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 /* SPDX-License-Identifier: GPL-2.0 */
 #ifndef _LINUX_MM_H
 #define _LINUX_MM_H
 
 #include <linux/errno.h>
 #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/overflow.h>
 #include <linux/sizes.h>
 #include <linux/sched.h>
 #include <linux/pgtable.h>
 #include <linux/kasan.h>
 #include <linux/memremap.h>
 
 struct mempolicy;
 struct anon_vma;
 struct anon_vma_chain;
 struct user_struct;
 struct pt_regs;
 
 extern int sysctl_page_lock_unfairness;
 
 void init_mm_internals(void);
 
 #ifndef CONFIG_NUMA     /* 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 architectures 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 statements 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 *);
 
 #if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
 #define nth_page(page,n) pfn_to_page(page_to_pfn((page)) + (n))
 #define folio_page_idx(folio, p)    (page_to_pfn(p) - folio_pfn(folio))
 #else
 #define nth_page(page,n) ((page) + (n))
 #define folio_page_idx(folio, p)    ((p) - &(folio)->page)
 #endif
 
 /* to align the pointer to the (next) page boundary */
 #define PAGE_ALIGN(addr) ALIGN(addr, PAGE_SIZE)
 
 /* to align the pointer to the (prev) page boundary */
 #define PAGE_ALIGN_DOWN(addr) ALIGN_DOWN(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))
 static inline struct folio *lru_to_folio(struct list_head *head)
 {
     return list_entry((head)->prev, struct folio, lru);
 }
 
 void setup_initial_init_mm(void *start_code, void *end_code,
                void *end_data, void *brk);
 
 /*
  * 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_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
 
 #ifdef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR
 # define VM_UFFD_MINOR_BIT  37
 # define VM_UFFD_MINOR      BIT(VM_UFFD_MINOR_BIT)  /* UFFD minor faults */
 #else /* !CONFIG_HAVE_ARCH_USERFAULTFD_MINOR */
 # define VM_UFFD_MINOR      VM_NONE
 #endif /* CONFIG_HAVE_ARCH_USERFAULTFD_MINOR */
 
 /* 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..
  */
 
 /*
  * 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
  * @flags: Fault flags.
  *
  * 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(enum fault_flag 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 {
     const struct {
         struct vm_area_struct *vma; /* Target VMA */
         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 - masked */
         unsigned long real_address; /* Faulting virtual address - unmasked */
     };
     enum fault_flag flags;      /* FAULT_FLAG_xxx flags
                      * XXX: should really be 'const' */
     pmd_t *pmd;         /* Pointer to pmd entry matching
                      * the 'address' */
     pud_t *pud;         /* Pointer to pud entry matching
                      * the 'address'
                      */
     union {
         pte_t orig_pte;     /* Value of PTE at the time of fault */
         pmd_t orig_pmd;     /* Value of PMD at the time of fault,
                      * used by PMD fault only.
                      */
     };
 
     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() sets up a page
                      * table 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);
     /**
      * @close: Called when the VMA is being removed from the MM.
      * Context: User context.  May sleep.  Caller holds mmap_lock.
      */
     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);
     /*
      * 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);
     vm_fault_t (*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. See also generic_access_phys() for a generic
      * implementation useful for any iomem mapping.
      */
     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;
 
 static inline unsigned int compound_order(struct page *page)
 {
     if (!PageHead(page))
         return 0;
     return page[1].compound_order;
 }
 
 /**
  * folio_order - The allocation order of a folio.
  * @folio: The folio.
  *
  * A folio is composed of 2^order pages.  See get_order() for the definition
  * of order.
  *
  * Return: The order of the folio.
  */
 static inline unsigned int folio_order(struct folio *folio)
 {
     return compound_order(&folio->page);
 }
 
 #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);
 }
 
 static inline int folio_put_testzero(struct folio *folio)
 {
     return put_page_testzero(&folio->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 bool 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
 
 /*
  * How many times the entire folio is mapped as a single unit (eg by a
  * PMD or PUD entry).  This is probably not what you want, except for
  * debugging purposes; look at folio_mapcount() or page_mapcount()
  * instead.
  */
 static inline int folio_entire_mapcount(struct folio *folio)
 {
     VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
     return atomic_read(folio_mapcount_ptr(folio)) + 1;
 }
 
 /*
  * Mapcount of compound page as a whole, does not include mapped sub-pages.
  *
  * Must be called only for compound pages.
  */
 static inline int compound_mapcount(struct page *page)
 {
     return folio_entire_mapcount(page_folio(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;
 }
 
 int folio_mapcount(struct folio *folio);
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 static inline int total_mapcount(struct page *page)
 {
     return folio_mapcount(page_folio(page));
 }
 
 #else
 static inline int total_mapcount(struct page *page)
 {
     return page_mapcount(page);
 }
 #endif
 
 static inline struct page *virt_to_head_page(const void *x)
 {
     struct page *page = virt_to_page(x);
 
     return compound_head(page);
 }
 
 static inline struct folio *virt_to_folio(const void *x)
 {
     struct page *page = virt_to_page(x);
 
     return page_folio(page);
 }
 
 void __folio_put(struct folio *folio);
 
 void put_pages_list(struct list_head *pages);
 
 void split_page(struct page *page, unsigned int order);
 void folio_copy(struct folio *dst, struct folio *src);
 
 unsigned long nr_free_buffer_pages(void);
 
 /*
  * 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;
 }
 
 void destroy_large_folio(struct folio *folio);
 
 static inline int head_compound_pincount(struct page *head)
 {
     return atomic_read(compound_pincount_ptr(head));
 }
 
 static inline void set_compound_order(struct page *page, unsigned int order)
 {
     page[1].compound_order = order;
 #ifdef CONFIG_64BIT
     page[1].compound_nr = 1U << order;
 #endif
 }
 
 /* Returns the number of pages in this potentially compound page. */
 static inline unsigned long compound_nr(struct page *page)
 {
     if (!PageHead(page))
         return 1;
 #ifdef CONFIG_64BIT
     return page[1].compound_nr;
 #else
     return 1UL << compound_order(page);
 #endif
 }
 
 /* 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);
 }
 
 /**
  * thp_order - Order of a transparent huge page.
  * @page: Head page of a transparent huge page.
  */
 static inline unsigned int thp_order(struct page *page)
 {
     VM_BUG_ON_PGFLAGS(PageTail(page), page);
     return compound_order(page);
 }
 
 /**
  * thp_nr_pages - The number of regular pages in this huge page.
  * @page: The head page of a huge page.
  */
 static inline int thp_nr_pages(struct page *page)
 {
     VM_BUG_ON_PGFLAGS(PageTail(page), page);
     return compound_nr(page);
 }
 
 /**
  * thp_size - Size of a transparent huge page.
  * @page: Head page of a transparent huge page.
  *
  * Return: Number of bytes in this page.
  */
 static inline unsigned long thp_size(struct page *page)
 {
     return PAGE_SIZE << thp_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 do_set_pmd(struct vm_fault *vmf, struct page *page);
 void do_set_pte(struct vm_fault *vmf, struct page *page, unsigned long addr);
 
 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.
  */
 
 #if defined(CONFIG_ZONE_DEVICE) && defined(CONFIG_FS_DAX)
 DECLARE_STATIC_KEY_FALSE(devmap_managed_key);
 
 bool __put_devmap_managed_page_refs(struct page *page, int refs);
 static inline bool put_devmap_managed_page_refs(struct page *page, int refs)
 {
     if (!static_branch_unlikely(&devmap_managed_key))
         return false;
     if (!is_zone_device_page(page))
         return false;
     return __put_devmap_managed_page_refs(page, refs);
 }
 #else /* CONFIG_ZONE_DEVICE && CONFIG_FS_DAX */
 static inline bool put_devmap_managed_page_refs(struct page *page, int refs)
 {
     return false;
 }
 #endif /* CONFIG_ZONE_DEVICE && CONFIG_FS_DAX */
 
 static inline bool put_devmap_managed_page(struct page *page)
 {
     return put_devmap_managed_page_refs(page, 1);
 }
 
 /* 127: arbitrary random number, small enough to assemble well */
 #define folio_ref_zero_or_close_to_overflow(folio) \
     ((unsigned int) folio_ref_count(folio) + 127u <= 127u)
 
 /**
  * folio_get - Increment the reference count on a folio.
  * @folio: The folio.
  *
  * Context: May be called in any context, as long as you know that
  * you have a refcount on the folio.  If you do not already have one,
  * folio_try_get() may be the right interface for you to use.
  */
 static inline void folio_get(struct folio *folio)
 {
     VM_BUG_ON_FOLIO(folio_ref_zero_or_close_to_overflow(folio), folio);
     folio_ref_inc(folio);
 }
 
 static inline void get_page(struct page *page)
 {
     folio_get(page_folio(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;
 }
 
 /**
  * folio_put - Decrement the reference count on a folio.
  * @folio: The folio.
  *
  * If the folio's reference count reaches zero, the memory will be
  * released back to the page allocator and may be used by another
  * allocation immediately.  Do not access the memory or the struct folio
  * after calling folio_put() unless you can be sure that it wasn't the
  * last reference.
  *
  * Context: May be called in process or interrupt context, but not in NMI
  * context.  May be called while holding a spinlock.
  */
 static inline void folio_put(struct folio *folio)
 {
     if (folio_put_testzero(folio))
         __folio_put(folio);
 }
 
 /**
  * folio_put_refs - Reduce the reference count on a folio.
  * @folio: The folio.
  * @refs: The amount to subtract from the folio's reference count.
  *
  * If the folio's reference count reaches zero, the memory will be
  * released back to the page allocator and may be used by another
  * allocation immediately.  Do not access the memory or the struct folio
  * after calling folio_put_refs() unless you can be sure that these weren't
  * the last references.
  *
  * Context: May be called in process or interrupt context, but not in NMI
  * context.  May be called while holding a spinlock.
  */
 static inline void folio_put_refs(struct folio *folio, int refs)
 {
     if (folio_ref_sub_and_test(folio, refs))
         __folio_put(folio);
 }
 
 void release_pages(struct page **pages, int nr);
 
 /**
  * folios_put - Decrement the reference count on an array of folios.
  * @folios: The folios.
  * @nr: How many folios there are.
  *
  * Like folio_put(), but for an array of folios.  This is more efficient
  * than writing the loop yourself as it will optimise the locks which
  * need to be taken if the folios are freed.
  *
  * Context: May be called in process or interrupt context, but not in NMI
  * context.  May be called while holding a spinlock.
  */
 static inline void folios_put(struct folio **folios, unsigned int nr)
 {
     release_pages((struct page **)folios, nr);
 }
 
 static inline void put_page(struct page *page)
 {
     struct folio *folio = page_folio(page);
 
     /*
      * For some devmap managed pages we need to catch refcount transition
      * from 2 to 1:
      */
     if (put_devmap_managed_page(&folio->page))
         return;
     folio_put(folio);
 }
 
 /*
  * 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 folio_try_get_rcu()
  * provides safe operation for get_user_pages(), 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_page_range_dirty_lock(struct page *page, unsigned long npages,
                       bool make_dirty);
 void unpin_user_pages(struct page **pages, unsigned long npages);
 
 static inline bool is_cow_mapping(vm_flags_t flags)
 {
     return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
 }
 
 #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
 
 static inline int folio_nid(const struct folio *folio)
 {
     return page_to_nid(&folio->page);
 }
 
 #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)
 
 /*
  * KASAN per-page tags are stored xor'ed with 0xff. This allows to avoid
  * setting tags for all pages to native kernel tag value 0xff, as the default
  * value 0x00 maps to 0xff.
  */
 
 static inline u8 page_kasan_tag(const struct page *page)
 {
     u8 tag = 0xff;
 
     if (kasan_enabled()) {
         tag = (page->flags >> KASAN_TAG_PGSHIFT) & KASAN_TAG_MASK;
         tag ^= 0xff;
     }
 
     return tag;
 }
 
 static inline void page_kasan_tag_set(struct page *page, u8 tag)
 {
     unsigned long old_flags, flags;
 
     if (!kasan_enabled())
         return;
 
     tag ^= 0xff;
     old_flags = READ_ONCE(page->flags);
     do {
         flags = old_flags;
         flags &= ~(KASAN_TAG_MASK << KASAN_TAG_PGSHIFT);
         flags |= (tag & KASAN_TAG_MASK) << KASAN_TAG_PGSHIFT;
     } while (unlikely(!try_cmpxchg(&page->flags, &old_flags, flags)));
 }
 
 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));
 }
 
 static inline struct zone *folio_zone(const struct folio *folio)
 {
     return page_zone(&folio->page);
 }
 
 static inline pg_data_t *folio_pgdat(const struct folio *folio)
 {
     return page_pgdat(&folio->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
 
 /**
  * folio_pfn - Return the Page Frame Number of a folio.
  * @folio: The folio.
  *
  * A folio may contain multiple pages.  The pages have consecutive
  * Page Frame Numbers.
  *
  * Return: The Page Frame Number of the first page in the folio.
  */
 static inline unsigned long folio_pfn(struct folio *folio)
 {
     return page_to_pfn(&folio->page);
 }
 
 static inline atomic_t *folio_pincount_ptr(struct folio *folio)
 {
     return &folio_page(folio, 1)->compound_pincount;
 }
 
 /**
  * folio_maybe_dma_pinned - Report if a folio may be pinned for DMA.
  * @folio: The folio.
  *
  * This function checks if a folio has been pinned via a call to
  * a function in the pin_user_pages() family.
  *
  * For small folios, 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 folio references".
  *
  * False positives are OK, because: a) it's unlikely for a folio 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 large folios, the result will be exactly correct. That's because
  * we have more tracking data available: the compound_pincount is used
  * instead of the GUP_PIN_COUNTING_BIAS scheme.
  *
  * For more information, please see Documentation/core-api/pin_user_pages.rst.
  *
  * 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 folio_maybe_dma_pinned(struct folio *folio)
 {
     if (folio_test_large(folio))
         return atomic_read(folio_pincount_ptr(folio)) > 0;
 
     /*
      * folio_ref_count() is signed. If that refcount overflows, then
      * folio_ref_count() returns a negative value, and callers will avoid
      * further incrementing the refcount.
      *
      * Here, for that overflow case, use the sign bit to count a little
      * bit higher via unsigned math, and thus still get an accurate result.
      */
     return ((unsigned int)folio_ref_count(folio)) >=
         GUP_PIN_COUNTING_BIAS;
 }
 
 static inline bool page_maybe_dma_pinned(struct page *page)
 {
     return folio_maybe_dma_pinned(page_folio(page));
 }
 
 /*
  * This should most likely only be called during fork() to see whether we
  * should break the cow immediately for an anon page on the src mm.
  *
  * The caller has to hold the PT lock and the vma->vm_mm->->write_protect_seq.
  */
 static inline bool page_needs_cow_for_dma(struct vm_area_struct *vma,
                       struct page *page)
 {
     VM_BUG_ON(!(raw_read_seqcount(&vma->vm_mm->write_protect_seq) & 1));
 
     if (!test_bit(MMF_HAS_PINNED, &vma->vm_mm->flags))
         return false;
 
     return page_maybe_dma_pinned(page);
 }
 
 /* MIGRATE_CMA and ZONE_MOVABLE do not allow pin pages */
 #ifdef CONFIG_MIGRATION
 static inline bool is_longterm_pinnable_page(struct page *page)
 {
 #ifdef CONFIG_CMA
     int mt = get_pageblock_migratetype(page);
 
     if (mt == MIGRATE_CMA || mt == MIGRATE_ISOLATE)
         return false;
 #endif
     /* The zero page may always be pinned */
     if (is_zero_pfn(page_to_pfn(page)))
         return true;
 
     /* Coherent device memory must always allow eviction. */
     if (is_device_coherent_page(page))
         return false;
 
     /* Otherwise, non-movable zone pages can be pinned. */
     return !is_zone_movable_page(page);
 }
 #else
 static inline bool is_longterm_pinnable_page(struct page *page)
 {
     return true;
 }
 #endif
 
 static inline bool folio_is_longterm_pinnable(struct folio *folio)
 {
     return is_longterm_pinnable_page(&folio->page);
 }
 
 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
 }
 
 /**
  * folio_nr_pages - The number of pages in the folio.
  * @folio: The folio.
  *
  * Return: A positive power of two.
  */
 static inline long folio_nr_pages(struct folio *folio)
 {
     return compound_nr(&folio->page);
 }
 
 /**
  * folio_next - Move to the next physical folio.
  * @folio: The folio we're currently operating on.
  *
  * If you have physically contiguous memory which may span more than
  * one folio (eg a &struct bio_vec), use this function to move from one
  * folio to the next.  Do not use it if the memory is only virtually
  * contiguous as the folios are almost certainly not adjacent to each
  * other.  This is the folio equivalent to writing ``page++``.
  *
  * Context: We assume that the folios are refcounted and/or locked at a
  * higher level and do not adjust the reference counts.
  * Return: The next struct folio.
  */
 static inline struct folio *folio_next(struct folio *folio)
 {
     return (struct folio *)folio_page(folio, folio_nr_pages(folio));
 }
 
 /**
  * folio_shift - The size of the memory described by this folio.
  * @folio: The folio.
  *
  * A folio represents a number of bytes which is a power-of-two in size.
  * This function tells you which power-of-two the folio is.  See also
  * folio_size() and folio_order().
  *
  * Context: The caller should have a reference on the folio to prevent
  * it from being split.  It is not necessary for the folio to be locked.
  * Return: The base-2 logarithm of the size of this folio.
  */
 static inline unsigned int folio_shift(struct folio *folio)
 {
     return PAGE_SHIFT + folio_order(folio);
 }
 
 /**
  * folio_size - The number of bytes in a folio.
  * @folio: The folio.
  *
  * Context: The caller should have a reference on the folio to prevent
  * it from being split.  It is not necessary for the folio to be locked.
  * Return: The number of bytes in this folio.
  */
 static inline size_t folio_size(struct folio *folio)
 {
     return PAGE_SIZE << folio_order(folio);
 }
 
 #ifndef HAVE_ARCH_MAKE_PAGE_ACCESSIBLE
 static inline int arch_make_page_accessible(struct page *page)
 {
     return 0;
 }
 #endif
 
 #ifndef HAVE_ARCH_MAKE_FOLIO_ACCESSIBLE
 static inline int arch_make_folio_accessible(struct folio *folio)
 {
     int ret;
     long i, nr = folio_nr_pages(folio);
 
     for (i = 0; i < nr; i++) {
         ret = arch_make_page_accessible(folio_page(folio, i));
         if (ret)
             break;
     }
 
     return ret;
 }
 #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
 
 static inline void *folio_address(const struct folio *folio)
 {
     return page_address(&folio->page);
 }
 
 extern void *page_rmapping(struct page *page);
 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);
 bool folio_mapped(struct folio *folio);
 
 /*
  * 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(const struct page *page)
 {
     /*
      * lru.next has bit 1 set if the page is allocated from the
      * pfmemalloc reserves.  Callers may simply overwrite it if
      * they do not need to preserve that information.
      */
     return (uintptr_t)page->lru.next & BIT(1);
 }
 
 /*
  * Only to be called by the page allocator on a freshly allocated
  * page.
  */
 static inline void set_page_pfmemalloc(struct page *page)
 {
     page->lru.next = (void *)BIT(1);
 }
 
 static inline void clear_page_pfmemalloc(struct page *page)
 {
     page->lru.next = NULL;
 }
 
 /*
  * 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))
 #define offset_in_folio(folio, p) ((unsigned long)(p) & (folio_size(folio) - 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 ucounts *);
 extern void user_shm_unlock(size_t, struct ucounts *);
 
 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,
            pte_t **ptepp, 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 generic_error_remove_page(struct address_space *mapping, 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_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);
 
 struct kvec;
 int get_kernel_pages(const struct kvec *iov, int nr_pages, int write,
             struct page **pages);
 struct page *get_dump_page(unsigned long addr);
 
 bool folio_mark_dirty(struct folio *folio);
 bool set_page_dirty(struct page *page);
 int set_page_dirty_lock(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 manually check if we can map individual PTEs writable,
  * because something (e.g., COW, uffd-wp) blocks that from happening for all
  * PTEs automatically in a writable mapping.
  */
 #define  MM_CP_TRY_CHANGE_WRITABLE     (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 mmu_gather *tlb,
                   struct vm_area_struct *vma, unsigned long start,
                   unsigned long end, pgprot_t newprot,
                   unsigned long cp_flags);
 extern int mprotect_fixup(struct mmu_gather *tlb, 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 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);
 
 extern void adjust_managed_page_count(struct page *page, long count);
 extern void mem_init_print_info(void);
 
 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);
     adjust_managed_page_count(page, 1);
 }
 #define free_highmem_page(page) free_reserved_page(page)
 
 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 image (initmem)");
 }
 
 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, MEMBLOCK_NONE)
  * 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_NUMA
 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_range(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 void calculate_min_free_kbytes(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, struct anon_vma_name *);
 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 int set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file);
 extern int replace_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);
 unsigned long randomize_page(unsigned long start, unsigned long range);
 
 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 vm_fault_t 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);
 
 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);
 
 /**
  * find_vma_intersection() - Look up the first VMA which intersects the interval
  * @mm: The process address space.
  * @start_addr: The inclusive start user address.
  * @end_addr: The exclusive end user address.
  *
  * Returns: The first VMA within the provided range, %NULL otherwise.  Assumes
  * 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;
 }
 
 /**
  * vma_lookup() - Find a VMA at a specific address
  * @mm: The process address space.
  * @addr: The user address.
  *
  * Return: The vm_area_struct at the given address, %NULL otherwise.
  */
 static inline
 struct vm_area_struct *vma_lookup(struct mm_struct *mm, unsigned long addr)
 {
     struct vm_area_struct *vma = find_vma(mm, addr);
 
     if (vma && 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 remap_pfn_range_notrack(struct vm_area_struct *vma, unsigned long addr,
         unsigned long pfn, unsigned long size, pgprot_t prot);
 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_NOFAULT    0x80    /* do not fault in pages */
 #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_REMOTE 0x2000  /* we are working on non-current tsk/mm */
 #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;
 }
 
 /*
  * Indicates for which pages that are write-protected in the page table,
  * whether GUP has to trigger unsharing via FAULT_FLAG_UNSHARE such that the
  * GUP pin will remain consistent with the pages mapped into the page tables
  * of the MM.
  *
  * Temporary unmapping of PageAnonExclusive() pages or clearing of
  * PageAnonExclusive() has to protect against concurrent GUP:
  * * Ordinary GUP: Using the PT lock
  * * GUP-fast and fork(): mm->write_protect_seq
  * * GUP-fast and KSM or temporary unmapping (swap, migration):
  *   clear/invalidate+flush of the page table entry
  *
  * Must be called with the (sub)page that's actually referenced via the
  * page table entry, which might not necessarily be the head page for a
  * PTE-mapped THP.
  */
 static inline bool gup_must_unshare(unsigned int flags, struct page *page)
 {
     /*
      * FOLL_WRITE is implicitly handled correctly as the page table entry
      * has to be writable -- and if it references (part of) an anonymous
      * folio, that part is required to be marked exclusive.
      */
     if ((flags & (FOLL_WRITE | FOLL_PIN)) != FOLL_PIN)
         return false;
     /*
      * Note: PageAnon(page) is stable until the page is actually getting
      * freed.
      */
     if (!PageAnon(page))
         return false;
     /*
      * Note that PageKsm() pages cannot be exclusive, and consequently,
      * cannot get pinned.
      */
     return !PageAnonExclusive(page);
 }
 
 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_MAYBE(CONFIG_INIT_ON_ALLOC_DEFAULT_ON, init_on_alloc);
 static inline bool want_init_on_alloc(gfp_t flags)
 {
     if (static_branch_maybe(CONFIG_INIT_ON_ALLOC_DEFAULT_ON,
                 &init_on_alloc))
         return true;
     return flags & __GFP_ZERO;
 }
 
 DECLARE_STATIC_KEY_MAYBE(CONFIG_INIT_ON_FREE_DEFAULT_ON, init_on_free);
 static inline bool want_init_on_free(void)
 {
     return static_branch_maybe(CONFIG_INIT_ON_FREE_DEFAULT_ON,
                    &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);
 
 #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,
         struct dev_pagemap *pgmap);
 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, struct page *reuse);
 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,
     MF_UNPOISON = 1 << 4,
     MF_SW_SIMULATED = 1 << 5,
     MF_NO_RETRY = 1 << 6,
 };
 int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index,
               unsigned long count, int mf_flags);
 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);
 extern atomic_long_t num_poisoned_pages __read_mostly;
 extern int soft_offline_page(unsigned long pfn, int flags);
 #ifdef CONFIG_MEMORY_FAILURE
 extern int __get_huge_page_for_hwpoison(unsigned long pfn, int flags);
 #else
 static inline int __get_huge_page_for_hwpoison(unsigned long pfn, int flags)
 {
     return 0;
 }
 #endif
 
 #ifndef arch_memory_failure
 static inline int arch_memory_failure(unsigned long pfn, int flags)
 {
     return -ENXIO;
 }
 #endif
 
 #ifndef arch_is_platform_page
 static inline bool arch_is_platform_page(u64 paddr)
 {
     return false;
 }
 #endif
 
 /*
  * 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_HUGE,
     MF_MSG_FREE_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_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;
 
 #ifdef CONFIG_PRINTK
 void mem_dump_obj(void *object);
 #else
 static inline void mem_dump_obj(void *object) {}
 #endif
 
 /**
  * seal_check_future_write - Check for F_SEAL_FUTURE_WRITE flag and handle it
  * @seals: the seals to check
  * @vma: the vma to operate on
  *
  * Check whether F_SEAL_FUTURE_WRITE is set; if so, do proper check/handling on
  * the vma flags.  Return 0 if check pass, or <0 for errors.
  */
 static inline int seal_check_future_write(int seals, struct vm_area_struct *vma)
 {
     if (seals & F_SEAL_FUTURE_WRITE) {
         /*
          * New PROT_WRITE and MAP_SHARED mmaps are not allowed when
          * "future write" seal active.
          */
         if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_WRITE))
             return -EPERM;
 
         /*
          * Since an F_SEAL_FUTURE_WRITE sealed memfd can be mapped as
          * MAP_SHARED and read-only, take care to not allow mprotect to
          * revert protections on such mappings. Do this only for shared
          * mappings. For private mappings, don't need to mask
          * VM_MAYWRITE as we still want them to be COW-writable.
          */
         if (vma->vm_flags & VM_SHARED)
             vma->vm_flags &= ~(VM_MAYWRITE);
     }
 
     return 0;
 }
 
 #ifdef CONFIG_ANON_VMA_NAME
 int madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
               unsigned long len_in,
               struct anon_vma_name *anon_name);
 #else
 static inline int
 madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
               unsigned long len_in, struct anon_vma_name *anon_name) {
     return 0;
 }
 #endif
 
 /*
  * Whether to drop the pte markers, for example, the uffd-wp information for
  * file-backed memory.  This should only be specified when we will completely
  * drop the page in the mm, either by truncation or unmapping of the vma.  By
  * default, the flag is not set.
  */
 #define  ZAP_FLAG_DROP_MARKER        ((__force zap_flags_t) BIT(0))
 
 #endif /* _LINUX_MM_H */