linux/include/linux/rmap.h
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   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/mutex.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 */
  27struct anon_vma {
  28        struct anon_vma *root;  /* Root of this anon_vma tree */
  29        struct mutex mutex;     /* 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 */
  63struct 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->mutex */
  68};
  69
  70#ifdef CONFIG_MMU
  71static inline void get_anon_vma(struct anon_vma *anon_vma)
  72{
  73        atomic_inc(&anon_vma->refcount);
  74}
  75
  76void __put_anon_vma(struct anon_vma *anon_vma);
  77
  78static 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
  84static 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
  92static 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                mutex_lock(&anon_vma->root->mutex);
  97}
  98
  99static 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                mutex_unlock(&anon_vma->root->mutex);
 104}
 105
 106static inline void anon_vma_lock(struct anon_vma *anon_vma)
 107{
 108        mutex_lock(&anon_vma->root->mutex);
 109}
 110
 111static inline void anon_vma_unlock(struct anon_vma *anon_vma)
 112{
 113        mutex_unlock(&anon_vma->root->mutex);
 114}
 115
 116/*
 117 * anon_vma helper functions.
 118 */
 119void anon_vma_init(void);       /* create anon_vma_cachep */
 120int  anon_vma_prepare(struct vm_area_struct *);
 121void unlink_anon_vmas(struct vm_area_struct *);
 122int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *);
 123void anon_vma_moveto_tail(struct vm_area_struct *);
 124int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *);
 125
 126static 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
 133struct anon_vma *page_get_anon_vma(struct page *page);
 134
 135/*
 136 * rmap interfaces called when adding or removing pte of page
 137 */
 138void page_move_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
 139void page_add_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
 140void do_page_add_anon_rmap(struct page *, struct vm_area_struct *,
 141                           unsigned long, int);
 142void page_add_new_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
 143void page_add_file_rmap(struct page *);
 144void page_remove_rmap(struct page *);
 145
 146void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *,
 147                            unsigned long);
 148void hugepage_add_new_anon_rmap(struct page *, struct vm_area_struct *,
 149                                unsigned long);
 150
 151static 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 */
 159int page_referenced(struct page *, int is_locked,
 160                        struct mem_cgroup *memcg, unsigned long *vm_flags);
 161int page_referenced_one(struct page *, struct vm_area_struct *,
 162        unsigned long address, unsigned int *mapcount, unsigned long *vm_flags);
 163
 164enum 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
 176int try_to_unmap(struct page *, enum ttu_flags flags);
 177int try_to_unmap_one(struct page *, struct vm_area_struct *,
 178                        unsigned long address, enum ttu_flags flags);
 179
 180/*
 181 * Called from mm/filemap_xip.c to unmap empty zero page
 182 */
 183pte_t *__page_check_address(struct page *, struct mm_struct *,
 184                                unsigned long, spinlock_t **, int);
 185
 186static inline pte_t *page_check_address(struct page *page, struct mm_struct *mm,
 187                                        unsigned long address,
 188                                        spinlock_t **ptlp, int sync)
 189{
 190        pte_t *ptep;
 191
 192        __cond_lock(*ptlp, ptep = __page_check_address(page, mm, address,
 193                                                       ptlp, sync));
 194        return ptep;
 195}
 196
 197/*
 198 * Used by swapoff to help locate where page is expected in vma.
 199 */
 200unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
 201
 202/*
 203 * Cleans the PTEs of shared mappings.
 204 * (and since clean PTEs should also be readonly, write protects them too)
 205 *
 206 * returns the number of cleaned PTEs.
 207 */
 208int page_mkclean(struct page *);
 209
 210/*
 211 * called in munlock()/munmap() path to check for other vmas holding
 212 * the page mlocked.
 213 */
 214int try_to_munlock(struct page *);
 215
 216/*
 217 * Called by memory-failure.c to kill processes.
 218 */
 219struct anon_vma *page_lock_anon_vma(struct page *page);
 220void page_unlock_anon_vma(struct anon_vma *anon_vma);
 221int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
 222
 223/*
 224 * Called by migrate.c to remove migration ptes, but might be used more later.
 225 */
 226int rmap_walk(struct page *page, int (*rmap_one)(struct page *,
 227                struct vm_area_struct *, unsigned long, void *), void *arg);
 228
 229#else   /* !CONFIG_MMU */
 230
 231#define anon_vma_init()         do {} while (0)
 232#define anon_vma_prepare(vma)   (0)
 233#define anon_vma_link(vma)      do {} while (0)
 234
 235static inline int page_referenced(struct page *page, int is_locked,
 236                                  struct mem_cgroup *memcg,
 237                                  unsigned long *vm_flags)
 238{
 239        *vm_flags = 0;
 240        return 0;
 241}
 242
 243#define try_to_unmap(page, refs) SWAP_FAIL
 244
 245static inline int page_mkclean(struct page *page)
 246{
 247        return 0;
 248}
 249
 250
 251#endif  /* CONFIG_MMU */
 252
 253/*
 254 * Return values of try_to_unmap
 255 */
 256#define SWAP_SUCCESS    0
 257#define SWAP_AGAIN      1
 258#define SWAP_FAIL       2
 259#define SWAP_MLOCK      3
 260
 261#endif  /* _LINUX_RMAP_H */
 262
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