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/rwsem.h>
  11 #include <linux/memcontrol.h>
  12 #include <linux/highmem.h>
  13
  14 /*
  15  * The anon_vma heads a list of private "related" vmas, to scan if
  16  * an anonymous page pointing to this anon_vma needs to be unmapped:
  17  * the vmas on the list will be related by forking, or by splitting.
  18  *
  19  * Since vmas come and go as they are split and merged (particularly
  20  * in mprotect), the mapping field of an anonymous page cannot point
  21  * directly to a vma: instead it points to an anon_vma, on whose list
  22  * the related vmas can be easily linked or unlinked.
  23  *
  24  * After unlinking the last vma on the list, we must garbage collect
  25  * the anon_vma object itself: we're guaranteed no page can be
  26  * pointing to this anon_vma once its vma list is empty.
  27  */
  28 struct anon_vma {
  29         struct anon_vma *root;          /* Root of this anon_vma tree */
  30         struct rw_semaphore rwsem;      /* W: modification, R: walking the list */
  31         /*
  32          * The refcount is taken on an anon_vma when there is no
  33          * guarantee that the vma of page tables will exist for
  34          * the duration of the operation. A caller that takes
  35          * the reference is responsible for clearing up the
  36          * anon_vma if they are the last user on release
  37          */
  38         atomic_t refcount;
  39
  40         /*
  41          * Count of child anon_vmas and VMAs which points to this anon_vma.
  42          *
  43          * This counter is used for making decision about reusing anon_vma
  44          * instead of forking new one. See comments in function anon_vma_clone.
  45          */
  46         unsigned degree;
  47
  48         struct anon_vma *parent;        /* Parent of this anon_vma */
  49
  50         /*
  51          * NOTE: the LSB of the rb_root.rb_node is set by
  52          * mm_take_all_locks() _after_ taking the above lock. So the
  53          * rb_root must only be read/written after taking the above lock
  54          * to be sure to see a valid next pointer. The LSB bit itself
  55          * is serialized by a system wide lock only visible to
  56          * mm_take_all_locks() (mm_all_locks_mutex).
  57          */
  58         struct rb_root rb_root; /* Interval tree of private "related" vmas */
  59 };
  60
  61 /*
  62  * The copy-on-write semantics of fork mean that an anon_vma
  63  * can become associated with multiple processes. Furthermore,
  64  * each child process will have its own anon_vma, where new
  65  * pages for that process are instantiated.
  66  *
  67  * This structure allows us to find the anon_vmas associated
  68  * with a VMA, or the VMAs associated with an anon_vma.
  69  * The "same_vma" list contains the anon_vma_chains linking
  70  * all the anon_vmas associated with this VMA.
  71  * The "rb" field indexes on an interval tree the anon_vma_chains
  72  * which link all the VMAs associated with this anon_vma.
  73  */
  74 struct anon_vma_chain {
  75         struct vm_area_struct *vma;
  76         struct anon_vma *anon_vma;
  77         struct list_head same_vma;   /* locked by mmap_sem & page_table_lock */
  78         struct rb_node rb;                      /* locked by anon_vma->rwsem */
  79         unsigned long rb_subtree_last;
  80 #ifdef CONFIG_DEBUG_VM_RB
  81         unsigned long cached_vma_start, cached_vma_last;
  82 #endif
  83 };
  84
  85 enum ttu_flags {
  86         TTU_MIGRATION           = 0x1,  /* migration mode */
  87         TTU_MUNLOCK             = 0x2,  /* munlock mode */
  88
  89         TTU_SPLIT_HUGE_PMD      = 0x4,  /* split huge PMD if any */
  90         TTU_IGNORE_MLOCK        = 0x8,  /* ignore mlock */
  91         TTU_IGNORE_ACCESS       = 0x10, /* don't age */
  92         TTU_IGNORE_HWPOISON     = 0x20, /* corrupted page is recoverable */
  93         TTU_BATCH_FLUSH         = 0x40, /* Batch TLB flushes where possible
  94                                          * and caller guarantees they will
  95                                          * do a final flush if necessary */
  96         TTU_RMAP_LOCKED         = 0x80  /* do not grab rmap lock:
  97                                          * caller holds it */
  98 };
  99
 100 #ifdef CONFIG_MMU
 101 static inline void get_anon_vma(struct anon_vma *anon_vma)
 102 {
 103         atomic_inc(&anon_vma->refcount);
 104 }
 105
 106 void __put_anon_vma(struct anon_vma *anon_vma);
 107
 108 static inline void put_anon_vma(struct anon_vma *anon_vma)
 109 {
 110         if (atomic_dec_and_test(&anon_vma->refcount))
 111                 __put_anon_vma(anon_vma);
 112 }
 113
 114 static inline void anon_vma_lock_write(struct anon_vma *anon_vma)
 115 {
 116         down_write(&anon_vma->root->rwsem);
 117 }
 118
 119 static inline void anon_vma_unlock_write(struct anon_vma *anon_vma)
 120 {
 121         up_write(&anon_vma->root->rwsem);
 122 }
 123
 124 static inline void anon_vma_lock_read(struct anon_vma *anon_vma)
 125 {
 126         down_read(&anon_vma->root->rwsem);
 127 }
 128
 129 static inline void anon_vma_unlock_read(struct anon_vma *anon_vma)
 130 {
 131         up_read(&anon_vma->root->rwsem);
 132 }
 133
 134
 135 /*
 136  * anon_vma helper functions.
 137  */
 138 void anon_vma_init(void);       /* create anon_vma_cachep */
 139 int  __anon_vma_prepare(struct vm_area_struct *);
 140 void unlink_anon_vmas(struct vm_area_struct *);
 141 int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *);
 142 int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *);
 143
 144 static inline int anon_vma_prepare(struct vm_area_struct *vma)
 145 {
 146         if (likely(vma->anon_vma))
 147                 return 0;
 148
 149         return __anon_vma_prepare(vma);
 150 }
 151
 152 static inline void anon_vma_merge(struct vm_area_struct *vma,
 153                                   struct vm_area_struct *next)
 154 {
 155         VM_BUG_ON_VMA(vma->anon_vma != next->anon_vma, vma);
 156         unlink_anon_vmas(next);
 157 }
 158
 159 struct anon_vma *page_get_anon_vma(struct page *page);
 160
 161 /* bitflags for do_page_add_anon_rmap() */
 162 #define RMAP_EXCLUSIVE 0x01
 163 #define RMAP_COMPOUND 0x02
 164
 165 /*
 166  * rmap interfaces called when adding or removing pte of page
 167  */
 168 void page_move_anon_rmap(struct page *, struct vm_area_struct *);
 169 void page_add_anon_rmap(struct page *, struct vm_area_struct *,
 170                 unsigned long, bool);
 171 void do_page_add_anon_rmap(struct page *, struct vm_area_struct *,
 172                            unsigned long, int);
 173 void page_add_new_anon_rmap(struct page *, struct vm_area_struct *,
 174                 unsigned long, bool);
 175 void page_add_file_rmap(struct page *, bool);
 176 void page_remove_rmap(struct page *, bool);
 177
 178 void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *,
 179                             unsigned long);
 180 void hugepage_add_new_anon_rmap(struct page *, struct vm_area_struct *,
 181                                 unsigned long);
 182
 183 static inline void page_dup_rmap(struct page *page, bool compound)
 184 {
 185         atomic_inc(compound ? compound_mapcount_ptr(page) : &page->_mapcount);
 186 }
 187
 188 /*
 189  * Called from mm/vmscan.c to handle paging out
 190  */
 191 int page_referenced(struct page *, int is_locked,
 192                         struct mem_cgroup *memcg, unsigned long *vm_flags);
 193
 194 bool try_to_unmap(struct page *, enum ttu_flags flags);
 195
 196 /* Avoid racy checks */
 197 #define PVMW_SYNC               (1 << 0)
 198 /* Look for migarion entries rather than present PTEs */
 199 #define PVMW_MIGRATION          (1 << 1)
 200
 201 struct page_vma_mapped_walk {
 202         struct page *page;
 203         struct vm_area_struct *vma;
 204         unsigned long address;
 205         pmd_t *pmd;
 206         pte_t *pte;
 207         spinlock_t *ptl;
 208         unsigned int flags;
 209 };
 210
 211 static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
 212 {
 213         if (pvmw->pte)
 214                 pte_unmap(pvmw->pte);
 215         if (pvmw->ptl)
 216                 spin_unlock(pvmw->ptl);
 217 }
 218
 219 bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw);
 220
 221 /*
 222  * Used by swapoff to help locate where page is expected in vma.
 223  */
 224 unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
 225
 226 /*
 227  * Cleans the PTEs of shared mappings.
 228  * (and since clean PTEs should also be readonly, write protects them too)
 229  *
 230  * returns the number of cleaned PTEs.
 231  */
 232 int page_mkclean(struct page *);
 233
 234 /*
 235  * called in munlock()/munmap() path to check for other vmas holding
 236  * the page mlocked.
 237  */
 238 void try_to_munlock(struct page *);
 239
 240 void remove_migration_ptes(struct page *old, struct page *new, bool locked);
 241
 242 /*
 243  * Called by memory-failure.c to kill processes.
 244  */
 245 struct anon_vma *page_lock_anon_vma_read(struct page *page);
 246 void page_unlock_anon_vma_read(struct anon_vma *anon_vma);
 247 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
 248
 249 /*
 250  * rmap_walk_control: To control rmap traversing for specific needs
 251  *
 252  * arg: passed to rmap_one() and invalid_vma()
 253  * rmap_one: executed on each vma where page is mapped
 254  * done: for checking traversing termination condition
 255  * anon_lock: for getting anon_lock by optimized way rather than default
 256  * invalid_vma: for skipping uninterested vma
 257  */
 258 struct rmap_walk_control {
 259         void *arg;
 260         /*
 261          * Return false if page table scanning in rmap_walk should be stopped.
 262          * Otherwise, return true.
 263          */
 264         bool (*rmap_one)(struct page *page, struct vm_area_struct *vma,
 265                                         unsigned long addr, void *arg);
 266         int (*done)(struct page *page);
 267         struct anon_vma *(*anon_lock)(struct page *page);
 268         bool (*invalid_vma)(struct vm_area_struct *vma, void *arg);
 269 };
 270
 271 void rmap_walk(struct page *page, struct rmap_walk_control *rwc);
 272 void rmap_walk_locked(struct page *page, struct rmap_walk_control *rwc);
 273
 274 #else   /* !CONFIG_MMU */
 275
 276 #define anon_vma_init()         do {} while (0)
 277 #define anon_vma_prepare(vma)   (0)
 278 #define anon_vma_link(vma)      do {} while (0)
 279
 280 static inline int page_referenced(struct page *page, int is_locked,
 281                                   struct mem_cgroup *memcg,
 282                                   unsigned long *vm_flags)
 283 {
 284         *vm_flags = 0;
 285         return 0;
 286 }
 287
 288 #define try_to_unmap(page, refs) false
 289
 290 static inline int page_mkclean(struct page *page)
 291 {
 292         return 0;
 293 }
 294
 295
 296 #endif  /* CONFIG_MMU */
 297
 298 #endif  /* _LINUX_RMAP_H */