include/linux/rmap.h - third_party/kernel - Git at Google

 /* 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_HWPOISON		= 0x20,	/* do convert pte to hwpoison entry */
 	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 *folio_get_anon_vma(struct folio *folio);

 /* 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.
  *
  * 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);

 	/* device private pages cannot get pinned via GUP. */
 	if (unlikely(is_device_private_page(page))) {
 		ClearPageAnonExclusive(page);
 		return 0;
 	}

 	/*
 	 * We have to make sure that when we clear PageAnonExclusive, that
 	 * the page is not pinned and that concurrent GUP-fast won't succeed in
 	 * concurrently pinning the page.
 	 *
 	 * Conceptually, PageAnonExclusive clearing consists of:
 	 * (A1) Clear PTE
 	 * (A2) Check if the page is pinned; back off if so.
 	 * (A3) Clear PageAnonExclusive
 	 * (A4) Restore PTE (optional, but certainly not writable)
 	 *
 	 * When clearing PageAnonExclusive, we cannot possibly map the page
 	 * writable again, because anon pages that may be shared must never
 	 * be writable. So in any case, if the PTE was writable it cannot
 	 * be writable anymore afterwards and there would be a PTE change. Only
 	 * if the PTE wasn't writable, there might not be a PTE change.
 	 *
 	 * Conceptually, GUP-fast pinning of an anon page consists of:
 	 * (B1) Read the PTE
 	 * (B2) FOLL_WRITE: check if the PTE is not writable; back off if so.
 	 * (B3) Pin the mapped page
 	 * (B4) Check if the PTE changed by re-reading it; back off if so.
 	 * (B5) If the original PTE is not writable, check if
 	 *	PageAnonExclusive is not set; back off if so.
 	 *
 	 * If the PTE was writable, we only have to make sure that GUP-fast
 	 * observes a PTE change and properly backs off.
 	 *
 	 * If the PTE was not writable, we have to make sure that GUP-fast either
 	 * detects a (temporary) PTE change or that PageAnonExclusive is cleared
 	 * and properly backs off.
 	 *
 	 * Consequently, when clearing PageAnonExclusive(), we have to make
 	 * sure that (A1), (A2)/(A3) and (A4) happen in the right memory
 	 * order. In GUP-fast pinning code, we have to make sure that (B3),(B4)
 	 * and (B5) happen in the right memory order.
 	 *
 	 * We assume that there might not be a memory barrier after
 	 * clearing/invalidating the PTE (A1) and before restoring the PTE (A4),
 	 * so we use explicit ones here.
 	 */

 	/* Paired with the memory barrier in try_grab_folio(). */
 	if (IS_ENABLED(CONFIG_HAVE_FAST_GUP))
 		smp_mb();

 	if (unlikely(page_maybe_dma_pinned(page)))
 		return -EBUSY;
 	ClearPageAnonExclusive(page);

 	/*
 	 * This is conceptually a smp_wmb() paired with the smp_rmb() in
 	 * gup_must_unshare().
 	 */
 	if (IS_ENABLED(CONFIG_HAVE_FAST_GUP))
 		smp_mb__after_atomic();
 	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);
 struct anon_vma *folio_lock_anon_vma_read(struct folio *folio,
 					  struct rmap_walk_control *rwc);

 #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 */
	/* 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_HWPOISON = 0x20, /* do convert pte to hwpoison entry */
	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 folio_get_anon_vma(struct folio folio);

	/* 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.
	*
	* 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);

	/* device private pages cannot get pinned via GUP. */
	if (unlikely(is_device_private_page(page))) {
	ClearPageAnonExclusive(page);
	return 0;
	}

	/*
	* We have to make sure that when we clear PageAnonExclusive, that
	* the page is not pinned and that concurrent GUP-fast won't succeed in
	* concurrently pinning the page.
	*
	* Conceptually, PageAnonExclusive clearing consists of:
	* (A1) Clear PTE
	* (A2) Check if the page is pinned; back off if so.
	* (A3) Clear PageAnonExclusive
	* (A4) Restore PTE (optional, but certainly not writable)
	*
	* When clearing PageAnonExclusive, we cannot possibly map the page
	* writable again, because anon pages that may be shared must never
	* be writable. So in any case, if the PTE was writable it cannot
	* be writable anymore afterwards and there would be a PTE change. Only
	* if the PTE wasn't writable, there might not be a PTE change.
	*
	* Conceptually, GUP-fast pinning of an anon page consists of:
	* (B1) Read the PTE
	* (B2) FOLL_WRITE: check if the PTE is not writable; back off if so.
	* (B3) Pin the mapped page
	* (B4) Check if the PTE changed by re-reading it; back off if so.
	* (B5) If the original PTE is not writable, check if
	* PageAnonExclusive is not set; back off if so.
	*
	* If the PTE was writable, we only have to make sure that GUP-fast
	* observes a PTE change and properly backs off.
	*
	* If the PTE was not writable, we have to make sure that GUP-fast either
	* detects a (temporary) PTE change or that PageAnonExclusive is cleared
	* and properly backs off.
	*
	* Consequently, when clearing PageAnonExclusive(), we have to make
	* sure that (A1), (A2)/(A3) and (A4) happen in the right memory
	* order. In GUP-fast pinning code, we have to make sure that (B3),(B4)
	* and (B5) happen in the right memory order.
	*
	* We assume that there might not be a memory barrier after
	* clearing/invalidating the PTE (A1) and before restoring the PTE (A4),
	* so we use explicit ones here.
	*/

	/* Paired with the memory barrier in try_grab_folio(). */
	if (IS_ENABLED(CONFIG_HAVE_FAST_GUP))
	smp_mb();

	if (unlikely(page_maybe_dma_pinned(page)))
	return -EBUSY;
	ClearPageAnonExclusive(page);

	/*
	* This is conceptually a smp_wmb() paired with the smp_rmb() in
	* gup_must_unshare().
	*/
	if (IS_ENABLED(CONFIG_HAVE_FAST_GUP))
	smp_mb__after_atomic();
	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);
	struct anon_vma folio_lock_anon_vma_read(struct folio folio,
	struct rmap_walk_control *rwc);

	#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 */