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 #ifdef CONFIG_KSM
  30         atomic_t ksm_refcount;
  31 #endif
  32         /*
  33          * NOTE: the LSB of the head.next is set by
  34          * mm_take_all_locks() _after_ taking the above lock. So the
  35          * head must only be read/written after taking the above lock
  36          * to be sure to see a valid next pointer. The LSB bit itself
  37          * is serialized by a system wide lock only visible to
  38          * mm_take_all_locks() (mm_all_locks_mutex).
  39          */
  40         struct list_head head;  /* Chain of private "related" vmas */
  41 };
  42
  43 /*
  44  * The copy-on-write semantics of fork mean that an anon_vma
  45  * can become associated with multiple processes. Furthermore,
  46  * each child process will have its own anon_vma, where new
  47  * pages for that process are instantiated.
  48  *
  49  * This structure allows us to find the anon_vmas associated
  50  * with a VMA, or the VMAs associated with an anon_vma.
  51  * The "same_vma" list contains the anon_vma_chains linking
  52  * all the anon_vmas associated with this VMA.
  53  * The "same_anon_vma" list contains the anon_vma_chains
  54  * which link all the VMAs associated with this anon_vma.
  55  */
  56 struct anon_vma_chain {
  57         struct vm_area_struct *vma;
  58         struct anon_vma *anon_vma;
  59         struct list_head same_vma;   /* locked by mmap_sem & page_table_lock */
  60         struct list_head same_anon_vma; /* locked by anon_vma->lock */
  61 };
  62
  63 #ifdef CONFIG_MMU
  64 #ifdef CONFIG_KSM
  65 static inline void ksm_refcount_init(struct anon_vma *anon_vma)
  66 {
  67         atomic_set(&anon_vma->ksm_refcount, 0);
  68 }
  69
  70 static inline int ksm_refcount(struct anon_vma *anon_vma)
  71 {
  72         return atomic_read(&anon_vma->ksm_refcount);
  73 }
  74 #else
  75 static inline void ksm_refcount_init(struct anon_vma *anon_vma)
  76 {
  77 }
  78
  79 static inline int ksm_refcount(struct anon_vma *anon_vma)
  80 {
  81         return 0;
  82 }
  83 #endif /* CONFIG_KSM */
  84
  85 static inline struct anon_vma *page_anon_vma(struct page *page)
  86 {
  87         if (((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) !=
  88                                             PAGE_MAPPING_ANON)
  89                 return NULL;
  90         return page_rmapping(page);
  91 }
  92
  93 static inline void anon_vma_lock(struct vm_area_struct *vma)
  94 {
  95         struct anon_vma *anon_vma = vma->anon_vma;
  96         if (anon_vma)
  97                 spin_lock(&anon_vma->lock);
  98 }
  99
 100 static inline void anon_vma_unlock(struct vm_area_struct *vma)
 101 {
 102         struct anon_vma *anon_vma = vma->anon_vma;
 103         if (anon_vma)
 104                 spin_unlock(&anon_vma->lock);
 105 }
 106
 107 /*
 108  * anon_vma helper functions.
 109  */
 110 void anon_vma_init(void);       /* create anon_vma_cachep */
 111 int  anon_vma_prepare(struct vm_area_struct *);
 112 void unlink_anon_vmas(struct vm_area_struct *);
 113 int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *);
 114 int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *);
 115 void __anon_vma_link(struct vm_area_struct *);
 116 void anon_vma_free(struct anon_vma *);
 117
 118 static inline void anon_vma_merge(struct vm_area_struct *vma,
 119                                   struct vm_area_struct *next)
 120 {
 121         VM_BUG_ON(vma->anon_vma != next->anon_vma);
 122         unlink_anon_vmas(next);
 123 }
 124
 125 /*
 126  * rmap interfaces called when adding or removing pte of page
 127  */
 128 void page_move_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
 129 void page_add_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
 130 void page_add_new_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
 131 void page_add_file_rmap(struct page *);
 132 void page_remove_rmap(struct page *);
 133
 134 static inline void page_dup_rmap(struct page *page)
 135 {
 136         atomic_inc(&page->_mapcount);
 137 }
 138
 139 /*
 140  * Called from mm/vmscan.c to handle paging out
 141  */
 142 int page_referenced(struct page *, int is_locked,
 143                         struct mem_cgroup *cnt, unsigned long *vm_flags);
 144 int page_referenced_one(struct page *, struct vm_area_struct *,
 145         unsigned long address, unsigned int *mapcount, unsigned long *vm_flags);
 146
 147 enum ttu_flags {
 148         TTU_UNMAP = 0,                  /* unmap mode */
 149         TTU_MIGRATION = 1,              /* migration mode */
 150         TTU_MUNLOCK = 2,                /* munlock mode */
 151         TTU_ACTION_MASK = 0xff,
 152
 153         TTU_IGNORE_MLOCK = (1 << 8),    /* ignore mlock */
 154         TTU_IGNORE_ACCESS = (1 << 9),   /* don't age */
 155         TTU_IGNORE_HWPOISON = (1 << 10),/* corrupted page is recoverable */
 156 };
 157 #define TTU_ACTION(x) ((x) & TTU_ACTION_MASK)
 158
 159 int try_to_unmap(struct page *, enum ttu_flags flags);
 160 int try_to_unmap_one(struct page *, struct vm_area_struct *,
 161                         unsigned long address, enum ttu_flags flags);
 162
 163 /*
 164  * Called from mm/filemap_xip.c to unmap empty zero page
 165  */
 166 pte_t *page_check_address(struct page *, struct mm_struct *,
 167                                 unsigned long, spinlock_t **, int);
 168
 169 /*
 170  * Used by swapoff to help locate where page is expected in vma.
 171  */
 172 unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
 173
 174 /*
 175  * Cleans the PTEs of shared mappings.
 176  * (and since clean PTEs should also be readonly, write protects them too)
 177  *
 178  * returns the number of cleaned PTEs.
 179  */
 180 int page_mkclean(struct page *);
 181
 182 /*
 183  * called in munlock()/munmap() path to check for other vmas holding
 184  * the page mlocked.
 185  */
 186 int try_to_munlock(struct page *);
 187
 188 /*
 189  * Called by memory-failure.c to kill processes.
 190  */
 191 struct anon_vma *page_lock_anon_vma(struct page *page);
 192 void page_unlock_anon_vma(struct anon_vma *anon_vma);
 193 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
 194
 195 /*
 196  * Called by migrate.c to remove migration ptes, but might be used more later.
 197  */
 198 int rmap_walk(struct page *page, int (*rmap_one)(struct page *,
 199                 struct vm_area_struct *, unsigned long, void *), void *arg);
 200
 201 #else   /* !CONFIG_MMU */
 202
 203 #define anon_vma_init()         do {} while (0)
 204 #define anon_vma_prepare(vma)   (0)
 205 #define anon_vma_link(vma)      do {} while (0)
 206
 207 static inline int page_referenced(struct page *page, int is_locked,
 208                                   struct mem_cgroup *cnt,
 209                                   unsigned long *vm_flags)
 210 {
 211         *vm_flags = 0;
 212         return 0;
 213 }
 214
 215 #define try_to_unmap(page, refs) SWAP_FAIL
 216
 217 static inline int page_mkclean(struct page *page)
 218 {
 219         return 0;
 220 }
 221
 222
 223 #endif  /* CONFIG_MMU */
 224
 225 /*
 226  * Return values of try_to_unmap
 227  */
 228 #define SWAP_SUCCESS    0
 229 #define SWAP_AGAIN      1
 230 #define SWAP_FAIL       2
 231 #define SWAP_MLOCK      3
 232
 233 #endif  /* _LINUX_RMAP_H */