io_uring: move timeout opcodes and handling into its own file

[linux-2.6-microblaze.git] / io_uring / io_uring.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Shared application/kernel submission and completion ring pairs, for
 * supporting fast/efficient IO.
 *
 * A note on the read/write ordering memory barriers that are matched between
 * the application and kernel side.
 *
 * After the application reads the CQ ring tail, it must use an
 * appropriate smp_rmb() to pair with the smp_wmb() the kernel uses
 * before writing the tail (using smp_load_acquire to read the tail will
 * do). It also needs a smp_mb() before updating CQ head (ordering the
 * entry load(s) with the head store), pairing with an implicit barrier
 * through a control-dependency in io_get_cqe (smp_store_release to
 * store head will do). Failure to do so could lead to reading invalid
 * CQ entries.
 *
 * Likewise, the application must use an appropriate smp_wmb() before
 * writing the SQ tail (ordering SQ entry stores with the tail store),
 * which pairs with smp_load_acquire in io_get_sqring (smp_store_release
 * to store the tail will do). And it needs a barrier ordering the SQ
 * head load before writing new SQ entries (smp_load_acquire to read
 * head will do).
 *
 * When using the SQ poll thread (IORING_SETUP_SQPOLL), the application
 * needs to check the SQ flags for IORING_SQ_NEED_WAKEUP *after*
 * updating the SQ tail; a full memory barrier smp_mb() is needed
 * between.
 *
 * Also see the examples in the liburing library:
 *
 *      git://git.kernel.dk/liburing
 *
 * io_uring also uses READ/WRITE_ONCE() for _any_ store or load that happens
 * from data shared between the kernel and application. This is done both
 * for ordering purposes, but also to ensure that once a value is loaded from
 * data that the application could potentially modify, it remains stable.
 *
 * Copyright (C) 2018-2019 Jens Axboe
 * Copyright (c) 2018-2019 Christoph Hellwig
 */
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/syscalls.h>
#include <linux/compat.h>
#include <net/compat.h>
#include <linux/refcount.h>
#include <linux/uio.h>
#include <linux/bits.h>

#include <linux/sched/signal.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/percpu.h>
#include <linux/slab.h>
#include <linux/blk-mq.h>
#include <linux/bvec.h>
#include <linux/net.h>
#include <net/sock.h>
#include <net/af_unix.h>
#include <net/scm.h>
#include <linux/anon_inodes.h>
#include <linux/sched/mm.h>
#include <linux/uaccess.h>
#include <linux/nospec.h>
#include <linux/sizes.h>
#include <linux/hugetlb.h>
#include <linux/highmem.h>
#include <linux/namei.h>
#include <linux/fsnotify.h>
#include <linux/fadvise.h>
#include <linux/eventpoll.h>
#include <linux/splice.h>
#include <linux/task_work.h>
#include <linux/pagemap.h>
#include <linux/io_uring.h>
#include <linux/audit.h>
#include <linux/security.h>

#define CREATE_TRACE_POINTS
#include <trace/events/io_uring.h>

#include <uapi/linux/io_uring.h>

#include "../fs/internal.h"
#include "io-wq.h"

#include "io_uring_types.h"
#include "io_uring.h"
#include "refs.h"

#include "xattr.h"
#include "nop.h"
#include "fs.h"
#include "splice.h"
#include "sync.h"
#include "advise.h"
#include "openclose.h"
#include "uring_cmd.h"
#include "epoll.h"
#include "statx.h"
#include "net.h"
#include "msg_ring.h"
#include "timeout.h"

#define IORING_MAX_ENTRIES      32768
#define IORING_MAX_CQ_ENTRIES   (2 * IORING_MAX_ENTRIES)
#define IORING_SQPOLL_CAP_ENTRIES_VALUE 8

/* only define max */
#define IORING_MAX_FIXED_FILES  (1U << 20)
#define IORING_MAX_RESTRICTIONS (IORING_RESTRICTION_LAST + \
                                 IORING_REGISTER_LAST + IORING_OP_LAST)

#define IO_RSRC_TAG_TABLE_SHIFT (PAGE_SHIFT - 3)
#define IO_RSRC_TAG_TABLE_MAX   (1U << IO_RSRC_TAG_TABLE_SHIFT)
#define IO_RSRC_TAG_TABLE_MASK  (IO_RSRC_TAG_TABLE_MAX - 1)

#define IORING_MAX_REG_BUFFERS  (1U << 14)

#define SQE_COMMON_FLAGS (IOSQE_FIXED_FILE | IOSQE_IO_LINK | \
                          IOSQE_IO_HARDLINK | IOSQE_ASYNC)

#define SQE_VALID_FLAGS (SQE_COMMON_FLAGS | IOSQE_BUFFER_SELECT | \
                        IOSQE_IO_DRAIN | IOSQE_CQE_SKIP_SUCCESS)

#define IO_REQ_CLEAN_FLAGS (REQ_F_BUFFER_SELECTED | REQ_F_NEED_CLEANUP | \
                                REQ_F_POLLED | REQ_F_INFLIGHT | REQ_F_CREDS | \
                                REQ_F_ASYNC_DATA)

#define IO_REQ_CLEAN_SLOW_FLAGS (REQ_F_REFCOUNT | REQ_F_LINK | REQ_F_HARDLINK |\
                                 IO_REQ_CLEAN_FLAGS)

#define IO_TCTX_REFS_CACHE_NR   (1U << 10)

struct io_mapped_ubuf {
        u64             ubuf;
        u64             ubuf_end;
        unsigned int    nr_bvecs;
        unsigned long   acct_pages;
        struct bio_vec  bvec[];
};

struct io_ring_ctx;

struct io_overflow_cqe {
        struct list_head list;
        struct io_uring_cqe cqe;
};

struct io_rsrc_put {
        struct list_head list;
        u64 tag;
        union {
                void *rsrc;
                struct file *file;
                struct io_mapped_ubuf *buf;
        };
};

struct io_rsrc_node {
        struct percpu_ref               refs;
        struct list_head                node;
        struct list_head                rsrc_list;
        struct io_rsrc_data             *rsrc_data;
        struct llist_node               llist;
        bool                            done;
};

typedef void (rsrc_put_fn)(struct io_ring_ctx *ctx, struct io_rsrc_put *prsrc);

struct io_rsrc_data {
        struct io_ring_ctx              *ctx;

        u64                             **tags;
        unsigned int                    nr;
        rsrc_put_fn                     *do_put;
        atomic_t                        refs;
        struct completion               done;
        bool                            quiesce;
};

#define IO_BUFFER_LIST_BUF_PER_PAGE (PAGE_SIZE / sizeof(struct io_uring_buf))
struct io_buffer_list {
        /*
         * If ->buf_nr_pages is set, then buf_pages/buf_ring are used. If not,
         * then these are classic provided buffers and ->buf_list is used.
         */
        union {
                struct list_head buf_list;
                struct {
                        struct page **buf_pages;
                        struct io_uring_buf_ring *buf_ring;
                };
        };
        __u16 bgid;

        /* below is for ring provided buffers */
        __u16 buf_nr_pages;
        __u16 nr_entries;
        __u16 head;
        __u16 mask;
};

struct io_buffer {
        struct list_head list;
        __u64 addr;
        __u32 len;
        __u16 bid;
        __u16 bgid;
};

enum {
        IO_SQ_THREAD_SHOULD_STOP = 0,
        IO_SQ_THREAD_SHOULD_PARK,
};

struct io_sq_data {
        refcount_t              refs;
        atomic_t                park_pending;
        struct mutex            lock;

        /* ctx's that are using this sqd */
        struct list_head        ctx_list;

        struct task_struct      *thread;
        struct wait_queue_head  wait;

        unsigned                sq_thread_idle;
        int                     sq_cpu;
        pid_t                   task_pid;
        pid_t                   task_tgid;

        unsigned long           state;
        struct completion       exited;
};

#define IO_COMPL_BATCH                  32
#define IO_REQ_CACHE_SIZE               32
#define IO_REQ_ALLOC_BATCH              8

#define BGID_ARRAY                      64

/*
 * Arbitrary limit, can be raised if need be
 */
#define IO_RINGFD_REG_MAX 16

struct io_uring_task {
        /* submission side */
        int                     cached_refs;
        struct xarray           xa;
        struct wait_queue_head  wait;
        const struct io_ring_ctx *last;
        struct io_wq            *io_wq;
        struct percpu_counter   inflight;
        atomic_t                inflight_tracked;
        atomic_t                in_idle;

        spinlock_t              task_lock;
        struct io_wq_work_list  task_list;
        struct io_wq_work_list  prio_task_list;
        struct callback_head    task_work;
        struct file             **registered_rings;
        bool                    task_running;
};

/*
 * First field must be the file pointer in all the
 * iocb unions! See also 'struct kiocb' in <linux/fs.h>
 */
struct io_poll {
        struct file                     *file;
        struct wait_queue_head          *head;
        __poll_t                        events;
        struct wait_queue_entry         wait;
};

struct io_poll_update {
        struct file                     *file;
        u64                             old_user_data;
        u64                             new_user_data;
        __poll_t                        events;
        bool                            update_events;
        bool                            update_user_data;
};

struct io_cancel {
        struct file                     *file;
        u64                             addr;
        u32                             flags;
        s32                             fd;
};

struct io_rw {
        /* NOTE: kiocb has the file as the first member, so don't do it here */
        struct kiocb                    kiocb;
        u64                             addr;
        u32                             len;
        rwf_t                           flags;
};

struct io_rsrc_update {
        struct file                     *file;
        u64                             arg;
        u32                             nr_args;
        u32                             offset;
};

struct io_provide_buf {
        struct file                     *file;
        __u64                           addr;
        __u32                           len;
        __u32                           bgid;
        __u16                           nbufs;
        __u16                           bid;
};

struct io_rw_state {
        struct iov_iter                 iter;
        struct iov_iter_state           iter_state;
        struct iovec                    fast_iov[UIO_FASTIOV];
};

struct io_async_rw {
        struct io_rw_state              s;
        const struct iovec              *free_iovec;
        size_t                          bytes_done;
        struct wait_page_queue          wpq;
};

struct async_poll {
        struct io_poll          poll;
        struct io_poll          *double_poll;
};

enum {
        IORING_RSRC_FILE                = 0,
        IORING_RSRC_BUFFER              = 1,
};

enum {
        IO_CHECK_CQ_OVERFLOW_BIT,
        IO_CHECK_CQ_DROPPED_BIT,
};

struct io_tctx_node {
        struct list_head        ctx_node;
        struct task_struct      *task;
        struct io_ring_ctx      *ctx;
};

struct io_defer_entry {
        struct list_head        list;
        struct io_kiocb         *req;
        u32                     seq;
};

struct io_op_def {
        /* needs req->file assigned */
        unsigned                needs_file : 1;
        /* should block plug */
        unsigned                plug : 1;
        /* hash wq insertion if file is a regular file */
        unsigned                hash_reg_file : 1;
        /* unbound wq insertion if file is a non-regular file */
        unsigned                unbound_nonreg_file : 1;
        /* set if opcode supports polled "wait" */
        unsigned                pollin : 1;
        unsigned                pollout : 1;
        unsigned                poll_exclusive : 1;
        /* op supports buffer selection */
        unsigned                buffer_select : 1;
        /* opcode is not supported by this kernel */
        unsigned                not_supported : 1;
        /* skip auditing */
        unsigned                audit_skip : 1;
        /* supports ioprio */
        unsigned                ioprio : 1;
        /* supports iopoll */
        unsigned                iopoll : 1;
        /* size of async data needed, if any */
        unsigned short          async_size;

        int (*prep)(struct io_kiocb *, const struct io_uring_sqe *);
        int (*issue)(struct io_kiocb *, unsigned int);
        int (*prep_async)(struct io_kiocb *);
        void (*cleanup)(struct io_kiocb *);
};

static const struct io_op_def io_op_defs[];

/* requests with any of those set should undergo io_disarm_next() */
#define IO_DISARM_MASK (REQ_F_ARM_LTIMEOUT | REQ_F_LINK_TIMEOUT | REQ_F_FAIL)
#define IO_REQ_LINK_FLAGS (REQ_F_LINK | REQ_F_HARDLINK)

static void io_uring_del_tctx_node(unsigned long index);
static void io_uring_try_cancel_requests(struct io_ring_ctx *ctx,
                                         struct task_struct *task,
                                         bool cancel_all);
static void io_uring_cancel_generic(bool cancel_all, struct io_sq_data *sqd);

static void io_dismantle_req(struct io_kiocb *req);
static int __io_register_rsrc_update(struct io_ring_ctx *ctx, unsigned type,
                                     struct io_uring_rsrc_update2 *up,
                                     unsigned nr_args);
static void io_clean_op(struct io_kiocb *req);
static void io_queue_sqe(struct io_kiocb *req);
static void io_rsrc_put_work(struct work_struct *work);

static void io_req_task_queue(struct io_kiocb *req);
static void __io_submit_flush_completions(struct io_ring_ctx *ctx);
static int io_req_prep_async(struct io_kiocb *req);

static void io_eventfd_signal(struct io_ring_ctx *ctx);

static struct kmem_cache *req_cachep;

static const struct file_operations io_uring_fops;

const char *io_uring_get_opcode(u8 opcode)
{
        switch ((enum io_uring_op)opcode) {
        case IORING_OP_NOP:
                return "NOP";
        case IORING_OP_READV:
                return "READV";
        case IORING_OP_WRITEV:
                return "WRITEV";
        case IORING_OP_FSYNC:
                return "FSYNC";
        case IORING_OP_READ_FIXED:
                return "READ_FIXED";
        case IORING_OP_WRITE_FIXED:
                return "WRITE_FIXED";
        case IORING_OP_POLL_ADD:
                return "POLL_ADD";
        case IORING_OP_POLL_REMOVE:
                return "POLL_REMOVE";
        case IORING_OP_SYNC_FILE_RANGE:
                return "SYNC_FILE_RANGE";
        case IORING_OP_SENDMSG:
                return "SENDMSG";
        case IORING_OP_RECVMSG:
                return "RECVMSG";
        case IORING_OP_TIMEOUT:
                return "TIMEOUT";
        case IORING_OP_TIMEOUT_REMOVE:
                return "TIMEOUT_REMOVE";
        case IORING_OP_ACCEPT:
                return "ACCEPT";
        case IORING_OP_ASYNC_CANCEL:
                return "ASYNC_CANCEL";
        case IORING_OP_LINK_TIMEOUT:
                return "LINK_TIMEOUT";
        case IORING_OP_CONNECT:
                return "CONNECT";
        case IORING_OP_FALLOCATE:
                return "FALLOCATE";
        case IORING_OP_OPENAT:
                return "OPENAT";
        case IORING_OP_CLOSE:
                return "CLOSE";
        case IORING_OP_FILES_UPDATE:
                return "FILES_UPDATE";
        case IORING_OP_STATX:
                return "STATX";
        case IORING_OP_READ:
                return "READ";
        case IORING_OP_WRITE:
                return "WRITE";
        case IORING_OP_FADVISE:
                return "FADVISE";
        case IORING_OP_MADVISE:
                return "MADVISE";
        case IORING_OP_SEND:
                return "SEND";
        case IORING_OP_RECV:
                return "RECV";
        case IORING_OP_OPENAT2:
                return "OPENAT2";
        case IORING_OP_EPOLL_CTL:
                return "EPOLL_CTL";
        case IORING_OP_SPLICE:
                return "SPLICE";
        case IORING_OP_PROVIDE_BUFFERS:
                return "PROVIDE_BUFFERS";
        case IORING_OP_REMOVE_BUFFERS:
                return "REMOVE_BUFFERS";
        case IORING_OP_TEE:
                return "TEE";
        case IORING_OP_SHUTDOWN:
                return "SHUTDOWN";
        case IORING_OP_RENAMEAT:
                return "RENAMEAT";
        case IORING_OP_UNLINKAT:
                return "UNLINKAT";
        case IORING_OP_MKDIRAT:
                return "MKDIRAT";
        case IORING_OP_SYMLINKAT:
                return "SYMLINKAT";
        case IORING_OP_LINKAT:
                return "LINKAT";
        case IORING_OP_MSG_RING:
                return "MSG_RING";
        case IORING_OP_FSETXATTR:
                return "FSETXATTR";
        case IORING_OP_SETXATTR:
                return "SETXATTR";
        case IORING_OP_FGETXATTR:
                return "FGETXATTR";
        case IORING_OP_GETXATTR:
                return "GETXATTR";
        case IORING_OP_SOCKET:
                return "SOCKET";
        case IORING_OP_URING_CMD:
                return "URING_CMD";
        case IORING_OP_LAST:
                return "INVALID";
        }
        return "INVALID";
}

bool io_is_uring_fops(struct file *file)
{
        return file->f_op == &io_uring_fops;
}

struct sock *io_uring_get_socket(struct file *file)
{
#if defined(CONFIG_UNIX)
        if (io_is_uring_fops(file)) {
                struct io_ring_ctx *ctx = file->private_data;

                return ctx->ring_sock->sk;
        }
#endif
        return NULL;
}
EXPORT_SYMBOL(io_uring_get_socket);

#if defined(CONFIG_UNIX)
static inline bool io_file_need_scm(struct file *filp)
{
#if defined(IO_URING_SCM_ALL)
        return true;
#else
        return !!unix_get_socket(filp);
#endif
}
#else
static inline bool io_file_need_scm(struct file *filp)
{
        return false;
}
#endif

static inline void io_tw_lock(struct io_ring_ctx *ctx, bool *locked)
{
        if (!*locked) {
                mutex_lock(&ctx->uring_lock);
                *locked = true;
        }
}

static inline void io_submit_flush_completions(struct io_ring_ctx *ctx)
{
        if (!wq_list_empty(&ctx->submit_state.compl_reqs))
                __io_submit_flush_completions(ctx);
}

#define IO_RSRC_REF_BATCH       100

static void io_rsrc_put_node(struct io_rsrc_node *node, int nr)
{
        percpu_ref_put_many(&node->refs, nr);
}

static inline void io_req_put_rsrc_locked(struct io_kiocb *req,
                                          struct io_ring_ctx *ctx)
        __must_hold(&ctx->uring_lock)
{
        struct io_rsrc_node *node = req->rsrc_node;

        if (node) {
                if (node == ctx->rsrc_node)
                        ctx->rsrc_cached_refs++;
                else
                        io_rsrc_put_node(node, 1);
        }
}

static inline void io_req_put_rsrc(struct io_kiocb *req)
{
        if (req->rsrc_node)
                io_rsrc_put_node(req->rsrc_node, 1);
}

static __cold void io_rsrc_refs_drop(struct io_ring_ctx *ctx)
        __must_hold(&ctx->uring_lock)
{
        if (ctx->rsrc_cached_refs) {
                io_rsrc_put_node(ctx->rsrc_node, ctx->rsrc_cached_refs);
                ctx->rsrc_cached_refs = 0;
        }
}

static void io_rsrc_refs_refill(struct io_ring_ctx *ctx)
        __must_hold(&ctx->uring_lock)
{
        ctx->rsrc_cached_refs += IO_RSRC_REF_BATCH;
        percpu_ref_get_many(&ctx->rsrc_node->refs, IO_RSRC_REF_BATCH);
}

static inline void io_req_set_rsrc_node(struct io_kiocb *req,
                                        struct io_ring_ctx *ctx,
                                        unsigned int issue_flags)
{
        if (!req->rsrc_node) {
                req->rsrc_node = ctx->rsrc_node;

                if (!(issue_flags & IO_URING_F_UNLOCKED)) {
                        lockdep_assert_held(&ctx->uring_lock);
                        ctx->rsrc_cached_refs--;
                        if (unlikely(ctx->rsrc_cached_refs < 0))
                                io_rsrc_refs_refill(ctx);
                } else {
                        percpu_ref_get(&req->rsrc_node->refs);
                }
        }
}

static unsigned int __io_put_kbuf(struct io_kiocb *req, struct list_head *list)
{
        if (req->flags & REQ_F_BUFFER_RING) {
                if (req->buf_list)
                        req->buf_list->head++;
                req->flags &= ~REQ_F_BUFFER_RING;
        } else {
                list_add(&req->kbuf->list, list);
                req->flags &= ~REQ_F_BUFFER_SELECTED;
        }

        return IORING_CQE_F_BUFFER | (req->buf_index << IORING_CQE_BUFFER_SHIFT);
}

static inline unsigned int io_put_kbuf_comp(struct io_kiocb *req)
{
        lockdep_assert_held(&req->ctx->completion_lock);

        if (!(req->flags & (REQ_F_BUFFER_SELECTED|REQ_F_BUFFER_RING)))
                return 0;
        return __io_put_kbuf(req, &req->ctx->io_buffers_comp);
}

inline unsigned int io_put_kbuf(struct io_kiocb *req, unsigned issue_flags)
{
        unsigned int cflags;

        if (!(req->flags & (REQ_F_BUFFER_SELECTED|REQ_F_BUFFER_RING)))
                return 0;

        /*
         * We can add this buffer back to two lists:
         *
         * 1) The io_buffers_cache list. This one is protected by the
         *    ctx->uring_lock. If we already hold this lock, add back to this
         *    list as we can grab it from issue as well.
         * 2) The io_buffers_comp list. This one is protected by the
         *    ctx->completion_lock.
         *
         * We migrate buffers from the comp_list to the issue cache list
         * when we need one.
         */
        if (req->flags & REQ_F_BUFFER_RING) {
                /* no buffers to recycle for this case */
                cflags = __io_put_kbuf(req, NULL);
        } else if (issue_flags & IO_URING_F_UNLOCKED) {
                struct io_ring_ctx *ctx = req->ctx;

                spin_lock(&ctx->completion_lock);
                cflags = __io_put_kbuf(req, &ctx->io_buffers_comp);
                spin_unlock(&ctx->completion_lock);
        } else {
                lockdep_assert_held(&req->ctx->uring_lock);

                cflags = __io_put_kbuf(req, &req->ctx->io_buffers_cache);
        }

        return cflags;
}

static struct io_buffer_list *io_buffer_get_list(struct io_ring_ctx *ctx,
                                                 unsigned int bgid)
{
        if (ctx->io_bl && bgid < BGID_ARRAY)
                return &ctx->io_bl[bgid];

        return xa_load(&ctx->io_bl_xa, bgid);
}

static void io_kbuf_recycle(struct io_kiocb *req, unsigned issue_flags)
{
        struct io_ring_ctx *ctx = req->ctx;
        struct io_buffer_list *bl;
        struct io_buffer *buf;

        if (!(req->flags & (REQ_F_BUFFER_SELECTED|REQ_F_BUFFER_RING)))
                return;
        /*
         * For legacy provided buffer mode, don't recycle if we already did
         * IO to this buffer. For ring-mapped provided buffer mode, we should
         * increment ring->head to explicitly monopolize the buffer to avoid
         * multiple use.
         */
        if ((req->flags & REQ_F_BUFFER_SELECTED) &&
            (req->flags & REQ_F_PARTIAL_IO))
                return;

        /*
         * READV uses fields in `struct io_rw` (len/addr) to stash the selected
         * buffer data. However if that buffer is recycled the original request
         * data stored in addr is lost. Therefore forbid recycling for now.
         */
        if (req->opcode == IORING_OP_READV)
                return;

        /*
         * We don't need to recycle for REQ_F_BUFFER_RING, we can just clear
         * the flag and hence ensure that bl->head doesn't get incremented.
         * If the tail has already been incremented, hang on to it.
         */
        if (req->flags & REQ_F_BUFFER_RING) {
                if (req->buf_list) {
                        if (req->flags & REQ_F_PARTIAL_IO) {
                                req->buf_list->head++;
                                req->buf_list = NULL;
                        } else {
                                req->buf_index = req->buf_list->bgid;
                                req->flags &= ~REQ_F_BUFFER_RING;
                        }
                }
                return;
        }

        io_ring_submit_lock(ctx, issue_flags);

        buf = req->kbuf;
        bl = io_buffer_get_list(ctx, buf->bgid);
        list_add(&buf->list, &bl->buf_list);
        req->flags &= ~REQ_F_BUFFER_SELECTED;
        req->buf_index = buf->bgid;

        io_ring_submit_unlock(ctx, issue_flags);
}

static bool io_match_linked(struct io_kiocb *head)
{
        struct io_kiocb *req;

        io_for_each_link(req, head) {
                if (req->flags & REQ_F_INFLIGHT)
                        return true;
        }
        return false;
}

/*
 * As io_match_task() but protected against racing with linked timeouts.
 * User must not hold timeout_lock.
 */
static bool io_match_task_safe(struct io_kiocb *head, struct task_struct *task,
                               bool cancel_all)
{
        bool matched;

        if (task && head->task != task)
                return false;
        if (cancel_all)
                return true;

        if (head->flags & REQ_F_LINK_TIMEOUT) {
                struct io_ring_ctx *ctx = head->ctx;

                /* protect against races with linked timeouts */
                spin_lock_irq(&ctx->timeout_lock);
                matched = io_match_linked(head);
                spin_unlock_irq(&ctx->timeout_lock);
        } else {
                matched = io_match_linked(head);
        }
        return matched;
}

static inline void req_fail_link_node(struct io_kiocb *req, int res)
{
        req_set_fail(req);
        io_req_set_res(req, res, 0);
}

static inline void io_req_add_to_cache(struct io_kiocb *req, struct io_ring_ctx *ctx)
{
        wq_stack_add_head(&req->comp_list, &ctx->submit_state.free_list);
}

static __cold void io_ring_ctx_ref_free(struct percpu_ref *ref)
{
        struct io_ring_ctx *ctx = container_of(ref, struct io_ring_ctx, refs);

        complete(&ctx->ref_comp);
}

static __cold void io_fallback_req_func(struct work_struct *work)
{
        struct io_ring_ctx *ctx = container_of(work, struct io_ring_ctx,
                                                fallback_work.work);
        struct llist_node *node = llist_del_all(&ctx->fallback_llist);
        struct io_kiocb *req, *tmp;
        bool locked = false;

        percpu_ref_get(&ctx->refs);
        llist_for_each_entry_safe(req, tmp, node, io_task_work.fallback_node)
                req->io_task_work.func(req, &locked);

        if (locked) {
                io_submit_flush_completions(ctx);
                mutex_unlock(&ctx->uring_lock);
        }
        percpu_ref_put(&ctx->refs);
}

static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
{
        struct io_ring_ctx *ctx;
        int hash_bits;

        ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
        if (!ctx)
                return NULL;

        xa_init(&ctx->io_bl_xa);

        /*
         * Use 5 bits less than the max cq entries, that should give us around
         * 32 entries per hash list if totally full and uniformly spread.
         */
        hash_bits = ilog2(p->cq_entries);
        hash_bits -= 5;
        if (hash_bits <= 0)
                hash_bits = 1;
        ctx->cancel_hash_bits = hash_bits;
        ctx->cancel_hash = kmalloc((1U << hash_bits) * sizeof(struct hlist_head),
                                        GFP_KERNEL);
        if (!ctx->cancel_hash)
                goto err;
        __hash_init(ctx->cancel_hash, 1U << hash_bits);

        ctx->dummy_ubuf = kzalloc(sizeof(*ctx->dummy_ubuf), GFP_KERNEL);
        if (!ctx->dummy_ubuf)
                goto err;
        /* set invalid range, so io_import_fixed() fails meeting it */
        ctx->dummy_ubuf->ubuf = -1UL;

        if (percpu_ref_init(&ctx->refs, io_ring_ctx_ref_free,
                            PERCPU_REF_ALLOW_REINIT, GFP_KERNEL))
                goto err;

        ctx->flags = p->flags;
        init_waitqueue_head(&ctx->sqo_sq_wait);
        INIT_LIST_HEAD(&ctx->sqd_list);
        INIT_LIST_HEAD(&ctx->cq_overflow_list);
        INIT_LIST_HEAD(&ctx->io_buffers_cache);
        INIT_LIST_HEAD(&ctx->apoll_cache);
        init_completion(&ctx->ref_comp);
        xa_init_flags(&ctx->personalities, XA_FLAGS_ALLOC1);
        mutex_init(&ctx->uring_lock);
        init_waitqueue_head(&ctx->cq_wait);
        spin_lock_init(&ctx->completion_lock);
        spin_lock_init(&ctx->timeout_lock);
        INIT_WQ_LIST(&ctx->iopoll_list);
        INIT_LIST_HEAD(&ctx->io_buffers_pages);
        INIT_LIST_HEAD(&ctx->io_buffers_comp);
        INIT_LIST_HEAD(&ctx->defer_list);
        INIT_LIST_HEAD(&ctx->timeout_list);
        INIT_LIST_HEAD(&ctx->ltimeout_list);
        spin_lock_init(&ctx->rsrc_ref_lock);
        INIT_LIST_HEAD(&ctx->rsrc_ref_list);
        INIT_DELAYED_WORK(&ctx->rsrc_put_work, io_rsrc_put_work);
        init_llist_head(&ctx->rsrc_put_llist);
        INIT_LIST_HEAD(&ctx->tctx_list);
        ctx->submit_state.free_list.next = NULL;
        INIT_WQ_LIST(&ctx->locked_free_list);
        INIT_DELAYED_WORK(&ctx->fallback_work, io_fallback_req_func);
        INIT_WQ_LIST(&ctx->submit_state.compl_reqs);
        return ctx;
err:
        kfree(ctx->dummy_ubuf);
        kfree(ctx->cancel_hash);
        kfree(ctx->io_bl);
        xa_destroy(&ctx->io_bl_xa);
        kfree(ctx);
        return NULL;
}

static void io_account_cq_overflow(struct io_ring_ctx *ctx)
{
        struct io_rings *r = ctx->rings;

        WRITE_ONCE(r->cq_overflow, READ_ONCE(r->cq_overflow) + 1);
        ctx->cq_extra--;
}

static bool req_need_defer(struct io_kiocb *req, u32 seq)
{
        if (unlikely(req->flags & REQ_F_IO_DRAIN)) {
                struct io_ring_ctx *ctx = req->ctx;

                return seq + READ_ONCE(ctx->cq_extra) != ctx->cached_cq_tail;
        }

        return false;
}

static inline bool io_req_ffs_set(struct io_kiocb *req)
{
        return req->flags & REQ_F_FIXED_FILE;
}

static inline void io_req_track_inflight(struct io_kiocb *req)
{
        if (!(req->flags & REQ_F_INFLIGHT)) {
                req->flags |= REQ_F_INFLIGHT;
                atomic_inc(&req->task->io_uring->inflight_tracked);
        }
}

static struct io_kiocb *__io_prep_linked_timeout(struct io_kiocb *req)
{
        if (WARN_ON_ONCE(!req->link))
                return NULL;

        req->flags &= ~REQ_F_ARM_LTIMEOUT;
        req->flags |= REQ_F_LINK_TIMEOUT;

        /* linked timeouts should have two refs once prep'ed */
        io_req_set_refcount(req);
        __io_req_set_refcount(req->link, 2);
        return req->link;
}

static inline struct io_kiocb *io_prep_linked_timeout(struct io_kiocb *req)
{
        if (likely(!(req->flags & REQ_F_ARM_LTIMEOUT)))
                return NULL;
        return __io_prep_linked_timeout(req);
}

static noinline void __io_arm_ltimeout(struct io_kiocb *req)
{
        io_queue_linked_timeout(__io_prep_linked_timeout(req));
}

static inline void io_arm_ltimeout(struct io_kiocb *req)
{
        if (unlikely(req->flags & REQ_F_ARM_LTIMEOUT))
                __io_arm_ltimeout(req);
}

static void io_prep_async_work(struct io_kiocb *req)
{
        const struct io_op_def *def = &io_op_defs[req->opcode];
        struct io_ring_ctx *ctx = req->ctx;

        if (!(req->flags & REQ_F_CREDS)) {
                req->flags |= REQ_F_CREDS;
                req->creds = get_current_cred();
        }

        req->work.list.next = NULL;
        req->work.flags = 0;
        req->work.cancel_seq = atomic_read(&ctx->cancel_seq);
        if (req->flags & REQ_F_FORCE_ASYNC)
                req->work.flags |= IO_WQ_WORK_CONCURRENT;

        if (req->flags & REQ_F_ISREG) {
                if (def->hash_reg_file || (ctx->flags & IORING_SETUP_IOPOLL))
                        io_wq_hash_work(&req->work, file_inode(req->file));
        } else if (!req->file || !S_ISBLK(file_inode(req->file)->i_mode)) {
                if (def->unbound_nonreg_file)
                        req->work.flags |= IO_WQ_WORK_UNBOUND;
        }
}

static void io_prep_async_link(struct io_kiocb *req)
{
        struct io_kiocb *cur;

        if (req->flags & REQ_F_LINK_TIMEOUT) {
                struct io_ring_ctx *ctx = req->ctx;

                spin_lock_irq(&ctx->timeout_lock);
                io_for_each_link(cur, req)
                        io_prep_async_work(cur);
                spin_unlock_irq(&ctx->timeout_lock);
        } else {
                io_for_each_link(cur, req)
                        io_prep_async_work(cur);
        }
}

static inline void io_req_add_compl_list(struct io_kiocb *req)
{
        struct io_submit_state *state = &req->ctx->submit_state;

        if (!(req->flags & REQ_F_CQE_SKIP))
                state->flush_cqes = true;
        wq_list_add_tail(&req->comp_list, &state->compl_reqs);
}

static void io_queue_iowq(struct io_kiocb *req, bool *dont_use)
{
        struct io_kiocb *link = io_prep_linked_timeout(req);
        struct io_uring_task *tctx = req->task->io_uring;

        BUG_ON(!tctx);
        BUG_ON(!tctx->io_wq);

        /* init ->work of the whole link before punting */
        io_prep_async_link(req);

        /*
         * Not expected to happen, but if we do have a bug where this _can_
         * happen, catch it here and ensure the request is marked as
         * canceled. That will make io-wq go through the usual work cancel
         * procedure rather than attempt to run this request (or create a new
         * worker for it).
         */
        if (WARN_ON_ONCE(!same_thread_group(req->task, current)))
                req->work.flags |= IO_WQ_WORK_CANCEL;

        trace_io_uring_queue_async_work(req->ctx, req, req->cqe.user_data,
                                        req->opcode, req->flags, &req->work,
                                        io_wq_is_hashed(&req->work));
        io_wq_enqueue(tctx->io_wq, &req->work);
        if (link)
                io_queue_linked_timeout(link);
}

static __cold void io_queue_deferred(struct io_ring_ctx *ctx)
{
        while (!list_empty(&ctx->defer_list)) {
                struct io_defer_entry *de = list_first_entry(&ctx->defer_list,
                                                struct io_defer_entry, list);

                if (req_need_defer(de->req, de->seq))
                        break;
                list_del_init(&de->list);
                io_req_task_queue(de->req);
                kfree(de);
        }
}

static void __io_commit_cqring_flush(struct io_ring_ctx *ctx)
{
        if (ctx->off_timeout_used || ctx->drain_active) {
                spin_lock(&ctx->completion_lock);
                if (ctx->off_timeout_used)
                        io_flush_timeouts(ctx);
                if (ctx->drain_active)
                        io_queue_deferred(ctx);
                io_commit_cqring(ctx);
                spin_unlock(&ctx->completion_lock);
        }
        if (ctx->has_evfd)
                io_eventfd_signal(ctx);
}

static inline bool io_sqring_full(struct io_ring_ctx *ctx)
{
        struct io_rings *r = ctx->rings;

        return READ_ONCE(r->sq.tail) - ctx->cached_sq_head == ctx->sq_entries;
}

static inline unsigned int __io_cqring_events(struct io_ring_ctx *ctx)
{
        return ctx->cached_cq_tail - READ_ONCE(ctx->rings->cq.head);
}

/*
 * writes to the cq entry need to come after reading head; the
 * control dependency is enough as we're using WRITE_ONCE to
 * fill the cq entry
 */
static noinline struct io_uring_cqe *__io_get_cqe(struct io_ring_ctx *ctx)
{
        struct io_rings *rings = ctx->rings;
        unsigned int off = ctx->cached_cq_tail & (ctx->cq_entries - 1);
        unsigned int shift = 0;
        unsigned int free, queued, len;

        if (ctx->flags & IORING_SETUP_CQE32)
                shift = 1;

        /* userspace may cheat modifying the tail, be safe and do min */
        queued = min(__io_cqring_events(ctx), ctx->cq_entries);
        free = ctx->cq_entries - queued;
        /* we need a contiguous range, limit based on the current array offset */
        len = min(free, ctx->cq_entries - off);
        if (!len)
                return NULL;

        ctx->cached_cq_tail++;
        ctx->cqe_cached = &rings->cqes[off];
        ctx->cqe_sentinel = ctx->cqe_cached + len;
        ctx->cqe_cached++;
        return &rings->cqes[off << shift];
}

static inline struct io_uring_cqe *io_get_cqe(struct io_ring_ctx *ctx)
{
        if (likely(ctx->cqe_cached < ctx->cqe_sentinel)) {
                struct io_uring_cqe *cqe = ctx->cqe_cached;

                if (ctx->flags & IORING_SETUP_CQE32) {
                        unsigned int off = ctx->cqe_cached - ctx->rings->cqes;

                        cqe += off;
                }

                ctx->cached_cq_tail++;
                ctx->cqe_cached++;
                return cqe;
        }

        return __io_get_cqe(ctx);
}

static void io_eventfd_signal(struct io_ring_ctx *ctx)
{
        struct io_ev_fd *ev_fd;

        rcu_read_lock();
        /*
         * rcu_dereference ctx->io_ev_fd once and use it for both for checking
         * and eventfd_signal
         */
        ev_fd = rcu_dereference(ctx->io_ev_fd);

        /*
         * Check again if ev_fd exists incase an io_eventfd_unregister call
         * completed between the NULL check of ctx->io_ev_fd at the start of
         * the function and rcu_read_lock.
         */
        if (unlikely(!ev_fd))
                goto out;
        if (READ_ONCE(ctx->rings->cq_flags) & IORING_CQ_EVENTFD_DISABLED)
                goto out;

        if (!ev_fd->eventfd_async || io_wq_current_is_worker())
                eventfd_signal(ev_fd->cq_ev_fd, 1);
out:
        rcu_read_unlock();
}

static inline void io_cqring_wake(struct io_ring_ctx *ctx)
{
        /*
         * wake_up_all() may seem excessive, but io_wake_function() and
         * io_should_wake() handle the termination of the loop and only
         * wake as many waiters as we need to.
         */
        if (wq_has_sleeper(&ctx->cq_wait))
                wake_up_all(&ctx->cq_wait);
}

/*
 * This should only get called when at least one event has been posted.
 * Some applications rely on the eventfd notification count only changing
 * IFF a new CQE has been added to the CQ ring. There's no depedency on
 * 1:1 relationship between how many times this function is called (and
 * hence the eventfd count) and number of CQEs posted to the CQ ring.
 */
void io_cqring_ev_posted(struct io_ring_ctx *ctx)
{
        if (unlikely(ctx->off_timeout_used || ctx->drain_active ||
                     ctx->has_evfd))
                __io_commit_cqring_flush(ctx);

        io_cqring_wake(ctx);
}

static void io_cqring_ev_posted_iopoll(struct io_ring_ctx *ctx)
{
        if (unlikely(ctx->off_timeout_used || ctx->drain_active ||
                     ctx->has_evfd))
                __io_commit_cqring_flush(ctx);

        if (ctx->flags & IORING_SETUP_SQPOLL)
                io_cqring_wake(ctx);
}

/* Returns true if there are no backlogged entries after the flush */
static bool __io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force)
{
        bool all_flushed, posted;
        size_t cqe_size = sizeof(struct io_uring_cqe);

        if (!force && __io_cqring_events(ctx) == ctx->cq_entries)
                return false;

        if (ctx->flags & IORING_SETUP_CQE32)
                cqe_size <<= 1;

        posted = false;
        spin_lock(&ctx->completion_lock);
        while (!list_empty(&ctx->cq_overflow_list)) {
                struct io_uring_cqe *cqe = io_get_cqe(ctx);
                struct io_overflow_cqe *ocqe;

                if (!cqe && !force)
                        break;
                ocqe = list_first_entry(&ctx->cq_overflow_list,
                                        struct io_overflow_cqe, list);
                if (cqe)
                        memcpy(cqe, &ocqe->cqe, cqe_size);
                else
                        io_account_cq_overflow(ctx);

                posted = true;
                list_del(&ocqe->list);
                kfree(ocqe);
        }

        all_flushed = list_empty(&ctx->cq_overflow_list);
        if (all_flushed) {
                clear_bit(IO_CHECK_CQ_OVERFLOW_BIT, &ctx->check_cq);
                atomic_andnot(IORING_SQ_CQ_OVERFLOW, &ctx->rings->sq_flags);
        }

        io_commit_cqring(ctx);
        spin_unlock(&ctx->completion_lock);
        if (posted)
                io_cqring_ev_posted(ctx);
        return all_flushed;
}

static bool io_cqring_overflow_flush(struct io_ring_ctx *ctx)
{
        bool ret = true;

        if (test_bit(IO_CHECK_CQ_OVERFLOW_BIT, &ctx->check_cq)) {
                /* iopoll syncs against uring_lock, not completion_lock */
                if (ctx->flags & IORING_SETUP_IOPOLL)
                        mutex_lock(&ctx->uring_lock);
                ret = __io_cqring_overflow_flush(ctx, false);
                if (ctx->flags & IORING_SETUP_IOPOLL)
                        mutex_unlock(&ctx->uring_lock);
        }

        return ret;
}

static void __io_put_task(struct task_struct *task, int nr)
{
        struct io_uring_task *tctx = task->io_uring;

        percpu_counter_sub(&tctx->inflight, nr);
        if (unlikely(atomic_read(&tctx->in_idle)))
                wake_up(&tctx->wait);
        put_task_struct_many(task, nr);
}

/* must to be called somewhat shortly after putting a request */
static inline void io_put_task(struct task_struct *task, int nr)
{
        if (likely(task == current))
                task->io_uring->cached_refs += nr;
        else
                __io_put_task(task, nr);
}

static void io_task_refs_refill(struct io_uring_task *tctx)
{
        unsigned int refill = -tctx->cached_refs + IO_TCTX_REFS_CACHE_NR;

        percpu_counter_add(&tctx->inflight, refill);
        refcount_add(refill, &current->usage);
        tctx->cached_refs += refill;
}

static inline void io_get_task_refs(int nr)
{
        struct io_uring_task *tctx = current->io_uring;

        tctx->cached_refs -= nr;
        if (unlikely(tctx->cached_refs < 0))
                io_task_refs_refill(tctx);
}

static __cold void io_uring_drop_tctx_refs(struct task_struct *task)
{
        struct io_uring_task *tctx = task->io_uring;
        unsigned int refs = tctx->cached_refs;

        if (refs) {
                tctx->cached_refs = 0;
                percpu_counter_sub(&tctx->inflight, refs);
                put_task_struct_many(task, refs);
        }
}

static bool io_cqring_event_overflow(struct io_ring_ctx *ctx, u64 user_data,
                                     s32 res, u32 cflags, u64 extra1,
                                     u64 extra2)
{
        struct io_overflow_cqe *ocqe;
        size_t ocq_size = sizeof(struct io_overflow_cqe);
        bool is_cqe32 = (ctx->flags & IORING_SETUP_CQE32);

        if (is_cqe32)
                ocq_size += sizeof(struct io_uring_cqe);

        ocqe = kmalloc(ocq_size, GFP_ATOMIC | __GFP_ACCOUNT);
        trace_io_uring_cqe_overflow(ctx, user_data, res, cflags, ocqe);
        if (!ocqe) {
                /*
                 * If we're in ring overflow flush mode, or in task cancel mode,
                 * or cannot allocate an overflow entry, then we need to drop it
                 * on the floor.
                 */
                io_account_cq_overflow(ctx);
                set_bit(IO_CHECK_CQ_DROPPED_BIT, &ctx->check_cq);
                return false;
        }
        if (list_empty(&ctx->cq_overflow_list)) {
                set_bit(IO_CHECK_CQ_OVERFLOW_BIT, &ctx->check_cq);
                atomic_or(IORING_SQ_CQ_OVERFLOW, &ctx->rings->sq_flags);

        }
        ocqe->cqe.user_data = user_data;
        ocqe->cqe.res = res;
        ocqe->cqe.flags = cflags;
        if (is_cqe32) {
                ocqe->cqe.big_cqe[0] = extra1;
                ocqe->cqe.big_cqe[1] = extra2;
        }
        list_add_tail(&ocqe->list, &ctx->cq_overflow_list);
        return true;
}

static inline bool __io_fill_cqe_req(struct io_ring_ctx *ctx,
                                     struct io_kiocb *req)
{
        struct io_uring_cqe *cqe;

        if (!(ctx->flags & IORING_SETUP_CQE32)) {
                trace_io_uring_complete(req->ctx, req, req->cqe.user_data,
                                        req->cqe.res, req->cqe.flags, 0, 0);

                /*
                 * If we can't get a cq entry, userspace overflowed the
                 * submission (by quite a lot). Increment the overflow count in
                 * the ring.
                 */
                cqe = io_get_cqe(ctx);
                if (likely(cqe)) {
                        memcpy(cqe, &req->cqe, sizeof(*cqe));
                        return true;
                }

                return io_cqring_event_overflow(ctx, req->cqe.user_data,
                                                req->cqe.res, req->cqe.flags,
                                                0, 0);
        } else {
                u64 extra1 = 0, extra2 = 0;

                if (req->flags & REQ_F_CQE32_INIT) {
                        extra1 = req->extra1;
                        extra2 = req->extra2;
                }

                trace_io_uring_complete(req->ctx, req, req->cqe.user_data,
                                        req->cqe.res, req->cqe.flags, extra1, extra2);

                /*
                 * If we can't get a cq entry, userspace overflowed the
                 * submission (by quite a lot). Increment the overflow count in
                 * the ring.
                 */
                cqe = io_get_cqe(ctx);
                if (likely(cqe)) {
                        memcpy(cqe, &req->cqe, sizeof(struct io_uring_cqe));
                        WRITE_ONCE(cqe->big_cqe[0], extra1);
                        WRITE_ONCE(cqe->big_cqe[1], extra2);
                        return true;
                }

                return io_cqring_event_overflow(ctx, req->cqe.user_data,
                                req->cqe.res, req->cqe.flags,
                                extra1, extra2);
        }
}

bool io_fill_cqe_aux(struct io_ring_ctx *ctx, u64 user_data, s32 res,
                     u32 cflags)
{
        struct io_uring_cqe *cqe;

        ctx->cq_extra++;
        trace_io_uring_complete(ctx, NULL, user_data, res, cflags, 0, 0);

        /*
         * If we can't get a cq entry, userspace overflowed the
         * submission (by quite a lot). Increment the overflow count in
         * the ring.
         */
        cqe = io_get_cqe(ctx);
        if (likely(cqe)) {
                WRITE_ONCE(cqe->user_data, user_data);
                WRITE_ONCE(cqe->res, res);
                WRITE_ONCE(cqe->flags, cflags);

                if (ctx->flags & IORING_SETUP_CQE32) {
                        WRITE_ONCE(cqe->big_cqe[0], 0);
                        WRITE_ONCE(cqe->big_cqe[1], 0);
                }
                return true;
        }
        return io_cqring_event_overflow(ctx, user_data, res, cflags, 0, 0);
}

static void __io_req_complete_put(struct io_kiocb *req)
{
        /*
         * If we're the last reference to this request, add to our locked
         * free_list cache.
         */
        if (req_ref_put_and_test(req)) {
                struct io_ring_ctx *ctx = req->ctx;

                if (req->flags & IO_REQ_LINK_FLAGS) {
                        if (req->flags & IO_DISARM_MASK)
                                io_disarm_next(req);
                        if (req->link) {
                                io_req_task_queue(req->link);
                                req->link = NULL;
                        }
                }
                io_req_put_rsrc(req);
                /*
                 * Selected buffer deallocation in io_clean_op() assumes that
                 * we don't hold ->completion_lock. Clean them here to avoid
                 * deadlocks.
                 */
                io_put_kbuf_comp(req);
                io_dismantle_req(req);
                io_put_task(req->task, 1);
                wq_list_add_head(&req->comp_list, &ctx->locked_free_list);
                ctx->locked_free_nr++;
        }
}

void __io_req_complete_post(struct io_kiocb *req)
{
        if (!(req->flags & REQ_F_CQE_SKIP))
                __io_fill_cqe_req(req->ctx, req);
        __io_req_complete_put(req);
}

void io_req_complete_post(struct io_kiocb *req)
{
        struct io_ring_ctx *ctx = req->ctx;

        spin_lock(&ctx->completion_lock);
        __io_req_complete_post(req);
        io_commit_cqring(ctx);
        spin_unlock(&ctx->completion_lock);
        io_cqring_ev_posted(ctx);
}

inline void __io_req_complete(struct io_kiocb *req, unsigned issue_flags)
{
        if (issue_flags & IO_URING_F_COMPLETE_DEFER)
                req->flags |= REQ_F_COMPLETE_INLINE;
        else
                io_req_complete_post(req);
}

static void io_req_complete_failed(struct io_kiocb *req, s32 res)
{
        req_set_fail(req);
        io_req_set_res(req, res, io_put_kbuf(req, IO_URING_F_UNLOCKED));
        io_req_complete_post(req);
}

/*
 * Don't initialise the fields below on every allocation, but do that in
 * advance and keep them valid across allocations.
 */
static void io_preinit_req(struct io_kiocb *req, struct io_ring_ctx *ctx)
{
        req->ctx = ctx;
        req->link = NULL;
        req->async_data = NULL;
        /* not necessary, but safer to zero */
        req->cqe.res = 0;
}

static void io_flush_cached_locked_reqs(struct io_ring_ctx *ctx,
                                        struct io_submit_state *state)
{
        spin_lock(&ctx->completion_lock);
        wq_list_splice(&ctx->locked_free_list, &state->free_list);
        ctx->locked_free_nr = 0;
        spin_unlock(&ctx->completion_lock);
}

static inline bool io_req_cache_empty(struct io_ring_ctx *ctx)
{
        return !ctx->submit_state.free_list.next;
}

/*
 * A request might get retired back into the request caches even before opcode
 * handlers and io_issue_sqe() are done with it, e.g. inline completion path.
 * Because of that, io_alloc_req() should be called only under ->uring_lock
 * and with extra caution to not get a request that is still worked on.
 */
static __cold bool __io_alloc_req_refill(struct io_ring_ctx *ctx)
        __must_hold(&ctx->uring_lock)
{
        gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
        void *reqs[IO_REQ_ALLOC_BATCH];
        int ret, i;

        /*
         * If we have more than a batch's worth of requests in our IRQ side
         * locked cache, grab the lock and move them over to our submission
         * side cache.
         */
        if (data_race(ctx->locked_free_nr) > IO_COMPL_BATCH) {
                io_flush_cached_locked_reqs(ctx, &ctx->submit_state);
                if (!io_req_cache_empty(ctx))
                        return true;
        }

        ret = kmem_cache_alloc_bulk(req_cachep, gfp, ARRAY_SIZE(reqs), reqs);

        /*
         * Bulk alloc is all-or-nothing. If we fail to get a batch,
         * retry single alloc to be on the safe side.
         */
        if (unlikely(ret <= 0)) {
                reqs[0] = kmem_cache_alloc(req_cachep, gfp);
                if (!reqs[0])
                        return false;
                ret = 1;
        }

        percpu_ref_get_many(&ctx->refs, ret);
        for (i = 0; i < ret; i++) {
                struct io_kiocb *req = reqs[i];

                io_preinit_req(req, ctx);
                io_req_add_to_cache(req, ctx);
        }
        return true;
}

static inline bool io_alloc_req_refill(struct io_ring_ctx *ctx)
{
        if (unlikely(io_req_cache_empty(ctx)))
                return __io_alloc_req_refill(ctx);
        return true;
}

static inline struct io_kiocb *io_alloc_req(struct io_ring_ctx *ctx)
{
        struct io_wq_work_node *node;

        node = wq_stack_extract(&ctx->submit_state.free_list);
        return container_of(node, struct io_kiocb, comp_list);
}

static inline void io_dismantle_req(struct io_kiocb *req)
{
        unsigned int flags = req->flags;

        if (unlikely(flags & IO_REQ_CLEAN_FLAGS))
                io_clean_op(req);
        if (!(flags & REQ_F_FIXED_FILE))
                io_put_file(req->file);
}

__cold void io_free_req(struct io_kiocb *req)
{
        struct io_ring_ctx *ctx = req->ctx;

        io_req_put_rsrc(req);
        io_dismantle_req(req);
        io_put_task(req->task, 1);

        spin_lock(&ctx->completion_lock);
        wq_list_add_head(&req->comp_list, &ctx->locked_free_list);
        ctx->locked_free_nr++;
        spin_unlock(&ctx->completion_lock);
}

static void __io_req_find_next_prep(struct io_kiocb *req)
{
        struct io_ring_ctx *ctx = req->ctx;
        bool posted;

        spin_lock(&ctx->completion_lock);
        posted = io_disarm_next(req);
        io_commit_cqring(ctx);
        spin_unlock(&ctx->completion_lock);
        if (posted)
                io_cqring_ev_posted(ctx);
}

static inline struct io_kiocb *io_req_find_next(struct io_kiocb *req)
{
        struct io_kiocb *nxt;

        /*
         * If LINK is set, we have dependent requests in this chain. If we
         * didn't fail this request, queue the first one up, moving any other
         * dependencies to the next request. In case of failure, fail the rest
         * of the chain.
         */
        if (unlikely(req->flags & IO_DISARM_MASK))
                __io_req_find_next_prep(req);
        nxt = req->link;
        req->link = NULL;
        return nxt;
}

static void ctx_flush_and_put(struct io_ring_ctx *ctx, bool *locked)
{
        if (!ctx)
                return;
        if (ctx->flags & IORING_SETUP_TASKRUN_FLAG)
                atomic_andnot(IORING_SQ_TASKRUN, &ctx->rings->sq_flags);
        if (*locked) {
                io_submit_flush_completions(ctx);
                mutex_unlock(&ctx->uring_lock);
                *locked = false;
        }
        percpu_ref_put(&ctx->refs);
}

static inline void ctx_commit_and_unlock(struct io_ring_ctx *ctx)
{
        io_commit_cqring(ctx);
        spin_unlock(&ctx->completion_lock);
        io_cqring_ev_posted(ctx);
}

static void handle_prev_tw_list(struct io_wq_work_node *node,
                                struct io_ring_ctx **ctx, bool *uring_locked)
{
        if (*ctx && !*uring_locked)
                spin_lock(&(*ctx)->completion_lock);

        do {
                struct io_wq_work_node *next = node->next;
                struct io_kiocb *req = container_of(node, struct io_kiocb,
                                                    io_task_work.node);

                prefetch(container_of(next, struct io_kiocb, io_task_work.node));

                if (req->ctx != *ctx) {
                        if (unlikely(!*uring_locked && *ctx))
                                ctx_commit_and_unlock(*ctx);

                        ctx_flush_and_put(*ctx, uring_locked);
                        *ctx = req->ctx;
                        /* if not contended, grab and improve batching */
                        *uring_locked = mutex_trylock(&(*ctx)->uring_lock);
                        percpu_ref_get(&(*ctx)->refs);
                        if (unlikely(!*uring_locked))
                                spin_lock(&(*ctx)->completion_lock);
                }
                if (likely(*uring_locked)) {
                        req->io_task_work.func(req, uring_locked);
                } else {
                        req->cqe.flags = io_put_kbuf_comp(req);
                        __io_req_complete_post(req);
                }
                node = next;
        } while (node);

        if (unlikely(!*uring_locked))
                ctx_commit_and_unlock(*ctx);
}

static void handle_tw_list(struct io_wq_work_node *node,
                           struct io_ring_ctx **ctx, bool *locked)
{
        do {
                struct io_wq_work_node *next = node->next;
                struct io_kiocb *req = container_of(node, struct io_kiocb,
                                                    io_task_work.node);

                prefetch(container_of(next, struct io_kiocb, io_task_work.node));

                if (req->ctx != *ctx) {
                        ctx_flush_and_put(*ctx, locked);
                        *ctx = req->ctx;
                        /* if not contended, grab and improve batching */
                        *locked = mutex_trylock(&(*ctx)->uring_lock);
                        percpu_ref_get(&(*ctx)->refs);
                }
                req->io_task_work.func(req, locked);
                node = next;
        } while (node);
}

static void tctx_task_work(struct callback_head *cb)
{
        bool uring_locked = false;
        struct io_ring_ctx *ctx = NULL;
        struct io_uring_task *tctx = container_of(cb, struct io_uring_task,
                                                  task_work);

        while (1) {
                struct io_wq_work_node *node1, *node2;

                spin_lock_irq(&tctx->task_lock);
                node1 = tctx->prio_task_list.first;
                node2 = tctx->task_list.first;
                INIT_WQ_LIST(&tctx->task_list);
                INIT_WQ_LIST(&tctx->prio_task_list);
                if (!node2 && !node1)
                        tctx->task_running = false;
                spin_unlock_irq(&tctx->task_lock);
                if (!node2 && !node1)
                        break;

                if (node1)
                        handle_prev_tw_list(node1, &ctx, &uring_locked);
                if (node2)
                        handle_tw_list(node2, &ctx, &uring_locked);
                cond_resched();

                if (data_race(!tctx->task_list.first) &&
                    data_race(!tctx->prio_task_list.first) && uring_locked)
                        io_submit_flush_completions(ctx);
        }

        ctx_flush_and_put(ctx, &uring_locked);

        /* relaxed read is enough as only the task itself sets ->in_idle */
        if (unlikely(atomic_read(&tctx->in_idle)))
                io_uring_drop_tctx_refs(current);
}

static void __io_req_task_work_add(struct io_kiocb *req,
                                   struct io_uring_task *tctx,
                                   struct io_wq_work_list *list)
{
        struct io_ring_ctx *ctx = req->ctx;
        struct io_wq_work_node *node;
        unsigned long flags;
        bool running;

        spin_lock_irqsave(&tctx->task_lock, flags);
        wq_list_add_tail(&req->io_task_work.node, list);
        running = tctx->task_running;
        if (!running)
                tctx->task_running = true;
        spin_unlock_irqrestore(&tctx->task_lock, flags);

        /* task_work already pending, we're done */
        if (running)
                return;

        if (ctx->flags & IORING_SETUP_TASKRUN_FLAG)
                atomic_or(IORING_SQ_TASKRUN, &ctx->rings->sq_flags);

        if (likely(!task_work_add(req->task, &tctx->task_work, ctx->notify_method)))
                return;

        spin_lock_irqsave(&tctx->task_lock, flags);
        tctx->task_running = false;
        node = wq_list_merge(&tctx->prio_task_list, &tctx->task_list);
        spin_unlock_irqrestore(&tctx->task_lock, flags);

        while (node) {
                req = container_of(node, struct io_kiocb, io_task_work.node);
                node = node->next;
                if (llist_add(&req->io_task_work.fallback_node,
                              &req->ctx->fallback_llist))
                        schedule_delayed_work(&req->ctx->fallback_work, 1);
        }
}

void io_req_task_work_add(struct io_kiocb *req)
{
        struct io_uring_task *tctx = req->task->io_uring;

        __io_req_task_work_add(req, tctx, &tctx->task_list);
}

static void io_req_task_prio_work_add(struct io_kiocb *req)
{
        struct io_uring_task *tctx = req->task->io_uring;

        if (req->ctx->flags & IORING_SETUP_SQPOLL)
                __io_req_task_work_add(req, tctx, &tctx->prio_task_list);
        else
                __io_req_task_work_add(req, tctx, &tctx->task_list);
}

static void io_req_tw_post(struct io_kiocb *req, bool *locked)
{
        io_req_complete_post(req);
}

void io_req_tw_post_queue(struct io_kiocb *req, s32 res, u32 cflags)
{
        io_req_set_res(req, res, cflags);
        req->io_task_work.func = io_req_tw_post;
        io_req_task_work_add(req);
}

static void io_req_task_cancel(struct io_kiocb *req, bool *locked)
{
        /* not needed for normal modes, but SQPOLL depends on it */
        io_tw_lock(req->ctx, locked);
        io_req_complete_failed(req, req->cqe.res);
}

static void io_req_task_submit(struct io_kiocb *req, bool *locked)
{
        io_tw_lock(req->ctx, locked);
        /* req->task == current here, checking PF_EXITING is safe */
        if (likely(!(req->task->flags & PF_EXITING)))
                io_queue_sqe(req);
        else
                io_req_complete_failed(req, -EFAULT);
}

void io_req_task_queue_fail(struct io_kiocb *req, int ret)
{
        io_req_set_res(req, ret, 0);
        req->io_task_work.func = io_req_task_cancel;
        io_req_task_work_add(req);
}

static void io_req_task_queue(struct io_kiocb *req)
{
        req->io_task_work.func = io_req_task_submit;
        io_req_task_work_add(req);
}

static void io_req_task_queue_reissue(struct io_kiocb *req)
{
        req->io_task_work.func = io_queue_iowq;
        io_req_task_work_add(req);
}

void io_queue_next(struct io_kiocb *req)
{
        struct io_kiocb *nxt = io_req_find_next(req);

        if (nxt)
                io_req_task_queue(nxt);
}

static void io_free_batch_list(struct io_ring_ctx *ctx,
                                struct io_wq_work_node *node)
        __must_hold(&ctx->uring_lock)
{
        struct task_struct *task = NULL;
        int task_refs = 0;

        do {
                struct io_kiocb *req = container_of(node, struct io_kiocb,
                                                    comp_list);

                if (unlikely(req->flags & IO_REQ_CLEAN_SLOW_FLAGS)) {
                        if (req->flags & REQ_F_REFCOUNT) {
                                node = req->comp_list.next;
                                if (!req_ref_put_and_test(req))
                                        continue;
                        }
                        if ((req->flags & REQ_F_POLLED) && req->apoll) {
                                struct async_poll *apoll = req->apoll;

                                if (apoll->double_poll)
                                        kfree(apoll->double_poll);
                                list_add(&apoll->poll.wait.entry,
                                                &ctx->apoll_cache);
                                req->flags &= ~REQ_F_POLLED;
                        }
                        if (req->flags & IO_REQ_LINK_FLAGS)
                                io_queue_next(req);
                        if (unlikely(req->flags & IO_REQ_CLEAN_FLAGS))
                                io_clean_op(req);
                }
                if (!(req->flags & REQ_F_FIXED_FILE))
                        io_put_file(req->file);

                io_req_put_rsrc_locked(req, ctx);

                if (req->task != task) {
                        if (task)
                                io_put_task(task, task_refs);
                        task = req->task;
                        task_refs = 0;
                }
                task_refs++;
                node = req->comp_list.next;
                io_req_add_to_cache(req, ctx);
        } while (node);

        if (task)
                io_put_task(task, task_refs);
}

static void __io_submit_flush_completions(struct io_ring_ctx *ctx)
        __must_hold(&ctx->uring_lock)
{
        struct io_wq_work_node *node, *prev;
        struct io_submit_state *state = &ctx->submit_state;

        if (state->flush_cqes) {
                spin_lock(&ctx->completion_lock);
                wq_list_for_each(node, prev, &state->compl_reqs) {
                        struct io_kiocb *req = container_of(node, struct io_kiocb,
                                                    comp_list);

                        if (!(req->flags & REQ_F_CQE_SKIP))
                                __io_fill_cqe_req(ctx, req);
                }

                io_commit_cqring(ctx);
                spin_unlock(&ctx->completion_lock);
                io_cqring_ev_posted(ctx);
                state->flush_cqes = false;
        }

        io_free_batch_list(ctx, state->compl_reqs.first);
        INIT_WQ_LIST(&state->compl_reqs);
}

/*
 * Drop reference to request, return next in chain (if there is one) if this
 * was the last reference to this request.
 */
static inline struct io_kiocb *io_put_req_find_next(struct io_kiocb *req)
{
        struct io_kiocb *nxt = NULL;

        if (req_ref_put_and_test(req)) {
                if (unlikely(req->flags & IO_REQ_LINK_FLAGS))
                        nxt = io_req_find_next(req);
                io_free_req(req);
        }
        return nxt;
}

static unsigned io_cqring_events(struct io_ring_ctx *ctx)
{
        /* See comment at the top of this file */
        smp_rmb();
        return __io_cqring_events(ctx);
}

static inline unsigned int io_sqring_entries(struct io_ring_ctx *ctx)
{
        struct io_rings *rings = ctx->rings;

        /* make sure SQ entry isn't read before tail */
        return smp_load_acquire(&rings->sq.tail) - ctx->cached_sq_head;
}

static inline bool io_run_task_work(void)
{
        if (test_thread_flag(TIF_NOTIFY_SIGNAL) || task_work_pending(current)) {
                __set_current_state(TASK_RUNNING);
                clear_notify_signal();
                if (task_work_pending(current))
                        task_work_run();
                return true;
        }

        return false;
}

static int io_do_iopoll(struct io_ring_ctx *ctx, bool force_nonspin)
{
        struct io_wq_work_node *pos, *start, *prev;
        unsigned int poll_flags = BLK_POLL_NOSLEEP;
        DEFINE_IO_COMP_BATCH(iob);
        int nr_events = 0;

        /*
         * Only spin for completions if we don't have multiple devices hanging
         * off our complete list.
         */
        if (ctx->poll_multi_queue || force_nonspin)
                poll_flags |= BLK_POLL_ONESHOT;

        wq_list_for_each(pos, start, &ctx->iopoll_list) {
                struct io_kiocb *req = container_of(pos, struct io_kiocb, comp_list);
                struct io_rw *rw = io_kiocb_to_cmd(req);
                int ret;

                /*
                 * Move completed and retryable entries to our local lists.
                 * If we find a request that requires polling, break out
                 * and complete those lists first, if we have entries there.
                 */
                if (READ_ONCE(req->iopoll_completed))
                        break;

                ret = rw->kiocb.ki_filp->f_op->iopoll(&rw->kiocb, &iob, poll_flags);
                if (unlikely(ret < 0))
                        return ret;
                else if (ret)
                        poll_flags |= BLK_POLL_ONESHOT;

                /* iopoll may have completed current req */
                if (!rq_list_empty(iob.req_list) ||
                    READ_ONCE(req->iopoll_completed))
                        break;
        }

        if (!rq_list_empty(iob.req_list))
                iob.complete(&iob);
        else if (!pos)
                return 0;

        prev = start;
        wq_list_for_each_resume(pos, prev) {
                struct io_kiocb *req = container_of(pos, struct io_kiocb, comp_list);

                /* order with io_complete_rw_iopoll(), e.g. ->result updates */
                if (!smp_load_acquire(&req->iopoll_completed))
                        break;
                nr_events++;
                if (unlikely(req->flags & REQ_F_CQE_SKIP))
                        continue;

                req->cqe.flags = io_put_kbuf(req, 0);
                __io_fill_cqe_req(req->ctx, req);
        }

        if (unlikely(!nr_events))
                return 0;

        io_commit_cqring(ctx);
        io_cqring_ev_posted_iopoll(ctx);
        pos = start ? start->next : ctx->iopoll_list.first;
        wq_list_cut(&ctx->iopoll_list, prev, start);
        io_free_batch_list(ctx, pos);
        return nr_events;
}

/*
 * We can't just wait for polled events to come to us, we have to actively
 * find and complete them.
 */
static __cold void io_iopoll_try_reap_events(struct io_ring_ctx *ctx)
{
        if (!(ctx->flags & IORING_SETUP_IOPOLL))
                return;

        mutex_lock(&ctx->uring_lock);
        while (!wq_list_empty(&ctx->iopoll_list)) {
                /* let it sleep and repeat later if can't complete a request */
                if (io_do_iopoll(ctx, true) == 0)
                        break;
                /*
                 * Ensure we allow local-to-the-cpu processing to take place,
                 * in this case we need to ensure that we reap all events.
                 * Also let task_work, etc. to progress by releasing the mutex
                 */
                if (need_resched()) {
                        mutex_unlock(&ctx->uring_lock);
                        cond_resched();
                        mutex_lock(&ctx->uring_lock);
                }
        }
        mutex_unlock(&ctx->uring_lock);
}

static int io_iopoll_check(struct io_ring_ctx *ctx, long min)
{
        unsigned int nr_events = 0;
        int ret = 0;
        unsigned long check_cq;

        /*
         * Don't enter poll loop if we already have events pending.
         * If we do, we can potentially be spinning for commands that
         * already triggered a CQE (eg in error).
         */
        check_cq = READ_ONCE(ctx->check_cq);
        if (check_cq & BIT(IO_CHECK_CQ_OVERFLOW_BIT))
                __io_cqring_overflow_flush(ctx, false);
        if (io_cqring_events(ctx))
                return 0;

        /*
         * Similarly do not spin if we have not informed the user of any
         * dropped CQE.
         */
        if (unlikely(check_cq & BIT(IO_CHECK_CQ_DROPPED_BIT)))
                return -EBADR;

        do {
                /*
                 * If a submit got punted to a workqueue, we can have the
                 * application entering polling for a command before it gets
                 * issued. That app will hold the uring_lock for the duration
                 * of the poll right here, so we need to take a breather every
                 * now and then to ensure that the issue has a chance to add
                 * the poll to the issued list. Otherwise we can spin here
                 * forever, while the workqueue is stuck trying to acquire the
                 * very same mutex.
                 */
                if (wq_list_empty(&ctx->iopoll_list)) {
                        u32 tail = ctx->cached_cq_tail;

                        mutex_unlock(&ctx->uring_lock);
                        io_run_task_work();
                        mutex_lock(&ctx->uring_lock);

                        /* some requests don't go through iopoll_list */
                        if (tail != ctx->cached_cq_tail ||
                            wq_list_empty(&ctx->iopoll_list))
                                break;
                }
                ret = io_do_iopoll(ctx, !min);
                if (ret < 0)
                        break;
                nr_events += ret;
                ret = 0;
        } while (nr_events < min && !need_resched());

        return ret;
}

static void kiocb_end_write(struct io_kiocb *req)
{
        /*
         * Tell lockdep we inherited freeze protection from submission
         * thread.
         */
        if (req->flags & REQ_F_ISREG) {
                struct super_block *sb = file_inode(req->file)->i_sb;

                __sb_writers_acquired(sb, SB_FREEZE_WRITE);
                sb_end_write(sb);
        }
}

#ifdef CONFIG_BLOCK
static bool io_resubmit_prep(struct io_kiocb *req)
{
        struct io_async_rw *io = req->async_data;

        if (!req_has_async_data(req))
                return !io_req_prep_async(req);
        iov_iter_restore(&io->s.iter, &io->s.iter_state);
        return true;
}

static bool io_rw_should_reissue(struct io_kiocb *req)
{
        umode_t mode = file_inode(req->file)->i_mode;
        struct io_ring_ctx *ctx = req->ctx;

        if (!S_ISBLK(mode) && !S_ISREG(mode))
                return false;
        if ((req->flags & REQ_F_NOWAIT) || (io_wq_current_is_worker() &&
            !(ctx->flags & IORING_SETUP_IOPOLL)))
                return false;
        /*
         * If ref is dying, we might be running poll reap from the exit work.
         * Don't attempt to reissue from that path, just let it fail with
         * -EAGAIN.
         */
        if (percpu_ref_is_dying(&ctx->refs))
                return false;
        /*
         * Play it safe and assume not safe to re-import and reissue if we're
         * not in the original thread group (or in task context).
         */
        if (!same_thread_group(req->task, current) || !in_task())
                return false;
        return true;
}
#else
static bool io_resubmit_prep(struct io_kiocb *req)
{
        return false;
}
static bool io_rw_should_reissue(struct io_kiocb *req)
{
        return false;
}
#endif

static bool __io_complete_rw_common(struct io_kiocb *req, long res)
{
        struct io_rw *rw = io_kiocb_to_cmd(req);

        if (rw->kiocb.ki_flags & IOCB_WRITE) {
                kiocb_end_write(req);
                fsnotify_modify(req->file);
        } else {
                fsnotify_access(req->file);
        }
        if (unlikely(res != req->cqe.res)) {
                if ((res == -EAGAIN || res == -EOPNOTSUPP) &&
                    io_rw_should_reissue(req)) {
                        req->flags |= REQ_F_REISSUE | REQ_F_PARTIAL_IO;
                        return true;
                }
                req_set_fail(req);
                req->cqe.res = res;
        }
        return false;
}

inline void io_req_task_complete(struct io_kiocb *req, bool *locked)
{
        if (*locked) {
                req->cqe.flags |= io_put_kbuf(req, 0);
                req->flags |= REQ_F_COMPLETE_INLINE;
                io_req_add_compl_list(req);
        } else {
                req->cqe.flags |= io_put_kbuf(req, IO_URING_F_UNLOCKED);
                io_req_complete_post(req);
        }
}

static void __io_complete_rw(struct io_kiocb *req, long res,
                             unsigned int issue_flags)
{
        if (__io_complete_rw_common(req, res))
                return;
        io_req_set_res(req, req->cqe.res, io_put_kbuf(req, issue_flags));
        __io_req_complete(req, issue_flags);
}

static void io_complete_rw(struct kiocb *kiocb, long res)
{
        struct io_rw *rw = container_of(kiocb, struct io_rw, kiocb);
        struct io_kiocb *req = cmd_to_io_kiocb(rw);

        if (__io_complete_rw_common(req, res))
                return;
        io_req_set_res(req, res, 0);
        req->io_task_work.func = io_req_task_complete;
        io_req_task_prio_work_add(req);
}

static void io_complete_rw_iopoll(struct kiocb *kiocb, long res)
{
        struct io_rw *rw = container_of(kiocb, struct io_rw, kiocb);
        struct io_kiocb *req = cmd_to_io_kiocb(rw);

        if (kiocb->ki_flags & IOCB_WRITE)
                kiocb_end_write(req);
        if (unlikely(res != req->cqe.res)) {
                if (res == -EAGAIN && io_rw_should_reissue(req)) {
                        req->flags |= REQ_F_REISSUE | REQ_F_PARTIAL_IO;
                        return;
                }
                req->cqe.res = res;
        }

        /* order with io_iopoll_complete() checking ->iopoll_completed */
        smp_store_release(&req->iopoll_completed, 1);
}

/*
 * After the iocb has been issued, it's safe to be found on the poll list.
 * Adding the kiocb to the list AFTER submission ensures that we don't
 * find it from a io_do_iopoll() thread before the issuer is done
 * accessing the kiocb cookie.
 */
static void io_iopoll_req_issued(struct io_kiocb *req, unsigned int issue_flags)
{
        struct io_ring_ctx *ctx = req->ctx;
        const bool needs_lock = issue_flags & IO_URING_F_UNLOCKED;

        /* workqueue context doesn't hold uring_lock, grab it now */
        if (unlikely(needs_lock))
                mutex_lock(&ctx->uring_lock);

        /*
         * Track whether we have multiple files in our lists. This will impact
         * how we do polling eventually, not spinning if we're on potentially
         * different devices.
         */
        if (wq_list_empty(&ctx->iopoll_list)) {
                ctx->poll_multi_queue = false;
        } else if (!ctx->poll_multi_queue) {
                struct io_kiocb *list_req;

                list_req = container_of(ctx->iopoll_list.first, struct io_kiocb,
                                        comp_list);
                if (list_req->file != req->file)
                        ctx->poll_multi_queue = true;
        }

        /*
         * For fast devices, IO may have already completed. If it has, add
         * it to the front so we find it first.
         */
        if (READ_ONCE(req->iopoll_completed))
                wq_list_add_head(&req->comp_list, &ctx->iopoll_list);
        else
                wq_list_add_tail(&req->comp_list, &ctx->iopoll_list);

        if (unlikely(needs_lock)) {
                /*
                 * If IORING_SETUP_SQPOLL is enabled, sqes are either handle
                 * in sq thread task context or in io worker task context. If
                 * current task context is sq thread, we don't need to check
                 * whether should wake up sq thread.
                 */
                if ((ctx->flags & IORING_SETUP_SQPOLL) &&
                    wq_has_sleeper(&ctx->sq_data->wait))
                        wake_up(&ctx->sq_data->wait);

                mutex_unlock(&ctx->uring_lock);
        }
}

static bool io_bdev_nowait(struct block_device *bdev)
{
        return !bdev || blk_queue_nowait(bdev_get_queue(bdev));
}

/*
 * If we tracked the file through the SCM inflight mechanism, we could support
 * any file. For now, just ensure that anything potentially problematic is done
 * inline.
 */
static bool __io_file_supports_nowait(struct file *file, umode_t mode)
{
        if (S_ISBLK(mode)) {
                if (IS_ENABLED(CONFIG_BLOCK) &&
                    io_bdev_nowait(I_BDEV(file->f_mapping->host)))
                        return true;
                return false;
        }
        if (S_ISSOCK(mode))
                return true;
        if (S_ISREG(mode)) {
                if (IS_ENABLED(CONFIG_BLOCK) &&
                    io_bdev_nowait(file->f_inode->i_sb->s_bdev) &&
                    file->f_op != &io_uring_fops)
                        return true;
                return false;
        }

        /* any ->read/write should understand O_NONBLOCK */
        if (file->f_flags & O_NONBLOCK)
                return true;
        return file->f_mode & FMODE_NOWAIT;
}

/*
 * If we tracked the file through the SCM inflight mechanism, we could support
 * any file. For now, just ensure that anything potentially problematic is done
 * inline.
 */
static unsigned int io_file_get_flags(struct file *file)
{
        umode_t mode = file_inode(file)->i_mode;
        unsigned int res = 0;

        if (S_ISREG(mode))
                res |= FFS_ISREG;
        if (__io_file_supports_nowait(file, mode))
                res |= FFS_NOWAIT;
        if (io_file_need_scm(file))
                res |= FFS_SCM;
        return res;
}

static inline bool io_file_supports_nowait(struct io_kiocb *req)
{
        return req->flags & REQ_F_SUPPORT_NOWAIT;
}

static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        struct io_rw *rw = io_kiocb_to_cmd(req);
        unsigned ioprio;
        int ret;

        rw->kiocb.ki_pos = READ_ONCE(sqe->off);
        /* used for fixed read/write too - just read unconditionally */
        req->buf_index = READ_ONCE(sqe->buf_index);

        if (req->opcode == IORING_OP_READ_FIXED ||
            req->opcode == IORING_OP_WRITE_FIXED) {
                struct io_ring_ctx *ctx = req->ctx;
                u16 index;

                if (unlikely(req->buf_index >= ctx->nr_user_bufs))
                        return -EFAULT;
                index = array_index_nospec(req->buf_index, ctx->nr_user_bufs);
                req->imu = ctx->user_bufs[index];
                io_req_set_rsrc_node(req, ctx, 0);
        }

        ioprio = READ_ONCE(sqe->ioprio);
        if (ioprio) {
                ret = ioprio_check_cap(ioprio);
                if (ret)
                        return ret;

                rw->kiocb.ki_ioprio = ioprio;
        } else {
                rw->kiocb.ki_ioprio = get_current_ioprio();
        }

        rw->addr = READ_ONCE(sqe->addr);
        rw->len = READ_ONCE(sqe->len);
        rw->flags = READ_ONCE(sqe->rw_flags);
        return 0;
}

static void io_readv_writev_cleanup(struct io_kiocb *req)
{
        struct io_async_rw *io = req->async_data;

        kfree(io->free_iovec);
}

static inline void io_rw_done(struct kiocb *kiocb, ssize_t ret)
{
        switch (ret) {
        case -EIOCBQUEUED:
                break;
        case -ERESTARTSYS:
        case -ERESTARTNOINTR:
        case -ERESTARTNOHAND:
        case -ERESTART_RESTARTBLOCK:
                /*
                 * We can't just restart the syscall, since previously
                 * submitted sqes may already be in progress. Just fail this
                 * IO with EINTR.
                 */
                ret = -EINTR;
                fallthrough;
        default:
                kiocb->ki_complete(kiocb, ret);
        }
}

static inline loff_t *io_kiocb_update_pos(struct io_kiocb *req)
{
        struct io_rw *rw = io_kiocb_to_cmd(req);

        if (rw->kiocb.ki_pos != -1)
                return &rw->kiocb.ki_pos;

        if (!(req->file->f_mode & FMODE_STREAM)) {
                req->flags |= REQ_F_CUR_POS;
                rw->kiocb.ki_pos = req->file->f_pos;
                return &rw->kiocb.ki_pos;
        }

        rw->kiocb.ki_pos = 0;
        return NULL;
}

static void kiocb_done(struct io_kiocb *req, ssize_t ret,
                       unsigned int issue_flags)
{
        struct io_async_rw *io = req->async_data;
        struct io_rw *rw = io_kiocb_to_cmd(req);

        /* add previously done IO, if any */
        if (req_has_async_data(req) && io->bytes_done > 0) {
                if (ret < 0)
                        ret = io->bytes_done;
                else
                        ret += io->bytes_done;
        }

        if (req->flags & REQ_F_CUR_POS)
                req->file->f_pos = rw->kiocb.ki_pos;
        if (ret >= 0 && (rw->kiocb.ki_complete == io_complete_rw))
                __io_complete_rw(req, ret, issue_flags);
        else
                io_rw_done(&rw->kiocb, ret);

        if (req->flags & REQ_F_REISSUE) {
                req->flags &= ~REQ_F_REISSUE;
                if (io_resubmit_prep(req))
                        io_req_task_queue_reissue(req);
                else
                        io_req_task_queue_fail(req, ret);
        }
}

static int __io_import_fixed(struct io_kiocb *req, int ddir,
                             struct iov_iter *iter, struct io_mapped_ubuf *imu)
{
        struct io_rw *rw = io_kiocb_to_cmd(req);
        size_t len = rw->len;
        u64 buf_end, buf_addr = rw->addr;
        size_t offset;

        if (unlikely(check_add_overflow(buf_addr, (u64)len, &buf_end)))
                return -EFAULT;
        /* not inside the mapped region */
        if (unlikely(buf_addr < imu->ubuf || buf_end > imu->ubuf_end))
                return -EFAULT;

        /*
         * May not be a start of buffer, set size appropriately
         * and advance us to the beginning.
         */
        offset = buf_addr - imu->ubuf;
        iov_iter_bvec(iter, ddir, imu->bvec, imu->nr_bvecs, offset + len);

        if (offset) {
                /*
                 * Don't use iov_iter_advance() here, as it's really slow for
                 * using the latter parts of a big fixed buffer - it iterates
                 * over each segment manually. We can cheat a bit here, because
                 * we know that:
                 *
                 * 1) it's a BVEC iter, we set it up
                 * 2) all bvecs are PAGE_SIZE in size, except potentially the
                 *    first and last bvec
                 *
                 * So just find our index, and adjust the iterator afterwards.
                 * If the offset is within the first bvec (or the whole first
                 * bvec, just use iov_iter_advance(). This makes it easier
                 * since we can just skip the first segment, which may not
                 * be PAGE_SIZE aligned.
                 */
                const struct bio_vec *bvec = imu->bvec;

                if (offset <= bvec->bv_len) {
                        iov_iter_advance(iter, offset);
                } else {
                        unsigned long seg_skip;

                        /* skip first vec */
                        offset -= bvec->bv_len;
                        seg_skip = 1 + (offset >> PAGE_SHIFT);

                        iter->bvec = bvec + seg_skip;
                        iter->nr_segs -= seg_skip;
                        iter->count -= bvec->bv_len + offset;
                        iter->iov_offset = offset & ~PAGE_MASK;
                }
        }

        return 0;
}

static int io_import_fixed(struct io_kiocb *req, int rw, struct iov_iter *iter,
                           unsigned int issue_flags)
{
        if (WARN_ON_ONCE(!req->imu))
                return -EFAULT;
        return __io_import_fixed(req, rw, iter, req->imu);
}

static int io_buffer_add_list(struct io_ring_ctx *ctx,
                              struct io_buffer_list *bl, unsigned int bgid)
{
        bl->bgid = bgid;
        if (bgid < BGID_ARRAY)
                return 0;

        return xa_err(xa_store(&ctx->io_bl_xa, bgid, bl, GFP_KERNEL));
}

static void __user *io_provided_buffer_select(struct io_kiocb *req, size_t *len,
                                              struct io_buffer_list *bl)
{
        if (!list_empty(&bl->buf_list)) {
                struct io_buffer *kbuf;

                kbuf = list_first_entry(&bl->buf_list, struct io_buffer, list);
                list_del(&kbuf->list);
                if (*len > kbuf->len)
                        *len = kbuf->len;
                req->flags |= REQ_F_BUFFER_SELECTED;
                req->kbuf = kbuf;
                req->buf_index = kbuf->bid;
                return u64_to_user_ptr(kbuf->addr);
        }
        return NULL;
}

static void __user *io_ring_buffer_select(struct io_kiocb *req, size_t *len,
                                          struct io_buffer_list *bl,
                                          unsigned int issue_flags)
{
        struct io_uring_buf_ring *br = bl->buf_ring;
        struct io_uring_buf *buf;
        __u16 head = bl->head;

        if (unlikely(smp_load_acquire(&br->tail) == head))
                return NULL;

        head &= bl->mask;
        if (head < IO_BUFFER_LIST_BUF_PER_PAGE) {
                buf = &br->bufs[head];
        } else {
                int off = head & (IO_BUFFER_LIST_BUF_PER_PAGE - 1);
                int index = head / IO_BUFFER_LIST_BUF_PER_PAGE;
                buf = page_address(bl->buf_pages[index]);
                buf += off;
        }
        if (*len > buf->len)
                *len = buf->len;
        req->flags |= REQ_F_BUFFER_RING;
        req->buf_list = bl;
        req->buf_index = buf->bid;

        if (issue_flags & IO_URING_F_UNLOCKED || !file_can_poll(req->file)) {
                /*
                 * If we came in unlocked, we have no choice but to consume the
                 * buffer here. This does mean it'll be pinned until the IO
                 * completes. But coming in unlocked means we're in io-wq
                 * context, hence there should be no further retry. For the
                 * locked case, the caller must ensure to call the commit when
                 * the transfer completes (or if we get -EAGAIN and must poll
                 * or retry).
                 */
                req->buf_list = NULL;
                bl->head++;
        }
        return u64_to_user_ptr(buf->addr);
}

void __user *io_buffer_select(struct io_kiocb *req, size_t *len,
                              unsigned int issue_flags)
{
        struct io_ring_ctx *ctx = req->ctx;
        struct io_buffer_list *bl;
        void __user *ret = NULL;

        io_ring_submit_lock(req->ctx, issue_flags);

        bl = io_buffer_get_list(ctx, req->buf_index);
        if (likely(bl)) {
                if (bl->buf_nr_pages)
                        ret = io_ring_buffer_select(req, len, bl, issue_flags);
                else
                        ret = io_provided_buffer_select(req, len, bl);
        }
        io_ring_submit_unlock(req->ctx, issue_flags);
        return ret;
}

#ifdef CONFIG_COMPAT
static ssize_t io_compat_import(struct io_kiocb *req, struct iovec *iov,
                                unsigned int issue_flags)
{
        struct io_rw *rw = io_kiocb_to_cmd(req);
        struct compat_iovec __user *uiov;
        compat_ssize_t clen;
        void __user *buf;
        size_t len;

        uiov = u64_to_user_ptr(rw->addr);
        if (!access_ok(uiov, sizeof(*uiov)))
                return -EFAULT;
        if (__get_user(clen, &uiov->iov_len))
                return -EFAULT;
        if (clen < 0)
                return -EINVAL;

        len = clen;
        buf = io_buffer_select(req, &len, issue_flags);
        if (!buf)
                return -ENOBUFS;
        rw->addr = (unsigned long) buf;
        iov[0].iov_base = buf;
        rw->len = iov[0].iov_len = (compat_size_t) len;
        return 0;
}
#endif

static ssize_t __io_iov_buffer_select(struct io_kiocb *req, struct iovec *iov,
                                      unsigned int issue_flags)
{
        struct io_rw *rw = io_kiocb_to_cmd(req);
        struct iovec __user *uiov = u64_to_user_ptr(rw->addr);
        void __user *buf;
        ssize_t len;

        if (copy_from_user(iov, uiov, sizeof(*uiov)))
                return -EFAULT;

        len = iov[0].iov_len;
        if (len < 0)
                return -EINVAL;
        buf = io_buffer_select(req, &len, issue_flags);
        if (!buf)
                return -ENOBUFS;
        rw->addr = (unsigned long) buf;
        iov[0].iov_base = buf;
        rw->len = iov[0].iov_len = len;
        return 0;
}

static ssize_t io_iov_buffer_select(struct io_kiocb *req, struct iovec *iov,
                                    unsigned int issue_flags)
{
        struct io_rw *rw = io_kiocb_to_cmd(req);

        if (req->flags & (REQ_F_BUFFER_SELECTED|REQ_F_BUFFER_RING)) {
                iov[0].iov_base = u64_to_user_ptr(rw->addr);
                iov[0].iov_len = rw->len;
                return 0;
        }
        if (rw->len != 1)
                return -EINVAL;

#ifdef CONFIG_COMPAT
        if (req->ctx->compat)
                return io_compat_import(req, iov, issue_flags);
#endif

        return __io_iov_buffer_select(req, iov, issue_flags);
}

static struct iovec *__io_import_iovec(int ddir, struct io_kiocb *req,
                                       struct io_rw_state *s,
                                       unsigned int issue_flags)
{
        struct io_rw *rw = io_kiocb_to_cmd(req);
        struct iov_iter *iter = &s->iter;
        u8 opcode = req->opcode;
        struct iovec *iovec;
        void __user *buf;
        size_t sqe_len;
        ssize_t ret;

        if (opcode == IORING_OP_READ_FIXED || opcode == IORING_OP_WRITE_FIXED) {
                ret = io_import_fixed(req, ddir, iter, issue_flags);
                if (ret)
                        return ERR_PTR(ret);
                return NULL;
        }

        buf = u64_to_user_ptr(rw->addr);
        sqe_len = rw->len;

        if (opcode == IORING_OP_READ || opcode == IORING_OP_WRITE) {
                if (io_do_buffer_select(req)) {
                        buf = io_buffer_select(req, &sqe_len, issue_flags);
                        if (!buf)
                                return ERR_PTR(-ENOBUFS);
                        rw->addr = (unsigned long) buf;
                        rw->len = sqe_len;
                }

                ret = import_single_range(ddir, buf, sqe_len, s->fast_iov, iter);
                if (ret)
                        return ERR_PTR(ret);
                return NULL;
        }

        iovec = s->fast_iov;
        if (req->flags & REQ_F_BUFFER_SELECT) {
                ret = io_iov_buffer_select(req, iovec, issue_flags);
                if (ret)
                        return ERR_PTR(ret);
                iov_iter_init(iter, ddir, iovec, 1, iovec->iov_len);
                return NULL;
        }

        ret = __import_iovec(ddir, buf, sqe_len, UIO_FASTIOV, &iovec, iter,
                              req->ctx->compat);
        if (unlikely(ret < 0))
                return ERR_PTR(ret);
        return iovec;
}

static inline int io_import_iovec(int rw, struct io_kiocb *req,
                                  struct iovec **iovec, struct io_rw_state *s,
                                  unsigned int issue_flags)
{
        *iovec = __io_import_iovec(rw, req, s, issue_flags);
        if (unlikely(IS_ERR(*iovec)))
                return PTR_ERR(*iovec);

        iov_iter_save_state(&s->iter, &s->iter_state);
        return 0;
}

static inline loff_t *io_kiocb_ppos(struct kiocb *kiocb)
{
        return (kiocb->ki_filp->f_mode & FMODE_STREAM) ? NULL : &kiocb->ki_pos;
}

/*
 * For files that don't have ->read_iter() and ->write_iter(), handle them
 * by looping over ->read() or ->write() manually.
 */
static ssize_t loop_rw_iter(int ddir, struct io_rw *rw, struct iov_iter *iter)
{
        struct kiocb *kiocb = &rw->kiocb;
        struct file *file = kiocb->ki_filp;
        ssize_t ret = 0;
        loff_t *ppos;

        /*
         * Don't support polled IO through this interface, and we can't
         * support non-blocking either. For the latter, this just causes
         * the kiocb to be handled from an async context.
         */
        if (kiocb->ki_flags & IOCB_HIPRI)
                return -EOPNOTSUPP;
        if ((kiocb->ki_flags & IOCB_NOWAIT) &&
            !(kiocb->ki_filp->f_flags & O_NONBLOCK))
                return -EAGAIN;

        ppos = io_kiocb_ppos(kiocb);

        while (iov_iter_count(iter)) {
                struct iovec iovec;
                ssize_t nr;

                if (!iov_iter_is_bvec(iter)) {
                        iovec = iov_iter_iovec(iter);
                } else {
                        iovec.iov_base = u64_to_user_ptr(rw->addr);
                        iovec.iov_len = rw->len;
                }

                if (ddir == READ) {
                        nr = file->f_op->read(file, iovec.iov_base,
                                              iovec.iov_len, ppos);
                } else {
                        nr = file->f_op->write(file, iovec.iov_base,
                                               iovec.iov_len, ppos);
                }

                if (nr < 0) {
                        if (!ret)
                                ret = nr;
                        break;
                }
                ret += nr;
                if (!iov_iter_is_bvec(iter)) {
                        iov_iter_advance(iter, nr);
                } else {
                        rw->addr += nr;
                        rw->len -= nr;
                        if (!rw->len)
                                break;
                }
                if (nr != iovec.iov_len)
                        break;
        }

        return ret;
}

static void io_req_map_rw(struct io_kiocb *req, const struct iovec *iovec,
                          const struct iovec *fast_iov, struct iov_iter *iter)
{
        struct io_async_rw *io = req->async_data;

        memcpy(&io->s.iter, iter, sizeof(*iter));
        io->free_iovec = iovec;
        io->bytes_done = 0;
        /* can only be fixed buffers, no need to do anything */
        if (iov_iter_is_bvec(iter))
                return;
        if (!iovec) {
                unsigned iov_off = 0;

                io->s.iter.iov = io->s.fast_iov;
                if (iter->iov != fast_iov) {
                        iov_off = iter->iov - fast_iov;
                        io->s.iter.iov += iov_off;
                }
                if (io->s.fast_iov != fast_iov)
                        memcpy(io->s.fast_iov + iov_off, fast_iov + iov_off,
                               sizeof(struct iovec) * iter->nr_segs);
        } else {
                req->flags |= REQ_F_NEED_CLEANUP;
        }
}

bool io_alloc_async_data(struct io_kiocb *req)
{
        WARN_ON_ONCE(!io_op_defs[req->opcode].async_size);
        req->async_data = kmalloc(io_op_defs[req->opcode].async_size, GFP_KERNEL);
        if (req->async_data) {
                req->flags |= REQ_F_ASYNC_DATA;
                return false;
        }
        return true;
}

static int io_setup_async_rw(struct io_kiocb *req, const struct iovec *iovec,
                             struct io_rw_state *s, bool force)
{
        if (!force && !io_op_defs[req->opcode].prep_async)
                return 0;
        if (!req_has_async_data(req)) {
                struct io_async_rw *iorw;

                if (io_alloc_async_data(req)) {
                        kfree(iovec);
                        return -ENOMEM;
                }

                io_req_map_rw(req, iovec, s->fast_iov, &s->iter);
                iorw = req->async_data;
                /* we've copied and mapped the iter, ensure state is saved */
                iov_iter_save_state(&iorw->s.iter, &iorw->s.iter_state);
        }
        return 0;
}

static inline int io_rw_prep_async(struct io_kiocb *req, int rw)
{
        struct io_async_rw *iorw = req->async_data;
        struct iovec *iov;
        int ret;

        /* submission path, ->uring_lock should already be taken */
        ret = io_import_iovec(rw, req, &iov, &iorw->s, 0);
        if (unlikely(ret < 0))
                return ret;

        iorw->bytes_done = 0;
        iorw->free_iovec = iov;
        if (iov)
                req->flags |= REQ_F_NEED_CLEANUP;
        return 0;
}

static int io_readv_prep_async(struct io_kiocb *req)
{
        return io_rw_prep_async(req, READ);
}

static int io_writev_prep_async(struct io_kiocb *req)
{
        return io_rw_prep_async(req, WRITE);
}

/*
 * This is our waitqueue callback handler, registered through __folio_lock_async()
 * when we initially tried to do the IO with the iocb armed our waitqueue.
 * This gets called when the page is unlocked, and we generally expect that to
 * happen when the page IO is completed and the page is now uptodate. This will
 * queue a task_work based retry of the operation, attempting to copy the data
 * again. If the latter fails because the page was NOT uptodate, then we will
 * do a thread based blocking retry of the operation. That's the unexpected
 * slow path.
 */
static int io_async_buf_func(struct wait_queue_entry *wait, unsigned mode,
                             int sync, void *arg)
{
        struct wait_page_queue *wpq;
        struct io_kiocb *req = wait->private;
        struct io_rw *rw = io_kiocb_to_cmd(req);
        struct wait_page_key *key = arg;

        wpq = container_of(wait, struct wait_page_queue, wait);

        if (!wake_page_match(wpq, key))
                return 0;

        rw->kiocb.ki_flags &= ~IOCB_WAITQ;
        list_del_init(&wait->entry);
        io_req_task_queue(req);
        return 1;
}

/*
 * This controls whether a given IO request should be armed for async page
 * based retry. If we return false here, the request is handed to the async
 * worker threads for retry. If we're doing buffered reads on a regular file,
 * we prepare a private wait_page_queue entry and retry the operation. This
 * will either succeed because the page is now uptodate and unlocked, or it
 * will register a callback when the page is unlocked at IO completion. Through
 * that callback, io_uring uses task_work to setup a retry of the operation.
 * That retry will attempt the buffered read again. The retry will generally
 * succeed, or in rare cases where it fails, we then fall back to using the
 * async worker threads for a blocking retry.
 */
static bool io_rw_should_retry(struct io_kiocb *req)
{
        struct io_async_rw *io = req->async_data;
        struct wait_page_queue *wait = &io->wpq;
        struct io_rw *rw = io_kiocb_to_cmd(req);
        struct kiocb *kiocb = &rw->kiocb;

        /* never retry for NOWAIT, we just complete with -EAGAIN */
        if (req->flags & REQ_F_NOWAIT)
                return false;

        /* Only for buffered IO */
        if (kiocb->ki_flags & (IOCB_DIRECT | IOCB_HIPRI))
                return false;

        /*
         * just use poll if we can, and don't attempt if the fs doesn't
         * support callback based unlocks
         */
        if (file_can_poll(req->file) || !(req->file->f_mode & FMODE_BUF_RASYNC))
                return false;

        wait->wait.func = io_async_buf_func;
        wait->wait.private = req;
        wait->wait.flags = 0;
        INIT_LIST_HEAD(&wait->wait.entry);
        kiocb->ki_flags |= IOCB_WAITQ;
        kiocb->ki_flags &= ~IOCB_NOWAIT;
        kiocb->ki_waitq = wait;
        return true;
}

static inline int io_iter_do_read(struct io_rw *rw, struct iov_iter *iter)
{
        struct file *file = rw->kiocb.ki_filp;

        if (likely(file->f_op->read_iter))
                return call_read_iter(file, &rw->kiocb, iter);
        else if (file->f_op->read)
                return loop_rw_iter(READ, rw, iter);
        else
                return -EINVAL;
}

static bool need_read_all(struct io_kiocb *req)
{
        return req->flags & REQ_F_ISREG ||
                S_ISBLK(file_inode(req->file)->i_mode);
}

static int io_rw_init_file(struct io_kiocb *req, fmode_t mode)
{
        struct io_rw *rw = io_kiocb_to_cmd(req);
        struct kiocb *kiocb = &rw->kiocb;
        struct io_ring_ctx *ctx = req->ctx;
        struct file *file = req->file;
        int ret;

        if (unlikely(!file || !(file->f_mode & mode)))
                return -EBADF;

        if (!io_req_ffs_set(req))
                req->flags |= io_file_get_flags(file) << REQ_F_SUPPORT_NOWAIT_BIT;

        kiocb->ki_flags = iocb_flags(file);
        ret = kiocb_set_rw_flags(kiocb, rw->flags);
        if (unlikely(ret))
                return ret;

        /*
         * If the file is marked O_NONBLOCK, still allow retry for it if it
         * supports async. Otherwise it's impossible to use O_NONBLOCK files
         * reliably. If not, or it IOCB_NOWAIT is set, don't retry.
         */
        if ((kiocb->ki_flags & IOCB_NOWAIT) ||
            ((file->f_flags & O_NONBLOCK) && !io_file_supports_nowait(req)))
                req->flags |= REQ_F_NOWAIT;

        if (ctx->flags & IORING_SETUP_IOPOLL) {
                if (!(kiocb->ki_flags & IOCB_DIRECT) || !file->f_op->iopoll)
                        return -EOPNOTSUPP;

                kiocb->private = NULL;
                kiocb->ki_flags |= IOCB_HIPRI | IOCB_ALLOC_CACHE;
                kiocb->ki_complete = io_complete_rw_iopoll;
                req->iopoll_completed = 0;
        } else {
                if (kiocb->ki_flags & IOCB_HIPRI)
                        return -EINVAL;
                kiocb->ki_complete = io_complete_rw;
        }

        return 0;
}

static int io_read(struct io_kiocb *req, unsigned int issue_flags)
{
        struct io_rw *rw = io_kiocb_to_cmd(req);
        struct io_rw_state __s, *s = &__s;
        struct iovec *iovec;
        struct kiocb *kiocb = &rw->kiocb;
        bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
        struct io_async_rw *io;
        ssize_t ret, ret2;
        loff_t *ppos;

        if (!req_has_async_data(req)) {
                ret = io_import_iovec(READ, req, &iovec, s, issue_flags);
                if (unlikely(ret < 0))
                        return ret;
        } else {
                io = req->async_data;
                s = &io->s;

                /*
                 * Safe and required to re-import if we're using provided
                 * buffers, as we dropped the selected one before retry.
                 */
                if (io_do_buffer_select(req)) {
                        ret = io_import_iovec(READ, req, &iovec, s, issue_flags);
                        if (unlikely(ret < 0))
                                return ret;
                }

                /*
                 * We come here from an earlier attempt, restore our state to
                 * match in case it doesn't. It's cheap enough that we don't
                 * need to make this conditional.
                 */
                iov_iter_restore(&s->iter, &s->iter_state);
                iovec = NULL;
        }
        ret = io_rw_init_file(req, FMODE_READ);
        if (unlikely(ret)) {
                kfree(iovec);
                return ret;
        }
        req->cqe.res = iov_iter_count(&s->iter);

        if (force_nonblock) {
                /* If the file doesn't support async, just async punt */
                if (unlikely(!io_file_supports_nowait(req))) {
                        ret = io_setup_async_rw(req, iovec, s, true);
                        return ret ?: -EAGAIN;
                }
                kiocb->ki_flags |= IOCB_NOWAIT;
        } else {
                /* Ensure we clear previously set non-block flag */
                kiocb->ki_flags &= ~IOCB_NOWAIT;
        }

        ppos = io_kiocb_update_pos(req);

        ret = rw_verify_area(READ, req->file, ppos, req->cqe.res);
        if (unlikely(ret)) {
                kfree(iovec);
                return ret;
        }

        ret = io_iter_do_read(rw, &s->iter);

        if (ret == -EAGAIN || (req->flags & REQ_F_REISSUE)) {
                req->flags &= ~REQ_F_REISSUE;
                /* if we can poll, just do that */
                if (req->opcode == IORING_OP_READ && file_can_poll(req->file))
                        return -EAGAIN;
                /* IOPOLL retry should happen for io-wq threads */
                if (!force_nonblock && !(req->ctx->flags & IORING_SETUP_IOPOLL))
                        goto done;
                /* no retry on NONBLOCK nor RWF_NOWAIT */
                if (req->flags & REQ_F_NOWAIT)
                        goto done;
                ret = 0;
        } else if (ret == -EIOCBQUEUED) {
                goto out_free;
        } else if (ret == req->cqe.res || ret <= 0 || !force_nonblock ||
                   (req->flags & REQ_F_NOWAIT) || !need_read_all(req)) {
                /* read all, failed, already did sync or don't want to retry */
                goto done;
        }

        /*
         * Don't depend on the iter state matching what was consumed, or being
         * untouched in case of error. Restore it and we'll advance it
         * manually if we need to.
         */
        iov_iter_restore(&s->iter, &s->iter_state);

        ret2 = io_setup_async_rw(req, iovec, s, true);
        if (ret2)
                return ret2;

        iovec = NULL;
        io = req->async_data;
        s = &io->s;
        /*
         * Now use our persistent iterator and state, if we aren't already.
         * We've restored and mapped the iter to match.
         */

        do {
                /*
                 * We end up here because of a partial read, either from
                 * above or inside this loop. Advance the iter by the bytes
                 * that were consumed.
                 */
                iov_iter_advance(&s->iter, ret);
                if (!iov_iter_count(&s->iter))
                        break;
                io->bytes_done += ret;
                iov_iter_save_state(&s->iter, &s->iter_state);

                /* if we can retry, do so with the callbacks armed */
                if (!io_rw_should_retry(req)) {
                        kiocb->ki_flags &= ~IOCB_WAITQ;
                        return -EAGAIN;
                }

                /*
                 * Now retry read with the IOCB_WAITQ parts set in the iocb. If
                 * we get -EIOCBQUEUED, then we'll get a notification when the
                 * desired page gets unlocked. We can also get a partial read
                 * here, and if we do, then just retry at the new offset.
                 */
                ret = io_iter_do_read(rw, &s->iter);
                if (ret == -EIOCBQUEUED)
                        return IOU_ISSUE_SKIP_COMPLETE;
                /* we got some bytes, but not all. retry. */
                kiocb->ki_flags &= ~IOCB_WAITQ;
                iov_iter_restore(&s->iter, &s->iter_state);
        } while (ret > 0);
done:
        kiocb_done(req, ret, issue_flags);
out_free:
        /* it's faster to check here then delegate to kfree */
        if (iovec)
                kfree(iovec);
        return IOU_ISSUE_SKIP_COMPLETE;
}

static int io_write(struct io_kiocb *req, unsigned int issue_flags)
{
        struct io_rw *rw = io_kiocb_to_cmd(req);
        struct io_rw_state __s, *s = &__s;
        struct iovec *iovec;
        struct kiocb *kiocb = &rw->kiocb;
        bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
        ssize_t ret, ret2;
        loff_t *ppos;

        if (!req_has_async_data(req)) {
                ret = io_import_iovec(WRITE, req, &iovec, s, issue_flags);
                if (unlikely(ret < 0))
                        return ret;
        } else {
                struct io_async_rw *io = req->async_data;

                s = &io->s;
                iov_iter_restore(&s->iter, &s->iter_state);
                iovec = NULL;
        }
        ret = io_rw_init_file(req, FMODE_WRITE);
        if (unlikely(ret)) {
                kfree(iovec);
                return ret;
        }
        req->cqe.res = iov_iter_count(&s->iter);

        if (force_nonblock) {
                /* If the file doesn't support async, just async punt */
                if (unlikely(!io_file_supports_nowait(req)))
                        goto copy_iov;

                /* file path doesn't support NOWAIT for non-direct_IO */
                if (force_nonblock && !(kiocb->ki_flags & IOCB_DIRECT) &&
                    (req->flags & REQ_F_ISREG))
                        goto copy_iov;

                kiocb->ki_flags |= IOCB_NOWAIT;
        } else {
                /* Ensure we clear previously set non-block flag */
                kiocb->ki_flags &= ~IOCB_NOWAIT;
        }

        ppos = io_kiocb_update_pos(req);

        ret = rw_verify_area(WRITE, req->file, ppos, req->cqe.res);
        if (unlikely(ret))
                goto out_free;

        /*
         * Open-code file_start_write here to grab freeze protection,
         * which will be released by another thread in
         * io_complete_rw().  Fool lockdep by telling it the lock got
         * released so that it doesn't complain about the held lock when
         * we return to userspace.
         */
        if (req->flags & REQ_F_ISREG) {
                sb_start_write(file_inode(req->file)->i_sb);
                __sb_writers_release(file_inode(req->file)->i_sb,
                                        SB_FREEZE_WRITE);
        }
        kiocb->ki_flags |= IOCB_WRITE;

        if (likely(req->file->f_op->write_iter))
                ret2 = call_write_iter(req->file, kiocb, &s->iter);
        else if (req->file->f_op->write)
                ret2 = loop_rw_iter(WRITE, rw, &s->iter);
        else
                ret2 = -EINVAL;

        if (req->flags & REQ_F_REISSUE) {
                req->flags &= ~REQ_F_REISSUE;
                ret2 = -EAGAIN;
        }

        /*
         * Raw bdev writes will return -EOPNOTSUPP for IOCB_NOWAIT. Just
         * retry them without IOCB_NOWAIT.
         */
        if (ret2 == -EOPNOTSUPP && (kiocb->ki_flags & IOCB_NOWAIT))
                ret2 = -EAGAIN;
        /* no retry on NONBLOCK nor RWF_NOWAIT */
        if (ret2 == -EAGAIN && (req->flags & REQ_F_NOWAIT))
                goto done;
        if (!force_nonblock || ret2 != -EAGAIN) {
                /* IOPOLL retry should happen for io-wq threads */
                if (ret2 == -EAGAIN && (req->ctx->flags & IORING_SETUP_IOPOLL))
                        goto copy_iov;
done:
                kiocb_done(req, ret2, issue_flags);
                ret = IOU_ISSUE_SKIP_COMPLETE;
        } else {
copy_iov:
                iov_iter_restore(&s->iter, &s->iter_state);
                ret = io_setup_async_rw(req, iovec, s, false);
                return ret ?: -EAGAIN;
        }
out_free:
        /* it's reportedly faster than delegating the null check to kfree() */
        if (iovec)
                kfree(iovec);
        return ret;
}

/*
 * Note when io_fixed_fd_install() returns error value, it will ensure
 * fput() is called correspondingly.
 */
int io_fixed_fd_install(struct io_kiocb *req, unsigned int issue_flags,
                        struct file *file, unsigned int file_slot)
{
        bool alloc_slot = file_slot == IORING_FILE_INDEX_ALLOC;
        struct io_ring_ctx *ctx = req->ctx;
        int ret;

        io_ring_submit_lock(ctx, issue_flags);

        if (alloc_slot) {
                ret = io_file_bitmap_get(ctx);
                if (unlikely(ret < 0))
                        goto err;
                file_slot = ret;
        } else {
                file_slot--;
        }

        ret = io_install_fixed_file(req, file, issue_flags, file_slot);
        if (!ret && alloc_slot)
                ret = file_slot;
err:
        io_ring_submit_unlock(ctx, issue_flags);
        if (unlikely(ret < 0))
                fput(file);
        return ret;
}

static int io_remove_buffers_prep(struct io_kiocb *req,
                                  const struct io_uring_sqe *sqe)
{
        struct io_provide_buf *p = io_kiocb_to_cmd(req);
        u64 tmp;

        if (sqe->rw_flags || sqe->addr || sqe->len || sqe->off ||
            sqe->splice_fd_in)
                return -EINVAL;

        tmp = READ_ONCE(sqe->fd);
        if (!tmp || tmp > USHRT_MAX)
                return -EINVAL;

        memset(p, 0, sizeof(*p));
        p->nbufs = tmp;
        p->bgid = READ_ONCE(sqe->buf_group);
        return 0;
}

static int __io_remove_buffers(struct io_ring_ctx *ctx,
                               struct io_buffer_list *bl, unsigned nbufs)
{
        unsigned i = 0;

        /* shouldn't happen */
        if (!nbufs)
                return 0;

        if (bl->buf_nr_pages) {
                int j;

                i = bl->buf_ring->tail - bl->head;
                for (j = 0; j < bl->buf_nr_pages; j++)
                        unpin_user_page(bl->buf_pages[j]);
                kvfree(bl->buf_pages);
                bl->buf_pages = NULL;
                bl->buf_nr_pages = 0;
                /* make sure it's seen as empty */
                INIT_LIST_HEAD(&bl->buf_list);
                return i;
        }

        /* the head kbuf is the list itself */
        while (!list_empty(&bl->buf_list)) {
                struct io_buffer *nxt;

                nxt = list_first_entry(&bl->buf_list, struct io_buffer, list);
                list_del(&nxt->list);
                if (++i == nbufs)
                        return i;
                cond_resched();
        }
        i++;

        return i;
}

static int io_remove_buffers(struct io_kiocb *req, unsigned int issue_flags)
{
        struct io_provide_buf *p = io_kiocb_to_cmd(req);
        struct io_ring_ctx *ctx = req->ctx;
        struct io_buffer_list *bl;
        int ret = 0;

        io_ring_submit_lock(ctx, issue_flags);

        ret = -ENOENT;
        bl = io_buffer_get_list(ctx, p->bgid);
        if (bl) {
                ret = -EINVAL;
                /* can't use provide/remove buffers command on mapped buffers */
                if (!bl->buf_nr_pages)
                        ret = __io_remove_buffers(ctx, bl, p->nbufs);
        }
        if (ret < 0)
                req_set_fail(req);

        /* complete before unlock, IOPOLL may need the lock */
        io_req_set_res(req, ret, 0);
        __io_req_complete(req, issue_flags);
        io_ring_submit_unlock(ctx, issue_flags);
        return IOU_ISSUE_SKIP_COMPLETE;
}

static int io_provide_buffers_prep(struct io_kiocb *req,
                                   const struct io_uring_sqe *sqe)
{
        unsigned long size, tmp_check;
        struct io_provide_buf *p = io_kiocb_to_cmd(req);
        u64 tmp;

        if (sqe->rw_flags || sqe->splice_fd_in)
                return -EINVAL;

        tmp = READ_ONCE(sqe->fd);
        if (!tmp || tmp > USHRT_MAX)
                return -E2BIG;
        p->nbufs = tmp;
        p->addr = READ_ONCE(sqe->addr);
        p->len = READ_ONCE(sqe->len);

        if (check_mul_overflow((unsigned long)p->len, (unsigned long)p->nbufs,
                                &size))
                return -EOVERFLOW;
        if (check_add_overflow((unsigned long)p->addr, size, &tmp_check))
                return -EOVERFLOW;

        size = (unsigned long)p->len * p->nbufs;
        if (!access_ok(u64_to_user_ptr(p->addr), size))
                return -EFAULT;

        p->bgid = READ_ONCE(sqe->buf_group);
        tmp = READ_ONCE(sqe->off);
        if (tmp > USHRT_MAX)
                return -E2BIG;
        p->bid = tmp;
        return 0;
}

static int io_refill_buffer_cache(struct io_ring_ctx *ctx)
{
        struct io_buffer *buf;
        struct page *page;
        int bufs_in_page;

        /*
         * Completions that don't happen inline (eg not under uring_lock) will
         * add to ->io_buffers_comp. If we don't have any free buffers, check
         * the completion list and splice those entries first.
         */
        if (!list_empty_careful(&ctx->io_buffers_comp)) {
                spin_lock(&ctx->completion_lock);
                if (!list_empty(&ctx->io_buffers_comp)) {
                        list_splice_init(&ctx->io_buffers_comp,
                                                &ctx->io_buffers_cache);
                        spin_unlock(&ctx->completion_lock);
                        return 0;
                }
                spin_unlock(&ctx->completion_lock);
        }

        /*
         * No free buffers and no completion entries either. Allocate a new
         * page worth of buffer entries and add those to our freelist.
         */
        page = alloc_page(GFP_KERNEL_ACCOUNT);
        if (!page)
                return -ENOMEM;

        list_add(&page->lru, &ctx->io_buffers_pages);

        buf = page_address(page);
        bufs_in_page = PAGE_SIZE / sizeof(*buf);
        while (bufs_in_page) {
                list_add_tail(&buf->list, &ctx->io_buffers_cache);
                buf++;
                bufs_in_page--;
        }

        return 0;
}

static int io_add_buffers(struct io_ring_ctx *ctx, struct io_provide_buf *pbuf,
                          struct io_buffer_list *bl)
{
        struct io_buffer *buf;
        u64 addr = pbuf->addr;
        int i, bid = pbuf->bid;

        for (i = 0; i < pbuf->nbufs; i++) {
                if (list_empty(&ctx->io_buffers_cache) &&
                    io_refill_buffer_cache(ctx))
                        break;
                buf = list_first_entry(&ctx->io_buffers_cache, struct io_buffer,
                                        list);
                list_move_tail(&buf->list, &bl->buf_list);
                buf->addr = addr;
                buf->len = min_t(__u32, pbuf->len, MAX_RW_COUNT);
                buf->bid = bid;
                buf->bgid = pbuf->bgid;
                addr += pbuf->len;
                bid++;
                cond_resched();
        }

        return i ? 0 : -ENOMEM;
}

static __cold int io_init_bl_list(struct io_ring_ctx *ctx)
{
        int i;

        ctx->io_bl = kcalloc(BGID_ARRAY, sizeof(struct io_buffer_list),
                                GFP_KERNEL);
        if (!ctx->io_bl)
                return -ENOMEM;

        for (i = 0; i < BGID_ARRAY; i++) {
                INIT_LIST_HEAD(&ctx->io_bl[i].buf_list);
                ctx->io_bl[i].bgid = i;
        }

        return 0;
}

static int io_provide_buffers(struct io_kiocb *req, unsigned int issue_flags)
{
        struct io_provide_buf *p = io_kiocb_to_cmd(req);
        struct io_ring_ctx *ctx = req->ctx;
        struct io_buffer_list *bl;
        int ret = 0;

        io_ring_submit_lock(ctx, issue_flags);

        if (unlikely(p->bgid < BGID_ARRAY && !ctx->io_bl)) {
                ret = io_init_bl_list(ctx);
                if (ret)
                        goto err;
        }

        bl = io_buffer_get_list(ctx, p->bgid);
        if (unlikely(!bl)) {
                bl = kzalloc(sizeof(*bl), GFP_KERNEL);
                if (!bl) {
                        ret = -ENOMEM;
                        goto err;
                }
                INIT_LIST_HEAD(&bl->buf_list);
                ret = io_buffer_add_list(ctx, bl, p->bgid);
                if (ret) {
                        kfree(bl);
                        goto err;
                }
        }
        /* can't add buffers via this command for a mapped buffer ring */
        if (bl->buf_nr_pages) {
                ret = -EINVAL;
                goto err;
        }

        ret = io_add_buffers(ctx, p, bl);
err:
        if (ret < 0)
                req_set_fail(req);
        /* complete before unlock, IOPOLL may need the lock */
        io_req_set_res(req, ret, 0);
        __io_req_complete(req, issue_flags);
        io_ring_submit_unlock(ctx, issue_flags);
        return IOU_ISSUE_SKIP_COMPLETE;
}

static __maybe_unused int io_eopnotsupp_prep(struct io_kiocb *kiocb,
                                             const struct io_uring_sqe *sqe)
{
        return -EOPNOTSUPP;
}

struct io_poll_table {
        struct poll_table_struct pt;
        struct io_kiocb *req;
        int nr_entries;
        int error;
};

#define IO_POLL_CANCEL_FLAG     BIT(31)
#define IO_POLL_REF_MASK        GENMASK(30, 0)

/*
 * If refs part of ->poll_refs (see IO_POLL_REF_MASK) is 0, it's free. We can
 * bump it and acquire ownership. It's disallowed to modify requests while not
 * owning it, that prevents from races for enqueueing task_work's and b/w
 * arming poll and wakeups.
 */
static inline bool io_poll_get_ownership(struct io_kiocb *req)
{
        return !(atomic_fetch_inc(&req->poll_refs) & IO_POLL_REF_MASK);
}

static void io_poll_mark_cancelled(struct io_kiocb *req)
{
        atomic_or(IO_POLL_CANCEL_FLAG, &req->poll_refs);
}

static struct io_poll *io_poll_get_double(struct io_kiocb *req)
{
        /* pure poll stashes this in ->async_data, poll driven retry elsewhere */
        if (req->opcode == IORING_OP_POLL_ADD)
                return req->async_data;
        return req->apoll->double_poll;
}

static struct io_poll *io_poll_get_single(struct io_kiocb *req)
{
        if (req->opcode == IORING_OP_POLL_ADD)
                return io_kiocb_to_cmd(req);
        return &req->apoll->poll;
}

static void io_poll_req_insert(struct io_kiocb *req)
{
        struct io_ring_ctx *ctx = req->ctx;
        struct hlist_head *list;

        list = &ctx->cancel_hash[hash_long(req->cqe.user_data, ctx->cancel_hash_bits)];
        hlist_add_head(&req->hash_node, list);
}

static void io_init_poll_iocb(struct io_poll *poll, __poll_t events,
                              wait_queue_func_t wake_func)
{
        poll->head = NULL;
#define IO_POLL_UNMASK  (EPOLLERR|EPOLLHUP|EPOLLNVAL|EPOLLRDHUP)
        /* mask in events that we always want/need */
        poll->events = events | IO_POLL_UNMASK;
        INIT_LIST_HEAD(&poll->wait.entry);
        init_waitqueue_func_entry(&poll->wait, wake_func);
}

static inline void io_poll_remove_entry(struct io_poll *poll)
{
        struct wait_queue_head *head = smp_load_acquire(&poll->head);

        if (head) {
                spin_lock_irq(&head->lock);
                list_del_init(&poll->wait.entry);
                poll->head = NULL;
                spin_unlock_irq(&head->lock);
        }
}

static void io_poll_remove_entries(struct io_kiocb *req)
{
        /*
         * Nothing to do if neither of those flags are set. Avoid dipping
         * into the poll/apoll/double cachelines if we can.
         */
        if (!(req->flags & (REQ_F_SINGLE_POLL | REQ_F_DOUBLE_POLL)))
                return;

        /*
         * While we hold the waitqueue lock and the waitqueue is nonempty,
         * wake_up_pollfree() will wait for us.  However, taking the waitqueue
         * lock in the first place can race with the waitqueue being freed.
         *
         * We solve this as eventpoll does: by taking advantage of the fact that
         * all users of wake_up_pollfree() will RCU-delay the actual free.  If
         * we enter rcu_read_lock() and see that the pointer to the queue is
         * non-NULL, we can then lock it without the memory being freed out from
         * under us.
         *
         * Keep holding rcu_read_lock() as long as we hold the queue lock, in
         * case the caller deletes the entry from the queue, leaving it empty.
         * In that case, only RCU prevents the queue memory from being freed.
         */
        rcu_read_lock();
        if (req->flags & REQ_F_SINGLE_POLL)
                io_poll_remove_entry(io_poll_get_single(req));
        if (req->flags & REQ_F_DOUBLE_POLL)
                io_poll_remove_entry(io_poll_get_double(req));
        rcu_read_unlock();
}

static int io_issue_sqe(struct io_kiocb *req, unsigned int issue_flags);
/*
 * All poll tw should go through this. Checks for poll events, manages
 * references, does rewait, etc.
 *
 * Returns a negative error on failure. >0 when no action require, which is
 * either spurious wakeup or multishot CQE is served. 0 when it's done with
 * the request, then the mask is stored in req->cqe.res.
 */
static int io_poll_check_events(struct io_kiocb *req, bool *locked)
{
        struct io_ring_ctx *ctx = req->ctx;
        int v, ret;

        /* req->task == current here, checking PF_EXITING is safe */
        if (unlikely(req->task->flags & PF_EXITING))
                return -ECANCELED;

        do {
                v = atomic_read(&req->poll_refs);

                /* tw handler should be the owner, and so have some references */
                if (WARN_ON_ONCE(!(v & IO_POLL_REF_MASK)))
                        return 0;
                if (v & IO_POLL_CANCEL_FLAG)
                        return -ECANCELED;

                if (!req->cqe.res) {
                        struct poll_table_struct pt = { ._key = req->apoll_events };
                        req->cqe.res = vfs_poll(req->file, &pt) & req->apoll_events;
                }

                if ((unlikely(!req->cqe.res)))
                        continue;
                if (req->apoll_events & EPOLLONESHOT)
                        return 0;

                /* multishot, just fill a CQE and proceed */
                if (!(req->flags & REQ_F_APOLL_MULTISHOT)) {
                        __poll_t mask = mangle_poll(req->cqe.res &
                                                    req->apoll_events);
                        bool filled;

                        spin_lock(&ctx->completion_lock);
                        filled = io_fill_cqe_aux(ctx, req->cqe.user_data,
                                                 mask, IORING_CQE_F_MORE);
                        io_commit_cqring(ctx);
                        spin_unlock(&ctx->completion_lock);
                        if (filled) {
                                io_cqring_ev_posted(ctx);
                                continue;
                        }
                        return -ECANCELED;
                }

                io_tw_lock(req->ctx, locked);
                if (unlikely(req->task->flags & PF_EXITING))
                        return -EFAULT;
                ret = io_issue_sqe(req,
                                   IO_URING_F_NONBLOCK|IO_URING_F_COMPLETE_DEFER);
                if (ret)
                        return ret;

                /*
                 * Release all references, retry if someone tried to restart
                 * task_work while we were executing it.
                 */
        } while (atomic_sub_return(v & IO_POLL_REF_MASK, &req->poll_refs));

        return 1;
}

static void io_poll_task_func(struct io_kiocb *req, bool *locked)
{
        struct io_ring_ctx *ctx = req->ctx;
        int ret;

        ret = io_poll_check_events(req, locked);
        if (ret > 0)
                return;

        if (!ret) {
                struct io_poll *poll = io_kiocb_to_cmd(req);

                req->cqe.res = mangle_poll(req->cqe.res & poll->events);
        } else {
                req->cqe.res = ret;
                req_set_fail(req);
        }

        io_poll_remove_entries(req);
        spin_lock(&ctx->completion_lock);
        hash_del(&req->hash_node);
        req->cqe.flags = 0;
        __io_req_complete_post(req);
        io_commit_cqring(ctx);
        spin_unlock(&ctx->completion_lock);
        io_cqring_ev_posted(ctx);
}

static void io_apoll_task_func(struct io_kiocb *req, bool *locked)
{
        struct io_ring_ctx *ctx = req->ctx;
        int ret;

        ret = io_poll_check_events(req, locked);
        if (ret > 0)
                return;

        io_poll_remove_entries(req);
        spin_lock(&ctx->completion_lock);
        hash_del(&req->hash_node);
        spin_unlock(&ctx->completion_lock);

        if (!ret)
                io_req_task_submit(req, locked);
        else
                io_req_complete_failed(req, ret);
}

static void __io_poll_execute(struct io_kiocb *req, int mask,
                              __poll_t __maybe_unused events)
{
        io_req_set_res(req, mask, 0);
        /*
         * This is useful for poll that is armed on behalf of another
         * request, and where the wakeup path could be on a different
         * CPU. We want to avoid pulling in req->apoll->events for that
         * case.
         */
        if (req->opcode == IORING_OP_POLL_ADD)
                req->io_task_work.func = io_poll_task_func;
        else
                req->io_task_work.func = io_apoll_task_func;

        trace_io_uring_task_add(req->ctx, req, req->cqe.user_data, req->opcode, mask);
        io_req_task_work_add(req);
}

static inline void io_poll_execute(struct io_kiocb *req, int res,
                __poll_t events)
{
        if (io_poll_get_ownership(req))
                __io_poll_execute(req, res, events);
}

static void io_poll_cancel_req(struct io_kiocb *req)
{
        io_poll_mark_cancelled(req);
        /* kick tw, which should complete the request */
        io_poll_execute(req, 0, 0);
}

#define wqe_to_req(wait)        ((void *)((unsigned long) (wait)->private & ~1))
#define wqe_is_double(wait)     ((unsigned long) (wait)->private & 1)
#define IO_ASYNC_POLL_COMMON    (EPOLLONESHOT | EPOLLPRI)

static int io_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync,
                        void *key)
{
        struct io_kiocb *req = wqe_to_req(wait);
        struct io_poll *poll = container_of(wait, struct io_poll, wait);
        __poll_t mask = key_to_poll(key);

        if (unlikely(mask & POLLFREE)) {
                io_poll_mark_cancelled(req);
                /* we have to kick tw in case it's not already */
                io_poll_execute(req, 0, poll->events);

                /*
                 * If the waitqueue is being freed early but someone is already
                 * holds ownership over it, we have to tear down the request as
                 * best we can. That means immediately removing the request from
                 * its waitqueue and preventing all further accesses to the
                 * waitqueue via the request.
                 */
                list_del_init(&poll->wait.entry);

                /*
                 * Careful: this *must* be the last step, since as soon
                 * as req->head is NULL'ed out, the request can be
                 * completed and freed, since aio_poll_complete_work()
                 * will no longer need to take the waitqueue lock.
                 */
                smp_store_release(&poll->head, NULL);
                return 1;
        }

        /* for instances that support it check for an event match first */
        if (mask && !(mask & (poll->events & ~IO_ASYNC_POLL_COMMON)))
                return 0;

        if (io_poll_get_ownership(req)) {
                /* optional, saves extra locking for removal in tw handler */
                if (mask && poll->events & EPOLLONESHOT) {
                        list_del_init(&poll->wait.entry);
                        poll->head = NULL;
                        if (wqe_is_double(wait))
                                req->flags &= ~REQ_F_DOUBLE_POLL;
                        else
                                req->flags &= ~REQ_F_SINGLE_POLL;
                }
                __io_poll_execute(req, mask, poll->events);
        }
        return 1;
}

static void __io_queue_proc(struct io_poll *poll, struct io_poll_table *pt,
                            struct wait_queue_head *head,
                            struct io_poll **poll_ptr)
{
        struct io_kiocb *req = pt->req;
        unsigned long wqe_private = (unsigned long) req;

        /*
         * The file being polled uses multiple waitqueues for poll handling
         * (e.g. one for read, one for write). Setup a separate io_poll
         * if this happens.
         */
        if (unlikely(pt->nr_entries)) {
                struct io_poll *first = poll;

                /* double add on the same waitqueue head, ignore */
                if (first->head == head)
                        return;
                /* already have a 2nd entry, fail a third attempt */
                if (*poll_ptr) {
                        if ((*poll_ptr)->head == head)
                                return;
                        pt->error = -EINVAL;
                        return;
                }

                poll = kmalloc(sizeof(*poll), GFP_ATOMIC);
                if (!poll) {
                        pt->error = -ENOMEM;
                        return;
                }
                /* mark as double wq entry */
                wqe_private |= 1;
                req->flags |= REQ_F_DOUBLE_POLL;
                io_init_poll_iocb(poll, first->events, first->wait.func);
                *poll_ptr = poll;
                if (req->opcode == IORING_OP_POLL_ADD)
                        req->flags |= REQ_F_ASYNC_DATA;
        }

        req->flags |= REQ_F_SINGLE_POLL;
        pt->nr_entries++;
        poll->head = head;
        poll->wait.private = (void *) wqe_private;

        if (poll->events & EPOLLEXCLUSIVE)
                add_wait_queue_exclusive(head, &poll->wait);
        else
                add_wait_queue(head, &poll->wait);
}

static void io_poll_queue_proc(struct file *file, struct wait_queue_head *head,
                               struct poll_table_struct *p)
{
        struct io_poll_table *pt = container_of(p, struct io_poll_table, pt);
        struct io_poll *poll = io_kiocb_to_cmd(pt->req);

        __io_queue_proc(poll, pt, head,
                        (struct io_poll **) &pt->req->async_data);
}

static int __io_arm_poll_handler(struct io_kiocb *req,
                                 struct io_poll *poll,
                                 struct io_poll_table *ipt, __poll_t mask)
{
        struct io_ring_ctx *ctx = req->ctx;
        int v;

        INIT_HLIST_NODE(&req->hash_node);
        req->work.cancel_seq = atomic_read(&ctx->cancel_seq);
        io_init_poll_iocb(poll, mask, io_poll_wake);
        poll->file = req->file;

        req->apoll_events = poll->events;

        ipt->pt._key = mask;
        ipt->req = req;
        ipt->error = 0;
        ipt->nr_entries = 0;

        /*
         * Take the ownership to delay any tw execution up until we're done
         * with poll arming. see io_poll_get_ownership().
         */
        atomic_set(&req->poll_refs, 1);
        mask = vfs_poll(req->file, &ipt->pt) & poll->events;

        if (mask && (poll->events & EPOLLONESHOT)) {
                io_poll_remove_entries(req);
                /* no one else has access to the req, forget about the ref */
                return mask;
        }
        if (!mask && unlikely(ipt->error || !ipt->nr_entries)) {
                io_poll_remove_entries(req);
                if (!ipt->error)
                        ipt->error = -EINVAL;
                return 0;
        }

        spin_lock(&ctx->completion_lock);
        io_poll_req_insert(req);
        spin_unlock(&ctx->completion_lock);

        if (mask) {
                /* can't multishot if failed, just queue the event we've got */
                if (unlikely(ipt->error || !ipt->nr_entries)) {
                        poll->events |= EPOLLONESHOT;
                        req->apoll_events |= EPOLLONESHOT;
                        ipt->error = 0;
                }
                __io_poll_execute(req, mask, poll->events);
                return 0;
        }

        /*
         * Release ownership. If someone tried to queue a tw while it was
         * locked, kick it off for them.
         */
        v = atomic_dec_return(&req->poll_refs);
        if (unlikely(v & IO_POLL_REF_MASK))
                __io_poll_execute(req, 0, poll->events);
        return 0;
}

static void io_async_queue_proc(struct file *file, struct wait_queue_head *head,
                               struct poll_table_struct *p)
{
        struct io_poll_table *pt = container_of(p, struct io_poll_table, pt);
        struct async_poll *apoll = pt->req->apoll;

        __io_queue_proc(&apoll->poll, pt, head, &apoll->double_poll);
}

enum {
        IO_APOLL_OK,
        IO_APOLL_ABORTED,
        IO_APOLL_READY
};

static int io_arm_poll_handler(struct io_kiocb *req, unsigned issue_flags)
{
        const struct io_op_def *def = &io_op_defs[req->opcode];
        struct io_ring_ctx *ctx = req->ctx;
        struct async_poll *apoll;
        struct io_poll_table ipt;
        __poll_t mask = POLLPRI | POLLERR;
        int ret;

        if (!def->pollin && !def->pollout)
                return IO_APOLL_ABORTED;
        if (!file_can_poll(req->file))
                return IO_APOLL_ABORTED;
        if ((req->flags & (REQ_F_POLLED|REQ_F_PARTIAL_IO)) == REQ_F_POLLED)
                return IO_APOLL_ABORTED;
        if (!(req->flags & REQ_F_APOLL_MULTISHOT))
                mask |= EPOLLONESHOT;

        if (def->pollin) {
                mask |= EPOLLIN | EPOLLRDNORM;

                /* If reading from MSG_ERRQUEUE using recvmsg, ignore POLLIN */
                if (req->flags & REQ_F_CLEAR_POLLIN)
                        mask &= ~EPOLLIN;
        } else {
                mask |= EPOLLOUT | EPOLLWRNORM;
        }
        if (def->poll_exclusive)
                mask |= EPOLLEXCLUSIVE;
        if (req->flags & REQ_F_POLLED) {
                apoll = req->apoll;
                kfree(apoll->double_poll);
        } else if (!(issue_flags & IO_URING_F_UNLOCKED) &&
                   !list_empty(&ctx->apoll_cache)) {
                apoll = list_first_entry(&ctx->apoll_cache, struct async_poll,
                                                poll.wait.entry);
                list_del_init(&apoll->poll.wait.entry);
        } else {
                apoll = kmalloc(sizeof(*apoll), GFP_ATOMIC);
                if (unlikely(!apoll))
                        return IO_APOLL_ABORTED;
        }
        apoll->double_poll = NULL;
        req->apoll = apoll;
        req->flags |= REQ_F_POLLED;
        ipt.pt._qproc = io_async_queue_proc;

        io_kbuf_recycle(req, issue_flags);

        ret = __io_arm_poll_handler(req, &apoll->poll, &ipt, mask);
        if (ret || ipt.error)
                return ret ? IO_APOLL_READY : IO_APOLL_ABORTED;

        trace_io_uring_poll_arm(ctx, req, req->cqe.user_data, req->opcode,
                                mask, apoll->poll.events);
        return IO_APOLL_OK;
}

/*
 * Returns true if we found and killed one or more poll requests
 */
static __cold bool io_poll_remove_all(struct io_ring_ctx *ctx,
                                      struct task_struct *tsk, bool cancel_all)
{
        struct hlist_node *tmp;
        struct io_kiocb *req;
        bool found = false;
        int i;

        spin_lock(&ctx->completion_lock);
        for (i = 0; i < (1U << ctx->cancel_hash_bits); i++) {
                struct hlist_head *list;

                list = &ctx->cancel_hash[i];
                hlist_for_each_entry_safe(req, tmp, list, hash_node) {
                        if (io_match_task_safe(req, tsk, cancel_all)) {
                                hlist_del_init(&req->hash_node);
                                io_poll_cancel_req(req);
                                found = true;
                        }
                }
        }
        spin_unlock(&ctx->completion_lock);
        return found;
}

static struct io_kiocb *io_poll_find(struct io_ring_ctx *ctx, bool poll_only,
                                     struct io_cancel_data *cd)
        __must_hold(&ctx->completion_lock)
{
        struct hlist_head *list;
        struct io_kiocb *req;

        list = &ctx->cancel_hash[hash_long(cd->data, ctx->cancel_hash_bits)];
        hlist_for_each_entry(req, list, hash_node) {
                if (cd->data != req->cqe.user_data)
                        continue;
                if (poll_only && req->opcode != IORING_OP_POLL_ADD)
                        continue;
                if (cd->flags & IORING_ASYNC_CANCEL_ALL) {
                        if (cd->seq == req->work.cancel_seq)
                                continue;
                        req->work.cancel_seq = cd->seq;
                }
                return req;
        }
        return NULL;
}

static struct io_kiocb *io_poll_file_find(struct io_ring_ctx *ctx,
                                          struct io_cancel_data *cd)
        __must_hold(&ctx->completion_lock)
{
        struct io_kiocb *req;
        int i;

        for (i = 0; i < (1U << ctx->cancel_hash_bits); i++) {
                struct hlist_head *list;

                list = &ctx->cancel_hash[i];
                hlist_for_each_entry(req, list, hash_node) {
                        if (!(cd->flags & IORING_ASYNC_CANCEL_ANY) &&
                            req->file != cd->file)
                                continue;
                        if (cd->seq == req->work.cancel_seq)
                                continue;
                        req->work.cancel_seq = cd->seq;
                        return req;
                }
        }
        return NULL;
}

static bool io_poll_disarm(struct io_kiocb *req)
        __must_hold(&ctx->completion_lock)
{
        if (!io_poll_get_ownership(req))
                return false;
        io_poll_remove_entries(req);
        hash_del(&req->hash_node);
        return true;
}

static int io_poll_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd)
        __must_hold(&ctx->completion_lock)
{
        struct io_kiocb *req;

        if (cd->flags & (IORING_ASYNC_CANCEL_FD|IORING_ASYNC_CANCEL_ANY))
                req = io_poll_file_find(ctx, cd);
        else
                req = io_poll_find(ctx, false, cd);
        if (!req)
                return -ENOENT;
        io_poll_cancel_req(req);
        return 0;
}

static __poll_t io_poll_parse_events(const struct io_uring_sqe *sqe,
                                     unsigned int flags)
{
        u32 events;

        events = READ_ONCE(sqe->poll32_events);
#ifdef __BIG_ENDIAN
        events = swahw32(events);
#endif
        if (!(flags & IORING_POLL_ADD_MULTI))
                events |= EPOLLONESHOT;
        return demangle_poll(events) | (events & (EPOLLEXCLUSIVE|EPOLLONESHOT));
}

static int io_poll_remove_prep(struct io_kiocb *req,
                               const struct io_uring_sqe *sqe)
{
        struct io_poll_update *upd = io_kiocb_to_cmd(req);
        u32 flags;

        if (sqe->buf_index || sqe->splice_fd_in)
                return -EINVAL;
        flags = READ_ONCE(sqe->len);
        if (flags & ~(IORING_POLL_UPDATE_EVENTS | IORING_POLL_UPDATE_USER_DATA |
                      IORING_POLL_ADD_MULTI))
                return -EINVAL;
        /* meaningless without update */
        if (flags == IORING_POLL_ADD_MULTI)
                return -EINVAL;

        upd->old_user_data = READ_ONCE(sqe->addr);
        upd->update_events = flags & IORING_POLL_UPDATE_EVENTS;
        upd->update_user_data = flags & IORING_POLL_UPDATE_USER_DATA;

        upd->new_user_data = READ_ONCE(sqe->off);
        if (!upd->update_user_data && upd->new_user_data)
                return -EINVAL;
        if (upd->update_events)
                upd->events = io_poll_parse_events(sqe, flags);
        else if (sqe->poll32_events)
                return -EINVAL;

        return 0;
}

static int io_poll_add_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        struct io_poll *poll = io_kiocb_to_cmd(req);
        u32 flags;

        if (sqe->buf_index || sqe->off || sqe->addr)
                return -EINVAL;
        flags = READ_ONCE(sqe->len);
        if (flags & ~IORING_POLL_ADD_MULTI)
                return -EINVAL;
        if ((flags & IORING_POLL_ADD_MULTI) && (req->flags & REQ_F_CQE_SKIP))
                return -EINVAL;

        io_req_set_refcount(req);
        poll->events = io_poll_parse_events(sqe, flags);
        return 0;
}

static int io_poll_add(struct io_kiocb *req, unsigned int issue_flags)
{
        struct io_poll *poll = io_kiocb_to_cmd(req);
        struct io_poll_table ipt;
        int ret;

        ipt.pt._qproc = io_poll_queue_proc;

        ret = __io_arm_poll_handler(req, poll, &ipt, poll->events);
        if (ret) {
                io_req_set_res(req, ret, 0);
                return IOU_OK;
        }
        if (ipt.error) {
                req_set_fail(req);
                return ipt.error;
        }

        return IOU_ISSUE_SKIP_COMPLETE;
}

static int io_poll_remove(struct io_kiocb *req, unsigned int issue_flags)
{
        struct io_poll_update *poll_update = io_kiocb_to_cmd(req);
        struct io_cancel_data cd = { .data = poll_update->old_user_data, };
        struct io_ring_ctx *ctx = req->ctx;
        struct io_kiocb *preq;
        int ret2, ret = 0;
        bool locked;

        spin_lock(&ctx->completion_lock);
        preq = io_poll_find(ctx, true, &cd);
        if (!preq || !io_poll_disarm(preq)) {
                spin_unlock(&ctx->completion_lock);
                ret = preq ? -EALREADY : -ENOENT;
                goto out;
        }
        spin_unlock(&ctx->completion_lock);

        if (poll_update->update_events || poll_update->update_user_data) {
                /* only mask one event flags, keep behavior flags */
                if (poll_update->update_events) {
                        struct io_poll *poll = io_kiocb_to_cmd(preq);

                        poll->events &= ~0xffff;
                        poll->events |= poll_update->events & 0xffff;
                        poll->events |= IO_POLL_UNMASK;
                }
                if (poll_update->update_user_data)
                        preq->cqe.user_data = poll_update->new_user_data;

                ret2 = io_poll_add(preq, issue_flags);
                /* successfully updated, don't complete poll request */
                if (!ret2 || ret2 == -EIOCBQUEUED)
                        goto out;
        }

        req_set_fail(preq);
        io_req_set_res(preq, -ECANCELED, 0);
        locked = !(issue_flags & IO_URING_F_UNLOCKED);
        io_req_task_complete(preq, &locked);
out:
        if (ret < 0) {
                req_set_fail(req);
                return ret;
        }
        /* complete update request, we're done with it */
        io_req_set_res(req, ret, 0);
        return IOU_OK;
}

static bool io_cancel_cb(struct io_wq_work *work, void *data)
{
        struct io_kiocb *req = container_of(work, struct io_kiocb, work);
        struct io_cancel_data *cd = data;

        if (req->ctx != cd->ctx)
                return false;
        if (cd->flags & IORING_ASYNC_CANCEL_ANY) {
                ;
        } else if (cd->flags & IORING_ASYNC_CANCEL_FD) {
                if (req->file != cd->file)
                        return false;
        } else {
                if (req->cqe.user_data != cd->data)
                        return false;
        }
        if (cd->flags & (IORING_ASYNC_CANCEL_ALL|IORING_ASYNC_CANCEL_ANY)) {
                if (cd->seq == req->work.cancel_seq)
                        return false;
                req->work.cancel_seq = cd->seq;
        }
        return true;
}

static int io_async_cancel_one(struct io_uring_task *tctx,
                               struct io_cancel_data *cd)
{
        enum io_wq_cancel cancel_ret;
        int ret = 0;
        bool all;

        if (!tctx || !tctx->io_wq)
                return -ENOENT;

        all = cd->flags & (IORING_ASYNC_CANCEL_ALL|IORING_ASYNC_CANCEL_ANY);
        cancel_ret = io_wq_cancel_cb(tctx->io_wq, io_cancel_cb, cd, all);
        switch (cancel_ret) {
        case IO_WQ_CANCEL_OK:
                ret = 0;
                break;
        case IO_WQ_CANCEL_RUNNING:
                ret = -EALREADY;
                break;
        case IO_WQ_CANCEL_NOTFOUND:
                ret = -ENOENT;
                break;
        }

        return ret;
}

int io_try_cancel(struct io_kiocb *req, struct io_cancel_data *cd)
{
        struct io_ring_ctx *ctx = req->ctx;
        int ret;

        WARN_ON_ONCE(!io_wq_current_is_worker() && req->task != current);

        ret = io_async_cancel_one(req->task->io_uring, cd);
        /*
         * Fall-through even for -EALREADY, as we may have poll armed
         * that need unarming.
         */
        if (!ret)
                return 0;

        spin_lock(&ctx->completion_lock);
        ret = io_poll_cancel(ctx, cd);
        if (ret != -ENOENT)
                goto out;
        if (!(cd->flags & IORING_ASYNC_CANCEL_FD))
                ret = io_timeout_cancel(ctx, cd);
out:
        spin_unlock(&ctx->completion_lock);
        return ret;
}

#define CANCEL_FLAGS    (IORING_ASYNC_CANCEL_ALL | IORING_ASYNC_CANCEL_FD | \
                         IORING_ASYNC_CANCEL_ANY)

static int io_async_cancel_prep(struct io_kiocb *req,
                                const struct io_uring_sqe *sqe)
{
        struct io_cancel *cancel = io_kiocb_to_cmd(req);

        if (unlikely(req->flags & REQ_F_BUFFER_SELECT))
                return -EINVAL;
        if (sqe->off || sqe->len || sqe->splice_fd_in)
                return -EINVAL;

        cancel->addr = READ_ONCE(sqe->addr);
        cancel->flags = READ_ONCE(sqe->cancel_flags);
        if (cancel->flags & ~CANCEL_FLAGS)
                return -EINVAL;
        if (cancel->flags & IORING_ASYNC_CANCEL_FD) {
                if (cancel->flags & IORING_ASYNC_CANCEL_ANY)
                        return -EINVAL;
                cancel->fd = READ_ONCE(sqe->fd);
        }

        return 0;
}

static int __io_async_cancel(struct io_cancel_data *cd, struct io_kiocb *req,
                             unsigned int issue_flags)
{
        bool all = cd->flags & (IORING_ASYNC_CANCEL_ALL|IORING_ASYNC_CANCEL_ANY);
        struct io_ring_ctx *ctx = cd->ctx;
        struct io_tctx_node *node;
        int ret, nr = 0;

        do {
                ret = io_try_cancel(req, cd);
                if (ret == -ENOENT)
                        break;
                if (!all)
                        return ret;
                nr++;
        } while (1);

        /* slow path, try all io-wq's */
        io_ring_submit_lock(ctx, issue_flags);
        ret = -ENOENT;
        list_for_each_entry(node, &ctx->tctx_list, ctx_node) {
                struct io_uring_task *tctx = node->task->io_uring;

                ret = io_async_cancel_one(tctx, cd);
                if (ret != -ENOENT) {
                        if (!all)
                                break;
                        nr++;
                }
        }
        io_ring_submit_unlock(ctx, issue_flags);
        return all ? nr : ret;
}

static int io_async_cancel(struct io_kiocb *req, unsigned int issue_flags)
{
        struct io_cancel *cancel = io_kiocb_to_cmd(req);
        struct io_cancel_data cd = {
                .ctx    = req->ctx,
                .data   = cancel->addr,
                .flags  = cancel->flags,
                .seq    = atomic_inc_return(&req->ctx->cancel_seq),
        };
        int ret;

        if (cd.flags & IORING_ASYNC_CANCEL_FD) {
                if (req->flags & REQ_F_FIXED_FILE)
                        req->file = io_file_get_fixed(req, cancel->fd,
                                                        issue_flags);
                else
                        req->file = io_file_get_normal(req, cancel->fd);
                if (!req->file) {
                        ret = -EBADF;
                        goto done;
                }
                cd.file = req->file;
        }

        ret = __io_async_cancel(&cd, req, issue_flags);
done:
        if (ret < 0)
                req_set_fail(req);
        io_req_set_res(req, ret, 0);
        return IOU_OK;
}

static int io_files_update_prep(struct io_kiocb *req,
                                const struct io_uring_sqe *sqe)
{
        struct io_rsrc_update *up = io_kiocb_to_cmd(req);

        if (unlikely(req->flags & (REQ_F_FIXED_FILE | REQ_F_BUFFER_SELECT)))
                return -EINVAL;
        if (sqe->rw_flags || sqe->splice_fd_in)
                return -EINVAL;

        up->offset = READ_ONCE(sqe->off);
        up->nr_args = READ_ONCE(sqe->len);
        if (!up->nr_args)
                return -EINVAL;
        up->arg = READ_ONCE(sqe->addr);
        return 0;
}

static int io_files_update_with_index_alloc(struct io_kiocb *req,
                                            unsigned int issue_flags)
{
        struct io_rsrc_update *up = io_kiocb_to_cmd(req);
        __s32 __user *fds = u64_to_user_ptr(up->arg);
        unsigned int done;
        struct file *file;
        int ret, fd;

        if (!req->ctx->file_data)
                return -ENXIO;

        for (done = 0; done < up->nr_args; done++) {
                if (copy_from_user(&fd, &fds[done], sizeof(fd))) {
                        ret = -EFAULT;
                        break;
                }

                file = fget(fd);
                if (!file) {
                        ret = -EBADF;
                        break;
                }
                ret = io_fixed_fd_install(req, issue_flags, file,
                                          IORING_FILE_INDEX_ALLOC);
                if (ret < 0)
                        break;
                if (copy_to_user(&fds[done], &ret, sizeof(ret))) {
                        __io_close_fixed(req, issue_flags, ret);
                        ret = -EFAULT;
                        break;
                }
        }

        if (done)
                return done;
        return ret;
}

static int io_files_update(struct io_kiocb *req, unsigned int issue_flags)
{
        struct io_rsrc_update *up = io_kiocb_to_cmd(req);
        struct io_ring_ctx *ctx = req->ctx;
        struct io_uring_rsrc_update2 up2;
        int ret;

        up2.offset = up->offset;
        up2.data = up->arg;
        up2.nr = 0;
        up2.tags = 0;
        up2.resv = 0;
        up2.resv2 = 0;

        if (up->offset == IORING_FILE_INDEX_ALLOC) {
                ret = io_files_update_with_index_alloc(req, issue_flags);
        } else {
                io_ring_submit_lock(ctx, issue_flags);
                ret = __io_register_rsrc_update(ctx, IORING_RSRC_FILE,
                                                &up2, up->nr_args);
                io_ring_submit_unlock(ctx, issue_flags);
        }

        if (ret < 0)
                req_set_fail(req);
        io_req_set_res(req, ret, 0);
        return IOU_OK;
}

static int io_req_prep_async(struct io_kiocb *req)
{
        const struct io_op_def *def = &io_op_defs[req->opcode];

        /* assign early for deferred execution for non-fixed file */
        if (def->needs_file && !(req->flags & REQ_F_FIXED_FILE))
                req->file = io_file_get_normal(req, req->cqe.fd);
        if (!def->prep_async)
                return 0;
        if (WARN_ON_ONCE(req_has_async_data(req)))
                return -EFAULT;
        if (io_alloc_async_data(req))
                return -EAGAIN;

        return def->prep_async(req);
}

static u32 io_get_sequence(struct io_kiocb *req)
{
        u32 seq = req->ctx->cached_sq_head;
        struct io_kiocb *cur;

        /* need original cached_sq_head, but it was increased for each req */
        io_for_each_link(cur, req)
                seq--;
        return seq;
}

static __cold void io_drain_req(struct io_kiocb *req)
{
        struct io_ring_ctx *ctx = req->ctx;
        struct io_defer_entry *de;
        int ret;
        u32 seq = io_get_sequence(req);

        /* Still need defer if there is pending req in defer list. */
        spin_lock(&ctx->completion_lock);
        if (!req_need_defer(req, seq) && list_empty_careful(&ctx->defer_list)) {
                spin_unlock(&ctx->completion_lock);
queue:
                ctx->drain_active = false;
                io_req_task_queue(req);
                return;
        }
        spin_unlock(&ctx->completion_lock);

        ret = io_req_prep_async(req);
        if (ret) {
fail:
                io_req_complete_failed(req, ret);
                return;
        }
        io_prep_async_link(req);
        de = kmalloc(sizeof(*de), GFP_KERNEL);
        if (!de) {
                ret = -ENOMEM;
                goto fail;
        }

        spin_lock(&ctx->completion_lock);
        if (!req_need_defer(req, seq) && list_empty(&ctx->defer_list)) {
                spin_unlock(&ctx->completion_lock);
                kfree(de);
                goto queue;
        }

        trace_io_uring_defer(ctx, req, req->cqe.user_data, req->opcode);
        de->req = req;
        de->seq = seq;
        list_add_tail(&de->list, &ctx->defer_list);
        spin_unlock(&ctx->completion_lock);
}

static void io_clean_op(struct io_kiocb *req)
{
        if (req->flags & REQ_F_BUFFER_SELECTED) {
                spin_lock(&req->ctx->completion_lock);
                io_put_kbuf_comp(req);
                spin_unlock(&req->ctx->completion_lock);
        }

        if (req->flags & REQ_F_NEED_CLEANUP) {
                const struct io_op_def *def = &io_op_defs[req->opcode];

                if (def->cleanup)
                        def->cleanup(req);
        }
        if ((req->flags & REQ_F_POLLED) && req->apoll) {
                kfree(req->apoll->double_poll);
                kfree(req->apoll);
                req->apoll = NULL;
        }
        if (req->flags & REQ_F_INFLIGHT) {
                struct io_uring_task *tctx = req->task->io_uring;

                atomic_dec(&tctx->inflight_tracked);
        }
        if (req->flags & REQ_F_CREDS)
                put_cred(req->creds);
        if (req->flags & REQ_F_ASYNC_DATA) {
                kfree(req->async_data);
                req->async_data = NULL;
        }
        req->flags &= ~IO_REQ_CLEAN_FLAGS;
}

static bool io_assign_file(struct io_kiocb *req, unsigned int issue_flags)
{
        if (req->file || !io_op_defs[req->opcode].needs_file)
                return true;

        if (req->flags & REQ_F_FIXED_FILE)
                req->file = io_file_get_fixed(req, req->cqe.fd, issue_flags);
        else
                req->file = io_file_get_normal(req, req->cqe.fd);

        return !!req->file;
}

static int io_issue_sqe(struct io_kiocb *req, unsigned int issue_flags)
{
        const struct io_op_def *def = &io_op_defs[req->opcode];
        const struct cred *creds = NULL;
        int ret;

        if (unlikely(!io_assign_file(req, issue_flags)))
                return -EBADF;

        if (unlikely((req->flags & REQ_F_CREDS) && req->creds != current_cred()))
                creds = override_creds(req->creds);

        if (!def->audit_skip)
                audit_uring_entry(req->opcode);

        ret = def->issue(req, issue_flags);

        if (!def->audit_skip)
                audit_uring_exit(!ret, ret);

        if (creds)
                revert_creds(creds);

        if (ret == IOU_OK)
                __io_req_complete(req, issue_flags);
        else if (ret != IOU_ISSUE_SKIP_COMPLETE)
                return ret;

        /* If the op doesn't have a file, we're not polling for it */
        if ((req->ctx->flags & IORING_SETUP_IOPOLL) && req->file)
                io_iopoll_req_issued(req, issue_flags);

        return 0;
}

static struct io_wq_work *io_wq_free_work(struct io_wq_work *work)
{
        struct io_kiocb *req = container_of(work, struct io_kiocb, work);

        req = io_put_req_find_next(req);
        return req ? &req->work : NULL;
}

static void io_wq_submit_work(struct io_wq_work *work)
{
        struct io_kiocb *req = container_of(work, struct io_kiocb, work);
        const struct io_op_def *def = &io_op_defs[req->opcode];
        unsigned int issue_flags = IO_URING_F_UNLOCKED;
        bool needs_poll = false;
        int ret = 0, err = -ECANCELED;

        /* one will be dropped by ->io_free_work() after returning to io-wq */
        if (!(req->flags & REQ_F_REFCOUNT))
                __io_req_set_refcount(req, 2);
        else
                req_ref_get(req);

        io_arm_ltimeout(req);

        /* either cancelled or io-wq is dying, so don't touch tctx->iowq */
        if (work->flags & IO_WQ_WORK_CANCEL) {
fail:
                io_req_task_queue_fail(req, err);
                return;
        }
        if (!io_assign_file(req, issue_flags)) {
                err = -EBADF;
                work->flags |= IO_WQ_WORK_CANCEL;
                goto fail;
        }

        if (req->flags & REQ_F_FORCE_ASYNC) {
                bool opcode_poll = def->pollin || def->pollout;

                if (opcode_poll && file_can_poll(req->file)) {
                        needs_poll = true;
                        issue_flags |= IO_URING_F_NONBLOCK;
                }
        }

        do {
                ret = io_issue_sqe(req, issue_flags);
                if (ret != -EAGAIN)
                        break;
                /*
                 * We can get EAGAIN for iopolled IO even though we're
                 * forcing a sync submission from here, since we can't
                 * wait for request slots on the block side.
                 */
                if (!needs_poll) {
                        if (!(req->ctx->flags & IORING_SETUP_IOPOLL))
                                break;
                        cond_resched();
                        continue;
                }

                if (io_arm_poll_handler(req, issue_flags) == IO_APOLL_OK)
                        return;
                /* aborted or ready, in either case retry blocking */
                needs_poll = false;
                issue_flags &= ~IO_URING_F_NONBLOCK;
        } while (1);

        /* avoid locking problems by failing it from a clean context */
        if (ret < 0)
                io_req_task_queue_fail(req, ret);
}

static inline struct file *io_file_from_index(struct io_ring_ctx *ctx,
                                              int index)
{
        struct io_fixed_file *slot = io_fixed_file_slot(&ctx->file_table, index);

        return (struct file *) (slot->file_ptr & FFS_MASK);
}

static void io_fixed_file_set(struct io_fixed_file *file_slot, struct file *file)
{
        unsigned long file_ptr = (unsigned long) file;

        file_ptr |= io_file_get_flags(file);
        file_slot->file_ptr = file_ptr;
}

inline struct file *io_file_get_fixed(struct io_kiocb *req, int fd,
                                      unsigned int issue_flags)
{
        struct io_ring_ctx *ctx = req->ctx;
        struct file *file = NULL;
        unsigned long file_ptr;

        io_ring_submit_lock(ctx, issue_flags);

        if (unlikely((unsigned int)fd >= ctx->nr_user_files))
                goto out;
        fd = array_index_nospec(fd, ctx->nr_user_files);
        file_ptr = io_fixed_file_slot(&ctx->file_table, fd)->file_ptr;
        file = (struct file *) (file_ptr & FFS_MASK);
        file_ptr &= ~FFS_MASK;
        /* mask in overlapping REQ_F and FFS bits */
        req->flags |= (file_ptr << REQ_F_SUPPORT_NOWAIT_BIT);
        io_req_set_rsrc_node(req, ctx, 0);
        WARN_ON_ONCE(file && !test_bit(fd, ctx->file_table.bitmap));
out:
        io_ring_submit_unlock(ctx, issue_flags);
        return file;
}

struct file *io_file_get_normal(struct io_kiocb *req, int fd)
{
        struct file *file = fget(fd);

        trace_io_uring_file_get(req->ctx, req, req->cqe.user_data, fd);

        /* we don't allow fixed io_uring files */
        if (file && file->f_op == &io_uring_fops)
                io_req_track_inflight(req);
        return file;
}

static void io_queue_async(struct io_kiocb *req, int ret)
        __must_hold(&req->ctx->uring_lock)
{
        struct io_kiocb *linked_timeout;

        if (ret != -EAGAIN || (req->flags & REQ_F_NOWAIT)) {
                io_req_complete_failed(req, ret);
                return;
        }

        linked_timeout = io_prep_linked_timeout(req);

        switch (io_arm_poll_handler(req, 0)) {
        case IO_APOLL_READY:
                io_req_task_queue(req);
                break;
        case IO_APOLL_ABORTED:
                /*
                 * Queued up for async execution, worker will release
                 * submit reference when the iocb is actually submitted.
                 */
                io_kbuf_recycle(req, 0);
                io_queue_iowq(req, NULL);
                break;
        case IO_APOLL_OK:
                break;
        }

        if (linked_timeout)
                io_queue_linked_timeout(linked_timeout);
}

static inline void io_queue_sqe(struct io_kiocb *req)
        __must_hold(&req->ctx->uring_lock)
{
        int ret;

        ret = io_issue_sqe(req, IO_URING_F_NONBLOCK|IO_URING_F_COMPLETE_DEFER);

        if (req->flags & REQ_F_COMPLETE_INLINE) {
                io_req_add_compl_list(req);
                return;
        }
        /*
         * We async punt it if the file wasn't marked NOWAIT, or if the file
         * doesn't support non-blocking read/write attempts
         */
        if (likely(!ret))
                io_arm_ltimeout(req);
        else
                io_queue_async(req, ret);
}

static void io_queue_sqe_fallback(struct io_kiocb *req)
        __must_hold(&req->ctx->uring_lock)
{
        if (unlikely(req->flags & REQ_F_FAIL)) {
                /*
                 * We don't submit, fail them all, for that replace hardlinks
                 * with normal links. Extra REQ_F_LINK is tolerated.
                 */
                req->flags &= ~REQ_F_HARDLINK;
                req->flags |= REQ_F_LINK;
                io_req_complete_failed(req, req->cqe.res);
        } else if (unlikely(req->ctx->drain_active)) {
                io_drain_req(req);
        } else {
                int ret = io_req_prep_async(req);

                if (unlikely(ret))
                        io_req_complete_failed(req, ret);
                else
                        io_queue_iowq(req, NULL);
        }
}

/*
 * Check SQE restrictions (opcode and flags).
 *
 * Returns 'true' if SQE is allowed, 'false' otherwise.
 */
static inline bool io_check_restriction(struct io_ring_ctx *ctx,
                                        struct io_kiocb *req,
                                        unsigned int sqe_flags)
{
        if (!test_bit(req->opcode, ctx->restrictions.sqe_op))
                return false;

        if ((sqe_flags & ctx->restrictions.sqe_flags_required) !=
            ctx->restrictions.sqe_flags_required)
                return false;

        if (sqe_flags & ~(ctx->restrictions.sqe_flags_allowed |
                          ctx->restrictions.sqe_flags_required))
                return false;

        return true;
}

static void io_init_req_drain(struct io_kiocb *req)
{
        struct io_ring_ctx *ctx = req->ctx;
        struct io_kiocb *head = ctx->submit_state.link.head;

        ctx->drain_active = true;
        if (head) {
                /*
                 * If we need to drain a request in the middle of a link, drain
                 * the head request and the next request/link after the current
                 * link. Considering sequential execution of links,
                 * REQ_F_IO_DRAIN will be maintained for every request of our
                 * link.
                 */
                head->flags |= REQ_F_IO_DRAIN | REQ_F_FORCE_ASYNC;
                ctx->drain_next = true;
        }
}

static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
                       const struct io_uring_sqe *sqe)
        __must_hold(&ctx->uring_lock)
{
        const struct io_op_def *def;
        unsigned int sqe_flags;
        int personality;
        u8 opcode;

        /* req is partially pre-initialised, see io_preinit_req() */
        req->opcode = opcode = READ_ONCE(sqe->opcode);
        /* same numerical values with corresponding REQ_F_*, safe to copy */
        req->flags = sqe_flags = READ_ONCE(sqe->flags);
        req->cqe.user_data = READ_ONCE(sqe->user_data);
        req->file = NULL;
        req->rsrc_node = NULL;
        req->task = current;

        if (unlikely(opcode >= IORING_OP_LAST)) {
                req->opcode = 0;
                return -EINVAL;
        }
        def = &io_op_defs[opcode];
        if (unlikely(sqe_flags & ~SQE_COMMON_FLAGS)) {
                /* enforce forwards compatibility on users */
                if (sqe_flags & ~SQE_VALID_FLAGS)
                        return -EINVAL;
                if (sqe_flags & IOSQE_BUFFER_SELECT) {
                        if (!def->buffer_select)
                                return -EOPNOTSUPP;
                        req->buf_index = READ_ONCE(sqe->buf_group);
                }
                if (sqe_flags & IOSQE_CQE_SKIP_SUCCESS)
                        ctx->drain_disabled = true;
                if (sqe_flags & IOSQE_IO_DRAIN) {
                        if (ctx->drain_disabled)
                                return -EOPNOTSUPP;
                        io_init_req_drain(req);
                }
        }
        if (unlikely(ctx->restricted || ctx->drain_active || ctx->drain_next)) {
                if (ctx->restricted && !io_check_restriction(ctx, req, sqe_flags))
                        return -EACCES;
                /* knock it to the slow queue path, will be drained there */
                if (ctx->drain_active)
                        req->flags |= REQ_F_FORCE_ASYNC;
                /* if there is no link, we're at "next" request and need to drain */
                if (unlikely(ctx->drain_next) && !ctx->submit_state.link.head) {
                        ctx->drain_next = false;
                        ctx->drain_active = true;
                        req->flags |= REQ_F_IO_DRAIN | REQ_F_FORCE_ASYNC;
                }
        }

        if (!def->ioprio && sqe->ioprio)
                return -EINVAL;
        if (!def->iopoll && (ctx->flags & IORING_SETUP_IOPOLL))
                return -EINVAL;

        if (def->needs_file) {
                struct io_submit_state *state = &ctx->submit_state;

                req->cqe.fd = READ_ONCE(sqe->fd);

                /*
                 * Plug now if we have more than 2 IO left after this, and the
                 * target is potentially a read/write to block based storage.
                 */
                if (state->need_plug && def->plug) {
                        state->plug_started = true;
                        state->need_plug = false;
                        blk_start_plug_nr_ios(&state->plug, state->submit_nr);
                }
        }

        personality = READ_ONCE(sqe->personality);
        if (personality) {
                int ret;

                req->creds = xa_load(&ctx->personalities, personality);
                if (!req->creds)
                        return -EINVAL;
                get_cred(req->creds);
                ret = security_uring_override_creds(req->creds);
                if (ret) {
                        put_cred(req->creds);
                        return ret;
                }
                req->flags |= REQ_F_CREDS;
        }

        return def->prep(req, sqe);
}

static __cold int io_submit_fail_init(const struct io_uring_sqe *sqe,
                                      struct io_kiocb *req, int ret)
{
        struct io_ring_ctx *ctx = req->ctx;
        struct io_submit_link *link = &ctx->submit_state.link;
        struct io_kiocb *head = link->head;

        trace_io_uring_req_failed(sqe, ctx, req, ret);

        /*
         * Avoid breaking links in the middle as it renders links with SQPOLL
         * unusable. Instead of failing eagerly, continue assembling the link if
         * applicable and mark the head with REQ_F_FAIL. The link flushing code
         * should find the flag and handle the rest.
         */
        req_fail_link_node(req, ret);
        if (head && !(head->flags & REQ_F_FAIL))
                req_fail_link_node(head, -ECANCELED);

        if (!(req->flags & IO_REQ_LINK_FLAGS)) {
                if (head) {
                        link->last->link = req;
                        link->head = NULL;
                        req = head;
                }
                io_queue_sqe_fallback(req);
                return ret;
        }

        if (head)
                link->last->link = req;
        else
                link->head = req;
        link->last = req;
        return 0;
}

static inline int io_submit_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req,
                         const struct io_uring_sqe *sqe)
        __must_hold(&ctx->uring_lock)
{
        struct io_submit_link *link = &ctx->submit_state.link;
        int ret;

        ret = io_init_req(ctx, req, sqe);
        if (unlikely(ret))
                return io_submit_fail_init(sqe, req, ret);

        /* don't need @sqe from now on */
        trace_io_uring_submit_sqe(ctx, req, req->cqe.user_data, req->opcode,
                                  req->flags, true,
                                  ctx->flags & IORING_SETUP_SQPOLL);

        /*
         * If we already have a head request, queue this one for async
         * submittal once the head completes. If we don't have a head but
         * IOSQE_IO_LINK is set in the sqe, start a new head. This one will be
         * submitted sync once the chain is complete. If none of those
         * conditions are true (normal request), then just queue it.
         */
        if (unlikely(link->head)) {
                ret = io_req_prep_async(req);
                if (unlikely(ret))
                        return io_submit_fail_init(sqe, req, ret);

                trace_io_uring_link(ctx, req, link->head);
                link->last->link = req;
                link->last = req;

                if (req->flags & IO_REQ_LINK_FLAGS)
                        return 0;
                /* last request of the link, flush it */
                req = link->head;
                link->head = NULL;
                if (req->flags & (REQ_F_FORCE_ASYNC | REQ_F_FAIL))
                        goto fallback;

        } else if (unlikely(req->flags & (IO_REQ_LINK_FLAGS |
                                          REQ_F_FORCE_ASYNC | REQ_F_FAIL))) {
                if (req->flags & IO_REQ_LINK_FLAGS) {
                        link->head = req;
                        link->last = req;
                } else {
fallback:
                        io_queue_sqe_fallback(req);
                }
                return 0;
        }

        io_queue_sqe(req);
        return 0;
}

/*
 * Batched submission is done, ensure local IO is flushed out.
 */
static void io_submit_state_end(struct io_ring_ctx *ctx)
{
        struct io_submit_state *state = &ctx->submit_state;

        if (unlikely(state->link.head))
                io_queue_sqe_fallback(state->link.head);
        /* flush only after queuing links as they can generate completions */
        io_submit_flush_completions(ctx);
        if (state->plug_started)
                blk_finish_plug(&state->plug);
}

/*
 * Start submission side cache.
 */
static void io_submit_state_start(struct io_submit_state *state,
                                  unsigned int max_ios)
{
        state->plug_started = false;
        state->need_plug = max_ios > 2;
        state->submit_nr = max_ios;
        /* set only head, no need to init link_last in advance */
        state->link.head = NULL;
}

static void io_commit_sqring(struct io_ring_ctx *ctx)
{
        struct io_rings *rings = ctx->rings;

        /*
         * Ensure any loads from the SQEs are done at this point,
         * since once we write the new head, the application could
         * write new data to them.
         */
        smp_store_release(&rings->sq.head, ctx->cached_sq_head);
}

/*
 * Fetch an sqe, if one is available. Note this returns a pointer to memory
 * that is mapped by userspace. This means that care needs to be taken to
 * ensure that reads are stable, as we cannot rely on userspace always
 * being a good citizen. If members of the sqe are validated and then later
 * used, it's important that those reads are done through READ_ONCE() to
 * prevent a re-load down the line.
 */
static const struct io_uring_sqe *io_get_sqe(struct io_ring_ctx *ctx)
{
        unsigned head, mask = ctx->sq_entries - 1;
        unsigned sq_idx = ctx->cached_sq_head++ & mask;

        /*
         * The cached sq head (or cq tail) serves two purposes:
         *
         * 1) allows us to batch the cost of updating the user visible
         *    head updates.
         * 2) allows the kernel side to track the head on its own, even
         *    though the application is the one updating it.
         */
        head = READ_ONCE(ctx->sq_array[sq_idx]);
        if (likely(head < ctx->sq_entries)) {
                /* double index for 128-byte SQEs, twice as long */
                if (ctx->flags & IORING_SETUP_SQE128)
                        head <<= 1;
                return &ctx->sq_sqes[head];
        }

        /* drop invalid entries */
        ctx->cq_extra--;
        WRITE_ONCE(ctx->rings->sq_dropped,
                   READ_ONCE(ctx->rings->sq_dropped) + 1);
        return NULL;
}

static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr)
        __must_hold(&ctx->uring_lock)
{
        unsigned int entries = io_sqring_entries(ctx);
        unsigned int left;
        int ret;

        if (unlikely(!entries))
                return 0;
        /* make sure SQ entry isn't read before tail */
        ret = left = min3(nr, ctx->sq_entries, entries);
        io_get_task_refs(left);
        io_submit_state_start(&ctx->submit_state, left);

        do {
                const struct io_uring_sqe *sqe;
                struct io_kiocb *req;

                if (unlikely(!io_alloc_req_refill(ctx)))
                        break;
                req = io_alloc_req(ctx);
                sqe = io_get_sqe(ctx);
                if (unlikely(!sqe)) {
                        io_req_add_to_cache(req, ctx);
                        break;
                }

                /*
                 * Continue submitting even for sqe failure if the
                 * ring was setup with IORING_SETUP_SUBMIT_ALL
                 */
                if (unlikely(io_submit_sqe(ctx, req, sqe)) &&
                    !(ctx->flags & IORING_SETUP_SUBMIT_ALL)) {
                        left--;
                        break;
                }
        } while (--left);

        if (unlikely(left)) {
                ret -= left;
                /* try again if it submitted nothing and can't allocate a req */
                if (!ret && io_req_cache_empty(ctx))
                        ret = -EAGAIN;
                current->io_uring->cached_refs += left;
        }

        io_submit_state_end(ctx);
         /* Commit SQ ring head once we've consumed and submitted all SQEs */
        io_commit_sqring(ctx);
        return ret;
}

static inline bool io_sqd_events_pending(struct io_sq_data *sqd)
{
        return READ_ONCE(sqd->state);
}

static int __io_sq_thread(struct io_ring_ctx *ctx, bool cap_entries)
{
        unsigned int to_submit;
        int ret = 0;

        to_submit = io_sqring_entries(ctx);
        /* if we're handling multiple rings, cap submit size for fairness */
        if (cap_entries && to_submit > IORING_SQPOLL_CAP_ENTRIES_VALUE)
                to_submit = IORING_SQPOLL_CAP_ENTRIES_VALUE;

        if (!wq_list_empty(&ctx->iopoll_list) || to_submit) {
                const struct cred *creds = NULL;

                if (ctx->sq_creds != current_cred())
                        creds = override_creds(ctx->sq_creds);

                mutex_lock(&ctx->uring_lock);
                if (!wq_list_empty(&ctx->iopoll_list))
                        io_do_iopoll(ctx, true);

                /*
                 * Don't submit if refs are dying, good for io_uring_register(),
                 * but also it is relied upon by io_ring_exit_work()
                 */
                if (to_submit && likely(!percpu_ref_is_dying(&ctx->refs)) &&
                    !(ctx->flags & IORING_SETUP_R_DISABLED))
                        ret = io_submit_sqes(ctx, to_submit);
                mutex_unlock(&ctx->uring_lock);

                if (to_submit && wq_has_sleeper(&ctx->sqo_sq_wait))
                        wake_up(&ctx->sqo_sq_wait);
                if (creds)
                        revert_creds(creds);
        }

        return ret;
}

static __cold void io_sqd_update_thread_idle(struct io_sq_data *sqd)
{
        struct io_ring_ctx *ctx;
        unsigned sq_thread_idle = 0;

        list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
                sq_thread_idle = max(sq_thread_idle, ctx->sq_thread_idle);
        sqd->sq_thread_idle = sq_thread_idle;
}

static bool io_sqd_handle_event(struct io_sq_data *sqd)
{
        bool did_sig = false;
        struct ksignal ksig;

        if (test_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state) ||
            signal_pending(current)) {
                mutex_unlock(&sqd->lock);
                if (signal_pending(current))
                        did_sig = get_signal(&ksig);
                cond_resched();
                mutex_lock(&sqd->lock);
        }
        return did_sig || test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state);
}

static int io_sq_thread(void *data)
{
        struct io_sq_data *sqd = data;
        struct io_ring_ctx *ctx;
        unsigned long timeout = 0;
        char buf[TASK_COMM_LEN];
        DEFINE_WAIT(wait);

        snprintf(buf, sizeof(buf), "iou-sqp-%d", sqd->task_pid);
        set_task_comm(current, buf);

        if (sqd->sq_cpu != -1)
                set_cpus_allowed_ptr(current, cpumask_of(sqd->sq_cpu));
        else
                set_cpus_allowed_ptr(current, cpu_online_mask);
        current->flags |= PF_NO_SETAFFINITY;

        audit_alloc_kernel(current);

        mutex_lock(&sqd->lock);
        while (1) {
                bool cap_entries, sqt_spin = false;

                if (io_sqd_events_pending(sqd) || signal_pending(current)) {
                        if (io_sqd_handle_event(sqd))
                                break;
                        timeout = jiffies + sqd->sq_thread_idle;
                }

                cap_entries = !list_is_singular(&sqd->ctx_list);
                list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
                        int ret = __io_sq_thread(ctx, cap_entries);

                        if (!sqt_spin && (ret > 0 || !wq_list_empty(&ctx->iopoll_list)))
                                sqt_spin = true;
                }
                if (io_run_task_work())
                        sqt_spin = true;

                if (sqt_spin || !time_after(jiffies, timeout)) {
                        cond_resched();
                        if (sqt_spin)
                                timeout = jiffies + sqd->sq_thread_idle;
                        continue;
                }

                prepare_to_wait(&sqd->wait, &wait, TASK_INTERRUPTIBLE);
                if (!io_sqd_events_pending(sqd) && !task_work_pending(current)) {
                        bool needs_sched = true;

                        list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
                                atomic_or(IORING_SQ_NEED_WAKEUP,
                                                &ctx->rings->sq_flags);
                                if ((ctx->flags & IORING_SETUP_IOPOLL) &&
                                    !wq_list_empty(&ctx->iopoll_list)) {
                                        needs_sched = false;
                                        break;
                                }

                                /*
                                 * Ensure the store of the wakeup flag is not
                                 * reordered with the load of the SQ tail
                                 */
                                smp_mb__after_atomic();

                                if (io_sqring_entries(ctx)) {
                                        needs_sched = false;
                                        break;
                                }
                        }

                        if (needs_sched) {
                                mutex_unlock(&sqd->lock);
                                schedule();
                                mutex_lock(&sqd->lock);
                        }
                        list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
                                atomic_andnot(IORING_SQ_NEED_WAKEUP,
                                                &ctx->rings->sq_flags);
                }

                finish_wait(&sqd->wait, &wait);
                timeout = jiffies + sqd->sq_thread_idle;
        }

        io_uring_cancel_generic(true, sqd);
        sqd->thread = NULL;
        list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
                atomic_or(IORING_SQ_NEED_WAKEUP, &ctx->rings->sq_flags);
        io_run_task_work();
        mutex_unlock(&sqd->lock);

        audit_free(current);

        complete(&sqd->exited);
        do_exit(0);
}

struct io_wait_queue {
        struct wait_queue_entry wq;
        struct io_ring_ctx *ctx;
        unsigned cq_tail;
        unsigned nr_timeouts;
};

static inline bool io_should_wake(struct io_wait_queue *iowq)
{
        struct io_ring_ctx *ctx = iowq->ctx;
        int dist = ctx->cached_cq_tail - (int) iowq->cq_tail;

        /*
         * Wake up if we have enough events, or if a timeout occurred since we
         * started waiting. For timeouts, we always want to return to userspace,
         * regardless of event count.
         */
        return dist >= 0 || atomic_read(&ctx->cq_timeouts) != iowq->nr_timeouts;
}

static int io_wake_function(struct wait_queue_entry *curr, unsigned int mode,
                            int wake_flags, void *key)
{
        struct io_wait_queue *iowq = container_of(curr, struct io_wait_queue,
                                                        wq);

        /*
         * Cannot safely flush overflowed CQEs from here, ensure we wake up
         * the task, and the next invocation will do it.
         */
        if (io_should_wake(iowq) ||
            test_bit(IO_CHECK_CQ_OVERFLOW_BIT, &iowq->ctx->check_cq))
                return autoremove_wake_function(curr, mode, wake_flags, key);
        return -1;
}

static int io_run_task_work_sig(void)
{
        if (io_run_task_work())
                return 1;
        if (test_thread_flag(TIF_NOTIFY_SIGNAL))
                return -ERESTARTSYS;
        if (task_sigpending(current))
                return -EINTR;
        return 0;
}

/* when returns >0, the caller should retry */
static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx,
                                          struct io_wait_queue *iowq,
                                          ktime_t timeout)
{
        int ret;
        unsigned long check_cq;

        /* make sure we run task_work before checking for signals */
        ret = io_run_task_work_sig();
        if (ret || io_should_wake(iowq))
                return ret;
        check_cq = READ_ONCE(ctx->check_cq);
        /* let the caller flush overflows, retry */
        if (check_cq & BIT(IO_CHECK_CQ_OVERFLOW_BIT))
                return 1;
        if (unlikely(check_cq & BIT(IO_CHECK_CQ_DROPPED_BIT)))
                return -EBADR;
        if (!schedule_hrtimeout(&timeout, HRTIMER_MODE_ABS))
                return -ETIME;
        return 1;
}

/*
 * Wait until events become available, if we don't already have some. The
 * application must reap them itself, as they reside on the shared cq ring.
 */
static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
                          const sigset_t __user *sig, size_t sigsz,
                          struct __kernel_timespec __user *uts)
{
        struct io_wait_queue iowq;
        struct io_rings *rings = ctx->rings;
        ktime_t timeout = KTIME_MAX;
        int ret;

        do {
                io_cqring_overflow_flush(ctx);
                if (io_cqring_events(ctx) >= min_events)
                        return 0;
                if (!io_run_task_work())
                        break;
        } while (1);

        if (sig) {
#ifdef CONFIG_COMPAT
                if (in_compat_syscall())
                        ret = set_compat_user_sigmask((const compat_sigset_t __user *)sig,
                                                      sigsz);
                else
#endif
                        ret = set_user_sigmask(sig, sigsz);

                if (ret)
                        return ret;
        }

        if (uts) {
                struct timespec64 ts;

                if (get_timespec64(&ts, uts))
                        return -EFAULT;
                timeout = ktime_add_ns(timespec64_to_ktime(ts), ktime_get_ns());
        }

        init_waitqueue_func_entry(&iowq.wq, io_wake_function);
        iowq.wq.private = current;
        INIT_LIST_HEAD(&iowq.wq.entry);
        iowq.ctx = ctx;
        iowq.nr_timeouts = atomic_read(&ctx->cq_timeouts);
        iowq.cq_tail = READ_ONCE(ctx->rings->cq.head) + min_events;

        trace_io_uring_cqring_wait(ctx, min_events);
        do {
                /* if we can't even flush overflow, don't wait for more */
                if (!io_cqring_overflow_flush(ctx)) {
                        ret = -EBUSY;
                        break;
                }
                prepare_to_wait_exclusive(&ctx->cq_wait, &iowq.wq,
                                                TASK_INTERRUPTIBLE);
                ret = io_cqring_wait_schedule(ctx, &iowq, timeout);
                cond_resched();
        } while (ret > 0);

        finish_wait(&ctx->cq_wait, &iowq.wq);
        restore_saved_sigmask_unless(ret == -EINTR);

        return READ_ONCE(rings->cq.head) == READ_ONCE(rings->cq.tail) ? ret : 0;
}

static void io_free_page_table(void **table, size_t size)
{
        unsigned i, nr_tables = DIV_ROUND_UP(size, PAGE_SIZE);

        for (i = 0; i < nr_tables; i++)
                kfree(table[i]);
        kfree(table);
}

static __cold void **io_alloc_page_table(size_t size)
{
        unsigned i, nr_tables = DIV_ROUND_UP(size, PAGE_SIZE);
        size_t init_size = size;
        void **table;

        table = kcalloc(nr_tables, sizeof(*table), GFP_KERNEL_ACCOUNT);
        if (!table)
                return NULL;

        for (i = 0; i < nr_tables; i++) {
                unsigned int this_size = min_t(size_t, size, PAGE_SIZE);

                table[i] = kzalloc(this_size, GFP_KERNEL_ACCOUNT);
                if (!table[i]) {
                        io_free_page_table(table, init_size);
                        return NULL;
                }
                size -= this_size;
        }
        return table;
}

static void io_rsrc_node_destroy(struct io_rsrc_node *ref_node)
{
        percpu_ref_exit(&ref_node->refs);
        kfree(ref_node);
}

static __cold void io_rsrc_node_ref_zero(struct percpu_ref *ref)
{
        struct io_rsrc_node *node = container_of(ref, struct io_rsrc_node, refs);
        struct io_ring_ctx *ctx = node->rsrc_data->ctx;
        unsigned long flags;
        bool first_add = false;
        unsigned long delay = HZ;

        spin_lock_irqsave(&ctx->rsrc_ref_lock, flags);
        node->done = true;

        /* if we are mid-quiesce then do not delay */
        if (node->rsrc_data->quiesce)
                delay = 0;

        while (!list_empty(&ctx->rsrc_ref_list)) {
                node = list_first_entry(&ctx->rsrc_ref_list,
                                            struct io_rsrc_node, node);
                /* recycle ref nodes in order */
                if (!node->done)
                        break;
                list_del(&node->node);
                first_add |= llist_add(&node->llist, &ctx->rsrc_put_llist);
        }
        spin_unlock_irqrestore(&ctx->rsrc_ref_lock, flags);

        if (first_add)
                mod_delayed_work(system_wq, &ctx->rsrc_put_work, delay);
}

static struct io_rsrc_node *io_rsrc_node_alloc(void)
{
        struct io_rsrc_node *ref_node;

        ref_node = kzalloc(sizeof(*ref_node), GFP_KERNEL);
        if (!ref_node)
                return NULL;

        if (percpu_ref_init(&ref_node->refs, io_rsrc_node_ref_zero,
                            0, GFP_KERNEL)) {
                kfree(ref_node);
                return NULL;
        }
        INIT_LIST_HEAD(&ref_node->node);
        INIT_LIST_HEAD(&ref_node->rsrc_list);
        ref_node->done = false;
        return ref_node;
}

void io_rsrc_node_switch(struct io_ring_ctx *ctx,
                         struct io_rsrc_data *data_to_kill)
        __must_hold(&ctx->uring_lock)
{
        WARN_ON_ONCE(!ctx->rsrc_backup_node);
        WARN_ON_ONCE(data_to_kill && !ctx->rsrc_node);

        io_rsrc_refs_drop(ctx);

        if (data_to_kill) {
                struct io_rsrc_node *rsrc_node = ctx->rsrc_node;

                rsrc_node->rsrc_data = data_to_kill;
                spin_lock_irq(&ctx->rsrc_ref_lock);
                list_add_tail(&rsrc_node->node, &ctx->rsrc_ref_list);
                spin_unlock_irq(&ctx->rsrc_ref_lock);

                atomic_inc(&data_to_kill->refs);
                percpu_ref_kill(&rsrc_node->refs);
                ctx->rsrc_node = NULL;
        }

        if (!ctx->rsrc_node) {
                ctx->rsrc_node = ctx->rsrc_backup_node;
                ctx->rsrc_backup_node = NULL;
        }
}

int io_rsrc_node_switch_start(struct io_ring_ctx *ctx)
{
        if (ctx->rsrc_backup_node)
                return 0;
        ctx->rsrc_backup_node = io_rsrc_node_alloc();
        return ctx->rsrc_backup_node ? 0 : -ENOMEM;
}

static __cold int io_rsrc_ref_quiesce(struct io_rsrc_data *data,
                                      struct io_ring_ctx *ctx)
{
        int ret;

        /* As we may drop ->uring_lock, other task may have started quiesce */
        if (data->quiesce)
                return -ENXIO;

        data->quiesce = true;
        do {
                ret = io_rsrc_node_switch_start(ctx);
                if (ret)
                        break;
                io_rsrc_node_switch(ctx, data);

                /* kill initial ref, already quiesced if zero */
                if (atomic_dec_and_test(&data->refs))
                        break;
                mutex_unlock(&ctx->uring_lock);
                flush_delayed_work(&ctx->rsrc_put_work);
                ret = wait_for_completion_interruptible(&data->done);
                if (!ret) {
                        mutex_lock(&ctx->uring_lock);
                        if (atomic_read(&data->refs) > 0) {
                                /*
                                 * it has been revived by another thread while
                                 * we were unlocked
                                 */
                                mutex_unlock(&ctx->uring_lock);
                        } else {
                                break;
                        }
                }

                atomic_inc(&data->refs);
                /* wait for all works potentially completing data->done */
                flush_delayed_work(&ctx->rsrc_put_work);
                reinit_completion(&data->done);

                ret = io_run_task_work_sig();
                mutex_lock(&ctx->uring_lock);
        } while (ret >= 0);
        data->quiesce = false;

        return ret;
}

static u64 *io_get_tag_slot(struct io_rsrc_data *data, unsigned int idx)
{
        unsigned int off = idx & IO_RSRC_TAG_TABLE_MASK;
        unsigned int table_idx = idx >> IO_RSRC_TAG_TABLE_SHIFT;

        return &data->tags[table_idx][off];
}

static void io_rsrc_data_free(struct io_rsrc_data *data)
{
        size_t size = data->nr * sizeof(data->tags[0][0]);

        if (data->tags)
                io_free_page_table((void **)data->tags, size);
        kfree(data);
}

static __cold int io_rsrc_data_alloc(struct io_ring_ctx *ctx, rsrc_put_fn *do_put,
                                     u64 __user *utags, unsigned nr,
                                     struct io_rsrc_data **pdata)
{
        struct io_rsrc_data *data;
        int ret = -ENOMEM;
        unsigned i;

        data = kzalloc(sizeof(*data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;
        data->tags = (u64 **)io_alloc_page_table(nr * sizeof(data->tags[0][0]));
        if (!data->tags) {
                kfree(data);
                return -ENOMEM;
        }

        data->nr = nr;
        data->ctx = ctx;
        data->do_put = do_put;
        if (utags) {
                ret = -EFAULT;
                for (i = 0; i < nr; i++) {
                        u64 *tag_slot = io_get_tag_slot(data, i);

                        if (copy_from_user(tag_slot, &utags[i],
                                           sizeof(*tag_slot)))
                                goto fail;
                }
        }

        atomic_set(&data->refs, 1);
        init_completion(&data->done);
        *pdata = data;
        return 0;
fail:
        io_rsrc_data_free(data);
        return ret;
}

static void __io_sqe_files_unregister(struct io_ring_ctx *ctx)
{
#if !defined(IO_URING_SCM_ALL)
        int i;

        for (i = 0; i < ctx->nr_user_files; i++) {
                struct file *file = io_file_from_index(ctx, i);

                if (!file)
                        continue;
                if (io_fixed_file_slot(&ctx->file_table, i)->file_ptr & FFS_SCM)
                        continue;
                io_file_bitmap_clear(&ctx->file_table, i);
                fput(file);
        }
#endif

#if defined(CONFIG_UNIX)
        if (ctx->ring_sock) {
                struct sock *sock = ctx->ring_sock->sk;
                struct sk_buff *skb;

                while ((skb = skb_dequeue(&sock->sk_receive_queue)) != NULL)
                        kfree_skb(skb);
        }
#endif
        io_free_file_tables(&ctx->file_table);
        io_rsrc_data_free(ctx->file_data);
        ctx->file_data = NULL;
        ctx->nr_user_files = 0;
}

static int io_sqe_files_unregister(struct io_ring_ctx *ctx)
{
        unsigned nr = ctx->nr_user_files;
        int ret;

        if (!ctx->file_data)
                return -ENXIO;

        /*
         * Quiesce may unlock ->uring_lock, and while it's not held
         * prevent new requests using the table.
         */
        ctx->nr_user_files = 0;
        ret = io_rsrc_ref_quiesce(ctx->file_data, ctx);
        ctx->nr_user_files = nr;
        if (!ret)
                __io_sqe_files_unregister(ctx);
        return ret;
}

static void io_sq_thread_unpark(struct io_sq_data *sqd)
        __releases(&sqd->lock)
{
        WARN_ON_ONCE(sqd->thread == current);

        /*
         * Do the dance but not conditional clear_bit() because it'd race with
         * other threads incrementing park_pending and setting the bit.
         */
        clear_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state);
        if (atomic_dec_return(&sqd->park_pending))
                set_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state);
        mutex_unlock(&sqd->lock);
}

static void io_sq_thread_park(struct io_sq_data *sqd)
        __acquires(&sqd->lock)
{
        WARN_ON_ONCE(sqd->thread == current);

        atomic_inc(&sqd->park_pending);
        set_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state);
        mutex_lock(&sqd->lock);
        if (sqd->thread)
                wake_up_process(sqd->thread);
}

static void io_sq_thread_stop(struct io_sq_data *sqd)
{
        WARN_ON_ONCE(sqd->thread == current);
        WARN_ON_ONCE(test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state));

        set_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state);
        mutex_lock(&sqd->lock);
        if (sqd->thread)
                wake_up_process(sqd->thread);
        mutex_unlock(&sqd->lock);
        wait_for_completion(&sqd->exited);
}

static void io_put_sq_data(struct io_sq_data *sqd)
{
        if (refcount_dec_and_test(&sqd->refs)) {
                WARN_ON_ONCE(atomic_read(&sqd->park_pending));

                io_sq_thread_stop(sqd);
                kfree(sqd);
        }
}

static void io_sq_thread_finish(struct io_ring_ctx *ctx)
{
        struct io_sq_data *sqd = ctx->sq_data;

        if (sqd) {
                io_sq_thread_park(sqd);
                list_del_init(&ctx->sqd_list);
                io_sqd_update_thread_idle(sqd);
                io_sq_thread_unpark(sqd);

                io_put_sq_data(sqd);
                ctx->sq_data = NULL;
        }
}

static struct io_sq_data *io_attach_sq_data(struct io_uring_params *p)
{
        struct io_ring_ctx *ctx_attach;
        struct io_sq_data *sqd;
        struct fd f;

        f = fdget(p->wq_fd);
        if (!f.file)
                return ERR_PTR(-ENXIO);
        if (f.file->f_op != &io_uring_fops) {
                fdput(f);
                return ERR_PTR(-EINVAL);
        }

        ctx_attach = f.file->private_data;
        sqd = ctx_attach->sq_data;
        if (!sqd) {
                fdput(f);
                return ERR_PTR(-EINVAL);
        }
        if (sqd->task_tgid != current->tgid) {
                fdput(f);
                return ERR_PTR(-EPERM);
        }

        refcount_inc(&sqd->refs);
        fdput(f);
        return sqd;
}

static struct io_sq_data *io_get_sq_data(struct io_uring_params *p,
                                         bool *attached)
{
        struct io_sq_data *sqd;

        *attached = false;
        if (p->flags & IORING_SETUP_ATTACH_WQ) {
                sqd = io_attach_sq_data(p);
                if (!IS_ERR(sqd)) {
                        *attached = true;
                        return sqd;
                }
                /* fall through for EPERM case, setup new sqd/task */
                if (PTR_ERR(sqd) != -EPERM)
                        return sqd;
        }

        sqd = kzalloc(sizeof(*sqd), GFP_KERNEL);
        if (!sqd)
                return ERR_PTR(-ENOMEM);

        atomic_set(&sqd->park_pending, 0);
        refcount_set(&sqd->refs, 1);
        INIT_LIST_HEAD(&sqd->ctx_list);
        mutex_init(&sqd->lock);
        init_waitqueue_head(&sqd->wait);
        init_completion(&sqd->exited);
        return sqd;
}

/*
 * Ensure the UNIX gc is aware of our file set, so we are certain that
 * the io_uring can be safely unregistered on process exit, even if we have
 * loops in the file referencing. We account only files that can hold other
 * files because otherwise they can't form a loop and so are not interesting
 * for GC.
 */
static int io_scm_file_account(struct io_ring_ctx *ctx, struct file *file)
{
#if defined(CONFIG_UNIX)
        struct sock *sk = ctx->ring_sock->sk;
        struct sk_buff_head *head = &sk->sk_receive_queue;
        struct scm_fp_list *fpl;
        struct sk_buff *skb;

        if (likely(!io_file_need_scm(file)))
                return 0;

        /*
         * See if we can merge this file into an existing skb SCM_RIGHTS
         * file set. If there's no room, fall back to allocating a new skb
         * and filling it in.
         */
        spin_lock_irq(&head->lock);
        skb = skb_peek(head);
        if (skb && UNIXCB(skb).fp->count < SCM_MAX_FD)
                __skb_unlink(skb, head);
        else
                skb = NULL;
        spin_unlock_irq(&head->lock);

        if (!skb) {
                fpl = kzalloc(sizeof(*fpl), GFP_KERNEL);
                if (!fpl)
                        return -ENOMEM;

                skb = alloc_skb(0, GFP_KERNEL);
                if (!skb) {
                        kfree(fpl);
                        return -ENOMEM;
                }

                fpl->user = get_uid(current_user());
                fpl->max = SCM_MAX_FD;
                fpl->count = 0;

                UNIXCB(skb).fp = fpl;
                skb->sk = sk;
                skb->destructor = unix_destruct_scm;
                refcount_add(skb->truesize, &sk->sk_wmem_alloc);
        }

        fpl = UNIXCB(skb).fp;
        fpl->fp[fpl->count++] = get_file(file);
        unix_inflight(fpl->user, file);
        skb_queue_head(head, skb);
        fput(file);
#endif
        return 0;
}

static void io_rsrc_file_put(struct io_ring_ctx *ctx, struct io_rsrc_put *prsrc)
{
        struct file *file = prsrc->file;
#if defined(CONFIG_UNIX)
        struct sock *sock = ctx->ring_sock->sk;
        struct sk_buff_head list, *head = &sock->sk_receive_queue;
        struct sk_buff *skb;
        int i;

        if (!io_file_need_scm(file)) {
                fput(file);
                return;
        }

        __skb_queue_head_init(&list);

        /*
         * Find the skb that holds this file in its SCM_RIGHTS. When found,
         * remove this entry and rearrange the file array.
         */
        skb = skb_dequeue(head);
        while (skb) {
                struct scm_fp_list *fp;

                fp = UNIXCB(skb).fp;
                for (i = 0; i < fp->count; i++) {
                        int left;

                        if (fp->fp[i] != file)
                                continue;

                        unix_notinflight(fp->user, fp->fp[i]);
                        left = fp->count - 1 - i;
                        if (left) {
                                memmove(&fp->fp[i], &fp->fp[i + 1],
                                                left * sizeof(struct file *));
                        }
                        fp->count--;
                        if (!fp->count) {
                                kfree_skb(skb);
                                skb = NULL;
                        } else {
                                __skb_queue_tail(&list, skb);
                        }
                        fput(file);
                        file = NULL;
                        break;
                }

                if (!file)
                        break;

                __skb_queue_tail(&list, skb);

                skb = skb_dequeue(head);
        }

        if (skb_peek(&list)) {
                spin_lock_irq(&head->lock);
                while ((skb = __skb_dequeue(&list)) != NULL)
                        __skb_queue_tail(head, skb);
                spin_unlock_irq(&head->lock);
        }
#else
        fput(file);
#endif
}

static void __io_rsrc_put_work(struct io_rsrc_node *ref_node)
{
        struct io_rsrc_data *rsrc_data = ref_node->rsrc_data;
        struct io_ring_ctx *ctx = rsrc_data->ctx;
        struct io_rsrc_put *prsrc, *tmp;

        list_for_each_entry_safe(prsrc, tmp, &ref_node->rsrc_list, list) {
                list_del(&prsrc->list);

                if (prsrc->tag) {
                        if (ctx->flags & IORING_SETUP_IOPOLL)
                                mutex_lock(&ctx->uring_lock);

                        spin_lock(&ctx->completion_lock);
                        io_fill_cqe_aux(ctx, prsrc->tag, 0, 0);
                        io_commit_cqring(ctx);
                        spin_unlock(&ctx->completion_lock);
                        io_cqring_ev_posted(ctx);

                        if (ctx->flags & IORING_SETUP_IOPOLL)
                                mutex_unlock(&ctx->uring_lock);
                }

                rsrc_data->do_put(ctx, prsrc);
                kfree(prsrc);
        }

        io_rsrc_node_destroy(ref_node);
        if (atomic_dec_and_test(&rsrc_data->refs))
                complete(&rsrc_data->done);
}

static void io_rsrc_put_work(struct work_struct *work)
{
        struct io_ring_ctx *ctx;
        struct llist_node *node;

        ctx = container_of(work, struct io_ring_ctx, rsrc_put_work.work);
        node = llist_del_all(&ctx->rsrc_put_llist);

        while (node) {
                struct io_rsrc_node *ref_node;
                struct llist_node *next = node->next;

                ref_node = llist_entry(node, struct io_rsrc_node, llist);
                __io_rsrc_put_work(ref_node);
                node = next;
        }
}

static int io_sqe_files_register(struct io_ring_ctx *ctx, void __user *arg,
                                 unsigned nr_args, u64 __user *tags)
{
        __s32 __user *fds = (__s32 __user *) arg;
        struct file *file;
        int fd, ret;
        unsigned i;

        if (ctx->file_data)
                return -EBUSY;
        if (!nr_args)
                return -EINVAL;
        if (nr_args > IORING_MAX_FIXED_FILES)
                return -EMFILE;
        if (nr_args > rlimit(RLIMIT_NOFILE))
                return -EMFILE;
        ret = io_rsrc_node_switch_start(ctx);
        if (ret)
                return ret;
        ret = io_rsrc_data_alloc(ctx, io_rsrc_file_put, tags, nr_args,
                                 &ctx->file_data);
        if (ret)
                return ret;

        if (!io_alloc_file_tables(&ctx->file_table, nr_args)) {
                io_rsrc_data_free(ctx->file_data);
                ctx->file_data = NULL;
                return -ENOMEM;
        }

        for (i = 0; i < nr_args; i++, ctx->nr_user_files++) {
                struct io_fixed_file *file_slot;

                if (fds && copy_from_user(&fd, &fds[i], sizeof(fd))) {
                        ret = -EFAULT;
                        goto fail;
                }
                /* allow sparse sets */
                if (!fds || fd == -1) {
                        ret = -EINVAL;
                        if (unlikely(*io_get_tag_slot(ctx->file_data, i)))
                                goto fail;
                        continue;
                }

                file = fget(fd);
                ret = -EBADF;
                if (unlikely(!file))
                        goto fail;

                /*
                 * Don't allow io_uring instances to be registered. If UNIX
                 * isn't enabled, then this causes a reference cycle and this
                 * instance can never get freed. If UNIX is enabled we'll
                 * handle it just fine, but there's still no point in allowing
                 * a ring fd as it doesn't support regular read/write anyway.
                 */
                if (file->f_op == &io_uring_fops) {
                        fput(file);
                        goto fail;
                }
                ret = io_scm_file_account(ctx, file);
                if (ret) {
                        fput(file);
                        goto fail;
                }
                file_slot = io_fixed_file_slot(&ctx->file_table, i);
                io_fixed_file_set(file_slot, file);
                io_file_bitmap_set(&ctx->file_table, i);
        }

        io_rsrc_node_switch(ctx, NULL);
        return 0;
fail:
        __io_sqe_files_unregister(ctx);
        return ret;
}

int io_queue_rsrc_removal(struct io_rsrc_data *data, unsigned idx,
                          struct io_rsrc_node *node, void *rsrc)
{
        u64 *tag_slot = io_get_tag_slot(data, idx);
        struct io_rsrc_put *prsrc;

        prsrc = kzalloc(sizeof(*prsrc), GFP_KERNEL);
        if (!prsrc)
                return -ENOMEM;

        prsrc->tag = *tag_slot;
        *tag_slot = 0;
        prsrc->rsrc = rsrc;
        list_add(&prsrc->list, &node->rsrc_list);
        return 0;
}

int io_install_fixed_file(struct io_kiocb *req, struct file *file,
                          unsigned int issue_flags, u32 slot_index)
        __must_hold(&req->ctx->uring_lock)
{
        struct io_ring_ctx *ctx = req->ctx;
        bool needs_switch = false;
        struct io_fixed_file *file_slot;
        int ret;

        if (file->f_op == &io_uring_fops)
                return -EBADF;
        if (!ctx->file_data)
                return -ENXIO;
        if (slot_index >= ctx->nr_user_files)
                return -EINVAL;

        slot_index = array_index_nospec(slot_index, ctx->nr_user_files);
        file_slot = io_fixed_file_slot(&ctx->file_table, slot_index);

        if (file_slot->file_ptr) {
                struct file *old_file;

                ret = io_rsrc_node_switch_start(ctx);
                if (ret)
                        goto err;

                old_file = (struct file *)(file_slot->file_ptr & FFS_MASK);
                ret = io_queue_rsrc_removal(ctx->file_data, slot_index,
                                            ctx->rsrc_node, old_file);
                if (ret)
                        goto err;
                file_slot->file_ptr = 0;
                io_file_bitmap_clear(&ctx->file_table, slot_index);
                needs_switch = true;
        }

        ret = io_scm_file_account(ctx, file);
        if (!ret) {
                *io_get_tag_slot(ctx->file_data, slot_index) = 0;
                io_fixed_file_set(file_slot, file);
                io_file_bitmap_set(&ctx->file_table, slot_index);
        }
err:
        if (needs_switch)
                io_rsrc_node_switch(ctx, ctx->file_data);
        if (ret)
                fput(file);
        return ret;
}

static int __io_sqe_files_update(struct io_ring_ctx *ctx,
                                 struct io_uring_rsrc_update2 *up,
                                 unsigned nr_args)
{
        u64 __user *tags = u64_to_user_ptr(up->tags);
        __s32 __user *fds = u64_to_user_ptr(up->data);
        struct io_rsrc_data *data = ctx->file_data;
        struct io_fixed_file *file_slot;
        struct file *file;
        int fd, i, err = 0;
        unsigned int done;
        bool needs_switch = false;

        if (!ctx->file_data)
                return -ENXIO;
        if (up->offset + nr_args > ctx->nr_user_files)
                return -EINVAL;

        for (done = 0; done < nr_args; done++) {
                u64 tag = 0;

                if ((tags && copy_from_user(&tag, &tags[done], sizeof(tag))) ||
                    copy_from_user(&fd, &fds[done], sizeof(fd))) {
                        err = -EFAULT;
                        break;
                }
                if ((fd == IORING_REGISTER_FILES_SKIP || fd == -1) && tag) {
                        err = -EINVAL;
                        break;
                }
                if (fd == IORING_REGISTER_FILES_SKIP)
                        continue;

                i = array_index_nospec(up->offset + done, ctx->nr_user_files);
                file_slot = io_fixed_file_slot(&ctx->file_table, i);

                if (file_slot->file_ptr) {
                        file = (struct file *)(file_slot->file_ptr & FFS_MASK);
                        err = io_queue_rsrc_removal(data, i, ctx->rsrc_node, file);
                        if (err)
                                break;
                        file_slot->file_ptr = 0;
                        io_file_bitmap_clear(&ctx->file_table, i);
                        needs_switch = true;
                }
                if (fd != -1) {
                        file = fget(fd);
                        if (!file) {
                                err = -EBADF;
                                break;
                        }
                        /*
                         * Don't allow io_uring instances to be registered. If
                         * UNIX isn't enabled, then this causes a reference
                         * cycle and this instance can never get freed. If UNIX
                         * is enabled we'll handle it just fine, but there's
                         * still no point in allowing a ring fd as it doesn't
                         * support regular read/write anyway.
                         */
                        if (file->f_op == &io_uring_fops) {
                                fput(file);
                                err = -EBADF;
                                break;
                        }
                        err = io_scm_file_account(ctx, file);
                        if (err) {
                                fput(file);
                                break;
                        }
                        *io_get_tag_slot(data, i) = tag;
                        io_fixed_file_set(file_slot, file);
                        io_file_bitmap_set(&ctx->file_table, i);
                }
        }

        if (needs_switch)
                io_rsrc_node_switch(ctx, data);
        return done ? done : err;
}

static struct io_wq *io_init_wq_offload(struct io_ring_ctx *ctx,
                                        struct task_struct *task)
{
        struct io_wq_hash *hash;
        struct io_wq_data data;
        unsigned int concurrency;

        mutex_lock(&ctx->uring_lock);
        hash = ctx->hash_map;
        if (!hash) {
                hash = kzalloc(sizeof(*hash), GFP_KERNEL);
                if (!hash) {
                        mutex_unlock(&ctx->uring_lock);
                        return ERR_PTR(-ENOMEM);
                }
                refcount_set(&hash->refs, 1);
                init_waitqueue_head(&hash->wait);
                ctx->hash_map = hash;
        }
        mutex_unlock(&ctx->uring_lock);

        data.hash = hash;
        data.task = task;
        data.free_work = io_wq_free_work;
        data.do_work = io_wq_submit_work;

        /* Do QD, or 4 * CPUS, whatever is smallest */
        concurrency = min(ctx->sq_entries, 4 * num_online_cpus());

        return io_wq_create(concurrency, &data);
}

static __cold int io_uring_alloc_task_context(struct task_struct *task,
                                              struct io_ring_ctx *ctx)
{
        struct io_uring_task *tctx;
        int ret;

        tctx = kzalloc(sizeof(*tctx), GFP_KERNEL);
        if (unlikely(!tctx))
                return -ENOMEM;

        tctx->registered_rings = kcalloc(IO_RINGFD_REG_MAX,
                                         sizeof(struct file *), GFP_KERNEL);
        if (unlikely(!tctx->registered_rings)) {
                kfree(tctx);
                return -ENOMEM;
        }

        ret = percpu_counter_init(&tctx->inflight, 0, GFP_KERNEL);
        if (unlikely(ret)) {
                kfree(tctx->registered_rings);
                kfree(tctx);
                return ret;
        }

        tctx->io_wq = io_init_wq_offload(ctx, task);
        if (IS_ERR(tctx->io_wq)) {
                ret = PTR_ERR(tctx->io_wq);
                percpu_counter_destroy(&tctx->inflight);
                kfree(tctx->registered_rings);
                kfree(tctx);
                return ret;
        }

        xa_init(&tctx->xa);
        init_waitqueue_head(&tctx->wait);
        atomic_set(&tctx->in_idle, 0);
        atomic_set(&tctx->inflight_tracked, 0);
        task->io_uring = tctx;
        spin_lock_init(&tctx->task_lock);
        INIT_WQ_LIST(&tctx->task_list);
        INIT_WQ_LIST(&tctx->prio_task_list);
        init_task_work(&tctx->task_work, tctx_task_work);
        return 0;
}

void __io_uring_free(struct task_struct *tsk)
{
        struct io_uring_task *tctx = tsk->io_uring;

        WARN_ON_ONCE(!xa_empty(&tctx->xa));
        WARN_ON_ONCE(tctx->io_wq);
        WARN_ON_ONCE(tctx->cached_refs);

        kfree(tctx->registered_rings);
        percpu_counter_destroy(&tctx->inflight);
        kfree(tctx);
        tsk->io_uring = NULL;
}

static __cold int io_sq_offload_create(struct io_ring_ctx *ctx,
                                       struct io_uring_params *p)
{
        int ret;

        /* Retain compatibility with failing for an invalid attach attempt */
        if ((ctx->flags & (IORING_SETUP_ATTACH_WQ | IORING_SETUP_SQPOLL)) ==
                                IORING_SETUP_ATTACH_WQ) {
                struct fd f;

                f = fdget(p->wq_fd);
                if (!f.file)
                        return -ENXIO;
                if (f.file->f_op != &io_uring_fops) {
                        fdput(f);
                        return -EINVAL;
                }
                fdput(f);
        }
        if (ctx->flags & IORING_SETUP_SQPOLL) {
                struct task_struct *tsk;
                struct io_sq_data *sqd;
                bool attached;

                ret = security_uring_sqpoll();
                if (ret)
                        return ret;

                sqd = io_get_sq_data(p, &attached);
                if (IS_ERR(sqd)) {
                        ret = PTR_ERR(sqd);
                        goto err;
                }

                ctx->sq_creds = get_current_cred();
                ctx->sq_data = sqd;
                ctx->sq_thread_idle = msecs_to_jiffies(p->sq_thread_idle);
                if (!ctx->sq_thread_idle)
                        ctx->sq_thread_idle = HZ;

                io_sq_thread_park(sqd);
                list_add(&ctx->sqd_list, &sqd->ctx_list);
                io_sqd_update_thread_idle(sqd);
                /* don't attach to a dying SQPOLL thread, would be racy */
                ret = (attached && !sqd->thread) ? -ENXIO : 0;
                io_sq_thread_unpark(sqd);

                if (ret < 0)
                        goto err;
                if (attached)
                        return 0;

                if (p->flags & IORING_SETUP_SQ_AFF) {
                        int cpu = p->sq_thread_cpu;

                        ret = -EINVAL;
                        if (cpu >= nr_cpu_ids || !cpu_online(cpu))
                                goto err_sqpoll;
                        sqd->sq_cpu = cpu;
                } else {
                        sqd->sq_cpu = -1;
                }

                sqd->task_pid = current->pid;
                sqd->task_tgid = current->tgid;
                tsk = create_io_thread(io_sq_thread, sqd, NUMA_NO_NODE);
                if (IS_ERR(tsk)) {
                        ret = PTR_ERR(tsk);
                        goto err_sqpoll;
                }

                sqd->thread = tsk;
                ret = io_uring_alloc_task_context(tsk, ctx);
                wake_up_new_task(tsk);
                if (ret)
                        goto err;
        } else if (p->flags & IORING_SETUP_SQ_AFF) {
                /* Can't have SQ_AFF without SQPOLL */
                ret = -EINVAL;
                goto err;
        }

        return 0;
err_sqpoll:
        complete(&ctx->sq_data->exited);
err:
        io_sq_thread_finish(ctx);
        return ret;
}

static inline void __io_unaccount_mem(struct user_struct *user,
                                      unsigned long nr_pages)
{
        atomic_long_sub(nr_pages, &user->locked_vm);
}

static inline int __io_account_mem(struct user_struct *user,
                                   unsigned long nr_pages)
{
        unsigned long page_limit, cur_pages, new_pages;

        /* Don't allow more pages than we can safely lock */
        page_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;

        do {
                cur_pages = atomic_long_read(&user->locked_vm);
                new_pages = cur_pages + nr_pages;
                if (new_pages > page_limit)
                        return -ENOMEM;
        } while (atomic_long_cmpxchg(&user->locked_vm, cur_pages,
                                        new_pages) != cur_pages);

        return 0;
}

static void io_unaccount_mem(struct io_ring_ctx *ctx, unsigned long nr_pages)
{
        if (ctx->user)
                __io_unaccount_mem(ctx->user, nr_pages);

        if (ctx->mm_account)
                atomic64_sub(nr_pages, &ctx->mm_account->pinned_vm);
}

static int io_account_mem(struct io_ring_ctx *ctx, unsigned long nr_pages)
{
        int ret;

        if (ctx->user) {
                ret = __io_account_mem(ctx->user, nr_pages);
                if (ret)
                        return ret;
        }

        if (ctx->mm_account)
                atomic64_add(nr_pages, &ctx->mm_account->pinned_vm);

        return 0;
}

static void io_mem_free(void *ptr)
{
        struct page *page;

        if (!ptr)
                return;

        page = virt_to_head_page(ptr);
        if (put_page_testzero(page))
                free_compound_page(page);
}

static void *io_mem_alloc(size_t size)
{
        gfp_t gfp = GFP_KERNEL_ACCOUNT | __GFP_ZERO | __GFP_NOWARN | __GFP_COMP;

        return (void *) __get_free_pages(gfp, get_order(size));
}

static unsigned long rings_size(struct io_ring_ctx *ctx, unsigned int sq_entries,
                                unsigned int cq_entries, size_t *sq_offset)
{
        struct io_rings *rings;
        size_t off, sq_array_size;

        off = struct_size(rings, cqes, cq_entries);
        if (off == SIZE_MAX)
                return SIZE_MAX;
        if (ctx->flags & IORING_SETUP_CQE32) {
                if (check_shl_overflow(off, 1, &off))
                        return SIZE_MAX;
        }

#ifdef CONFIG_SMP
        off = ALIGN(off, SMP_CACHE_BYTES);
        if (off == 0)
                return SIZE_MAX;
#endif

        if (sq_offset)
                *sq_offset = off;

        sq_array_size = array_size(sizeof(u32), sq_entries);
        if (sq_array_size == SIZE_MAX)
                return SIZE_MAX;

        if (check_add_overflow(off, sq_array_size, &off))
                return SIZE_MAX;

        return off;
}

static void io_buffer_unmap(struct io_ring_ctx *ctx, struct io_mapped_ubuf **slot)
{
        struct io_mapped_ubuf *imu = *slot;
        unsigned int i;

        if (imu != ctx->dummy_ubuf) {
                for (i = 0; i < imu->nr_bvecs; i++)
                        unpin_user_page(imu->bvec[i].bv_page);
                if (imu->acct_pages)
                        io_unaccount_mem(ctx, imu->acct_pages);
                kvfree(imu);
        }
        *slot = NULL;
}

static void io_rsrc_buf_put(struct io_ring_ctx *ctx, struct io_rsrc_put *prsrc)
{
        io_buffer_unmap(ctx, &prsrc->buf);
        prsrc->buf = NULL;
}

static void __io_sqe_buffers_unregister(struct io_ring_ctx *ctx)
{
        unsigned int i;

        for (i = 0; i < ctx->nr_user_bufs; i++)
                io_buffer_unmap(ctx, &ctx->user_bufs[i]);
        kfree(ctx->user_bufs);
        io_rsrc_data_free(ctx->buf_data);
        ctx->user_bufs = NULL;
        ctx->buf_data = NULL;
        ctx->nr_user_bufs = 0;
}

static int io_sqe_buffers_unregister(struct io_ring_ctx *ctx)
{
        unsigned nr = ctx->nr_user_bufs;
        int ret;

        if (!ctx->buf_data)
                return -ENXIO;

        /*
         * Quiesce may unlock ->uring_lock, and while it's not held
         * prevent new requests using the table.
         */
        ctx->nr_user_bufs = 0;
        ret = io_rsrc_ref_quiesce(ctx->buf_data, ctx);
        ctx->nr_user_bufs = nr;
        if (!ret)
                __io_sqe_buffers_unregister(ctx);
        return ret;
}

static int io_copy_iov(struct io_ring_ctx *ctx, struct iovec *dst,
                       void __user *arg, unsigned index)
{
        struct iovec __user *src;

#ifdef CONFIG_COMPAT
        if (ctx->compat) {
                struct compat_iovec __user *ciovs;
                struct compat_iovec ciov;

                ciovs = (struct compat_iovec __user *) arg;
                if (copy_from_user(&ciov, &ciovs[index], sizeof(ciov)))
                        return -EFAULT;

                dst->iov_base = u64_to_user_ptr((u64)ciov.iov_base);
                dst->iov_len = ciov.iov_len;
                return 0;
        }
#endif
        src = (struct iovec __user *) arg;
        if (copy_from_user(dst, &src[index], sizeof(*dst)))
                return -EFAULT;
        return 0;
}

/*
 * Not super efficient, but this is just a registration time. And we do cache
 * the last compound head, so generally we'll only do a full search if we don't
 * match that one.
 *
 * We check if the given compound head page has already been accounted, to
 * avoid double accounting it. This allows us to account the full size of the
 * page, not just the constituent pages of a huge page.
 */
static bool headpage_already_acct(struct io_ring_ctx *ctx, struct page **pages,
                                  int nr_pages, struct page *hpage)
{
        int i, j;

        /* check current page array */
        for (i = 0; i < nr_pages; i++) {
                if (!PageCompound(pages[i]))
                        continue;
                if (compound_head(pages[i]) == hpage)
                        return true;
        }

        /* check previously registered pages */
        for (i = 0; i < ctx->nr_user_bufs; i++) {
                struct io_mapped_ubuf *imu = ctx->user_bufs[i];

                for (j = 0; j < imu->nr_bvecs; j++) {
                        if (!PageCompound(imu->bvec[j].bv_page))
                                continue;
                        if (compound_head(imu->bvec[j].bv_page) == hpage)
                                return true;
                }
        }

        return false;
}

static int io_buffer_account_pin(struct io_ring_ctx *ctx, struct page **pages,
                                 int nr_pages, struct io_mapped_ubuf *imu,
                                 struct page **last_hpage)
{
        int i, ret;

        imu->acct_pages = 0;
        for (i = 0; i < nr_pages; i++) {
                if (!PageCompound(pages[i])) {
                        imu->acct_pages++;
                } else {
                        struct page *hpage;

                        hpage = compound_head(pages[i]);
                        if (hpage == *last_hpage)
                                continue;
                        *last_hpage = hpage;
                        if (headpage_already_acct(ctx, pages, i, hpage))
                                continue;
                        imu->acct_pages += page_size(hpage) >> PAGE_SHIFT;
                }
        }

        if (!imu->acct_pages)
                return 0;

        ret = io_account_mem(ctx, imu->acct_pages);
        if (ret)
                imu->acct_pages = 0;
        return ret;
}

static struct page **io_pin_pages(unsigned long ubuf, unsigned long len,
                                  int *npages)
{
        unsigned long start, end, nr_pages;
        struct vm_area_struct **vmas = NULL;
        struct page **pages = NULL;
        int i, pret, ret = -ENOMEM;

        end = (ubuf + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
        start = ubuf >> PAGE_SHIFT;
        nr_pages = end - start;

        pages = kvmalloc_array(nr_pages, sizeof(struct page *), GFP_KERNEL);
        if (!pages)
                goto done;

        vmas = kvmalloc_array(nr_pages, sizeof(struct vm_area_struct *),
                              GFP_KERNEL);
        if (!vmas)
                goto done;

        ret = 0;
        mmap_read_lock(current->mm);
        pret = pin_user_pages(ubuf, nr_pages, FOLL_WRITE | FOLL_LONGTERM,
                              pages, vmas);
        if (pret == nr_pages) {
                /* don't support file backed memory */
                for (i = 0; i < nr_pages; i++) {
                        struct vm_area_struct *vma = vmas[i];

                        if (vma_is_shmem(vma))
                                continue;
                        if (vma->vm_file &&
                            !is_file_hugepages(vma->vm_file)) {
                                ret = -EOPNOTSUPP;
                                break;
                        }
                }
                *npages = nr_pages;
        } else {
                ret = pret < 0 ? pret : -EFAULT;
        }
        mmap_read_unlock(current->mm);
        if (ret) {
                /*
                 * if we did partial map, or found file backed vmas,
                 * release any pages we did get
                 */
                if (pret > 0)
                        unpin_user_pages(pages, pret);
                goto done;
        }
        ret = 0;
done:
        kvfree(vmas);
        if (ret < 0) {
                kvfree(pages);
                pages = ERR_PTR(ret);
        }
        return pages;
}

static int io_sqe_buffer_register(struct io_ring_ctx *ctx, struct iovec *iov,
                                  struct io_mapped_ubuf **pimu,
                                  struct page **last_hpage)
{
        struct io_mapped_ubuf *imu = NULL;
        struct page **pages = NULL;
        unsigned long off;
        size_t size;
        int ret, nr_pages, i;

        if (!iov->iov_base) {
                *pimu = ctx->dummy_ubuf;
                return 0;
        }

        *pimu = NULL;
        ret = -ENOMEM;

        pages = io_pin_pages((unsigned long) iov->iov_base, iov->iov_len,
                                &nr_pages);
        if (IS_ERR(pages)) {
                ret = PTR_ERR(pages);
                pages = NULL;
                goto done;
        }

        imu = kvmalloc(struct_size(imu, bvec, nr_pages), GFP_KERNEL);
        if (!imu)
                goto done;

        ret = io_buffer_account_pin(ctx, pages, nr_pages, imu, last_hpage);
        if (ret) {
                unpin_user_pages(pages, nr_pages);
                goto done;
        }

        off = (unsigned long) iov->iov_base & ~PAGE_MASK;
        size = iov->iov_len;
        for (i = 0; i < nr_pages; i++) {
                size_t vec_len;

                vec_len = min_t(size_t, size, PAGE_SIZE - off);
                imu->bvec[i].bv_page = pages[i];
                imu->bvec[i].bv_len = vec_len;
                imu->bvec[i].bv_offset = off;
                off = 0;
                size -= vec_len;
        }
        /* store original address for later verification */
        imu->ubuf = (unsigned long) iov->iov_base;
        imu->ubuf_end = imu->ubuf + iov->iov_len;
        imu->nr_bvecs = nr_pages;
        *pimu = imu;
        ret = 0;
done:
        if (ret)
                kvfree(imu);
        kvfree(pages);
        return ret;
}

static int io_buffers_map_alloc(struct io_ring_ctx *ctx, unsigned int nr_args)
{
        ctx->user_bufs = kcalloc(nr_args, sizeof(*ctx->user_bufs), GFP_KERNEL);
        return ctx->user_bufs ? 0 : -ENOMEM;
}

static int io_buffer_validate(struct iovec *iov)
{
        unsigned long tmp, acct_len = iov->iov_len + (PAGE_SIZE - 1);

        /*
         * Don't impose further limits on the size and buffer
         * constraints here, we'll -EINVAL later when IO is
         * submitted if they are wrong.
         */
        if (!iov->iov_base)
                return iov->iov_len ? -EFAULT : 0;
        if (!iov->iov_len)
                return -EFAULT;

        /* arbitrary limit, but we need something */
        if (iov->iov_len > SZ_1G)
                return -EFAULT;

        if (check_add_overflow((unsigned long)iov->iov_base, acct_len, &tmp))
                return -EOVERFLOW;

        return 0;
}

static int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
                                   unsigned int nr_args, u64 __user *tags)
{
        struct page *last_hpage = NULL;
        struct io_rsrc_data *data;
        int i, ret;
        struct iovec iov;

        if (ctx->user_bufs)
                return -EBUSY;
        if (!nr_args || nr_args > IORING_MAX_REG_BUFFERS)
                return -EINVAL;
        ret = io_rsrc_node_switch_start(ctx);
        if (ret)
                return ret;
        ret = io_rsrc_data_alloc(ctx, io_rsrc_buf_put, tags, nr_args, &data);
        if (ret)
                return ret;
        ret = io_buffers_map_alloc(ctx, nr_args);
        if (ret) {
                io_rsrc_data_free(data);
                return ret;
        }

        for (i = 0; i < nr_args; i++, ctx->nr_user_bufs++) {
                if (arg) {
                        ret = io_copy_iov(ctx, &iov, arg, i);
                        if (ret)
                                break;
                        ret = io_buffer_validate(&iov);
                        if (ret)
                                break;
                } else {
                        memset(&iov, 0, sizeof(iov));
                }

                if (!iov.iov_base && *io_get_tag_slot(data, i)) {
                        ret = -EINVAL;
                        break;
                }

                ret = io_sqe_buffer_register(ctx, &iov, &ctx->user_bufs[i],
                                             &last_hpage);
                if (ret)
                        break;
        }

        WARN_ON_ONCE(ctx->buf_data);

        ctx->buf_data = data;
        if (ret)
                __io_sqe_buffers_unregister(ctx);
        else
                io_rsrc_node_switch(ctx, NULL);
        return ret;
}

static int __io_sqe_buffers_update(struct io_ring_ctx *ctx,
                                   struct io_uring_rsrc_update2 *up,
                                   unsigned int nr_args)
{
        u64 __user *tags = u64_to_user_ptr(up->tags);
        struct iovec iov, __user *iovs = u64_to_user_ptr(up->data);
        struct page *last_hpage = NULL;
        bool needs_switch = false;
        __u32 done;
        int i, err;

        if (!ctx->buf_data)
                return -ENXIO;
        if (up->offset + nr_args > ctx->nr_user_bufs)
                return -EINVAL;

        for (done = 0; done < nr_args; done++) {
                struct io_mapped_ubuf *imu;
                int offset = up->offset + done;
                u64 tag = 0;

                err = io_copy_iov(ctx, &iov, iovs, done);
                if (err)
                        break;
                if (tags && copy_from_user(&tag, &tags[done], sizeof(tag))) {
                        err = -EFAULT;
                        break;
                }
                err = io_buffer_validate(&iov);
                if (err)
                        break;
                if (!iov.iov_base && tag) {
                        err = -EINVAL;
                        break;
                }
                err = io_sqe_buffer_register(ctx, &iov, &imu, &last_hpage);
                if (err)
                        break;

                i = array_index_nospec(offset, ctx->nr_user_bufs);
                if (ctx->user_bufs[i] != ctx->dummy_ubuf) {
                        err = io_queue_rsrc_removal(ctx->buf_data, i,
                                                    ctx->rsrc_node, ctx->user_bufs[i]);
                        if (unlikely(err)) {
                                io_buffer_unmap(ctx, &imu);
                                break;
                        }
                        ctx->user_bufs[i] = NULL;
                        needs_switch = true;
                }

                ctx->user_bufs[i] = imu;
                *io_get_tag_slot(ctx->buf_data, offset) = tag;
        }

        if (needs_switch)
                io_rsrc_node_switch(ctx, ctx->buf_data);
        return done ? done : err;
}

static int io_eventfd_register(struct io_ring_ctx *ctx, void __user *arg,
                               unsigned int eventfd_async)
{
        struct io_ev_fd *ev_fd;
        __s32 __user *fds = arg;
        int fd;

        ev_fd = rcu_dereference_protected(ctx->io_ev_fd,
                                        lockdep_is_held(&ctx->uring_lock));
        if (ev_fd)
                return -EBUSY;

        if (copy_from_user(&fd, fds, sizeof(*fds)))
                return -EFAULT;

        ev_fd = kmalloc(sizeof(*ev_fd), GFP_KERNEL);
        if (!ev_fd)
                return -ENOMEM;

        ev_fd->cq_ev_fd = eventfd_ctx_fdget(fd);
        if (IS_ERR(ev_fd->cq_ev_fd)) {
                int ret = PTR_ERR(ev_fd->cq_ev_fd);
                kfree(ev_fd);
                return ret;
        }
        ev_fd->eventfd_async = eventfd_async;
        ctx->has_evfd = true;
        rcu_assign_pointer(ctx->io_ev_fd, ev_fd);
        return 0;
}

static void io_eventfd_put(struct rcu_head *rcu)
{
        struct io_ev_fd *ev_fd = container_of(rcu, struct io_ev_fd, rcu);

        eventfd_ctx_put(ev_fd->cq_ev_fd);
        kfree(ev_fd);
}

static int io_eventfd_unregister(struct io_ring_ctx *ctx)
{
        struct io_ev_fd *ev_fd;

        ev_fd = rcu_dereference_protected(ctx->io_ev_fd,
                                        lockdep_is_held(&ctx->uring_lock));
        if (ev_fd) {
                ctx->has_evfd = false;
                rcu_assign_pointer(ctx->io_ev_fd, NULL);
                call_rcu(&ev_fd->rcu, io_eventfd_put);
                return 0;
        }

        return -ENXIO;
}

static void io_destroy_buffers(struct io_ring_ctx *ctx)
{
        struct io_buffer_list *bl;
        unsigned long index;
        int i;

        for (i = 0; i < BGID_ARRAY; i++) {
                if (!ctx->io_bl)
                        break;
                __io_remove_buffers(ctx, &ctx->io_bl[i], -1U);
        }

        xa_for_each(&ctx->io_bl_xa, index, bl) {
                xa_erase(&ctx->io_bl_xa, bl->bgid);
                __io_remove_buffers(ctx, bl, -1U);
                kfree(bl);
        }

        while (!list_empty(&ctx->io_buffers_pages)) {
                struct page *page;

                page = list_first_entry(&ctx->io_buffers_pages, struct page, lru);
                list_del_init(&page->lru);
                __free_page(page);
        }
}

static void io_req_caches_free(struct io_ring_ctx *ctx)
{
        struct io_submit_state *state = &ctx->submit_state;
        int nr = 0;

        mutex_lock(&ctx->uring_lock);
        io_flush_cached_locked_reqs(ctx, state);

        while (!io_req_cache_empty(ctx)) {
                struct io_wq_work_node *node;
                struct io_kiocb *req;

                node = wq_stack_extract(&state->free_list);
                req = container_of(node, struct io_kiocb, comp_list);
                kmem_cache_free(req_cachep, req);
                nr++;
        }
        if (nr)
                percpu_ref_put_many(&ctx->refs, nr);
        mutex_unlock(&ctx->uring_lock);
}

static void io_wait_rsrc_data(struct io_rsrc_data *data)
{
        if (data && !atomic_dec_and_test(&data->refs))
                wait_for_completion(&data->done);
}

static void io_flush_apoll_cache(struct io_ring_ctx *ctx)
{
        struct async_poll *apoll;

        while (!list_empty(&ctx->apoll_cache)) {
                apoll = list_first_entry(&ctx->apoll_cache, struct async_poll,
                                                poll.wait.entry);
                list_del(&apoll->poll.wait.entry);
                kfree(apoll);
        }
}

static __cold void io_ring_ctx_free(struct io_ring_ctx *ctx)
{
        io_sq_thread_finish(ctx);

        if (ctx->mm_account) {
                mmdrop(ctx->mm_account);
                ctx->mm_account = NULL;
        }

        io_rsrc_refs_drop(ctx);
        /* __io_rsrc_put_work() may need uring_lock to progress, wait w/o it */
        io_wait_rsrc_data(ctx->buf_data);
        io_wait_rsrc_data(ctx->file_data);

        mutex_lock(&ctx->uring_lock);
        if (ctx->buf_data)
                __io_sqe_buffers_unregister(ctx);
        if (ctx->file_data)
                __io_sqe_files_unregister(ctx);
        if (ctx->rings)
                __io_cqring_overflow_flush(ctx, true);
        io_eventfd_unregister(ctx);
        io_flush_apoll_cache(ctx);
        mutex_unlock(&ctx->uring_lock);
        io_destroy_buffers(ctx);
        if (ctx->sq_creds)
                put_cred(ctx->sq_creds);

        /* there are no registered resources left, nobody uses it */
        if (ctx->rsrc_node)
                io_rsrc_node_destroy(ctx->rsrc_node);
        if (ctx->rsrc_backup_node)
                io_rsrc_node_destroy(ctx->rsrc_backup_node);
        flush_delayed_work(&ctx->rsrc_put_work);
        flush_delayed_work(&ctx->fallback_work);

        WARN_ON_ONCE(!list_empty(&ctx->rsrc_ref_list));
        WARN_ON_ONCE(!llist_empty(&ctx->rsrc_put_llist));

#if defined(CONFIG_UNIX)
        if (ctx->ring_sock) {
                ctx->ring_sock->file = NULL; /* so that iput() is called */
                sock_release(ctx->ring_sock);
        }
#endif
        WARN_ON_ONCE(!list_empty(&ctx->ltimeout_list));

        io_mem_free(ctx->rings);
        io_mem_free(ctx->sq_sqes);

        percpu_ref_exit(&ctx->refs);
        free_uid(ctx->user);
        io_req_caches_free(ctx);
        if (ctx->hash_map)
                io_wq_put_hash(ctx->hash_map);
        kfree(ctx->cancel_hash);
        kfree(ctx->dummy_ubuf);
        kfree(ctx->io_bl);
        xa_destroy(&ctx->io_bl_xa);
        kfree(ctx);
}

static __poll_t io_uring_poll(struct file *file, poll_table *wait)
{
        struct io_ring_ctx *ctx = file->private_data;
        __poll_t mask = 0;

        poll_wait(file, &ctx->cq_wait, wait);
        /*
         * synchronizes with barrier from wq_has_sleeper call in
         * io_commit_cqring
         */
        smp_rmb();
        if (!io_sqring_full(ctx))
                mask |= EPOLLOUT | EPOLLWRNORM;

        /*
         * Don't flush cqring overflow list here, just do a simple check.
         * Otherwise there could possible be ABBA deadlock:
         *      CPU0                    CPU1
         *      ----                    ----
         * lock(&ctx->uring_lock);
         *                              lock(&ep->mtx);
         *                              lock(&ctx->uring_lock);
         * lock(&ep->mtx);
         *
         * Users may get EPOLLIN meanwhile seeing nothing in cqring, this
         * pushs them to do the flush.
         */
        if (io_cqring_events(ctx) ||
            test_bit(IO_CHECK_CQ_OVERFLOW_BIT, &ctx->check_cq))
                mask |= EPOLLIN | EPOLLRDNORM;

        return mask;
}

static int io_unregister_personality(struct io_ring_ctx *ctx, unsigned id)
{
        const struct cred *creds;

        creds = xa_erase(&ctx->personalities, id);
        if (creds) {
                put_cred(creds);
                return 0;
        }

        return -EINVAL;
}

struct io_tctx_exit {
        struct callback_head            task_work;
        struct completion               completion;
        struct io_ring_ctx              *ctx;
};

static __cold void io_tctx_exit_cb(struct callback_head *cb)
{
        struct io_uring_task *tctx = current->io_uring;
        struct io_tctx_exit *work;

        work = container_of(cb, struct io_tctx_exit, task_work);
        /*
         * When @in_idle, we're in cancellation and it's racy to remove the
         * node. It'll be removed by the end of cancellation, just ignore it.
         */
        if (!atomic_read(&tctx->in_idle))
                io_uring_del_tctx_node((unsigned long)work->ctx);
        complete(&work->completion);
}

static __cold bool io_cancel_ctx_cb(struct io_wq_work *work, void *data)
{
        struct io_kiocb *req = container_of(work, struct io_kiocb, work);

        return req->ctx == data;
}

static __cold void io_ring_exit_work(struct work_struct *work)
{
        struct io_ring_ctx *ctx = container_of(work, struct io_ring_ctx, exit_work);
        unsigned long timeout = jiffies + HZ * 60 * 5;
        unsigned long interval = HZ / 20;
        struct io_tctx_exit exit;
        struct io_tctx_node *node;
        int ret;

        /*
         * If we're doing polled IO and end up having requests being
         * submitted async (out-of-line), then completions can come in while
         * we're waiting for refs to drop. We need to reap these manually,
         * as nobody else will be looking for them.
         */
        do {
                io_uring_try_cancel_requests(ctx, NULL, true);
                if (ctx->sq_data) {
                        struct io_sq_data *sqd = ctx->sq_data;
                        struct task_struct *tsk;

                        io_sq_thread_park(sqd);
                        tsk = sqd->thread;
                        if (tsk && tsk->io_uring && tsk->io_uring->io_wq)
                                io_wq_cancel_cb(tsk->io_uring->io_wq,
                                                io_cancel_ctx_cb, ctx, true);
                        io_sq_thread_unpark(sqd);
                }

                io_req_caches_free(ctx);

                if (WARN_ON_ONCE(time_after(jiffies, timeout))) {
                        /* there is little hope left, don't run it too often */
                        interval = HZ * 60;
                }
        } while (!wait_for_completion_timeout(&ctx->ref_comp, interval));

        init_completion(&exit.completion);
        init_task_work(&exit.task_work, io_tctx_exit_cb);
        exit.ctx = ctx;
        /*
         * Some may use context even when all refs and requests have been put,
         * and they are free to do so while still holding uring_lock or
         * completion_lock, see io_req_task_submit(). Apart from other work,
         * this lock/unlock section also waits them to finish.
         */
        mutex_lock(&ctx->uring_lock);
        while (!list_empty(&ctx->tctx_list)) {
                WARN_ON_ONCE(time_after(jiffies, timeout));

                node = list_first_entry(&ctx->tctx_list, struct io_tctx_node,
                                        ctx_node);
                /* don't spin on a single task if cancellation failed */
                list_rotate_left(&ctx->tctx_list);
                ret = task_work_add(node->task, &exit.task_work, TWA_SIGNAL);
                if (WARN_ON_ONCE(ret))
                        continue;

                mutex_unlock(&ctx->uring_lock);
                wait_for_completion(&exit.completion);
                mutex_lock(&ctx->uring_lock);
        }
        mutex_unlock(&ctx->uring_lock);
        spin_lock(&ctx->completion_lock);
        spin_unlock(&ctx->completion_lock);

        io_ring_ctx_free(ctx);
}

static __cold void io_ring_ctx_wait_and_kill(struct io_ring_ctx *ctx)
{
        unsigned long index;
        struct creds *creds;

        mutex_lock(&ctx->uring_lock);
        percpu_ref_kill(&ctx->refs);
        if (ctx->rings)
                __io_cqring_overflow_flush(ctx, true);
        xa_for_each(&ctx->personalities, index, creds)
                io_unregister_personality(ctx, index);
        mutex_unlock(&ctx->uring_lock);

        /* failed during ring init, it couldn't have issued any requests */
        if (ctx->rings) {
                io_kill_timeouts(ctx, NULL, true);
                io_poll_remove_all(ctx, NULL, true);
                /* if we failed setting up the ctx, we might not have any rings */
                io_iopoll_try_reap_events(ctx);
        }

        INIT_WORK(&ctx->exit_work, io_ring_exit_work);
        /*
         * Use system_unbound_wq to avoid spawning tons of event kworkers
         * if we're exiting a ton of rings at the same time. It just adds
         * noise and overhead, there's no discernable change in runtime
         * over using system_wq.
         */
        queue_work(system_unbound_wq, &ctx->exit_work);
}

static int io_uring_release(struct inode *inode, struct file *file)
{
        struct io_ring_ctx *ctx = file->private_data;

        file->private_data = NULL;
        io_ring_ctx_wait_and_kill(ctx);
        return 0;
}

struct io_task_cancel {
        struct task_struct *task;
        bool all;
};

static bool io_cancel_task_cb(struct io_wq_work *work, void *data)
{
        struct io_kiocb *req = container_of(work, struct io_kiocb, work);
        struct io_task_cancel *cancel = data;

        return io_match_task_safe(req, cancel->task, cancel->all);
}

static __cold bool io_cancel_defer_files(struct io_ring_ctx *ctx,
                                         struct task_struct *task,
                                         bool cancel_all)
{
        struct io_defer_entry *de;
        LIST_HEAD(list);

        spin_lock(&ctx->completion_lock);
        list_for_each_entry_reverse(de, &ctx->defer_list, list) {
                if (io_match_task_safe(de->req, task, cancel_all)) {
                        list_cut_position(&list, &ctx->defer_list, &de->list);
                        break;
                }
        }
        spin_unlock(&ctx->completion_lock);
        if (list_empty(&list))
                return false;

        while (!list_empty(&list)) {
                de = list_first_entry(&list, struct io_defer_entry, list);
                list_del_init(&de->list);
                io_req_complete_failed(de->req, -ECANCELED);
                kfree(de);
        }
        return true;
}

static __cold bool io_uring_try_cancel_iowq(struct io_ring_ctx *ctx)
{
        struct io_tctx_node *node;
        enum io_wq_cancel cret;
        bool ret = false;

        mutex_lock(&ctx->uring_lock);
        list_for_each_entry(node, &ctx->tctx_list, ctx_node) {
                struct io_uring_task *tctx = node->task->io_uring;

                /*
                 * io_wq will stay alive while we hold uring_lock, because it's
                 * killed after ctx nodes, which requires to take the lock.
                 */
                if (!tctx || !tctx->io_wq)
                        continue;
                cret = io_wq_cancel_cb(tctx->io_wq, io_cancel_ctx_cb, ctx, true);
                ret |= (cret != IO_WQ_CANCEL_NOTFOUND);
        }
        mutex_unlock(&ctx->uring_lock);

        return ret;
}

static __cold void io_uring_try_cancel_requests(struct io_ring_ctx *ctx,
                                                struct task_struct *task,
                                                bool cancel_all)
{
        struct io_task_cancel cancel = { .task = task, .all = cancel_all, };
        struct io_uring_task *tctx = task ? task->io_uring : NULL;

        /* failed during ring init, it couldn't have issued any requests */
        if (!ctx->rings)
                return;

        while (1) {
                enum io_wq_cancel cret;
                bool ret = false;

                if (!task) {
                        ret |= io_uring_try_cancel_iowq(ctx);
                } else if (tctx && tctx->io_wq) {
                        /*
                         * Cancels requests of all rings, not only @ctx, but
                         * it's fine as the task is in exit/exec.
                         */
                        cret = io_wq_cancel_cb(tctx->io_wq, io_cancel_task_cb,
                                               &cancel, true);
                        ret |= (cret != IO_WQ_CANCEL_NOTFOUND);
                }

                /* SQPOLL thread does its own polling */
                if ((!(ctx->flags & IORING_SETUP_SQPOLL) && cancel_all) ||
                    (ctx->sq_data && ctx->sq_data->thread == current)) {
                        while (!wq_list_empty(&ctx->iopoll_list)) {
                                io_iopoll_try_reap_events(ctx);
                                ret = true;
                        }
                }

                ret |= io_cancel_defer_files(ctx, task, cancel_all);
                ret |= io_poll_remove_all(ctx, task, cancel_all);
                ret |= io_kill_timeouts(ctx, task, cancel_all);
                if (task)
                        ret |= io_run_task_work();
                if (!ret)
                        break;
                cond_resched();
        }
}

static int __io_uring_add_tctx_node(struct io_ring_ctx *ctx)
{
        struct io_uring_task *tctx = current->io_uring;
        struct io_tctx_node *node;
        int ret;

        if (unlikely(!tctx)) {
                ret = io_uring_alloc_task_context(current, ctx);
                if (unlikely(ret))
                        return ret;

                tctx = current->io_uring;
                if (ctx->iowq_limits_set) {
                        unsigned int limits[2] = { ctx->iowq_limits[0],
                                                   ctx->iowq_limits[1], };

                        ret = io_wq_max_workers(tctx->io_wq, limits);
                        if (ret)
                                return ret;
                }
        }
        if (!xa_load(&tctx->xa, (unsigned long)ctx)) {
                node = kmalloc(sizeof(*node), GFP_KERNEL);
                if (!node)
                        return -ENOMEM;
                node->ctx = ctx;
                node->task = current;

                ret = xa_err(xa_store(&tctx->xa, (unsigned long)ctx,
                                        node, GFP_KERNEL));
                if (ret) {
                        kfree(node);
                        return ret;
                }

                mutex_lock(&ctx->uring_lock);
                list_add(&node->ctx_node, &ctx->tctx_list);
                mutex_unlock(&ctx->uring_lock);
        }
        tctx->last = ctx;
        return 0;
}

/*
 * Note that this task has used io_uring. We use it for cancelation purposes.
 */
static inline int io_uring_add_tctx_node(struct io_ring_ctx *ctx)
{
        struct io_uring_task *tctx = current->io_uring;

        if (likely(tctx && tctx->last == ctx))
                return 0;
        return __io_uring_add_tctx_node(ctx);
}

/*
 * Remove this io_uring_file -> task mapping.
 */
static __cold void io_uring_del_tctx_node(unsigned long index)
{
        struct io_uring_task *tctx = current->io_uring;
        struct io_tctx_node *node;

        if (!tctx)
                return;
        node = xa_erase(&tctx->xa, index);
        if (!node)
                return;

        WARN_ON_ONCE(current != node->task);
        WARN_ON_ONCE(list_empty(&node->ctx_node));

        mutex_lock(&node->ctx->uring_lock);
        list_del(&node->ctx_node);
        mutex_unlock(&node->ctx->uring_lock);

        if (tctx->last == node->ctx)
                tctx->last = NULL;
        kfree(node);
}

static __cold void io_uring_clean_tctx(struct io_uring_task *tctx)
{
        struct io_wq *wq = tctx->io_wq;
        struct io_tctx_node *node;
        unsigned long index;

        xa_for_each(&tctx->xa, index, node) {
                io_uring_del_tctx_node(index);
                cond_resched();
        }
        if (wq) {
                /*
                 * Must be after io_uring_del_tctx_node() (removes nodes under
                 * uring_lock) to avoid race with io_uring_try_cancel_iowq().
                 */
                io_wq_put_and_exit(wq);
                tctx->io_wq = NULL;
        }
}

static s64 tctx_inflight(struct io_uring_task *tctx, bool tracked)
{
        if (tracked)
                return atomic_read(&tctx->inflight_tracked);
        return percpu_counter_sum(&tctx->inflight);
}

/*
 * Find any io_uring ctx that this task has registered or done IO on, and cancel
 * requests. @sqd should be not-null IFF it's an SQPOLL thread cancellation.
 */
static __cold void io_uring_cancel_generic(bool cancel_all,
                                           struct io_sq_data *sqd)
{
        struct io_uring_task *tctx = current->io_uring;
        struct io_ring_ctx *ctx;
        s64 inflight;
        DEFINE_WAIT(wait);

        WARN_ON_ONCE(sqd && sqd->thread != current);

        if (!current->io_uring)
                return;
        if (tctx->io_wq)
                io_wq_exit_start(tctx->io_wq);

        atomic_inc(&tctx->in_idle);
        do {
                io_uring_drop_tctx_refs(current);
                /* read completions before cancelations */
                inflight = tctx_inflight(tctx, !cancel_all);
                if (!inflight)
                        break;

                if (!sqd) {
                        struct io_tctx_node *node;
                        unsigned long index;

                        xa_for_each(&tctx->xa, index, node) {
                                /* sqpoll task will cancel all its requests */
                                if (node->ctx->sq_data)
                                        continue;
                                io_uring_try_cancel_requests(node->ctx, current,
                                                             cancel_all);
                        }
                } else {
                        list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
                                io_uring_try_cancel_requests(ctx, current,
                                                             cancel_all);
                }

                prepare_to_wait(&tctx->wait, &wait, TASK_INTERRUPTIBLE);
                io_run_task_work();
                io_uring_drop_tctx_refs(current);

                /*
                 * If we've seen completions, retry without waiting. This
                 * avoids a race where a completion comes in before we did
                 * prepare_to_wait().
                 */
                if (inflight == tctx_inflight(tctx, !cancel_all))
                        schedule();
                finish_wait(&tctx->wait, &wait);
        } while (1);

        io_uring_clean_tctx(tctx);
        if (cancel_all) {
                /*
                 * We shouldn't run task_works after cancel, so just leave
                 * ->in_idle set for normal exit.
                 */
                atomic_dec(&tctx->in_idle);
                /* for exec all current's requests should be gone, kill tctx */
                __io_uring_free(current);
        }
}

void __io_uring_cancel(bool cancel_all)
{
        io_uring_cancel_generic(cancel_all, NULL);
}

void io_uring_unreg_ringfd(void)
{
        struct io_uring_task *tctx = current->io_uring;
        int i;

        for (i = 0; i < IO_RINGFD_REG_MAX; i++) {
                if (tctx->registered_rings[i]) {
                        fput(tctx->registered_rings[i]);
                        tctx->registered_rings[i] = NULL;
                }
        }
}

static int io_ring_add_registered_fd(struct io_uring_task *tctx, int fd,
                                     int start, int end)
{
        struct file *file;
        int offset;

        for (offset = start; offset < end; offset++) {
                offset = array_index_nospec(offset, IO_RINGFD_REG_MAX);
                if (tctx->registered_rings[offset])
                        continue;

                file = fget(fd);
                if (!file) {
                        return -EBADF;
                } else if (file->f_op != &io_uring_fops) {
                        fput(file);
                        return -EOPNOTSUPP;
                }
                tctx->registered_rings[offset] = file;
                return offset;
        }

        return -EBUSY;
}

/*
 * Register a ring fd to avoid fdget/fdput for each io_uring_enter()
 * invocation. User passes in an array of struct io_uring_rsrc_update
 * with ->data set to the ring_fd, and ->offset given for the desired
 * index. If no index is desired, application may set ->offset == -1U
 * and we'll find an available index. Returns number of entries
 * successfully processed, or < 0 on error if none were processed.
 */
static int io_ringfd_register(struct io_ring_ctx *ctx, void __user *__arg,
                              unsigned nr_args)
{
        struct io_uring_rsrc_update __user *arg = __arg;
        struct io_uring_rsrc_update reg;
        struct io_uring_task *tctx;
        int ret, i;

        if (!nr_args || nr_args > IO_RINGFD_REG_MAX)
                return -EINVAL;

        mutex_unlock(&ctx->uring_lock);
        ret = io_uring_add_tctx_node(ctx);
        mutex_lock(&ctx->uring_lock);
        if (ret)
                return ret;

        tctx = current->io_uring;
        for (i = 0; i < nr_args; i++) {
                int start, end;

                if (copy_from_user(&reg, &arg[i], sizeof(reg))) {
                        ret = -EFAULT;
                        break;
                }

                if (reg.resv) {
                        ret = -EINVAL;
                        break;
                }

                if (reg.offset == -1U) {
                        start = 0;
                        end = IO_RINGFD_REG_MAX;
                } else {
                        if (reg.offset >= IO_RINGFD_REG_MAX) {
                                ret = -EINVAL;
                                break;
                        }
                        start = reg.offset;
                        end = start + 1;
                }

                ret = io_ring_add_registered_fd(tctx, reg.data, start, end);
                if (ret < 0)
                        break;

                reg.offset = ret;
                if (copy_to_user(&arg[i], &reg, sizeof(reg))) {
                        fput(tctx->registered_rings[reg.offset]);
                        tctx->registered_rings[reg.offset] = NULL;
                        ret = -EFAULT;
                        break;
                }
        }

        return i ? i : ret;
}

static int io_ringfd_unregister(struct io_ring_ctx *ctx, void __user *__arg,
                                unsigned nr_args)
{
        struct io_uring_rsrc_update __user *arg = __arg;
        struct io_uring_task *tctx = current->io_uring;
        struct io_uring_rsrc_update reg;
        int ret = 0, i;

        if (!nr_args || nr_args > IO_RINGFD_REG_MAX)
                return -EINVAL;
        if (!tctx)
                return 0;

        for (i = 0; i < nr_args; i++) {
                if (copy_from_user(&reg, &arg[i], sizeof(reg))) {
                        ret = -EFAULT;
                        break;
                }
                if (reg.resv || reg.data || reg.offset >= IO_RINGFD_REG_MAX) {
                        ret = -EINVAL;
                        break;
                }

                reg.offset = array_index_nospec(reg.offset, IO_RINGFD_REG_MAX);
                if (tctx->registered_rings[reg.offset]) {
                        fput(tctx->registered_rings[reg.offset]);
                        tctx->registered_rings[reg.offset] = NULL;
                }
        }

        return i ? i : ret;
}

static void *io_uring_validate_mmap_request(struct file *file,
                                            loff_t pgoff, size_t sz)
{
        struct io_ring_ctx *ctx = file->private_data;
        loff_t offset = pgoff << PAGE_SHIFT;
        struct page *page;
        void *ptr;

        switch (offset) {
        case IORING_OFF_SQ_RING:
        case IORING_OFF_CQ_RING:
                ptr = ctx->rings;
                break;
        case IORING_OFF_SQES:
                ptr = ctx->sq_sqes;
                break;
        default:
                return ERR_PTR(-EINVAL);
        }

        page = virt_to_head_page(ptr);
        if (sz > page_size(page))
                return ERR_PTR(-EINVAL);

        return ptr;
}

#ifdef CONFIG_MMU

static __cold int io_uring_mmap(struct file *file, struct vm_area_struct *vma)
{
        size_t sz = vma->vm_end - vma->vm_start;
        unsigned long pfn;
        void *ptr;

        ptr = io_uring_validate_mmap_request(file, vma->vm_pgoff, sz);
        if (IS_ERR(ptr))
                return PTR_ERR(ptr);

        pfn = virt_to_phys(ptr) >> PAGE_SHIFT;
        return remap_pfn_range(vma, vma->vm_start, pfn, sz, vma->vm_page_prot);
}

#else /* !CONFIG_MMU */

static int io_uring_mmap(struct file *file, struct vm_area_struct *vma)
{
        return vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 0 : -EINVAL;
}

static unsigned int io_uring_nommu_mmap_capabilities(struct file *file)
{
        return NOMMU_MAP_DIRECT | NOMMU_MAP_READ | NOMMU_MAP_WRITE;
}

static unsigned long io_uring_nommu_get_unmapped_area(struct file *file,
        unsigned long addr, unsigned long len,
        unsigned long pgoff, unsigned long flags)
{
        void *ptr;

        ptr = io_uring_validate_mmap_request(file, pgoff, len);
        if (IS_ERR(ptr))
                return PTR_ERR(ptr);

        return (unsigned long) ptr;
}

#endif /* !CONFIG_MMU */

static int io_sqpoll_wait_sq(struct io_ring_ctx *ctx)
{
        DEFINE_WAIT(wait);

        do {
                if (!io_sqring_full(ctx))
                        break;
                prepare_to_wait(&ctx->sqo_sq_wait, &wait, TASK_INTERRUPTIBLE);

                if (!io_sqring_full(ctx))
                        break;
                schedule();
        } while (!signal_pending(current));

        finish_wait(&ctx->sqo_sq_wait, &wait);
        return 0;
}

static int io_validate_ext_arg(unsigned flags, const void __user *argp, size_t argsz)
{
        if (flags & IORING_ENTER_EXT_ARG) {
                struct io_uring_getevents_arg arg;

                if (argsz != sizeof(arg))
                        return -EINVAL;
                if (copy_from_user(&arg, argp, sizeof(arg)))
                        return -EFAULT;
        }
        return 0;
}

static int io_get_ext_arg(unsigned flags, const void __user *argp, size_t *argsz,
                          struct __kernel_timespec __user **ts,
                          const sigset_t __user **sig)
{
        struct io_uring_getevents_arg arg;

        /*
         * If EXT_ARG isn't set, then we have no timespec and the argp pointer
         * is just a pointer to the sigset_t.
         */
        if (!(flags & IORING_ENTER_EXT_ARG)) {
                *sig = (const sigset_t __user *) argp;
                *ts = NULL;
                return 0;
        }

        /*
         * EXT_ARG is set - ensure we agree on the size of it and copy in our
         * timespec and sigset_t pointers if good.
         */
        if (*argsz != sizeof(arg))
                return -EINVAL;
        if (copy_from_user(&arg, argp, sizeof(arg)))
                return -EFAULT;
        if (arg.pad)
                return -EINVAL;
        *sig = u64_to_user_ptr(arg.sigmask);
        *argsz = arg.sigmask_sz;
        *ts = u64_to_user_ptr(arg.ts);
        return 0;
}

SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
                u32, min_complete, u32, flags, const void __user *, argp,
                size_t, argsz)
{
        struct io_ring_ctx *ctx;
        struct fd f;
        long ret;

        io_run_task_work();

        if (unlikely(flags & ~(IORING_ENTER_GETEVENTS | IORING_ENTER_SQ_WAKEUP |
                               IORING_ENTER_SQ_WAIT | IORING_ENTER_EXT_ARG |
                               IORING_ENTER_REGISTERED_RING)))
                return -EINVAL;

        /*
         * Ring fd has been registered via IORING_REGISTER_RING_FDS, we
         * need only dereference our task private array to find it.
         */
        if (flags & IORING_ENTER_REGISTERED_RING) {
                struct io_uring_task *tctx = current->io_uring;

                if (!tctx || fd >= IO_RINGFD_REG_MAX)
                        return -EINVAL;
                fd = array_index_nospec(fd, IO_RINGFD_REG_MAX);
                f.file = tctx->registered_rings[fd];
                f.flags = 0;
        } else {
                f = fdget(fd);
        }

        if (unlikely(!f.file))
                return -EBADF;

        ret = -EOPNOTSUPP;
        if (unlikely(f.file->f_op != &io_uring_fops))
                goto out_fput;

        ret = -ENXIO;
        ctx = f.file->private_data;
        if (unlikely(!percpu_ref_tryget(&ctx->refs)))
                goto out_fput;

        ret = -EBADFD;
        if (unlikely(ctx->flags & IORING_SETUP_R_DISABLED))
                goto out;

        /*
         * For SQ polling, the thread will do all submissions and completions.
         * Just return the requested submit count, and wake the thread if
         * we were asked to.
         */
        ret = 0;
        if (ctx->flags & IORING_SETUP_SQPOLL) {
                io_cqring_overflow_flush(ctx);

                if (unlikely(ctx->sq_data->thread == NULL)) {
                        ret = -EOWNERDEAD;
                        goto out;
                }
                if (flags & IORING_ENTER_SQ_WAKEUP)
                        wake_up(&ctx->sq_data->wait);
                if (flags & IORING_ENTER_SQ_WAIT) {
                        ret = io_sqpoll_wait_sq(ctx);
                        if (ret)
                                goto out;
                }
                ret = to_submit;
        } else if (to_submit) {
                ret = io_uring_add_tctx_node(ctx);
                if (unlikely(ret))
                        goto out;

                mutex_lock(&ctx->uring_lock);
                ret = io_submit_sqes(ctx, to_submit);
                if (ret != to_submit) {
                        mutex_unlock(&ctx->uring_lock);
                        goto out;
                }
                if ((flags & IORING_ENTER_GETEVENTS) && ctx->syscall_iopoll)
                        goto iopoll_locked;
                mutex_unlock(&ctx->uring_lock);
        }
        if (flags & IORING_ENTER_GETEVENTS) {
                int ret2;
                if (ctx->syscall_iopoll) {
                        /*
                         * We disallow the app entering submit/complete with
                         * polling, but we still need to lock the ring to
                         * prevent racing with polled issue that got punted to
                         * a workqueue.
                         */
                        mutex_lock(&ctx->uring_lock);
iopoll_locked:
                        ret2 = io_validate_ext_arg(flags, argp, argsz);
                        if (likely(!ret2)) {
                                min_complete = min(min_complete,
                                                   ctx->cq_entries);
                                ret2 = io_iopoll_check(ctx, min_complete);
                        }
                        mutex_unlock(&ctx->uring_lock);
                } else {
                        const sigset_t __user *sig;
                        struct __kernel_timespec __user *ts;

                        ret2 = io_get_ext_arg(flags, argp, &argsz, &ts, &sig);
                        if (likely(!ret2)) {
                                min_complete = min(min_complete,
                                                   ctx->cq_entries);
                                ret2 = io_cqring_wait(ctx, min_complete, sig,
                                                      argsz, ts);
                        }
                }

                if (!ret) {
                        ret = ret2;

                        /*
                         * EBADR indicates that one or more CQE were dropped.
                         * Once the user has been informed we can clear the bit
                         * as they are obviously ok with those drops.
                         */
                        if (unlikely(ret2 == -EBADR))
                                clear_bit(IO_CHECK_CQ_DROPPED_BIT,
                                          &ctx->check_cq);
                }
        }

out:
        percpu_ref_put(&ctx->refs);
out_fput:
        fdput(f);
        return ret;
}

#ifdef CONFIG_PROC_FS
static __cold int io_uring_show_cred(struct seq_file *m, unsigned int id,
                const struct cred *cred)
{
        struct user_namespace *uns = seq_user_ns(m);
        struct group_info *gi;
        kernel_cap_t cap;
        unsigned __capi;
        int g;

        seq_printf(m, "%5d\n", id);
        seq_put_decimal_ull(m, "\tUid:\t", from_kuid_munged(uns, cred->uid));
        seq_put_decimal_ull(m, "\t\t", from_kuid_munged(uns, cred->euid));
        seq_put_decimal_ull(m, "\t\t", from_kuid_munged(uns, cred->suid));
        seq_put_decimal_ull(m, "\t\t", from_kuid_munged(uns, cred->fsuid));
        seq_put_decimal_ull(m, "\n\tGid:\t", from_kgid_munged(uns, cred->gid));
        seq_put_decimal_ull(m, "\t\t", from_kgid_munged(uns, cred->egid));
        seq_put_decimal_ull(m, "\t\t", from_kgid_munged(uns, cred->sgid));
        seq_put_decimal_ull(m, "\t\t", from_kgid_munged(uns, cred->fsgid));
        seq_puts(m, "\n\tGroups:\t");
        gi = cred->group_info;
        for (g = 0; g < gi->ngroups; g++) {
                seq_put_decimal_ull(m, g ? " " : "",
                                        from_kgid_munged(uns, gi->gid[g]));
        }
        seq_puts(m, "\n\tCapEff:\t");
        cap = cred->cap_effective;
        CAP_FOR_EACH_U32(__capi)
                seq_put_hex_ll(m, NULL, cap.cap[CAP_LAST_U32 - __capi], 8);
        seq_putc(m, '\n');
        return 0;
}

static __cold void __io_uring_show_fdinfo(struct io_ring_ctx *ctx,
                                          struct seq_file *m)
{
        struct io_sq_data *sq = NULL;
        struct io_overflow_cqe *ocqe;
        struct io_rings *r = ctx->rings;
        unsigned int sq_mask = ctx->sq_entries - 1, cq_mask = ctx->cq_entries - 1;
        unsigned int sq_head = READ_ONCE(r->sq.head);
        unsigned int sq_tail = READ_ONCE(r->sq.tail);
        unsigned int cq_head = READ_ONCE(r->cq.head);
        unsigned int cq_tail = READ_ONCE(r->cq.tail);
        unsigned int cq_shift = 0;
        unsigned int sq_entries, cq_entries;
        bool has_lock;
        bool is_cqe32 = (ctx->flags & IORING_SETUP_CQE32);
        unsigned int i;

        if (is_cqe32)
                cq_shift = 1;

        /*
         * we may get imprecise sqe and cqe info if uring is actively running
         * since we get cached_sq_head and cached_cq_tail without uring_lock
         * and sq_tail and cq_head are changed by userspace. But it's ok since
         * we usually use these info when it is stuck.
         */
        seq_printf(m, "SqMask:\t0x%x\n", sq_mask);
        seq_printf(m, "SqHead:\t%u\n", sq_head);
        seq_printf(m, "SqTail:\t%u\n", sq_tail);
        seq_printf(m, "CachedSqHead:\t%u\n", ctx->cached_sq_head);
        seq_printf(m, "CqMask:\t0x%x\n", cq_mask);
        seq_printf(m, "CqHead:\t%u\n", cq_head);
        seq_printf(m, "CqTail:\t%u\n", cq_tail);
        seq_printf(m, "CachedCqTail:\t%u\n", ctx->cached_cq_tail);
        seq_printf(m, "SQEs:\t%u\n", sq_tail - ctx->cached_sq_head);
        sq_entries = min(sq_tail - sq_head, ctx->sq_entries);
        for (i = 0; i < sq_entries; i++) {
                unsigned int entry = i + sq_head;
                unsigned int sq_idx = READ_ONCE(ctx->sq_array[entry & sq_mask]);
                struct io_uring_sqe *sqe;

                if (sq_idx > sq_mask)
                        continue;
                sqe = &ctx->sq_sqes[sq_idx];
                seq_printf(m, "%5u: opcode:%d, fd:%d, flags:%x, user_data:%llu\n",
                           sq_idx, sqe->opcode, sqe->fd, sqe->flags,
                           sqe->user_data);
        }
        seq_printf(m, "CQEs:\t%u\n", cq_tail - cq_head);
        cq_entries = min(cq_tail - cq_head, ctx->cq_entries);
        for (i = 0; i < cq_entries; i++) {
                unsigned int entry = i + cq_head;
                struct io_uring_cqe *cqe = &r->cqes[(entry & cq_mask) << cq_shift];

                if (!is_cqe32) {
                        seq_printf(m, "%5u: user_data:%llu, res:%d, flag:%x\n",
                           entry & cq_mask, cqe->user_data, cqe->res,
                           cqe->flags);
                } else {
                        seq_printf(m, "%5u: user_data:%llu, res:%d, flag:%x, "
                                "extra1:%llu, extra2:%llu\n",
                                entry & cq_mask, cqe->user_data, cqe->res,
                                cqe->flags, cqe->big_cqe[0], cqe->big_cqe[1]);
                }
        }

        /*
         * Avoid ABBA deadlock between the seq lock and the io_uring mutex,
         * since fdinfo case grabs it in the opposite direction of normal use
         * cases. If we fail to get the lock, we just don't iterate any
         * structures that could be going away outside the io_uring mutex.
         */
        has_lock = mutex_trylock(&ctx->uring_lock);

        if (has_lock && (ctx->flags & IORING_SETUP_SQPOLL)) {
                sq = ctx->sq_data;
                if (!sq->thread)
                        sq = NULL;
        }

        seq_printf(m, "SqThread:\t%d\n", sq ? task_pid_nr(sq->thread) : -1);
        seq_printf(m, "SqThreadCpu:\t%d\n", sq ? task_cpu(sq->thread) : -1);
        seq_printf(m, "UserFiles:\t%u\n", ctx->nr_user_files);
        for (i = 0; has_lock && i < ctx->nr_user_files; i++) {
                struct file *f = io_file_from_index(ctx, i);

                if (f)
                        seq_printf(m, "%5u: %s\n", i, file_dentry(f)->d_iname);
                else
                        seq_printf(m, "%5u: <none>\n", i);
        }
        seq_printf(m, "UserBufs:\t%u\n", ctx->nr_user_bufs);
        for (i = 0; has_lock && i < ctx->nr_user_bufs; i++) {
                struct io_mapped_ubuf *buf = ctx->user_bufs[i];
                unsigned int len = buf->ubuf_end - buf->ubuf;

                seq_printf(m, "%5u: 0x%llx/%u\n", i, buf->ubuf, len);
        }
        if (has_lock && !xa_empty(&ctx->personalities)) {
                unsigned long index;
                const struct cred *cred;

                seq_printf(m, "Personalities:\n");
                xa_for_each(&ctx->personalities, index, cred)
                        io_uring_show_cred(m, index, cred);
        }
        if (has_lock)
                mutex_unlock(&ctx->uring_lock);

        seq_puts(m, "PollList:\n");
        spin_lock(&ctx->completion_lock);
        for (i = 0; i < (1U << ctx->cancel_hash_bits); i++) {
                struct hlist_head *list = &ctx->cancel_hash[i];
                struct io_kiocb *req;

                hlist_for_each_entry(req, list, hash_node)
                        seq_printf(m, "  op=%d, task_works=%d\n", req->opcode,
                                        task_work_pending(req->task));
        }

        seq_puts(m, "CqOverflowList:\n");
        list_for_each_entry(ocqe, &ctx->cq_overflow_list, list) {
                struct io_uring_cqe *cqe = &ocqe->cqe;

                seq_printf(m, "  user_data=%llu, res=%d, flags=%x\n",
                           cqe->user_data, cqe->res, cqe->flags);

        }

        spin_unlock(&ctx->completion_lock);
}

static __cold void io_uring_show_fdinfo(struct seq_file *m, struct file *f)
{
        struct io_ring_ctx *ctx = f->private_data;

        if (percpu_ref_tryget(&ctx->refs)) {
                __io_uring_show_fdinfo(ctx, m);
                percpu_ref_put(&ctx->refs);
        }
}
#endif

static const struct file_operations io_uring_fops = {
        .release        = io_uring_release,
        .mmap           = io_uring_mmap,
#ifndef CONFIG_MMU
        .get_unmapped_area = io_uring_nommu_get_unmapped_area,
        .mmap_capabilities = io_uring_nommu_mmap_capabilities,
#endif
        .poll           = io_uring_poll,
#ifdef CONFIG_PROC_FS
        .show_fdinfo    = io_uring_show_fdinfo,
#endif
};

static __cold int io_allocate_scq_urings(struct io_ring_ctx *ctx,
                                         struct io_uring_params *p)
{
        struct io_rings *rings;
        size_t size, sq_array_offset;

        /* make sure these are sane, as we already accounted them */
        ctx->sq_entries = p->sq_entries;
        ctx->cq_entries = p->cq_entries;

        size = rings_size(ctx, p->sq_entries, p->cq_entries, &sq_array_offset);
        if (size == SIZE_MAX)
                return -EOVERFLOW;

        rings = io_mem_alloc(size);
        if (!rings)
                return -ENOMEM;

        ctx->rings = rings;
        ctx->sq_array = (u32 *)((char *)rings + sq_array_offset);
        rings->sq_ring_mask = p->sq_entries - 1;
        rings->cq_ring_mask = p->cq_entries - 1;
        rings->sq_ring_entries = p->sq_entries;
        rings->cq_ring_entries = p->cq_entries;

        if (p->flags & IORING_SETUP_SQE128)
                size = array_size(2 * sizeof(struct io_uring_sqe), p->sq_entries);
        else
                size = array_size(sizeof(struct io_uring_sqe), p->sq_entries);
        if (size == SIZE_MAX) {
                io_mem_free(ctx->rings);
                ctx->rings = NULL;
                return -EOVERFLOW;
        }

        ctx->sq_sqes = io_mem_alloc(size);
        if (!ctx->sq_sqes) {
                io_mem_free(ctx->rings);
                ctx->rings = NULL;
                return -ENOMEM;
        }

        return 0;
}

static int io_uring_install_fd(struct io_ring_ctx *ctx, struct file *file)
{
        int ret, fd;

        fd = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
        if (fd < 0)
                return fd;

        ret = io_uring_add_tctx_node(ctx);
        if (ret) {
                put_unused_fd(fd);
                return ret;
        }
        fd_install(fd, file);
        return fd;
}

/*
 * Allocate an anonymous fd, this is what constitutes the application
 * visible backing of an io_uring instance. The application mmaps this
 * fd to gain access to the SQ/CQ ring details. If UNIX sockets are enabled,
 * we have to tie this fd to a socket for file garbage collection purposes.
 */
static struct file *io_uring_get_file(struct io_ring_ctx *ctx)
{
        struct file *file;
#if defined(CONFIG_UNIX)
        int ret;

        ret = sock_create_kern(&init_net, PF_UNIX, SOCK_RAW, IPPROTO_IP,
                                &ctx->ring_sock);
        if (ret)
                return ERR_PTR(ret);
#endif

        file = anon_inode_getfile_secure("[io_uring]", &io_uring_fops, ctx,
                                         O_RDWR | O_CLOEXEC, NULL);
#if defined(CONFIG_UNIX)
        if (IS_ERR(file)) {
                sock_release(ctx->ring_sock);
                ctx->ring_sock = NULL;
        } else {
                ctx->ring_sock->file = file;
        }
#endif
        return file;
}

static __cold int io_uring_create(unsigned entries, struct io_uring_params *p,
                                  struct io_uring_params __user *params)
{
        struct io_ring_ctx *ctx;
        struct file *file;
        int ret;

        if (!entries)
                return -EINVAL;
        if (entries > IORING_MAX_ENTRIES) {
                if (!(p->flags & IORING_SETUP_CLAMP))
                        return -EINVAL;
                entries = IORING_MAX_ENTRIES;
        }

        /*
         * Use twice as many entries for the CQ ring. It's possible for the
         * application to drive a higher depth than the size of the SQ ring,
         * since the sqes are only used at submission time. This allows for
         * some flexibility in overcommitting a bit. If the application has
         * set IORING_SETUP_CQSIZE, it will have passed in the desired number
         * of CQ ring entries manually.
         */
        p->sq_entries = roundup_pow_of_two(entries);
        if (p->flags & IORING_SETUP_CQSIZE) {
                /*
                 * If IORING_SETUP_CQSIZE is set, we do the same roundup
                 * to a power-of-two, if it isn't already. We do NOT impose
                 * any cq vs sq ring sizing.
                 */
                if (!p->cq_entries)
                        return -EINVAL;
                if (p->cq_entries > IORING_MAX_CQ_ENTRIES) {
                        if (!(p->flags & IORING_SETUP_CLAMP))
                                return -EINVAL;
                        p->cq_entries = IORING_MAX_CQ_ENTRIES;
                }
                p->cq_entries = roundup_pow_of_two(p->cq_entries);
                if (p->cq_entries < p->sq_entries)
                        return -EINVAL;
        } else {
                p->cq_entries = 2 * p->sq_entries;
        }

        ctx = io_ring_ctx_alloc(p);
        if (!ctx)
                return -ENOMEM;

        /*
         * When SETUP_IOPOLL and SETUP_SQPOLL are both enabled, user
         * space applications don't need to do io completion events
         * polling again, they can rely on io_sq_thread to do polling
         * work, which can reduce cpu usage and uring_lock contention.
         */
        if (ctx->flags & IORING_SETUP_IOPOLL &&
            !(ctx->flags & IORING_SETUP_SQPOLL))
                ctx->syscall_iopoll = 1;

        ctx->compat = in_compat_syscall();
        if (!capable(CAP_IPC_LOCK))
                ctx->user = get_uid(current_user());

        /*
         * For SQPOLL, we just need a wakeup, always. For !SQPOLL, if
         * COOP_TASKRUN is set, then IPIs are never needed by the app.
         */
        ret = -EINVAL;
        if (ctx->flags & IORING_SETUP_SQPOLL) {
                /* IPI related flags don't make sense with SQPOLL */
                if (ctx->flags & (IORING_SETUP_COOP_TASKRUN |
                                  IORING_SETUP_TASKRUN_FLAG))
                        goto err;
                ctx->notify_method = TWA_SIGNAL_NO_IPI;
        } else if (ctx->flags & IORING_SETUP_COOP_TASKRUN) {
                ctx->notify_method = TWA_SIGNAL_NO_IPI;
        } else {
                if (ctx->flags & IORING_SETUP_TASKRUN_FLAG)
                        goto err;
                ctx->notify_method = TWA_SIGNAL;
        }

        /*
         * This is just grabbed for accounting purposes. When a process exits,
         * the mm is exited and dropped before the files, hence we need to hang
         * on to this mm purely for the purposes of being able to unaccount
         * memory (locked/pinned vm). It's not used for anything else.
         */
        mmgrab(current->mm);
        ctx->mm_account = current->mm;

        ret = io_allocate_scq_urings(ctx, p);
        if (ret)
                goto err;

        ret = io_sq_offload_create(ctx, p);
        if (ret)
                goto err;
        /* always set a rsrc node */
        ret = io_rsrc_node_switch_start(ctx);
        if (ret)
                goto err;
        io_rsrc_node_switch(ctx, NULL);

        memset(&p->sq_off, 0, sizeof(p->sq_off));
        p->sq_off.head = offsetof(struct io_rings, sq.head);
        p->sq_off.tail = offsetof(struct io_rings, sq.tail);
        p->sq_off.ring_mask = offsetof(struct io_rings, sq_ring_mask);
        p->sq_off.ring_entries = offsetof(struct io_rings, sq_ring_entries);
        p->sq_off.flags = offsetof(struct io_rings, sq_flags);
        p->sq_off.dropped = offsetof(struct io_rings, sq_dropped);
        p->sq_off.array = (char *)ctx->sq_array - (char *)ctx->rings;

        memset(&p->cq_off, 0, sizeof(p->cq_off));
        p->cq_off.head = offsetof(struct io_rings, cq.head);
        p->cq_off.tail = offsetof(struct io_rings, cq.tail);
        p->cq_off.ring_mask = offsetof(struct io_rings, cq_ring_mask);
        p->cq_off.ring_entries = offsetof(struct io_rings, cq_ring_entries);
        p->cq_off.overflow = offsetof(struct io_rings, cq_overflow);
        p->cq_off.cqes = offsetof(struct io_rings, cqes);
        p->cq_off.flags = offsetof(struct io_rings, cq_flags);

        p->features = IORING_FEAT_SINGLE_MMAP | IORING_FEAT_NODROP |
                        IORING_FEAT_SUBMIT_STABLE | IORING_FEAT_RW_CUR_POS |
                        IORING_FEAT_CUR_PERSONALITY | IORING_FEAT_FAST_POLL |
                        IORING_FEAT_POLL_32BITS | IORING_FEAT_SQPOLL_NONFIXED |
                        IORING_FEAT_EXT_ARG | IORING_FEAT_NATIVE_WORKERS |
                        IORING_FEAT_RSRC_TAGS | IORING_FEAT_CQE_SKIP |
                        IORING_FEAT_LINKED_FILE;

        if (copy_to_user(params, p, sizeof(*p))) {
                ret = -EFAULT;
                goto err;
        }

        file = io_uring_get_file(ctx);
        if (IS_ERR(file)) {
                ret = PTR_ERR(file);
                goto err;
        }

        /*
         * Install ring fd as the very last thing, so we don't risk someone
         * having closed it before we finish setup
         */
        ret = io_uring_install_fd(ctx, file);
        if (ret < 0) {
                /* fput will clean it up */
                fput(file);
                return ret;
        }

        trace_io_uring_create(ret, ctx, p->sq_entries, p->cq_entries, p->flags);
        return ret;
err:
        io_ring_ctx_wait_and_kill(ctx);
        return ret;
}

/*
 * Sets up an aio uring context, and returns the fd. Applications asks for a
 * ring size, we return the actual sq/cq ring sizes (among other things) in the
 * params structure passed in.
 */
static long io_uring_setup(u32 entries, struct io_uring_params __user *params)
{
        struct io_uring_params p;
        int i;

        if (copy_from_user(&p, params, sizeof(p)))
                return -EFAULT;
        for (i = 0; i < ARRAY_SIZE(p.resv); i++) {
                if (p.resv[i])
                        return -EINVAL;
        }

        if (p.flags & ~(IORING_SETUP_IOPOLL | IORING_SETUP_SQPOLL |
                        IORING_SETUP_SQ_AFF | IORING_SETUP_CQSIZE |
                        IORING_SETUP_CLAMP | IORING_SETUP_ATTACH_WQ |
                        IORING_SETUP_R_DISABLED | IORING_SETUP_SUBMIT_ALL |
                        IORING_SETUP_COOP_TASKRUN | IORING_SETUP_TASKRUN_FLAG |
                        IORING_SETUP_SQE128 | IORING_SETUP_CQE32))
                return -EINVAL;

        return io_uring_create(entries, &p, params);
}

SYSCALL_DEFINE2(io_uring_setup, u32, entries,
                struct io_uring_params __user *, params)
{
        return io_uring_setup(entries, params);
}

static __cold int io_probe(struct io_ring_ctx *ctx, void __user *arg,
                           unsigned nr_args)
{
        struct io_uring_probe *p;
        size_t size;
        int i, ret;

        size = struct_size(p, ops, nr_args);
        if (size == SIZE_MAX)
                return -EOVERFLOW;
        p = kzalloc(size, GFP_KERNEL);
        if (!p)
                return -ENOMEM;

        ret = -EFAULT;
        if (copy_from_user(p, arg, size))
                goto out;
        ret = -EINVAL;
        if (memchr_inv(p, 0, size))
                goto out;

        p->last_op = IORING_OP_LAST - 1;
        if (nr_args > IORING_OP_LAST)
                nr_args = IORING_OP_LAST;

        for (i = 0; i < nr_args; i++) {
                p->ops[i].op = i;
                if (!io_op_defs[i].not_supported)
                        p->ops[i].flags = IO_URING_OP_SUPPORTED;
        }
        p->ops_len = i;

        ret = 0;
        if (copy_to_user(arg, p, size))
                ret = -EFAULT;
out:
        kfree(p);
        return ret;
}

static int io_register_personality(struct io_ring_ctx *ctx)
{
        const struct cred *creds;
        u32 id;
        int ret;

        creds = get_current_cred();

        ret = xa_alloc_cyclic(&ctx->personalities, &id, (void *)creds,
                        XA_LIMIT(0, USHRT_MAX), &ctx->pers_next, GFP_KERNEL);
        if (ret < 0) {
                put_cred(creds);
                return ret;
        }
        return id;
}

static __cold int io_register_restrictions(struct io_ring_ctx *ctx,
                                           void __user *arg, unsigned int nr_args)
{
        struct io_uring_restriction *res;
        size_t size;
        int i, ret;

        /* Restrictions allowed only if rings started disabled */
        if (!(ctx->flags & IORING_SETUP_R_DISABLED))
                return -EBADFD;

        /* We allow only a single restrictions registration */
        if (ctx->restrictions.registered)
                return -EBUSY;

        if (!arg || nr_args > IORING_MAX_RESTRICTIONS)
                return -EINVAL;

        size = array_size(nr_args, sizeof(*res));
        if (size == SIZE_MAX)
                return -EOVERFLOW;

        res = memdup_user(arg, size);
        if (IS_ERR(res))
                return PTR_ERR(res);

        ret = 0;

        for (i = 0; i < nr_args; i++) {
                switch (res[i].opcode) {
                case IORING_RESTRICTION_REGISTER_OP:
                        if (res[i].register_op >= IORING_REGISTER_LAST) {
                                ret = -EINVAL;
                                goto out;
                        }

                        __set_bit(res[i].register_op,
                                  ctx->restrictions.register_op);
                        break;
                case IORING_RESTRICTION_SQE_OP:
                        if (res[i].sqe_op >= IORING_OP_LAST) {
                                ret = -EINVAL;
                                goto out;
                        }

                        __set_bit(res[i].sqe_op, ctx->restrictions.sqe_op);
                        break;
                case IORING_RESTRICTION_SQE_FLAGS_ALLOWED:
                        ctx->restrictions.sqe_flags_allowed = res[i].sqe_flags;
                        break;
                case IORING_RESTRICTION_SQE_FLAGS_REQUIRED:
                        ctx->restrictions.sqe_flags_required = res[i].sqe_flags;
                        break;
                default:
                        ret = -EINVAL;
                        goto out;
                }
        }

out:
        /* Reset all restrictions if an error happened */
        if (ret != 0)
                memset(&ctx->restrictions, 0, sizeof(ctx->restrictions));
        else
                ctx->restrictions.registered = true;

        kfree(res);
        return ret;
}

static int io_register_enable_rings(struct io_ring_ctx *ctx)
{
        if (!(ctx->flags & IORING_SETUP_R_DISABLED))
                return -EBADFD;

        if (ctx->restrictions.registered)
                ctx->restricted = 1;

        ctx->flags &= ~IORING_SETUP_R_DISABLED;
        if (ctx->sq_data && wq_has_sleeper(&ctx->sq_data->wait))
                wake_up(&ctx->sq_data->wait);
        return 0;
}

static int __io_register_rsrc_update(struct io_ring_ctx *ctx, unsigned type,
                                     struct io_uring_rsrc_update2 *up,
                                     unsigned nr_args)
{
        __u32 tmp;
        int err;

        if (check_add_overflow(up->offset, nr_args, &tmp))
                return -EOVERFLOW;
        err = io_rsrc_node_switch_start(ctx);
        if (err)
                return err;

        switch (type) {
        case IORING_RSRC_FILE:
                return __io_sqe_files_update(ctx, up, nr_args);
        case IORING_RSRC_BUFFER:
                return __io_sqe_buffers_update(ctx, up, nr_args);
        }
        return -EINVAL;
}

static int io_register_files_update(struct io_ring_ctx *ctx, void __user *arg,
                                    unsigned nr_args)
{
        struct io_uring_rsrc_update2 up;

        if (!nr_args)
                return -EINVAL;
        memset(&up, 0, sizeof(up));
        if (copy_from_user(&up, arg, sizeof(struct io_uring_rsrc_update)))
                return -EFAULT;
        if (up.resv || up.resv2)
                return -EINVAL;
        return __io_register_rsrc_update(ctx, IORING_RSRC_FILE, &up, nr_args);
}

static int io_register_rsrc_update(struct io_ring_ctx *ctx, void __user *arg,
                                   unsigned size, unsigned type)
{
        struct io_uring_rsrc_update2 up;

        if (size != sizeof(up))
                return -EINVAL;
        if (copy_from_user(&up, arg, sizeof(up)))
                return -EFAULT;
        if (!up.nr || up.resv || up.resv2)
                return -EINVAL;
        return __io_register_rsrc_update(ctx, type, &up, up.nr);
}

static __cold int io_register_rsrc(struct io_ring_ctx *ctx, void __user *arg,
                            unsigned int size, unsigned int type)
{
        struct io_uring_rsrc_register rr;

        /* keep it extendible */
        if (size != sizeof(rr))
                return -EINVAL;

        memset(&rr, 0, sizeof(rr));
        if (copy_from_user(&rr, arg, size))
                return -EFAULT;
        if (!rr.nr || rr.resv2)
                return -EINVAL;
        if (rr.flags & ~IORING_RSRC_REGISTER_SPARSE)
                return -EINVAL;

        switch (type) {
        case IORING_RSRC_FILE:
                if (rr.flags & IORING_RSRC_REGISTER_SPARSE && rr.data)
                        break;
                return io_sqe_files_register(ctx, u64_to_user_ptr(rr.data),
                                             rr.nr, u64_to_user_ptr(rr.tags));
        case IORING_RSRC_BUFFER:
                if (rr.flags & IORING_RSRC_REGISTER_SPARSE && rr.data)
                        break;
                return io_sqe_buffers_register(ctx, u64_to_user_ptr(rr.data),
                                               rr.nr, u64_to_user_ptr(rr.tags));
        }
        return -EINVAL;
}

static __cold int io_register_iowq_aff(struct io_ring_ctx *ctx,
                                       void __user *arg, unsigned len)
{
        struct io_uring_task *tctx = current->io_uring;
        cpumask_var_t new_mask;
        int ret;

        if (!tctx || !tctx->io_wq)
                return -EINVAL;

        if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
                return -ENOMEM;

        cpumask_clear(new_mask);
        if (len > cpumask_size())
                len = cpumask_size();

        if (in_compat_syscall()) {
                ret = compat_get_bitmap(cpumask_bits(new_mask),
                                        (const compat_ulong_t __user *)arg,
                                        len * 8 /* CHAR_BIT */);
        } else {
                ret = copy_from_user(new_mask, arg, len);
        }

        if (ret) {
                free_cpumask_var(new_mask);
                return -EFAULT;
        }

        ret = io_wq_cpu_affinity(tctx->io_wq, new_mask);
        free_cpumask_var(new_mask);
        return ret;
}

static __cold int io_unregister_iowq_aff(struct io_ring_ctx *ctx)
{
        struct io_uring_task *tctx = current->io_uring;

        if (!tctx || !tctx->io_wq)
                return -EINVAL;

        return io_wq_cpu_affinity(tctx->io_wq, NULL);
}

static __cold int io_register_iowq_max_workers(struct io_ring_ctx *ctx,
                                               void __user *arg)
        __must_hold(&ctx->uring_lock)
{
        struct io_tctx_node *node;
        struct io_uring_task *tctx = NULL;
        struct io_sq_data *sqd = NULL;
        __u32 new_count[2];
        int i, ret;

        if (copy_from_user(new_count, arg, sizeof(new_count)))
                return -EFAULT;
        for (i = 0; i < ARRAY_SIZE(new_count); i++)
                if (new_count[i] > INT_MAX)
                        return -EINVAL;

        if (ctx->flags & IORING_SETUP_SQPOLL) {
                sqd = ctx->sq_data;
                if (sqd) {
                        /*
                         * Observe the correct sqd->lock -> ctx->uring_lock
                         * ordering. Fine to drop uring_lock here, we hold
                         * a ref to the ctx.
                         */
                        refcount_inc(&sqd->refs);
                        mutex_unlock(&ctx->uring_lock);
                        mutex_lock(&sqd->lock);
                        mutex_lock(&ctx->uring_lock);
                        if (sqd->thread)
                                tctx = sqd->thread->io_uring;
                }
        } else {
                tctx = current->io_uring;
        }

        BUILD_BUG_ON(sizeof(new_count) != sizeof(ctx->iowq_limits));

        for (i = 0; i < ARRAY_SIZE(new_count); i++)
                if (new_count[i])
                        ctx->iowq_limits[i] = new_count[i];
        ctx->iowq_limits_set = true;

        if (tctx && tctx->io_wq) {
                ret = io_wq_max_workers(tctx->io_wq, new_count);
                if (ret)
                        goto err;
        } else {
                memset(new_count, 0, sizeof(new_count));
        }

        if (sqd) {
                mutex_unlock(&sqd->lock);
                io_put_sq_data(sqd);
        }

        if (copy_to_user(arg, new_count, sizeof(new_count)))
                return -EFAULT;

        /* that's it for SQPOLL, only the SQPOLL task creates requests */
        if (sqd)
                return 0;

        /* now propagate the restriction to all registered users */
        list_for_each_entry(node, &ctx->tctx_list, ctx_node) {
                struct io_uring_task *tctx = node->task->io_uring;

                if (WARN_ON_ONCE(!tctx->io_wq))
                        continue;

                for (i = 0; i < ARRAY_SIZE(new_count); i++)
                        new_count[i] = ctx->iowq_limits[i];
                /* ignore errors, it always returns zero anyway */
                (void)io_wq_max_workers(tctx->io_wq, new_count);
        }
        return 0;
err:
        if (sqd) {
                mutex_unlock(&sqd->lock);
                io_put_sq_data(sqd);
        }
        return ret;
}

static int io_register_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
{
        struct io_uring_buf_ring *br;
        struct io_uring_buf_reg reg;
        struct io_buffer_list *bl, *free_bl = NULL;
        struct page **pages;
        int nr_pages;

        if (copy_from_user(&reg, arg, sizeof(reg)))
                return -EFAULT;

        if (reg.pad || reg.resv[0] || reg.resv[1] || reg.resv[2])
                return -EINVAL;
        if (!reg.ring_addr)
                return -EFAULT;
        if (reg.ring_addr & ~PAGE_MASK)
                return -EINVAL;
        if (!is_power_of_2(reg.ring_entries))
                return -EINVAL;

        /* cannot disambiguate full vs empty due to head/tail size */
        if (reg.ring_entries >= 65536)
                return -EINVAL;

        if (unlikely(reg.bgid < BGID_ARRAY && !ctx->io_bl)) {
                int ret = io_init_bl_list(ctx);
                if (ret)
                        return ret;
        }

        bl = io_buffer_get_list(ctx, reg.bgid);
        if (bl) {
                /* if mapped buffer ring OR classic exists, don't allow */
                if (bl->buf_nr_pages || !list_empty(&bl->buf_list))
                        return -EEXIST;
        } else {
                free_bl = bl = kzalloc(sizeof(*bl), GFP_KERNEL);
                if (!bl)
                        return -ENOMEM;
        }

        pages = io_pin_pages(reg.ring_addr,
                             struct_size(br, bufs, reg.ring_entries),
                             &nr_pages);
        if (IS_ERR(pages)) {
                kfree(free_bl);
                return PTR_ERR(pages);
        }

        br = page_address(pages[0]);
        bl->buf_pages = pages;
        bl->buf_nr_pages = nr_pages;
        bl->nr_entries = reg.ring_entries;
        bl->buf_ring = br;
        bl->mask = reg.ring_entries - 1;
        io_buffer_add_list(ctx, bl, reg.bgid);
        return 0;
}

static int io_unregister_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
{
        struct io_uring_buf_reg reg;
        struct io_buffer_list *bl;

        if (copy_from_user(&reg, arg, sizeof(reg)))
                return -EFAULT;
        if (reg.pad || reg.resv[0] || reg.resv[1] || reg.resv[2])
                return -EINVAL;

        bl = io_buffer_get_list(ctx, reg.bgid);
        if (!bl)
                return -ENOENT;
        if (!bl->buf_nr_pages)
                return -EINVAL;

        __io_remove_buffers(ctx, bl, -1U);
        if (bl->bgid >= BGID_ARRAY) {
                xa_erase(&ctx->io_bl_xa, bl->bgid);
                kfree(bl);
        }
        return 0;
}

static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
                               void __user *arg, unsigned nr_args)
        __releases(ctx->uring_lock)
        __acquires(ctx->uring_lock)
{
        int ret;

        /*
         * We're inside the ring mutex, if the ref is already dying, then
         * someone else killed the ctx or is already going through
         * io_uring_register().
         */
        if (percpu_ref_is_dying(&ctx->refs))
                return -ENXIO;

        if (ctx->restricted) {
                if (opcode >= IORING_REGISTER_LAST)
                        return -EINVAL;
                opcode = array_index_nospec(opcode, IORING_REGISTER_LAST);
                if (!test_bit(opcode, ctx->restrictions.register_op))
                        return -EACCES;
        }

        switch (opcode) {
        case IORING_REGISTER_BUFFERS:
                ret = -EFAULT;
                if (!arg)
                        break;
                ret = io_sqe_buffers_register(ctx, arg, nr_args, NULL);
                break;
        case IORING_UNREGISTER_BUFFERS:
                ret = -EINVAL;
                if (arg || nr_args)
                        break;
                ret = io_sqe_buffers_unregister(ctx);
                break;
        case IORING_REGISTER_FILES:
                ret = -EFAULT;
                if (!arg)
                        break;
                ret = io_sqe_files_register(ctx, arg, nr_args, NULL);
                break;
        case IORING_UNREGISTER_FILES:
                ret = -EINVAL;
                if (arg || nr_args)
                        break;
                ret = io_sqe_files_unregister(ctx);
                break;
        case IORING_REGISTER_FILES_UPDATE:
                ret = io_register_files_update(ctx, arg, nr_args);
                break;
        case IORING_REGISTER_EVENTFD:
                ret = -EINVAL;
                if (nr_args != 1)
                        break;
                ret = io_eventfd_register(ctx, arg, 0);
                break;
        case IORING_REGISTER_EVENTFD_ASYNC:
                ret = -EINVAL;
                if (nr_args != 1)
                        break;
                ret = io_eventfd_register(ctx, arg, 1);
                break;
        case IORING_UNREGISTER_EVENTFD:
                ret = -EINVAL;
                if (arg || nr_args)
                        break;
                ret = io_eventfd_unregister(ctx);
                break;
        case IORING_REGISTER_PROBE:
                ret = -EINVAL;
                if (!arg || nr_args > 256)
                        break;
                ret = io_probe(ctx, arg, nr_args);
                break;
        case IORING_REGISTER_PERSONALITY:
                ret = -EINVAL;
                if (arg || nr_args)
                        break;
                ret = io_register_personality(ctx);
                break;
        case IORING_UNREGISTER_PERSONALITY:
                ret = -EINVAL;
                if (arg)
                        break;
                ret = io_unregister_personality(ctx, nr_args);
                break;
        case IORING_REGISTER_ENABLE_RINGS:
                ret = -EINVAL;
                if (arg || nr_args)
                        break;
                ret = io_register_enable_rings(ctx);
                break;
        case IORING_REGISTER_RESTRICTIONS:
                ret = io_register_restrictions(ctx, arg, nr_args);
                break;
        case IORING_REGISTER_FILES2:
                ret = io_register_rsrc(ctx, arg, nr_args, IORING_RSRC_FILE);
                break;
        case IORING_REGISTER_FILES_UPDATE2:
                ret = io_register_rsrc_update(ctx, arg, nr_args,
                                              IORING_RSRC_FILE);
                break;
        case IORING_REGISTER_BUFFERS2:
                ret = io_register_rsrc(ctx, arg, nr_args, IORING_RSRC_BUFFER);
                break;
        case IORING_REGISTER_BUFFERS_UPDATE:
                ret = io_register_rsrc_update(ctx, arg, nr_args,
                                              IORING_RSRC_BUFFER);
                break;
        case IORING_REGISTER_IOWQ_AFF:
                ret = -EINVAL;
                if (!arg || !nr_args)
                        break;
                ret = io_register_iowq_aff(ctx, arg, nr_args);
                break;
        case IORING_UNREGISTER_IOWQ_AFF:
                ret = -EINVAL;
                if (arg || nr_args)
                        break;
                ret = io_unregister_iowq_aff(ctx);
                break;
        case IORING_REGISTER_IOWQ_MAX_WORKERS:
                ret = -EINVAL;
                if (!arg || nr_args != 2)
                        break;
                ret = io_register_iowq_max_workers(ctx, arg);
                break;
        case IORING_REGISTER_RING_FDS:
                ret = io_ringfd_register(ctx, arg, nr_args);
                break;
        case IORING_UNREGISTER_RING_FDS:
                ret = io_ringfd_unregister(ctx, arg, nr_args);
                break;
        case IORING_REGISTER_PBUF_RING:
                ret = -EINVAL;
                if (!arg || nr_args != 1)
                        break;
                ret = io_register_pbuf_ring(ctx, arg);
                break;
        case IORING_UNREGISTER_PBUF_RING:
                ret = -EINVAL;
                if (!arg || nr_args != 1)
                        break;
                ret = io_unregister_pbuf_ring(ctx, arg);
                break;
        default:
                ret = -EINVAL;
                break;
        }

        return ret;
}

SYSCALL_DEFINE4(io_uring_register, unsigned int, fd, unsigned int, opcode,
                void __user *, arg, unsigned int, nr_args)
{
        struct io_ring_ctx *ctx;
        long ret = -EBADF;
        struct fd f;

        f = fdget(fd);
        if (!f.file)
                return -EBADF;

        ret = -EOPNOTSUPP;
        if (f.file->f_op != &io_uring_fops)
                goto out_fput;

        ctx = f.file->private_data;

        io_run_task_work();

        mutex_lock(&ctx->uring_lock);
        ret = __io_uring_register(ctx, opcode, arg, nr_args);
        mutex_unlock(&ctx->uring_lock);
        trace_io_uring_register(ctx, opcode, ctx->nr_user_files, ctx->nr_user_bufs, ret);
out_fput:
        fdput(f);
        return ret;
}

static int io_no_issue(struct io_kiocb *req, unsigned int issue_flags)
{
        WARN_ON_ONCE(1);
        return -ECANCELED;
}

static const struct io_op_def io_op_defs[] = {
        [IORING_OP_NOP] = {
                .audit_skip             = 1,
                .iopoll                 = 1,
                .prep                   = io_nop_prep,
                .issue                  = io_nop,
        },
        [IORING_OP_READV] = {
                .needs_file             = 1,
                .unbound_nonreg_file    = 1,
                .pollin                 = 1,
                .buffer_select          = 1,
                .plug                   = 1,
                .audit_skip             = 1,
                .ioprio                 = 1,
                .iopoll                 = 1,
                .async_size             = sizeof(struct io_async_rw),
                .prep                   = io_prep_rw,
                .issue                  = io_read,
                .prep_async             = io_readv_prep_async,
                .cleanup                = io_readv_writev_cleanup,
        },
        [IORING_OP_WRITEV] = {
                .needs_file             = 1,
                .hash_reg_file          = 1,
                .unbound_nonreg_file    = 1,
                .pollout                = 1,
                .plug                   = 1,
                .audit_skip             = 1,
                .ioprio                 = 1,
                .iopoll                 = 1,
                .async_size             = sizeof(struct io_async_rw),
                .prep                   = io_prep_rw,
                .issue                  = io_write,
                .prep_async             = io_writev_prep_async,
                .cleanup                = io_readv_writev_cleanup,
        },
        [IORING_OP_FSYNC] = {
                .needs_file             = 1,
                .audit_skip             = 1,
                .prep                   = io_fsync_prep,
                .issue                  = io_fsync,
        },
        [IORING_OP_READ_FIXED] = {
                .needs_file             = 1,
                .unbound_nonreg_file    = 1,
                .pollin                 = 1,
                .plug                   = 1,
                .audit_skip             = 1,
                .ioprio                 = 1,
                .iopoll                 = 1,
                .async_size             = sizeof(struct io_async_rw),
                .prep                   = io_prep_rw,
                .issue                  = io_read,
        },
        [IORING_OP_WRITE_FIXED] = {
                .needs_file             = 1,
                .hash_reg_file          = 1,
                .unbound_nonreg_file    = 1,
                .pollout                = 1,
                .plug                   = 1,
                .audit_skip             = 1,
                .ioprio                 = 1,
                .iopoll                 = 1,
                .async_size             = sizeof(struct io_async_rw),
                .prep                   = io_prep_rw,
                .issue                  = io_write,
        },
        [IORING_OP_POLL_ADD] = {
                .needs_file             = 1,
                .unbound_nonreg_file    = 1,
                .audit_skip             = 1,
                .prep                   = io_poll_add_prep,
                .issue                  = io_poll_add,
        },
        [IORING_OP_POLL_REMOVE] = {
                .audit_skip             = 1,
                .prep                   = io_poll_remove_prep,
                .issue                  = io_poll_remove,
        },
        [IORING_OP_SYNC_FILE_RANGE] = {
                .needs_file             = 1,
                .audit_skip             = 1,
                .prep                   = io_sfr_prep,
                .issue                  = io_sync_file_range,
        },
        [IORING_OP_SENDMSG] = {
                .needs_file             = 1,
                .unbound_nonreg_file    = 1,
                .pollout                = 1,
                .ioprio                 = 1,
#if defined(CONFIG_NET)
                .async_size             = sizeof(struct io_async_msghdr),
                .prep                   = io_sendmsg_prep,
                .issue                  = io_sendmsg,
                .prep_async             = io_sendmsg_prep_async,
                .cleanup                = io_sendmsg_recvmsg_cleanup,
#else
                .prep                   = io_eopnotsupp_prep,
#endif
        },
        [IORING_OP_RECVMSG] = {
                .needs_file             = 1,
                .unbound_nonreg_file    = 1,
                .pollin                 = 1,
                .buffer_select          = 1,
                .ioprio                 = 1,
#if defined(CONFIG_NET)
                .async_size             = sizeof(struct io_async_msghdr),
                .prep                   = io_recvmsg_prep,
                .issue                  = io_recvmsg,
                .prep_async             = io_recvmsg_prep_async,
                .cleanup                = io_sendmsg_recvmsg_cleanup,
#else
                .prep                   = io_eopnotsupp_prep,
#endif
        },
        [IORING_OP_TIMEOUT] = {
                .audit_skip             = 1,
                .async_size             = sizeof(struct io_timeout_data),
                .prep                   = io_timeout_prep,
                .issue                  = io_timeout,
        },
        [IORING_OP_TIMEOUT_REMOVE] = {
                /* used by timeout updates' prep() */
                .audit_skip             = 1,
                .prep                   = io_timeout_remove_prep,
                .issue                  = io_timeout_remove,
        },
        [IORING_OP_ACCEPT] = {
                .needs_file             = 1,
                .unbound_nonreg_file    = 1,
                .pollin                 = 1,
                .poll_exclusive         = 1,
                .ioprio                 = 1,    /* used for flags */
#if defined(CONFIG_NET)
                .prep                   = io_accept_prep,
                .issue                  = io_accept,
#else
                .prep                   = io_eopnotsupp_prep,
#endif
        },
        [IORING_OP_ASYNC_CANCEL] = {
                .audit_skip             = 1,
                .prep                   = io_async_cancel_prep,
                .issue                  = io_async_cancel,
        },
        [IORING_OP_LINK_TIMEOUT] = {
                .audit_skip             = 1,
                .async_size             = sizeof(struct io_timeout_data),
                .prep                   = io_link_timeout_prep,
                .issue                  = io_no_issue,
        },
        [IORING_OP_CONNECT] = {
                .needs_file             = 1,
                .unbound_nonreg_file    = 1,
                .pollout                = 1,
#if defined(CONFIG_NET)
                .async_size             = sizeof(struct io_async_connect),
                .prep                   = io_connect_prep,
                .issue                  = io_connect,
                .prep_async             = io_connect_prep_async,
#else
                .prep                   = io_eopnotsupp_prep,
#endif
        },
        [IORING_OP_FALLOCATE] = {
                .needs_file             = 1,
                .prep                   = io_fallocate_prep,
                .issue                  = io_fallocate,
        },
        [IORING_OP_OPENAT] = {
                .prep                   = io_openat_prep,
                .issue                  = io_openat,
                .cleanup                = io_open_cleanup,
        },
        [IORING_OP_CLOSE] = {
                .prep                   = io_close_prep,
                .issue                  = io_close,
        },
        [IORING_OP_FILES_UPDATE] = {
                .audit_skip             = 1,
                .iopoll                 = 1,
                .prep                   = io_files_update_prep,
                .issue                  = io_files_update,
        },
        [IORING_OP_STATX] = {
                .audit_skip             = 1,
                .prep                   = io_statx_prep,
                .issue                  = io_statx,
                .cleanup                = io_statx_cleanup,
        },
        [IORING_OP_READ] = {
                .needs_file             = 1,
                .unbound_nonreg_file    = 1,
                .pollin                 = 1,
                .buffer_select          = 1,
                .plug                   = 1,
                .audit_skip             = 1,
                .ioprio                 = 1,
                .iopoll                 = 1,
                .async_size             = sizeof(struct io_async_rw),
                .prep                   = io_prep_rw,
                .issue                  = io_read,
        },
        [IORING_OP_WRITE] = {
                .needs_file             = 1,
                .hash_reg_file          = 1,
                .unbound_nonreg_file    = 1,
                .pollout                = 1,
                .plug                   = 1,
                .audit_skip             = 1,
                .ioprio                 = 1,
                .iopoll                 = 1,
                .async_size             = sizeof(struct io_async_rw),
                .prep                   = io_prep_rw,
                .issue                  = io_write,
        },
        [IORING_OP_FADVISE] = {
                .needs_file             = 1,
                .audit_skip             = 1,
                .prep                   = io_fadvise_prep,
                .issue                  = io_fadvise,
        },
        [IORING_OP_MADVISE] = {
                .prep                   = io_madvise_prep,
                .issue                  = io_madvise,
        },
        [IORING_OP_SEND] = {
                .needs_file             = 1,
                .unbound_nonreg_file    = 1,
                .pollout                = 1,
                .audit_skip             = 1,
                .ioprio                 = 1,
#if defined(CONFIG_NET)
                .prep                   = io_sendmsg_prep,
                .issue                  = io_send,
#else
                .prep                   = io_eopnotsupp_prep,
#endif
        },
        [IORING_OP_RECV] = {
                .needs_file             = 1,
                .unbound_nonreg_file    = 1,
                .pollin                 = 1,
                .buffer_select          = 1,
                .audit_skip             = 1,
                .ioprio                 = 1,
#if defined(CONFIG_NET)
                .prep                   = io_recvmsg_prep,
                .issue                  = io_recv,
#else
                .prep                   = io_eopnotsupp_prep,
#endif
        },
        [IORING_OP_OPENAT2] = {
                .prep                   = io_openat2_prep,
                .issue                  = io_openat2,
                .cleanup                = io_open_cleanup,
        },
        [IORING_OP_EPOLL_CTL] = {
                .unbound_nonreg_file    = 1,
                .audit_skip             = 1,
#if defined(CONFIG_EPOLL)
                .prep                   = io_epoll_ctl_prep,
                .issue                  = io_epoll_ctl,
#else
                .prep                   = io_eopnotsupp_prep,
#endif
        },
        [IORING_OP_SPLICE] = {
                .needs_file             = 1,
                .hash_reg_file          = 1,
                .unbound_nonreg_file    = 1,
                .audit_skip             = 1,
                .prep                   = io_splice_prep,
                .issue                  = io_splice,
        },
        [IORING_OP_PROVIDE_BUFFERS] = {
                .audit_skip             = 1,
                .iopoll                 = 1,
                .prep                   = io_provide_buffers_prep,
                .issue                  = io_provide_buffers,
        },
        [IORING_OP_REMOVE_BUFFERS] = {
                .audit_skip             = 1,
                .iopoll                 = 1,
                .prep                   = io_remove_buffers_prep,
                .issue                  = io_remove_buffers,
        },
        [IORING_OP_TEE] = {
                .needs_file             = 1,
                .hash_reg_file          = 1,
                .unbound_nonreg_file    = 1,
                .audit_skip             = 1,
                .prep                   = io_tee_prep,
                .issue                  = io_tee,
        },
        [IORING_OP_SHUTDOWN] = {
                .needs_file             = 1,
#if defined(CONFIG_NET)
                .prep                   = io_shutdown_prep,
                .issue                  = io_shutdown,
#else
                .prep                   = io_eopnotsupp_prep,
#endif
        },
        [IORING_OP_RENAMEAT] = {
                .prep                   = io_renameat_prep,
                .issue                  = io_renameat,
                .cleanup                = io_renameat_cleanup,
        },
        [IORING_OP_UNLINKAT] = {
                .prep                   = io_unlinkat_prep,
                .issue                  = io_unlinkat,
                .cleanup                = io_unlinkat_cleanup,
        },
        [IORING_OP_MKDIRAT] = {
                .prep                   = io_mkdirat_prep,
                .issue                  = io_mkdirat,
                .cleanup                = io_mkdirat_cleanup,
        },
        [IORING_OP_SYMLINKAT] = {
                .prep                   = io_symlinkat_prep,
                .issue                  = io_symlinkat,
                .cleanup                = io_link_cleanup,
        },
        [IORING_OP_LINKAT] = {
                .prep                   = io_linkat_prep,
                .issue                  = io_linkat,
                .cleanup                = io_link_cleanup,
        },
        [IORING_OP_MSG_RING] = {
                .needs_file             = 1,
                .iopoll                 = 1,
                .prep                   = io_msg_ring_prep,
                .issue                  = io_msg_ring,
        },
        [IORING_OP_FSETXATTR] = {
                .needs_file = 1,
                .prep                   = io_fsetxattr_prep,
                .issue                  = io_fsetxattr,
                .cleanup                = io_xattr_cleanup,
        },
        [IORING_OP_SETXATTR] = {
                .prep                   = io_setxattr_prep,
                .issue                  = io_setxattr,
                .cleanup                = io_xattr_cleanup,
        },
        [IORING_OP_FGETXATTR] = {
                .needs_file = 1,
                .prep                   = io_fgetxattr_prep,
                .issue                  = io_fgetxattr,
                .cleanup                = io_xattr_cleanup,
        },
        [IORING_OP_GETXATTR] = {
                .prep                   = io_getxattr_prep,
                .issue                  = io_getxattr,
                .cleanup                = io_xattr_cleanup,
        },
        [IORING_OP_SOCKET] = {
                .audit_skip             = 1,
#if defined(CONFIG_NET)
                .prep                   = io_socket_prep,
                .issue                  = io_socket,
#else
                .prep                   = io_eopnotsupp_prep,
#endif
        },
        [IORING_OP_URING_CMD] = {
                .needs_file             = 1,
                .plug                   = 1,
                .async_size             = uring_cmd_pdu_size(1),
                .prep                   = io_uring_cmd_prep,
                .issue                  = io_uring_cmd,
                .prep_async             = io_uring_cmd_prep_async,
        },
};

static int __init io_uring_init(void)
{
        int i;

#define __BUILD_BUG_VERIFY_ELEMENT(stype, eoffset, etype, ename) do { \
        BUILD_BUG_ON(offsetof(stype, ename) != eoffset); \
        BUILD_BUG_ON(sizeof(etype) != sizeof_field(stype, ename)); \
} while (0)

#define BUILD_BUG_SQE_ELEM(eoffset, etype, ename) \
        __BUILD_BUG_VERIFY_ELEMENT(struct io_uring_sqe, eoffset, etype, ename)
        BUILD_BUG_ON(sizeof(struct io_uring_sqe) != 64);
        BUILD_BUG_SQE_ELEM(0,  __u8,   opcode);
        BUILD_BUG_SQE_ELEM(1,  __u8,   flags);
        BUILD_BUG_SQE_ELEM(2,  __u16,  ioprio);
        BUILD_BUG_SQE_ELEM(4,  __s32,  fd);
        BUILD_BUG_SQE_ELEM(8,  __u64,  off);
        BUILD_BUG_SQE_ELEM(8,  __u64,  addr2);
        BUILD_BUG_SQE_ELEM(16, __u64,  addr);
        BUILD_BUG_SQE_ELEM(16, __u64,  splice_off_in);
        BUILD_BUG_SQE_ELEM(24, __u32,  len);
        BUILD_BUG_SQE_ELEM(28,     __kernel_rwf_t, rw_flags);
        BUILD_BUG_SQE_ELEM(28, /* compat */   int, rw_flags);
        BUILD_BUG_SQE_ELEM(28, /* compat */ __u32, rw_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  fsync_flags);
        BUILD_BUG_SQE_ELEM(28, /* compat */ __u16,  poll_events);
        BUILD_BUG_SQE_ELEM(28, __u32,  poll32_events);
        BUILD_BUG_SQE_ELEM(28, __u32,  sync_range_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  msg_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  timeout_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  accept_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  cancel_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  open_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  statx_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  fadvise_advice);
        BUILD_BUG_SQE_ELEM(28, __u32,  splice_flags);
        BUILD_BUG_SQE_ELEM(32, __u64,  user_data);
        BUILD_BUG_SQE_ELEM(40, __u16,  buf_index);
        BUILD_BUG_SQE_ELEM(40, __u16,  buf_group);
        BUILD_BUG_SQE_ELEM(42, __u16,  personality);
        BUILD_BUG_SQE_ELEM(44, __s32,  splice_fd_in);
        BUILD_BUG_SQE_ELEM(44, __u32,  file_index);
        BUILD_BUG_SQE_ELEM(48, __u64,  addr3);

        BUILD_BUG_ON(sizeof(struct io_uring_files_update) !=
                     sizeof(struct io_uring_rsrc_update));
        BUILD_BUG_ON(sizeof(struct io_uring_rsrc_update) >
                     sizeof(struct io_uring_rsrc_update2));

        /* ->buf_index is u16 */
        BUILD_BUG_ON(IORING_MAX_REG_BUFFERS >= (1u << 16));
        BUILD_BUG_ON(BGID_ARRAY * sizeof(struct io_buffer_list) > PAGE_SIZE);
        BUILD_BUG_ON(offsetof(struct io_uring_buf_ring, bufs) != 0);
        BUILD_BUG_ON(offsetof(struct io_uring_buf, resv) !=
                     offsetof(struct io_uring_buf_ring, tail));

        /* should fit into one byte */
        BUILD_BUG_ON(SQE_VALID_FLAGS >= (1 << 8));
        BUILD_BUG_ON(SQE_COMMON_FLAGS >= (1 << 8));
        BUILD_BUG_ON((SQE_VALID_FLAGS | SQE_COMMON_FLAGS) != SQE_VALID_FLAGS);

        BUILD_BUG_ON(ARRAY_SIZE(io_op_defs) != IORING_OP_LAST);
        BUILD_BUG_ON(__REQ_F_LAST_BIT > 8 * sizeof(int));

        BUILD_BUG_ON(sizeof(atomic_t) != sizeof(u32));

        for (i = 0; i < ARRAY_SIZE(io_op_defs); i++) {
                BUG_ON(!io_op_defs[i].prep);
                if (io_op_defs[i].prep != io_eopnotsupp_prep)
                        BUG_ON(!io_op_defs[i].issue);
        }

        req_cachep = KMEM_CACHE(io_kiocb, SLAB_HWCACHE_ALIGN | SLAB_PANIC |
                                SLAB_ACCOUNT);
        return 0;
};
__initcall(io_uring_init);