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 /* SPDX-License-Identifier: GPL-2.0 */
 #ifndef _LINUX_RMAP_H
 #define _LINUX_RMAP_H
 /*
  * Declarations for Reverse Mapping functions in mm/rmap.c
  */
 
 #include <linux/list.h>
 #include <linux/slab.h>
 #include <linux/mm.h>
 #include <linux/rwsem.h>
 #include <linux/memcontrol.h>
 #include <linux/highmem.h>
 #include <linux/pagemap.h>
 #include <linux/memremap.h>
 
 /*
  * The anon_vma heads a list of private "related" vmas, to scan if
  * an anonymous page pointing to this anon_vma needs to be unmapped:
  * the vmas on the list will be related by forking, or by splitting.
  *
  * Since vmas come and go as they are split and merged (particularly
  * in mprotect), the mapping field of an anonymous page cannot point
  * directly to a vma: instead it points to an anon_vma, on whose list
  * the related vmas can be easily linked or unlinked.
  *
  * After unlinking the last vma on the list, we must garbage collect
  * the anon_vma object itself: we're guaranteed no page can be
  * pointing to this anon_vma once its vma list is empty.
  */
 struct anon_vma {
     struct anon_vma *root;      /* Root of this anon_vma tree */
     struct rw_semaphore rwsem;  /* W: modification, R: walking the list */
     /*
      * The refcount is taken on an anon_vma when there is no
      * guarantee that the vma of page tables will exist for
      * the duration of the operation. A caller that takes
      * the reference is responsible for clearing up the
      * anon_vma if they are the last user on release
      */
     atomic_t refcount;
 
     /*
      * Count of child anon_vmas. Equals to the count of all anon_vmas that
      * have ->parent pointing to this one, including itself.
      *
      * This counter is used for making decision about reusing anon_vma
      * instead of forking new one. See comments in function anon_vma_clone.
      */
     unsigned long num_children;
     /* Count of VMAs whose ->anon_vma pointer points to this object. */
     unsigned long num_active_vmas;
 
     struct anon_vma *parent;    /* Parent of this anon_vma */
 
     /*
      * NOTE: the LSB of the rb_root.rb_node is set by
      * mm_take_all_locks() _after_ taking the above lock. So the
      * rb_root must only be read/written after taking the above lock
      * to be sure to see a valid next pointer. The LSB bit itself
      * is serialized by a system wide lock only visible to
      * mm_take_all_locks() (mm_all_locks_mutex).
      */
 
     /* Interval tree of private "related" vmas */
     struct rb_root_cached rb_root;
 };
 
 /*
  * The copy-on-write semantics of fork mean that an anon_vma
  * can become associated with multiple processes. Furthermore,
  * each child process will have its own anon_vma, where new
  * pages for that process are instantiated.
  *
  * This structure allows us to find the anon_vmas associated
  * with a VMA, or the VMAs associated with an anon_vma.
  * The "same_vma" list contains the anon_vma_chains linking
  * all the anon_vmas associated with this VMA.
  * The "rb" field indexes on an interval tree the anon_vma_chains
  * which link all the VMAs associated with this anon_vma.
  */
 struct anon_vma_chain {
     struct vm_area_struct *vma;
     struct anon_vma *anon_vma;
     struct list_head same_vma;   /* locked by mmap_lock & page_table_lock */
     struct rb_node rb;          /* locked by anon_vma->rwsem */
     unsigned long rb_subtree_last;
 #ifdef CONFIG_DEBUG_VM_RB
     unsigned long cached_vma_start, cached_vma_last;
 #endif
 };
 
 enum ttu_flags {
     TTU_SPLIT_HUGE_PMD  = 0x4,  /* split huge PMD if any */
     TTU_IGNORE_MLOCK    = 0x8,  /* ignore mlock */
     TTU_SYNC        = 0x10, /* avoid racy checks with PVMW_SYNC */
     TTU_IGNORE_HWPOISON = 0x20, /* corrupted page is recoverable */
     TTU_BATCH_FLUSH     = 0x40, /* Batch TLB flushes where possible
                      * and caller guarantees they will
                      * do a final flush if necessary */
     TTU_RMAP_LOCKED     = 0x80, /* do not grab rmap lock:
                      * caller holds it */
 };
 
 #ifdef CONFIG_MMU
 static inline void get_anon_vma(struct anon_vma *anon_vma)
 {
     atomic_inc(&anon_vma->refcount);
 }
 
 void __put_anon_vma(struct anon_vma *anon_vma);
 
 static inline void put_anon_vma(struct anon_vma *anon_vma)
 {
     if (atomic_dec_and_test(&anon_vma->refcount))
         __put_anon_vma(anon_vma);
 }
 
 static inline void anon_vma_lock_write(struct anon_vma *anon_vma)
 {
     down_write(&anon_vma->root->rwsem);
 }
 
 static inline void anon_vma_unlock_write(struct anon_vma *anon_vma)
 {
     up_write(&anon_vma->root->rwsem);
 }
 
 static inline void anon_vma_lock_read(struct anon_vma *anon_vma)
 {
     down_read(&anon_vma->root->rwsem);
 }
 
 static inline int anon_vma_trylock_read(struct anon_vma *anon_vma)
 {
     return down_read_trylock(&anon_vma->root->rwsem);
 }
 
 static inline void anon_vma_unlock_read(struct anon_vma *anon_vma)
 {
     up_read(&anon_vma->root->rwsem);
 }
 
 
 /*
  * anon_vma helper functions.
  */
 void anon_vma_init(void);   /* create anon_vma_cachep */
 int  __anon_vma_prepare(struct vm_area_struct *);
 void unlink_anon_vmas(struct vm_area_struct *);
 int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *);
 int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *);
 
 static inline int anon_vma_prepare(struct vm_area_struct *vma)
 {
     if (likely(vma->anon_vma))
         return 0;
 
     return __anon_vma_prepare(vma);
 }
 
 static inline void anon_vma_merge(struct vm_area_struct *vma,
                   struct vm_area_struct *next)
 {
     VM_BUG_ON_VMA(vma->anon_vma != next->anon_vma, vma);
     unlink_anon_vmas(next);
 }
 
 struct anon_vma *page_get_anon_vma(struct page *page);
 
 /* RMAP flags, currently only relevant for some anon rmap operations. */
 typedef int __bitwise rmap_t;
 
 /*
  * No special request: if the page is a subpage of a compound page, it is
  * mapped via a PTE. The mapped (sub)page is possibly shared between processes.
  */
 #define RMAP_NONE       ((__force rmap_t)0)
 
 /* The (sub)page is exclusive to a single process. */
 #define RMAP_EXCLUSIVE      ((__force rmap_t)BIT(0))
 
 /*
  * The compound page is not mapped via PTEs, but instead via a single PMD and
  * should be accounted accordingly.
  */
 #define RMAP_COMPOUND       ((__force rmap_t)BIT(1))
 
 /*
  * rmap interfaces called when adding or removing pte of page
  */
 void page_move_anon_rmap(struct page *, struct vm_area_struct *);
 void page_add_anon_rmap(struct page *, struct vm_area_struct *,
         unsigned long address, rmap_t flags);
 void page_add_new_anon_rmap(struct page *, struct vm_area_struct *,
         unsigned long address);
 void page_add_file_rmap(struct page *, struct vm_area_struct *,
         bool compound);
 void page_remove_rmap(struct page *, struct vm_area_struct *,
         bool compound);
 
 void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *,
         unsigned long address, rmap_t flags);
 void hugepage_add_new_anon_rmap(struct page *, struct vm_area_struct *,
         unsigned long address);
 
 static inline void __page_dup_rmap(struct page *page, bool compound)
 {
     atomic_inc(compound ? compound_mapcount_ptr(page) : &page->_mapcount);
 }
 
 static inline void page_dup_file_rmap(struct page *page, bool compound)
 {
     __page_dup_rmap(page, compound);
 }
 
 /**
  * page_try_dup_anon_rmap - try duplicating a mapping of an already mapped
  *              anonymous page
  * @page: the page to duplicate the mapping for
  * @compound: the page is mapped as compound or as a small page
  * @vma: the source vma
  *
  * The caller needs to hold the PT lock and the vma->vma_mm->write_protect_seq.
  *
  * Duplicating the mapping can only fail if the page may be pinned; device
  * private pages cannot get pinned and consequently this function cannot fail.
  *
  * If duplicating the mapping succeeds, the page has to be mapped R/O into
  * the parent and the child. It must *not* get mapped writable after this call.
  *
  * Returns 0 if duplicating the mapping succeeded. Returns -EBUSY otherwise.
  */
 static inline int page_try_dup_anon_rmap(struct page *page, bool compound,
                      struct vm_area_struct *vma)
 {
     VM_BUG_ON_PAGE(!PageAnon(page), page);
 
     /*
      * No need to check+clear for already shared pages, including KSM
      * pages.
      */
     if (!PageAnonExclusive(page))
         goto dup;
 
     /*
      * If this page may have been pinned by the parent process,
      * don't allow to duplicate the mapping but instead require to e.g.,
      * copy the page immediately for the child so that we'll always
      * guarantee the pinned page won't be randomly replaced in the
      * future on write faults.
      */
     if (likely(!is_device_private_page(page) &&
         unlikely(page_needs_cow_for_dma(vma, page))))
         return -EBUSY;
 
     ClearPageAnonExclusive(page);
     /*
      * It's okay to share the anon page between both processes, mapping
      * the page R/O into both processes.
      */
 dup:
     __page_dup_rmap(page, compound);
     return 0;
 }
 
 /**
  * page_try_share_anon_rmap - try marking an exclusive anonymous page possibly
  *                shared to prepare for KSM or temporary unmapping
  * @page: the exclusive anonymous page to try marking possibly shared
  *
  * The caller needs to hold the PT lock and has to have the page table entry
  * cleared/invalidated+flushed, to properly sync against GUP-fast.
  *
  * This is similar to page_try_dup_anon_rmap(), however, not used during fork()
  * to duplicate a mapping, but instead to prepare for KSM or temporarily
  * unmapping a page (swap, migration) via page_remove_rmap().
  *
  * Marking the page shared can only fail if the page may be pinned; device
  * private pages cannot get pinned and consequently this function cannot fail.
  *
  * Returns 0 if marking the page possibly shared succeeded. Returns -EBUSY
  * otherwise.
  */
 static inline int page_try_share_anon_rmap(struct page *page)
 {
     VM_BUG_ON_PAGE(!PageAnon(page) || !PageAnonExclusive(page), page);
 
     /* See page_try_dup_anon_rmap(). */
     if (likely(!is_device_private_page(page) &&
         unlikely(page_maybe_dma_pinned(page))))
         return -EBUSY;
 
     ClearPageAnonExclusive(page);
     return 0;
 }
 
 /*
  * Called from mm/vmscan.c to handle paging out
  */
 int folio_referenced(struct folio *, int is_locked,
             struct mem_cgroup *memcg, unsigned long *vm_flags);
 
 void try_to_migrate(struct folio *folio, enum ttu_flags flags);
 void try_to_unmap(struct folio *, enum ttu_flags flags);
 
 int make_device_exclusive_range(struct mm_struct *mm, unsigned long start,
                 unsigned long end, struct page **pages,
                 void *arg);
 
 /* Avoid racy checks */
 #define PVMW_SYNC       (1 << 0)
 /* Look for migration entries rather than present PTEs */
 #define PVMW_MIGRATION      (1 << 1)
 
 struct page_vma_mapped_walk {
     unsigned long pfn;
     unsigned long nr_pages;
     pgoff_t pgoff;
     struct vm_area_struct *vma;
     unsigned long address;
     pmd_t *pmd;
     pte_t *pte;
     spinlock_t *ptl;
     unsigned int flags;
 };
 
 #define DEFINE_PAGE_VMA_WALK(name, _page, _vma, _address, _flags)   \
     struct page_vma_mapped_walk name = {                \
         .pfn = page_to_pfn(_page),              \
         .nr_pages = compound_nr(_page),             \
         .pgoff = page_to_pgoff(_page),              \
         .vma = _vma,                        \
         .address = _address,                    \
         .flags = _flags,                    \
     }
 
 #define DEFINE_FOLIO_VMA_WALK(name, _folio, _vma, _address, _flags) \
     struct page_vma_mapped_walk name = {                \
         .pfn = folio_pfn(_folio),               \
         .nr_pages = folio_nr_pages(_folio),         \
         .pgoff = folio_pgoff(_folio),               \
         .vma = _vma,                        \
         .address = _address,                    \
         .flags = _flags,                    \
     }
 
 static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
 {
     /* HugeTLB pte is set to the relevant page table entry without pte_mapped. */
     if (pvmw->pte && !is_vm_hugetlb_page(pvmw->vma))
         pte_unmap(pvmw->pte);
     if (pvmw->ptl)
         spin_unlock(pvmw->ptl);
 }
 
 bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw);
 
 /*
  * Used by swapoff to help locate where page is expected in vma.
  */
 unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
 
 /*
  * Cleans the PTEs of shared mappings.
  * (and since clean PTEs should also be readonly, write protects them too)
  *
  * returns the number of cleaned PTEs.
  */
 int folio_mkclean(struct folio *);
 
 int pfn_mkclean_range(unsigned long pfn, unsigned long nr_pages, pgoff_t pgoff,
               struct vm_area_struct *vma);
 
 void remove_migration_ptes(struct folio *src, struct folio *dst, bool locked);
 
 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
 
 /*
  * rmap_walk_control: To control rmap traversing for specific needs
  *
  * arg: passed to rmap_one() and invalid_vma()
  * try_lock: bail out if the rmap lock is contended
  * contended: indicate the rmap traversal bailed out due to lock contention
  * rmap_one: executed on each vma where page is mapped
  * done: for checking traversing termination condition
  * anon_lock: for getting anon_lock by optimized way rather than default
  * invalid_vma: for skipping uninterested vma
  */
 struct rmap_walk_control {
     void *arg;
     bool try_lock;
     bool contended;
     /*
      * Return false if page table scanning in rmap_walk should be stopped.
      * Otherwise, return true.
      */
     bool (*rmap_one)(struct folio *folio, struct vm_area_struct *vma,
                     unsigned long addr, void *arg);
     int (*done)(struct folio *folio);
     struct anon_vma *(*anon_lock)(struct folio *folio,
                       struct rmap_walk_control *rwc);
     bool (*invalid_vma)(struct vm_area_struct *vma, void *arg);
 };
 
 void rmap_walk(struct folio *folio, struct rmap_walk_control *rwc);
 void rmap_walk_locked(struct folio *folio, struct rmap_walk_control *rwc);
 
 /*
  * Called by memory-failure.c to kill processes.
  */
 struct anon_vma *folio_lock_anon_vma_read(struct folio *folio,
                       struct rmap_walk_control *rwc);
 void page_unlock_anon_vma_read(struct anon_vma *anon_vma);
 
 #else   /* !CONFIG_MMU */
 
 #define anon_vma_init()     do {} while (0)
 #define anon_vma_prepare(vma)   (0)
 #define anon_vma_link(vma)  do {} while (0)
 
 static inline int folio_referenced(struct folio *folio, int is_locked,
                   struct mem_cgroup *memcg,
                   unsigned long *vm_flags)
 {
     *vm_flags = 0;
     return 0;
 }
 
 static inline void try_to_unmap(struct folio *folio, enum ttu_flags flags)
 {
 }
 
 static inline int folio_mkclean(struct folio *folio)
 {
     return 0;
 }
 #endif  /* CONFIG_MMU */
 
 static inline int page_mkclean(struct page *page)
 {
     return folio_mkclean(page_folio(page));
 }
 #endif  /* _LINUX_RMAP_H */

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