include/linux/rmap.h

   1 #ifndef _LINUX_RMAP_H
   2 #define _LINUX_RMAP_H
   3 /*
   4  * Declarations for Reverse Mapping functions in mm/rmap.c
   5  */
   6
   7 #include <linux/list.h>
   8 #include <linux/slab.h>
   9 #include <linux/mm.h>
  10 #include <linux/rwsem.h>
  11 #include <linux/memcontrol.h>
  12
  13 /*
  14  * The anon_vma heads a list of private "related" vmas, to scan if
  15  * an anonymous page pointing to this anon_vma needs to be unmapped:
  16  * the vmas on the list will be related by forking, or by splitting.
  17  *
  18  * Since vmas come and go as they are split and merged (particularly
  19  * in mprotect), the mapping field of an anonymous page cannot point
  20  * directly to a vma: instead it points to an anon_vma, on whose list
  21  * the related vmas can be easily linked or unlinked.
  22  *
  23  * After unlinking the last vma on the list, we must garbage collect
  24  * the anon_vma object itself: we're guaranteed no page can be
  25  * pointing to this anon_vma once its vma list is empty.
  26  */
  27 struct anon_vma {
  28         struct anon_vma *root;          /* Root of this anon_vma tree */
  29         struct rw_semaphore rwsem;      /* W: modification, R: walking the list */
  30         /*
  31          * The refcount is taken on an anon_vma when there is no
  32          * guarantee that the vma of page tables will exist for
  33          * the duration of the operation. A caller that takes
  34          * the reference is responsible for clearing up the
  35          * anon_vma if they are the last user on release
  36          */
  37         atomic_t refcount;
  38
  39         /*
  40          * NOTE: the LSB of the rb_root.rb_node is set by
  41          * mm_take_all_locks() _after_ taking the above lock. So the
  42          * rb_root must only be read/written after taking the above lock
  43          * to be sure to see a valid next pointer. The LSB bit itself
  44          * is serialized by a system wide lock only visible to
  45          * mm_take_all_locks() (mm_all_locks_mutex).
  46          */
  47         struct rb_root rb_root; /* Interval tree of private "related" vmas */
  48 };
  49
  50 /*
  51  * The copy-on-write semantics of fork mean that an anon_vma
  52  * can become associated with multiple processes. Furthermore,
  53  * each child process will have its own anon_vma, where new
  54  * pages for that process are instantiated.
  55  *
  56  * This structure allows us to find the anon_vmas associated
  57  * with a VMA, or the VMAs associated with an anon_vma.
  58  * The "same_vma" list contains the anon_vma_chains linking
  59  * all the anon_vmas associated with this VMA.
  60  * The "rb" field indexes on an interval tree the anon_vma_chains
  61  * which link all the VMAs associated with this anon_vma.
  62  */
  63 struct anon_vma_chain {
  64         struct vm_area_struct *vma;
  65         struct anon_vma *anon_vma;
  66         struct list_head same_vma;   /* locked by mmap_sem & page_table_lock */
  67         struct rb_node rb;                      /* locked by anon_vma->rwsem */
  68         unsigned long rb_subtree_last;
  69 #ifdef CONFIG_DEBUG_VM_RB
  70         unsigned long cached_vma_start, cached_vma_last;
  71 #endif
  72 };
  73
  74 enum ttu_flags {
  75         TTU_UNMAP = 0,                  /* unmap mode */
  76         TTU_MIGRATION = 1,              /* migration mode */
  77         TTU_MUNLOCK = 2,                /* munlock mode */
  78         TTU_ACTION_MASK = 0xff,
  79
  80         TTU_IGNORE_MLOCK = (1 << 8),    /* ignore mlock */
  81         TTU_IGNORE_ACCESS = (1 << 9),   /* don't age */
  82         TTU_IGNORE_HWPOISON = (1 << 10),/* corrupted page is recoverable */
  83 };
  84
  85 #ifdef CONFIG_MMU
  86 static inline void get_anon_vma(struct anon_vma *anon_vma)
  87 {
  88         atomic_inc(&anon_vma->refcount);
  89 }
  90
  91 void __put_anon_vma(struct anon_vma *anon_vma);
  92
  93 static inline void put_anon_vma(struct anon_vma *anon_vma)
  94 {
  95         if (atomic_dec_and_test(&anon_vma->refcount))
  96                 __put_anon_vma(anon_vma);
  97 }
  98
  99 static inline struct anon_vma *page_anon_vma(struct page *page)
 100 {
 101         if (((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) !=
 102                                             PAGE_MAPPING_ANON)
 103                 return NULL;
 104         return page_rmapping(page);
 105 }
 106
 107 static inline void vma_lock_anon_vma(struct vm_area_struct *vma)
 108 {
 109         struct anon_vma *anon_vma = vma->anon_vma;
 110         if (anon_vma)
 111                 down_write(&anon_vma->root->rwsem);
 112 }
 113
 114 static inline void vma_unlock_anon_vma(struct vm_area_struct *vma)
 115 {
 116         struct anon_vma *anon_vma = vma->anon_vma;
 117         if (anon_vma)
 118                 up_write(&anon_vma->root->rwsem);
 119 }
 120
 121 static inline void anon_vma_lock_write(struct anon_vma *anon_vma)
 122 {
 123         down_write(&anon_vma->root->rwsem);
 124 }
 125
 126 static inline void anon_vma_unlock_write(struct anon_vma *anon_vma)
 127 {
 128         up_write(&anon_vma->root->rwsem);
 129 }
 130
 131 static inline void anon_vma_lock_read(struct anon_vma *anon_vma)
 132 {
 133         down_read(&anon_vma->root->rwsem);
 134 }
 135
 136 static inline void anon_vma_unlock_read(struct anon_vma *anon_vma)
 137 {
 138         up_read(&anon_vma->root->rwsem);
 139 }
 140
 141
 142 /*
 143  * anon_vma helper functions.
 144  */
 145 void anon_vma_init(void);       /* create anon_vma_cachep */
 146 int  anon_vma_prepare(struct vm_area_struct *);
 147 void unlink_anon_vmas(struct vm_area_struct *);
 148 int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *);
 149 int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *);
 150
 151 static inline void anon_vma_merge(struct vm_area_struct *vma,
 152                                   struct vm_area_struct *next)
 153 {
 154         VM_BUG_ON(vma->anon_vma != next->anon_vma);
 155         unlink_anon_vmas(next);
 156 }
 157
 158 struct anon_vma *page_get_anon_vma(struct page *page);
 159
 160 /*
 161  * rmap interfaces called when adding or removing pte of page
 162  */
 163 void page_move_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
 164 void page_add_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
 165 void do_page_add_anon_rmap(struct page *, struct vm_area_struct *,
 166                            unsigned long, int);
 167 void page_add_new_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
 168 void page_add_file_rmap(struct page *);
 169 void page_remove_rmap(struct page *);
 170
 171 void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *,
 172                             unsigned long);
 173 void hugepage_add_new_anon_rmap(struct page *, struct vm_area_struct *,
 174                                 unsigned long);
 175
 176 static inline void page_dup_rmap(struct page *page)
 177 {
 178         atomic_inc(&page->_mapcount);
 179 }
 180
 181 /*
 182  * Called from mm/vmscan.c to handle paging out
 183  */
 184 int page_referenced(struct page *, int is_locked,
 185                         struct mem_cgroup *memcg, unsigned long *vm_flags);
 186 int page_referenced_one(struct page *, struct vm_area_struct *,
 187         unsigned long address, unsigned int *mapcount, unsigned long *vm_flags);
 188
 189 #define TTU_ACTION(x) ((x) & TTU_ACTION_MASK)
 190
 191 int try_to_unmap(struct page *, enum ttu_flags flags);
 192 int try_to_unmap_one(struct page *, struct vm_area_struct *,
 193                         unsigned long address, enum ttu_flags flags);
 194
 195 /*
 196  * Called from mm/filemap_xip.c to unmap empty zero page
 197  */
 198 pte_t *__page_check_address(struct page *, struct mm_struct *,
 199                                 unsigned long, spinlock_t **, int);
 200
 201 static inline pte_t *page_check_address(struct page *page, struct mm_struct *mm,
 202                                         unsigned long address,
 203                                         spinlock_t **ptlp, int sync)
 204 {
 205         pte_t *ptep;
 206
 207         __cond_lock(*ptlp, ptep = __page_check_address(page, mm, address,
 208                                                        ptlp, sync));
 209         return ptep;
 210 }
 211
 212 /*
 213  * Used by swapoff to help locate where page is expected in vma.
 214  */
 215 unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
 216
 217 /*
 218  * Cleans the PTEs of shared mappings.
 219  * (and since clean PTEs should also be readonly, write protects them too)
 220  *
 221  * returns the number of cleaned PTEs.
 222  */
 223 int page_mkclean(struct page *);
 224
 225 /*
 226  * called in munlock()/munmap() path to check for other vmas holding
 227  * the page mlocked.
 228  */
 229 int try_to_munlock(struct page *);
 230
 231 /*
 232  * Called by memory-failure.c to kill processes.
 233  */
 234 struct anon_vma *page_lock_anon_vma_read(struct page *page);
 235 void page_unlock_anon_vma_read(struct anon_vma *anon_vma);
 236 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
 237
 238 /*
 239  * Called by migrate.c to remove migration ptes, but might be used more later.
 240  */
 241 int rmap_walk(struct page *page, int (*rmap_one)(struct page *,
 242                 struct vm_area_struct *, unsigned long, void *), void *arg);
 243
 244 #else   /* !CONFIG_MMU */
 245
 246 #define anon_vma_init()         do {} while (0)
 247 #define anon_vma_prepare(vma)   (0)
 248 #define anon_vma_link(vma)      do {} while (0)
 249
 250 static inline int page_referenced(struct page *page, int is_locked,
 251                                   struct mem_cgroup *memcg,
 252                                   unsigned long *vm_flags)
 253 {
 254         *vm_flags = 0;
 255         return 0;
 256 }
 257
 258 #define try_to_unmap(page, refs) SWAP_FAIL
 259
 260 static inline int page_mkclean(struct page *page)
 261 {
 262         return 0;
 263 }
 264
 265
 266 #endif  /* CONFIG_MMU */
 267
 268 /*
 269  * Return values of try_to_unmap
 270  */
 271 #define SWAP_SUCCESS    0
 272 #define SWAP_AGAIN      1
 273 #define SWAP_FAIL       2
 274 #define SWAP_MLOCK      3
 275
 276 #endif  /* _LINUX_RMAP_H */