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/mutex.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 mutex mutex;     /* Serialize access to vma 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 head.next is set by
  41          * mm_take_all_locks() _after_ taking the above lock. So the
  42          * head 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 list_head head;  /* Chain 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 "same_anon_vma" list contains 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 list_head same_anon_vma; /* locked by anon_vma->mutex */
  68 };
  69
  70 #ifdef CONFIG_MMU
  71 static inline void get_anon_vma(struct anon_vma *anon_vma)
  72 {
  73         atomic_inc(&anon_vma->refcount);
  74 }
  75
  76 void __put_anon_vma(struct anon_vma *anon_vma);
  77
  78 static inline void put_anon_vma(struct anon_vma *anon_vma)
  79 {
  80         if (atomic_dec_and_test(&anon_vma->refcount))
  81                 __put_anon_vma(anon_vma);
  82 }
  83
  84 static inline struct anon_vma *page_anon_vma(struct page *page)
  85 {
  86         if (((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) !=
  87                                             PAGE_MAPPING_ANON)
  88                 return NULL;
  89         return page_rmapping(page);
  90 }
  91
  92 static inline void vma_lock_anon_vma(struct vm_area_struct *vma)
  93 {
  94         struct anon_vma *anon_vma = vma->anon_vma;
  95         if (anon_vma)
  96                 mutex_lock(&anon_vma->root->mutex);
  97 }
  98
  99 static inline void vma_unlock_anon_vma(struct vm_area_struct *vma)
 100 {
 101         struct anon_vma *anon_vma = vma->anon_vma;
 102         if (anon_vma)
 103                 mutex_unlock(&anon_vma->root->mutex);
 104 }
 105
 106 static inline void anon_vma_lock(struct anon_vma *anon_vma)
 107 {
 108         mutex_lock(&anon_vma->root->mutex);
 109 }
 110
 111 static inline void anon_vma_unlock(struct anon_vma *anon_vma)
 112 {
 113         mutex_unlock(&anon_vma->root->mutex);
 114 }
 115
 116 /*
 117  * anon_vma helper functions.
 118  */
 119 void anon_vma_init(void);       /* create anon_vma_cachep */
 120 int  anon_vma_prepare(struct vm_area_struct *);
 121 void unlink_anon_vmas(struct vm_area_struct *);
 122 int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *);
 123 void anon_vma_moveto_tail(struct vm_area_struct *);
 124 int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *);
 125 void __anon_vma_link(struct vm_area_struct *);
 126
 127 static inline void anon_vma_merge(struct vm_area_struct *vma,
 128                                   struct vm_area_struct *next)
 129 {
 130         VM_BUG_ON(vma->anon_vma != next->anon_vma);
 131         unlink_anon_vmas(next);
 132 }
 133
 134 struct anon_vma *page_get_anon_vma(struct page *page);
 135
 136 /*
 137  * rmap interfaces called when adding or removing pte of page
 138  */
 139 void page_move_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
 140 void page_add_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
 141 void do_page_add_anon_rmap(struct page *, struct vm_area_struct *,
 142                            unsigned long, int);
 143 void page_add_new_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
 144 void page_add_file_rmap(struct page *);
 145 void page_remove_rmap(struct page *);
 146
 147 void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *,
 148                             unsigned long);
 149 void hugepage_add_new_anon_rmap(struct page *, struct vm_area_struct *,
 150                                 unsigned long);
 151
 152 static inline void page_dup_rmap(struct page *page)
 153 {
 154         atomic_inc(&page->_mapcount);
 155 }
 156
 157 /*
 158  * Called from mm/vmscan.c to handle paging out
 159  */
 160 int page_referenced(struct page *, int is_locked,
 161                         struct mem_cgroup *cnt, unsigned long *vm_flags);
 162 int page_referenced_one(struct page *, struct vm_area_struct *,
 163         unsigned long address, unsigned int *mapcount, unsigned long *vm_flags);
 164
 165 enum ttu_flags {
 166         TTU_UNMAP = 0,                  /* unmap mode */
 167         TTU_MIGRATION = 1,              /* migration mode */
 168         TTU_MUNLOCK = 2,                /* munlock mode */
 169         TTU_ACTION_MASK = 0xff,
 170
 171         TTU_IGNORE_MLOCK = (1 << 8),    /* ignore mlock */
 172         TTU_IGNORE_ACCESS = (1 << 9),   /* don't age */
 173         TTU_IGNORE_HWPOISON = (1 << 10),/* corrupted page is recoverable */
 174 };
 175 #define TTU_ACTION(x) ((x) & TTU_ACTION_MASK)
 176
 177 bool is_vma_temporary_stack(struct vm_area_struct *vma);
 178
 179 int try_to_unmap(struct page *, enum ttu_flags flags);
 180 int try_to_unmap_one(struct page *, struct vm_area_struct *,
 181                         unsigned long address, enum ttu_flags flags);
 182
 183 /*
 184  * Called from mm/filemap_xip.c to unmap empty zero page
 185  */
 186 pte_t *__page_check_address(struct page *, struct mm_struct *,
 187                                 unsigned long, spinlock_t **, int);
 188
 189 static inline pte_t *page_check_address(struct page *page, struct mm_struct *mm,
 190                                         unsigned long address,
 191                                         spinlock_t **ptlp, int sync)
 192 {
 193         pte_t *ptep;
 194
 195         __cond_lock(*ptlp, ptep = __page_check_address(page, mm, address,
 196                                                        ptlp, sync));
 197         return ptep;
 198 }
 199
 200 /*
 201  * Used by swapoff to help locate where page is expected in vma.
 202  */
 203 unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
 204
 205 /*
 206  * Cleans the PTEs of shared mappings.
 207  * (and since clean PTEs should also be readonly, write protects them too)
 208  *
 209  * returns the number of cleaned PTEs.
 210  */
 211 int page_mkclean(struct page *);
 212
 213 /*
 214  * called in munlock()/munmap() path to check for other vmas holding
 215  * the page mlocked.
 216  */
 217 int try_to_munlock(struct page *);
 218
 219 /*
 220  * Called by memory-failure.c to kill processes.
 221  */
 222 struct anon_vma *page_lock_anon_vma(struct page *page);
 223 void page_unlock_anon_vma(struct anon_vma *anon_vma);
 224 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
 225
 226 /*
 227  * Called by migrate.c to remove migration ptes, but might be used more later.
 228  */
 229 int rmap_walk(struct page *page, int (*rmap_one)(struct page *,
 230                 struct vm_area_struct *, unsigned long, void *), void *arg);
 231
 232 #else   /* !CONFIG_MMU */
 233
 234 #define anon_vma_init()         do {} while (0)
 235 #define anon_vma_prepare(vma)   (0)
 236 #define anon_vma_link(vma)      do {} while (0)
 237
 238 static inline int page_referenced(struct page *page, int is_locked,
 239                                   struct mem_cgroup *cnt,
 240                                   unsigned long *vm_flags)
 241 {
 242         *vm_flags = 0;
 243         return 0;
 244 }
 245
 246 #define try_to_unmap(page, refs) SWAP_FAIL
 247
 248 static inline int page_mkclean(struct page *page)
 249 {
 250         return 0;
 251 }
 252
 253
 254 #endif  /* CONFIG_MMU */
 255
 256 /*
 257  * Return values of try_to_unmap
 258  */
 259 #define SWAP_SUCCESS    0
 260 #define SWAP_AGAIN      1
 261 #define SWAP_FAIL       2
 262 #define SWAP_MLOCK      3
 263
 264 #endif  /* _LINUX_RMAP_H */