/* 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>

  
  /*
   * 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 and VMAs which points to this anon_vma.
  	 *
  	 * This counter is used for making decision about reusing anon_vma
  	 * instead of forking new one. See comments in function anon_vma_clone.
  	 */
  	unsigned degree;
  
  	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_MIGRATION		= 0x1,	/* migration mode */
  	TTU_MUNLOCK		= 0x2,	/* munlock mode */
  
  	TTU_SPLIT_HUGE_PMD	= 0x4,	/* split huge PMD if any */
  	TTU_IGNORE_MLOCK	= 0x8,	/* ignore mlock */

  	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 */

  	TTU_SPLIT_FREEZE	= 0x100,		/* freeze pte under splitting thp */

  };

  #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 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);

  /* bitflags for do_page_add_anon_rmap() */
  #define RMAP_EXCLUSIVE 0x01
  #define RMAP_COMPOUND 0x02

  /*
   * 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, bool);

  void do_page_add_anon_rmap(struct page *, struct vm_area_struct *,
  			   unsigned long, int);

  void page_add_new_anon_rmap(struct page *, struct vm_area_struct *,
  		unsigned long, bool);

  void page_add_file_rmap(struct page *, bool);

  void page_remove_rmap(struct page *, bool);

  void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *,
  			    unsigned long);
  void hugepage_add_new_anon_rmap(struct page *, struct vm_area_struct *,
  				unsigned long);

  static inline void page_dup_rmap(struct page *page, bool compound)

  {

  	atomic_inc(compound ? compound_mapcount_ptr(page) : &page->_mapcount);

  }
  
  /*
   * Called from mm/vmscan.c to handle paging out
   */

  int page_referenced(struct page *, int is_locked,

  			struct mem_cgroup *memcg, unsigned long *vm_flags);

  bool try_to_unmap(struct page *, enum ttu_flags flags);

  /* Avoid racy checks */
  #define PVMW_SYNC		(1 << 0)
  /* Look for migarion entries rather than present PTEs */
  #define PVMW_MIGRATION		(1 << 1)
  
  struct page_vma_mapped_walk {
  	struct page *page;
  	struct vm_area_struct *vma;
  	unsigned long address;
  	pmd_t *pmd;
  	pte_t *pte;
  	spinlock_t *ptl;
  	unsigned int flags;
  };
  
  static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
  {
  	if (pvmw->pte)
  		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 page_mkclean(struct page *);

  /*
   * called in munlock()/munmap() path to check for other vmas holding
   * the page mlocked.
   */

  void try_to_munlock(struct page *);

  void remove_migration_ptes(struct page *old, struct page *new, bool locked);

  /*
   * Called by memory-failure.c to kill processes.
   */

  struct anon_vma *page_lock_anon_vma_read(struct page *page);
  void page_unlock_anon_vma_read(struct anon_vma *anon_vma);

  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()
   * 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;

  	/*
  	 * Return false if page table scanning in rmap_walk should be stopped.
  	 * Otherwise, return true.
  	 */
  	bool (*rmap_one)(struct page *page, struct vm_area_struct *vma,

  					unsigned long addr, void *arg);

  	int (*done)(struct page *page);

  	struct anon_vma *(*anon_lock)(struct page *page);
  	bool (*invalid_vma)(struct vm_area_struct *vma, void *arg);

  };

  void rmap_walk(struct page *page, struct rmap_walk_control *rwc);
  void rmap_walk_locked(struct page *page, 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 page_referenced(struct page *page, int is_locked,

  				  struct mem_cgroup *memcg,

  				  unsigned long *vm_flags)
  {
  	*vm_flags = 0;

  	return 0;

  }

  #define try_to_unmap(page, refs) false

  static inline int page_mkclean(struct page *page)
  {
  	return 0;
  }

  #endif	/* CONFIG_MMU */

  #endif	/* _LINUX_RMAP_H */