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 */ 303