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       1                 :            : /* SPDX-License-Identifier: GPL-2.0 */
       2                 :            : #ifndef _LINUX_RMAP_H
       3                 :            : #define _LINUX_RMAP_H
       4                 :            : /*
       5                 :            :  * Declarations for Reverse Mapping functions in mm/rmap.c
       6                 :            :  */
       7                 :            : 
       8                 :            : #include <linux/list.h>
       9                 :            : #include <linux/slab.h>
      10                 :            : #include <linux/mm.h>
      11                 :            : #include <linux/rwsem.h>
      12                 :            : #include <linux/memcontrol.h>
      13                 :            : #include <linux/highmem.h>
      14                 :            : 
      15                 :            : /*
      16                 :            :  * The anon_vma heads a list of private "related" vmas, to scan if
      17                 :            :  * an anonymous page pointing to this anon_vma needs to be unmapped:
      18                 :            :  * the vmas on the list will be related by forking, or by splitting.
      19                 :            :  *
      20                 :            :  * Since vmas come and go as they are split and merged (particularly
      21                 :            :  * in mprotect), the mapping field of an anonymous page cannot point
      22                 :            :  * directly to a vma: instead it points to an anon_vma, on whose list
      23                 :            :  * the related vmas can be easily linked or unlinked.
      24                 :            :  *
      25                 :            :  * After unlinking the last vma on the list, we must garbage collect
      26                 :            :  * the anon_vma object itself: we're guaranteed no page can be
      27                 :            :  * pointing to this anon_vma once its vma list is empty.
      28                 :            :  */
      29                 :            : struct anon_vma {
      30                 :            :         struct anon_vma *root;          /* Root of this anon_vma tree */
      31                 :            :         struct rw_semaphore rwsem;      /* W: modification, R: walking the list */
      32                 :            :         /*
      33                 :            :          * The refcount is taken on an anon_vma when there is no
      34                 :            :          * guarantee that the vma of page tables will exist for
      35                 :            :          * the duration of the operation. A caller that takes
      36                 :            :          * the reference is responsible for clearing up the
      37                 :            :          * anon_vma if they are the last user on release
      38                 :            :          */
      39                 :            :         atomic_t refcount;
      40                 :            : 
      41                 :            :         /*
      42                 :            :          * Count of child anon_vmas and VMAs which points to this anon_vma.
      43                 :            :          *
      44                 :            :          * This counter is used for making decision about reusing anon_vma
      45                 :            :          * instead of forking new one. See comments in function anon_vma_clone.
      46                 :            :          */
      47                 :            :         unsigned degree;
      48                 :            : 
      49                 :            :         struct anon_vma *parent;        /* Parent of this anon_vma */
      50                 :            : 
      51                 :            :         /*
      52                 :            :          * NOTE: the LSB of the rb_root.rb_node is set by
      53                 :            :          * mm_take_all_locks() _after_ taking the above lock. So the
      54                 :            :          * rb_root must only be read/written after taking the above lock
      55                 :            :          * to be sure to see a valid next pointer. The LSB bit itself
      56                 :            :          * is serialized by a system wide lock only visible to
      57                 :            :          * mm_take_all_locks() (mm_all_locks_mutex).
      58                 :            :          */
      59                 :            : 
      60                 :            :         /* Interval tree of private "related" vmas */
      61                 :            :         struct rb_root_cached rb_root;
      62                 :            : };
      63                 :            : 
      64                 :            : /*
      65                 :            :  * The copy-on-write semantics of fork mean that an anon_vma
      66                 :            :  * can become associated with multiple processes. Furthermore,
      67                 :            :  * each child process will have its own anon_vma, where new
      68                 :            :  * pages for that process are instantiated.
      69                 :            :  *
      70                 :            :  * This structure allows us to find the anon_vmas associated
      71                 :            :  * with a VMA, or the VMAs associated with an anon_vma.
      72                 :            :  * The "same_vma" list contains the anon_vma_chains linking
      73                 :            :  * all the anon_vmas associated with this VMA.
      74                 :            :  * The "rb" field indexes on an interval tree the anon_vma_chains
      75                 :            :  * which link all the VMAs associated with this anon_vma.
      76                 :            :  */
      77                 :            : struct anon_vma_chain {
      78                 :            :         struct vm_area_struct *vma;
      79                 :            :         struct anon_vma *anon_vma;
      80                 :            :         struct list_head same_vma;   /* locked by mmap_sem & page_table_lock */
      81                 :            :         struct rb_node rb;                      /* locked by anon_vma->rwsem */
      82                 :            :         unsigned long rb_subtree_last;
      83                 :            : #ifdef CONFIG_DEBUG_VM_RB
      84                 :            :         unsigned long cached_vma_start, cached_vma_last;
      85                 :            : #endif
      86                 :            : };
      87                 :            : 
      88                 :            : enum ttu_flags {
      89                 :            :         TTU_MIGRATION           = 0x1,  /* migration mode */
      90                 :            :         TTU_MUNLOCK             = 0x2,  /* munlock mode */
      91                 :            : 
      92                 :            :         TTU_SPLIT_HUGE_PMD      = 0x4,  /* split huge PMD if any */
      93                 :            :         TTU_IGNORE_MLOCK        = 0x8,  /* ignore mlock */
      94                 :            :         TTU_IGNORE_ACCESS       = 0x10, /* don't age */
      95                 :            :         TTU_IGNORE_HWPOISON     = 0x20, /* corrupted page is recoverable */
      96                 :            :         TTU_BATCH_FLUSH         = 0x40, /* Batch TLB flushes where possible
      97                 :            :                                          * and caller guarantees they will
      98                 :            :                                          * do a final flush if necessary */
      99                 :            :         TTU_RMAP_LOCKED         = 0x80, /* do not grab rmap lock:
     100                 :            :                                          * caller holds it */
     101                 :            :         TTU_SPLIT_FREEZE        = 0x100,                /* freeze pte under splitting thp */
     102                 :            : };
     103                 :            : 
     104                 :            : #ifdef CONFIG_MMU
     105                 :            : static inline void get_anon_vma(struct anon_vma *anon_vma)
     106                 :            : {
     107                 :          3 :         atomic_inc(&anon_vma->refcount);
     108                 :            : }
     109                 :            : 
     110                 :            : void __put_anon_vma(struct anon_vma *anon_vma);
     111                 :            : 
     112                 :          3 : static inline void put_anon_vma(struct anon_vma *anon_vma)
     113                 :            : {
     114                 :          3 :         if (atomic_dec_and_test(&anon_vma->refcount))
     115                 :          3 :                 __put_anon_vma(anon_vma);
     116                 :          3 : }
     117                 :            : 
     118                 :            : static inline void anon_vma_lock_write(struct anon_vma *anon_vma)
     119                 :            : {
     120                 :          3 :         down_write(&anon_vma->root->rwsem);
     121                 :            : }
     122                 :            : 
     123                 :            : static inline void anon_vma_unlock_write(struct anon_vma *anon_vma)
     124                 :            : {
     125                 :          3 :         up_write(&anon_vma->root->rwsem);
     126                 :            : }
     127                 :            : 
     128                 :            : static inline void anon_vma_lock_read(struct anon_vma *anon_vma)
     129                 :            : {
     130                 :          0 :         down_read(&anon_vma->root->rwsem);
     131                 :            : }
     132                 :            : 
     133                 :            : static inline void anon_vma_unlock_read(struct anon_vma *anon_vma)
     134                 :            : {
     135                 :          0 :         up_read(&anon_vma->root->rwsem);
     136                 :            : }
     137                 :            : 
     138                 :            : 
     139                 :            : /*
     140                 :            :  * anon_vma helper functions.
     141                 :            :  */
     142                 :            : void anon_vma_init(void);       /* create anon_vma_cachep */
     143                 :            : int  __anon_vma_prepare(struct vm_area_struct *);
     144                 :            : void unlink_anon_vmas(struct vm_area_struct *);
     145                 :            : int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *);
     146                 :            : int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *);
     147                 :            : 
     148                 :            : static inline int anon_vma_prepare(struct vm_area_struct *vma)
     149                 :            : {
     150                 :          3 :         if (likely(vma->anon_vma))
     151                 :            :                 return 0;
     152                 :            : 
     153                 :          3 :         return __anon_vma_prepare(vma);
     154                 :            : }
     155                 :            : 
     156                 :            : static inline void anon_vma_merge(struct vm_area_struct *vma,
     157                 :            :                                   struct vm_area_struct *next)
     158                 :            : {
     159                 :            :         VM_BUG_ON_VMA(vma->anon_vma != next->anon_vma, vma);
     160                 :          3 :         unlink_anon_vmas(next);
     161                 :            : }
     162                 :            : 
     163                 :            : struct anon_vma *page_get_anon_vma(struct page *page);
     164                 :            : 
     165                 :            : /* bitflags for do_page_add_anon_rmap() */
     166                 :            : #define RMAP_EXCLUSIVE 0x01
     167                 :            : #define RMAP_COMPOUND 0x02
     168                 :            : 
     169                 :            : /*
     170                 :            :  * rmap interfaces called when adding or removing pte of page
     171                 :            :  */
     172                 :            : void page_move_anon_rmap(struct page *, struct vm_area_struct *);
     173                 :            : void page_add_anon_rmap(struct page *, struct vm_area_struct *,
     174                 :            :                 unsigned long, bool);
     175                 :            : void do_page_add_anon_rmap(struct page *, struct vm_area_struct *,
     176                 :            :                            unsigned long, int);
     177                 :            : void page_add_new_anon_rmap(struct page *, struct vm_area_struct *,
     178                 :            :                 unsigned long, bool);
     179                 :            : void page_add_file_rmap(struct page *, bool);
     180                 :            : void page_remove_rmap(struct page *, bool);
     181                 :            : 
     182                 :            : void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *,
     183                 :            :                             unsigned long);
     184                 :            : void hugepage_add_new_anon_rmap(struct page *, struct vm_area_struct *,
     185                 :            :                                 unsigned long);
     186                 :            : 
     187                 :          3 : static inline void page_dup_rmap(struct page *page, bool compound)
     188                 :            : {
     189                 :          3 :         atomic_inc(compound ? compound_mapcount_ptr(page) : &page->_mapcount);
     190                 :          3 : }
     191                 :            : 
     192                 :            : /*
     193                 :            :  * Called from mm/vmscan.c to handle paging out
     194                 :            :  */
     195                 :            : int page_referenced(struct page *, int is_locked,
     196                 :            :                         struct mem_cgroup *memcg, unsigned long *vm_flags);
     197                 :            : 
     198                 :            : bool try_to_unmap(struct page *, enum ttu_flags flags);
     199                 :            : 
     200                 :            : /* Avoid racy checks */
     201                 :            : #define PVMW_SYNC               (1 << 0)
     202                 :            : /* Look for migarion entries rather than present PTEs */
     203                 :            : #define PVMW_MIGRATION          (1 << 1)
     204                 :            : 
     205                 :            : struct page_vma_mapped_walk {
     206                 :            :         struct page *page;
     207                 :            :         struct vm_area_struct *vma;
     208                 :            :         unsigned long address;
     209                 :            :         pmd_t *pmd;
     210                 :            :         pte_t *pte;
     211                 :            :         spinlock_t *ptl;
     212                 :            :         unsigned int flags;
     213                 :            : };
     214                 :            : 
     215                 :            : static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
     216                 :            : {
     217                 :            :         if (pvmw->pte)
     218                 :            :                 pte_unmap(pvmw->pte);
     219                 :          2 :         if (pvmw->ptl)
     220                 :            :                 spin_unlock(pvmw->ptl);
     221                 :            : }
     222                 :            : 
     223                 :            : bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw);
     224                 :            : 
     225                 :            : /*
     226                 :            :  * Used by swapoff to help locate where page is expected in vma.
     227                 :            :  */
     228                 :            : unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
     229                 :            : 
     230                 :            : /*
     231                 :            :  * Cleans the PTEs of shared mappings.
     232                 :            :  * (and since clean PTEs should also be readonly, write protects them too)
     233                 :            :  *
     234                 :            :  * returns the number of cleaned PTEs.
     235                 :            :  */
     236                 :            : int page_mkclean(struct page *);
     237                 :            : 
     238                 :            : /*
     239                 :            :  * called in munlock()/munmap() path to check for other vmas holding
     240                 :            :  * the page mlocked.
     241                 :            :  */
     242                 :            : void try_to_munlock(struct page *);
     243                 :            : 
     244                 :            : void remove_migration_ptes(struct page *old, struct page *new, bool locked);
     245                 :            : 
     246                 :            : /*
     247                 :            :  * Called by memory-failure.c to kill processes.
     248                 :            :  */
     249                 :            : struct anon_vma *page_lock_anon_vma_read(struct page *page);
     250                 :            : void page_unlock_anon_vma_read(struct anon_vma *anon_vma);
     251                 :            : int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
     252                 :            : 
     253                 :            : /*
     254                 :            :  * rmap_walk_control: To control rmap traversing for specific needs
     255                 :            :  *
     256                 :            :  * arg: passed to rmap_one() and invalid_vma()
     257                 :            :  * rmap_one: executed on each vma where page is mapped
     258                 :            :  * done: for checking traversing termination condition
     259                 :            :  * anon_lock: for getting anon_lock by optimized way rather than default
     260                 :            :  * invalid_vma: for skipping uninterested vma
     261                 :            :  */
     262                 :            : struct rmap_walk_control {
     263                 :            :         void *arg;
     264                 :            :         /*
     265                 :            :          * Return false if page table scanning in rmap_walk should be stopped.
     266                 :            :          * Otherwise, return true.
     267                 :            :          */
     268                 :            :         bool (*rmap_one)(struct page *page, struct vm_area_struct *vma,
     269                 :            :                                         unsigned long addr, void *arg);
     270                 :            :         int (*done)(struct page *page);
     271                 :            :         struct anon_vma *(*anon_lock)(struct page *page);
     272                 :            :         bool (*invalid_vma)(struct vm_area_struct *vma, void *arg);
     273                 :            : };
     274                 :            : 
     275                 :            : void rmap_walk(struct page *page, struct rmap_walk_control *rwc);
     276                 :            : void rmap_walk_locked(struct page *page, struct rmap_walk_control *rwc);
     277                 :            : 
     278                 :            : #else   /* !CONFIG_MMU */
     279                 :            : 
     280                 :            : #define anon_vma_init()         do {} while (0)
     281                 :            : #define anon_vma_prepare(vma)   (0)
     282                 :            : #define anon_vma_link(vma)      do {} while (0)
     283                 :            : 
     284                 :            : static inline int page_referenced(struct page *page, int is_locked,
     285                 :            :                                   struct mem_cgroup *memcg,
     286                 :            :                                   unsigned long *vm_flags)
     287                 :            : {
     288                 :            :         *vm_flags = 0;
     289                 :            :         return 0;
     290                 :            : }
     291                 :            : 
     292                 :            : #define try_to_unmap(page, refs) false
     293                 :            : 
     294                 :            : static inline int page_mkclean(struct page *page)
     295                 :            : {
     296                 :            :         return 0;
     297                 :            : }
     298                 :            : 
     299                 :            : 
     300                 :            : #endif  /* CONFIG_MMU */
     301                 :            : 
     302                 :            : #endif  /* _LINUX_RMAP_H */