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
  59         /* Interval tree of private "related" vmas */
  60         struct rb_root_cached rb_root;
  61 };
  62
  63 /*
  64  * The copy-on-write semantics of fork mean that an anon_vma
  65  * can become associated with multiple processes. Furthermore,
  66  * each child process will have its own anon_vma, where new
  67  * pages for that process are instantiated.
  68  *
  69  * This structure allows us to find the anon_vmas associated
  70  * with a VMA, or the VMAs associated with an anon_vma.
  71  * The "same_vma" list contains the anon_vma_chains linking
  72  * all the anon_vmas associated with this VMA.
  73  * The "rb" field indexes on an interval tree the anon_vma_chains
  74  * which link all the VMAs associated with this anon_vma.
  75  */
  76 struct anon_vma_chain {
  77         struct vm_area_struct *vma;
  78         struct anon_vma *anon_vma;
  79         struct list_head same_vma;   /* locked by mmap_sem & page_table_lock */
  80         struct rb_node rb;                      /* locked by anon_vma->rwsem */
  81         unsigned long rb_subtree_last;
  82 #ifdef CONFIG_DEBUG_VM_RB
  83         unsigned long cached_vma_start, cached_vma_last;
  84 #endif
  85 };
  86
  87 enum ttu_flags {
  88         TTU_MIGRATION           = 0x1,  /* migration mode */
  89         TTU_MUNLOCK             = 0x2,  /* munlock mode */
  90
  91         TTU_SPLIT_HUGE_PMD      = 0x4,  /* split huge PMD if any */
  92         TTU_IGNORE_MLOCK        = 0x8,  /* ignore mlock */
  93         TTU_IGNORE_ACCESS       = 0x10, /* don't age */
  94         TTU_IGNORE_HWPOISON     = 0x20, /* corrupted page is recoverable */
  95         TTU_BATCH_FLUSH         = 0x40, /* Batch TLB flushes where possible
  96                                          * and caller guarantees they will
  97                                          * do a final flush if necessary */
  98         TTU_RMAP_LOCKED         = 0x80, /* do not grab rmap lock:
  99                                          * caller holds it */
 100         TTU_SPLIT_FREEZE        = 0x100,                /* freeze pte under splitting thp */
 101 };
 102
 103 #ifdef CONFIG_MMU
 104 static inline void get_anon_vma(struct anon_vma *anon_vma)
 105 {
 106         atomic_inc(&anon_vma->refcount);
 107 }
 108
 109 void __put_anon_vma(struct anon_vma *anon_vma);
 110
 111 static inline void put_anon_vma(struct anon_vma *anon_vma)
 112 {
 113         if (atomic_dec_and_test(&anon_vma->refcount))
 114                 __put_anon_vma(anon_vma);
 115 }
 116
 117 static inline void anon_vma_lock_write(struct anon_vma *anon_vma)
 118 {
 119         down_write(&anon_vma->root->rwsem);
 120 }
 121
 122 static inline void anon_vma_unlock_write(struct anon_vma *anon_vma)
 123 {
 124         up_write(&anon_vma->root->rwsem);
 125 }
 126
 127 static inline void anon_vma_lock_read(struct anon_vma *anon_vma)
 128 {
 129         down_read(&anon_vma->root->rwsem);
 130 }
 131
 132 static inline void anon_vma_unlock_read(struct anon_vma *anon_vma)
 133 {
 134         up_read(&anon_vma->root->rwsem);
 135 }
 136
 137
 138 /*
 139  * anon_vma helper functions.
 140  */
 141 void anon_vma_init(void);       /* create anon_vma_cachep */
 142 int  __anon_vma_prepare(struct vm_area_struct *);
 143 void unlink_anon_vmas(struct vm_area_struct *);
 144 int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *);
 145 int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *);
 146
 147 static inline int anon_vma_prepare(struct vm_area_struct *vma)
 148 {
 149         if (likely(vma->anon_vma))
 150                 return 0;
 151
 152         return __anon_vma_prepare(vma);
 153 }
 154
 155 static inline void anon_vma_merge(struct vm_area_struct *vma,
 156                                   struct vm_area_struct *next)
 157 {
 158         VM_BUG_ON_VMA(vma->anon_vma != next->anon_vma, vma);
 159         unlink_anon_vmas(next);
 160 }
 161
 162 struct anon_vma *page_get_anon_vma(struct page *page);
 163
 164 /* bitflags for do_page_add_anon_rmap() */
 165 #define RMAP_EXCLUSIVE 0x01
 166 #define RMAP_COMPOUND 0x02
 167
 168 /*
 169  * rmap interfaces called when adding or removing pte of page
 170  */
 171 void page_move_anon_rmap(struct page *, struct vm_area_struct *);
 172 void page_add_anon_rmap(struct page *, struct vm_area_struct *,
 173                 unsigned long, bool);
 174 void do_page_add_anon_rmap(struct page *, struct vm_area_struct *,
 175                            unsigned long, int);
 176 void page_add_new_anon_rmap(struct page *, struct vm_area_struct *,
 177                 unsigned long, bool);
 178 void page_add_file_rmap(struct page *, bool);
 179 void page_remove_rmap(struct page *, bool);
 180
 181 void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *,
 182                             unsigned long);
 183 void hugepage_add_new_anon_rmap(struct page *, struct vm_area_struct *,
 184                                 unsigned long);
 185
 186 static inline void page_dup_rmap(struct page *page, bool compound)
 187 {
 188         atomic_inc(compound ? compound_mapcount_ptr(page) : &page->_mapcount);
 189 }
 190
 191 /*
 192  * Called from mm/vmscan.c to handle paging out
 193  */
 194 int page_referenced(struct page *, int is_locked,
 195                         struct mem_cgroup *memcg, unsigned long *vm_flags);
 196
 197 bool try_to_unmap(struct page *, enum ttu_flags flags);
 198
 199 /* Avoid racy checks */
 200 #define PVMW_SYNC               (1 << 0)
 201 /* Look for migarion entries rather than present PTEs */
 202 #define PVMW_MIGRATION          (1 << 1)
 203
 204 struct page_vma_mapped_walk {
 205         struct page *page;
 206         struct vm_area_struct *vma;
 207         unsigned long address;
 208         pmd_t *pmd;
 209         pte_t *pte;
 210         spinlock_t *ptl;
 211         unsigned int flags;
 212 };
 213
 214 static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
 215 {
 216         if (pvmw->pte)
 217                 pte_unmap(pvmw->pte);
 218         if (pvmw->ptl)
 219                 spin_unlock(pvmw->ptl);
 220 }
 221
 222 bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw);
 223
 224 /*
 225  * Used by swapoff to help locate where page is expected in vma.
 226  */
 227 unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
 228
 229 /*
 230  * Cleans the PTEs of shared mappings.
 231  * (and since clean PTEs should also be readonly, write protects them too)
 232  *
 233  * returns the number of cleaned PTEs.
 234  */
 235 int page_mkclean(struct page *);
 236
 237 /*
 238  * called in munlock()/munmap() path to check for other vmas holding
 239  * the page mlocked.
 240  */
 241 void try_to_munlock(struct page *);
 242
 243 void remove_migration_ptes(struct page *old, struct page *new, bool locked);
 244
 245 /*
 246  * Called by memory-failure.c to kill processes.
 247  */
 248 struct anon_vma *page_lock_anon_vma_read(struct page *page);
 249 void page_unlock_anon_vma_read(struct anon_vma *anon_vma);
 250 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
 251
 252 /*
 253  * rmap_walk_control: To control rmap traversing for specific needs
 254  *
 255  * arg: passed to rmap_one() and invalid_vma()
 256  * rmap_one: executed on each vma where page is mapped
 257  * done: for checking traversing termination condition
 258  * anon_lock: for getting anon_lock by optimized way rather than default
 259  * invalid_vma: for skipping uninterested vma
 260  */
 261 struct rmap_walk_control {
 262         void *arg;
 263         /*
 264          * Return false if page table scanning in rmap_walk should be stopped.
 265          * Otherwise, return true.
 266          */
 267         bool (*rmap_one)(struct page *page, struct vm_area_struct *vma,
 268                                         unsigned long addr, void *arg);
 269         int (*done)(struct page *page);
 270         struct anon_vma *(*anon_lock)(struct page *page);
 271         bool (*invalid_vma)(struct vm_area_struct *vma, void *arg);
 272 };
 273
 274 void rmap_walk(struct page *page, struct rmap_walk_control *rwc);
 275 void rmap_walk_locked(struct page *page, struct rmap_walk_control *rwc);
 276
 277 #else   /* !CONFIG_MMU */
 278
 279 #define anon_vma_init()         do {} while (0)
 280 #define anon_vma_prepare(vma)   (0)
 281 #define anon_vma_link(vma)      do {} while (0)
 282
 283 static inline int page_referenced(struct page *page, int is_locked,
 284                                   struct mem_cgroup *memcg,
 285                                   unsigned long *vm_flags)
 286 {
 287         *vm_flags = 0;
 288         return 0;
 289 }
 290
 291 #define try_to_unmap(page, refs) false
 292
 293 static inline int page_mkclean(struct page *page)
 294 {
 295         return 0;
 296 }
 297
 298
 299 #endif  /* CONFIG_MMU */
 300
 301 #endif  /* _LINUX_RMAP_H */