mm: memmap defer init doesn't work as expected

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

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

#include <linux/errno.h>

#ifdef __KERNEL__

#include <linux/mmdebug.h>
#include <linux/gfp.h>
#include <linux/bug.h>
#include <linux/list.h>
#include <linux/mmzone.h>
#include <linux/rbtree.h>
#include <linux/atomic.h>
#include <linux/debug_locks.h>
#include <linux/mm_types.h>
#include <linux/mmap_lock.h>
#include <linux/range.h>
#include <linux/pfn.h>
#include <linux/percpu-refcount.h>
#include <linux/bit_spinlock.h>
#include <linux/shrinker.h>
#include <linux/resource.h>
#include <linux/page_ext.h>
#include <linux/err.h>
#include <linux/page-flags.h>
#include <linux/page_ref.h>
#include <linux/memremap.h>
#include <linux/overflow.h>
#include <linux/sizes.h>
#include <linux/sched.h>
#include <linux/pgtable.h>
#include <linux/kasan.h>

struct mempolicy;
struct anon_vma;
struct anon_vma_chain;
struct file_ra_state;
struct user_struct;
struct writeback_control;
struct bdi_writeback;
struct pt_regs;

extern int sysctl_page_lock_unfairness;

void init_mm_internals(void);

#ifndef CONFIG_NEED_MULTIPLE_NODES      /* Don't use mapnrs, do it properly */
extern unsigned long max_mapnr;

static inline void set_max_mapnr(unsigned long limit)
{
        max_mapnr = limit;
}
#else
static inline void set_max_mapnr(unsigned long limit) { }
#endif

extern atomic_long_t _totalram_pages;
static inline unsigned long totalram_pages(void)
{
        return (unsigned long)atomic_long_read(&_totalram_pages);
}

static inline void totalram_pages_inc(void)
{
        atomic_long_inc(&_totalram_pages);
}

static inline void totalram_pages_dec(void)
{
        atomic_long_dec(&_totalram_pages);
}

static inline void totalram_pages_add(long count)
{
        atomic_long_add(count, &_totalram_pages);
}

extern void * high_memory;
extern int page_cluster;

#ifdef CONFIG_SYSCTL
extern int sysctl_legacy_va_layout;
#else
#define sysctl_legacy_va_layout 0
#endif

#ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS
extern const int mmap_rnd_bits_min;
extern const int mmap_rnd_bits_max;
extern int mmap_rnd_bits __read_mostly;
#endif
#ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
extern const int mmap_rnd_compat_bits_min;
extern const int mmap_rnd_compat_bits_max;
extern int mmap_rnd_compat_bits __read_mostly;
#endif

#include <asm/page.h>
#include <asm/processor.h>

/*
 * Architectures that support memory tagging (assigning tags to memory regions,
 * embedding these tags into addresses that point to these memory regions, and
 * checking that the memory and the pointer tags match on memory accesses)
 * redefine this macro to strip tags from pointers.
 * It's defined as noop for arcitectures that don't support memory tagging.
 */
#ifndef untagged_addr
#define untagged_addr(addr) (addr)
#endif

#ifndef __pa_symbol
#define __pa_symbol(x)  __pa(RELOC_HIDE((unsigned long)(x), 0))
#endif

#ifndef page_to_virt
#define page_to_virt(x) __va(PFN_PHYS(page_to_pfn(x)))
#endif

#ifndef lm_alias
#define lm_alias(x)     __va(__pa_symbol(x))
#endif

/*
 * To prevent common memory management code establishing
 * a zero page mapping on a read fault.
 * This macro should be defined within <asm/pgtable.h>.
 * s390 does this to prevent multiplexing of hardware bits
 * related to the physical page in case of virtualization.
 */
#ifndef mm_forbids_zeropage
#define mm_forbids_zeropage(X)  (0)
#endif

/*
 * On some architectures it is expensive to call memset() for small sizes.
 * If an architecture decides to implement their own version of
 * mm_zero_struct_page they should wrap the defines below in a #ifndef and
 * define their own version of this macro in <asm/pgtable.h>
 */
#if BITS_PER_LONG == 64
/* This function must be updated when the size of struct page grows above 80
 * or reduces below 56. The idea that compiler optimizes out switch()
 * statement, and only leaves move/store instructions. Also the compiler can
 * combine write statments if they are both assignments and can be reordered,
 * this can result in several of the writes here being dropped.
 */
#define mm_zero_struct_page(pp) __mm_zero_struct_page(pp)
static inline void __mm_zero_struct_page(struct page *page)
{
        unsigned long *_pp = (void *)page;

         /* Check that struct page is either 56, 64, 72, or 80 bytes */
        BUILD_BUG_ON(sizeof(struct page) & 7);
        BUILD_BUG_ON(sizeof(struct page) < 56);
        BUILD_BUG_ON(sizeof(struct page) > 80);

        switch (sizeof(struct page)) {
        case 80:
                _pp[9] = 0;
                fallthrough;
        case 72:
                _pp[8] = 0;
                fallthrough;
        case 64:
                _pp[7] = 0;
                fallthrough;
        case 56:
                _pp[6] = 0;
                _pp[5] = 0;
                _pp[4] = 0;
                _pp[3] = 0;
                _pp[2] = 0;
                _pp[1] = 0;
                _pp[0] = 0;
        }
}
#else
#define mm_zero_struct_page(pp)  ((void)memset((pp), 0, sizeof(struct page)))
#endif

/*
 * Default maximum number of active map areas, this limits the number of vmas
 * per mm struct. Users can overwrite this number by sysctl but there is a
 * problem.
 *
 * When a program's coredump is generated as ELF format, a section is created
 * per a vma. In ELF, the number of sections is represented in unsigned short.
 * This means the number of sections should be smaller than 65535 at coredump.
 * Because the kernel adds some informative sections to a image of program at
 * generating coredump, we need some margin. The number of extra sections is
 * 1-3 now and depends on arch. We use "5" as safe margin, here.
 *
 * ELF extended numbering allows more than 65535 sections, so 16-bit bound is
 * not a hard limit any more. Although some userspace tools can be surprised by
 * that.
 */
#define MAPCOUNT_ELF_CORE_MARGIN        (5)
#define DEFAULT_MAX_MAP_COUNT   (USHRT_MAX - MAPCOUNT_ELF_CORE_MARGIN)

extern int sysctl_max_map_count;

extern unsigned long sysctl_user_reserve_kbytes;
extern unsigned long sysctl_admin_reserve_kbytes;

extern int sysctl_overcommit_memory;
extern int sysctl_overcommit_ratio;
extern unsigned long sysctl_overcommit_kbytes;

int overcommit_ratio_handler(struct ctl_table *, int, void *, size_t *,
                loff_t *);
int overcommit_kbytes_handler(struct ctl_table *, int, void *, size_t *,
                loff_t *);
int overcommit_policy_handler(struct ctl_table *, int, void *, size_t *,
                loff_t *);
/*
 * Any attempt to mark this function as static leads to build failure
 * when CONFIG_DEBUG_INFO_BTF is enabled because __add_to_page_cache_locked()
 * is referred to by BPF code. This must be visible for error injection.
 */
int __add_to_page_cache_locked(struct page *page, struct address_space *mapping,
                pgoff_t index, gfp_t gfp, void **shadowp);

#define nth_page(page,n) pfn_to_page(page_to_pfn((page)) + (n))

/* to align the pointer to the (next) page boundary */
#define PAGE_ALIGN(addr) ALIGN(addr, PAGE_SIZE)

/* test whether an address (unsigned long or pointer) is aligned to PAGE_SIZE */
#define PAGE_ALIGNED(addr)      IS_ALIGNED((unsigned long)(addr), PAGE_SIZE)

#define lru_to_page(head) (list_entry((head)->prev, struct page, lru))

/*
 * Linux kernel virtual memory manager primitives.
 * The idea being to have a "virtual" mm in the same way
 * we have a virtual fs - giving a cleaner interface to the
 * mm details, and allowing different kinds of memory mappings
 * (from shared memory to executable loading to arbitrary
 * mmap() functions).
 */

struct vm_area_struct *vm_area_alloc(struct mm_struct *);
struct vm_area_struct *vm_area_dup(struct vm_area_struct *);
void vm_area_free(struct vm_area_struct *);

#ifndef CONFIG_MMU
extern struct rb_root nommu_region_tree;
extern struct rw_semaphore nommu_region_sem;

extern unsigned int kobjsize(const void *objp);
#endif

/*
 * vm_flags in vm_area_struct, see mm_types.h.
 * When changing, update also include/trace/events/mmflags.h
 */
#define VM_NONE         0x00000000

#define VM_READ         0x00000001      /* currently active flags */
#define VM_WRITE        0x00000002
#define VM_EXEC         0x00000004
#define VM_SHARED       0x00000008

/* mprotect() hardcodes VM_MAYREAD >> 4 == VM_READ, and so for r/w/x bits. */
#define VM_MAYREAD      0x00000010      /* limits for mprotect() etc */
#define VM_MAYWRITE     0x00000020
#define VM_MAYEXEC      0x00000040
#define VM_MAYSHARE     0x00000080

#define VM_GROWSDOWN    0x00000100      /* general info on the segment */
#define VM_UFFD_MISSING 0x00000200      /* missing pages tracking */
#define VM_PFNMAP       0x00000400      /* Page-ranges managed without "struct page", just pure PFN */
#define VM_DENYWRITE    0x00000800      /* ETXTBSY on write attempts.. */
#define VM_UFFD_WP      0x00001000      /* wrprotect pages tracking */

#define VM_LOCKED       0x00002000
#define VM_IO           0x00004000      /* Memory mapped I/O or similar */

                                        /* Used by sys_madvise() */
#define VM_SEQ_READ     0x00008000      /* App will access data sequentially */
#define VM_RAND_READ    0x00010000      /* App will not benefit from clustered reads */

#define VM_DONTCOPY     0x00020000      /* Do not copy this vma on fork */
#define VM_DONTEXPAND   0x00040000      /* Cannot expand with mremap() */
#define VM_LOCKONFAULT  0x00080000      /* Lock the pages covered when they are faulted in */
#define VM_ACCOUNT      0x00100000      /* Is a VM accounted object */
#define VM_NORESERVE    0x00200000      /* should the VM suppress accounting */
#define VM_HUGETLB      0x00400000      /* Huge TLB Page VM */
#define VM_SYNC         0x00800000      /* Synchronous page faults */
#define VM_ARCH_1       0x01000000      /* Architecture-specific flag */
#define VM_WIPEONFORK   0x02000000      /* Wipe VMA contents in child. */
#define VM_DONTDUMP     0x04000000      /* Do not include in the core dump */

#ifdef CONFIG_MEM_SOFT_DIRTY
# define VM_SOFTDIRTY   0x08000000      /* Not soft dirty clean area */
#else
# define VM_SOFTDIRTY   0
#endif

#define VM_MIXEDMAP     0x10000000      /* Can contain "struct page" and pure PFN pages */
#define VM_HUGEPAGE     0x20000000      /* MADV_HUGEPAGE marked this vma */
#define VM_NOHUGEPAGE   0x40000000      /* MADV_NOHUGEPAGE marked this vma */
#define VM_MERGEABLE    0x80000000      /* KSM may merge identical pages */

#ifdef CONFIG_ARCH_USES_HIGH_VMA_FLAGS
#define VM_HIGH_ARCH_BIT_0      32      /* bit only usable on 64-bit architectures */
#define VM_HIGH_ARCH_BIT_1      33      /* bit only usable on 64-bit architectures */
#define VM_HIGH_ARCH_BIT_2      34      /* bit only usable on 64-bit architectures */
#define VM_HIGH_ARCH_BIT_3      35      /* bit only usable on 64-bit architectures */
#define VM_HIGH_ARCH_BIT_4      36      /* bit only usable on 64-bit architectures */
#define VM_HIGH_ARCH_0  BIT(VM_HIGH_ARCH_BIT_0)
#define VM_HIGH_ARCH_1  BIT(VM_HIGH_ARCH_BIT_1)
#define VM_HIGH_ARCH_2  BIT(VM_HIGH_ARCH_BIT_2)
#define VM_HIGH_ARCH_3  BIT(VM_HIGH_ARCH_BIT_3)
#define VM_HIGH_ARCH_4  BIT(VM_HIGH_ARCH_BIT_4)
#endif /* CONFIG_ARCH_USES_HIGH_VMA_FLAGS */

#ifdef CONFIG_ARCH_HAS_PKEYS
# define VM_PKEY_SHIFT  VM_HIGH_ARCH_BIT_0
# define VM_PKEY_BIT0   VM_HIGH_ARCH_0  /* A protection key is a 4-bit value */
# define VM_PKEY_BIT1   VM_HIGH_ARCH_1  /* on x86 and 5-bit value on ppc64   */
# define VM_PKEY_BIT2   VM_HIGH_ARCH_2
# define VM_PKEY_BIT3   VM_HIGH_ARCH_3
#ifdef CONFIG_PPC
# define VM_PKEY_BIT4  VM_HIGH_ARCH_4
#else
# define VM_PKEY_BIT4  0
#endif
#endif /* CONFIG_ARCH_HAS_PKEYS */

#if defined(CONFIG_X86)
# define VM_PAT         VM_ARCH_1       /* PAT reserves whole VMA at once (x86) */
#elif defined(CONFIG_PPC)
# define VM_SAO         VM_ARCH_1       /* Strong Access Ordering (powerpc) */
#elif defined(CONFIG_PARISC)
# define VM_GROWSUP     VM_ARCH_1
#elif defined(CONFIG_IA64)
# define VM_GROWSUP     VM_ARCH_1
#elif defined(CONFIG_SPARC64)
# define VM_SPARC_ADI   VM_ARCH_1       /* Uses ADI tag for access control */
# define VM_ARCH_CLEAR  VM_SPARC_ADI
#elif defined(CONFIG_ARM64)
# define VM_ARM64_BTI   VM_ARCH_1       /* BTI guarded page, a.k.a. GP bit */
# define VM_ARCH_CLEAR  VM_ARM64_BTI
#elif !defined(CONFIG_MMU)
# define VM_MAPPED_COPY VM_ARCH_1       /* T if mapped copy of data (nommu mmap) */
#endif

#if defined(CONFIG_ARM64_MTE)
# define VM_MTE         VM_HIGH_ARCH_0  /* Use Tagged memory for access control */
# define VM_MTE_ALLOWED VM_HIGH_ARCH_1  /* Tagged memory permitted */
#else
# define VM_MTE         VM_NONE
# define VM_MTE_ALLOWED VM_NONE
#endif

#ifndef VM_GROWSUP
# define VM_GROWSUP     VM_NONE
#endif

/* Bits set in the VMA until the stack is in its final location */
#define VM_STACK_INCOMPLETE_SETUP       (VM_RAND_READ | VM_SEQ_READ)

#define TASK_EXEC ((current->personality & READ_IMPLIES_EXEC) ? VM_EXEC : 0)

/* Common data flag combinations */
#define VM_DATA_FLAGS_TSK_EXEC  (VM_READ | VM_WRITE | TASK_EXEC | \
                                 VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC)
#define VM_DATA_FLAGS_NON_EXEC  (VM_READ | VM_WRITE | VM_MAYREAD | \
                                 VM_MAYWRITE | VM_MAYEXEC)
#define VM_DATA_FLAGS_EXEC      (VM_READ | VM_WRITE | VM_EXEC | \
                                 VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC)

#ifndef VM_DATA_DEFAULT_FLAGS           /* arch can override this */
#define VM_DATA_DEFAULT_FLAGS  VM_DATA_FLAGS_EXEC
#endif

#ifndef VM_STACK_DEFAULT_FLAGS          /* arch can override this */
#define VM_STACK_DEFAULT_FLAGS VM_DATA_DEFAULT_FLAGS
#endif

#ifdef CONFIG_STACK_GROWSUP
#define VM_STACK        VM_GROWSUP
#else
#define VM_STACK        VM_GROWSDOWN
#endif

#define VM_STACK_FLAGS  (VM_STACK | VM_STACK_DEFAULT_FLAGS | VM_ACCOUNT)

/* VMA basic access permission flags */
#define VM_ACCESS_FLAGS (VM_READ | VM_WRITE | VM_EXEC)


/*
 * Special vmas that are non-mergable, non-mlock()able.
 */
#define VM_SPECIAL (VM_IO | VM_DONTEXPAND | VM_PFNMAP | VM_MIXEDMAP)

/* This mask prevents VMA from being scanned with khugepaged */
#define VM_NO_KHUGEPAGED (VM_SPECIAL | VM_HUGETLB)

/* This mask defines which mm->def_flags a process can inherit its parent */
#define VM_INIT_DEF_MASK        VM_NOHUGEPAGE

/* This mask is used to clear all the VMA flags used by mlock */
#define VM_LOCKED_CLEAR_MASK    (~(VM_LOCKED | VM_LOCKONFAULT))

/* Arch-specific flags to clear when updating VM flags on protection change */
#ifndef VM_ARCH_CLEAR
# define VM_ARCH_CLEAR  VM_NONE
#endif
#define VM_FLAGS_CLEAR  (ARCH_VM_PKEY_FLAGS | VM_ARCH_CLEAR)

/*
 * mapping from the currently active vm_flags protection bits (the
 * low four bits) to a page protection mask..
 */
extern pgprot_t protection_map[16];

/**
 * 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.
 */
#define FAULT_FLAG_WRITE                        0x01
#define FAULT_FLAG_MKWRITE                      0x02
#define FAULT_FLAG_ALLOW_RETRY                  0x04
#define FAULT_FLAG_RETRY_NOWAIT                 0x08
#define FAULT_FLAG_KILLABLE                     0x10
#define FAULT_FLAG_TRIED                        0x20
#define FAULT_FLAG_USER                         0x40
#define FAULT_FLAG_REMOTE                       0x80
#define FAULT_FLAG_INSTRUCTION                  0x100
#define FAULT_FLAG_INTERRUPTIBLE                0x200

/*
 * The default fault flags that should be used by most of the
 * arch-specific page fault handlers.
 */
#define FAULT_FLAG_DEFAULT  (FAULT_FLAG_ALLOW_RETRY | \
                             FAULT_FLAG_KILLABLE | \
                             FAULT_FLAG_INTERRUPTIBLE)

/**
 * fault_flag_allow_retry_first - check ALLOW_RETRY the first time
 *
 * This is mostly used for places where we want to try to avoid taking
 * the mmap_lock for too long a time when waiting for another condition
 * to change, in which case we can try to be polite to release the
 * mmap_lock in the first round to avoid potential starvation of other
 * processes that would also want the mmap_lock.
 *
 * Return: true if the page fault allows retry and this is the first
 * attempt of the fault handling; false otherwise.
 */
static inline bool fault_flag_allow_retry_first(unsigned int flags)
{
        return (flags & FAULT_FLAG_ALLOW_RETRY) &&
            (!(flags & FAULT_FLAG_TRIED));
}

#define FAULT_FLAG_TRACE \
        { FAULT_FLAG_WRITE,             "WRITE" }, \
        { FAULT_FLAG_MKWRITE,           "MKWRITE" }, \
        { FAULT_FLAG_ALLOW_RETRY,       "ALLOW_RETRY" }, \
        { FAULT_FLAG_RETRY_NOWAIT,      "RETRY_NOWAIT" }, \
        { FAULT_FLAG_KILLABLE,          "KILLABLE" }, \
        { FAULT_FLAG_TRIED,             "TRIED" }, \
        { FAULT_FLAG_USER,              "USER" }, \
        { FAULT_FLAG_REMOTE,            "REMOTE" }, \
        { FAULT_FLAG_INSTRUCTION,       "INSTRUCTION" }, \
        { FAULT_FLAG_INTERRUPTIBLE,     "INTERRUPTIBLE" }

/*
 * vm_fault is filled by the pagefault handler and passed to the vma's
 * ->fault function. The vma's ->fault is responsible for returning a bitmask
 * of VM_FAULT_xxx flags that give details about how the fault was handled.
 *
 * MM layer fills up gfp_mask for page allocations but fault handler might
 * alter it if its implementation requires a different allocation context.
 *
 * pgoff should be used in favour of virtual_address, if possible.
 */
struct vm_fault {
        struct vm_area_struct *vma;     /* Target VMA */
        unsigned int flags;             /* FAULT_FLAG_xxx flags */
        gfp_t gfp_mask;                 /* gfp mask to be used for allocations */
        pgoff_t pgoff;                  /* Logical page offset based on vma */
        unsigned long address;          /* Faulting virtual address */
        pmd_t *pmd;                     /* Pointer to pmd entry matching
                                         * the 'address' */
        pud_t *pud;                     /* Pointer to pud entry matching
                                         * the 'address'
                                         */
        pte_t orig_pte;                 /* Value of PTE at the time of fault */

        struct page *cow_page;          /* Page handler may use for COW fault */
        struct page *page;              /* ->fault handlers should return a
                                         * page here, unless VM_FAULT_NOPAGE
                                         * is set (which is also implied by
                                         * VM_FAULT_ERROR).
                                         */
        /* These three entries are valid only while holding ptl lock */
        pte_t *pte;                     /* Pointer to pte entry matching
                                         * the 'address'. NULL if the page
                                         * table hasn't been allocated.
                                         */
        spinlock_t *ptl;                /* Page table lock.
                                         * Protects pte page table if 'pte'
                                         * is not NULL, otherwise pmd.
                                         */
        pgtable_t prealloc_pte;         /* Pre-allocated pte page table.
                                         * vm_ops->map_pages() calls
                                         * alloc_set_pte() from atomic context.
                                         * do_fault_around() pre-allocates
                                         * page table to avoid allocation from
                                         * atomic context.
                                         */
};

/* page entry size for vm->huge_fault() */
enum page_entry_size {
        PE_SIZE_PTE = 0,
        PE_SIZE_PMD,
        PE_SIZE_PUD,
};

/*
 * These are the virtual MM functions - opening of an area, closing and
 * unmapping it (needed to keep files on disk up-to-date etc), pointer
 * to the functions called when a no-page or a wp-page exception occurs.
 */
struct vm_operations_struct {
        void (*open)(struct vm_area_struct * area);
        void (*close)(struct vm_area_struct * area);
        /* Called any time before splitting to check if it's allowed */
        int (*may_split)(struct vm_area_struct *area, unsigned long addr);
        int (*mremap)(struct vm_area_struct *area, unsigned long flags);
        /*
         * Called by mprotect() to make driver-specific permission
         * checks before mprotect() is finalised.   The VMA must not
         * be modified.  Returns 0 if eprotect() can proceed.
         */
        int (*mprotect)(struct vm_area_struct *vma, unsigned long start,
                        unsigned long end, unsigned long newflags);
        vm_fault_t (*fault)(struct vm_fault *vmf);
        vm_fault_t (*huge_fault)(struct vm_fault *vmf,
                        enum page_entry_size pe_size);
        void (*map_pages)(struct vm_fault *vmf,
                        pgoff_t start_pgoff, pgoff_t end_pgoff);
        unsigned long (*pagesize)(struct vm_area_struct * area);

        /* notification that a previously read-only page is about to become
         * writable, if an error is returned it will cause a SIGBUS */
        vm_fault_t (*page_mkwrite)(struct vm_fault *vmf);

        /* same as page_mkwrite when using VM_PFNMAP|VM_MIXEDMAP */
        vm_fault_t (*pfn_mkwrite)(struct vm_fault *vmf);

        /* called by access_process_vm when get_user_pages() fails, typically
         * for use by special VMAs that can switch between memory and hardware
         */
        int (*access)(struct vm_area_struct *vma, unsigned long addr,
                      void *buf, int len, int write);

        /* Called by the /proc/PID/maps code to ask the vma whether it
         * has a special name.  Returning non-NULL will also cause this
         * vma to be dumped unconditionally. */
        const char *(*name)(struct vm_area_struct *vma);

#ifdef CONFIG_NUMA
        /*
         * set_policy() op must add a reference to any non-NULL @new mempolicy
         * to hold the policy upon return.  Caller should pass NULL @new to
         * remove a policy and fall back to surrounding context--i.e. do not
         * install a MPOL_DEFAULT policy, nor the task or system default
         * mempolicy.
         */
        int (*set_policy)(struct vm_area_struct *vma, struct mempolicy *new);

        /*
         * get_policy() op must add reference [mpol_get()] to any policy at
         * (vma,addr) marked as MPOL_SHARED.  The shared policy infrastructure
         * in mm/mempolicy.c will do this automatically.
         * get_policy() must NOT add a ref if the policy at (vma,addr) is not
         * marked as MPOL_SHARED. vma policies are protected by the mmap_lock.
         * If no [shared/vma] mempolicy exists at the addr, get_policy() op
         * must return NULL--i.e., do not "fallback" to task or system default
         * policy.
         */
        struct mempolicy *(*get_policy)(struct vm_area_struct *vma,
                                        unsigned long addr);
#endif
        /*
         * Called by vm_normal_page() for special PTEs to find the
         * page for @addr.  This is useful if the default behavior
         * (using pte_page()) would not find the correct page.
         */
        struct page *(*find_special_page)(struct vm_area_struct *vma,
                                          unsigned long addr);
};

static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *mm)
{
        static const struct vm_operations_struct dummy_vm_ops = {};

        memset(vma, 0, sizeof(*vma));
        vma->vm_mm = mm;
        vma->vm_ops = &dummy_vm_ops;
        INIT_LIST_HEAD(&vma->anon_vma_chain);
}

static inline void vma_set_anonymous(struct vm_area_struct *vma)
{
        vma->vm_ops = NULL;
}

static inline bool vma_is_anonymous(struct vm_area_struct *vma)
{
        return !vma->vm_ops;
}

static inline bool vma_is_temporary_stack(struct vm_area_struct *vma)
{
        int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP);

        if (!maybe_stack)
                return false;

        if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) ==
                                                VM_STACK_INCOMPLETE_SETUP)
                return true;

        return false;
}

static inline bool vma_is_foreign(struct vm_area_struct *vma)
{
        if (!current->mm)
                return true;

        if (current->mm != vma->vm_mm)
                return true;

        return false;
}

static inline bool vma_is_accessible(struct vm_area_struct *vma)
{
        return vma->vm_flags & VM_ACCESS_FLAGS;
}

#ifdef CONFIG_SHMEM
/*
 * The vma_is_shmem is not inline because it is used only by slow
 * paths in userfault.
 */
bool vma_is_shmem(struct vm_area_struct *vma);
#else
static inline bool vma_is_shmem(struct vm_area_struct *vma) { return false; }
#endif

int vma_is_stack_for_current(struct vm_area_struct *vma);

/* flush_tlb_range() takes a vma, not a mm, and can care about flags */
#define TLB_FLUSH_VMA(mm,flags) { .vm_mm = (mm), .vm_flags = (flags) }

struct mmu_gather;
struct inode;

#include <linux/huge_mm.h>

/*
 * Methods to modify the page usage count.
 *
 * What counts for a page usage:
 * - cache mapping   (page->mapping)
 * - private data    (page->private)
 * - page mapped in a task's page tables, each mapping
 *   is counted separately
 *
 * Also, many kernel routines increase the page count before a critical
 * routine so they can be sure the page doesn't go away from under them.
 */

/*
 * Drop a ref, return true if the refcount fell to zero (the page has no users)
 */
static inline int put_page_testzero(struct page *page)
{
        VM_BUG_ON_PAGE(page_ref_count(page) == 0, page);
        return page_ref_dec_and_test(page);
}

/*
 * Try to grab a ref unless the page has a refcount of zero, return false if
 * that is the case.
 * This can be called when MMU is off so it must not access
 * any of the virtual mappings.
 */
static inline int get_page_unless_zero(struct page *page)
{
        return page_ref_add_unless(page, 1, 0);
}

extern int page_is_ram(unsigned long pfn);

enum {
        REGION_INTERSECTS,
        REGION_DISJOINT,
        REGION_MIXED,
};

int region_intersects(resource_size_t offset, size_t size, unsigned long flags,
                      unsigned long desc);

/* Support for virtually mapped pages */
struct page *vmalloc_to_page(const void *addr);
unsigned long vmalloc_to_pfn(const void *addr);

/*
 * Determine if an address is within the vmalloc range
 *
 * On nommu, vmalloc/vfree wrap through kmalloc/kfree directly, so there
 * is no special casing required.
 */

#ifndef is_ioremap_addr
#define is_ioremap_addr(x) is_vmalloc_addr(x)
#endif

#ifdef CONFIG_MMU
extern bool is_vmalloc_addr(const void *x);
extern int is_vmalloc_or_module_addr(const void *x);
#else
static inline bool is_vmalloc_addr(const void *x)
{
        return false;
}
static inline int is_vmalloc_or_module_addr(const void *x)
{
        return 0;
}
#endif

extern void *kvmalloc_node(size_t size, gfp_t flags, int node);
static inline void *kvmalloc(size_t size, gfp_t flags)
{
        return kvmalloc_node(size, flags, NUMA_NO_NODE);
}
static inline void *kvzalloc_node(size_t size, gfp_t flags, int node)
{
        return kvmalloc_node(size, flags | __GFP_ZERO, node);
}
static inline void *kvzalloc(size_t size, gfp_t flags)
{
        return kvmalloc(size, flags | __GFP_ZERO);
}

static inline void *kvmalloc_array(size_t n, size_t size, gfp_t flags)
{
        size_t bytes;

        if (unlikely(check_mul_overflow(n, size, &bytes)))
                return NULL;

        return kvmalloc(bytes, flags);
}

static inline void *kvcalloc(size_t n, size_t size, gfp_t flags)
{
        return kvmalloc_array(n, size, flags | __GFP_ZERO);
}

extern void kvfree(const void *addr);
extern void kvfree_sensitive(const void *addr, size_t len);

static inline int head_compound_mapcount(struct page *head)
{
        return atomic_read(compound_mapcount_ptr(head)) + 1;
}

/*
 * Mapcount of compound page as a whole, does not include mapped sub-pages.
 *
 * Must be called only for compound pages or any their tail sub-pages.
 */
static inline int compound_mapcount(struct page *page)
{
        VM_BUG_ON_PAGE(!PageCompound(page), page);
        page = compound_head(page);
        return head_compound_mapcount(page);
}

/*
 * The atomic page->_mapcount, starts from -1: so that transitions
 * both from it and to it can be tracked, using atomic_inc_and_test
 * and atomic_add_negative(-1).
 */
static inline void page_mapcount_reset(struct page *page)
{
        atomic_set(&(page)->_mapcount, -1);
}

int __page_mapcount(struct page *page);

/*
 * Mapcount of 0-order page; when compound sub-page, includes
 * compound_mapcount().
 *
 * Result is undefined for pages which cannot be mapped into userspace.
 * For example SLAB or special types of pages. See function page_has_type().
 * They use this place in struct page differently.
 */
static inline int page_mapcount(struct page *page)
{
        if (unlikely(PageCompound(page)))
                return __page_mapcount(page);
        return atomic_read(&page->_mapcount) + 1;
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
int total_mapcount(struct page *page);
int page_trans_huge_mapcount(struct page *page, int *total_mapcount);
#else
static inline int total_mapcount(struct page *page)
{
        return page_mapcount(page);
}
static inline int page_trans_huge_mapcount(struct page *page,
                                           int *total_mapcount)
{
        int mapcount = page_mapcount(page);
        if (total_mapcount)
                *total_mapcount = mapcount;
        return mapcount;
}
#endif

static inline struct page *virt_to_head_page(const void *x)
{
        struct page *page = virt_to_page(x);

        return compound_head(page);
}

void __put_page(struct page *page);

void put_pages_list(struct list_head *pages);

void split_page(struct page *page, unsigned int order);

/*
 * Compound pages have a destructor function.  Provide a
 * prototype for that function and accessor functions.
 * These are _only_ valid on the head of a compound page.
 */
typedef void compound_page_dtor(struct page *);

/* Keep the enum in sync with compound_page_dtors array in mm/page_alloc.c */
enum compound_dtor_id {
        NULL_COMPOUND_DTOR,
        COMPOUND_PAGE_DTOR,
#ifdef CONFIG_HUGETLB_PAGE
        HUGETLB_PAGE_DTOR,
#endif
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
        TRANSHUGE_PAGE_DTOR,
#endif
        NR_COMPOUND_DTORS,
};
extern compound_page_dtor * const compound_page_dtors[NR_COMPOUND_DTORS];

static inline void set_compound_page_dtor(struct page *page,
                enum compound_dtor_id compound_dtor)
{
        VM_BUG_ON_PAGE(compound_dtor >= NR_COMPOUND_DTORS, page);
        page[1].compound_dtor = compound_dtor;
}

static inline void destroy_compound_page(struct page *page)
{
        VM_BUG_ON_PAGE(page[1].compound_dtor >= NR_COMPOUND_DTORS, page);
        compound_page_dtors[page[1].compound_dtor](page);
}

static inline unsigned int compound_order(struct page *page)
{
        if (!PageHead(page))
                return 0;
        return page[1].compound_order;
}

static inline bool hpage_pincount_available(struct page *page)
{
        /*
         * Can the page->hpage_pinned_refcount field be used? That field is in
         * the 3rd page of the compound page, so the smallest (2-page) compound
         * pages cannot support it.
         */
        page = compound_head(page);
        return PageCompound(page) && compound_order(page) > 1;
}

static inline int head_compound_pincount(struct page *head)
{
        return atomic_read(compound_pincount_ptr(head));
}

static inline int compound_pincount(struct page *page)
{
        VM_BUG_ON_PAGE(!hpage_pincount_available(page), page);
        page = compound_head(page);
        return head_compound_pincount(page);
}

static inline void set_compound_order(struct page *page, unsigned int order)
{
        page[1].compound_order = order;
        page[1].compound_nr = 1U << order;
}

/* Returns the number of pages in this potentially compound page. */
static inline unsigned long compound_nr(struct page *page)
{
        if (!PageHead(page))
                return 1;
        return page[1].compound_nr;
}

/* Returns the number of bytes in this potentially compound page. */
static inline unsigned long page_size(struct page *page)
{
        return PAGE_SIZE << compound_order(page);
}

/* Returns the number of bits needed for the number of bytes in a page */
static inline unsigned int page_shift(struct page *page)
{
        return PAGE_SHIFT + compound_order(page);
}

void free_compound_page(struct page *page);

#ifdef CONFIG_MMU
/*
 * Do pte_mkwrite, but only if the vma says VM_WRITE.  We do this when
 * servicing faults for write access.  In the normal case, do always want
 * pte_mkwrite.  But get_user_pages can cause write faults for mappings
 * that do not have writing enabled, when used by access_process_vm.
 */
static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
{
        if (likely(vma->vm_flags & VM_WRITE))
                pte = pte_mkwrite(pte);
        return pte;
}

vm_fault_t alloc_set_pte(struct vm_fault *vmf, struct page *page);
vm_fault_t finish_fault(struct vm_fault *vmf);
vm_fault_t finish_mkwrite_fault(struct vm_fault *vmf);
#endif

/*
 * Multiple processes may "see" the same page. E.g. for untouched
 * mappings of /dev/null, all processes see the same page full of
 * zeroes, and text pages of executables and shared libraries have
 * only one copy in memory, at most, normally.
 *
 * For the non-reserved pages, page_count(page) denotes a reference count.
 *   page_count() == 0 means the page is free. page->lru is then used for
 *   freelist management in the buddy allocator.
 *   page_count() > 0  means the page has been allocated.
 *
 * Pages are allocated by the slab allocator in order to provide memory
 * to kmalloc and kmem_cache_alloc. In this case, the management of the
 * page, and the fields in 'struct page' are the responsibility of mm/slab.c
 * unless a particular usage is carefully commented. (the responsibility of
 * freeing the kmalloc memory is the caller's, of course).
 *
 * A page may be used by anyone else who does a __get_free_page().
 * In this case, page_count still tracks the references, and should only
 * be used through the normal accessor functions. The top bits of page->flags
 * and page->virtual store page management information, but all other fields
 * are unused and could be used privately, carefully. The management of this
 * page is the responsibility of the one who allocated it, and those who have
 * subsequently been given references to it.
 *
 * The other pages (we may call them "pagecache pages") are completely
 * managed by the Linux memory manager: I/O, buffers, swapping etc.
 * The following discussion applies only to them.
 *
 * A pagecache page contains an opaque `private' member, which belongs to the
 * page's address_space. Usually, this is the address of a circular list of
 * the page's disk buffers. PG_private must be set to tell the VM to call
 * into the filesystem to release these pages.
 *
 * A page may belong to an inode's memory mapping. In this case, page->mapping
 * is the pointer to the inode, and page->index is the file offset of the page,
 * in units of PAGE_SIZE.
 *
 * If pagecache pages are not associated with an inode, they are said to be
 * anonymous pages. These may become associated with the swapcache, and in that
 * case PG_swapcache is set, and page->private is an offset into the swapcache.
 *
 * In either case (swapcache or inode backed), the pagecache itself holds one
 * reference to the page. Setting PG_private should also increment the
 * refcount. The each user mapping also has a reference to the page.
 *
 * The pagecache pages are stored in a per-mapping radix tree, which is
 * rooted at mapping->i_pages, and indexed by offset.
 * Where 2.4 and early 2.6 kernels kept dirty/clean pages in per-address_space
 * lists, we instead now tag pages as dirty/writeback in the radix tree.
 *
 * All pagecache pages may be subject to I/O:
 * - inode pages may need to be read from disk,
 * - inode pages which have been modified and are MAP_SHARED may need
 *   to be written back to the inode on disk,
 * - anonymous pages (including MAP_PRIVATE file mappings) which have been
 *   modified may need to be swapped out to swap space and (later) to be read
 *   back into memory.
 */

/*
 * The zone field is never updated after free_area_init_core()
 * sets it, so none of the operations on it need to be atomic.
 */

/* Page flags: | [SECTION] | [NODE] | ZONE | [LAST_CPUPID] | ... | FLAGS | */
#define SECTIONS_PGOFF          ((sizeof(unsigned long)*8) - SECTIONS_WIDTH)
#define NODES_PGOFF             (SECTIONS_PGOFF - NODES_WIDTH)
#define ZONES_PGOFF             (NODES_PGOFF - ZONES_WIDTH)
#define LAST_CPUPID_PGOFF       (ZONES_PGOFF - LAST_CPUPID_WIDTH)
#define KASAN_TAG_PGOFF         (LAST_CPUPID_PGOFF - KASAN_TAG_WIDTH)

/*
 * Define the bit shifts to access each section.  For non-existent
 * sections we define the shift as 0; that plus a 0 mask ensures
 * the compiler will optimise away reference to them.
 */
#define SECTIONS_PGSHIFT        (SECTIONS_PGOFF * (SECTIONS_WIDTH != 0))
#define NODES_PGSHIFT           (NODES_PGOFF * (NODES_WIDTH != 0))
#define ZONES_PGSHIFT           (ZONES_PGOFF * (ZONES_WIDTH != 0))
#define LAST_CPUPID_PGSHIFT     (LAST_CPUPID_PGOFF * (LAST_CPUPID_WIDTH != 0))
#define KASAN_TAG_PGSHIFT       (KASAN_TAG_PGOFF * (KASAN_TAG_WIDTH != 0))

/* NODE:ZONE or SECTION:ZONE is used to ID a zone for the buddy allocator */
#ifdef NODE_NOT_IN_PAGE_FLAGS
#define ZONEID_SHIFT            (SECTIONS_SHIFT + ZONES_SHIFT)
#define ZONEID_PGOFF            ((SECTIONS_PGOFF < ZONES_PGOFF)? \
                                                SECTIONS_PGOFF : ZONES_PGOFF)
#else
#define ZONEID_SHIFT            (NODES_SHIFT + ZONES_SHIFT)
#define ZONEID_PGOFF            ((NODES_PGOFF < ZONES_PGOFF)? \
                                                NODES_PGOFF : ZONES_PGOFF)
#endif

#define ZONEID_PGSHIFT          (ZONEID_PGOFF * (ZONEID_SHIFT != 0))

#define ZONES_MASK              ((1UL << ZONES_WIDTH) - 1)
#define NODES_MASK              ((1UL << NODES_WIDTH) - 1)
#define SECTIONS_MASK           ((1UL << SECTIONS_WIDTH) - 1)
#define LAST_CPUPID_MASK        ((1UL << LAST_CPUPID_SHIFT) - 1)
#define KASAN_TAG_MASK          ((1UL << KASAN_TAG_WIDTH) - 1)
#define ZONEID_MASK             ((1UL << ZONEID_SHIFT) - 1)

static inline enum zone_type page_zonenum(const struct page *page)
{
        ASSERT_EXCLUSIVE_BITS(page->flags, ZONES_MASK << ZONES_PGSHIFT);
        return (page->flags >> ZONES_PGSHIFT) & ZONES_MASK;
}

#ifdef CONFIG_ZONE_DEVICE
static inline bool is_zone_device_page(const struct page *page)
{
        return page_zonenum(page) == ZONE_DEVICE;
}
extern void memmap_init_zone_device(struct zone *, unsigned long,
                                    unsigned long, struct dev_pagemap *);
#else
static inline bool is_zone_device_page(const struct page *page)
{
        return false;
}
#endif

#ifdef CONFIG_DEV_PAGEMAP_OPS
void free_devmap_managed_page(struct page *page);
DECLARE_STATIC_KEY_FALSE(devmap_managed_key);

static inline bool page_is_devmap_managed(struct page *page)
{
        if (!static_branch_unlikely(&devmap_managed_key))
                return false;
        if (!is_zone_device_page(page))
                return false;
        switch (page->pgmap->type) {
        case MEMORY_DEVICE_PRIVATE:
        case MEMORY_DEVICE_FS_DAX:
                return true;
        default:
                break;
        }
        return false;
}

void put_devmap_managed_page(struct page *page);

#else /* CONFIG_DEV_PAGEMAP_OPS */
static inline bool page_is_devmap_managed(struct page *page)
{
        return false;
}

static inline void put_devmap_managed_page(struct page *page)
{
}
#endif /* CONFIG_DEV_PAGEMAP_OPS */

static inline bool is_device_private_page(const struct page *page)
{
        return IS_ENABLED(CONFIG_DEV_PAGEMAP_OPS) &&
                IS_ENABLED(CONFIG_DEVICE_PRIVATE) &&
                is_zone_device_page(page) &&
                page->pgmap->type == MEMORY_DEVICE_PRIVATE;
}

static inline bool is_pci_p2pdma_page(const struct page *page)
{
        return IS_ENABLED(CONFIG_DEV_PAGEMAP_OPS) &&
                IS_ENABLED(CONFIG_PCI_P2PDMA) &&
                is_zone_device_page(page) &&
                page->pgmap->type == MEMORY_DEVICE_PCI_P2PDMA;
}

/* 127: arbitrary random number, small enough to assemble well */
#define page_ref_zero_or_close_to_overflow(page) \
        ((unsigned int) page_ref_count(page) + 127u <= 127u)

static inline void get_page(struct page *page)
{
        page = compound_head(page);
        /*
         * Getting a normal page or the head of a compound page
         * requires to already have an elevated page->_refcount.
         */
        VM_BUG_ON_PAGE(page_ref_zero_or_close_to_overflow(page), page);
        page_ref_inc(page);
}

bool __must_check try_grab_page(struct page *page, unsigned int flags);

static inline __must_check bool try_get_page(struct page *page)
{
        page = compound_head(page);
        if (WARN_ON_ONCE(page_ref_count(page) <= 0))
                return false;
        page_ref_inc(page);
        return true;
}

static inline void put_page(struct page *page)
{
        page = compound_head(page);

        /*
         * For devmap managed pages we need to catch refcount transition from
         * 2 to 1, when refcount reach one it means the page is free and we
         * need to inform the device driver through callback. See
         * include/linux/memremap.h and HMM for details.
         */
        if (page_is_devmap_managed(page)) {
                put_devmap_managed_page(page);
                return;
        }

        if (put_page_testzero(page))
                __put_page(page);
}

/*
 * GUP_PIN_COUNTING_BIAS, and the associated functions that use it, overload
 * the page's refcount so that two separate items are tracked: the original page
 * reference count, and also a new count of how many pin_user_pages() calls were
 * made against the page. ("gup-pinned" is another term for the latter).
 *
 * With this scheme, pin_user_pages() becomes special: such pages are marked as
 * distinct from normal pages. As such, the unpin_user_page() call (and its
 * variants) must be used in order to release gup-pinned pages.
 *
 * Choice of value:
 *
 * By making GUP_PIN_COUNTING_BIAS a power of two, debugging of page reference
 * counts with respect to pin_user_pages() and unpin_user_page() becomes
 * simpler, due to the fact that adding an even power of two to the page
 * refcount has the effect of using only the upper N bits, for the code that
 * counts up using the bias value. This means that the lower bits are left for
 * the exclusive use of the original code that increments and decrements by one
 * (or at least, by much smaller values than the bias value).
 *
 * Of course, once the lower bits overflow into the upper bits (and this is
 * OK, because subtraction recovers the original values), then visual inspection
 * no longer suffices to directly view the separate counts. However, for normal
 * applications that don't have huge page reference counts, this won't be an
 * issue.
 *
 * Locking: the lockless algorithm described in page_cache_get_speculative()
 * and page_cache_gup_pin_speculative() provides safe operation for
 * get_user_pages and page_mkclean and other calls that race to set up page
 * table entries.
 */
#define GUP_PIN_COUNTING_BIAS (1U << 10)

void unpin_user_page(struct page *page);
void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages,
                                 bool make_dirty);
void unpin_user_pages(struct page **pages, unsigned long npages);

/**
 * page_maybe_dma_pinned() - report if a page is pinned for DMA.
 *
 * This function checks if a page has been pinned via a call to
 * pin_user_pages*().
 *
 * For non-huge pages, the return value is partially fuzzy: false is not fuzzy,
 * because it means "definitely not pinned for DMA", but true means "probably
 * pinned for DMA, but possibly a false positive due to having at least
 * GUP_PIN_COUNTING_BIAS worth of normal page references".
 *
 * False positives are OK, because: a) it's unlikely for a page to get that many
 * refcounts, and b) all the callers of this routine are expected to be able to
 * deal gracefully with a false positive.
 *
 * For huge pages, the result will be exactly correct. That's because we have
 * more tracking data available: the 3rd struct page in the compound page is
 * used to track the pincount (instead using of the GUP_PIN_COUNTING_BIAS
 * scheme).
 *
 * For more information, please see Documentation/core-api/pin_user_pages.rst.
 *
 * @page:       pointer to page to be queried.
 * @Return:     True, if it is likely that the page has been "dma-pinned".
 *              False, if the page is definitely not dma-pinned.
 */
static inline bool page_maybe_dma_pinned(struct page *page)
{
        if (hpage_pincount_available(page))
                return compound_pincount(page) > 0;

        /*
         * page_ref_count() is signed. If that refcount overflows, then
         * page_ref_count() returns a negative value, and callers will avoid
         * further incrementing the refcount.
         *
         * Here, for that overflow case, use the signed bit to count a little
         * bit higher via unsigned math, and thus still get an accurate result.
         */
        return ((unsigned int)page_ref_count(compound_head(page))) >=
                GUP_PIN_COUNTING_BIAS;
}

#if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
#define SECTION_IN_PAGE_FLAGS
#endif

/*
 * The identification function is mainly used by the buddy allocator for
 * determining if two pages could be buddies. We are not really identifying
 * the zone since we could be using the section number id if we do not have
 * node id available in page flags.
 * We only guarantee that it will return the same value for two combinable
 * pages in a zone.
 */
static inline int page_zone_id(struct page *page)
{
        return (page->flags >> ZONEID_PGSHIFT) & ZONEID_MASK;
}

#ifdef NODE_NOT_IN_PAGE_FLAGS
extern int page_to_nid(const struct page *page);
#else
static inline int page_to_nid(const struct page *page)
{
        struct page *p = (struct page *)page;

        return (PF_POISONED_CHECK(p)->flags >> NODES_PGSHIFT) & NODES_MASK;
}
#endif

#ifdef CONFIG_NUMA_BALANCING
static inline int cpu_pid_to_cpupid(int cpu, int pid)
{
        return ((cpu & LAST__CPU_MASK) << LAST__PID_SHIFT) | (pid & LAST__PID_MASK);
}

static inline int cpupid_to_pid(int cpupid)
{
        return cpupid & LAST__PID_MASK;
}

static inline int cpupid_to_cpu(int cpupid)
{
        return (cpupid >> LAST__PID_SHIFT) & LAST__CPU_MASK;
}

static inline int cpupid_to_nid(int cpupid)
{
        return cpu_to_node(cpupid_to_cpu(cpupid));
}

static inline bool cpupid_pid_unset(int cpupid)
{
        return cpupid_to_pid(cpupid) == (-1 & LAST__PID_MASK);
}

static inline bool cpupid_cpu_unset(int cpupid)
{
        return cpupid_to_cpu(cpupid) == (-1 & LAST__CPU_MASK);
}

static inline bool __cpupid_match_pid(pid_t task_pid, int cpupid)
{
        return (task_pid & LAST__PID_MASK) == cpupid_to_pid(cpupid);
}

#define cpupid_match_pid(task, cpupid) __cpupid_match_pid(task->pid, cpupid)
#ifdef LAST_CPUPID_NOT_IN_PAGE_FLAGS
static inline int page_cpupid_xchg_last(struct page *page, int cpupid)
{
        return xchg(&page->_last_cpupid, cpupid & LAST_CPUPID_MASK);
}

static inline int page_cpupid_last(struct page *page)
{
        return page->_last_cpupid;
}
static inline void page_cpupid_reset_last(struct page *page)
{
        page->_last_cpupid = -1 & LAST_CPUPID_MASK;
}
#else
static inline int page_cpupid_last(struct page *page)
{
        return (page->flags >> LAST_CPUPID_PGSHIFT) & LAST_CPUPID_MASK;
}

extern int page_cpupid_xchg_last(struct page *page, int cpupid);

static inline void page_cpupid_reset_last(struct page *page)
{
        page->flags |= LAST_CPUPID_MASK << LAST_CPUPID_PGSHIFT;
}
#endif /* LAST_CPUPID_NOT_IN_PAGE_FLAGS */
#else /* !CONFIG_NUMA_BALANCING */
static inline int page_cpupid_xchg_last(struct page *page, int cpupid)
{
        return page_to_nid(page); /* XXX */
}

static inline int page_cpupid_last(struct page *page)
{
        return page_to_nid(page); /* XXX */
}

static inline int cpupid_to_nid(int cpupid)
{
        return -1;
}

static inline int cpupid_to_pid(int cpupid)
{
        return -1;
}

static inline int cpupid_to_cpu(int cpupid)
{
        return -1;
}

static inline int cpu_pid_to_cpupid(int nid, int pid)
{
        return -1;
}

static inline bool cpupid_pid_unset(int cpupid)
{
        return true;
}

static inline void page_cpupid_reset_last(struct page *page)
{
}

static inline bool cpupid_match_pid(struct task_struct *task, int cpupid)
{
        return false;
}
#endif /* CONFIG_NUMA_BALANCING */

#if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS)

static inline u8 page_kasan_tag(const struct page *page)
{
        if (kasan_enabled())
                return (page->flags >> KASAN_TAG_PGSHIFT) & KASAN_TAG_MASK;
        return 0xff;
}

static inline void page_kasan_tag_set(struct page *page, u8 tag)
{
        if (kasan_enabled()) {
                page->flags &= ~(KASAN_TAG_MASK << KASAN_TAG_PGSHIFT);
                page->flags |= (tag & KASAN_TAG_MASK) << KASAN_TAG_PGSHIFT;
        }
}

static inline void page_kasan_tag_reset(struct page *page)
{
        if (kasan_enabled())
                page_kasan_tag_set(page, 0xff);
}

#else /* CONFIG_KASAN_SW_TAGS || CONFIG_KASAN_HW_TAGS */

static inline u8 page_kasan_tag(const struct page *page)
{
        return 0xff;
}

static inline void page_kasan_tag_set(struct page *page, u8 tag) { }
static inline void page_kasan_tag_reset(struct page *page) { }

#endif /* CONFIG_KASAN_SW_TAGS || CONFIG_KASAN_HW_TAGS */

static inline struct zone *page_zone(const struct page *page)
{
        return &NODE_DATA(page_to_nid(page))->node_zones[page_zonenum(page)];
}

static inline pg_data_t *page_pgdat(const struct page *page)
{
        return NODE_DATA(page_to_nid(page));
}

#ifdef SECTION_IN_PAGE_FLAGS
static inline void set_page_section(struct page *page, unsigned long section)
{
        page->flags &= ~(SECTIONS_MASK << SECTIONS_PGSHIFT);
        page->flags |= (section & SECTIONS_MASK) << SECTIONS_PGSHIFT;
}

static inline unsigned long page_to_section(const struct page *page)
{
        return (page->flags >> SECTIONS_PGSHIFT) & SECTIONS_MASK;
}
#endif

static inline void set_page_zone(struct page *page, enum zone_type zone)
{
        page->flags &= ~(ZONES_MASK << ZONES_PGSHIFT);
        page->flags |= (zone & ZONES_MASK) << ZONES_PGSHIFT;
}

static inline void set_page_node(struct page *page, unsigned long node)
{
        page->flags &= ~(NODES_MASK << NODES_PGSHIFT);
        page->flags |= (node & NODES_MASK) << NODES_PGSHIFT;
}

static inline void set_page_links(struct page *page, enum zone_type zone,
        unsigned long node, unsigned long pfn)
{
        set_page_zone(page, zone);
        set_page_node(page, node);
#ifdef SECTION_IN_PAGE_FLAGS
        set_page_section(page, pfn_to_section_nr(pfn));
#endif
}

/*
 * Some inline functions in vmstat.h depend on page_zone()
 */
#include <linux/vmstat.h>

static __always_inline void *lowmem_page_address(const struct page *page)
{
        return page_to_virt(page);
}

#if defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL)
#define HASHED_PAGE_VIRTUAL
#endif

#if defined(WANT_PAGE_VIRTUAL)
static inline void *page_address(const struct page *page)
{
        return page->virtual;
}
static inline void set_page_address(struct page *page, void *address)
{
        page->virtual = address;
}
#define page_address_init()  do { } while(0)
#endif

#if defined(HASHED_PAGE_VIRTUAL)
void *page_address(const struct page *page);
void set_page_address(struct page *page, void *virtual);
void page_address_init(void);
#endif

#if !defined(HASHED_PAGE_VIRTUAL) && !defined(WANT_PAGE_VIRTUAL)
#define page_address(page) lowmem_page_address(page)
#define set_page_address(page, address)  do { } while(0)
#define page_address_init()  do { } while(0)
#endif

extern void *page_rmapping(struct page *page);
extern struct anon_vma *page_anon_vma(struct page *page);
extern struct address_space *page_mapping(struct page *page);

extern struct address_space *__page_file_mapping(struct page *);

static inline
struct address_space *page_file_mapping(struct page *page)
{
        if (unlikely(PageSwapCache(page)))
                return __page_file_mapping(page);

        return page->mapping;
}

extern pgoff_t __page_file_index(struct page *page);

/*
 * Return the pagecache index of the passed page.  Regular pagecache pages
 * use ->index whereas swapcache pages use swp_offset(->private)
 */
static inline pgoff_t page_index(struct page *page)
{
        if (unlikely(PageSwapCache(page)))
                return __page_file_index(page);
        return page->index;
}

bool page_mapped(struct page *page);
struct address_space *page_mapping(struct page *page);
struct address_space *page_mapping_file(struct page *page);

/*
 * Return true only if the page has been allocated with
 * ALLOC_NO_WATERMARKS and the low watermark was not
 * met implying that the system is under some pressure.
 */
static inline bool page_is_pfmemalloc(struct page *page)
{
        /*
         * Page index cannot be this large so this must be
         * a pfmemalloc page.
         */
        return page->index == -1UL;
}

/*
 * Only to be called by the page allocator on a freshly allocated
 * page.
 */
static inline void set_page_pfmemalloc(struct page *page)
{
        page->index = -1UL;
}

static inline void clear_page_pfmemalloc(struct page *page)
{
        page->index = 0;
}

/*
 * Can be called by the pagefault handler when it gets a VM_FAULT_OOM.
 */
extern void pagefault_out_of_memory(void);

#define offset_in_page(p)       ((unsigned long)(p) & ~PAGE_MASK)
#define offset_in_thp(page, p)  ((unsigned long)(p) & (thp_size(page) - 1))

/*
 * Flags passed to show_mem() and show_free_areas() to suppress output in
 * various contexts.
 */
#define SHOW_MEM_FILTER_NODES           (0x0001u)       /* disallowed nodes */

extern void show_free_areas(unsigned int flags, nodemask_t *nodemask);

#ifdef CONFIG_MMU
extern bool can_do_mlock(void);
#else
static inline bool can_do_mlock(void) { return false; }
#endif
extern int user_shm_lock(size_t, struct user_struct *);
extern void user_shm_unlock(size_t, struct user_struct *);

/*
 * Parameter block passed down to zap_pte_range in exceptional cases.
 */
struct zap_details {
        struct address_space *check_mapping;    /* Check page->mapping if set */
        pgoff_t first_index;                    /* Lowest page->index to unmap */
        pgoff_t last_index;                     /* Highest page->index to unmap */
};

struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
                             pte_t pte);
struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,
                                pmd_t pmd);

void zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
                  unsigned long size);
void zap_page_range(struct vm_area_struct *vma, unsigned long address,
                    unsigned long size);
void unmap_vmas(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
                unsigned long start, unsigned long end);

struct mmu_notifier_range;

void free_pgd_range(struct mmu_gather *tlb, unsigned long addr,
                unsigned long end, unsigned long floor, unsigned long ceiling);
int
copy_page_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma);
int follow_pte(struct mm_struct *mm, unsigned long address,
                struct mmu_notifier_range *range, pte_t **ptepp, pmd_t **pmdpp,
                spinlock_t **ptlp);
int follow_pfn(struct vm_area_struct *vma, unsigned long address,
        unsigned long *pfn);
int follow_phys(struct vm_area_struct *vma, unsigned long address,
                unsigned int flags, unsigned long *prot, resource_size_t *phys);
int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
                        void *buf, int len, int write);

extern void truncate_pagecache(struct inode *inode, loff_t new);
extern void truncate_setsize(struct inode *inode, loff_t newsize);
void pagecache_isize_extended(struct inode *inode, loff_t from, loff_t to);
void truncate_pagecache_range(struct inode *inode, loff_t offset, loff_t end);
int truncate_inode_page(struct address_space *mapping, struct page *page);
int generic_error_remove_page(struct address_space *mapping, struct page *page);
int invalidate_inode_page(struct page *page);

#ifdef CONFIG_MMU
extern vm_fault_t handle_mm_fault(struct vm_area_struct *vma,
                                  unsigned long address, unsigned int flags,
                                  struct pt_regs *regs);
extern int fixup_user_fault(struct mm_struct *mm,
                            unsigned long address, unsigned int fault_flags,
                            bool *unlocked);
void unmap_mapping_pages(struct address_space *mapping,
                pgoff_t start, pgoff_t nr, bool even_cows);
void unmap_mapping_range(struct address_space *mapping,
                loff_t const holebegin, loff_t const holelen, int even_cows);
#else
static inline vm_fault_t handle_mm_fault(struct vm_area_struct *vma,
                                         unsigned long address, unsigned int flags,
                                         struct pt_regs *regs)
{
        /* should never happen if there's no MMU */
        BUG();
        return VM_FAULT_SIGBUS;
}
static inline int fixup_user_fault(struct mm_struct *mm, unsigned long address,
                unsigned int fault_flags, bool *unlocked)
{
        /* should never happen if there's no MMU */
        BUG();
        return -EFAULT;
}
static inline void unmap_mapping_pages(struct address_space *mapping,
                pgoff_t start, pgoff_t nr, bool even_cows) { }
static inline void unmap_mapping_range(struct address_space *mapping,
                loff_t const holebegin, loff_t const holelen, int even_cows) { }
#endif

static inline void unmap_shared_mapping_range(struct address_space *mapping,
                loff_t const holebegin, loff_t const holelen)
{
        unmap_mapping_range(mapping, holebegin, holelen, 0);
}

extern int access_process_vm(struct task_struct *tsk, unsigned long addr,
                void *buf, int len, unsigned int gup_flags);
extern int access_remote_vm(struct mm_struct *mm, unsigned long addr,
                void *buf, int len, unsigned int gup_flags);
extern int __access_remote_vm(struct mm_struct *mm, unsigned long addr,
                              void *buf, int len, unsigned int gup_flags);

long get_user_pages_remote(struct mm_struct *mm,
                            unsigned long start, unsigned long nr_pages,
                            unsigned int gup_flags, struct page **pages,
                            struct vm_area_struct **vmas, int *locked);
long pin_user_pages_remote(struct mm_struct *mm,
                           unsigned long start, unsigned long nr_pages,
                           unsigned int gup_flags, struct page **pages,
                           struct vm_area_struct **vmas, int *locked);
long get_user_pages(unsigned long start, unsigned long nr_pages,
                            unsigned int gup_flags, struct page **pages,
                            struct vm_area_struct **vmas);
long pin_user_pages(unsigned long start, unsigned long nr_pages,
                    unsigned int gup_flags, struct page **pages,
                    struct vm_area_struct **vmas);
long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
                    unsigned int gup_flags, struct page **pages, int *locked);
long pin_user_pages_locked(unsigned long start, unsigned long nr_pages,
                    unsigned int gup_flags, struct page **pages, int *locked);
long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
                    struct page **pages, unsigned int gup_flags);
long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
                    struct page **pages, unsigned int gup_flags);

int get_user_pages_fast(unsigned long start, int nr_pages,
                        unsigned int gup_flags, struct page **pages);
int pin_user_pages_fast(unsigned long start, int nr_pages,
                        unsigned int gup_flags, struct page **pages);

int account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc);
int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc,
                        struct task_struct *task, bool bypass_rlim);

/* Container for pinned pfns / pages */
struct frame_vector {
        unsigned int nr_allocated;      /* Number of frames we have space for */
        unsigned int nr_frames; /* Number of frames stored in ptrs array */
        bool got_ref;           /* Did we pin pages by getting page ref? */
        bool is_pfns;           /* Does array contain pages or pfns? */
        void *ptrs[];           /* Array of pinned pfns / pages. Use
                                 * pfns_vector_pages() or pfns_vector_pfns()
                                 * for access */
};

struct frame_vector *frame_vector_create(unsigned int nr_frames);
void frame_vector_destroy(struct frame_vector *vec);
int get_vaddr_frames(unsigned long start, unsigned int nr_pfns,
                     unsigned int gup_flags, struct frame_vector *vec);
void put_vaddr_frames(struct frame_vector *vec);
int frame_vector_to_pages(struct frame_vector *vec);
void frame_vector_to_pfns(struct frame_vector *vec);

static inline unsigned int frame_vector_count(struct frame_vector *vec)
{
        return vec->nr_frames;
}

static inline struct page **frame_vector_pages(struct frame_vector *vec)
{
        if (vec->is_pfns) {
                int err = frame_vector_to_pages(vec);

                if (err)
                        return ERR_PTR(err);
        }
        return (struct page **)(vec->ptrs);
}

static inline unsigned long *frame_vector_pfns(struct frame_vector *vec)
{
        if (!vec->is_pfns)
                frame_vector_to_pfns(vec);
        return (unsigned long *)(vec->ptrs);
}

struct kvec;
int get_kernel_pages(const struct kvec *iov, int nr_pages, int write,
                        struct page **pages);
int get_kernel_page(unsigned long start, int write, struct page **pages);
struct page *get_dump_page(unsigned long addr);

extern int try_to_release_page(struct page * page, gfp_t gfp_mask);
extern void do_invalidatepage(struct page *page, unsigned int offset,
                              unsigned int length);

void __set_page_dirty(struct page *, struct address_space *, int warn);
int __set_page_dirty_nobuffers(struct page *page);
int __set_page_dirty_no_writeback(struct page *page);
int redirty_page_for_writepage(struct writeback_control *wbc,
                                struct page *page);
void account_page_dirtied(struct page *page, struct address_space *mapping);
void account_page_cleaned(struct page *page, struct address_space *mapping,
                          struct bdi_writeback *wb);
int set_page_dirty(struct page *page);
int set_page_dirty_lock(struct page *page);
void __cancel_dirty_page(struct page *page);
static inline void cancel_dirty_page(struct page *page)
{
        /* Avoid atomic ops, locking, etc. when not actually needed. */
        if (PageDirty(page))
                __cancel_dirty_page(page);
}
int clear_page_dirty_for_io(struct page *page);

int get_cmdline(struct task_struct *task, char *buffer, int buflen);

extern unsigned long move_page_tables(struct vm_area_struct *vma,
                unsigned long old_addr, struct vm_area_struct *new_vma,
                unsigned long new_addr, unsigned long len,
                bool need_rmap_locks);

/*
 * Flags used by change_protection().  For now we make it a bitmap so
 * that we can pass in multiple flags just like parameters.  However
 * for now all the callers are only use one of the flags at the same
 * time.
 */
/* Whether we should allow dirty bit accounting */
#define  MM_CP_DIRTY_ACCT                  (1UL << 0)
/* Whether this protection change is for NUMA hints */
#define  MM_CP_PROT_NUMA                   (1UL << 1)
/* Whether this change is for write protecting */
#define  MM_CP_UFFD_WP                     (1UL << 2) /* do wp */
#define  MM_CP_UFFD_WP_RESOLVE             (1UL << 3) /* Resolve wp */
#define  MM_CP_UFFD_WP_ALL                 (MM_CP_UFFD_WP | \
                                            MM_CP_UFFD_WP_RESOLVE)

extern unsigned long change_protection(struct vm_area_struct *vma, unsigned long start,
                              unsigned long end, pgprot_t newprot,
                              unsigned long cp_flags);
extern int mprotect_fixup(struct vm_area_struct *vma,
                          struct vm_area_struct **pprev, unsigned long start,
                          unsigned long end, unsigned long newflags);

/*
 * doesn't attempt to fault and will return short.
 */
int get_user_pages_fast_only(unsigned long start, int nr_pages,
                             unsigned int gup_flags, struct page **pages);
int pin_user_pages_fast_only(unsigned long start, int nr_pages,
                             unsigned int gup_flags, struct page **pages);

static inline bool get_user_page_fast_only(unsigned long addr,
                        unsigned int gup_flags, struct page **pagep)
{
        return get_user_pages_fast_only(addr, 1, gup_flags, pagep) == 1;
}
/*
 * per-process(per-mm_struct) statistics.
 */
static inline unsigned long get_mm_counter(struct mm_struct *mm, int member)
{
        long val = atomic_long_read(&mm->rss_stat.count[member]);

#ifdef SPLIT_RSS_COUNTING
        /*
         * counter is updated in asynchronous manner and may go to minus.
         * But it's never be expected number for users.
         */
        if (val < 0)
                val = 0;
#endif
        return (unsigned long)val;
}

void mm_trace_rss_stat(struct mm_struct *mm, int member, long count);

static inline void add_mm_counter(struct mm_struct *mm, int member, long value)
{
        long count = atomic_long_add_return(value, &mm->rss_stat.count[member]);

        mm_trace_rss_stat(mm, member, count);
}

static inline void inc_mm_counter(struct mm_struct *mm, int member)
{
        long count = atomic_long_inc_return(&mm->rss_stat.count[member]);

        mm_trace_rss_stat(mm, member, count);
}

static inline void dec_mm_counter(struct mm_struct *mm, int member)
{
        long count = atomic_long_dec_return(&mm->rss_stat.count[member]);

        mm_trace_rss_stat(mm, member, count);
}

/* Optimized variant when page is already known not to be PageAnon */
static inline int mm_counter_file(struct page *page)
{
        if (PageSwapBacked(page))
                return MM_SHMEMPAGES;
        return MM_FILEPAGES;
}

static inline int mm_counter(struct page *page)
{
        if (PageAnon(page))
                return MM_ANONPAGES;
        return mm_counter_file(page);
}

static inline unsigned long get_mm_rss(struct mm_struct *mm)
{
        return get_mm_counter(mm, MM_FILEPAGES) +
                get_mm_counter(mm, MM_ANONPAGES) +
                get_mm_counter(mm, MM_SHMEMPAGES);
}

static inline unsigned long get_mm_hiwater_rss(struct mm_struct *mm)
{
        return max(mm->hiwater_rss, get_mm_rss(mm));
}

static inline unsigned long get_mm_hiwater_vm(struct mm_struct *mm)
{
        return max(mm->hiwater_vm, mm->total_vm);
}

static inline void update_hiwater_rss(struct mm_struct *mm)
{
        unsigned long _rss = get_mm_rss(mm);

        if ((mm)->hiwater_rss < _rss)
                (mm)->hiwater_rss = _rss;
}

static inline void update_hiwater_vm(struct mm_struct *mm)
{
        if (mm->hiwater_vm < mm->total_vm)
                mm->hiwater_vm = mm->total_vm;
}

static inline void reset_mm_hiwater_rss(struct mm_struct *mm)
{
        mm->hiwater_rss = get_mm_rss(mm);
}

static inline void setmax_mm_hiwater_rss(unsigned long *maxrss,
                                         struct mm_struct *mm)
{
        unsigned long hiwater_rss = get_mm_hiwater_rss(mm);

        if (*maxrss < hiwater_rss)
                *maxrss = hiwater_rss;
}

#if defined(SPLIT_RSS_COUNTING)
void sync_mm_rss(struct mm_struct *mm);
#else
static inline void sync_mm_rss(struct mm_struct *mm)
{
}
#endif

#ifndef CONFIG_ARCH_HAS_PTE_SPECIAL
static inline int pte_special(pte_t pte)
{
        return 0;
}

static inline pte_t pte_mkspecial(pte_t pte)
{
        return pte;
}
#endif

#ifndef CONFIG_ARCH_HAS_PTE_DEVMAP
static inline int pte_devmap(pte_t pte)
{
        return 0;
}
#endif

int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot);

extern pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr,
                               spinlock_t **ptl);
static inline pte_t *get_locked_pte(struct mm_struct *mm, unsigned long addr,
                                    spinlock_t **ptl)
{
        pte_t *ptep;
        __cond_lock(*ptl, ptep = __get_locked_pte(mm, addr, ptl));
        return ptep;
}

#ifdef __PAGETABLE_P4D_FOLDED
static inline int __p4d_alloc(struct mm_struct *mm, pgd_t *pgd,
                                                unsigned long address)
{
        return 0;
}
#else
int __p4d_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address);
#endif

#if defined(__PAGETABLE_PUD_FOLDED) || !defined(CONFIG_MMU)
static inline int __pud_alloc(struct mm_struct *mm, p4d_t *p4d,
                                                unsigned long address)
{
        return 0;
}
static inline void mm_inc_nr_puds(struct mm_struct *mm) {}
static inline void mm_dec_nr_puds(struct mm_struct *mm) {}

#else
int __pud_alloc(struct mm_struct *mm, p4d_t *p4d, unsigned long address);

static inline void mm_inc_nr_puds(struct mm_struct *mm)
{
        if (mm_pud_folded(mm))
                return;
        atomic_long_add(PTRS_PER_PUD * sizeof(pud_t), &mm->pgtables_bytes);
}

static inline void mm_dec_nr_puds(struct mm_struct *mm)
{
        if (mm_pud_folded(mm))
                return;
        atomic_long_sub(PTRS_PER_PUD * sizeof(pud_t), &mm->pgtables_bytes);
}
#endif

#if defined(__PAGETABLE_PMD_FOLDED) || !defined(CONFIG_MMU)
static inline int __pmd_alloc(struct mm_struct *mm, pud_t *pud,
                                                unsigned long address)
{
        return 0;
}

static inline void mm_inc_nr_pmds(struct mm_struct *mm) {}
static inline void mm_dec_nr_pmds(struct mm_struct *mm) {}

#else
int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address);

static inline void mm_inc_nr_pmds(struct mm_struct *mm)
{
        if (mm_pmd_folded(mm))
                return;
        atomic_long_add(PTRS_PER_PMD * sizeof(pmd_t), &mm->pgtables_bytes);
}

static inline void mm_dec_nr_pmds(struct mm_struct *mm)
{
        if (mm_pmd_folded(mm))
                return;
        atomic_long_sub(PTRS_PER_PMD * sizeof(pmd_t), &mm->pgtables_bytes);
}
#endif

#ifdef CONFIG_MMU
static inline void mm_pgtables_bytes_init(struct mm_struct *mm)
{
        atomic_long_set(&mm->pgtables_bytes, 0);
}

static inline unsigned long mm_pgtables_bytes(const struct mm_struct *mm)
{
        return atomic_long_read(&mm->pgtables_bytes);
}

static inline void mm_inc_nr_ptes(struct mm_struct *mm)
{
        atomic_long_add(PTRS_PER_PTE * sizeof(pte_t), &mm->pgtables_bytes);
}

static inline void mm_dec_nr_ptes(struct mm_struct *mm)
{
        atomic_long_sub(PTRS_PER_PTE * sizeof(pte_t), &mm->pgtables_bytes);
}
#else

static inline void mm_pgtables_bytes_init(struct mm_struct *mm) {}
static inline unsigned long mm_pgtables_bytes(const struct mm_struct *mm)
{
        return 0;
}

static inline void mm_inc_nr_ptes(struct mm_struct *mm) {}
static inline void mm_dec_nr_ptes(struct mm_struct *mm) {}
#endif

int __pte_alloc(struct mm_struct *mm, pmd_t *pmd);
int __pte_alloc_kernel(pmd_t *pmd);

#if defined(CONFIG_MMU)

static inline p4d_t *p4d_alloc(struct mm_struct *mm, pgd_t *pgd,
                unsigned long address)
{
        return (unlikely(pgd_none(*pgd)) && __p4d_alloc(mm, pgd, address)) ?
                NULL : p4d_offset(pgd, address);
}

static inline pud_t *pud_alloc(struct mm_struct *mm, p4d_t *p4d,
                unsigned long address)
{
        return (unlikely(p4d_none(*p4d)) && __pud_alloc(mm, p4d, address)) ?
                NULL : pud_offset(p4d, address);
}

static inline pmd_t *pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address)
{
        return (unlikely(pud_none(*pud)) && __pmd_alloc(mm, pud, address))?
                NULL: pmd_offset(pud, address);
}
#endif /* CONFIG_MMU */

#if USE_SPLIT_PTE_PTLOCKS
#if ALLOC_SPLIT_PTLOCKS
void __init ptlock_cache_init(void);
extern bool ptlock_alloc(struct page *page);
extern void ptlock_free(struct page *page);

static inline spinlock_t *ptlock_ptr(struct page *page)
{
        return page->ptl;
}
#else /* ALLOC_SPLIT_PTLOCKS */
static inline void ptlock_cache_init(void)
{
}

static inline bool ptlock_alloc(struct page *page)
{
        return true;
}

static inline void ptlock_free(struct page *page)
{
}

static inline spinlock_t *ptlock_ptr(struct page *page)
{
        return &page->ptl;
}
#endif /* ALLOC_SPLIT_PTLOCKS */

static inline spinlock_t *pte_lockptr(struct mm_struct *mm, pmd_t *pmd)
{
        return ptlock_ptr(pmd_page(*pmd));
}

static inline bool ptlock_init(struct page *page)
{
        /*
         * prep_new_page() initialize page->private (and therefore page->ptl)
         * with 0. Make sure nobody took it in use in between.
         *
         * It can happen if arch try to use slab for page table allocation:
         * slab code uses page->slab_cache, which share storage with page->ptl.
         */
        VM_BUG_ON_PAGE(*(unsigned long *)&page->ptl, page);
        if (!ptlock_alloc(page))
                return false;
        spin_lock_init(ptlock_ptr(page));
        return true;
}

#else   /* !USE_SPLIT_PTE_PTLOCKS */
/*
 * We use mm->page_table_lock to guard all pagetable pages of the mm.
 */
static inline spinlock_t *pte_lockptr(struct mm_struct *mm, pmd_t *pmd)
{
        return &mm->page_table_lock;
}
static inline void ptlock_cache_init(void) {}
static inline bool ptlock_init(struct page *page) { return true; }
static inline void ptlock_free(struct page *page) {}
#endif /* USE_SPLIT_PTE_PTLOCKS */

static inline void pgtable_init(void)
{
        ptlock_cache_init();
        pgtable_cache_init();
}

static inline bool pgtable_pte_page_ctor(struct page *page)
{
        if (!ptlock_init(page))
                return false;
        __SetPageTable(page);
        inc_lruvec_page_state(page, NR_PAGETABLE);
        return true;
}

static inline void pgtable_pte_page_dtor(struct page *page)
{
        ptlock_free(page);
        __ClearPageTable(page);
        dec_lruvec_page_state(page, NR_PAGETABLE);
}

#define pte_offset_map_lock(mm, pmd, address, ptlp)     \
({                                                      \
        spinlock_t *__ptl = pte_lockptr(mm, pmd);       \
        pte_t *__pte = pte_offset_map(pmd, address);    \
        *(ptlp) = __ptl;                                \
        spin_lock(__ptl);                               \
        __pte;                                          \
})

#define pte_unmap_unlock(pte, ptl)      do {            \
        spin_unlock(ptl);                               \
        pte_unmap(pte);                                 \
} while (0)

#define pte_alloc(mm, pmd) (unlikely(pmd_none(*(pmd))) && __pte_alloc(mm, pmd))

#define pte_alloc_map(mm, pmd, address)                 \
        (pte_alloc(mm, pmd) ? NULL : pte_offset_map(pmd, address))

#define pte_alloc_map_lock(mm, pmd, address, ptlp)      \
        (pte_alloc(mm, pmd) ?                   \
                 NULL : pte_offset_map_lock(mm, pmd, address, ptlp))

#define pte_alloc_kernel(pmd, address)                  \
        ((unlikely(pmd_none(*(pmd))) && __pte_alloc_kernel(pmd))? \
                NULL: pte_offset_kernel(pmd, address))

#if USE_SPLIT_PMD_PTLOCKS

static struct page *pmd_to_page(pmd_t *pmd)
{
        unsigned long mask = ~(PTRS_PER_PMD * sizeof(pmd_t) - 1);
        return virt_to_page((void *)((unsigned long) pmd & mask));
}

static inline spinlock_t *pmd_lockptr(struct mm_struct *mm, pmd_t *pmd)
{
        return ptlock_ptr(pmd_to_page(pmd));
}

static inline bool pmd_ptlock_init(struct page *page)
{
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
        page->pmd_huge_pte = NULL;
#endif
        return ptlock_init(page);
}

static inline void pmd_ptlock_free(struct page *page)
{
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
        VM_BUG_ON_PAGE(page->pmd_huge_pte, page);
#endif
        ptlock_free(page);
}

#define pmd_huge_pte(mm, pmd) (pmd_to_page(pmd)->pmd_huge_pte)

#else

static inline spinlock_t *pmd_lockptr(struct mm_struct *mm, pmd_t *pmd)
{
        return &mm->page_table_lock;
}

static inline bool pmd_ptlock_init(struct page *page) { return true; }
static inline void pmd_ptlock_free(struct page *page) {}

#define pmd_huge_pte(mm, pmd) ((mm)->pmd_huge_pte)

#endif

static inline spinlock_t *pmd_lock(struct mm_struct *mm, pmd_t *pmd)
{
        spinlock_t *ptl = pmd_lockptr(mm, pmd);
        spin_lock(ptl);
        return ptl;
}

static inline bool pgtable_pmd_page_ctor(struct page *page)
{
        if (!pmd_ptlock_init(page))
                return false;
        __SetPageTable(page);
        inc_lruvec_page_state(page, NR_PAGETABLE);
        return true;
}

static inline void pgtable_pmd_page_dtor(struct page *page)
{
        pmd_ptlock_free(page);
        __ClearPageTable(page);
        dec_lruvec_page_state(page, NR_PAGETABLE);
}

/*
 * No scalability reason to split PUD locks yet, but follow the same pattern
 * as the PMD locks to make it easier if we decide to.  The VM should not be
 * considered ready to switch to split PUD locks yet; there may be places
 * which need to be converted from page_table_lock.
 */
static inline spinlock_t *pud_lockptr(struct mm_struct *mm, pud_t *pud)
{
        return &mm->page_table_lock;
}

static inline spinlock_t *pud_lock(struct mm_struct *mm, pud_t *pud)
{
        spinlock_t *ptl = pud_lockptr(mm, pud);

        spin_lock(ptl);
        return ptl;
}

extern void __init pagecache_init(void);
extern void __init free_area_init_memoryless_node(int nid);
extern void free_initmem(void);

/*
 * Free reserved pages within range [PAGE_ALIGN(start), end & PAGE_MASK)
 * into the buddy system. The freed pages will be poisoned with pattern
 * "poison" if it's within range [0, UCHAR_MAX].
 * Return pages freed into the buddy system.
 */
extern unsigned long free_reserved_area(void *start, void *end,
                                        int poison, const char *s);

#ifdef  CONFIG_HIGHMEM
/*
 * Free a highmem page into the buddy system, adjusting totalhigh_pages
 * and totalram_pages.
 */
extern void free_highmem_page(struct page *page);
#endif

extern void adjust_managed_page_count(struct page *page, long count);
extern void mem_init_print_info(const char *str);

extern void reserve_bootmem_region(phys_addr_t start, phys_addr_t end);

/* Free the reserved page into the buddy system, so it gets managed. */
static inline void __free_reserved_page(struct page *page)
{
        ClearPageReserved(page);
        init_page_count(page);
        __free_page(page);
}

static inline void free_reserved_page(struct page *page)
{
        __free_reserved_page(page);
        adjust_managed_page_count(page, 1);
}

static inline void mark_page_reserved(struct page *page)
{
        SetPageReserved(page);
        adjust_managed_page_count(page, -1);
}

/*
 * Default method to free all the __init memory into the buddy system.
 * The freed pages will be poisoned with pattern "poison" if it's within
 * range [0, UCHAR_MAX].
 * Return pages freed into the buddy system.
 */
static inline unsigned long free_initmem_default(int poison)
{
        extern char __init_begin[], __init_end[];

        return free_reserved_area(&__init_begin, &__init_end,
                                  poison, "unused kernel");
}

static inline unsigned long get_num_physpages(void)
{
        int nid;
        unsigned long phys_pages = 0;

        for_each_online_node(nid)
                phys_pages += node_present_pages(nid);

        return phys_pages;
}

/*
 * Using memblock node mappings, an architecture may initialise its
 * zones, allocate the backing mem_map and account for memory holes in an
 * architecture independent manner.
 *
 * An architecture is expected to register range of page frames backed by
 * physical memory with memblock_add[_node]() before calling
 * free_area_init() passing in the PFN each zone ends at. At a basic
 * usage, an architecture is expected to do something like
 *
 * unsigned long max_zone_pfns[MAX_NR_ZONES] = {max_dma, max_normal_pfn,
 *                                                       max_highmem_pfn};
 * for_each_valid_physical_page_range()
 *      memblock_add_node(base, size, nid)
 * free_area_init(max_zone_pfns);
 */
void free_area_init(unsigned long *max_zone_pfn);
unsigned long node_map_pfn_alignment(void);
unsigned long __absent_pages_in_range(int nid, unsigned long start_pfn,
                                                unsigned long end_pfn);
extern unsigned long absent_pages_in_range(unsigned long start_pfn,
                                                unsigned long end_pfn);
extern void get_pfn_range_for_nid(unsigned int nid,
                        unsigned long *start_pfn, unsigned long *end_pfn);
extern unsigned long find_min_pfn_with_active_regions(void);

#ifndef CONFIG_NEED_MULTIPLE_NODES
static inline int early_pfn_to_nid(unsigned long pfn)
{
        return 0;
}
#else
/* please see mm/page_alloc.c */
extern int __meminit early_pfn_to_nid(unsigned long pfn);
#endif

extern void set_dma_reserve(unsigned long new_dma_reserve);
extern void memmap_init_zone(unsigned long, int, unsigned long,
                unsigned long, unsigned long, enum meminit_context,
                struct vmem_altmap *, int migratetype);
extern void setup_per_zone_wmarks(void);
extern int __meminit init_per_zone_wmark_min(void);
extern void mem_init(void);
extern void __init mmap_init(void);
extern void show_mem(unsigned int flags, nodemask_t *nodemask);
extern long si_mem_available(void);
extern void si_meminfo(struct sysinfo * val);
extern void si_meminfo_node(struct sysinfo *val, int nid);
#ifdef __HAVE_ARCH_RESERVED_KERNEL_PAGES
extern unsigned long arch_reserved_kernel_pages(void);
#endif

extern __printf(3, 4)
void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...);

extern void setup_per_cpu_pageset(void);

/* page_alloc.c */
extern int min_free_kbytes;
extern int watermark_boost_factor;
extern int watermark_scale_factor;
extern bool arch_has_descending_max_zone_pfns(void);

/* nommu.c */
extern atomic_long_t mmap_pages_allocated;
extern int nommu_shrink_inode_mappings(struct inode *, size_t, size_t);

/* interval_tree.c */
void vma_interval_tree_insert(struct vm_area_struct *node,
                              struct rb_root_cached *root);
void vma_interval_tree_insert_after(struct vm_area_struct *node,
                                    struct vm_area_struct *prev,
                                    struct rb_root_cached *root);
void vma_interval_tree_remove(struct vm_area_struct *node,
                              struct rb_root_cached *root);
struct vm_area_struct *vma_interval_tree_iter_first(struct rb_root_cached *root,
                                unsigned long start, unsigned long last);
struct vm_area_struct *vma_interval_tree_iter_next(struct vm_area_struct *node,
                                unsigned long start, unsigned long last);

#define vma_interval_tree_foreach(vma, root, start, last)               \
        for (vma = vma_interval_tree_iter_first(root, start, last);     \
             vma; vma = vma_interval_tree_iter_next(vma, start, last))

void anon_vma_interval_tree_insert(struct anon_vma_chain *node,
                                   struct rb_root_cached *root);
void anon_vma_interval_tree_remove(struct anon_vma_chain *node,
                                   struct rb_root_cached *root);
struct anon_vma_chain *
anon_vma_interval_tree_iter_first(struct rb_root_cached *root,
                                  unsigned long start, unsigned long last);
struct anon_vma_chain *anon_vma_interval_tree_iter_next(
        struct anon_vma_chain *node, unsigned long start, unsigned long last);
#ifdef CONFIG_DEBUG_VM_RB
void anon_vma_interval_tree_verify(struct anon_vma_chain *node);
#endif

#define anon_vma_interval_tree_foreach(avc, root, start, last)           \
        for (avc = anon_vma_interval_tree_iter_first(root, start, last); \
             avc; avc = anon_vma_interval_tree_iter_next(avc, start, last))

/* mmap.c */
extern int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin);
extern int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
        unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert,
        struct vm_area_struct *expand);
static inline int vma_adjust(struct vm_area_struct *vma, unsigned long start,
        unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert)
{
        return __vma_adjust(vma, start, end, pgoff, insert, NULL);
}
extern struct vm_area_struct *vma_merge(struct mm_struct *,
        struct vm_area_struct *prev, unsigned long addr, unsigned long end,
        unsigned long vm_flags, struct anon_vma *, struct file *, pgoff_t,
        struct mempolicy *, struct vm_userfaultfd_ctx);
extern struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *);
extern int __split_vma(struct mm_struct *, struct vm_area_struct *,
        unsigned long addr, int new_below);
extern int split_vma(struct mm_struct *, struct vm_area_struct *,
        unsigned long addr, int new_below);
extern int insert_vm_struct(struct mm_struct *, struct vm_area_struct *);
extern void __vma_link_rb(struct mm_struct *, struct vm_area_struct *,
        struct rb_node **, struct rb_node *);
extern void unlink_file_vma(struct vm_area_struct *);
extern struct vm_area_struct *copy_vma(struct vm_area_struct **,
        unsigned long addr, unsigned long len, pgoff_t pgoff,
        bool *need_rmap_locks);
extern void exit_mmap(struct mm_struct *);

static inline int check_data_rlimit(unsigned long rlim,
                                    unsigned long new,
                                    unsigned long start,
                                    unsigned long end_data,
                                    unsigned long start_data)
{
        if (rlim < RLIM_INFINITY) {
                if (((new - start) + (end_data - start_data)) > rlim)
                        return -ENOSPC;
        }

        return 0;
}

extern int mm_take_all_locks(struct mm_struct *mm);
extern void mm_drop_all_locks(struct mm_struct *mm);

extern void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file);
extern struct file *get_mm_exe_file(struct mm_struct *mm);
extern struct file *get_task_exe_file(struct task_struct *task);

extern bool may_expand_vm(struct mm_struct *, vm_flags_t, unsigned long npages);
extern void vm_stat_account(struct mm_struct *, vm_flags_t, long npages);

extern bool vma_is_special_mapping(const struct vm_area_struct *vma,
                                   const struct vm_special_mapping *sm);
extern struct vm_area_struct *_install_special_mapping(struct mm_struct *mm,
                                   unsigned long addr, unsigned long len,
                                   unsigned long flags,
                                   const struct vm_special_mapping *spec);
/* This is an obsolete alternative to _install_special_mapping. */
extern int install_special_mapping(struct mm_struct *mm,
                                   unsigned long addr, unsigned long len,
                                   unsigned long flags, struct page **pages);

unsigned long randomize_stack_top(unsigned long stack_top);

extern unsigned long get_unmapped_area(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);

extern unsigned long mmap_region(struct file *file, unsigned long addr,
        unsigned long len, vm_flags_t vm_flags, unsigned long pgoff,
        struct list_head *uf);
extern unsigned long do_mmap(struct file *file, unsigned long addr,
        unsigned long len, unsigned long prot, unsigned long flags,
        unsigned long pgoff, unsigned long *populate, struct list_head *uf);
extern int __do_munmap(struct mm_struct *, unsigned long, size_t,
                       struct list_head *uf, bool downgrade);
extern int do_munmap(struct mm_struct *, unsigned long, size_t,
                     struct list_head *uf);
extern int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int behavior);

#ifdef CONFIG_MMU
extern int __mm_populate(unsigned long addr, unsigned long len,
                         int ignore_errors);
static inline void mm_populate(unsigned long addr, unsigned long len)
{
        /* Ignore errors */
        (void) __mm_populate(addr, len, 1);
}
#else
static inline void mm_populate(unsigned long addr, unsigned long len) {}
#endif

/* These take the mm semaphore themselves */
extern int __must_check vm_brk(unsigned long, unsigned long);
extern int __must_check vm_brk_flags(unsigned long, unsigned long, unsigned long);
extern int vm_munmap(unsigned long, size_t);
extern unsigned long __must_check vm_mmap(struct file *, unsigned long,
        unsigned long, unsigned long,
        unsigned long, unsigned long);

struct vm_unmapped_area_info {
#define VM_UNMAPPED_AREA_TOPDOWN 1
        unsigned long flags;
        unsigned long length;
        unsigned long low_limit;
        unsigned long high_limit;
        unsigned long align_mask;
        unsigned long align_offset;
};

extern unsigned long vm_unmapped_area(struct vm_unmapped_area_info *info);

/* truncate.c */
extern void truncate_inode_pages(struct address_space *, loff_t);
extern void truncate_inode_pages_range(struct address_space *,
                                       loff_t lstart, loff_t lend);
extern void truncate_inode_pages_final(struct address_space *);

/* generic vm_area_ops exported for stackable file systems */
extern vm_fault_t filemap_fault(struct vm_fault *vmf);
extern void filemap_map_pages(struct vm_fault *vmf,
                pgoff_t start_pgoff, pgoff_t end_pgoff);
extern vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf);

/* mm/page-writeback.c */
int __must_check write_one_page(struct page *page);
void task_dirty_inc(struct task_struct *tsk);

extern unsigned long stack_guard_gap;
/* Generic expand stack which grows the stack according to GROWS{UP,DOWN} */
extern int expand_stack(struct vm_area_struct *vma, unsigned long address);

/* CONFIG_STACK_GROWSUP still needs to grow downwards at some places */
extern int expand_downwards(struct vm_area_struct *vma,
                unsigned long address);
#if VM_GROWSUP
extern int expand_upwards(struct vm_area_struct *vma, unsigned long address);
#else
  #define expand_upwards(vma, address) (0)
#endif

/* Look up the first VMA which satisfies  addr < vm_end,  NULL if none. */
extern struct vm_area_struct * find_vma(struct mm_struct * mm, unsigned long addr);
extern struct vm_area_struct * find_vma_prev(struct mm_struct * mm, unsigned long addr,
                                             struct vm_area_struct **pprev);

/* Look up the first VMA which intersects the interval start_addr..end_addr-1,
   NULL if none.  Assume start_addr < end_addr. */
static inline struct vm_area_struct * find_vma_intersection(struct mm_struct * mm, unsigned long start_addr, unsigned long end_addr)
{
        struct vm_area_struct * vma = find_vma(mm,start_addr);

        if (vma && end_addr <= vma->vm_start)
                vma = NULL;
        return vma;
}

static inline unsigned long vm_start_gap(struct vm_area_struct *vma)
{
        unsigned long vm_start = vma->vm_start;

        if (vma->vm_flags & VM_GROWSDOWN) {
                vm_start -= stack_guard_gap;
                if (vm_start > vma->vm_start)
                        vm_start = 0;
        }
        return vm_start;
}

static inline unsigned long vm_end_gap(struct vm_area_struct *vma)
{
        unsigned long vm_end = vma->vm_end;

        if (vma->vm_flags & VM_GROWSUP) {
                vm_end += stack_guard_gap;
                if (vm_end < vma->vm_end)
                        vm_end = -PAGE_SIZE;
        }
        return vm_end;
}

static inline unsigned long vma_pages(struct vm_area_struct *vma)
{
        return (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
}

/* Look up the first VMA which exactly match the interval vm_start ... vm_end */
static inline struct vm_area_struct *find_exact_vma(struct mm_struct *mm,
                                unsigned long vm_start, unsigned long vm_end)
{
        struct vm_area_struct *vma = find_vma(mm, vm_start);

        if (vma && (vma->vm_start != vm_start || vma->vm_end != vm_end))
                vma = NULL;

        return vma;
}

static inline bool range_in_vma(struct vm_area_struct *vma,
                                unsigned long start, unsigned long end)
{
        return (vma && vma->vm_start <= start && end <= vma->vm_end);
}

#ifdef CONFIG_MMU
pgprot_t vm_get_page_prot(unsigned long vm_flags);
void vma_set_page_prot(struct vm_area_struct *vma);
#else
static inline pgprot_t vm_get_page_prot(unsigned long vm_flags)
{
        return __pgprot(0);
}
static inline void vma_set_page_prot(struct vm_area_struct *vma)
{
        vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
}
#endif

void vma_set_file(struct vm_area_struct *vma, struct file *file);

#ifdef CONFIG_NUMA_BALANCING
unsigned long change_prot_numa(struct vm_area_struct *vma,
                        unsigned long start, unsigned long end);
#endif

struct vm_area_struct *find_extend_vma(struct mm_struct *, unsigned long addr);
int remap_pfn_range(struct vm_area_struct *, unsigned long addr,
                        unsigned long pfn, unsigned long size, pgprot_t);
int vm_insert_page(struct vm_area_struct *, unsigned long addr, struct page *);
int vm_insert_pages(struct vm_area_struct *vma, unsigned long addr,
                        struct page **pages, unsigned long *num);
int vm_map_pages(struct vm_area_struct *vma, struct page **pages,
                                unsigned long num);
int vm_map_pages_zero(struct vm_area_struct *vma, struct page **pages,
                                unsigned long num);
vm_fault_t vmf_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
                        unsigned long pfn);
vm_fault_t vmf_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
                        unsigned long pfn, pgprot_t pgprot);
vm_fault_t vmf_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
                        pfn_t pfn);
vm_fault_t vmf_insert_mixed_prot(struct vm_area_struct *vma, unsigned long addr,
                        pfn_t pfn, pgprot_t pgprot);
vm_fault_t vmf_insert_mixed_mkwrite(struct vm_area_struct *vma,
                unsigned long addr, pfn_t pfn);
int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len);

static inline vm_fault_t vmf_insert_page(struct vm_area_struct *vma,
                                unsigned long addr, struct page *page)
{
        int err = vm_insert_page(vma, addr, page);

        if (err == -ENOMEM)
                return VM_FAULT_OOM;
        if (err < 0 && err != -EBUSY)
                return VM_FAULT_SIGBUS;

        return VM_FAULT_NOPAGE;
}

#ifndef io_remap_pfn_range
static inline int io_remap_pfn_range(struct vm_area_struct *vma,
                                     unsigned long addr, unsigned long pfn,
                                     unsigned long size, pgprot_t prot)
{
        return remap_pfn_range(vma, addr, pfn, size, pgprot_decrypted(prot));
}
#endif

static inline vm_fault_t vmf_error(int err)
{
        if (err == -ENOMEM)
                return VM_FAULT_OOM;
        return VM_FAULT_SIGBUS;
}

struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
                         unsigned int foll_flags);

#define FOLL_WRITE      0x01    /* check pte is writable */
#define FOLL_TOUCH      0x02    /* mark page accessed */
#define FOLL_GET        0x04    /* do get_page on page */
#define FOLL_DUMP       0x08    /* give error on hole if it would be zero */
#define FOLL_FORCE      0x10    /* get_user_pages read/write w/o permission */
#define FOLL_NOWAIT     0x20    /* if a disk transfer is needed, start the IO
                                 * and return without waiting upon it */
#define FOLL_POPULATE   0x40    /* fault in page */
#define FOLL_SPLIT      0x80    /* don't return transhuge pages, split them */
#define FOLL_HWPOISON   0x100   /* check page is hwpoisoned */
#define FOLL_NUMA       0x200   /* force NUMA hinting page fault */
#define FOLL_MIGRATION  0x400   /* wait for page to replace migration entry */
#define FOLL_TRIED      0x800   /* a retry, previous pass started an IO */
#define FOLL_MLOCK      0x1000  /* lock present pages */
#define FOLL_REMOTE     0x2000  /* we are working on non-current tsk/mm */
#define FOLL_COW        0x4000  /* internal GUP flag */
#define FOLL_ANON       0x8000  /* don't do file mappings */
#define FOLL_LONGTERM   0x10000 /* mapping lifetime is indefinite: see below */
#define FOLL_SPLIT_PMD  0x20000 /* split huge pmd before returning */
#define FOLL_PIN        0x40000 /* pages must be released via unpin_user_page */
#define FOLL_FAST_ONLY  0x80000 /* gup_fast: prevent fall-back to slow gup */

/*
 * FOLL_PIN and FOLL_LONGTERM may be used in various combinations with each
 * other. Here is what they mean, and how to use them:
 *
 * FOLL_LONGTERM indicates that the page will be held for an indefinite time
 * period _often_ under userspace control.  This is in contrast to
 * iov_iter_get_pages(), whose usages are transient.
 *
 * FIXME: For pages which are part of a filesystem, mappings are subject to the
 * lifetime enforced by the filesystem and we need guarantees that longterm
 * users like RDMA and V4L2 only establish mappings which coordinate usage with
 * the filesystem.  Ideas for this coordination include revoking the longterm
 * pin, delaying writeback, bounce buffer page writeback, etc.  As FS DAX was
 * added after the problem with filesystems was found FS DAX VMAs are
 * specifically failed.  Filesystem pages are still subject to bugs and use of
 * FOLL_LONGTERM should be avoided on those pages.
 *
 * FIXME: Also NOTE that FOLL_LONGTERM is not supported in every GUP call.
 * Currently only get_user_pages() and get_user_pages_fast() support this flag
 * and calls to get_user_pages_[un]locked are specifically not allowed.  This
 * is due to an incompatibility with the FS DAX check and
 * FAULT_FLAG_ALLOW_RETRY.
 *
 * In the CMA case: long term pins in a CMA region would unnecessarily fragment
 * that region.  And so, CMA attempts to migrate the page before pinning, when
 * FOLL_LONGTERM is specified.
 *
 * FOLL_PIN indicates that a special kind of tracking (not just page->_refcount,
 * but an additional pin counting system) will be invoked. This is intended for
 * anything that gets a page reference and then touches page data (for example,
 * Direct IO). This lets the filesystem know that some non-file-system entity is
 * potentially changing the pages' data. In contrast to FOLL_GET (whose pages
 * are released via put_page()), FOLL_PIN pages must be released, ultimately, by
 * a call to unpin_user_page().
 *
 * FOLL_PIN is similar to FOLL_GET: both of these pin pages. They use different
 * and separate refcounting mechanisms, however, and that means that each has
 * its own acquire and release mechanisms:
 *
 *     FOLL_GET: get_user_pages*() to acquire, and put_page() to release.
 *
 *     FOLL_PIN: pin_user_pages*() to acquire, and unpin_user_pages to release.
 *
 * FOLL_PIN and FOLL_GET are mutually exclusive for a given function call.
 * (The underlying pages may experience both FOLL_GET-based and FOLL_PIN-based
 * calls applied to them, and that's perfectly OK. This is a constraint on the
 * callers, not on the pages.)
 *
 * FOLL_PIN should be set internally by the pin_user_pages*() APIs, never
 * directly by the caller. That's in order to help avoid mismatches when
 * releasing pages: get_user_pages*() pages must be released via put_page(),
 * while pin_user_pages*() pages must be released via unpin_user_page().
 *
 * Please see Documentation/core-api/pin_user_pages.rst for more information.
 */

static inline int vm_fault_to_errno(vm_fault_t vm_fault, int foll_flags)
{
        if (vm_fault & VM_FAULT_OOM)
                return -ENOMEM;
        if (vm_fault & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
                return (foll_flags & FOLL_HWPOISON) ? -EHWPOISON : -EFAULT;
        if (vm_fault & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV))
                return -EFAULT;
        return 0;
}

typedef int (*pte_fn_t)(pte_t *pte, unsigned long addr, void *data);
extern int apply_to_page_range(struct mm_struct *mm, unsigned long address,
                               unsigned long size, pte_fn_t fn, void *data);
extern int apply_to_existing_page_range(struct mm_struct *mm,
                                   unsigned long address, unsigned long size,
                                   pte_fn_t fn, void *data);

extern void init_mem_debugging_and_hardening(void);
#ifdef CONFIG_PAGE_POISONING
extern void __kernel_poison_pages(struct page *page, int numpages);
extern void __kernel_unpoison_pages(struct page *page, int numpages);
extern bool _page_poisoning_enabled_early;
DECLARE_STATIC_KEY_FALSE(_page_poisoning_enabled);
static inline bool page_poisoning_enabled(void)
{
        return _page_poisoning_enabled_early;
}
/*
 * For use in fast paths after init_mem_debugging() has run, or when a
 * false negative result is not harmful when called too early.
 */
static inline bool page_poisoning_enabled_static(void)
{
        return static_branch_unlikely(&_page_poisoning_enabled);
}
static inline void kernel_poison_pages(struct page *page, int numpages)
{
        if (page_poisoning_enabled_static())
                __kernel_poison_pages(page, numpages);
}
static inline void kernel_unpoison_pages(struct page *page, int numpages)
{
        if (page_poisoning_enabled_static())
                __kernel_unpoison_pages(page, numpages);
}
#else
static inline bool page_poisoning_enabled(void) { return false; }
static inline bool page_poisoning_enabled_static(void) { return false; }
static inline void __kernel_poison_pages(struct page *page, int nunmpages) { }
static inline void kernel_poison_pages(struct page *page, int numpages) { }
static inline void kernel_unpoison_pages(struct page *page, int numpages) { }
#endif

DECLARE_STATIC_KEY_FALSE(init_on_alloc);
static inline bool want_init_on_alloc(gfp_t flags)
{
        if (static_branch_unlikely(&init_on_alloc))
                return true;
        return flags & __GFP_ZERO;
}

DECLARE_STATIC_KEY_FALSE(init_on_free);
static inline bool want_init_on_free(void)
{
        return static_branch_unlikely(&init_on_free);
}

extern bool _debug_pagealloc_enabled_early;
DECLARE_STATIC_KEY_FALSE(_debug_pagealloc_enabled);

static inline bool debug_pagealloc_enabled(void)
{
        return IS_ENABLED(CONFIG_DEBUG_PAGEALLOC) &&
                _debug_pagealloc_enabled_early;
}

/*
 * For use in fast paths after init_debug_pagealloc() has run, or when a
 * false negative result is not harmful when called too early.
 */
static inline bool debug_pagealloc_enabled_static(void)
{
        if (!IS_ENABLED(CONFIG_DEBUG_PAGEALLOC))
                return false;

        return static_branch_unlikely(&_debug_pagealloc_enabled);
}

#ifdef CONFIG_DEBUG_PAGEALLOC
/*
 * To support DEBUG_PAGEALLOC architecture must ensure that
 * __kernel_map_pages() never fails
 */
extern void __kernel_map_pages(struct page *page, int numpages, int enable);

static inline void debug_pagealloc_map_pages(struct page *page, int numpages)
{
        if (debug_pagealloc_enabled_static())
                __kernel_map_pages(page, numpages, 1);
}

static inline void debug_pagealloc_unmap_pages(struct page *page, int numpages)
{
        if (debug_pagealloc_enabled_static())
                __kernel_map_pages(page, numpages, 0);
}
#else   /* CONFIG_DEBUG_PAGEALLOC */
static inline void debug_pagealloc_map_pages(struct page *page, int numpages) {}
static inline void debug_pagealloc_unmap_pages(struct page *page, int numpages) {}
#endif  /* CONFIG_DEBUG_PAGEALLOC */

#ifdef __HAVE_ARCH_GATE_AREA
extern struct vm_area_struct *get_gate_vma(struct mm_struct *mm);
extern int in_gate_area_no_mm(unsigned long addr);
extern int in_gate_area(struct mm_struct *mm, unsigned long addr);
#else
static inline struct vm_area_struct *get_gate_vma(struct mm_struct *mm)
{
        return NULL;
}
static inline int in_gate_area_no_mm(unsigned long addr) { return 0; }
static inline int in_gate_area(struct mm_struct *mm, unsigned long addr)
{
        return 0;
}
#endif  /* __HAVE_ARCH_GATE_AREA */

extern bool process_shares_mm(struct task_struct *p, struct mm_struct *mm);

#ifdef CONFIG_SYSCTL
extern int sysctl_drop_caches;
int drop_caches_sysctl_handler(struct ctl_table *, int, void *, size_t *,
                loff_t *);
#endif

void drop_slab(void);
void drop_slab_node(int nid);

#ifndef CONFIG_MMU
#define randomize_va_space 0
#else
extern int randomize_va_space;
#endif

const char * arch_vma_name(struct vm_area_struct *vma);
#ifdef CONFIG_MMU
void print_vma_addr(char *prefix, unsigned long rip);
#else
static inline void print_vma_addr(char *prefix, unsigned long rip)
{
}
#endif

void *sparse_buffer_alloc(unsigned long size);
struct page * __populate_section_memmap(unsigned long pfn,
                unsigned long nr_pages, int nid, struct vmem_altmap *altmap);
pgd_t *vmemmap_pgd_populate(unsigned long addr, int node);
p4d_t *vmemmap_p4d_populate(pgd_t *pgd, unsigned long addr, int node);
pud_t *vmemmap_pud_populate(p4d_t *p4d, unsigned long addr, int node);
pmd_t *vmemmap_pmd_populate(pud_t *pud, unsigned long addr, int node);
pte_t *vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, int node,
                            struct vmem_altmap *altmap);
void *vmemmap_alloc_block(unsigned long size, int node);
struct vmem_altmap;
void *vmemmap_alloc_block_buf(unsigned long size, int node,
                              struct vmem_altmap *altmap);
void vmemmap_verify(pte_t *, int, unsigned long, unsigned long);
int vmemmap_populate_basepages(unsigned long start, unsigned long end,
                               int node, struct vmem_altmap *altmap);
int vmemmap_populate(unsigned long start, unsigned long end, int node,
                struct vmem_altmap *altmap);
void vmemmap_populate_print_last(void);
#ifdef CONFIG_MEMORY_HOTPLUG
void vmemmap_free(unsigned long start, unsigned long end,
                struct vmem_altmap *altmap);
#endif
void register_page_bootmem_memmap(unsigned long section_nr, struct page *map,
                                  unsigned long nr_pages);

enum mf_flags {
        MF_COUNT_INCREASED = 1 << 0,
        MF_ACTION_REQUIRED = 1 << 1,
        MF_MUST_KILL = 1 << 2,
        MF_SOFT_OFFLINE = 1 << 3,
};
extern int memory_failure(unsigned long pfn, int flags);
extern void memory_failure_queue(unsigned long pfn, int flags);
extern void memory_failure_queue_kick(int cpu);
extern int unpoison_memory(unsigned long pfn);
extern int sysctl_memory_failure_early_kill;
extern int sysctl_memory_failure_recovery;
extern void shake_page(struct page *p, int access);
extern atomic_long_t num_poisoned_pages __read_mostly;
extern int soft_offline_page(unsigned long pfn, int flags);


/*
 * Error handlers for various types of pages.
 */
enum mf_result {
        MF_IGNORED,     /* Error: cannot be handled */
        MF_FAILED,      /* Error: handling failed */
        MF_DELAYED,     /* Will be handled later */
        MF_RECOVERED,   /* Successfully recovered */
};

enum mf_action_page_type {
        MF_MSG_KERNEL,
        MF_MSG_KERNEL_HIGH_ORDER,
        MF_MSG_SLAB,
        MF_MSG_DIFFERENT_COMPOUND,
        MF_MSG_POISONED_HUGE,
        MF_MSG_HUGE,
        MF_MSG_FREE_HUGE,
        MF_MSG_NON_PMD_HUGE,
        MF_MSG_UNMAP_FAILED,
        MF_MSG_DIRTY_SWAPCACHE,
        MF_MSG_CLEAN_SWAPCACHE,
        MF_MSG_DIRTY_MLOCKED_LRU,
        MF_MSG_CLEAN_MLOCKED_LRU,
        MF_MSG_DIRTY_UNEVICTABLE_LRU,
        MF_MSG_CLEAN_UNEVICTABLE_LRU,
        MF_MSG_DIRTY_LRU,
        MF_MSG_CLEAN_LRU,
        MF_MSG_TRUNCATED_LRU,
        MF_MSG_BUDDY,
        MF_MSG_BUDDY_2ND,
        MF_MSG_DAX,
        MF_MSG_UNSPLIT_THP,
        MF_MSG_UNKNOWN,
};

#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HUGETLBFS)
extern void clear_huge_page(struct page *page,
                            unsigned long addr_hint,
                            unsigned int pages_per_huge_page);
extern void copy_user_huge_page(struct page *dst, struct page *src,
                                unsigned long addr_hint,
                                struct vm_area_struct *vma,
                                unsigned int pages_per_huge_page);
extern long copy_huge_page_from_user(struct page *dst_page,
                                const void __user *usr_src,
                                unsigned int pages_per_huge_page,
                                bool allow_pagefault);

/**
 * vma_is_special_huge - Are transhuge page-table entries considered special?
 * @vma: Pointer to the struct vm_area_struct to consider
 *
 * Whether transhuge page-table entries are considered "special" following
 * the definition in vm_normal_page().
 *
 * Return: true if transhuge page-table entries should be considered special,
 * false otherwise.
 */
static inline bool vma_is_special_huge(const struct vm_area_struct *vma)
{
        return vma_is_dax(vma) || (vma->vm_file &&
                                   (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP)));
}

#endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */

#ifdef CONFIG_DEBUG_PAGEALLOC
extern unsigned int _debug_guardpage_minorder;
DECLARE_STATIC_KEY_FALSE(_debug_guardpage_enabled);

static inline unsigned int debug_guardpage_minorder(void)
{
        return _debug_guardpage_minorder;
}

static inline bool debug_guardpage_enabled(void)
{
        return static_branch_unlikely(&_debug_guardpage_enabled);
}

static inline bool page_is_guard(struct page *page)
{
        if (!debug_guardpage_enabled())
                return false;

        return PageGuard(page);
}
#else
static inline unsigned int debug_guardpage_minorder(void) { return 0; }
static inline bool debug_guardpage_enabled(void) { return false; }
static inline bool page_is_guard(struct page *page) { return false; }
#endif /* CONFIG_DEBUG_PAGEALLOC */

#if MAX_NUMNODES > 1
void __init setup_nr_node_ids(void);
#else
static inline void setup_nr_node_ids(void) {}
#endif

extern int memcmp_pages(struct page *page1, struct page *page2);

static inline int pages_identical(struct page *page1, struct page *page2)
{
        return !memcmp_pages(page1, page2);
}

#ifdef CONFIG_MAPPING_DIRTY_HELPERS
unsigned long clean_record_shared_mapping_range(struct address_space *mapping,
                                                pgoff_t first_index, pgoff_t nr,
                                                pgoff_t bitmap_pgoff,
                                                unsigned long *bitmap,
                                                pgoff_t *start,
                                                pgoff_t *end);

unsigned long wp_shared_mapping_range(struct address_space *mapping,
                                      pgoff_t first_index, pgoff_t nr);
#endif

extern int sysctl_nr_trim_pages;

#endif /* __KERNEL__ */
#endif /* _LINUX_MM_H */