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 *);
  77
  78 static inline struct anon_vma *page_anon_vma(struct page *page)
  79 {
  80         if (((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) !=
  81                                             PAGE_MAPPING_ANON)
  82                 return NULL;
  83         return page_rmapping(page);
  84 }
  85
  86 static inline void vma_lock_anon_vma(struct vm_area_struct *vma)
  87 {
  88         struct anon_vma *anon_vma = vma->anon_vma;
  89         if (anon_vma)
  90                 spin_lock(&anon_vma->root->lock);
  91 }
  92
  93 static inline void vma_unlock_anon_vma(struct vm_area_struct *vma)
  94 {
  95         struct anon_vma *anon_vma = vma->anon_vma;
  96         if (anon_vma)
  97                 spin_unlock(&anon_vma->root->lock);
  98 }
  99
 100 static inline void anon_vma_lock(struct anon_vma *anon_vma)
 101 {
 102         spin_lock(&anon_vma->root->lock);
 103 }
 104
 105 static inline void anon_vma_unlock(struct anon_vma *anon_vma)
 106 {
 107         spin_unlock(&anon_vma->root->lock);
 108 }
 109
 110 /*
 111  * anon_vma helper functions.
 112  */
 113 void anon_vma_init(void);       /* create anon_vma_cachep */
 114 int  anon_vma_prepare(struct vm_area_struct *);
 115 void unlink_anon_vmas(struct vm_area_struct *);
 116 int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *);
 117 int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *);
 118 void __anon_vma_link(struct vm_area_struct *);
 119 void anon_vma_free(struct anon_vma *);
 120
 121 static inline void anon_vma_merge(struct vm_area_struct *vma,
 122                                   struct vm_area_struct *next)
 123 {
 124         VM_BUG_ON(vma->anon_vma != next->anon_vma);
 125         unlink_anon_vmas(next);
 126 }
 127
 128 /*
 129  * rmap interfaces called when adding or removing pte of page
 130  */
 131 void page_move_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
 132 void page_add_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
 133 void do_page_add_anon_rmap(struct page *, struct vm_area_struct *,
 134                            unsigned long, int);
 135 void page_add_new_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
 136 void page_add_file_rmap(struct page *);
 137 void page_remove_rmap(struct page *);
 138
 139 void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *,
 140                             unsigned long);
 141 void hugepage_add_new_anon_rmap(struct page *, struct vm_area_struct *,
 142                                 unsigned long);
 143
 144 static inline void page_dup_rmap(struct page *page)
 145 {
 146         atomic_inc(&page->_mapcount);
 147 }
 148
 149 /*
 150  * Called from mm/vmscan.c to handle paging out
 151  */
 152 int page_referenced(struct page *, int is_locked,
 153                         struct mem_cgroup *cnt, unsigned long *vm_flags);
 154 int page_referenced_one(struct page *, struct vm_area_struct *,
 155         unsigned long address, unsigned int *mapcount, unsigned long *vm_flags);
 156
 157 enum ttu_flags {
 158         TTU_UNMAP = 0,                  /* unmap mode */
 159         TTU_MIGRATION = 1,              /* migration mode */
 160         TTU_MUNLOCK = 2,                /* munlock mode */
 161         TTU_ACTION_MASK = 0xff,
 162
 163         TTU_IGNORE_MLOCK = (1 << 8),    /* ignore mlock */
 164         TTU_IGNORE_ACCESS = (1 << 9),   /* don't age */
 165         TTU_IGNORE_HWPOISON = (1 << 10),/* corrupted page is recoverable */
 166 };
 167 #define TTU_ACTION(x) ((x) & TTU_ACTION_MASK)
 168
 169 bool is_vma_temporary_stack(struct vm_area_struct *vma);
 170
 171 int try_to_unmap(struct page *, enum ttu_flags flags);
 172 int try_to_unmap_one(struct page *, struct vm_area_struct *,
 173                         unsigned long address, enum ttu_flags flags);
 174
 175 /*
 176  * Called from mm/filemap_xip.c to unmap empty zero page
 177  */
 178 pte_t *__page_check_address(struct page *, struct mm_struct *,
 179                                 unsigned long, spinlock_t **, int);
 180
 181 static inline pte_t *page_check_address(struct page *page, struct mm_struct *mm,
 182                                         unsigned long address,
 183                                         spinlock_t **ptlp, int sync)
 184 {
 185         pte_t *ptep;
 186
 187         __cond_lock(*ptlp, ptep = __page_check_address(page, mm, address,
 188                                                        ptlp, sync));
 189         return ptep;
 190 }
 191
 192 /*
 193  * Used by swapoff to help locate where page is expected in vma.
 194  */
 195 unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
 196
 197 /*
 198  * Cleans the PTEs of shared mappings.
 199  * (and since clean PTEs should also be readonly, write protects them too)
 200  *
 201  * returns the number of cleaned PTEs.
 202  */
 203 int page_mkclean(struct page *);
 204
 205 /*
 206  * called in munlock()/munmap() path to check for other vmas holding
 207  * the page mlocked.
 208  */
 209 int try_to_munlock(struct page *);
 210
 211 /*
 212  * Called by memory-failure.c to kill processes.
 213  */
 214 struct anon_vma *__page_lock_anon_vma(struct page *page);
 215
 216 static inline struct anon_vma *page_lock_anon_vma(struct page *page)
 217 {
 218         struct anon_vma *anon_vma;
 219
 220         __cond_lock(RCU, anon_vma = __page_lock_anon_vma(page));
 221
 222         /* (void) is needed to make gcc happy */
 223         (void) __cond_lock(&anon_vma->root->lock, anon_vma);
 224
 225         return anon_vma;
 226 }
 227
 228 void page_unlock_anon_vma(struct anon_vma *anon_vma);
 229 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
 230
 231 /*
 232  * Called by migrate.c to remove migration ptes, but might be used more later.
 233  */
 234 int rmap_walk(struct page *page, int (*rmap_one)(struct page *,
 235                 struct vm_area_struct *, unsigned long, void *), void *arg);
 236
 237 #else   /* !CONFIG_MMU */
 238
 239 #define anon_vma_init()         do {} while (0)
 240 #define anon_vma_prepare(vma)   (0)
 241 #define anon_vma_link(vma)      do {} while (0)
 242
 243 static inline int page_referenced(struct page *page, int is_locked,
 244                                   struct mem_cgroup *cnt,
 245                                   unsigned long *vm_flags)
 246 {
 247         *vm_flags = 0;
 248         return 0;
 249 }
 250
 251 #define try_to_unmap(page, refs) SWAP_FAIL
 252
 253 static inline int page_mkclean(struct page *page)
 254 {
 255         return 0;
 256 }
 257
 258
 259 #endif  /* CONFIG_MMU */
 260
 261 /*
 262  * Return values of try_to_unmap
 263  */
 264 #define SWAP_SUCCESS    0
 265 #define SWAP_AGAIN      1
 266 #define SWAP_FAIL       2
 267 #define SWAP_MLOCK      3
 268
 269 #endif  /* _LINUX_RMAP_H */