Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

[linux-2.6-microblaze.git] / include / linux / mm_types.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_MM_TYPES_H
#define _LINUX_MM_TYPES_H

#include <linux/mm_types_task.h>

#include <linux/auxvec.h>
#include <linux/kref.h>
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/rbtree.h>
#include <linux/rwsem.h>
#include <linux/completion.h>
#include <linux/cpumask.h>
#include <linux/uprobes.h>
#include <linux/rcupdate.h>
#include <linux/page-flags-layout.h>
#include <linux/workqueue.h>
#include <linux/seqlock.h>

#include <asm/mmu.h>

#ifndef AT_VECTOR_SIZE_ARCH
#define AT_VECTOR_SIZE_ARCH 0
#endif
#define AT_VECTOR_SIZE (2*(AT_VECTOR_SIZE_ARCH + AT_VECTOR_SIZE_BASE + 1))

#define INIT_PASID      0

struct address_space;
struct mem_cgroup;

/*
 * Each physical page in the system has a struct page associated with
 * it to keep track of whatever it is we are using the page for at the
 * moment. Note that we have no way to track which tasks are using
 * a page, though if it is a pagecache page, rmap structures can tell us
 * who is mapping it.
 *
 * If you allocate the page using alloc_pages(), you can use some of the
 * space in struct page for your own purposes.  The five words in the main
 * union are available, except for bit 0 of the first word which must be
 * kept clear.  Many users use this word to store a pointer to an object
 * which is guaranteed to be aligned.  If you use the same storage as
 * page->mapping, you must restore it to NULL before freeing the page.
 *
 * If your page will not be mapped to userspace, you can also use the four
 * bytes in the mapcount union, but you must call page_mapcount_reset()
 * before freeing it.
 *
 * If you want to use the refcount field, it must be used in such a way
 * that other CPUs temporarily incrementing and then decrementing the
 * refcount does not cause problems.  On receiving the page from
 * alloc_pages(), the refcount will be positive.
 *
 * If you allocate pages of order > 0, you can use some of the fields
 * in each subpage, but you may need to restore some of their values
 * afterwards.
 *
 * SLUB uses cmpxchg_double() to atomically update its freelist and counters.
 * That requires that freelist & counters in struct slab be adjacent and
 * double-word aligned. Because struct slab currently just reinterprets the
 * bits of struct page, we align all struct pages to double-word boundaries,
 * and ensure that 'freelist' is aligned within struct slab.
 */
#ifdef CONFIG_HAVE_ALIGNED_STRUCT_PAGE
#define _struct_page_alignment  __aligned(2 * sizeof(unsigned long))
#else
#define _struct_page_alignment
#endif

struct page {
        unsigned long flags;            /* Atomic flags, some possibly
                                         * updated asynchronously */
        /*
         * Five words (20/40 bytes) are available in this union.
         * WARNING: bit 0 of the first word is used for PageTail(). That
         * means the other users of this union MUST NOT use the bit to
         * avoid collision and false-positive PageTail().
         */
        union {
                struct {        /* Page cache and anonymous pages */
                        /**
                         * @lru: Pageout list, eg. active_list protected by
                         * lruvec->lru_lock.  Sometimes used as a generic list
                         * by the page owner.
                         */
                        struct list_head lru;
                        /* See page-flags.h for PAGE_MAPPING_FLAGS */
                        struct address_space *mapping;
                        pgoff_t index;          /* Our offset within mapping. */
                        /**
                         * @private: Mapping-private opaque data.
                         * Usually used for buffer_heads if PagePrivate.
                         * Used for swp_entry_t if PageSwapCache.
                         * Indicates order in the buddy system if PageBuddy.
                         */
                        unsigned long private;
                };
                struct {        /* page_pool used by netstack */
                        /**
                         * @pp_magic: magic value to avoid recycling non
                         * page_pool allocated pages.
                         */
                        unsigned long pp_magic;
                        struct page_pool *pp;
                        unsigned long _pp_mapping_pad;
                        unsigned long dma_addr;
                        union {
                                /**
                                 * dma_addr_upper: might require a 64-bit
                                 * value on 32-bit architectures.
                                 */
                                unsigned long dma_addr_upper;
                                /**
                                 * For frag page support, not supported in
                                 * 32-bit architectures with 64-bit DMA.
                                 */
                                atomic_long_t pp_frag_count;
                        };
                };
                struct {        /* Tail pages of compound page */
                        unsigned long compound_head;    /* Bit zero is set */

                        /* First tail page only */
                        unsigned char compound_dtor;
                        unsigned char compound_order;
                        atomic_t compound_mapcount;
                        unsigned int compound_nr; /* 1 << compound_order */
                };
                struct {        /* Second tail page of compound page */
                        unsigned long _compound_pad_1;  /* compound_head */
                        atomic_t hpage_pinned_refcount;
                        /* For both global and memcg */
                        struct list_head deferred_list;
                };
                struct {        /* Page table pages */
                        unsigned long _pt_pad_1;        /* compound_head */
                        pgtable_t pmd_huge_pte; /* protected by page->ptl */
                        unsigned long _pt_pad_2;        /* mapping */
                        union {
                                struct mm_struct *pt_mm; /* x86 pgds only */
                                atomic_t pt_frag_refcount; /* powerpc */
                        };
#if ALLOC_SPLIT_PTLOCKS
                        spinlock_t *ptl;
#else
                        spinlock_t ptl;
#endif
                };
                struct {        /* ZONE_DEVICE pages */
                        /** @pgmap: Points to the hosting device page map. */
                        struct dev_pagemap *pgmap;
                        void *zone_device_data;
                        /*
                         * ZONE_DEVICE private pages are counted as being
                         * mapped so the next 3 words hold the mapping, index,
                         * and private fields from the source anonymous or
                         * page cache page while the page is migrated to device
                         * private memory.
                         * ZONE_DEVICE MEMORY_DEVICE_FS_DAX pages also
                         * use the mapping, index, and private fields when
                         * pmem backed DAX files are mapped.
                         */
                };

                /** @rcu_head: You can use this to free a page by RCU. */
                struct rcu_head rcu_head;
        };

        union {         /* This union is 4 bytes in size. */
                /*
                 * If the page can be mapped to userspace, encodes the number
                 * of times this page is referenced by a page table.
                 */
                atomic_t _mapcount;

                /*
                 * If the page is neither PageSlab nor mappable to userspace,
                 * the value stored here may help determine what this page
                 * is used for.  See page-flags.h for a list of page types
                 * which are currently stored here.
                 */
                unsigned int page_type;
        };

        /* Usage count. *DO NOT USE DIRECTLY*. See page_ref.h */
        atomic_t _refcount;

#ifdef CONFIG_MEMCG
        unsigned long memcg_data;
#endif

        /*
         * On machines where all RAM is mapped into kernel address space,
         * we can simply calculate the virtual address. On machines with
         * highmem some memory is mapped into kernel virtual memory
         * dynamically, so we need a place to store that address.
         * Note that this field could be 16 bits on x86 ... ;)
         *
         * Architectures with slow multiplication can define
         * WANT_PAGE_VIRTUAL in asm/page.h
         */
#if defined(WANT_PAGE_VIRTUAL)
        void *virtual;                  /* Kernel virtual address (NULL if
                                           not kmapped, ie. highmem) */
#endif /* WANT_PAGE_VIRTUAL */

#ifdef LAST_CPUPID_NOT_IN_PAGE_FLAGS
        int _last_cpupid;
#endif
} _struct_page_alignment;

/**
 * struct folio - Represents a contiguous set of bytes.
 * @flags: Identical to the page flags.
 * @lru: Least Recently Used list; tracks how recently this folio was used.
 * @mapping: The file this page belongs to, or refers to the anon_vma for
 *    anonymous memory.
 * @index: Offset within the file, in units of pages.  For anonymous memory,
 *    this is the index from the beginning of the mmap.
 * @private: Filesystem per-folio data (see folio_attach_private()).
 *    Used for swp_entry_t if folio_test_swapcache().
 * @_mapcount: Do not access this member directly.  Use folio_mapcount() to
 *    find out how many times this folio is mapped by userspace.
 * @_refcount: Do not access this member directly.  Use folio_ref_count()
 *    to find how many references there are to this folio.
 * @memcg_data: Memory Control Group data.
 *
 * A folio is a physically, virtually and logically contiguous set
 * of bytes.  It is a power-of-two in size, and it is aligned to that
 * same power-of-two.  It is at least as large as %PAGE_SIZE.  If it is
 * in the page cache, it is at a file offset which is a multiple of that
 * power-of-two.  It may be mapped into userspace at an address which is
 * at an arbitrary page offset, but its kernel virtual address is aligned
 * to its size.
 */
struct folio {
        /* private: don't document the anon union */
        union {
                struct {
        /* public: */
                        unsigned long flags;
                        struct list_head lru;
                        struct address_space *mapping;
                        pgoff_t index;
                        void *private;
                        atomic_t _mapcount;
                        atomic_t _refcount;
#ifdef CONFIG_MEMCG
                        unsigned long memcg_data;
#endif
        /* private: the union with struct page is transitional */
                };
                struct page page;
        };
};

static_assert(sizeof(struct page) == sizeof(struct folio));
#define FOLIO_MATCH(pg, fl)                                             \
        static_assert(offsetof(struct page, pg) == offsetof(struct folio, fl))
FOLIO_MATCH(flags, flags);
FOLIO_MATCH(lru, lru);
FOLIO_MATCH(mapping, mapping);
FOLIO_MATCH(compound_head, lru);
FOLIO_MATCH(index, index);
FOLIO_MATCH(private, private);
FOLIO_MATCH(_mapcount, _mapcount);
FOLIO_MATCH(_refcount, _refcount);
#ifdef CONFIG_MEMCG
FOLIO_MATCH(memcg_data, memcg_data);
#endif
#undef FOLIO_MATCH

static inline atomic_t *folio_mapcount_ptr(struct folio *folio)
{
        struct page *tail = &folio->page + 1;
        return &tail->compound_mapcount;
}

static inline atomic_t *compound_mapcount_ptr(struct page *page)
{
        return &page[1].compound_mapcount;
}

static inline atomic_t *compound_pincount_ptr(struct page *page)
{
        return &page[2].hpage_pinned_refcount;
}

/*
 * Used for sizing the vmemmap region on some architectures
 */
#define STRUCT_PAGE_MAX_SHIFT   (order_base_2(sizeof(struct page)))

#define PAGE_FRAG_CACHE_MAX_SIZE        __ALIGN_MASK(32768, ~PAGE_MASK)
#define PAGE_FRAG_CACHE_MAX_ORDER       get_order(PAGE_FRAG_CACHE_MAX_SIZE)

/*
 * page_private can be used on tail pages.  However, PagePrivate is only
 * checked by the VM on the head page.  So page_private on the tail pages
 * should be used for data that's ancillary to the head page (eg attaching
 * buffer heads to tail pages after attaching buffer heads to the head page)
 */
#define page_private(page)              ((page)->private)

static inline void set_page_private(struct page *page, unsigned long private)
{
        page->private = private;
}

static inline void *folio_get_private(struct folio *folio)
{
        return folio->private;
}

struct page_frag_cache {
        void * va;
#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
        __u16 offset;
        __u16 size;
#else
        __u32 offset;
#endif
        /* we maintain a pagecount bias, so that we dont dirty cache line
         * containing page->_refcount every time we allocate a fragment.
         */
        unsigned int            pagecnt_bias;
        bool pfmemalloc;
};

typedef unsigned long vm_flags_t;

/*
 * A region containing a mapping of a non-memory backed file under NOMMU
 * conditions.  These are held in a global tree and are pinned by the VMAs that
 * map parts of them.
 */
struct vm_region {
        struct rb_node  vm_rb;          /* link in global region tree */
        vm_flags_t      vm_flags;       /* VMA vm_flags */
        unsigned long   vm_start;       /* start address of region */
        unsigned long   vm_end;         /* region initialised to here */
        unsigned long   vm_top;         /* region allocated to here */
        unsigned long   vm_pgoff;       /* the offset in vm_file corresponding to vm_start */
        struct file     *vm_file;       /* the backing file or NULL */

        int             vm_usage;       /* region usage count (access under nommu_region_sem) */
        bool            vm_icache_flushed : 1; /* true if the icache has been flushed for
                                                * this region */
};

#ifdef CONFIG_USERFAULTFD
#define NULL_VM_UFFD_CTX ((struct vm_userfaultfd_ctx) { NULL, })
struct vm_userfaultfd_ctx {
        struct userfaultfd_ctx *ctx;
};
#else /* CONFIG_USERFAULTFD */
#define NULL_VM_UFFD_CTX ((struct vm_userfaultfd_ctx) {})
struct vm_userfaultfd_ctx {};
#endif /* CONFIG_USERFAULTFD */

struct anon_vma_name {
        struct kref kref;
        /* The name needs to be at the end because it is dynamically sized. */
        char name[];
};

/*
 * This struct describes a virtual memory area. There is one of these
 * per VM-area/task. A VM area is any part of the process virtual memory
 * space that has a special rule for the page-fault handlers (ie a shared
 * library, the executable area etc).
 */
struct vm_area_struct {
        /* The first cache line has the info for VMA tree walking. */

        unsigned long vm_start;         /* Our start address within vm_mm. */
        unsigned long vm_end;           /* The first byte after our end address
                                           within vm_mm. */

        /* linked list of VM areas per task, sorted by address */
        struct vm_area_struct *vm_next, *vm_prev;

        struct rb_node vm_rb;

        /*
         * Largest free memory gap in bytes to the left of this VMA.
         * Either between this VMA and vma->vm_prev, or between one of the
         * VMAs below us in the VMA rbtree and its ->vm_prev. This helps
         * get_unmapped_area find a free area of the right size.
         */
        unsigned long rb_subtree_gap;

        /* Second cache line starts here. */

        struct mm_struct *vm_mm;        /* The address space we belong to. */

        /*
         * Access permissions of this VMA.
         * See vmf_insert_mixed_prot() for discussion.
         */
        pgprot_t vm_page_prot;
        unsigned long vm_flags;         /* Flags, see mm.h. */

        /*
         * For areas with an address space and backing store,
         * linkage into the address_space->i_mmap interval tree.
         *
         * For private anonymous mappings, a pointer to a null terminated string
         * containing the name given to the vma, or NULL if unnamed.
         */

        union {
                struct {
                        struct rb_node rb;
                        unsigned long rb_subtree_last;
                } shared;
                /*
                 * Serialized by mmap_sem. Never use directly because it is
                 * valid only when vm_file is NULL. Use anon_vma_name instead.
                 */
                struct anon_vma_name *anon_name;
        };

        /*
         * A file's MAP_PRIVATE vma can be in both i_mmap tree and anon_vma
         * list, after a COW of one of the file pages.  A MAP_SHARED vma
         * can only be in the i_mmap tree.  An anonymous MAP_PRIVATE, stack
         * or brk vma (with NULL file) can only be in an anon_vma list.
         */
        struct list_head anon_vma_chain; /* Serialized by mmap_lock &
                                          * page_table_lock */
        struct anon_vma *anon_vma;      /* Serialized by page_table_lock */

        /* Function pointers to deal with this struct. */
        const struct vm_operations_struct *vm_ops;

        /* Information about our backing store: */
        unsigned long vm_pgoff;         /* Offset (within vm_file) in PAGE_SIZE
                                           units */
        struct file * vm_file;          /* File we map to (can be NULL). */
        void * vm_private_data;         /* was vm_pte (shared mem) */

#ifdef CONFIG_SWAP
        atomic_long_t swap_readahead_info;
#endif
#ifndef CONFIG_MMU
        struct vm_region *vm_region;    /* NOMMU mapping region */
#endif
#ifdef CONFIG_NUMA
        struct mempolicy *vm_policy;    /* NUMA policy for the VMA */
#endif
        struct vm_userfaultfd_ctx vm_userfaultfd_ctx;
} __randomize_layout;

struct kioctx_table;
struct mm_struct {
        struct {
                struct vm_area_struct *mmap;            /* list of VMAs */
                struct rb_root mm_rb;
                u64 vmacache_seqnum;                   /* per-thread vmacache */
#ifdef CONFIG_MMU
                unsigned long (*get_unmapped_area) (struct file *filp,
                                unsigned long addr, unsigned long len,
                                unsigned long pgoff, unsigned long flags);
#endif
                unsigned long mmap_base;        /* base of mmap area */
                unsigned long mmap_legacy_base; /* base of mmap area in bottom-up allocations */
#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
                /* Base addresses for compatible mmap() */
                unsigned long mmap_compat_base;
                unsigned long mmap_compat_legacy_base;
#endif
                unsigned long task_size;        /* size of task vm space */
                unsigned long highest_vm_end;   /* highest vma end address */
                pgd_t * pgd;

#ifdef CONFIG_MEMBARRIER
                /**
                 * @membarrier_state: Flags controlling membarrier behavior.
                 *
                 * This field is close to @pgd to hopefully fit in the same
                 * cache-line, which needs to be touched by switch_mm().
                 */
                atomic_t membarrier_state;
#endif

                /**
                 * @mm_users: The number of users including userspace.
                 *
                 * Use mmget()/mmget_not_zero()/mmput() to modify. When this
                 * drops to 0 (i.e. when the task exits and there are no other
                 * temporary reference holders), we also release a reference on
                 * @mm_count (which may then free the &struct mm_struct if
                 * @mm_count also drops to 0).
                 */
                atomic_t mm_users;

                /**
                 * @mm_count: The number of references to &struct mm_struct
                 * (@mm_users count as 1).
                 *
                 * Use mmgrab()/mmdrop() to modify. When this drops to 0, the
                 * &struct mm_struct is freed.
                 */
                atomic_t mm_count;

#ifdef CONFIG_MMU
                atomic_long_t pgtables_bytes;   /* PTE page table pages */
#endif
                int map_count;                  /* number of VMAs */

                spinlock_t page_table_lock; /* Protects page tables and some
                                             * counters
                                             */
                /*
                 * With some kernel config, the current mmap_lock's offset
                 * inside 'mm_struct' is at 0x120, which is very optimal, as
                 * its two hot fields 'count' and 'owner' sit in 2 different
                 * cachelines,  and when mmap_lock is highly contended, both
                 * of the 2 fields will be accessed frequently, current layout
                 * will help to reduce cache bouncing.
                 *
                 * So please be careful with adding new fields before
                 * mmap_lock, which can easily push the 2 fields into one
                 * cacheline.
                 */
                struct rw_semaphore mmap_lock;

                struct list_head mmlist; /* List of maybe swapped mm's. These
                                          * are globally strung together off
                                          * init_mm.mmlist, and are protected
                                          * by mmlist_lock
                                          */


                unsigned long hiwater_rss; /* High-watermark of RSS usage */
                unsigned long hiwater_vm;  /* High-water virtual memory usage */

                unsigned long total_vm;    /* Total pages mapped */
                unsigned long locked_vm;   /* Pages that have PG_mlocked set */
                atomic64_t    pinned_vm;   /* Refcount permanently increased */
                unsigned long data_vm;     /* VM_WRITE & ~VM_SHARED & ~VM_STACK */
                unsigned long exec_vm;     /* VM_EXEC & ~VM_WRITE & ~VM_STACK */
                unsigned long stack_vm;    /* VM_STACK */
                unsigned long def_flags;

                /**
                 * @write_protect_seq: Locked when any thread is write
                 * protecting pages mapped by this mm to enforce a later COW,
                 * for instance during page table copying for fork().
                 */
                seqcount_t write_protect_seq;

                spinlock_t arg_lock; /* protect the below fields */

                unsigned long start_code, end_code, start_data, end_data;
                unsigned long start_brk, brk, start_stack;
                unsigned long arg_start, arg_end, env_start, env_end;

                unsigned long saved_auxv[AT_VECTOR_SIZE]; /* for /proc/PID/auxv */

                /*
                 * Special counters, in some configurations protected by the
                 * page_table_lock, in other configurations by being atomic.
                 */
                struct mm_rss_stat rss_stat;

                struct linux_binfmt *binfmt;

                /* Architecture-specific MM context */
                mm_context_t context;

                unsigned long flags; /* Must use atomic bitops to access */

#ifdef CONFIG_AIO
                spinlock_t                      ioctx_lock;
                struct kioctx_table __rcu       *ioctx_table;
#endif
#ifdef CONFIG_MEMCG
                /*
                 * "owner" points to a task that is regarded as the canonical
                 * user/owner of this mm. All of the following must be true in
                 * order for it to be changed:
                 *
                 * current == mm->owner
                 * current->mm != mm
                 * new_owner->mm == mm
                 * new_owner->alloc_lock is held
                 */
                struct task_struct __rcu *owner;
#endif
                struct user_namespace *user_ns;

                /* store ref to file /proc/<pid>/exe symlink points to */
                struct file __rcu *exe_file;
#ifdef CONFIG_MMU_NOTIFIER
                struct mmu_notifier_subscriptions *notifier_subscriptions;
#endif
#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
                pgtable_t pmd_huge_pte; /* protected by page_table_lock */
#endif
#ifdef CONFIG_NUMA_BALANCING
                /*
                 * numa_next_scan is the next time that the PTEs will be marked
                 * pte_numa. NUMA hinting faults will gather statistics and
                 * migrate pages to new nodes if necessary.
                 */
                unsigned long numa_next_scan;

                /* Restart point for scanning and setting pte_numa */
                unsigned long numa_scan_offset;

                /* numa_scan_seq prevents two threads setting pte_numa */
                int numa_scan_seq;
#endif
                /*
                 * An operation with batched TLB flushing is going on. Anything
                 * that can move process memory needs to flush the TLB when
                 * moving a PROT_NONE or PROT_NUMA mapped page.
                 */
                atomic_t tlb_flush_pending;
#ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
                /* See flush_tlb_batched_pending() */
                atomic_t tlb_flush_batched;
#endif
                struct uprobes_state uprobes_state;
#ifdef CONFIG_PREEMPT_RT
                struct rcu_head delayed_drop;
#endif
#ifdef CONFIG_HUGETLB_PAGE
                atomic_long_t hugetlb_usage;
#endif
                struct work_struct async_put_work;

#ifdef CONFIG_IOMMU_SUPPORT
                u32 pasid;
#endif
        } __randomize_layout;

        /*
         * The mm_cpumask needs to be at the end of mm_struct, because it
         * is dynamically sized based on nr_cpu_ids.
         */
        unsigned long cpu_bitmap[];
};

extern struct mm_struct init_mm;

/* Pointer magic because the dynamic array size confuses some compilers. */
static inline void mm_init_cpumask(struct mm_struct *mm)
{
        unsigned long cpu_bitmap = (unsigned long)mm;

        cpu_bitmap += offsetof(struct mm_struct, cpu_bitmap);
        cpumask_clear((struct cpumask *)cpu_bitmap);
}

/* Future-safe accessor for struct mm_struct's cpu_vm_mask. */
static inline cpumask_t *mm_cpumask(struct mm_struct *mm)
{
        return (struct cpumask *)&mm->cpu_bitmap;
}

struct mmu_gather;
extern void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm);
extern void tlb_gather_mmu_fullmm(struct mmu_gather *tlb, struct mm_struct *mm);
extern void tlb_finish_mmu(struct mmu_gather *tlb);

struct vm_fault;

/**
 * typedef vm_fault_t - Return type for page fault handlers.
 *
 * Page fault handlers return a bitmask of %VM_FAULT values.
 */
typedef __bitwise unsigned int vm_fault_t;

/**
 * enum vm_fault_reason - Page fault handlers return a bitmask of
 * these values to tell the core VM what happened when handling the
 * fault. Used to decide whether a process gets delivered SIGBUS or
 * just gets major/minor fault counters bumped up.
 *
 * @VM_FAULT_OOM:               Out Of Memory
 * @VM_FAULT_SIGBUS:            Bad access
 * @VM_FAULT_MAJOR:             Page read from storage
 * @VM_FAULT_WRITE:             Special case for get_user_pages
 * @VM_FAULT_HWPOISON:          Hit poisoned small page
 * @VM_FAULT_HWPOISON_LARGE:    Hit poisoned large page. Index encoded
 *                              in upper bits
 * @VM_FAULT_SIGSEGV:           segmentation fault
 * @VM_FAULT_NOPAGE:            ->fault installed the pte, not return page
 * @VM_FAULT_LOCKED:            ->fault locked the returned page
 * @VM_FAULT_RETRY:             ->fault blocked, must retry
 * @VM_FAULT_FALLBACK:          huge page fault failed, fall back to small
 * @VM_FAULT_DONE_COW:          ->fault has fully handled COW
 * @VM_FAULT_NEEDDSYNC:         ->fault did not modify page tables and needs
 *                              fsync() to complete (for synchronous page faults
 *                              in DAX)
 * @VM_FAULT_HINDEX_MASK:       mask HINDEX value
 *
 */
enum vm_fault_reason {
        VM_FAULT_OOM            = (__force vm_fault_t)0x000001,
        VM_FAULT_SIGBUS         = (__force vm_fault_t)0x000002,
        VM_FAULT_MAJOR          = (__force vm_fault_t)0x000004,
        VM_FAULT_WRITE          = (__force vm_fault_t)0x000008,
        VM_FAULT_HWPOISON       = (__force vm_fault_t)0x000010,
        VM_FAULT_HWPOISON_LARGE = (__force vm_fault_t)0x000020,
        VM_FAULT_SIGSEGV        = (__force vm_fault_t)0x000040,
        VM_FAULT_NOPAGE         = (__force vm_fault_t)0x000100,
        VM_FAULT_LOCKED         = (__force vm_fault_t)0x000200,
        VM_FAULT_RETRY          = (__force vm_fault_t)0x000400,
        VM_FAULT_FALLBACK       = (__force vm_fault_t)0x000800,
        VM_FAULT_DONE_COW       = (__force vm_fault_t)0x001000,
        VM_FAULT_NEEDDSYNC      = (__force vm_fault_t)0x002000,
        VM_FAULT_HINDEX_MASK    = (__force vm_fault_t)0x0f0000,
};

/* Encode hstate index for a hwpoisoned large page */
#define VM_FAULT_SET_HINDEX(x) ((__force vm_fault_t)((x) << 16))
#define VM_FAULT_GET_HINDEX(x) (((__force unsigned int)(x) >> 16) & 0xf)

#define VM_FAULT_ERROR (VM_FAULT_OOM | VM_FAULT_SIGBUS |        \
                        VM_FAULT_SIGSEGV | VM_FAULT_HWPOISON |  \
                        VM_FAULT_HWPOISON_LARGE | VM_FAULT_FALLBACK)

#define VM_FAULT_RESULT_TRACE \
        { VM_FAULT_OOM,                 "OOM" },        \
        { VM_FAULT_SIGBUS,              "SIGBUS" },     \
        { VM_FAULT_MAJOR,               "MAJOR" },      \
        { VM_FAULT_WRITE,               "WRITE" },      \
        { VM_FAULT_HWPOISON,            "HWPOISON" },   \
        { VM_FAULT_HWPOISON_LARGE,      "HWPOISON_LARGE" },     \
        { VM_FAULT_SIGSEGV,             "SIGSEGV" },    \
        { VM_FAULT_NOPAGE,              "NOPAGE" },     \
        { VM_FAULT_LOCKED,              "LOCKED" },     \
        { VM_FAULT_RETRY,               "RETRY" },      \
        { VM_FAULT_FALLBACK,            "FALLBACK" },   \
        { VM_FAULT_DONE_COW,            "DONE_COW" },   \
        { VM_FAULT_NEEDDSYNC,           "NEEDDSYNC" }

struct vm_special_mapping {
        const char *name;       /* The name, e.g. "[vdso]". */

        /*
         * If .fault is not provided, this points to a
         * NULL-terminated array of pages that back the special mapping.
         *
         * This must not be NULL unless .fault is provided.
         */
        struct page **pages;

        /*
         * If non-NULL, then this is called to resolve page faults
         * on the special mapping.  If used, .pages is not checked.
         */
        vm_fault_t (*fault)(const struct vm_special_mapping *sm,
                                struct vm_area_struct *vma,
                                struct vm_fault *vmf);

        int (*mremap)(const struct vm_special_mapping *sm,
                     struct vm_area_struct *new_vma);
};

enum tlb_flush_reason {
        TLB_FLUSH_ON_TASK_SWITCH,
        TLB_REMOTE_SHOOTDOWN,
        TLB_LOCAL_SHOOTDOWN,
        TLB_LOCAL_MM_SHOOTDOWN,
        TLB_REMOTE_SEND_IPI,
        NR_TLB_FLUSH_REASONS,
};

 /*
  * A swap entry has to fit into a "unsigned long", as the entry is hidden
  * in the "index" field of the swapper address space.
  */
typedef struct {
        unsigned long val;
} swp_entry_t;

/**
 * enum fault_flag - Fault flag definitions.
 * @FAULT_FLAG_WRITE: Fault was a write fault.
 * @FAULT_FLAG_MKWRITE: Fault was mkwrite of existing PTE.
 * @FAULT_FLAG_ALLOW_RETRY: Allow to retry the fault if blocked.
 * @FAULT_FLAG_RETRY_NOWAIT: Don't drop mmap_lock and wait when retrying.
 * @FAULT_FLAG_KILLABLE: The fault task is in SIGKILL killable region.
 * @FAULT_FLAG_TRIED: The fault has been tried once.
 * @FAULT_FLAG_USER: The fault originated in userspace.
 * @FAULT_FLAG_REMOTE: The fault is not for current task/mm.
 * @FAULT_FLAG_INSTRUCTION: The fault was during an instruction fetch.
 * @FAULT_FLAG_INTERRUPTIBLE: The fault can be interrupted by non-fatal signals.
 *
 * About @FAULT_FLAG_ALLOW_RETRY and @FAULT_FLAG_TRIED: we can specify
 * whether we would allow page faults to retry by specifying these two
 * fault flags correctly.  Currently there can be three legal combinations:
 *
 * (a) ALLOW_RETRY and !TRIED:  this means the page fault allows retry, and
 *                              this is the first try
 *
 * (b) ALLOW_RETRY and TRIED:   this means the page fault allows retry, and
 *                              we've already tried at least once
 *
 * (c) !ALLOW_RETRY and !TRIED: this means the page fault does not allow retry
 *
 * The unlisted combination (!ALLOW_RETRY && TRIED) is illegal and should never
 * be used.  Note that page faults can be allowed to retry for multiple times,
 * in which case we'll have an initial fault with flags (a) then later on
 * continuous faults with flags (b).  We should always try to detect pending
 * signals before a retry to make sure the continuous page faults can still be
 * interrupted if necessary.
 */
enum fault_flag {
        FAULT_FLAG_WRITE =              1 << 0,
        FAULT_FLAG_MKWRITE =            1 << 1,
        FAULT_FLAG_ALLOW_RETRY =        1 << 2,
        FAULT_FLAG_RETRY_NOWAIT =       1 << 3,
        FAULT_FLAG_KILLABLE =           1 << 4,
        FAULT_FLAG_TRIED =              1 << 5,
        FAULT_FLAG_USER =               1 << 6,
        FAULT_FLAG_REMOTE =             1 << 7,
        FAULT_FLAG_INSTRUCTION =        1 << 8,
        FAULT_FLAG_INTERRUPTIBLE =      1 << 9,
};

#endif /* _LINUX_MM_TYPES_H */