include/linux/rmap.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _LINUX_RMAP_H
   3 #define _LINUX_RMAP_H
   4 /*
   5  * Declarations for Reverse Mapping functions in mm/rmap.c
   6  */
   7
   8 #include <linux/list.h>
   9 #include <linux/slab.h>
  10 #include <linux/mm.h>
  11 #include <linux/rwsem.h>
  12 #include <linux/memcontrol.h>
  13 #include <linux/highmem.h>
  14
  15 /*
  16  * The anon_vma heads a list of private "related" vmas, to scan if
  17  * an anonymous page pointing to this anon_vma needs to be unmapped:
  18  * the vmas on the list will be related by forking, or by splitting.
  19  *
  20  * Since vmas come and go as they are split and merged (particularly
  21  * in mprotect), the mapping field of an anonymous page cannot point
  22  * directly to a vma: instead it points to an anon_vma, on whose list
  23  * the related vmas can be easily linked or unlinked.
  24  *
  25  * After unlinking the last vma on the list, we must garbage collect
  26  * the anon_vma object itself: we're guaranteed no page can be
  27  * pointing to this anon_vma once its vma list is empty.
  28  */
  29 struct anon_vma {
  30         struct anon_vma *root;          /* Root of this anon_vma tree */
  31         struct rw_semaphore rwsem;      /* W: modification, R: walking the list */
  32         /*
  33          * The refcount is taken on an anon_vma when there is no
  34          * guarantee that the vma of page tables will exist for
  35          * the duration of the operation. A caller that takes
  36          * the reference is responsible for clearing up the
  37          * anon_vma if they are the last user on release
  38          */
  39         atomic_t refcount;
  40
  41         /*
  42          * Count of child anon_vmas and VMAs which points to this anon_vma.
  43          *
  44          * This counter is used for making decision about reusing anon_vma
  45          * instead of forking new one. See comments in function anon_vma_clone.
  46          */
  47         unsigned degree;
  48
  49         struct anon_vma *parent;        /* Parent of this anon_vma */
  50
  51         /*
  52          * NOTE: the LSB of the rb_root.rb_node is set by
  53          * mm_take_all_locks() _after_ taking the above lock. So the
  54          * rb_root must only be read/written after taking the above lock
  55          * to be sure to see a valid next pointer. The LSB bit itself
  56          * is serialized by a system wide lock only visible to
  57          * mm_take_all_locks() (mm_all_locks_mutex).
  58          */
  59
  60         /* Interval tree of private "related" vmas */
  61         struct rb_root_cached rb_root;
  62 };
  63
  64 /*
  65  * The copy-on-write semantics of fork mean that an anon_vma
  66  * can become associated with multiple processes. Furthermore,
  67  * each child process will have its own anon_vma, where new
  68  * pages for that process are instantiated.
  69  *
  70  * This structure allows us to find the anon_vmas associated
  71  * with a VMA, or the VMAs associated with an anon_vma.
  72  * The "same_vma" list contains the anon_vma_chains linking
  73  * all the anon_vmas associated with this VMA.
  74  * The "rb" field indexes on an interval tree the anon_vma_chains
  75  * which link all the VMAs associated with this anon_vma.
  76  */
  77 struct anon_vma_chain {
  78         struct vm_area_struct *vma;
  79         struct anon_vma *anon_vma;
  80         struct list_head same_vma;   /* locked by mmap_sem & page_table_lock */
  81         struct rb_node rb;                      /* locked by anon_vma->rwsem */
  82         unsigned long rb_subtree_last;
  83 #ifdef CONFIG_DEBUG_VM_RB
  84         unsigned long cached_vma_start, cached_vma_last;
  85 #endif
  86 };
  87
  88 enum ttu_flags {
  89         TTU_MIGRATION           = 0x1,  /* migration mode */
  90         TTU_MUNLOCK             = 0x2,  /* munlock mode */
  91
  92         TTU_SPLIT_HUGE_PMD      = 0x4,  /* split huge PMD if any */
  93         TTU_IGNORE_MLOCK        = 0x8,  /* ignore mlock */
  94         TTU_IGNORE_ACCESS       = 0x10, /* don't age */
  95         TTU_IGNORE_HWPOISON     = 0x20, /* corrupted page is recoverable */
  96         TTU_BATCH_FLUSH         = 0x40, /* Batch TLB flushes where possible
  97                                          * and caller guarantees they will
  98                                          * do a final flush if necessary */
  99         TTU_RMAP_LOCKED         = 0x80, /* do not grab rmap lock:
 100                                          * caller holds it */
 101         TTU_SPLIT_FREEZE        = 0x100,                /* freeze pte under splitting thp */
 102 };
 103
 104 #ifdef CONFIG_MMU
 105 static inline void get_anon_vma(struct anon_vma *anon_vma)
 106 {
 107         atomic_inc(&anon_vma->refcount);
 108 }
 109
 110 void __put_anon_vma(struct anon_vma *anon_vma);
 111
 112 static inline void put_anon_vma(struct anon_vma *anon_vma)
 113 {
 114         if (atomic_dec_and_test(&anon_vma->refcount))
 115                 __put_anon_vma(anon_vma);
 116 }
 117
 118 static inline void anon_vma_lock_write(struct anon_vma *anon_vma)
 119 {
 120         down_write(&anon_vma->root->rwsem);
 121 }
 122
 123 static inline void anon_vma_unlock_write(struct anon_vma *anon_vma)
 124 {
 125         up_write(&anon_vma->root->rwsem);
 126 }
 127
 128 static inline void anon_vma_lock_read(struct anon_vma *anon_vma)
 129 {
 130         down_read(&anon_vma->root->rwsem);
 131 }
 132
 133 static inline void anon_vma_unlock_read(struct anon_vma *anon_vma)
 134 {
 135         up_read(&anon_vma->root->rwsem);
 136 }
 137
 138
 139 /*
 140  * anon_vma helper functions.
 141  */
 142 void anon_vma_init(void);       /* create anon_vma_cachep */
 143 int  __anon_vma_prepare(struct vm_area_struct *);
 144 void unlink_anon_vmas(struct vm_area_struct *);
 145 int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *);
 146 int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *);
 147
 148 static inline int anon_vma_prepare(struct vm_area_struct *vma)
 149 {
 150         if (likely(vma->anon_vma))
 151                 return 0;
 152
 153         return __anon_vma_prepare(vma);
 154 }
 155
 156 static inline void anon_vma_merge(struct vm_area_struct *vma,
 157                                   struct vm_area_struct *next)
 158 {
 159         VM_BUG_ON_VMA(vma->anon_vma != next->anon_vma, vma);
 160         unlink_anon_vmas(next);
 161 }
 162
 163 struct anon_vma *page_get_anon_vma(struct page *page);
 164
 165 /* bitflags for do_page_add_anon_rmap() */
 166 #define RMAP_EXCLUSIVE 0x01
 167 #define RMAP_COMPOUND 0x02
 168
 169 /*
 170  * rmap interfaces called when adding or removing pte of page
 171  */
 172 void page_move_anon_rmap(struct page *, struct vm_area_struct *);
 173 void page_add_anon_rmap(struct page *, struct vm_area_struct *,
 174                 unsigned long, bool);
 175 void do_page_add_anon_rmap(struct page *, struct vm_area_struct *,
 176                            unsigned long, int);
 177 void page_add_new_anon_rmap(struct page *, struct vm_area_struct *,
 178                 unsigned long, bool);
 179 void page_add_file_rmap(struct page *, bool);
 180 void page_remove_rmap(struct page *, bool);
 181
 182 void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *,
 183                             unsigned long);
 184 void hugepage_add_new_anon_rmap(struct page *, struct vm_area_struct *,
 185                                 unsigned long);
 186
 187 static inline void page_dup_rmap(struct page *page, bool compound)
 188 {
 189         atomic_inc(compound ? compound_mapcount_ptr(page) : &page->_mapcount);
 190 }
 191
 192 /*
 193  * Called from mm/vmscan.c to handle paging out
 194  */
 195 int page_referenced(struct page *, int is_locked,
 196                         struct mem_cgroup *memcg, unsigned long *vm_flags);
 197
 198 bool try_to_unmap(struct page *, enum ttu_flags flags);
 199
 200 /* Avoid racy checks */
 201 #define PVMW_SYNC               (1 << 0)
 202 /* Look for migarion entries rather than present PTEs */
 203 #define PVMW_MIGRATION          (1 << 1)
 204
 205 struct page_vma_mapped_walk {
 206         struct page *page;
 207         struct vm_area_struct *vma;
 208         unsigned long address;
 209         pmd_t *pmd;
 210         pte_t *pte;
 211         spinlock_t *ptl;
 212         unsigned int flags;
 213 };
 214
 215 static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
 216 {
 217         if (pvmw->pte)
 218                 pte_unmap(pvmw->pte);
 219         if (pvmw->ptl)
 220                 spin_unlock(pvmw->ptl);
 221 }
 222
 223 bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw);
 224
 225 /*
 226  * Used by swapoff to help locate where page is expected in vma.
 227  */
 228 unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
 229
 230 /*
 231  * Cleans the PTEs of shared mappings.
 232  * (and since clean PTEs should also be readonly, write protects them too)
 233  *
 234  * returns the number of cleaned PTEs.
 235  */
 236 int page_mkclean(struct page *);
 237
 238 /*
 239  * called in munlock()/munmap() path to check for other vmas holding
 240  * the page mlocked.
 241  */
 242 void try_to_munlock(struct page *);
 243
 244 void remove_migration_ptes(struct page *old, struct page *new, bool locked);
 245
 246 /*
 247  * Called by memory-failure.c to kill processes.
 248  */
 249 struct anon_vma *page_lock_anon_vma_read(struct page *page);
 250 void page_unlock_anon_vma_read(struct anon_vma *anon_vma);
 251 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
 252
 253 /*
 254  * rmap_walk_control: To control rmap traversing for specific needs
 255  *
 256  * arg: passed to rmap_one() and invalid_vma()
 257  * rmap_one: executed on each vma where page is mapped
 258  * done: for checking traversing termination condition
 259  * anon_lock: for getting anon_lock by optimized way rather than default
 260  * invalid_vma: for skipping uninterested vma
 261  */
 262 struct rmap_walk_control {
 263         void *arg;
 264         /*
 265          * Return false if page table scanning in rmap_walk should be stopped.
 266          * Otherwise, return true.
 267          */
 268         bool (*rmap_one)(struct page *page, struct vm_area_struct *vma,
 269                                         unsigned long addr, void *arg);
 270         int (*done)(struct page *page);
 271         struct anon_vma *(*anon_lock)(struct page *page);
 272         bool (*invalid_vma)(struct vm_area_struct *vma, void *arg);
 273 };
 274
 275 void rmap_walk(struct page *page, struct rmap_walk_control *rwc);
 276 void rmap_walk_locked(struct page *page, struct rmap_walk_control *rwc);
 277
 278 #else   /* !CONFIG_MMU */
 279
 280 #define anon_vma_init()         do {} while (0)
 281 #define anon_vma_prepare(vma)   (0)
 282 #define anon_vma_link(vma)      do {} while (0)
 283
 284 static inline int page_referenced(struct page *page, int is_locked,
 285                                   struct mem_cgroup *memcg,
 286                                   unsigned long *vm_flags)
 287 {
 288         *vm_flags = 0;
 289         return 0;
 290 }
 291
 292 #define try_to_unmap(page, refs) false
 293
 294 static inline int page_mkclean(struct page *page)
 295 {
 296         return 0;
 297 }
 298
 299
 300 #endif  /* CONFIG_MMU */
 301
 302 #endif  /* _LINUX_RMAP_H */