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         struct anon_vma *root;  /* Root of this anon_vma tree */
  30 #if defined(CONFIG_KSM) || defined(CONFIG_MIGRATION)
  31
  32         /*
  33          * The external_refcount is taken by either KSM or page migration
  34          * to take a reference to an anon_vma when there is no
  35          * guarantee that the vma of page tables will exist for
  36          * the duration of the operation. A caller that takes
  37          * the reference is responsible for clearing up the
  38          * anon_vma if they are the last user on release
  39          */
  40         atomic_t external_refcount;
  41 #endif
  42         /*
  43          * NOTE: the LSB of the head.next is set by
  44          * mm_take_all_locks() _after_ taking the above lock. So the
  45          * head must only be read/written after taking the above lock
  46          * to be sure to see a valid next pointer. The LSB bit itself
  47          * is serialized by a system wide lock only visible to
  48          * mm_take_all_locks() (mm_all_locks_mutex).
  49          */
  50         struct list_head head;  /* Chain of private "related" vmas */
  51 };
  52
  53 /*
  54  * The copy-on-write semantics of fork mean that an anon_vma
  55  * can become associated with multiple processes. Furthermore,
  56  * each child process will have its own anon_vma, where new
  57  * pages for that process are instantiated.
  58  *
  59  * This structure allows us to find the anon_vmas associated
  60  * with a VMA, or the VMAs associated with an anon_vma.
  61  * The "same_vma" list contains the anon_vma_chains linking
  62  * all the anon_vmas associated with this VMA.
  63  * The "same_anon_vma" list contains the anon_vma_chains
  64  * which link all the VMAs associated with this anon_vma.
  65  */
  66 struct anon_vma_chain {
  67         struct vm_area_struct *vma;
  68         struct anon_vma *anon_vma;
  69         struct list_head same_vma;   /* locked by mmap_sem & page_table_lock */
  70         struct list_head same_anon_vma; /* locked by anon_vma->lock */
  71 };
  72
  73 #ifdef CONFIG_MMU
  74 #if defined(CONFIG_KSM) || defined(CONFIG_MIGRATION)
  75 static inline void anonvma_external_refcount_init(struct anon_vma *anon_vma)
  76 {
  77         atomic_set(&anon_vma->external_refcount, 0);
  78 }
  79
  80 static inline int anonvma_external_refcount(struct anon_vma *anon_vma)
  81 {
  82         return atomic_read(&anon_vma->external_refcount);
  83 }
  84
  85 static inline void get_anon_vma(struct anon_vma *anon_vma)
  86 {
  87         atomic_inc(&anon_vma->external_refcount);
  88 }
  89
  90 void drop_anon_vma(struct anon_vma *);
  91 #else
  92 static inline void anonvma_external_refcount_init(struct anon_vma *anon_vma)
  93 {
  94 }
  95
  96 static inline int anonvma_external_refcount(struct anon_vma *anon_vma)
  97 {
  98         return 0;
  99 }
 100
 101 static inline void get_anon_vma(struct anon_vma *anon_vma)
 102 {
 103 }
 104
 105 static inline void drop_anon_vma(struct anon_vma *anon_vma)
 106 {
 107 }
 108 #endif /* CONFIG_KSM */
 109
 110 static inline struct anon_vma *page_anon_vma(struct page *page)
 111 {
 112         if (((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) !=
 113                                             PAGE_MAPPING_ANON)
 114                 return NULL;
 115         return page_rmapping(page);
 116 }
 117
 118 static inline void vma_lock_anon_vma(struct vm_area_struct *vma)
 119 {
 120         struct anon_vma *anon_vma = vma->anon_vma;
 121         if (anon_vma)
 122                 spin_lock(&anon_vma->root->lock);
 123 }
 124
 125 static inline void vma_unlock_anon_vma(struct vm_area_struct *vma)
 126 {
 127         struct anon_vma *anon_vma = vma->anon_vma;
 128         if (anon_vma)
 129                 spin_unlock(&anon_vma->root->lock);
 130 }
 131
 132 static inline void anon_vma_lock(struct anon_vma *anon_vma)
 133 {
 134         spin_lock(&anon_vma->root->lock);
 135 }
 136
 137 static inline void anon_vma_unlock(struct anon_vma *anon_vma)
 138 {
 139         spin_unlock(&anon_vma->root->lock);
 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 void __anon_vma_link(struct vm_area_struct *);
 151 void anon_vma_free(struct anon_vma *);
 152
 153 static inline void anon_vma_merge(struct vm_area_struct *vma,
 154                                   struct vm_area_struct *next)
 155 {
 156         VM_BUG_ON(vma->anon_vma != next->anon_vma);
 157         unlink_anon_vmas(next);
 158 }
 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 static inline void page_dup_rmap(struct page *page)
 172 {
 173         atomic_inc(&page->_mapcount);
 174 }
 175
 176 /*
 177  * Called from mm/vmscan.c to handle paging out
 178  */
 179 int page_referenced(struct page *, int is_locked,
 180                         struct mem_cgroup *cnt, unsigned long *vm_flags);
 181 int page_referenced_one(struct page *, struct vm_area_struct *,
 182         unsigned long address, unsigned int *mapcount, unsigned long *vm_flags);
 183
 184 enum ttu_flags {
 185         TTU_UNMAP = 0,                  /* unmap mode */
 186         TTU_MIGRATION = 1,              /* migration mode */
 187         TTU_MUNLOCK = 2,                /* munlock mode */
 188         TTU_ACTION_MASK = 0xff,
 189
 190         TTU_IGNORE_MLOCK = (1 << 8),    /* ignore mlock */
 191         TTU_IGNORE_ACCESS = (1 << 9),   /* don't age */
 192         TTU_IGNORE_HWPOISON = (1 << 10),/* corrupted page is recoverable */
 193 };
 194 #define TTU_ACTION(x) ((x) & TTU_ACTION_MASK)
 195
 196 int try_to_unmap(struct page *, enum ttu_flags flags);
 197 int try_to_unmap_one(struct page *, struct vm_area_struct *,
 198                         unsigned long address, enum ttu_flags flags);
 199
 200 /*
 201  * Called from mm/filemap_xip.c to unmap empty zero page
 202  */
 203 pte_t *page_check_address(struct page *, struct mm_struct *,
 204                                 unsigned long, spinlock_t **, int);
 205
 206 /*
 207  * Used by swapoff to help locate where page is expected in vma.
 208  */
 209 unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
 210
 211 /*
 212  * Cleans the PTEs of shared mappings.
 213  * (and since clean PTEs should also be readonly, write protects them too)
 214  *
 215  * returns the number of cleaned PTEs.
 216  */
 217 int page_mkclean(struct page *);
 218
 219 /*
 220  * called in munlock()/munmap() path to check for other vmas holding
 221  * the page mlocked.
 222  */
 223 int try_to_munlock(struct page *);
 224
 225 /*
 226  * Called by memory-failure.c to kill processes.
 227  */
 228 struct anon_vma *page_lock_anon_vma(struct page *page);
 229 void page_unlock_anon_vma(struct anon_vma *anon_vma);
 230 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
 231
 232 /*
 233  * Called by migrate.c to remove migration ptes, but might be used more later.
 234  */
 235 int rmap_walk(struct page *page, int (*rmap_one)(struct page *,
 236                 struct vm_area_struct *, unsigned long, void *), void *arg);
 237
 238 #else   /* !CONFIG_MMU */
 239
 240 #define anon_vma_init()         do {} while (0)
 241 #define anon_vma_prepare(vma)   (0)
 242 #define anon_vma_link(vma)      do {} while (0)
 243
 244 static inline int page_referenced(struct page *page, int is_locked,
 245                                   struct mem_cgroup *cnt,
 246                                   unsigned long *vm_flags)
 247 {
 248         *vm_flags = 0;
 249         return 0;
 250 }
 251
 252 #define try_to_unmap(page, refs) SWAP_FAIL
 253
 254 static inline int page_mkclean(struct page *page)
 255 {
 256         return 0;
 257 }
 258
 259
 260 #endif  /* CONFIG_MMU */
 261
 262 /*
 263  * Return values of try_to_unmap
 264  */
 265 #define SWAP_SUCCESS    0
 266 #define SWAP_AGAIN      1
 267 #define SWAP_FAIL       2
 268 #define SWAP_MLOCK      3
 269
 270 #endif  /* _LINUX_RMAP_H */