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 /* SPDX-License-Identifier: GPL-2.0 */
 #ifndef _LINUX_MM_TYPES_H
 #define _LINUX_MM_TYPES_H
 
 #include <linux/mm_types_task.h>
 
 #include <linux/auxvec.h>
 #include <linux/kref.h>
 #include <linux/list.h>
 #include <linux/spinlock.h>
 #include <linux/rbtree.h>
 #include <linux/rwsem.h>
 #include <linux/completion.h>
 #include <linux/cpumask.h>
 #include <linux/uprobes.h>
 #include <linux/rcupdate.h>
 #include <linux/page-flags-layout.h>
 #include <linux/workqueue.h>
 #include <linux/seqlock.h>
 
 #include <asm/mmu.h>
 
 #ifndef AT_VECTOR_SIZE_ARCH
 #define AT_VECTOR_SIZE_ARCH 0
 #endif
 #define AT_VECTOR_SIZE (2*(AT_VECTOR_SIZE_ARCH + AT_VECTOR_SIZE_BASE + 1))
 
 #define INIT_PASID  0
 
 struct address_space;
 struct mem_cgroup;
 
 /*
  * Each physical page in the system has a struct page associated with
  * it to keep track of whatever it is we are using the page for at the
  * moment. Note that we have no way to track which tasks are using
  * a page, though if it is a pagecache page, rmap structures can tell us
  * who is mapping it.
  *
  * If you allocate the page using alloc_pages(), you can use some of the
  * space in struct page for your own purposes.  The five words in the main
  * union are available, except for bit 0 of the first word which must be
  * kept clear.  Many users use this word to store a pointer to an object
  * which is guaranteed to be aligned.  If you use the same storage as
  * page->mapping, you must restore it to NULL before freeing the page.
  *
  * If your page will not be mapped to userspace, you can also use the four
  * bytes in the mapcount union, but you must call page_mapcount_reset()
  * before freeing it.
  *
  * If you want to use the refcount field, it must be used in such a way
  * that other CPUs temporarily incrementing and then decrementing the
  * refcount does not cause problems.  On receiving the page from
  * alloc_pages(), the refcount will be positive.
  *
  * If you allocate pages of order > 0, you can use some of the fields
  * in each subpage, but you may need to restore some of their values
  * afterwards.
  *
  * SLUB uses cmpxchg_double() to atomically update its freelist and counters.
  * That requires that freelist & counters in struct slab be adjacent and
  * double-word aligned. Because struct slab currently just reinterprets the
  * bits of struct page, we align all struct pages to double-word boundaries,
  * and ensure that 'freelist' is aligned within struct slab.
  */
 #ifdef CONFIG_HAVE_ALIGNED_STRUCT_PAGE
 #define _struct_page_alignment  __aligned(2 * sizeof(unsigned long))
 #else
 #define _struct_page_alignment
 #endif
 
 struct page {
     unsigned long flags;        /* Atomic flags, some possibly
                      * updated asynchronously */
     /*
      * Five words (20/40 bytes) are available in this union.
      * WARNING: bit 0 of the first word is used for PageTail(). That
      * means the other users of this union MUST NOT use the bit to
      * avoid collision and false-positive PageTail().
      */
     union {
         struct {    /* Page cache and anonymous pages */
             /**
              * @lru: Pageout list, eg. active_list protected by
              * lruvec->lru_lock.  Sometimes used as a generic list
              * by the page owner.
              */
             union {
                 struct list_head lru;
 
                 /* Or, for the Unevictable "LRU list" slot */
                 struct {
                     /* Always even, to negate PageTail */
                     void *__filler;
                     /* Count page's or folio's mlocks */
                     unsigned int mlock_count;
                 };
 
                 /* Or, free page */
                 struct list_head buddy_list;
                 struct list_head pcp_list;
             };
             /* See page-flags.h for PAGE_MAPPING_FLAGS */
             struct address_space *mapping;
             pgoff_t index;      /* Our offset within mapping. */
             /**
              * @private: Mapping-private opaque data.
              * Usually used for buffer_heads if PagePrivate.
              * Used for swp_entry_t if PageSwapCache.
              * Indicates order in the buddy system if PageBuddy.
              */
             unsigned long private;
         };
         struct {    /* page_pool used by netstack */
             /**
              * @pp_magic: magic value to avoid recycling non
              * page_pool allocated pages.
              */
             unsigned long pp_magic;
             struct page_pool *pp;
             unsigned long _pp_mapping_pad;
             unsigned long dma_addr;
             union {
                 /**
                  * dma_addr_upper: might require a 64-bit
                  * value on 32-bit architectures.
                  */
                 unsigned long dma_addr_upper;
                 /**
                  * For frag page support, not supported in
                  * 32-bit architectures with 64-bit DMA.
                  */
                 atomic_long_t pp_frag_count;
             };
         };
         struct {    /* Tail pages of compound page */
             unsigned long compound_head;    /* Bit zero is set */
 
             /* First tail page only */
             unsigned char compound_dtor;
             unsigned char compound_order;
             atomic_t compound_mapcount;
             atomic_t compound_pincount;
 #ifdef CONFIG_64BIT
             unsigned int compound_nr; /* 1 << compound_order */
 #endif
         };
         struct {    /* Second tail page of compound page */
             unsigned long _compound_pad_1;  /* compound_head */
             unsigned long _compound_pad_2;
             /* For both global and memcg */
             struct list_head deferred_list;
         };
         struct {    /* Page table pages */
             unsigned long _pt_pad_1;    /* compound_head */
             pgtable_t pmd_huge_pte; /* protected by page->ptl */
             unsigned long _pt_pad_2;    /* mapping */
             union {
                 struct mm_struct *pt_mm; /* x86 pgds only */
                 atomic_t pt_frag_refcount; /* powerpc */
             };
 #if ALLOC_SPLIT_PTLOCKS
             spinlock_t *ptl;
 #else
             spinlock_t ptl;
 #endif
         };
         struct {    /* ZONE_DEVICE pages */
             /** @pgmap: Points to the hosting device page map. */
             struct dev_pagemap *pgmap;
             void *zone_device_data;
             /*
              * ZONE_DEVICE private pages are counted as being
              * mapped so the next 3 words hold the mapping, index,
              * and private fields from the source anonymous or
              * page cache page while the page is migrated to device
              * private memory.
              * ZONE_DEVICE MEMORY_DEVICE_FS_DAX pages also
              * use the mapping, index, and private fields when
              * pmem backed DAX files are mapped.
              */
         };
 
         /** @rcu_head: You can use this to free a page by RCU. */
         struct rcu_head rcu_head;
     };
 
     union {     /* This union is 4 bytes in size. */
         /*
          * If the page can be mapped to userspace, encodes the number
          * of times this page is referenced by a page table.
          */
         atomic_t _mapcount;
 
         /*
          * If the page is neither PageSlab nor mappable to userspace,
          * the value stored here may help determine what this page
          * is used for.  See page-flags.h for a list of page types
          * which are currently stored here.
          */
         unsigned int page_type;
     };
 
     /* Usage count. *DO NOT USE DIRECTLY*. See page_ref.h */
     atomic_t _refcount;
 
 #ifdef CONFIG_MEMCG
     unsigned long memcg_data;
 #endif
 
     /*
      * On machines where all RAM is mapped into kernel address space,
      * we can simply calculate the virtual address. On machines with
      * highmem some memory is mapped into kernel virtual memory
      * dynamically, so we need a place to store that address.
      * Note that this field could be 16 bits on x86 ... ;)
      *
      * Architectures with slow multiplication can define
      * WANT_PAGE_VIRTUAL in asm/page.h
      */
 #if defined(WANT_PAGE_VIRTUAL)
     void *virtual;          /* Kernel virtual address (NULL if
                        not kmapped, ie. highmem) */
 #endif /* WANT_PAGE_VIRTUAL */
 
 #ifdef LAST_CPUPID_NOT_IN_PAGE_FLAGS
     int _last_cpupid;
 #endif
 } _struct_page_alignment;
 
 /**
  * struct folio - Represents a contiguous set of bytes.
  * @flags: Identical to the page flags.
  * @lru: Least Recently Used list; tracks how recently this folio was used.
  * @mlock_count: Number of times this folio has been pinned by mlock().
  * @mapping: The file this page belongs to, or refers to the anon_vma for
  *    anonymous memory.
  * @index: Offset within the file, in units of pages.  For anonymous memory,
  *    this is the index from the beginning of the mmap.
  * @private: Filesystem per-folio data (see folio_attach_private()).
  *    Used for swp_entry_t if folio_test_swapcache().
  * @_mapcount: Do not access this member directly.  Use folio_mapcount() to
  *    find out how many times this folio is mapped by userspace.
  * @_refcount: Do not access this member directly.  Use folio_ref_count()
  *    to find how many references there are to this folio.
  * @memcg_data: Memory Control Group data.
  *
  * A folio is a physically, virtually and logically contiguous set
  * of bytes.  It is a power-of-two in size, and it is aligned to that
  * same power-of-two.  It is at least as large as %PAGE_SIZE.  If it is
  * in the page cache, it is at a file offset which is a multiple of that
  * power-of-two.  It may be mapped into userspace at an address which is
  * at an arbitrary page offset, but its kernel virtual address is aligned
  * to its size.
  */
 struct folio {
     /* private: don't document the anon union */
     union {
         struct {
     /* public: */
             unsigned long flags;
             union {
                 struct list_head lru;
     /* private: avoid cluttering the output */
                 struct {
                     void *__filler;
     /* public: */
                     unsigned int mlock_count;
     /* private: */
                 };
     /* public: */
             };
             struct address_space *mapping;
             pgoff_t index;
             void *private;
             atomic_t _mapcount;
             atomic_t _refcount;
 #ifdef CONFIG_MEMCG
             unsigned long memcg_data;
 #endif
     /* private: the union with struct page is transitional */
         };
         struct page page;
     };
 };
 
 static_assert(sizeof(struct page) == sizeof(struct folio));
 #define FOLIO_MATCH(pg, fl)                     \
     static_assert(offsetof(struct page, pg) == offsetof(struct folio, fl))
 FOLIO_MATCH(flags, flags);
 FOLIO_MATCH(lru, lru);
 FOLIO_MATCH(mapping, mapping);
 FOLIO_MATCH(compound_head, lru);
 FOLIO_MATCH(index, index);
 FOLIO_MATCH(private, private);
 FOLIO_MATCH(_mapcount, _mapcount);
 FOLIO_MATCH(_refcount, _refcount);
 #ifdef CONFIG_MEMCG
 FOLIO_MATCH(memcg_data, memcg_data);
 #endif
 #undef FOLIO_MATCH
 
 static inline atomic_t *folio_mapcount_ptr(struct folio *folio)
 {
     struct page *tail = &folio->page + 1;
     return &tail->compound_mapcount;
 }
 
 static inline atomic_t *compound_mapcount_ptr(struct page *page)
 {
     return &page[1].compound_mapcount;
 }
 
 static inline atomic_t *compound_pincount_ptr(struct page *page)
 {
     return &page[1].compound_pincount;
 }
 
 /*
  * Used for sizing the vmemmap region on some architectures
  */
 #define STRUCT_PAGE_MAX_SHIFT   (order_base_2(sizeof(struct page)))
 
 #define PAGE_FRAG_CACHE_MAX_SIZE    __ALIGN_MASK(32768, ~PAGE_MASK)
 #define PAGE_FRAG_CACHE_MAX_ORDER   get_order(PAGE_FRAG_CACHE_MAX_SIZE)
 
 /*
  * page_private can be used on tail pages.  However, PagePrivate is only
  * checked by the VM on the head page.  So page_private on the tail pages
  * should be used for data that's ancillary to the head page (eg attaching
  * buffer heads to tail pages after attaching buffer heads to the head page)
  */
 #define page_private(page)      ((page)->private)
 
 static inline void set_page_private(struct page *page, unsigned long private)
 {
     page->private = private;
 }
 
 static inline void *folio_get_private(struct folio *folio)
 {
     return folio->private;
 }
 
 struct page_frag_cache {
     void * va;
 #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
     __u16 offset;
     __u16 size;
 #else
     __u32 offset;
 #endif
     /* we maintain a pagecount bias, so that we dont dirty cache line
      * containing page->_refcount every time we allocate a fragment.
      */
     unsigned int        pagecnt_bias;
     bool pfmemalloc;
 };
 
 typedef unsigned long vm_flags_t;
 
 /*
  * A region containing a mapping of a non-memory backed file under NOMMU
  * conditions.  These are held in a global tree and are pinned by the VMAs that
  * map parts of them.
  */
 struct vm_region {
     struct rb_node  vm_rb;      /* link in global region tree */
     vm_flags_t  vm_flags;   /* VMA vm_flags */
     unsigned long   vm_start;   /* start address of region */
     unsigned long   vm_end;     /* region initialised to here */
     unsigned long   vm_top;     /* region allocated to here */
     unsigned long   vm_pgoff;   /* the offset in vm_file corresponding to vm_start */
     struct file *vm_file;   /* the backing file or NULL */
 
     int     vm_usage;   /* region usage count (access under nommu_region_sem) */
     bool        vm_icache_flushed : 1; /* true if the icache has been flushed for
                         * this region */
 };
 
 #ifdef CONFIG_USERFAULTFD
 #define NULL_VM_UFFD_CTX ((struct vm_userfaultfd_ctx) { NULL, })
 struct vm_userfaultfd_ctx {
     struct userfaultfd_ctx *ctx;
 };
 #else /* CONFIG_USERFAULTFD */
 #define NULL_VM_UFFD_CTX ((struct vm_userfaultfd_ctx) {})
 struct vm_userfaultfd_ctx {};
 #endif /* CONFIG_USERFAULTFD */
 
 struct anon_vma_name {
     struct kref kref;
     /* The name needs to be at the end because it is dynamically sized. */
     char name[];
 };
 
 /*
  * This struct describes a virtual memory area. There is one of these
  * per VM-area/task. A VM area is any part of the process virtual memory
  * space that has a special rule for the page-fault handlers (ie a shared
  * library, the executable area etc).
  */
 struct vm_area_struct {
     /* The first cache line has the info for VMA tree walking. */
 
     unsigned long vm_start;     /* Our start address within vm_mm. */
     unsigned long vm_end;       /* The first byte after our end address
                        within vm_mm. */
 
     /* linked list of VM areas per task, sorted by address */
     struct vm_area_struct *vm_next, *vm_prev;
 
     struct rb_node vm_rb;
 
     /*
      * Largest free memory gap in bytes to the left of this VMA.
      * Either between this VMA and vma->vm_prev, or between one of the
      * VMAs below us in the VMA rbtree and its ->vm_prev. This helps
      * get_unmapped_area find a free area of the right size.
      */
     unsigned long rb_subtree_gap;
 
     /* Second cache line starts here. */
 
     struct mm_struct *vm_mm;    /* The address space we belong to. */
 
     /*
      * Access permissions of this VMA.
      * See vmf_insert_mixed_prot() for discussion.
      */
     pgprot_t vm_page_prot;
     unsigned long vm_flags;     /* Flags, see mm.h. */
 
     /*
      * For areas with an address space and backing store,
      * linkage into the address_space->i_mmap interval tree.
      *
      * For private anonymous mappings, a pointer to a null terminated string
      * containing the name given to the vma, or NULL if unnamed.
      */
 
     union {
         struct {
             struct rb_node rb;
             unsigned long rb_subtree_last;
         } shared;
         /*
          * Serialized by mmap_sem. Never use directly because it is
          * valid only when vm_file is NULL. Use anon_vma_name instead.
          */
         struct anon_vma_name *anon_name;
     };
 
     /*
      * A file's MAP_PRIVATE vma can be in both i_mmap tree and anon_vma
      * list, after a COW of one of the file pages.  A MAP_SHARED vma
      * can only be in the i_mmap tree.  An anonymous MAP_PRIVATE, stack
      * or brk vma (with NULL file) can only be in an anon_vma list.
      */
     struct list_head anon_vma_chain; /* Serialized by mmap_lock &
                       * page_table_lock */
     struct anon_vma *anon_vma;  /* Serialized by page_table_lock */
 
     /* Function pointers to deal with this struct. */
     const struct vm_operations_struct *vm_ops;
 
     /* Information about our backing store: */
     unsigned long vm_pgoff;     /* Offset (within vm_file) in PAGE_SIZE
                        units */
     struct file * vm_file;      /* File we map to (can be NULL). */
     void * vm_private_data;     /* was vm_pte (shared mem) */
 
 #ifdef CONFIG_SWAP
     atomic_long_t swap_readahead_info;
 #endif
 #ifndef CONFIG_MMU
     struct vm_region *vm_region;    /* NOMMU mapping region */
 #endif
 #ifdef CONFIG_NUMA
     struct mempolicy *vm_policy;    /* NUMA policy for the VMA */
 #endif
     struct vm_userfaultfd_ctx vm_userfaultfd_ctx;
 } __randomize_layout;
 
 struct kioctx_table;
 struct mm_struct {
     struct {
         struct vm_area_struct *mmap;        /* list of VMAs */
         struct rb_root mm_rb;
         u64 vmacache_seqnum;                   /* per-thread vmacache */
 #ifdef CONFIG_MMU
         unsigned long (*get_unmapped_area) (struct file *filp,
                 unsigned long addr, unsigned long len,
                 unsigned long pgoff, unsigned long flags);
 #endif
         unsigned long mmap_base;    /* base of mmap area */
         unsigned long mmap_legacy_base; /* base of mmap area in bottom-up allocations */
 #ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
         /* Base addresses for compatible mmap() */
         unsigned long mmap_compat_base;
         unsigned long mmap_compat_legacy_base;
 #endif
         unsigned long task_size;    /* size of task vm space */
         unsigned long highest_vm_end;   /* highest vma end address */
         pgd_t * pgd;
 
 #ifdef CONFIG_MEMBARRIER
         /**
          * @membarrier_state: Flags controlling membarrier behavior.
          *
          * This field is close to @pgd to hopefully fit in the same
          * cache-line, which needs to be touched by switch_mm().
          */
         atomic_t membarrier_state;
 #endif
 
         /**
          * @mm_users: The number of users including userspace.
          *
          * Use mmget()/mmget_not_zero()/mmput() to modify. When this
          * drops to 0 (i.e. when the task exits and there are no other
          * temporary reference holders), we also release a reference on
          * @mm_count (which may then free the &struct mm_struct if
          * @mm_count also drops to 0).
          */
         atomic_t mm_users;
 
         /**
          * @mm_count: The number of references to &struct mm_struct
          * (@mm_users count as 1).
          *
          * Use mmgrab()/mmdrop() to modify. When this drops to 0, the
          * &struct mm_struct is freed.
          */
         atomic_t mm_count;
 
 #ifdef CONFIG_MMU
         atomic_long_t pgtables_bytes;   /* PTE page table pages */
 #endif
         int map_count;          /* number of VMAs */
 
         spinlock_t page_table_lock; /* Protects page tables and some
                          * counters
                          */
         /*
          * With some kernel config, the current mmap_lock's offset
          * inside 'mm_struct' is at 0x120, which is very optimal, as
          * its two hot fields 'count' and 'owner' sit in 2 different
          * cachelines,  and when mmap_lock is highly contended, both
          * of the 2 fields will be accessed frequently, current layout
          * will help to reduce cache bouncing.
          *
          * So please be careful with adding new fields before
          * mmap_lock, which can easily push the 2 fields into one
          * cacheline.
          */
         struct rw_semaphore mmap_lock;
 
         struct list_head mmlist; /* List of maybe swapped mm's. These
                       * are globally strung together off
                       * init_mm.mmlist, and are protected
                       * by mmlist_lock
                       */
 
 
         unsigned long hiwater_rss; /* High-watermark of RSS usage */
         unsigned long hiwater_vm;  /* High-water virtual memory usage */
 
         unsigned long total_vm;    /* Total pages mapped */
         unsigned long locked_vm;   /* Pages that have PG_mlocked set */
         atomic64_t    pinned_vm;   /* Refcount permanently increased */
         unsigned long data_vm;     /* VM_WRITE & ~VM_SHARED & ~VM_STACK */
         unsigned long exec_vm;     /* VM_EXEC & ~VM_WRITE & ~VM_STACK */
         unsigned long stack_vm;    /* VM_STACK */
         unsigned long def_flags;
 
         /**
          * @write_protect_seq: Locked when any thread is write
          * protecting pages mapped by this mm to enforce a later COW,
          * for instance during page table copying for fork().
          */
         seqcount_t write_protect_seq;
 
         spinlock_t arg_lock; /* protect the below fields */
 
         unsigned long start_code, end_code, start_data, end_data;
         unsigned long start_brk, brk, start_stack;
         unsigned long arg_start, arg_end, env_start, env_end;
 
         unsigned long saved_auxv[AT_VECTOR_SIZE]; /* for /proc/PID/auxv */
 
         /*
          * Special counters, in some configurations protected by the
          * page_table_lock, in other configurations by being atomic.
          */
         struct mm_rss_stat rss_stat;
 
         struct linux_binfmt *binfmt;
 
         /* Architecture-specific MM context */
         mm_context_t context;
 
         unsigned long flags; /* Must use atomic bitops to access */
 
 #ifdef CONFIG_AIO
         spinlock_t          ioctx_lock;
         struct kioctx_table __rcu   *ioctx_table;
 #endif
 #ifdef CONFIG_MEMCG
         /*
          * "owner" points to a task that is regarded as the canonical
          * user/owner of this mm. All of the following must be true in
          * order for it to be changed:
          *
          * current == mm->owner
          * current->mm != mm
          * new_owner->mm == mm
          * new_owner->alloc_lock is held
          */
         struct task_struct __rcu *owner;
 #endif
         struct user_namespace *user_ns;
 
         /* store ref to file /proc/<pid>/exe symlink points to */
         struct file __rcu *exe_file;
 #ifdef CONFIG_MMU_NOTIFIER
         struct mmu_notifier_subscriptions *notifier_subscriptions;
 #endif
 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
         pgtable_t pmd_huge_pte; /* protected by page_table_lock */
 #endif
 #ifdef CONFIG_NUMA_BALANCING
         /*
          * numa_next_scan is the next time that the PTEs will be marked
          * pte_numa. NUMA hinting faults will gather statistics and
          * migrate pages to new nodes if necessary.
          */
         unsigned long numa_next_scan;
 
         /* Restart point for scanning and setting pte_numa */
         unsigned long numa_scan_offset;
 
         /* numa_scan_seq prevents two threads setting pte_numa */
         int numa_scan_seq;
 #endif
         /*
          * An operation with batched TLB flushing is going on. Anything
          * that can move process memory needs to flush the TLB when
          * moving a PROT_NONE or PROT_NUMA mapped page.
          */
         atomic_t tlb_flush_pending;
 #ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
         /* See flush_tlb_batched_pending() */
         atomic_t tlb_flush_batched;
 #endif
         struct uprobes_state uprobes_state;
 #ifdef CONFIG_PREEMPT_RT
         struct rcu_head delayed_drop;
 #endif
 #ifdef CONFIG_HUGETLB_PAGE
         atomic_long_t hugetlb_usage;
 #endif
         struct work_struct async_put_work;
 
 #ifdef CONFIG_IOMMU_SVA
         u32 pasid;
 #endif
 #ifdef CONFIG_KSM
         /*
          * Represent how many pages of this process are involved in KSM
          * merging.
          */
         unsigned long ksm_merging_pages;
 #endif
     } __randomize_layout;
 
     /*
      * The mm_cpumask needs to be at the end of mm_struct, because it
      * is dynamically sized based on nr_cpu_ids.
      */
     unsigned long cpu_bitmap[];
 };
 
 extern struct mm_struct init_mm;
 
 /* Pointer magic because the dynamic array size confuses some compilers. */
 static inline void mm_init_cpumask(struct mm_struct *mm)
 {
     unsigned long cpu_bitmap = (unsigned long)mm;
 
     cpu_bitmap += offsetof(struct mm_struct, cpu_bitmap);
     cpumask_clear((struct cpumask *)cpu_bitmap);
 }
 
 /* Future-safe accessor for struct mm_struct's cpu_vm_mask. */
 static inline cpumask_t *mm_cpumask(struct mm_struct *mm)
 {
     return (struct cpumask *)&mm->cpu_bitmap;
 }
 
 struct mmu_gather;
 extern void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm);
 extern void tlb_gather_mmu_fullmm(struct mmu_gather *tlb, struct mm_struct *mm);
 extern void tlb_finish_mmu(struct mmu_gather *tlb);
 
 struct vm_fault;
 
 /**
  * typedef vm_fault_t - Return type for page fault handlers.
  *
  * Page fault handlers return a bitmask of %VM_FAULT values.
  */
 typedef __bitwise unsigned int vm_fault_t;
 
 /**
  * enum vm_fault_reason - Page fault handlers return a bitmask of
  * these values to tell the core VM what happened when handling the
  * fault. Used to decide whether a process gets delivered SIGBUS or
  * just gets major/minor fault counters bumped up.
  *
  * @VM_FAULT_OOM:       Out Of Memory
  * @VM_FAULT_SIGBUS:        Bad access
  * @VM_FAULT_MAJOR:     Page read from storage
  * @VM_FAULT_WRITE:     Special case for get_user_pages
  * @VM_FAULT_HWPOISON:      Hit poisoned small page
  * @VM_FAULT_HWPOISON_LARGE:    Hit poisoned large page. Index encoded
  *              in upper bits
  * @VM_FAULT_SIGSEGV:       segmentation fault
  * @VM_FAULT_NOPAGE:        ->fault installed the pte, not return page
  * @VM_FAULT_LOCKED:        ->fault locked the returned page
  * @VM_FAULT_RETRY:     ->fault blocked, must retry
  * @VM_FAULT_FALLBACK:      huge page fault failed, fall back to small
  * @VM_FAULT_DONE_COW:      ->fault has fully handled COW
  * @VM_FAULT_NEEDDSYNC:     ->fault did not modify page tables and needs
  *              fsync() to complete (for synchronous page faults
  *              in DAX)
  * @VM_FAULT_COMPLETED:     ->fault completed, meanwhile mmap lock released
  * @VM_FAULT_HINDEX_MASK:   mask HINDEX value
  *
  */
 enum vm_fault_reason {
     VM_FAULT_OOM            = (__force vm_fault_t)0x000001,
     VM_FAULT_SIGBUS         = (__force vm_fault_t)0x000002,
     VM_FAULT_MAJOR          = (__force vm_fault_t)0x000004,
     VM_FAULT_WRITE          = (__force vm_fault_t)0x000008,
     VM_FAULT_HWPOISON       = (__force vm_fault_t)0x000010,
     VM_FAULT_HWPOISON_LARGE = (__force vm_fault_t)0x000020,
     VM_FAULT_SIGSEGV        = (__force vm_fault_t)0x000040,
     VM_FAULT_NOPAGE         = (__force vm_fault_t)0x000100,
     VM_FAULT_LOCKED         = (__force vm_fault_t)0x000200,
     VM_FAULT_RETRY          = (__force vm_fault_t)0x000400,
     VM_FAULT_FALLBACK       = (__force vm_fault_t)0x000800,
     VM_FAULT_DONE_COW       = (__force vm_fault_t)0x001000,
     VM_FAULT_NEEDDSYNC      = (__force vm_fault_t)0x002000,
     VM_FAULT_COMPLETED      = (__force vm_fault_t)0x004000,
     VM_FAULT_HINDEX_MASK    = (__force vm_fault_t)0x0f0000,
 };
 
 /* Encode hstate index for a hwpoisoned large page */
 #define VM_FAULT_SET_HINDEX(x) ((__force vm_fault_t)((x) << 16))
 #define VM_FAULT_GET_HINDEX(x) (((__force unsigned int)(x) >> 16) & 0xf)
 
 #define VM_FAULT_ERROR (VM_FAULT_OOM | VM_FAULT_SIGBUS |    \
             VM_FAULT_SIGSEGV | VM_FAULT_HWPOISON |  \
             VM_FAULT_HWPOISON_LARGE | VM_FAULT_FALLBACK)
 
 #define VM_FAULT_RESULT_TRACE \
     { VM_FAULT_OOM,                 "OOM" },    \
     { VM_FAULT_SIGBUS,              "SIGBUS" }, \
     { VM_FAULT_MAJOR,               "MAJOR" },  \
     { VM_FAULT_WRITE,               "WRITE" },  \
     { VM_FAULT_HWPOISON,            "HWPOISON" },   \
     { VM_FAULT_HWPOISON_LARGE,      "HWPOISON_LARGE" }, \
     { VM_FAULT_SIGSEGV,             "SIGSEGV" },    \
     { VM_FAULT_NOPAGE,              "NOPAGE" }, \
     { VM_FAULT_LOCKED,              "LOCKED" }, \
     { VM_FAULT_RETRY,               "RETRY" },  \
     { VM_FAULT_FALLBACK,            "FALLBACK" },   \
     { VM_FAULT_DONE_COW,            "DONE_COW" },   \
     { VM_FAULT_NEEDDSYNC,           "NEEDDSYNC" }
 
 struct vm_special_mapping {
     const char *name;   /* The name, e.g. "[vdso]". */
 
     /*
      * If .fault is not provided, this points to a
      * NULL-terminated array of pages that back the special mapping.
      *
      * This must not be NULL unless .fault is provided.
      */
     struct page **pages;
 
     /*
      * If non-NULL, then this is called to resolve page faults
      * on the special mapping.  If used, .pages is not checked.
      */
     vm_fault_t (*fault)(const struct vm_special_mapping *sm,
                 struct vm_area_struct *vma,
                 struct vm_fault *vmf);
 
     int (*mremap)(const struct vm_special_mapping *sm,
              struct vm_area_struct *new_vma);
 };
 
 enum tlb_flush_reason {
     TLB_FLUSH_ON_TASK_SWITCH,
     TLB_REMOTE_SHOOTDOWN,
     TLB_LOCAL_SHOOTDOWN,
     TLB_LOCAL_MM_SHOOTDOWN,
     TLB_REMOTE_SEND_IPI,
     NR_TLB_FLUSH_REASONS,
 };
 
  /*
   * A swap entry has to fit into a "unsigned long", as the entry is hidden
   * in the "index" field of the swapper address space.
   */
 typedef struct {
     unsigned long val;
 } swp_entry_t;
 
 /**
  * enum fault_flag - Fault flag definitions.
  * @FAULT_FLAG_WRITE: Fault was a write fault.
  * @FAULT_FLAG_MKWRITE: Fault was mkwrite of existing PTE.
  * @FAULT_FLAG_ALLOW_RETRY: Allow to retry the fault if blocked.
  * @FAULT_FLAG_RETRY_NOWAIT: Don't drop mmap_lock and wait when retrying.
  * @FAULT_FLAG_KILLABLE: The fault task is in SIGKILL killable region.
  * @FAULT_FLAG_TRIED: The fault has been tried once.
  * @FAULT_FLAG_USER: The fault originated in userspace.
  * @FAULT_FLAG_REMOTE: The fault is not for current task/mm.
  * @FAULT_FLAG_INSTRUCTION: The fault was during an instruction fetch.
  * @FAULT_FLAG_INTERRUPTIBLE: The fault can be interrupted by non-fatal signals.
  * @FAULT_FLAG_UNSHARE: The fault is an unsharing request to unshare (and mark
  *                      exclusive) a possibly shared anonymous page that is
  *                      mapped R/O.
  * @FAULT_FLAG_ORIG_PTE_VALID: whether the fault has vmf->orig_pte cached.
  *                        We should only access orig_pte if this flag set.
  *
  * About @FAULT_FLAG_ALLOW_RETRY and @FAULT_FLAG_TRIED: we can specify
  * whether we would allow page faults to retry by specifying these two
  * fault flags correctly.  Currently there can be three legal combinations:
  *
  * (a) ALLOW_RETRY and !TRIED:  this means the page fault allows retry, and
  *                              this is the first try
  *
  * (b) ALLOW_RETRY and TRIED:   this means the page fault allows retry, and
  *                              we've already tried at least once
  *
  * (c) !ALLOW_RETRY and !TRIED: this means the page fault does not allow retry
  *
  * The unlisted combination (!ALLOW_RETRY && TRIED) is illegal and should never
  * be used.  Note that page faults can be allowed to retry for multiple times,
  * in which case we'll have an initial fault with flags (a) then later on
  * continuous faults with flags (b).  We should always try to detect pending
  * signals before a retry to make sure the continuous page faults can still be
  * interrupted if necessary.
  *
  * The combination FAULT_FLAG_WRITE|FAULT_FLAG_UNSHARE is illegal.
  * FAULT_FLAG_UNSHARE is ignored and treated like an ordinary read fault when
  * no existing R/O-mapped anonymous page is encountered.
  */
 enum fault_flag {
     FAULT_FLAG_WRITE =      1 << 0,
     FAULT_FLAG_MKWRITE =        1 << 1,
     FAULT_FLAG_ALLOW_RETRY =    1 << 2,
     FAULT_FLAG_RETRY_NOWAIT =   1 << 3,
     FAULT_FLAG_KILLABLE =       1 << 4,
     FAULT_FLAG_TRIED =      1 << 5,
     FAULT_FLAG_USER =       1 << 6,
     FAULT_FLAG_REMOTE =     1 << 7,
     FAULT_FLAG_INSTRUCTION =    1 << 8,
     FAULT_FLAG_INTERRUPTIBLE =  1 << 9,
     FAULT_FLAG_UNSHARE =        1 << 10,
     FAULT_FLAG_ORIG_PTE_VALID = 1 << 11,
 };
 
 typedef unsigned int __bitwise zap_flags_t;
 
 #endif /* _LINUX_MM_TYPES_H */

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