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/spinlock.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         spinlock_t lock;        /* 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->lock */
  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                 spin_lock(&anon_vma->root->lock);
  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                 spin_unlock(&anon_vma->root->lock);
 104 }
 105
 106 static inline void anon_vma_lock(struct anon_vma *anon_vma)
 107 {
 108         spin_lock(&anon_vma->root->lock);
 109 }
 110
 111 static inline void anon_vma_unlock(struct anon_vma *anon_vma)
 112 {
 113         spin_unlock(&anon_vma->root->lock);
 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 int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *);
 124 void __anon_vma_link(struct vm_area_struct *);
 125
 126 static inline void anon_vma_merge(struct vm_area_struct *vma,
 127                                   struct vm_area_struct *next)
 128 {
 129         VM_BUG_ON(vma->anon_vma != next->anon_vma);
 130         unlink_anon_vmas(next);
 131 }
 132
 133 struct anon_vma *page_get_anon_vma(struct page *page);
 134
 135 /*
 136  * rmap interfaces called when adding or removing pte of page
 137  */
 138 void page_move_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
 139 void page_add_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
 140 void do_page_add_anon_rmap(struct page *, struct vm_area_struct *,
 141                            unsigned long, int);
 142 void page_add_new_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
 143 void page_add_file_rmap(struct page *);
 144 void page_remove_rmap(struct page *);
 145
 146 void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *,
 147                             unsigned long);
 148 void hugepage_add_new_anon_rmap(struct page *, struct vm_area_struct *,
 149                                 unsigned long);
 150
 151 static inline void page_dup_rmap(struct page *page)
 152 {
 153         atomic_inc(&page->_mapcount);
 154 }
 155
 156 /*
 157  * Called from mm/vmscan.c to handle paging out
 158  */
 159 int page_referenced(struct page *, int is_locked,
 160                         struct mem_cgroup *cnt, unsigned long *vm_flags);
 161 int page_referenced_one(struct page *, struct vm_area_struct *,
 162         unsigned long address, unsigned int *mapcount, unsigned long *vm_flags);
 163
 164 enum ttu_flags {
 165         TTU_UNMAP = 0,                  /* unmap mode */
 166         TTU_MIGRATION = 1,              /* migration mode */
 167         TTU_MUNLOCK = 2,                /* munlock mode */
 168         TTU_ACTION_MASK = 0xff,
 169
 170         TTU_IGNORE_MLOCK = (1 << 8),    /* ignore mlock */
 171         TTU_IGNORE_ACCESS = (1 << 9),   /* don't age */
 172         TTU_IGNORE_HWPOISON = (1 << 10),/* corrupted page is recoverable */
 173 };
 174 #define TTU_ACTION(x) ((x) & TTU_ACTION_MASK)
 175
 176 bool is_vma_temporary_stack(struct vm_area_struct *vma);
 177
 178 int try_to_unmap(struct page *, enum ttu_flags flags);
 179 int try_to_unmap_one(struct page *, struct vm_area_struct *,
 180                         unsigned long address, enum ttu_flags flags);
 181
 182 /*
 183  * Called from mm/filemap_xip.c to unmap empty zero page
 184  */
 185 pte_t *__page_check_address(struct page *, struct mm_struct *,
 186                                 unsigned long, spinlock_t **, int);
 187
 188 static inline pte_t *page_check_address(struct page *page, struct mm_struct *mm,
 189                                         unsigned long address,
 190                                         spinlock_t **ptlp, int sync)
 191 {
 192         pte_t *ptep;
 193
 194         __cond_lock(*ptlp, ptep = __page_check_address(page, mm, address,
 195                                                        ptlp, sync));
 196         return ptep;
 197 }
 198
 199 /*
 200  * Used by swapoff to help locate where page is expected in vma.
 201  */
 202 unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
 203
 204 /*
 205  * Cleans the PTEs of shared mappings.
 206  * (and since clean PTEs should also be readonly, write protects them too)
 207  *
 208  * returns the number of cleaned PTEs.
 209  */
 210 int page_mkclean(struct page *);
 211
 212 /*
 213  * called in munlock()/munmap() path to check for other vmas holding
 214  * the page mlocked.
 215  */
 216 int try_to_munlock(struct page *);
 217
 218 /*
 219  * Called by memory-failure.c to kill processes.
 220  */
 221 struct anon_vma *__page_lock_anon_vma(struct page *page);
 222
 223 static inline struct anon_vma *page_lock_anon_vma(struct page *page)
 224 {
 225         struct anon_vma *anon_vma;
 226
 227         __cond_lock(RCU, anon_vma = __page_lock_anon_vma(page));
 228
 229         /* (void) is needed to make gcc happy */
 230         (void) __cond_lock(&anon_vma->root->lock, anon_vma);
 231
 232         return anon_vma;
 233 }
 234
 235 void page_unlock_anon_vma(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 *cnt,
 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 */