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. Equals to the count of all anon_vmas that
43 * have ->parent pointing to this one, including itself.
44 *
45 * This counter is used for making decision about reusing anon_vma
46 * instead of forking new one. See comments in function anon_vma_clone.
47 */
48 unsigned long num_children;
49 /* Count of VMAs whose ->anon_vma pointer points to this object. */
50 unsigned long num_active_vmas;
51
52 struct anon_vma *parent; /* Parent of this anon_vma */
53
54 /*
55 * NOTE: the LSB of the rb_root.rb_node is set by
56 * mm_take_all_locks() _after_ taking the above lock. So the
57 * rb_root must only be read/written after taking the above lock
58 * to be sure to see a valid next pointer. The LSB bit itself
59 * is serialized by a system wide lock only visible to
60 * mm_take_all_locks() (mm_all_locks_mutex).
61 */
62
63 /* Interval tree of private "related" vmas */
64 struct rb_root_cached rb_root;
65 };
66
67 /*
68 * The copy-on-write semantics of fork mean that an anon_vma
69 * can become associated with multiple processes. Furthermore,
70 * each child process will have its own anon_vma, where new
71 * pages for that process are instantiated.
72 *
73 * This structure allows us to find the anon_vmas associated
74 * with a VMA, or the VMAs associated with an anon_vma.
75 * The "same_vma" list contains the anon_vma_chains linking
76 * all the anon_vmas associated with this VMA.
77 * The "rb" field indexes on an interval tree the anon_vma_chains
78 * which link all the VMAs associated with this anon_vma.
79 */
80 struct anon_vma_chain {
81 struct vm_area_struct *vma;
82 struct anon_vma *anon_vma;
83 struct list_head same_vma; /* locked by mmap_sem & page_table_lock */
84 struct rb_node rb; /* locked by anon_vma->rwsem */
85 unsigned long rb_subtree_last;
86 #ifdef CONFIG_DEBUG_VM_RB
87 unsigned long cached_vma_start, cached_vma_last;
88 #endif
89 };
90
91 enum ttu_flags {
92 TTU_MIGRATION = 0x1, /* migration mode */
93 TTU_MUNLOCK = 0x2, /* munlock mode */
94
95 TTU_SPLIT_HUGE_PMD = 0x4, /* split huge PMD if any */
96 TTU_IGNORE_MLOCK = 0x8, /* ignore mlock */
97 TTU_IGNORE_ACCESS = 0x10, /* don't age */
98 TTU_IGNORE_HWPOISON = 0x20, /* corrupted page is recoverable */
99 TTU_BATCH_FLUSH = 0x40, /* Batch TLB flushes where possible
100 * and caller guarantees they will
101 * do a final flush if necessary */
102 TTU_RMAP_LOCKED = 0x80, /* do not grab rmap lock:
103 * caller holds it */
104 TTU_SPLIT_FREEZE = 0x100, /* freeze pte under splitting thp */
105 TTU_SYNC = 0x200, /* avoid racy checks with PVMW_SYNC */
106 };
107
108 #ifdef CONFIG_MMU
get_anon_vma(struct anon_vma * anon_vma)109 static inline void get_anon_vma(struct anon_vma *anon_vma)
110 {
111 atomic_inc(&anon_vma->refcount);
112 }
113
114 void __put_anon_vma(struct anon_vma *anon_vma);
115
put_anon_vma(struct anon_vma * anon_vma)116 static inline void put_anon_vma(struct anon_vma *anon_vma)
117 {
118 if (atomic_dec_and_test(&anon_vma->refcount))
119 __put_anon_vma(anon_vma);
120 }
121
anon_vma_lock_write(struct anon_vma * anon_vma)122 static inline void anon_vma_lock_write(struct anon_vma *anon_vma)
123 {
124 down_write(&anon_vma->root->rwsem);
125 }
126
anon_vma_unlock_write(struct anon_vma * anon_vma)127 static inline void anon_vma_unlock_write(struct anon_vma *anon_vma)
128 {
129 up_write(&anon_vma->root->rwsem);
130 }
131
anon_vma_lock_read(struct anon_vma * anon_vma)132 static inline void anon_vma_lock_read(struct anon_vma *anon_vma)
133 {
134 down_read(&anon_vma->root->rwsem);
135 }
136
anon_vma_unlock_read(struct anon_vma * anon_vma)137 static inline void anon_vma_unlock_read(struct anon_vma *anon_vma)
138 {
139 up_read(&anon_vma->root->rwsem);
140 }
141
142
143 /*
144 * anon_vma helper functions.
145 */
146 void anon_vma_init(void); /* create anon_vma_cachep */
147 int __anon_vma_prepare(struct vm_area_struct *);
148 void unlink_anon_vmas(struct vm_area_struct *);
149 int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *);
150 int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *);
151
anon_vma_prepare(struct vm_area_struct * vma)152 static inline int anon_vma_prepare(struct vm_area_struct *vma)
153 {
154 if (likely(vma->anon_vma))
155 return 0;
156
157 return __anon_vma_prepare(vma);
158 }
159
anon_vma_merge(struct vm_area_struct * vma,struct vm_area_struct * next)160 static inline void anon_vma_merge(struct vm_area_struct *vma,
161 struct vm_area_struct *next)
162 {
163 VM_BUG_ON_VMA(vma->anon_vma != next->anon_vma, vma);
164 unlink_anon_vmas(next);
165 }
166
167 struct anon_vma *page_get_anon_vma(struct page *page);
168
169 /* bitflags for do_page_add_anon_rmap() */
170 #define RMAP_EXCLUSIVE 0x01
171 #define RMAP_COMPOUND 0x02
172
173 /*
174 * rmap interfaces called when adding or removing pte of page
175 */
176 void page_move_anon_rmap(struct page *, struct vm_area_struct *);
177 void page_add_anon_rmap(struct page *, struct vm_area_struct *,
178 unsigned long, bool);
179 void do_page_add_anon_rmap(struct page *, struct vm_area_struct *,
180 unsigned long, int);
181 void page_add_new_anon_rmap(struct page *, struct vm_area_struct *,
182 unsigned long, bool);
183 void page_add_file_rmap(struct page *, bool);
184 void page_remove_rmap(struct page *, bool);
185
186 void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *,
187 unsigned long);
188 void hugepage_add_new_anon_rmap(struct page *, struct vm_area_struct *,
189 unsigned long);
190
page_dup_rmap(struct page * page,bool compound)191 static inline void page_dup_rmap(struct page *page, bool compound)
192 {
193 atomic_inc(compound ? compound_mapcount_ptr(page) : &page->_mapcount);
194 }
195
196 /*
197 * Called from mm/vmscan.c to handle paging out
198 */
199 int page_referenced(struct page *, int is_locked,
200 struct mem_cgroup *memcg, unsigned long *vm_flags);
201
202 bool try_to_unmap(struct page *, enum ttu_flags flags);
203
204 /* Avoid racy checks */
205 #define PVMW_SYNC (1 << 0)
206 /* Look for migarion entries rather than present PTEs */
207 #define PVMW_MIGRATION (1 << 1)
208
209 struct page_vma_mapped_walk {
210 struct page *page;
211 struct vm_area_struct *vma;
212 unsigned long address;
213 pmd_t *pmd;
214 pte_t *pte;
215 spinlock_t *ptl;
216 unsigned int flags;
217 };
218
page_vma_mapped_walk_done(struct page_vma_mapped_walk * pvmw)219 static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
220 {
221 /* HugeTLB pte is set to the relevant page table entry without pte_mapped. */
222 if (pvmw->pte && !PageHuge(pvmw->page))
223 pte_unmap(pvmw->pte);
224 if (pvmw->ptl)
225 spin_unlock(pvmw->ptl);
226 }
227
228 bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw);
229
230 /*
231 * Used by swapoff to help locate where page is expected in vma.
232 */
233 unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
234
235 /*
236 * Cleans the PTEs of shared mappings.
237 * (and since clean PTEs should also be readonly, write protects them too)
238 *
239 * returns the number of cleaned PTEs.
240 */
241 int page_mkclean(struct page *);
242
243 /*
244 * called in munlock()/munmap() path to check for other vmas holding
245 * the page mlocked.
246 */
247 void try_to_munlock(struct page *);
248
249 void remove_migration_ptes(struct page *old, struct page *new, bool locked);
250
251 /*
252 * Called by memory-failure.c to kill processes.
253 */
254 struct anon_vma *page_lock_anon_vma_read(struct page *page);
255 void page_unlock_anon_vma_read(struct anon_vma *anon_vma);
256 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
257
258 /*
259 * rmap_walk_control: To control rmap traversing for specific needs
260 *
261 * arg: passed to rmap_one() and invalid_vma()
262 * rmap_one: executed on each vma where page is mapped
263 * done: for checking traversing termination condition
264 * anon_lock: for getting anon_lock by optimized way rather than default
265 * invalid_vma: for skipping uninterested vma
266 */
267 struct rmap_walk_control {
268 void *arg;
269 /*
270 * Return false if page table scanning in rmap_walk should be stopped.
271 * Otherwise, return true.
272 */
273 bool (*rmap_one)(struct page *page, struct vm_area_struct *vma,
274 unsigned long addr, void *arg);
275 int (*done)(struct page *page);
276 struct anon_vma *(*anon_lock)(struct page *page);
277 bool (*invalid_vma)(struct vm_area_struct *vma, void *arg);
278 };
279
280 void rmap_walk(struct page *page, struct rmap_walk_control *rwc);
281 void rmap_walk_locked(struct page *page, struct rmap_walk_control *rwc);
282
283 #else /* !CONFIG_MMU */
284
285 #define anon_vma_init() do {} while (0)
286 #define anon_vma_prepare(vma) (0)
287 #define anon_vma_link(vma) do {} while (0)
288
page_referenced(struct page * page,int is_locked,struct mem_cgroup * memcg,unsigned long * vm_flags)289 static inline int page_referenced(struct page *page, int is_locked,
290 struct mem_cgroup *memcg,
291 unsigned long *vm_flags)
292 {
293 *vm_flags = 0;
294 return 0;
295 }
296
297 #define try_to_unmap(page, refs) false
298
page_mkclean(struct page * page)299 static inline int page_mkclean(struct page *page)
300 {
301 return 0;
302 }
303
304
305 #endif /* CONFIG_MMU */
306
307 #endif /* _LINUX_RMAP_H */
308