TOMOYO Linux Cross Reference
Linux/include/linux/mm.h

   /* SPDX-License-Identifier: GPL-2.0 */
   #ifndef _LINUX_MM_H
   #define _LINUX_MM_H
   
   #include <linux/errno.h>
   
   #ifdef __KERNEL__
   
   #include <linux/mmdebug.h>
  #include <linux/gfp.h>
  #include <linux/bug.h>
  #include <linux/list.h>
  #include <linux/mmzone.h>
  #include <linux/rbtree.h>
  #include <linux/atomic.h>
  #include <linux/debug_locks.h>
  #include <linux/mm_types.h>
  #include <linux/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_ref.h>
  #include <linux/memremap.h>
  
  struct mempolicy;
  struct anon_vma;
  struct anon_vma_chain;
  struct file_ra_state;
  struct user_struct;
  struct writeback_control;
  struct bdi_writeback;
  
  void init_mm_internals(void);
  
  #ifndef CONFIG_NEED_MULTIPLE_NODES      /* Don't use mapnrs, do it properly */
  extern unsigned long max_mapnr;
  
  static inline void set_max_mapnr(unsigned long limit)
  {
          max_mapnr = limit;
  }
  #else
  static inline void set_max_mapnr(unsigned long limit) { }
  #endif
  
  extern unsigned long 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/pgtable.h>
  #include <asm/processor.h>
  
  #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.
  * Those architectures should provide their own implementation of "struct page"
  * zeroing by defining this macro in <asm/pgtable.h>.
  */
 #ifndef mm_zero_struct_page
 #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;
 
 extern int overcommit_ratio_handler(struct ctl_table *, int, void __user *,
                                     size_t *, loff_t *);
 extern int overcommit_kbytes_handler(struct ctl_table *, int, void __user *,
                                     size_t *, loff_t *);
 
 #define nth_page(page,n) pfn_to_page(page_to_pfn((page)) + (n))
 
 /* to align the pointer to the (next) page boundary */
 #define PAGE_ALIGN(addr) ALIGN(addr, PAGE_SIZE)
 
 /* test whether an address (unsigned long or pointer) is aligned to PAGE_SIZE */
 #define PAGE_ALIGNED(addr)      IS_ALIGNED((unsigned long)(addr), PAGE_SIZE)
 
 /*
  * 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).
  */
 
 extern struct kmem_cache *vm_area_cachep;
 
 #ifndef CONFIG_MMU
 extern struct rb_root nommu_region_tree;
 extern struct rw_semaphore nommu_region_sem;
 
 extern unsigned int kobjsize(const void *objp);
 #endif
 
 /*
  * vm_flags in vm_area_struct, see mm_types.h.
  * When changing, update also include/trace/events/mmflags.h
  */
 #define VM_NONE         0x00000000
 
 #define VM_READ         0x00000001      /* currently active flags */
 #define VM_WRITE        0x00000002
 #define VM_EXEC         0x00000004
 #define VM_SHARED       0x00000008
 
 /* mprotect() hardcodes VM_MAYREAD >> 4 == VM_READ, and so for r/w/x bits. */
 #define VM_MAYREAD      0x00000010      /* limits for mprotect() etc */
 #define VM_MAYWRITE     0x00000020
 #define VM_MAYEXEC      0x00000040
 #define VM_MAYSHARE     0x00000080
 
 #define VM_GROWSDOWN    0x00000100      /* general info on the segment */
 #define VM_UFFD_MISSING 0x00000200      /* missing pages tracking */
 #define VM_PFNMAP       0x00000400      /* Page-ranges managed without "struct page", just pure PFN */
 #define VM_DENYWRITE    0x00000800      /* ETXTBSY on write attempts.. */
 #define VM_UFFD_WP      0x00001000      /* wrprotect pages tracking */
 
 #define VM_LOCKED       0x00002000
 #define VM_IO           0x00004000      /* Memory mapped I/O or similar */
 
                                         /* Used by sys_madvise() */
 #define VM_SEQ_READ     0x00008000      /* App will access data sequentially */
 #define VM_RAND_READ    0x00010000      /* App will not benefit from clustered reads */
 
 #define VM_DONTCOPY     0x00020000      /* Do not copy this vma on fork */
 #define VM_DONTEXPAND   0x00040000      /* Cannot expand with mremap() */
 #define VM_LOCKONFAULT  0x00080000      /* Lock the pages covered when they are faulted in */
 #define VM_ACCOUNT      0x00100000      /* Is a VM accounted object */
 #define VM_NORESERVE    0x00200000      /* should the VM suppress accounting */
 #define VM_HUGETLB      0x00400000      /* Huge TLB Page VM */
 #define VM_SYNC         0x00800000      /* Synchronous page faults */
 #define VM_ARCH_1       0x01000000      /* Architecture-specific flag */
 #define VM_WIPEONFORK   0x02000000      /* Wipe VMA contents in child. */
 #define VM_DONTDUMP     0x04000000      /* Do not include in the core dump */
 
 #ifdef CONFIG_MEM_SOFT_DIRTY
 # define VM_SOFTDIRTY   0x08000000      /* Not soft dirty clean area */
 #else
 # define VM_SOFTDIRTY   0
 #endif
 
 #define VM_MIXEDMAP     0x10000000      /* Can contain "struct page" and pure PFN pages */
 #define VM_HUGEPAGE     0x20000000      /* MADV_HUGEPAGE marked this vma */
 #define VM_NOHUGEPAGE   0x40000000      /* MADV_NOHUGEPAGE marked this vma */
 #define VM_MERGEABLE    0x80000000      /* KSM may merge identical pages */
 
 #ifdef CONFIG_ARCH_USES_HIGH_VMA_FLAGS
 #define VM_HIGH_ARCH_BIT_0      32      /* bit only usable on 64-bit architectures */
 #define VM_HIGH_ARCH_BIT_1      33      /* bit only usable on 64-bit architectures */
 #define VM_HIGH_ARCH_BIT_2      34      /* bit only usable on 64-bit architectures */
 #define VM_HIGH_ARCH_BIT_3      35      /* bit only usable on 64-bit architectures */
 #define VM_HIGH_ARCH_BIT_4      36      /* bit only usable on 64-bit architectures */
 #define VM_HIGH_ARCH_0  BIT(VM_HIGH_ARCH_BIT_0)
 #define VM_HIGH_ARCH_1  BIT(VM_HIGH_ARCH_BIT_1)
 #define VM_HIGH_ARCH_2  BIT(VM_HIGH_ARCH_BIT_2)
 #define VM_HIGH_ARCH_3  BIT(VM_HIGH_ARCH_BIT_3)
 #define VM_HIGH_ARCH_4  BIT(VM_HIGH_ARCH_BIT_4)
 #endif /* CONFIG_ARCH_USES_HIGH_VMA_FLAGS */
 
 #if defined(CONFIG_X86)
 # define VM_PAT         VM_ARCH_1       /* PAT reserves whole VMA at once (x86) */
 #if defined (CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS)
 # 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
 # define VM_PKEY_BIT2   VM_HIGH_ARCH_2
 # define VM_PKEY_BIT3   VM_HIGH_ARCH_3
 #endif
 #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_METAG)
 # define VM_GROWSUP     VM_ARCH_1
 #elif defined(CONFIG_IA64)
 # define VM_GROWSUP     VM_ARCH_1
 #elif !defined(CONFIG_MMU)
 # define VM_MAPPED_COPY VM_ARCH_1       /* T if mapped copy of data (nommu mmap) */
 #endif
 
 #if defined(CONFIG_X86_INTEL_MPX)
 /* MPX specific bounds table or bounds directory */
 # define VM_MPX         VM_HIGH_ARCH_4
 #else
 # define VM_MPX         VM_NONE
 #endif
 
 #ifndef VM_GROWSUP
 # define VM_GROWSUP     VM_NONE
 #endif
 
 /* Bits set in the VMA until the stack is in its final location */
 #define VM_STACK_INCOMPLETE_SETUP       (VM_RAND_READ | VM_SEQ_READ)
 
 #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)
 
 /*
  * Special vmas that are non-mergable, non-mlock()able.
  * Note: mm/huge_memory.c VM_NO_THP depends on this definition.
  */
 #define VM_SPECIAL (VM_IO | VM_DONTEXPAND | VM_PFNMAP | VM_MIXEDMAP)
 
 /* 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))
 
 /*
  * mapping from the currently active vm_flags protection bits (the
  * low four bits) to a page protection mask..
  */
 extern pgprot_t protection_map[16];
 
 #define FAULT_FLAG_WRITE        0x01    /* Fault was a write access */
 #define FAULT_FLAG_MKWRITE      0x02    /* Fault was mkwrite of existing pte */
 #define FAULT_FLAG_ALLOW_RETRY  0x04    /* Retry fault if blocking */
 #define FAULT_FLAG_RETRY_NOWAIT 0x08    /* Don't drop mmap_sem and wait when retrying */
 #define FAULT_FLAG_KILLABLE     0x10    /* The fault task is in SIGKILL killable region */
 #define FAULT_FLAG_TRIED        0x20    /* Second try */
 #define FAULT_FLAG_USER         0x40    /* The fault originated in userspace */
 #define FAULT_FLAG_REMOTE       0x80    /* faulting for non current tsk/mm */
 #define FAULT_FLAG_INSTRUCTION  0x100   /* The fault was during an instruction fetch */
 
 #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" }
 
 /*
  * vm_fault is filled by the the pagefault handler and passed to the vma's
  * ->fault function. The vma's ->fault is responsible for returning a bitmask
  * of VM_FAULT_xxx flags that give details about how the fault was handled.
  *
  * MM layer fills up gfp_mask for page allocations but fault handler might
  * alter it if its implementation requires a different allocation context.
  *
  * pgoff should be used in favour of virtual_address, if possible.
  */
 struct vm_fault {
         struct vm_area_struct *vma;     /* Target VMA */
         unsigned int flags;             /* FAULT_FLAG_xxx flags */
         gfp_t gfp_mask;                 /* gfp mask to be used for allocations */
         pgoff_t pgoff;                  /* Logical page offset based on vma */
         unsigned long address;          /* Faulting virtual address */
         pmd_t *pmd;                     /* Pointer to pmd entry matching
                                          * the 'address' */
         pud_t *pud;                     /* Pointer to pud entry matching
                                          * the 'address'
                                          */
         pte_t orig_pte;                 /* Value of PTE at the time of fault */
 
         struct page *cow_page;          /* Page handler may use for COW fault */
         struct mem_cgroup *memcg;       /* Cgroup cow_page belongs to */
         struct page *page;              /* ->fault handlers should return a
                                          * page here, unless VM_FAULT_NOPAGE
                                          * is set (which is also implied by
                                          * VM_FAULT_ERROR).
                                          */
         /* These three entries are valid only while holding ptl lock */
         pte_t *pte;                     /* Pointer to pte entry matching
                                          * the 'address'. NULL if the page
                                          * table hasn't been allocated.
                                          */
         spinlock_t *ptl;                /* Page table lock.
                                          * Protects pte page table if 'pte'
                                          * is not NULL, otherwise pmd.
                                          */
         pgtable_t prealloc_pte;         /* Pre-allocated pte page table.
                                          * vm_ops->map_pages() calls
                                          * alloc_set_pte() from atomic context.
                                          * do_fault_around() pre-allocates
                                          * page table to avoid allocation from
                                          * atomic context.
                                          */
 };
 
 /* page entry size for vm->huge_fault() */
 enum page_entry_size {
         PE_SIZE_PTE = 0,
         PE_SIZE_PMD,
         PE_SIZE_PUD,
 };
 
 /*
  * These are the virtual MM functions - opening of an area, closing and
  * unmapping it (needed to keep files on disk up-to-date etc), pointer
  * to the functions called when a no-page or a wp-page exception occurs. 
  */
 struct vm_operations_struct {
         void (*open)(struct vm_area_struct * area);
         void (*close)(struct vm_area_struct * area);
         int (*split)(struct vm_area_struct * area, unsigned long addr);
         int (*mremap)(struct vm_area_struct * area);
         int (*fault)(struct vm_fault *vmf);
         int (*huge_fault)(struct vm_fault *vmf, enum page_entry_size pe_size);
         void (*map_pages)(struct vm_fault *vmf,
                         pgoff_t start_pgoff, pgoff_t end_pgoff);
 
         /* notification that a previously read-only page is about to become
          * writable, if an error is returned it will cause a SIGBUS */
         int (*page_mkwrite)(struct vm_fault *vmf);
 
         /* same as page_mkwrite when using VM_PFNMAP|VM_MIXEDMAP */
         int (*pfn_mkwrite)(struct vm_fault *vmf);
 
         /* called by access_process_vm when get_user_pages() fails, typically
          * for use by special VMAs that can switch between memory and hardware
          */
         int (*access)(struct vm_area_struct *vma, unsigned long addr,
                       void *buf, int len, int write);
 
         /* Called by the /proc/PID/maps code to ask the vma whether it
          * has a special name.  Returning non-NULL will also cause this
          * vma to be dumped unconditionally. */
         const char *(*name)(struct vm_area_struct *vma);
 
 #ifdef CONFIG_NUMA
         /*
          * set_policy() op must add a reference to any non-NULL @new mempolicy
          * to hold the policy upon return.  Caller should pass NULL @new to
          * remove a policy and fall back to surrounding context--i.e. do not
          * install a MPOL_DEFAULT policy, nor the task or system default
          * mempolicy.
          */
         int (*set_policy)(struct vm_area_struct *vma, struct mempolicy *new);
 
         /*
          * get_policy() op must add reference [mpol_get()] to any policy at
          * (vma,addr) marked as MPOL_SHARED.  The shared policy infrastructure
          * in mm/mempolicy.c will do this automatically.
          * get_policy() must NOT add a ref if the policy at (vma,addr) is not
          * marked as MPOL_SHARED. vma policies are protected by the mmap_sem.
          * 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);
 };
 
 struct mmu_gather;
 struct inode;
 
 #define page_private(page)              ((page)->private)
 #define set_page_private(page, v)       ((page)->private = (v))
 
 #if !defined(__HAVE_ARCH_PTE_DEVMAP) || !defined(CONFIG_TRANSPARENT_HUGEPAGE)
 static inline int pmd_devmap(pmd_t pmd)
 {
         return 0;
 }
 static inline int pud_devmap(pud_t pud)
 {
         return 0;
 }
 static inline int pgd_devmap(pgd_t pgd)
 {
         return 0;
 }
 #endif
 
 /*
  * FIXME: take this include out, include page-flags.h in
  * files which need it (119 of them)
  */
 #include <linux/page-flags.h>
 #include <linux/huge_mm.h>
 
 /*
  * Methods to modify the page usage count.
  *
  * What counts for a page usage:
  * - cache mapping   (page->mapping)
  * - private data    (page->private)
  * - page mapped in a task's page tables, each mapping
  *   is counted separately
  *
  * Also, many kernel routines increase the page count before a critical
  * routine so they can be sure the page doesn't go away from under them.
  */
 
 /*
  * Drop a ref, return true if the refcount fell to zero (the page has no users)
  */
 static inline int put_page_testzero(struct page *page)
 {
         VM_BUG_ON_PAGE(page_ref_count(page) == 0, page);
         return page_ref_dec_and_test(page);
 }
 
 /*
  * Try to grab a ref unless the page has a refcount of zero, return false if
  * that is the case.
  * This can be called when MMU is off so it must not access
  * any of the virtual mappings.
  */
 static inline int get_page_unless_zero(struct page *page)
 {
         return page_ref_add_unless(page, 1, 0);
 }
 
 extern int page_is_ram(unsigned long pfn);
 
 enum {
         REGION_INTERSECTS,
         REGION_DISJOINT,
         REGION_MIXED,
 };
 
 int region_intersects(resource_size_t offset, size_t size, unsigned long flags,
                       unsigned long desc);
 
 /* Support for virtually mapped pages */
 struct page *vmalloc_to_page(const void *addr);
 unsigned long vmalloc_to_pfn(const void *addr);
 
 /*
  * Determine if an address is within the vmalloc range
  *
  * On nommu, vmalloc/vfree wrap through kmalloc/kfree directly, so there
  * is no special casing required.
  */
 static inline bool is_vmalloc_addr(const void *x)
 {
 #ifdef CONFIG_MMU
         unsigned long addr = (unsigned long)x;
 
         return addr >= VMALLOC_START && addr < VMALLOC_END;
 #else
         return false;
 #endif
 }
 #ifdef CONFIG_MMU
 extern int is_vmalloc_or_module_addr(const void *x);
 #else
 static inline int is_vmalloc_or_module_addr(const void *x)
 {
         return 0;
 }
 #endif
 
 extern void *kvmalloc_node(size_t size, gfp_t flags, int node);
 static inline void *kvmalloc(size_t size, gfp_t flags)
 {
         return kvmalloc_node(size, flags, NUMA_NO_NODE);
 }
 static inline void *kvzalloc_node(size_t size, gfp_t flags, int node)
 {
         return kvmalloc_node(size, flags | __GFP_ZERO, node);
 }
 static inline void *kvzalloc(size_t size, gfp_t flags)
 {
         return kvmalloc(size, flags | __GFP_ZERO);
 }
 
 static inline void *kvmalloc_array(size_t n, size_t size, gfp_t flags)
 {
         if (size != 0 && n > SIZE_MAX / size)
                 return NULL;
 
         return kvmalloc(n * size, flags);
 }
 
 extern void kvfree(const void *addr);
 
 static inline atomic_t *compound_mapcount_ptr(struct page *page)
 {
         return &page[1].compound_mapcount;
 }
 
 static inline int compound_mapcount(struct page *page)
 {
         VM_BUG_ON_PAGE(!PageCompound(page), page);
         page = compound_head(page);
         return atomic_read(compound_mapcount_ptr(page)) + 1;
 }
 
 /*
  * 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);
 
 static inline int page_mapcount(struct page *page)
 {
         VM_BUG_ON_PAGE(PageSlab(page), page);
 
         if (unlikely(PageCompound(page)))
                 return __page_mapcount(page);
         return atomic_read(&page->_mapcount) + 1;
 }
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 int total_mapcount(struct page *page);
 int page_trans_huge_mapcount(struct page *page, int *total_mapcount);
 #else
 static inline int total_mapcount(struct page *page)
 {
         return page_mapcount(page);
 }
 static inline int page_trans_huge_mapcount(struct page *page,
                                            int *total_mapcount)
 {
         int mapcount = page_mapcount(page);
         if (total_mapcount)
                 *total_mapcount = mapcount;
         return mapcount;
 }
 #endif
 
 static inline struct page *virt_to_head_page(const void *x)
 {
         struct page *page = virt_to_page(x);
 
         return compound_head(page);
 }
 
 void __put_page(struct page *page);
 
 void put_pages_list(struct list_head *pages);
 
 void split_page(struct page *page, unsigned int order);
 
 /*
  * Compound pages have a destructor function.  Provide a
  * prototype for that function and accessor functions.
  * These are _only_ valid on the head of a compound page.
  */
 typedef void compound_page_dtor(struct page *);
 
 /* Keep the enum in sync with compound_page_dtors array in mm/page_alloc.c */
 enum compound_dtor_id {
         NULL_COMPOUND_DTOR,
         COMPOUND_PAGE_DTOR,
 #ifdef CONFIG_HUGETLB_PAGE
         HUGETLB_PAGE_DTOR,
 #endif
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
         TRANSHUGE_PAGE_DTOR,
 #endif
         NR_COMPOUND_DTORS,
 };
 extern compound_page_dtor * const compound_page_dtors[];
 
 static inline void set_compound_page_dtor(struct page *page,
                 enum compound_dtor_id compound_dtor)
 {
         VM_BUG_ON_PAGE(compound_dtor >= NR_COMPOUND_DTORS, page);
         page[1].compound_dtor = compound_dtor;
 }
 
 static inline compound_page_dtor *get_compound_page_dtor(struct page *page)
 {
         VM_BUG_ON_PAGE(page[1].compound_dtor >= NR_COMPOUND_DTORS, page);
         return compound_page_dtors[page[1].compound_dtor];
 }
 
 static inline unsigned int compound_order(struct page *page)
 {
         if (!PageHead(page))
                 return 0;
         return page[1].compound_order;
 }
 
 static inline void set_compound_order(struct page *page, unsigned int order)
 {
         page[1].compound_order = order;
 }
 
 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;
 }
 
 int alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg,
                 struct page *page);
 int finish_fault(struct vm_fault *vmf);
 int 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->page_tree, and indexed by offset.
  * Where 2.4 and early 2.6 kernels kept dirty/clean pages in per-address_space
  * lists, we instead now tag pages as dirty/writeback in the radix tree.
  *
  * All pagecache pages may be subject to I/O:
  * - inode pages may need to be read from disk,
  * - inode pages which have been modified and are MAP_SHARED may need
  *   to be written back to the inode on disk,
  * - anonymous pages (including MAP_PRIVATE file mappings) which have been
  *   modified may need to be swapped out to swap space and (later) to be read
  *   back into memory.
  */
 
 /*
  * The zone field is never updated after free_area_init_core()
  * sets it, so none of the operations on it need to be atomic.
  */
 
 /* Page flags: | [SECTION] | [NODE] | ZONE | [LAST_CPUPID] | ... | FLAGS | */
 #define SECTIONS_PGOFF          ((sizeof(unsigned long)*8) - SECTIONS_WIDTH)
 #define NODES_PGOFF             (SECTIONS_PGOFF - NODES_WIDTH)
 #define ZONES_PGOFF             (NODES_PGOFF - ZONES_WIDTH)
 #define LAST_CPUPID_PGOFF       (ZONES_PGOFF - LAST_CPUPID_WIDTH)
 
 /*
  * Define the bit shifts to access each section.  For non-existent
  * sections we define the shift as 0; that plus a 0 mask ensures
  * the compiler will optimise away reference to them.
  */
 #define SECTIONS_PGSHIFT        (SECTIONS_PGOFF * (SECTIONS_WIDTH != 0))
 #define NODES_PGSHIFT           (NODES_PGOFF * (NODES_WIDTH != 0))
 #define ZONES_PGSHIFT           (ZONES_PGOFF * (ZONES_WIDTH != 0))
 #define LAST_CPUPID_PGSHIFT     (LAST_CPUPID_PGOFF * (LAST_CPUPID_WIDTH != 0))
 
 /* NODE:ZONE or SECTION:ZONE is used to ID a zone for the buddy allocator */
 #ifdef NODE_NOT_IN_PAGE_FLAGS
 #define ZONEID_SHIFT            (SECTIONS_SHIFT + ZONES_SHIFT)
 #define ZONEID_PGOFF            ((SECTIONS_PGOFF < ZONES_PGOFF)? \
                                                 SECTIONS_PGOFF : ZONES_PGOFF)
 #else
 #define ZONEID_SHIFT            (NODES_SHIFT + ZONES_SHIFT)
 #define ZONEID_PGOFF            ((NODES_PGOFF < ZONES_PGOFF)? \
                                                 NODES_PGOFF : ZONES_PGOFF)
 #endif
 
 #define ZONEID_PGSHIFT          (ZONEID_PGOFF * (ZONEID_SHIFT != 0))
 
 #if SECTIONS_WIDTH+NODES_WIDTH+ZONES_WIDTH > BITS_PER_LONG - NR_PAGEFLAGS
 #error SECTIONS_WIDTH+NODES_WIDTH+ZONES_WIDTH > BITS_PER_LONG - NR_PAGEFLAGS
 #endif
 
 #define ZONES_MASK              ((1UL << ZONES_WIDTH) - 1)
 #define NODES_MASK              ((1UL << NODES_WIDTH) - 1)
 #define SECTIONS_MASK           ((1UL << SECTIONS_WIDTH) - 1)
 #define LAST_CPUPID_MASK        ((1UL << LAST_CPUPID_SHIFT) - 1)
 #define ZONEID_MASK             ((1UL << ZONEID_SHIFT) - 1)
 
 static inline enum zone_type page_zonenum(const struct page *page)
 {
         return (page->flags >> ZONES_PGSHIFT) & ZONES_MASK;
 }
 
 #ifdef CONFIG_ZONE_DEVICE
 static inline bool is_zone_device_page(const struct page *page)
 {
         return page_zonenum(page) == ZONE_DEVICE;
 }
 #else
 static inline bool is_zone_device_page(const struct page *page)
 {
         return false;
 }
 #endif
 
 #if defined(CONFIG_DEVICE_PRIVATE) || defined(CONFIG_DEVICE_PUBLIC)
 void put_zone_device_private_or_public_page(struct page *page);
 DECLARE_STATIC_KEY_FALSE(device_private_key);
 #define IS_HMM_ENABLED static_branch_unlikely(&device_private_key)
 static inline bool is_device_private_page(const struct page *page);
 static inline bool is_device_public_page(const struct page *page);
 #else /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */
 static inline void put_zone_device_private_or_public_page(struct page *page)
 {
 }
 #define IS_HMM_ENABLED 0
 static inline bool is_device_private_page(const struct page *page)
 {
         return false;
 }
 static inline bool is_device_public_page(const struct page *page)
 {
         return false;
 }
 #endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */
 
 
 static inline void get_page(struct page *page)
 {
         page = compound_head(page);
         /*
          * Getting a normal page or the head of a compound page
          * requires to already have an elevated page->_refcount.
          */
         VM_BUG_ON_PAGE(page_ref_count(page) <= 0, page);
         page_ref_inc(page);
 }
 
 static inline void put_page(struct page *page)
 {
         page = compound_head(page);
 
         /*
          * For private device pages we need to catch refcount transition from
          * 2 to 1, when refcount reach one it means the private device page is
          * free and we need to inform the device driver through callback. See
          * include/linux/memremap.h and HMM for details.
          */
         if (IS_HMM_ENABLED && unlikely(is_device_private_page(page) ||
             unlikely(is_device_public_page(page)))) {
                 put_zone_device_private_or_public_page(page);
                 return;
         }
 
         if (put_page_testzero(page))
                 __put_page(page);
 }
 
 #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;
 }
 
 static inline int zone_to_nid(struct zone *zone)
 {
 #ifdef CONFIG_NUMA
         return zone->node;
 #else
         return 0;
 #endif
 }
 
 #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)
 {
         return (page->flags >> NODES_PGSHIFT) & NODES_MASK;
 }
 #endif
 
 #ifdef CONFIG_NUMA_BALANCING
 static inline int cpu_pid_to_cpupid(int cpu, int pid)
 {
         return ((cpu & LAST__CPU_MASK) << LAST__PID_SHIFT) | (pid & LAST__PID_MASK);
 }
 
 static inline int cpupid_to_pid(int cpupid)
 {
         return cpupid & LAST__PID_MASK;
 }
 
 static inline int cpupid_to_cpu(int cpupid)
 {
         return (cpupid >> LAST__PID_SHIFT) & LAST__CPU_MASK;
 }
 
 static inline int cpupid_to_nid(int cpupid)
 {
         return cpu_to_node(cpupid_to_cpu(cpupid));
 }
 
 static inline bool cpupid_pid_unset(int cpupid)
 {
         return cpupid_to_pid(cpupid) == (-1 & LAST__PID_MASK);
 }
 
 static inline bool cpupid_cpu_unset(int cpupid)
 {
         return cpupid_to_cpu(cpupid) == (-1 & LAST__CPU_MASK);
 }
 
 static inline bool __cpupid_match_pid(pid_t task_pid, int cpupid)
 {
         return (task_pid & LAST__PID_MASK) == cpupid_to_pid(cpupid);
 }
 
 #define cpupid_match_pid(task, cpupid) __cpupid_match_pid(task->pid, cpupid)
 #ifdef LAST_CPUPID_NOT_IN_PAGE_FLAGS
 static inline int page_cpupid_xchg_last(struct page *page, int cpupid)
 {
         return xchg(&page->_last_cpupid, cpupid & LAST_CPUPID_MASK);
 }
 
 static inline int page_cpupid_last(struct page *page)
 {
         return page->_last_cpupid;
 }
 static inline void page_cpupid_reset_last(struct page *page)
 {
         page->_last_cpupid = -1 & LAST_CPUPID_MASK;
 }
 #else
 static inline int page_cpupid_last(struct page *page)
 {
         return (page->flags >> LAST_CPUPID_PGSHIFT) & LAST_CPUPID_MASK;
 }
 
 extern int page_cpupid_xchg_last(struct page *page, int cpupid);
 
 static inline void page_cpupid_reset_last(struct page *page)
 {
         page->flags |= LAST_CPUPID_MASK << LAST_CPUPID_PGSHIFT;
 }
 #endif /* LAST_CPUPID_NOT_IN_PAGE_FLAGS */
 #else /* !CONFIG_NUMA_BALANCING */
 static inline int page_cpupid_xchg_last(struct page *page, int cpupid)
 {
         return page_to_nid(page); /* XXX */
 }
 
 static inline int page_cpupid_last(struct page *page)
 {
         return page_to_nid(page); /* XXX */
 }
 
 static inline int cpupid_to_nid(int cpupid)
 {
         return -1;
 }
 
 static inline int cpupid_to_pid(int cpupid)
 {
         return -1;
 }
 
 static inline int cpupid_to_cpu(int cpupid)
 {
         return -1;
 }
 
 static inline int cpu_pid_to_cpupid(int nid, int pid)
 {
         return -1;
 }
 
 static inline bool cpupid_pid_unset(int cpupid)
 {
         return 1;
 }
 
 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 */
 
 static inline struct zone *page_zone(const struct page *page)
 {
         return &NODE_DATA(page_to_nid(page))->node_zones[page_zonenum(page)];
 }
 
 static inline pg_data_t *page_pgdat(const struct page *page)
 {
         return NODE_DATA(page_to_nid(page));
 }
 
 #ifdef SECTION_IN_PAGE_FLAGS
 static inline void set_page_section(struct page *page, unsigned long section)
 {
         page->flags &= ~(SECTIONS_MASK << SECTIONS_PGSHIFT);
         page->flags |= (section & SECTIONS_MASK) << SECTIONS_PGSHIFT;
 }
 
 static inline unsigned long page_to_section(const struct page *page)
 {
         return (page->flags >> SECTIONS_PGSHIFT) & SECTIONS_MASK;
 }
 #endif
 
 static inline void set_page_zone(struct page *page, enum zone_type zone)
 {
         page->flags &= ~(ZONES_MASK << ZONES_PGSHIFT);
         page->flags |= (zone & ZONES_MASK) << ZONES_PGSHIFT;
 }
 
 static inline void set_page_node(struct page *page, unsigned long node)
 {
         page->flags &= ~(NODES_MASK << NODES_PGSHIFT);
         page->flags |= (node & NODES_MASK) << NODES_PGSHIFT;
 }
 
 static inline void set_page_links(struct page *page, enum zone_type zone,
         unsigned long node, unsigned long pfn)
 {
         set_page_zone(page, zone);
         set_page_node(page, node);
 #ifdef SECTION_IN_PAGE_FLAGS
         set_page_section(page, pfn_to_section_nr(pfn));
 #endif
 }
 
 #ifdef CONFIG_MEMCG
 static inline struct mem_cgroup *page_memcg(struct page *page)
 {
         return page->mem_cgroup;
 }
 static inline struct mem_cgroup *page_memcg_rcu(struct page *page)
 {
         WARN_ON_ONCE(!rcu_read_lock_held());
         return READ_ONCE(page->mem_cgroup);
 }
 #else
 static inline struct mem_cgroup *page_memcg(struct page *page)
 {
         return NULL;
 }
 static inline struct mem_cgroup *page_memcg_rcu(struct page *page)
 {
         WARN_ON_ONCE(!rcu_read_lock_held());
         return NULL;
 }
 #endif
 
 /*
  * Some inline functions in vmstat.h depend on page_zone()
  */
 #include <linux/vmstat.h>
 
 static __always_inline void *lowmem_page_address(const struct page *page)
 {
         return page_to_virt(page);
 }
 
 #if defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL)
 #define HASHED_PAGE_VIRTUAL
 #endif
 
 #if defined(WANT_PAGE_VIRTUAL)
 static inline void *page_address(const struct page *page)
 {
         return page->virtual;
 }
 static inline void set_page_address(struct page *page, void *address)
 {
         page->virtual = address;
 }
 #define page_address_init()  do { } while(0)
 #endif
 
 #if defined(HASHED_PAGE_VIRTUAL)
 void *page_address(const struct page *page);
 void set_page_address(struct page *page, void *virtual);
 void page_address_init(void);
 #endif
 
 #if !defined(HASHED_PAGE_VIRTUAL) && !defined(WANT_PAGE_VIRTUAL)
 #define page_address(page) lowmem_page_address(page)
 #define set_page_address(page, address)  do { } while(0)
 #define page_address_init()  do { } while(0)
 #endif
 
 extern void *page_rmapping(struct page *page);
 extern struct anon_vma *page_anon_vma(struct page *page);
 extern struct address_space *page_mapping(struct page *page);
 
 extern struct address_space *__page_file_mapping(struct page *);
 
 static inline
 struct address_space *page_file_mapping(struct page *page)
 {
         if (unlikely(PageSwapCache(page)))
                 return __page_file_mapping(page);
 
         return page->mapping;
 }
 
 extern pgoff_t __page_file_index(struct page *page);
 
 /*
  * Return the pagecache index of the passed page.  Regular pagecache pages
  * use ->index whereas swapcache pages use swp_offset(->private)
  */
 static inline pgoff_t page_index(struct page *page)
 {
         if (unlikely(PageSwapCache(page)))
                 return __page_file_index(page);
         return page->index;
 }
 
 bool page_mapped(struct page *page);
 struct address_space *page_mapping(struct page *page);
 
 /*
  * Return true only if the page has been allocated with
  * ALLOC_NO_WATERMARKS and the low watermark was not
  * met implying that the system is under some pressure.
  */
 static inline bool page_is_pfmemalloc(struct page *page)
 {
         /*
          * Page index cannot be this large so this must be
          * a pfmemalloc page.
          */
         return page->index == -1UL;
 }
 
 /*
  * Only to be called by the page allocator on a freshly allocated
  * page.
  */
 static inline void set_page_pfmemalloc(struct page *page)
 {
         page->index = -1UL;
 }
 
 static inline void clear_page_pfmemalloc(struct page *page)
 {
         page->index = 0;
 }
 
 /*
  * Different kinds of faults, as returned by handle_mm_fault().
  * Used to decide whether a process gets delivered SIGBUS or
  * just gets major/minor fault counters bumped up.
  */
 
 #define VM_FAULT_OOM    0x0001
 #define VM_FAULT_SIGBUS 0x0002
 #define VM_FAULT_MAJOR  0x0004
 #define VM_FAULT_WRITE  0x0008  /* Special case for get_user_pages */
 #define VM_FAULT_HWPOISON 0x0010        /* Hit poisoned small page */
 #define VM_FAULT_HWPOISON_LARGE 0x0020  /* Hit poisoned large page. Index encoded in upper bits */
 #define VM_FAULT_SIGSEGV 0x0040
 
 #define VM_FAULT_NOPAGE 0x0100  /* ->fault installed the pte, not return page */
 #define VM_FAULT_LOCKED 0x0200  /* ->fault locked the returned page */
 #define VM_FAULT_RETRY  0x0400  /* ->fault blocked, must retry */
 #define VM_FAULT_FALLBACK 0x0800        /* huge page fault failed, fall back to small */
 #define VM_FAULT_DONE_COW   0x1000      /* ->fault has fully handled COW */
 #define VM_FAULT_NEEDDSYNC  0x2000      /* ->fault did not modify page tables
                                          * and needs fsync() to complete (for
                                          * synchronous page faults in DAX) */
 
 #define VM_FAULT_ERROR  (VM_FAULT_OOM | VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV | \
                          VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE | \
                          VM_FAULT_FALLBACK)
 
 #define VM_FAULT_RESULT_TRACE \
         { VM_FAULT_OOM,                 "OOM" }, \
         { VM_FAULT_SIGBUS,              "SIGBUS" }, \
         { VM_FAULT_MAJOR,               "MAJOR" }, \
         { VM_FAULT_WRITE,               "WRITE" }, \
         { VM_FAULT_HWPOISON,            "HWPOISON" }, \
         { VM_FAULT_HWPOISON_LARGE,      "HWPOISON_LARGE" }, \
         { VM_FAULT_SIGSEGV,             "SIGSEGV" }, \
         { VM_FAULT_NOPAGE,              "NOPAGE" }, \
         { VM_FAULT_LOCKED,              "LOCKED" }, \
         { VM_FAULT_RETRY,               "RETRY" }, \
         { VM_FAULT_FALLBACK,            "FALLBACK" }, \
         { VM_FAULT_DONE_COW,            "DONE_COW" }, \
         { VM_FAULT_NEEDDSYNC,           "NEEDDSYNC" }
 
 /* Encode hstate index for a hwpoisoned large page */
 #define VM_FAULT_SET_HINDEX(x) ((x) << 12)
 #define VM_FAULT_GET_HINDEX(x) (((x) >> 12) & 0xf)
 
 /*
  * 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)
 
 /*
  * 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);
 
 extern bool can_do_mlock(void);
 extern int user_shm_lock(size_t, struct user_struct *);
 extern void user_shm_unlock(size_t, struct user_struct *);
 
 /*
  * Parameter block passed down to zap_pte_range in exceptional cases.
  */
 struct zap_details {
         struct address_space *check_mapping;    /* Check page->mapping if set */
         pgoff_t first_index;                    /* Lowest page->index to unmap */
         pgoff_t last_index;                     /* Highest page->index to unmap */
 };
 
 struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
                              pte_t pte, bool with_public_device);
 #define vm_normal_page(vma, addr, pte) _vm_normal_page(vma, addr, pte, false)
 
 struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,
                                 pmd_t pmd);
 
 int 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);
 
 /**
  * mm_walk - callbacks for walk_page_range
  * @pud_entry: if set, called for each non-empty PUD (2nd-level) entry
  *             this handler should only handle pud_trans_huge() puds.
  *             the pmd_entry or pte_entry callbacks will be used for
  *             regular PUDs.
  * @pmd_entry: if set, called for each non-empty PMD (3rd-level) entry
  *             this handler is required to be able to handle
  *             pmd_trans_huge() pmds.  They may simply choose to
  *             split_huge_page() instead of handling it explicitly.
  * @pte_entry: if set, called for each non-empty PTE (4th-level) entry
  * @pte_hole: if set, called for each hole at all levels
  * @hugetlb_entry: if set, called for each hugetlb entry
  * @test_walk: caller specific callback function to determine whether
  *             we walk over the current vma or not. Returning 0
  *             value means "do page table walk over the current vma,"
  *             and a negative one means "abort current page table walk
  *             right now." 1 means "skip the current vma."
  * @mm:        mm_struct representing the target process of page table walk
  * @vma:       vma currently walked (NULL if walking outside vmas)
  * @private:   private data for callbacks' usage
  *
  * (see the comment on walk_page_range() for more details)
  */
 struct mm_walk {
         int (*pud_entry)(pud_t *pud, unsigned long addr,
                          unsigned long next, struct mm_walk *walk);
         int (*pmd_entry)(pmd_t *pmd, unsigned long addr,
                          unsigned long next, struct mm_walk *walk);
         int (*pte_entry)(pte_t *pte, unsigned long addr,
                          unsigned long next, struct mm_walk *walk);
         int (*pte_hole)(unsigned long addr, unsigned long next,
                         struct mm_walk *walk);
         int (*hugetlb_entry)(pte_t *pte, unsigned long hmask,
                              unsigned long addr, unsigned long next,
                              struct mm_walk *walk);
         int (*test_walk)(unsigned long addr, unsigned long next,
                         struct mm_walk *walk);
         struct mm_struct *mm;
         struct vm_area_struct *vma;
         void *private;
 };
 
 int walk_page_range(unsigned long addr, unsigned long end,
                 struct mm_walk *walk);
 int walk_page_vma(struct vm_area_struct *vma, struct mm_walk *walk);
 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 mm_struct *dst, struct mm_struct *src,
                         struct vm_area_struct *vma);
 int follow_pte_pmd(struct mm_struct *mm, unsigned long address,
                              unsigned long *start, unsigned long *end,
                              pte_t **ptepp, pmd_t **pmdpp, spinlock_t **ptlp);
 int follow_pfn(struct vm_area_struct *vma, unsigned long address,
         unsigned long *pfn);
 int follow_phys(struct vm_area_struct *vma, unsigned long address,
                 unsigned int flags, unsigned long *prot, resource_size_t *phys);
 int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
                         void *buf, int len, int write);
 
 extern void truncate_pagecache(struct inode *inode, loff_t new);
 extern void truncate_setsize(struct inode *inode, loff_t newsize);
 void pagecache_isize_extended(struct inode *inode, loff_t from, loff_t to);
 void truncate_pagecache_range(struct inode *inode, loff_t offset, loff_t end);
 int truncate_inode_page(struct address_space *mapping, struct page *page);
 int generic_error_remove_page(struct address_space *mapping, struct page *page);
 int invalidate_inode_page(struct page *page);
 
 #ifdef CONFIG_MMU
 extern int handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
                 unsigned int flags);
 extern int fixup_user_fault(struct task_struct *tsk, 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 int handle_mm_fault(struct vm_area_struct *vma,
                 unsigned long address, unsigned int flags)
 {
         /* should never happen if there's no MMU */
         BUG();
         return VM_FAULT_SIGBUS;
 }
 static inline int fixup_user_fault(struct task_struct *tsk,
                 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 task_struct *tsk, struct mm_struct *mm,
                 unsigned long addr, void *buf, int len, unsigned int gup_flags);
 
 long get_user_pages_remote(struct task_struct *tsk, 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 get_user_pages_locked(unsigned long start, unsigned long nr_pages,
                     unsigned int gup_flags, struct page **pages, int *locked);
 long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
                     struct page **pages, unsigned int gup_flags);
 #ifdef CONFIG_FS_DAX
 long get_user_pages_longterm(unsigned long start, unsigned long nr_pages,
                             unsigned int gup_flags, struct page **pages,
                             struct vm_area_struct **vmas);
 #else
 static inline long get_user_pages_longterm(unsigned long start,
                 unsigned long nr_pages, unsigned int gup_flags,
                 struct page **pages, struct vm_area_struct **vmas)
 {
         return get_user_pages(start, nr_pages, gup_flags, pages, vmas);
 }
 #endif /* CONFIG_FS_DAX */
 
 int get_user_pages_fast(unsigned long start, int nr_pages, int write,
                         struct page **pages);
 
 /* Container for pinned pfns / pages */
 struct frame_vector {
         unsigned int nr_allocated;      /* Number of frames we have space for */
         unsigned int nr_frames; /* Number of frames stored in ptrs array */
         bool got_ref;           /* Did we pin pages by getting page ref? */
         bool is_pfns;           /* Does array contain pages or pfns? */
         void *ptrs[0];          /* Array of pinned pfns / pages. Use
                                  * pfns_vector_pages() or pfns_vector_pfns()
                                  * for access */
 };
 
 struct frame_vector *frame_vector_create(unsigned int nr_frames);
 void frame_vector_destroy(struct frame_vector *vec);
 int get_vaddr_frames(unsigned long start, unsigned int nr_pfns,
                      unsigned int gup_flags, struct frame_vector *vec);
 void put_vaddr_frames(struct frame_vector *vec);
 int frame_vector_to_pages(struct frame_vector *vec);
 void frame_vector_to_pfns(struct frame_vector *vec);
 
 static inline unsigned int frame_vector_count(struct frame_vector *vec)
 {
         return vec->nr_frames;
 }
 
 static inline struct page **frame_vector_pages(struct frame_vector *vec)
 {
         if (vec->is_pfns) {
                 int err = frame_vector_to_pages(vec);
 
                 if (err)
                         return ERR_PTR(err);
         }
         return (struct page **)(vec->ptrs);
 }
 
 static inline unsigned long *frame_vector_pfns(struct frame_vector *vec)
 {
         if (!vec->is_pfns)
                 frame_vector_to_pfns(vec);
         return (unsigned long *)(vec->ptrs);
 }
 
 struct kvec;
 int get_kernel_pages(const struct kvec *iov, int nr_pages, int write,
                         struct page **pages);
 int get_kernel_page(unsigned long start, int write, struct page **pages);
 struct page *get_dump_page(unsigned long addr);
 
 extern int try_to_release_page(struct page * page, gfp_t gfp_mask);
 extern void do_invalidatepage(struct page *page, unsigned int offset,
                               unsigned int length);
 
 int __set_page_dirty_nobuffers(struct page *page);
 int __set_page_dirty_no_writeback(struct page *page);
 int redirty_page_for_writepage(struct writeback_control *wbc,
                                 struct page *page);
 void account_page_dirtied(struct page *page, struct address_space *mapping);
 void account_page_cleaned(struct page *page, struct address_space *mapping,
                           struct bdi_writeback *wb);
 int set_page_dirty(struct page *page);
 int set_page_dirty_lock(struct page *page);
 void __cancel_dirty_page(struct page *page);
 static inline void cancel_dirty_page(struct page *page)
 {
         /* Avoid atomic ops, locking, etc. when not actually needed. */
         if (PageDirty(page))
                 __cancel_dirty_page(page);
 }
 int clear_page_dirty_for_io(struct page *page);
 
 int get_cmdline(struct task_struct *task, char *buffer, int buflen);
 
 static inline bool vma_is_anonymous(struct vm_area_struct *vma)
 {
         return !vma->vm_ops;
 }
 
 #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);
 
 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);
 extern unsigned long change_protection(struct vm_area_struct *vma, unsigned long start,
                               unsigned long end, pgprot_t newprot,
                               int dirty_accountable, int prot_numa);
 extern int mprotect_fixup(struct vm_area_struct *vma,
                           struct vm_area_struct **pprev, unsigned long start,
                           unsigned long end, unsigned long newflags);
 
 /*
  * doesn't attempt to fault and will return short.
  */
 int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
                           struct page **pages);
 /*
  * 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;
 }
 
 static inline void add_mm_counter(struct mm_struct *mm, int member, long value)
 {
         atomic_long_add(value, &mm->rss_stat.count[member]);
 }
 
 static inline void inc_mm_counter(struct mm_struct *mm, int member)
 {
         atomic_long_inc(&mm->rss_stat.count[member]);
 }
 
 static inline void dec_mm_counter(struct mm_struct *mm, int member)
 {
         atomic_long_dec(&mm->rss_stat.count[member]);
 }
 
 /* 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 __HAVE_ARCH_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)
 {
         atomic_long_add(PTRS_PER_PUD * sizeof(pud_t), &mm->pgtables_bytes);
 }
 
 static inline void mm_dec_nr_puds(struct mm_struct *mm)
 {
         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)
 {
         atomic_long_add(PTRS_PER_PMD * sizeof(pmd_t), &mm->pgtables_bytes);
 }
 
 static inline void mm_dec_nr_pmds(struct mm_struct *mm)
 {
         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, unsigned long address);
 int __pte_alloc_kernel(pmd_t *pmd, unsigned long address);
 
 /*
  * The following ifdef needed to get the 4level-fixup.h header to work.
  * Remove it when 4level-fixup.h has been removed.
  */
 #if defined(CONFIG_MMU) && !defined(__ARCH_HAS_4LEVEL_HACK)
 
 #ifndef __ARCH_HAS_5LEVEL_HACK
 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);
 }
 #endif /* !__ARCH_HAS_5LEVEL_HACK */
 
 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 && !__ARCH_HAS_4LEVEL_HACK */
 
 #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;
 }
 
 /* Reset page->mapping so free_pages_check won't complain. */
 static inline void pte_lock_deinit(struct page *page)
 {
         page->mapping = NULL;
         ptlock_free(page);
 }
 
 #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 pte_lock_deinit(struct page *page) {}
 #endif /* USE_SPLIT_PTE_PTLOCKS */
 
 static inline void pgtable_init(void)
 {
         ptlock_cache_init();
         pgtable_cache_init();
 }
 
 static inline bool pgtable_page_ctor(struct page *page)
 {
         if (!ptlock_init(page))
                 return false;
         inc_zone_page_state(page, NR_PAGETABLE);
         return true;
 }
 
 static inline void pgtable_page_dtor(struct page *page)
 {
         pte_lock_deinit(page);
         dec_zone_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, address)                     \
         (unlikely(pmd_none(*(pmd))) && __pte_alloc(mm, pmd, address))
 
 #define pte_alloc_map(mm, pmd, address)                 \
         (pte_alloc(mm, pmd, address) ? NULL : pte_offset_map(pmd, address))
 
 #define pte_alloc_map_lock(mm, pmd, address, ptlp)      \
         (pte_alloc(mm, pmd, address) ?                  \
                  NULL : pte_offset_map_lock(mm, pmd, address, ptlp))
 
 #define pte_alloc_kernel(pmd, address)                  \
         ((unlikely(pmd_none(*(pmd))) && __pte_alloc_kernel(pmd, address))? \
                 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 pgtable_pmd_page_ctor(struct page *page)
 {
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
         page->pmd_huge_pte = NULL;
 #endif
         return ptlock_init(page);
 }
 
 static inline void pgtable_pmd_page_dtor(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 pgtable_pmd_page_ctor(struct page *page) { return true; }
 static inline void pgtable_pmd_page_dtor(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;
 }
 
 /*
  * 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_area_init(unsigned long * zones_size);
 extern void free_area_init_node(int nid, unsigned long * zones_size,
                 unsigned long zone_start_pfn, unsigned long *zholes_size);
 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, char *s);
 
 #ifdef  CONFIG_HIGHMEM
 /*
  * Free a highmem page into the buddy system, adjusting totalhigh_pages
  * and totalram_pages.
  */
 extern void free_highmem_page(struct page *page);
 #endif
 
 extern void adjust_managed_page_count(struct page *page, long count);
 extern void mem_init_print_info(const char *str);
 
 extern void reserve_bootmem_region(phys_addr_t start, phys_addr_t end);
 
 /* Free the reserved page into the buddy system, so it gets managed. */
 static inline void __free_reserved_page(struct page *page)
 {
         ClearPageReserved(page);
         init_page_count(page);
         __free_page(page);
 }
 
 static inline void free_reserved_page(struct page *page)
 {
         __free_reserved_page(page);
         adjust_managed_page_count(page, 1);
 }
 
 static inline void mark_page_reserved(struct page *page)
 {
         SetPageReserved(page);
         adjust_managed_page_count(page, -1);
 }
 
 /*
  * Default method to free all the __init memory into the buddy system.
  * The freed pages will be poisoned with pattern "poison" if it's within
  * range [0, UCHAR_MAX].
  * Return pages freed into the buddy system.
  */
 static inline unsigned long free_initmem_default(int poison)
 {
         extern char __init_begin[], __init_end[];
 
         return free_reserved_area(&__init_begin, &__init_end,
                                   poison, "unused kernel");
 }
 
 static inline unsigned long get_num_physpages(void)
 {
         int nid;
         unsigned long phys_pages = 0;
 
         for_each_online_node(nid)
                 phys_pages += node_present_pages(nid);
 
         return phys_pages;
 }
 
 #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
 /*
  * With CONFIG_HAVE_MEMBLOCK_NODE_MAP set, an architecture may initialise its
  * zones, allocate the backing mem_map and account for memory holes in a more
  * architecture independent manner. This is a substitute for creating the
  * zone_sizes[] and zholes_size[] arrays and passing them to
  * free_area_init_node()
  *
  * An architecture is expected to register range of page frames backed by
  * physical memory with memblock_add[_node]() before calling
  * free_area_init_nodes() passing in the PFN each zone ends at. At a basic
  * usage, an architecture is expected to do something like
  *
  * unsigned long max_zone_pfns[MAX_NR_ZONES] = {max_dma, max_normal_pfn,
  *                                                       max_highmem_pfn};
  * for_each_valid_physical_page_range()
  *      memblock_add_node(base, size, nid)
  * free_area_init_nodes(max_zone_pfns);
  *
  * free_bootmem_with_active_regions() calls free_bootmem_node() for each
  * registered physical page range.  Similarly
  * sparse_memory_present_with_active_regions() calls memory_present() for
  * each range when SPARSEMEM is enabled.
  *
  * See mm/page_alloc.c for more information on each function exposed by
  * CONFIG_HAVE_MEMBLOCK_NODE_MAP.
  */
 extern void free_area_init_nodes(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);
 extern void free_bootmem_with_active_regions(int nid,
                                                 unsigned long max_low_pfn);
 extern void sparse_memory_present_with_active_regions(int nid);
 
 #endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
 
 #if !defined(CONFIG_HAVE_MEMBLOCK_NODE_MAP) && \
     !defined(CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID)
 static inline int __early_pfn_to_nid(unsigned long pfn,
                                         struct mminit_pfnnid_cache *state)
 {
         return 0;
 }
 #else
 /* please see mm/page_alloc.c */
 extern int __meminit early_pfn_to_nid(unsigned long pfn);
 /* there is a per-arch backend function. */
 extern int __meminit __early_pfn_to_nid(unsigned long pfn,
                                         struct mminit_pfnnid_cache *state);
 #endif
 
 #ifdef CONFIG_HAVE_MEMBLOCK
 void zero_resv_unavail(void);
 #else
 static inline void zero_resv_unavail(void) {}
 #endif
 
 extern void set_dma_reserve(unsigned long new_dma_reserve);
 extern void memmap_init_zone(unsigned long, int, unsigned long, unsigned long,
                 enum memmap_context, struct vmem_altmap *);
 extern void setup_per_zone_wmarks(void);
 extern int __meminit init_per_zone_wmark_min(void);
 extern void mem_init(void);
 extern void __init mmap_init(void);
 extern void show_mem(unsigned int flags, nodemask_t *nodemask);
 extern long si_mem_available(void);
 extern void si_meminfo(struct sysinfo * val);
 extern void si_meminfo_node(struct sysinfo *val, int nid);
 #ifdef __HAVE_ARCH_RESERVED_KERNEL_PAGES
 extern unsigned long arch_reserved_kernel_pages(void);
 #endif
 
 extern __printf(3, 4)
 void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...);
 
 extern void setup_per_cpu_pageset(void);
 
 extern void zone_pcp_update(struct zone *zone);
 extern void zone_pcp_reset(struct zone *zone);
 
 /* page_alloc.c */
 extern int min_free_kbytes;
 extern int watermark_scale_factor;
 
 /* nommu.c */
 extern atomic_long_t mmap_pages_allocated;
 extern int nommu_shrink_inode_mappings(struct inode *, size_t, size_t);
 
 /* interval_tree.c */
 void vma_interval_tree_insert(struct vm_area_struct *node,
                               struct rb_root_cached *root);
 void vma_interval_tree_insert_after(struct vm_area_struct *node,
                                     struct vm_area_struct *prev,
                                     struct rb_root_cached *root);
 void vma_interval_tree_remove(struct vm_area_struct *node,
                               struct rb_root_cached *root);
 struct vm_area_struct *vma_interval_tree_iter_first(struct rb_root_cached *root,
                                 unsigned long start, unsigned long last);
 struct vm_area_struct *vma_interval_tree_iter_next(struct vm_area_struct *node,
                                 unsigned long start, unsigned long last);
 
 #define vma_interval_tree_foreach(vma, root, start, last)               \
         for (vma = vma_interval_tree_iter_first(root, start, last);     \
              vma; vma = vma_interval_tree_iter_next(vma, start, last))
 
 void anon_vma_interval_tree_insert(struct anon_vma_chain *node,
                                    struct rb_root_cached *root);
 void anon_vma_interval_tree_remove(struct anon_vma_chain *node,
                                    struct rb_root_cached *root);
 struct anon_vma_chain *
 anon_vma_interval_tree_iter_first(struct rb_root_cached *root,
                                   unsigned long start, unsigned long last);
 struct anon_vma_chain *anon_vma_interval_tree_iter_next(
         struct anon_vma_chain *node, unsigned long start, unsigned long last);
 #ifdef CONFIG_DEBUG_VM_RB
 void anon_vma_interval_tree_verify(struct anon_vma_chain *node);
 #endif
 
 #define anon_vma_interval_tree_foreach(avc, root, start, last)           \
         for (avc = anon_vma_interval_tree_iter_first(root, start, last); \
              avc; avc = anon_vma_interval_tree_iter_next(avc, start, last))
 
 /* mmap.c */
 extern int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin);
 extern int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
         unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert,
         struct vm_area_struct *expand);
 static inline int vma_adjust(struct vm_area_struct *vma, unsigned long start,
         unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert)
 {
         return __vma_adjust(vma, start, end, pgoff, insert, NULL);
 }
 extern struct vm_area_struct *vma_merge(struct mm_struct *,
         struct vm_area_struct *prev, unsigned long addr, unsigned long end,
         unsigned long vm_flags, struct anon_vma *, struct file *, pgoff_t,
         struct mempolicy *, struct vm_userfaultfd_ctx);
 extern struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *);
 extern int __split_vma(struct mm_struct *, struct vm_area_struct *,
         unsigned long addr, int new_below);
 extern int split_vma(struct mm_struct *, struct vm_area_struct *,
         unsigned long addr, int new_below);
 extern int insert_vm_struct(struct mm_struct *, struct vm_area_struct *);
 extern void __vma_link_rb(struct mm_struct *, struct vm_area_struct *,
         struct rb_node **, struct rb_node *);
 extern void unlink_file_vma(struct vm_area_struct *);
 extern struct vm_area_struct *copy_vma(struct vm_area_struct **,
         unsigned long addr, unsigned long len, pgoff_t pgoff,
         bool *need_rmap_locks);
 extern void exit_mmap(struct mm_struct *);
 
 static inline int check_data_rlimit(unsigned long rlim,
                                     unsigned long new,
                                     unsigned long start,
                                     unsigned long end_data,
                                     unsigned long start_data)
 {
         if (rlim < RLIM_INFINITY) {
                 if (((new - start) + (end_data - start_data)) > rlim)
                         return -ENOSPC;
         }
 
         return 0;
 }
 
 extern int mm_take_all_locks(struct mm_struct *mm);
 extern void mm_drop_all_locks(struct mm_struct *mm);
 
 extern void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file);
 extern struct file *get_mm_exe_file(struct mm_struct *mm);
 extern struct file *get_task_exe_file(struct task_struct *task);
 
 extern bool may_expand_vm(struct mm_struct *, vm_flags_t, unsigned long npages);
 extern void vm_stat_account(struct mm_struct *, vm_flags_t, long npages);
 
 extern bool vma_is_special_mapping(const struct vm_area_struct *vma,
                                    const struct vm_special_mapping *sm);
 extern struct vm_area_struct *_install_special_mapping(struct mm_struct *mm,
                                    unsigned long addr, unsigned long len,
                                    unsigned long flags,
                                    const struct vm_special_mapping *spec);
 /* This is an obsolete alternative to _install_special_mapping. */
 extern int install_special_mapping(struct mm_struct *mm,
                                    unsigned long addr, unsigned long len,
                                    unsigned long flags, struct page **pages);
 
 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,
         vm_flags_t vm_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);
 
 static inline unsigned long
 do_mmap_pgoff(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)
 {
         return do_mmap(file, addr, len, prot, flags, 0, pgoff, populate, uf);
 }
 
 #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 unmapped_area(struct vm_unmapped_area_info *info);
 extern unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info);
 
 /*
  * Search for an unmapped address range.
  *
  * We are looking for a range that:
  * - does not intersect with any VMA;
  * - is contained within the [low_limit, high_limit) interval;
  * - is at least the desired size.
  * - satisfies (begin_addr & align_mask) == (align_offset & align_mask)
  */
 static inline unsigned long
 vm_unmapped_area(struct vm_unmapped_area_info *info)
 {
         if (info->flags & VM_UNMAPPED_AREA_TOPDOWN)
                 return unmapped_area_topdown(info);
         else
                 return unmapped_area(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 int filemap_fault(struct vm_fault *vmf);
 extern void filemap_map_pages(struct vm_fault *vmf,
                 pgoff_t start_pgoff, pgoff_t end_pgoff);
 extern int filemap_page_mkwrite(struct vm_fault *vmf);
 
 /* mm/page-writeback.c */
 int __must_check write_one_page(struct page *page);
 void task_dirty_inc(struct task_struct *tsk);
 
 /* readahead.c */
 #define VM_MAX_READAHEAD        128     /* kbytes */
 #define VM_MIN_READAHEAD        16      /* kbytes (includes current page) */
 
 int force_page_cache_readahead(struct address_space *mapping, struct file *filp,
                         pgoff_t offset, unsigned long nr_to_read);
 
 void page_cache_sync_readahead(struct address_space *mapping,
                                struct file_ra_state *ra,
                                struct file *filp,
                                pgoff_t offset,
                                unsigned long size);
 
 void page_cache_async_readahead(struct address_space *mapping,
                                 struct file_ra_state *ra,
                                 struct file *filp,
                                 struct page *pg,
                                 pgoff_t offset,
                                 unsigned long size);
 
 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 to grow downwards at some places */
 extern int expand_downwards(struct vm_area_struct *vma,
                 unsigned long address);
 #if VM_GROWSUP
 extern int expand_upwards(struct vm_area_struct *vma, unsigned long address);
 #else
   #define expand_upwards(vma, address) (0)
 #endif
 
 /* Look up the first VMA which satisfies  addr < vm_end,  NULL if none. */
 extern struct vm_area_struct * find_vma(struct mm_struct * mm, unsigned long addr);
 extern struct vm_area_struct * find_vma_prev(struct mm_struct * mm, unsigned long addr,
                                              struct vm_area_struct **pprev);
 
 /* Look up the first VMA which intersects the interval start_addr..end_addr-1,
    NULL if none.  Assume start_addr < end_addr. */
 static inline struct vm_area_struct * find_vma_intersection(struct mm_struct * mm, unsigned long start_addr, unsigned long end_addr)
 {
         struct vm_area_struct * vma = find_vma(mm,start_addr);
 
         if (vma && end_addr <= vma->vm_start)
                 vma = NULL;
         return vma;
 }
 
 static inline unsigned long vm_start_gap(struct vm_area_struct *vma)
 {
         unsigned long vm_start = vma->vm_start;
 
         if (vma->vm_flags & VM_GROWSDOWN) {
                 vm_start -= stack_guard_gap;
                 if (vm_start > vma->vm_start)
                         vm_start = 0;
         }
         return vm_start;
 }
 
 static inline unsigned long vm_end_gap(struct vm_area_struct *vma)
 {
         unsigned long vm_end = vma->vm_end;
 
         if (vma->vm_flags & VM_GROWSUP) {
                 vm_end += stack_guard_gap;
                 if (vm_end < vma->vm_end)
                         vm_end = -PAGE_SIZE;
         }
         return vm_end;
 }
 
 static inline unsigned long vma_pages(struct vm_area_struct *vma)
 {
         return (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
 }
 
 /* Look up the first VMA which exactly match the interval vm_start ... vm_end */
 static inline struct vm_area_struct *find_exact_vma(struct mm_struct *mm,
                                 unsigned long vm_start, unsigned long vm_end)
 {
         struct vm_area_struct *vma = find_vma(mm, vm_start);
 
         if (vma && (vma->vm_start != vm_start || vma->vm_end != vm_end))
                 vma = NULL;
 
         return vma;
 }
 
 #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
 
 #ifdef CONFIG_NUMA_BALANCING
 unsigned long change_prot_numa(struct vm_area_struct *vma,
                         unsigned long start, unsigned long end);
 #endif
 
 struct vm_area_struct *find_extend_vma(struct mm_struct *, unsigned long addr);
 int remap_pfn_range(struct vm_area_struct *, unsigned long addr,
                         unsigned long pfn, unsigned long size, pgprot_t);
 int vm_insert_page(struct vm_area_struct *, unsigned long addr, struct page *);
 int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
                         unsigned long pfn);
 int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
                         unsigned long pfn, pgprot_t pgprot);
 int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
                         pfn_t pfn);
 int vm_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);
 
 
 struct page *follow_page_mask(struct vm_area_struct *vma,
                               unsigned long address, unsigned int foll_flags,
                               unsigned int *page_mask);
 
 static inline struct page *follow_page(struct vm_area_struct *vma,
                 unsigned long address, unsigned int foll_flags)
 {
         unsigned int unused_page_mask;
         return follow_page_mask(vma, address, foll_flags, &unused_page_mask);
 }
 
 #define FOLL_WRITE      0x01    /* check pte is writable */
 #define FOLL_TOUCH      0x02    /* mark page accessed */
 #define FOLL_GET        0x04    /* do get_page on page */
 #define FOLL_DUMP       0x08    /* give error on hole if it would be zero */
 #define FOLL_FORCE      0x10    /* get_user_pages read/write w/o permission */
 #define FOLL_NOWAIT     0x20    /* if a disk transfer is needed, start the IO
                                  * and return without waiting upon it */
 #define FOLL_POPULATE   0x40    /* fault in page */
 #define FOLL_SPLIT      0x80    /* don't return transhuge pages, split them */
 #define FOLL_HWPOISON   0x100   /* check page is hwpoisoned */
 #define FOLL_NUMA       0x200   /* force NUMA hinting page fault */
 #define FOLL_MIGRATION  0x400   /* wait for page to replace migration entry */
 #define FOLL_TRIED      0x800   /* a retry, previous pass started an IO */
 #define FOLL_MLOCK      0x1000  /* lock present pages */
 #define FOLL_REMOTE     0x2000  /* we are working on non-current tsk/mm */
 #define FOLL_COW        0x4000  /* internal GUP flag */
 #define FOLL_ANON       0x8000  /* don't do file mappings */
 
 static inline int vm_fault_to_errno(int vm_fault, int foll_flags)
 {
         if (vm_fault & VM_FAULT_OOM)
                 return -ENOMEM;
         if (vm_fault & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
                 return (foll_flags & FOLL_HWPOISON) ? -EHWPOISON : -EFAULT;
         if (vm_fault & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV))
                 return -EFAULT;
         return 0;
 }
 
 typedef int (*pte_fn_t)(pte_t *pte, pgtable_t token, 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);
 
 
 #ifdef CONFIG_PAGE_POISONING
 extern bool page_poisoning_enabled(void);
 extern void kernel_poison_pages(struct page *page, int numpages, int enable);
 extern bool page_is_poisoned(struct page *page);
 #else
 static inline bool page_poisoning_enabled(void) { return false; }
 static inline void kernel_poison_pages(struct page *page, int numpages,
                                         int enable) { }
 static inline bool page_is_poisoned(struct page *page) { return false; }
 #endif
 
 #ifdef CONFIG_DEBUG_PAGEALLOC
 extern bool _debug_pagealloc_enabled;
 extern void __kernel_map_pages(struct page *page, int numpages, int enable);
 
 static inline bool debug_pagealloc_enabled(void)
 {
         return _debug_pagealloc_enabled;
 }
 
 static inline void
 kernel_map_pages(struct page *page, int numpages, int enable)
 {
         if (!debug_pagealloc_enabled())
                 return;
 
         __kernel_map_pages(page, numpages, enable);
 }
 #ifdef CONFIG_HIBERNATION
 extern bool kernel_page_present(struct page *page);
 #endif  /* CONFIG_HIBERNATION */
 #else   /* CONFIG_DEBUG_PAGEALLOC */
 static inline void
 kernel_map_pages(struct page *page, int numpages, int enable) {}
 #ifdef CONFIG_HIBERNATION
 static inline bool kernel_page_present(struct page *page) { return true; }
 #endif  /* CONFIG_HIBERNATION */
 static inline bool debug_pagealloc_enabled(void)
 {
         return false;
 }
 #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 __user *, size_t *, loff_t *);
 #endif
 
 void drop_slab(void);
 void drop_slab_node(int nid);
 
 #ifndef CONFIG_MMU
 #define randomize_va_space 0
 #else
 extern int randomize_va_space;
 #endif
 
 const char * arch_vma_name(struct vm_area_struct *vma);
 void print_vma_addr(char *prefix, unsigned long rip);
 
 void sparse_mem_maps_populate_node(struct page **map_map,
                                    unsigned long pnum_begin,
                                    unsigned long pnum_end,
                                    unsigned long map_count,
                                    int nodeid);
 
 struct page *sparse_mem_map_populate(unsigned long pnum, int nid,
                 struct vmem_altmap *altmap);
 pgd_t *vmemmap_pgd_populate(unsigned long addr, int node);
 p4d_t *vmemmap_p4d_populate(pgd_t *pgd, unsigned long addr, int node);
 pud_t *vmemmap_pud_populate(p4d_t *p4d, unsigned long addr, int node);
 pmd_t *vmemmap_pmd_populate(pud_t *pud, unsigned long addr, int node);
 pte_t *vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, int node);
 void *vmemmap_alloc_block(unsigned long size, int node);
 struct vmem_altmap;
 void *vmemmap_alloc_block_buf(unsigned long size, int node);
 void *altmap_alloc_block_buf(unsigned long size, 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);
 int vmemmap_populate(unsigned long start, unsigned long end, int node,
                 struct vmem_altmap *altmap);
 void vmemmap_populate_print_last(void);
 #ifdef CONFIG_MEMORY_HOTPLUG
 void vmemmap_free(unsigned long start, unsigned long end,
                 struct vmem_altmap *altmap);
 #endif
 void register_page_bootmem_memmap(unsigned long section_nr, struct page *map,
                                   unsigned long nr_pages);
 
 enum mf_flags {
         MF_COUNT_INCREASED = 1 << 0,
         MF_ACTION_REQUIRED = 1 << 1,
         MF_MUST_KILL = 1 << 2,
         MF_SOFT_OFFLINE = 1 << 3,
 };
 extern int memory_failure(unsigned long pfn, int flags);
 extern void memory_failure_queue(unsigned long pfn, int flags);
 extern int unpoison_memory(unsigned long pfn);
 extern int get_hwpoison_page(struct page *page);
 #define put_hwpoison_page(page) put_page(page)
 extern int sysctl_memory_failure_early_kill;
 extern int sysctl_memory_failure_recovery;
 extern void shake_page(struct page *p, int access);
 extern atomic_long_t num_poisoned_pages;
 extern int soft_offline_page(struct page *page, int flags);
 
 
 /*
  * Error handlers for various types of pages.
  */
 enum mf_result {
         MF_IGNORED,     /* Error: cannot be handled */
         MF_FAILED,      /* Error: handling failed */
         MF_DELAYED,     /* Will be handled later */
         MF_RECOVERED,   /* Successfully recovered */
 };
 
 enum mf_action_page_type {
         MF_MSG_KERNEL,
         MF_MSG_KERNEL_HIGH_ORDER,
         MF_MSG_SLAB,
         MF_MSG_DIFFERENT_COMPOUND,
         MF_MSG_POISONED_HUGE,
         MF_MSG_HUGE,
         MF_MSG_FREE_HUGE,
         MF_MSG_NON_PMD_HUGE,
         MF_MSG_UNMAP_FAILED,
         MF_MSG_DIRTY_SWAPCACHE,
         MF_MSG_CLEAN_SWAPCACHE,
         MF_MSG_DIRTY_MLOCKED_LRU,
         MF_MSG_CLEAN_MLOCKED_LRU,
         MF_MSG_DIRTY_UNEVICTABLE_LRU,
         MF_MSG_CLEAN_UNEVICTABLE_LRU,
         MF_MSG_DIRTY_LRU,
         MF_MSG_CLEAN_LRU,
         MF_MSG_TRUNCATED_LRU,
         MF_MSG_BUDDY,
         MF_MSG_BUDDY_2ND,
         MF_MSG_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, 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);
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */
 
 extern struct page_ext_operations debug_guardpage_ops;
 
 #ifdef CONFIG_DEBUG_PAGEALLOC
 extern unsigned int _debug_guardpage_minorder;
 extern bool _debug_guardpage_enabled;
 
 static inline unsigned int debug_guardpage_minorder(void)
 {
         return _debug_guardpage_minorder;
 }
 
 static inline bool debug_guardpage_enabled(void)
 {
         return _debug_guardpage_enabled;
 }
 
 static inline bool page_is_guard(struct page *page)
 {
         struct page_ext *page_ext;
 
         if (!debug_guardpage_enabled())
                 return false;
 
         page_ext = lookup_page_ext(page);
         if (unlikely(!page_ext))
                 return false;
 
         return test_bit(PAGE_EXT_DEBUG_GUARD, &page_ext->flags);
 }
 #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
 
 #endif /* __KERNEL__ */
 #endif /* _LINUX_MM_H */
 

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