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         spinlock_t lock;        /* Serialize access to vma list */
  29 #if defined(CONFIG_KSM) || defined(CONFIG_MIGRATION)
  30
  31         /*
  32          * The external_refcount is taken by either KSM or page migration
  33          * to take a reference to 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 external_refcount;
  40 #endif
  41         /*
  42          * NOTE: the LSB of the head.next is set by
  43          * mm_take_all_locks() _after_ taking the above lock. So the
  44          * head must only be read/written after taking the above lock
  45          * to be sure to see a valid next pointer. The LSB bit itself
  46          * is serialized by a system wide lock only visible to
  47          * mm_take_all_locks() (mm_all_locks_mutex).
  48          */
  49         struct list_head head;  /* Chain of private "related" vmas */
  50 };
  51
  52 /*
  53  * The copy-on-write semantics of fork mean that an anon_vma
  54  * can become associated with multiple processes. Furthermore,
  55  * each child process will have its own anon_vma, where new
  56  * pages for that process are instantiated.
  57  *
  58  * This structure allows us to find the anon_vmas associated
  59  * with a VMA, or the VMAs associated with an anon_vma.
  60  * The "same_vma" list contains the anon_vma_chains linking
  61  * all the anon_vmas associated with this VMA.
  62  * The "same_anon_vma" list contains the anon_vma_chains
  63  * which link all the VMAs associated with this anon_vma.
  64  */
  65 struct anon_vma_chain {
  66         struct vm_area_struct *vma;
  67         struct anon_vma *anon_vma;
  68         struct list_head same_vma;   /* locked by mmap_sem & page_table_lock */
  69         struct list_head same_anon_vma; /* locked by anon_vma->lock */
  70 };
  71
  72 #ifdef CONFIG_MMU
  73 #if defined(CONFIG_KSM) || defined(CONFIG_MIGRATION)
  74 static inline void anonvma_external_refcount_init(struct anon_vma *anon_vma)
  75 {
  76         atomic_set(&anon_vma->external_refcount, 0);
  77 }
  78
  79 static inline int anonvma_external_refcount(struct anon_vma *anon_vma)
  80 {
  81         return atomic_read(&anon_vma->external_refcount);
  82 }
  83 #else
  84 static inline void anonvma_external_refcount_init(struct anon_vma *anon_vma)
  85 {
  86 }
  87
  88 static inline int anonvma_external_refcount(struct anon_vma *anon_vma)
  89 {
  90         return 0;
  91 }
  92 #endif /* CONFIG_KSM */
  93
  94 static inline struct anon_vma *page_anon_vma(struct page *page)
  95 {
  96         if (((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) !=
  97                                             PAGE_MAPPING_ANON)
  98                 return NULL;
  99         return page_rmapping(page);
 100 }
 101
 102 static inline void anon_vma_lock(struct vm_area_struct *vma)
 103 {
 104         struct anon_vma *anon_vma = vma->anon_vma;
 105         if (anon_vma)
 106                 spin_lock(&anon_vma->lock);
 107 }
 108
 109 static inline void anon_vma_unlock(struct vm_area_struct *vma)
 110 {
 111         struct anon_vma *anon_vma = vma->anon_vma;
 112         if (anon_vma)
 113                 spin_unlock(&anon_vma->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 void anon_vma_free(struct anon_vma *);
 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 /*
 135  * rmap interfaces called when adding or removing pte of page
 136  */
 137 void page_move_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
 138 void page_add_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
 139 void page_add_new_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
 140 void page_add_file_rmap(struct page *);
 141 void page_remove_rmap(struct page *);
 142
 143 static inline void page_dup_rmap(struct page *page)
 144 {
 145         atomic_inc(&page->_mapcount);
 146 }
 147
 148 /*
 149  * Called from mm/vmscan.c to handle paging out
 150  */
 151 int page_referenced(struct page *, int is_locked,
 152                         struct mem_cgroup *cnt, unsigned long *vm_flags);
 153 int page_referenced_one(struct page *, struct vm_area_struct *,
 154         unsigned long address, unsigned int *mapcount, unsigned long *vm_flags);
 155
 156 enum ttu_flags {
 157         TTU_UNMAP = 0,                  /* unmap mode */
 158         TTU_MIGRATION = 1,              /* migration mode */
 159         TTU_MUNLOCK = 2,                /* munlock mode */
 160         TTU_ACTION_MASK = 0xff,
 161
 162         TTU_IGNORE_MLOCK = (1 << 8),    /* ignore mlock */
 163         TTU_IGNORE_ACCESS = (1 << 9),   /* don't age */
 164         TTU_IGNORE_HWPOISON = (1 << 10),/* corrupted page is recoverable */
 165 };
 166 #define TTU_ACTION(x) ((x) & TTU_ACTION_MASK)
 167
 168 int try_to_unmap(struct page *, enum ttu_flags flags);
 169 int try_to_unmap_one(struct page *, struct vm_area_struct *,
 170                         unsigned long address, enum ttu_flags flags);
 171
 172 /*
 173  * Called from mm/filemap_xip.c to unmap empty zero page
 174  */
 175 pte_t *page_check_address(struct page *, struct mm_struct *,
 176                                 unsigned long, spinlock_t **, int);
 177
 178 /*
 179  * Used by swapoff to help locate where page is expected in vma.
 180  */
 181 unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
 182
 183 /*
 184  * Cleans the PTEs of shared mappings.
 185  * (and since clean PTEs should also be readonly, write protects them too)
 186  *
 187  * returns the number of cleaned PTEs.
 188  */
 189 int page_mkclean(struct page *);
 190
 191 /*
 192  * called in munlock()/munmap() path to check for other vmas holding
 193  * the page mlocked.
 194  */
 195 int try_to_munlock(struct page *);
 196
 197 /*
 198  * Called by memory-failure.c to kill processes.
 199  */
 200 struct anon_vma *page_lock_anon_vma(struct page *page);
 201 void page_unlock_anon_vma(struct anon_vma *anon_vma);
 202 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
 203
 204 /*
 205  * Called by migrate.c to remove migration ptes, but might be used more later.
 206  */
 207 int rmap_walk(struct page *page, int (*rmap_one)(struct page *,
 208                 struct vm_area_struct *, unsigned long, void *), void *arg);
 209
 210 #else   /* !CONFIG_MMU */
 211
 212 #define anon_vma_init()         do {} while (0)
 213 #define anon_vma_prepare(vma)   (0)
 214 #define anon_vma_link(vma)      do {} while (0)
 215
 216 static inline int page_referenced(struct page *page, int is_locked,
 217                                   struct mem_cgroup *cnt,
 218                                   unsigned long *vm_flags)
 219 {
 220         *vm_flags = 0;
 221         return 0;
 222 }
 223
 224 #define try_to_unmap(page, refs) SWAP_FAIL
 225
 226 static inline int page_mkclean(struct page *page)
 227 {
 228         return 0;
 229 }
 230
 231
 232 #endif  /* CONFIG_MMU */
 233
 234 /*
 235  * Return values of try_to_unmap
 236  */
 237 #define SWAP_SUCCESS    0
 238 #define SWAP_AGAIN      1
 239 #define SWAP_FAIL       2
 240 #define SWAP_MLOCK      3
 241
 242 #endif  /* _LINUX_RMAP_H */