projects/linux·blob v6.18 · refs

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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#include <linux/pagemap.h>
15#include <linux/memremap.h>
16#include <linux/bit_spinlock.h>
17
18/*
19 * The anon_vma heads a list of private "related" vmas, to scan if
20 * an anonymous page pointing to this anon_vma needs to be unmapped:
21 * the vmas on the list will be related by forking, or by splitting.
22 *
23 * Since vmas come and go as they are split and merged (particularly
24 * in mprotect), the mapping field of an anonymous page cannot point
25 * directly to a vma: instead it points to an anon_vma, on whose list
26 * the related vmas can be easily linked or unlinked.
27 *
28 * After unlinking the last vma on the list, we must garbage collect
29 * the anon_vma object itself: we're guaranteed no page can be
30 * pointing to this anon_vma once its vma list is empty.
31 */
32struct anon_vma {
33 struct anon_vma *root; /* Root of this anon_vma tree */
34 struct rw_semaphore rwsem; /* W: modification, R: walking the list */
35 /*
36 * The refcount is taken on an anon_vma when there is no
37 * guarantee that the vma of page tables will exist for
38 * the duration of the operation. A caller that takes
39 * the reference is responsible for clearing up the
40 * anon_vma if they are the last user on release
41 */
42 atomic_t refcount;
43
44 /*
45 * Count of child anon_vmas. Equals to the count of all anon_vmas that
46 * have ->parent pointing to this one, including itself.
47 *
48 * This counter is used for making decision about reusing anon_vma
49 * instead of forking new one. See comments in function anon_vma_clone.
50 */
51 unsigned long num_children;
52 /* Count of VMAs whose ->anon_vma pointer points to this object. */
53 unsigned long num_active_vmas;
54
55 struct anon_vma *parent; /* Parent of this anon_vma */
56
57 /*
58 * NOTE: the LSB of the rb_root.rb_node is set by
59 * mm_take_all_locks() _after_ taking the above lock. So the
60 * rb_root must only be read/written after taking the above lock
61 * to be sure to see a valid next pointer. The LSB bit itself
62 * is serialized by a system wide lock only visible to
63 * mm_take_all_locks() (mm_all_locks_mutex).
64 */
65
66 /* Interval tree of private "related" vmas */
67 struct rb_root_cached rb_root;
68};
69
70/*
71 * The copy-on-write semantics of fork mean that an anon_vma
72 * can become associated with multiple processes. Furthermore,
73 * each child process will have its own anon_vma, where new
74 * pages for that process are instantiated.
75 *
76 * This structure allows us to find the anon_vmas associated
77 * with a VMA, or the VMAs associated with an anon_vma.
78 * The "same_vma" list contains the anon_vma_chains linking
79 * all the anon_vmas associated with this VMA.
80 * The "rb" field indexes on an interval tree the anon_vma_chains
81 * which link all the VMAs associated with this anon_vma.
82 */
83struct anon_vma_chain {
84 struct vm_area_struct *vma;
85 struct anon_vma *anon_vma;
86 struct list_head same_vma; /* locked by mmap_lock & page_table_lock */
87 struct rb_node rb; /* locked by anon_vma->rwsem */
88 unsigned long rb_subtree_last;
89#ifdef CONFIG_DEBUG_VM_RB
90 unsigned long cached_vma_start, cached_vma_last;
91#endif
92};
93
94enum ttu_flags {
95 TTU_SPLIT_HUGE_PMD = 0x4, /* split huge PMD if any */
96 TTU_IGNORE_MLOCK = 0x8, /* ignore mlock */
97 TTU_SYNC = 0x10, /* avoid racy checks with PVMW_SYNC */
98 TTU_HWPOISON = 0x20, /* do convert pte to hwpoison entry */
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};
105
106#ifdef CONFIG_MMU
107static inline void get_anon_vma(struct anon_vma *anon_vma)
108{
109 atomic_inc(&anon_vma->refcount);
110}
111
112void __put_anon_vma(struct anon_vma *anon_vma);
113
114static inline void put_anon_vma(struct anon_vma *anon_vma)
115{
116 if (atomic_dec_and_test(&anon_vma->refcount))
117 __put_anon_vma(anon_vma);
118}
119
120static inline void anon_vma_lock_write(struct anon_vma *anon_vma)
121{
122 down_write(&anon_vma->root->rwsem);
123}
124
125static inline int anon_vma_trylock_write(struct anon_vma *anon_vma)
126{
127 return down_write_trylock(&anon_vma->root->rwsem);
128}
129
130static inline void anon_vma_unlock_write(struct anon_vma *anon_vma)
131{
132 up_write(&anon_vma->root->rwsem);
133}
134
135static inline void anon_vma_lock_read(struct anon_vma *anon_vma)
136{
137 down_read(&anon_vma->root->rwsem);
138}
139
140static inline int anon_vma_trylock_read(struct anon_vma *anon_vma)
141{
142 return down_read_trylock(&anon_vma->root->rwsem);
143}
144
145static inline void anon_vma_unlock_read(struct anon_vma *anon_vma)
146{
147 up_read(&anon_vma->root->rwsem);
148}
149
150
151/*
152 * anon_vma helper functions.
153 */
154void anon_vma_init(void); /* create anon_vma_cachep */
155int __anon_vma_prepare(struct vm_area_struct *);
156void unlink_anon_vmas(struct vm_area_struct *);
157int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *);
158int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *);
159
160static inline int anon_vma_prepare(struct vm_area_struct *vma)
161{
162 if (likely(vma->anon_vma))
163 return 0;
164
165 return __anon_vma_prepare(vma);
166}
167
168static inline void anon_vma_merge(struct vm_area_struct *vma,
169 struct vm_area_struct *next)
170{
171 VM_BUG_ON_VMA(vma->anon_vma != next->anon_vma, vma);
172 unlink_anon_vmas(next);
173}
174
175struct anon_vma *folio_get_anon_vma(const struct folio *folio);
176
177#ifdef CONFIG_MM_ID
178static __always_inline void folio_lock_large_mapcount(struct folio *folio)
179{
180 bit_spin_lock(FOLIO_MM_IDS_LOCK_BITNUM, &folio->_mm_ids);
181}
182
183static __always_inline void folio_unlock_large_mapcount(struct folio *folio)
184{
185 __bit_spin_unlock(FOLIO_MM_IDS_LOCK_BITNUM, &folio->_mm_ids);
186}
187
188static inline unsigned int folio_mm_id(const struct folio *folio, int idx)
189{
190 VM_WARN_ON_ONCE(idx != 0 && idx != 1);
191 return folio->_mm_id[idx] & MM_ID_MASK;
192}
193
194static inline void folio_set_mm_id(struct folio *folio, int idx, mm_id_t id)
195{
196 VM_WARN_ON_ONCE(idx != 0 && idx != 1);
197 folio->_mm_id[idx] &= ~MM_ID_MASK;
198 folio->_mm_id[idx] |= id;
199}
200
201static inline void __folio_large_mapcount_sanity_checks(const struct folio *folio,
202 int diff, mm_id_t mm_id)
203{
204 VM_WARN_ON_ONCE(!folio_test_large(folio) || folio_test_hugetlb(folio));
205 VM_WARN_ON_ONCE(diff <= 0);
206 VM_WARN_ON_ONCE(mm_id < MM_ID_MIN || mm_id > MM_ID_MAX);
207
208 /*
209 * Make sure we can detect at least one complete PTE mapping of the
210 * folio in a single MM as "exclusively mapped". This is primarily
211 * a check on 32bit, where we currently reduce the size of the per-MM
212 * mapcount to a short.
213 */
214 VM_WARN_ON_ONCE(diff > folio_large_nr_pages(folio));
215 VM_WARN_ON_ONCE(folio_large_nr_pages(folio) - 1 > MM_ID_MAPCOUNT_MAX);
216
217 VM_WARN_ON_ONCE(folio_mm_id(folio, 0) == MM_ID_DUMMY &&
218 folio->_mm_id_mapcount[0] != -1);
219 VM_WARN_ON_ONCE(folio_mm_id(folio, 0) != MM_ID_DUMMY &&
220 folio->_mm_id_mapcount[0] < 0);
221 VM_WARN_ON_ONCE(folio_mm_id(folio, 1) == MM_ID_DUMMY &&
222 folio->_mm_id_mapcount[1] != -1);
223 VM_WARN_ON_ONCE(folio_mm_id(folio, 1) != MM_ID_DUMMY &&
224 folio->_mm_id_mapcount[1] < 0);
225 VM_WARN_ON_ONCE(!folio_mapped(folio) &&
226 test_bit(FOLIO_MM_IDS_SHARED_BITNUM, &folio->_mm_ids));
227}
228
229static __always_inline void folio_set_large_mapcount(struct folio *folio,
230 int mapcount, struct vm_area_struct *vma)
231{
232 __folio_large_mapcount_sanity_checks(folio, mapcount, vma->vm_mm->mm_id);
233
234 VM_WARN_ON_ONCE(folio_mm_id(folio, 0) != MM_ID_DUMMY);
235 VM_WARN_ON_ONCE(folio_mm_id(folio, 1) != MM_ID_DUMMY);
236
237 /* Note: mapcounts start at -1. */
238 atomic_set(&folio->_large_mapcount, mapcount - 1);
239 folio->_mm_id_mapcount[0] = mapcount - 1;
240 folio_set_mm_id(folio, 0, vma->vm_mm->mm_id);
241}
242
243static __always_inline int folio_add_return_large_mapcount(struct folio *folio,
244 int diff, struct vm_area_struct *vma)
245{
246 const mm_id_t mm_id = vma->vm_mm->mm_id;
247 int new_mapcount_val;
248
249 folio_lock_large_mapcount(folio);
250 __folio_large_mapcount_sanity_checks(folio, diff, mm_id);
251
252 new_mapcount_val = atomic_read(&folio->_large_mapcount) + diff;
253 atomic_set(&folio->_large_mapcount, new_mapcount_val);
254
255 /*
256 * If a folio is mapped more than once into an MM on 32bit, we
257 * can in theory overflow the per-MM mapcount (although only for
258 * fairly large folios), turning it negative. In that case, just
259 * free up the slot and mark the folio "mapped shared", otherwise
260 * we might be in trouble when unmapping pages later.
261 */
262 if (folio_mm_id(folio, 0) == mm_id) {
263 folio->_mm_id_mapcount[0] += diff;
264 if (!IS_ENABLED(CONFIG_64BIT) && unlikely(folio->_mm_id_mapcount[0] < 0)) {
265 folio->_mm_id_mapcount[0] = -1;
266 folio_set_mm_id(folio, 0, MM_ID_DUMMY);
267 folio->_mm_ids |= FOLIO_MM_IDS_SHARED_BIT;
268 }
269 } else if (folio_mm_id(folio, 1) == mm_id) {
270 folio->_mm_id_mapcount[1] += diff;
271 if (!IS_ENABLED(CONFIG_64BIT) && unlikely(folio->_mm_id_mapcount[1] < 0)) {
272 folio->_mm_id_mapcount[1] = -1;
273 folio_set_mm_id(folio, 1, MM_ID_DUMMY);
274 folio->_mm_ids |= FOLIO_MM_IDS_SHARED_BIT;
275 }
276 } else if (folio_mm_id(folio, 0) == MM_ID_DUMMY) {
277 folio_set_mm_id(folio, 0, mm_id);
278 folio->_mm_id_mapcount[0] = diff - 1;
279 /* We might have other mappings already. */
280 if (new_mapcount_val != diff - 1)
281 folio->_mm_ids |= FOLIO_MM_IDS_SHARED_BIT;
282 } else if (folio_mm_id(folio, 1) == MM_ID_DUMMY) {
283 folio_set_mm_id(folio, 1, mm_id);
284 folio->_mm_id_mapcount[1] = diff - 1;
285 /* Slot 0 certainly has mappings as well. */
286 folio->_mm_ids |= FOLIO_MM_IDS_SHARED_BIT;
287 }
288 folio_unlock_large_mapcount(folio);
289 return new_mapcount_val + 1;
290}
291#define folio_add_large_mapcount folio_add_return_large_mapcount
292
293static __always_inline int folio_sub_return_large_mapcount(struct folio *folio,
294 int diff, struct vm_area_struct *vma)
295{
296 const mm_id_t mm_id = vma->vm_mm->mm_id;
297 int new_mapcount_val;
298
299 folio_lock_large_mapcount(folio);
300 __folio_large_mapcount_sanity_checks(folio, diff, mm_id);
301
302 new_mapcount_val = atomic_read(&folio->_large_mapcount) - diff;
303 atomic_set(&folio->_large_mapcount, new_mapcount_val);
304
305 /*
306 * There are valid corner cases where we might underflow a per-MM
307 * mapcount (some mappings added when no slot was free, some mappings
308 * added once a slot was free), so we always set it to -1 once we go
309 * negative.
310 */
311 if (folio_mm_id(folio, 0) == mm_id) {
312 folio->_mm_id_mapcount[0] -= diff;
313 if (folio->_mm_id_mapcount[0] >= 0)
314 goto out;
315 folio->_mm_id_mapcount[0] = -1;
316 folio_set_mm_id(folio, 0, MM_ID_DUMMY);
317 } else if (folio_mm_id(folio, 1) == mm_id) {
318 folio->_mm_id_mapcount[1] -= diff;
319 if (folio->_mm_id_mapcount[1] >= 0)
320 goto out;
321 folio->_mm_id_mapcount[1] = -1;
322 folio_set_mm_id(folio, 1, MM_ID_DUMMY);
323 }
324
325 /*
326 * If one MM slot owns all mappings, the folio is mapped exclusively.
327 * Note that if the folio is now unmapped (new_mapcount_val == -1), both
328 * slots must be free (mapcount == -1), and we'll also mark it as
329 * exclusive.
330 */
331 if (folio->_mm_id_mapcount[0] == new_mapcount_val ||
332 folio->_mm_id_mapcount[1] == new_mapcount_val)
333 folio->_mm_ids &= ~FOLIO_MM_IDS_SHARED_BIT;
334out:
335 folio_unlock_large_mapcount(folio);
336 return new_mapcount_val + 1;
337}
338#define folio_sub_large_mapcount folio_sub_return_large_mapcount
339#else /* !CONFIG_MM_ID */
340/*
341 * See __folio_rmap_sanity_checks(), we might map large folios even without
342 * CONFIG_TRANSPARENT_HUGEPAGE. We'll keep that working for now.
343 */
344static inline void folio_set_large_mapcount(struct folio *folio, int mapcount,
345 struct vm_area_struct *vma)
346{
347 /* Note: mapcounts start at -1. */
348 atomic_set(&folio->_large_mapcount, mapcount - 1);
349}
350
351static inline void folio_add_large_mapcount(struct folio *folio,
352 int diff, struct vm_area_struct *vma)
353{
354 atomic_add(diff, &folio->_large_mapcount);
355}
356
357static inline int folio_add_return_large_mapcount(struct folio *folio,
358 int diff, struct vm_area_struct *vma)
359{
360 BUILD_BUG();
361}
362
363static inline void folio_sub_large_mapcount(struct folio *folio,
364 int diff, struct vm_area_struct *vma)
365{
366 atomic_sub(diff, &folio->_large_mapcount);
367}
368
369static inline int folio_sub_return_large_mapcount(struct folio *folio,
370 int diff, struct vm_area_struct *vma)
371{
372 BUILD_BUG();
373}
374#endif /* CONFIG_MM_ID */
375
376#define folio_inc_large_mapcount(folio, vma) \
377 folio_add_large_mapcount(folio, 1, vma)
378#define folio_inc_return_large_mapcount(folio, vma) \
379 folio_add_return_large_mapcount(folio, 1, vma)
380#define folio_dec_large_mapcount(folio, vma) \
381 folio_sub_large_mapcount(folio, 1, vma)
382#define folio_dec_return_large_mapcount(folio, vma) \
383 folio_sub_return_large_mapcount(folio, 1, vma)
384
385/* RMAP flags, currently only relevant for some anon rmap operations. */
386typedef int __bitwise rmap_t;
387
388/*
389 * No special request: A mapped anonymous (sub)page is possibly shared between
390 * processes.
391 */
392#define RMAP_NONE ((__force rmap_t)0)
393
394/* The anonymous (sub)page is exclusive to a single process. */
395#define RMAP_EXCLUSIVE ((__force rmap_t)BIT(0))
396
397static __always_inline void __folio_rmap_sanity_checks(const struct folio *folio,
398 const struct page *page, int nr_pages, enum pgtable_level level)
399{
400 /* hugetlb folios are handled separately. */
401 VM_WARN_ON_FOLIO(folio_test_hugetlb(folio), folio);
402
403 /* When (un)mapping zeropages, we should never touch ref+mapcount. */
404 VM_WARN_ON_FOLIO(is_zero_folio(folio), folio);
405
406 /*
407 * TODO: we get driver-allocated folios that have nothing to do with
408 * the rmap using vm_insert_page(); therefore, we cannot assume that
409 * folio_test_large_rmappable() holds for large folios. We should
410 * handle any desired mapcount+stats accounting for these folios in
411 * VM_MIXEDMAP VMAs separately, and then sanity-check here that
412 * we really only get rmappable folios.
413 */
414
415 VM_WARN_ON_ONCE(nr_pages <= 0);
416 VM_WARN_ON_FOLIO(page_folio(page) != folio, folio);
417 VM_WARN_ON_FOLIO(page_folio(page + nr_pages - 1) != folio, folio);
418
419 switch (level) {
420 case PGTABLE_LEVEL_PTE:
421 break;
422 case PGTABLE_LEVEL_PMD:
423 /*
424 * We don't support folios larger than a single PMD yet. So
425 * when PGTABLE_LEVEL_PMD is set, we assume that we are creating
426 * a single "entire" mapping of the folio.
427 */
428 VM_WARN_ON_FOLIO(folio_nr_pages(folio) != HPAGE_PMD_NR, folio);
429 VM_WARN_ON_FOLIO(nr_pages != HPAGE_PMD_NR, folio);
430 break;
431 case PGTABLE_LEVEL_PUD:
432 /*
433 * Assume that we are creating a single "entire" mapping of the
434 * folio.
435 */
436 VM_WARN_ON_FOLIO(folio_nr_pages(folio) != HPAGE_PUD_NR, folio);
437 VM_WARN_ON_FOLIO(nr_pages != HPAGE_PUD_NR, folio);
438 break;
439 default:
440 BUILD_BUG();
441 }
442
443 /*
444 * Anon folios must have an associated live anon_vma as long as they're
445 * mapped into userspace.
446 * Note that the atomic_read() mainly does two things:
447 *
448 * 1. In KASAN builds with CONFIG_SLUB_RCU_DEBUG, it causes KASAN to
449 * check that the associated anon_vma has not yet been freed (subject
450 * to KASAN's usual limitations). This check will pass if the
451 * anon_vma's refcount has already dropped to 0 but an RCU grace
452 * period hasn't passed since then.
453 * 2. If the anon_vma has not yet been freed, it checks that the
454 * anon_vma still has a nonzero refcount (as opposed to being in the
455 * middle of an RCU delay for getting freed).
456 */
457 if (folio_test_anon(folio) && !folio_test_ksm(folio)) {
458 unsigned long mapping = (unsigned long)folio->mapping;
459 struct anon_vma *anon_vma;
460
461 anon_vma = (void *)(mapping - FOLIO_MAPPING_ANON);
462 VM_WARN_ON_FOLIO(atomic_read(&anon_vma->refcount) == 0, folio);
463 }
464}
465
466/*
467 * rmap interfaces called when adding or removing pte of page
468 */
469void folio_move_anon_rmap(struct folio *, struct vm_area_struct *);
470void folio_add_anon_rmap_ptes(struct folio *, struct page *, int nr_pages,
471 struct vm_area_struct *, unsigned long address, rmap_t flags);
472#define folio_add_anon_rmap_pte(folio, page, vma, address, flags) \
473 folio_add_anon_rmap_ptes(folio, page, 1, vma, address, flags)
474void folio_add_anon_rmap_pmd(struct folio *, struct page *,
475 struct vm_area_struct *, unsigned long address, rmap_t flags);
476void folio_add_new_anon_rmap(struct folio *, struct vm_area_struct *,
477 unsigned long address, rmap_t flags);
478void folio_add_file_rmap_ptes(struct folio *, struct page *, int nr_pages,
479 struct vm_area_struct *);
480#define folio_add_file_rmap_pte(folio, page, vma) \
481 folio_add_file_rmap_ptes(folio, page, 1, vma)
482void folio_add_file_rmap_pmd(struct folio *, struct page *,
483 struct vm_area_struct *);
484void folio_add_file_rmap_pud(struct folio *, struct page *,
485 struct vm_area_struct *);
486void folio_remove_rmap_ptes(struct folio *, struct page *, int nr_pages,
487 struct vm_area_struct *);
488#define folio_remove_rmap_pte(folio, page, vma) \
489 folio_remove_rmap_ptes(folio, page, 1, vma)
490void folio_remove_rmap_pmd(struct folio *, struct page *,
491 struct vm_area_struct *);
492void folio_remove_rmap_pud(struct folio *, struct page *,
493 struct vm_area_struct *);
494
495void hugetlb_add_anon_rmap(struct folio *, struct vm_area_struct *,
496 unsigned long address, rmap_t flags);
497void hugetlb_add_new_anon_rmap(struct folio *, struct vm_area_struct *,
498 unsigned long address);
499
500/* See folio_try_dup_anon_rmap_*() */
501static inline int hugetlb_try_dup_anon_rmap(struct folio *folio,
502 struct vm_area_struct *vma)
503{
504 VM_WARN_ON_FOLIO(!folio_test_hugetlb(folio), folio);
505 VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio);
506
507 if (PageAnonExclusive(&folio->page)) {
508 if (unlikely(folio_needs_cow_for_dma(vma, folio)))
509 return -EBUSY;
510 ClearPageAnonExclusive(&folio->page);
511 }
512 atomic_inc(&folio->_entire_mapcount);
513 atomic_inc(&folio->_large_mapcount);
514 return 0;
515}
516
517/* See folio_try_share_anon_rmap_*() */
518static inline int hugetlb_try_share_anon_rmap(struct folio *folio)
519{
520 VM_WARN_ON_FOLIO(!folio_test_hugetlb(folio), folio);
521 VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio);
522 VM_WARN_ON_FOLIO(!PageAnonExclusive(&folio->page), folio);
523
524 /* Paired with the memory barrier in try_grab_folio(). */
525 if (IS_ENABLED(CONFIG_HAVE_GUP_FAST))
526 smp_mb();
527
528 if (unlikely(folio_maybe_dma_pinned(folio)))
529 return -EBUSY;
530 ClearPageAnonExclusive(&folio->page);
531
532 /*
533 * This is conceptually a smp_wmb() paired with the smp_rmb() in
534 * gup_must_unshare().
535 */
536 if (IS_ENABLED(CONFIG_HAVE_GUP_FAST))
537 smp_mb__after_atomic();
538 return 0;
539}
540
541static inline void hugetlb_add_file_rmap(struct folio *folio)
542{
543 VM_WARN_ON_FOLIO(!folio_test_hugetlb(folio), folio);
544 VM_WARN_ON_FOLIO(folio_test_anon(folio), folio);
545
546 atomic_inc(&folio->_entire_mapcount);
547 atomic_inc(&folio->_large_mapcount);
548}
549
550static inline void hugetlb_remove_rmap(struct folio *folio)
551{
552 VM_WARN_ON_FOLIO(!folio_test_hugetlb(folio), folio);
553
554 atomic_dec(&folio->_entire_mapcount);
555 atomic_dec(&folio->_large_mapcount);
556}
557
558static __always_inline void __folio_dup_file_rmap(struct folio *folio,
559 struct page *page, int nr_pages, struct vm_area_struct *dst_vma,
560 enum pgtable_level level)
561{
562 const int orig_nr_pages = nr_pages;
563
564 __folio_rmap_sanity_checks(folio, page, nr_pages, level);
565
566 switch (level) {
567 case PGTABLE_LEVEL_PTE:
568 if (!folio_test_large(folio)) {
569 atomic_inc(&folio->_mapcount);
570 break;
571 }
572
573 if (IS_ENABLED(CONFIG_PAGE_MAPCOUNT)) {
574 do {
575 atomic_inc(&page->_mapcount);
576 } while (page++, --nr_pages > 0);
577 }
578 folio_add_large_mapcount(folio, orig_nr_pages, dst_vma);
579 break;
580 case PGTABLE_LEVEL_PMD:
581 case PGTABLE_LEVEL_PUD:
582 atomic_inc(&folio->_entire_mapcount);
583 folio_inc_large_mapcount(folio, dst_vma);
584 break;
585 default:
586 BUILD_BUG();
587 }
588}
589
590/**
591 * folio_dup_file_rmap_ptes - duplicate PTE mappings of a page range of a folio
592 * @folio: The folio to duplicate the mappings of
593 * @page: The first page to duplicate the mappings of
594 * @nr_pages: The number of pages of which the mapping will be duplicated
595 * @dst_vma: The destination vm area
596 *
597 * The page range of the folio is defined by [page, page + nr_pages)
598 *
599 * The caller needs to hold the page table lock.
600 */
601static inline void folio_dup_file_rmap_ptes(struct folio *folio,
602 struct page *page, int nr_pages, struct vm_area_struct *dst_vma)
603{
604 __folio_dup_file_rmap(folio, page, nr_pages, dst_vma, PGTABLE_LEVEL_PTE);
605}
606
607static __always_inline void folio_dup_file_rmap_pte(struct folio *folio,
608 struct page *page, struct vm_area_struct *dst_vma)
609{
610 __folio_dup_file_rmap(folio, page, 1, dst_vma, PGTABLE_LEVEL_PTE);
611}
612
613/**
614 * folio_dup_file_rmap_pmd - duplicate a PMD mapping of a page range of a folio
615 * @folio: The folio to duplicate the mapping of
616 * @page: The first page to duplicate the mapping of
617 * @dst_vma: The destination vm area
618 *
619 * The page range of the folio is defined by [page, page + HPAGE_PMD_NR)
620 *
621 * The caller needs to hold the page table lock.
622 */
623static inline void folio_dup_file_rmap_pmd(struct folio *folio,
624 struct page *page, struct vm_area_struct *dst_vma)
625{
626#ifdef CONFIG_TRANSPARENT_HUGEPAGE
627 __folio_dup_file_rmap(folio, page, HPAGE_PMD_NR, dst_vma, PGTABLE_LEVEL_PTE);
628#else
629 WARN_ON_ONCE(true);
630#endif
631}
632
633static __always_inline int __folio_try_dup_anon_rmap(struct folio *folio,
634 struct page *page, int nr_pages, struct vm_area_struct *dst_vma,
635 struct vm_area_struct *src_vma, enum pgtable_level level)
636{
637 const int orig_nr_pages = nr_pages;
638 bool maybe_pinned;
639 int i;
640
641 VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio);
642 __folio_rmap_sanity_checks(folio, page, nr_pages, level);
643
644 /*
645 * If this folio may have been pinned by the parent process,
646 * don't allow to duplicate the mappings but instead require to e.g.,
647 * copy the subpage immediately for the child so that we'll always
648 * guarantee the pinned folio won't be randomly replaced in the
649 * future on write faults.
650 */
651 maybe_pinned = likely(!folio_is_device_private(folio)) &&
652 unlikely(folio_needs_cow_for_dma(src_vma, folio));
653
654 /*
655 * No need to check+clear for already shared PTEs/PMDs of the
656 * folio. But if any page is PageAnonExclusive, we must fallback to
657 * copying if the folio maybe pinned.
658 */
659 switch (level) {
660 case PGTABLE_LEVEL_PTE:
661 if (unlikely(maybe_pinned)) {
662 for (i = 0; i < nr_pages; i++)
663 if (PageAnonExclusive(page + i))
664 return -EBUSY;
665 }
666
667 if (!folio_test_large(folio)) {
668 if (PageAnonExclusive(page))
669 ClearPageAnonExclusive(page);
670 atomic_inc(&folio->_mapcount);
671 break;
672 }
673
674 do {
675 if (PageAnonExclusive(page))
676 ClearPageAnonExclusive(page);
677 if (IS_ENABLED(CONFIG_PAGE_MAPCOUNT))
678 atomic_inc(&page->_mapcount);
679 } while (page++, --nr_pages > 0);
680 folio_add_large_mapcount(folio, orig_nr_pages, dst_vma);
681 break;
682 case PGTABLE_LEVEL_PMD:
683 case PGTABLE_LEVEL_PUD:
684 if (PageAnonExclusive(page)) {
685 if (unlikely(maybe_pinned))
686 return -EBUSY;
687 ClearPageAnonExclusive(page);
688 }
689 atomic_inc(&folio->_entire_mapcount);
690 folio_inc_large_mapcount(folio, dst_vma);
691 break;
692 default:
693 BUILD_BUG();
694 }
695 return 0;
696}
697
698/**
699 * folio_try_dup_anon_rmap_ptes - try duplicating PTE mappings of a page range
700 * of a folio
701 * @folio: The folio to duplicate the mappings of
702 * @page: The first page to duplicate the mappings of
703 * @nr_pages: The number of pages of which the mapping will be duplicated
704 * @dst_vma: The destination vm area
705 * @src_vma: The vm area from which the mappings are duplicated
706 *
707 * The page range of the folio is defined by [page, page + nr_pages)
708 *
709 * The caller needs to hold the page table lock and the
710 * vma->vma_mm->write_protect_seq.
711 *
712 * Duplicating the mappings can only fail if the folio may be pinned; device
713 * private folios cannot get pinned and consequently this function cannot fail
714 * for them.
715 *
716 * If duplicating the mappings succeeded, the duplicated PTEs have to be R/O in
717 * the parent and the child. They must *not* be writable after this call
718 * succeeded.
719 *
720 * Returns 0 if duplicating the mappings succeeded. Returns -EBUSY otherwise.
721 */
722static inline int folio_try_dup_anon_rmap_ptes(struct folio *folio,
723 struct page *page, int nr_pages, struct vm_area_struct *dst_vma,
724 struct vm_area_struct *src_vma)
725{
726 return __folio_try_dup_anon_rmap(folio, page, nr_pages, dst_vma,
727 src_vma, PGTABLE_LEVEL_PTE);
728}
729
730static __always_inline int folio_try_dup_anon_rmap_pte(struct folio *folio,
731 struct page *page, struct vm_area_struct *dst_vma,
732 struct vm_area_struct *src_vma)
733{
734 return __folio_try_dup_anon_rmap(folio, page, 1, dst_vma, src_vma,
735 PGTABLE_LEVEL_PTE);
736}
737
738/**
739 * folio_try_dup_anon_rmap_pmd - try duplicating a PMD mapping of a page range
740 * of a folio
741 * @folio: The folio to duplicate the mapping of
742 * @page: The first page to duplicate the mapping of
743 * @dst_vma: The destination vm area
744 * @src_vma: The vm area from which the mapping is duplicated
745 *
746 * The page range of the folio is defined by [page, page + HPAGE_PMD_NR)
747 *
748 * The caller needs to hold the page table lock and the
749 * vma->vma_mm->write_protect_seq.
750 *
751 * Duplicating the mapping can only fail if the folio may be pinned; device
752 * private folios cannot get pinned and consequently this function cannot fail
753 * for them.
754 *
755 * If duplicating the mapping succeeds, the duplicated PMD has to be R/O in
756 * the parent and the child. They must *not* be writable after this call
757 * succeeded.
758 *
759 * Returns 0 if duplicating the mapping succeeded. Returns -EBUSY otherwise.
760 */
761static inline int folio_try_dup_anon_rmap_pmd(struct folio *folio,
762 struct page *page, struct vm_area_struct *dst_vma,
763 struct vm_area_struct *src_vma)
764{
765#ifdef CONFIG_TRANSPARENT_HUGEPAGE
766 return __folio_try_dup_anon_rmap(folio, page, HPAGE_PMD_NR, dst_vma,
767 src_vma, PGTABLE_LEVEL_PMD);
768#else
769 WARN_ON_ONCE(true);
770 return -EBUSY;
771#endif
772}
773
774static __always_inline int __folio_try_share_anon_rmap(struct folio *folio,
775 struct page *page, int nr_pages, enum pgtable_level level)
776{
777 VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio);
778 VM_WARN_ON_FOLIO(!PageAnonExclusive(page), folio);
779 __folio_rmap_sanity_checks(folio, page, nr_pages, level);
780
781 /* device private folios cannot get pinned via GUP. */
782 if (unlikely(folio_is_device_private(folio))) {
783 ClearPageAnonExclusive(page);
784 return 0;
785 }
786
787 /*
788 * We have to make sure that when we clear PageAnonExclusive, that
789 * the page is not pinned and that concurrent GUP-fast won't succeed in
790 * concurrently pinning the page.
791 *
792 * Conceptually, PageAnonExclusive clearing consists of:
793 * (A1) Clear PTE
794 * (A2) Check if the page is pinned; back off if so.
795 * (A3) Clear PageAnonExclusive
796 * (A4) Restore PTE (optional, but certainly not writable)
797 *
798 * When clearing PageAnonExclusive, we cannot possibly map the page
799 * writable again, because anon pages that may be shared must never
800 * be writable. So in any case, if the PTE was writable it cannot
801 * be writable anymore afterwards and there would be a PTE change. Only
802 * if the PTE wasn't writable, there might not be a PTE change.
803 *
804 * Conceptually, GUP-fast pinning of an anon page consists of:
805 * (B1) Read the PTE
806 * (B2) FOLL_WRITE: check if the PTE is not writable; back off if so.
807 * (B3) Pin the mapped page
808 * (B4) Check if the PTE changed by re-reading it; back off if so.
809 * (B5) If the original PTE is not writable, check if
810 * PageAnonExclusive is not set; back off if so.
811 *
812 * If the PTE was writable, we only have to make sure that GUP-fast
813 * observes a PTE change and properly backs off.
814 *
815 * If the PTE was not writable, we have to make sure that GUP-fast either
816 * detects a (temporary) PTE change or that PageAnonExclusive is cleared
817 * and properly backs off.
818 *
819 * Consequently, when clearing PageAnonExclusive(), we have to make
820 * sure that (A1), (A2)/(A3) and (A4) happen in the right memory
821 * order. In GUP-fast pinning code, we have to make sure that (B3),(B4)
822 * and (B5) happen in the right memory order.
823 *
824 * We assume that there might not be a memory barrier after
825 * clearing/invalidating the PTE (A1) and before restoring the PTE (A4),
826 * so we use explicit ones here.
827 */
828
829 /* Paired with the memory barrier in try_grab_folio(). */
830 if (IS_ENABLED(CONFIG_HAVE_GUP_FAST))
831 smp_mb();
832
833 if (unlikely(folio_maybe_dma_pinned(folio)))
834 return -EBUSY;
835 ClearPageAnonExclusive(page);
836
837 /*
838 * This is conceptually a smp_wmb() paired with the smp_rmb() in
839 * gup_must_unshare().
840 */
841 if (IS_ENABLED(CONFIG_HAVE_GUP_FAST))
842 smp_mb__after_atomic();
843 return 0;
844}
845
846/**
847 * folio_try_share_anon_rmap_pte - try marking an exclusive anonymous page
848 * mapped by a PTE possibly shared to prepare
849 * for KSM or temporary unmapping
850 * @folio: The folio to share a mapping of
851 * @page: The mapped exclusive page
852 *
853 * The caller needs to hold the page table lock and has to have the page table
854 * entries cleared/invalidated.
855 *
856 * This is similar to folio_try_dup_anon_rmap_pte(), however, not used during
857 * fork() to duplicate mappings, but instead to prepare for KSM or temporarily
858 * unmapping parts of a folio (swap, migration) via folio_remove_rmap_pte().
859 *
860 * Marking the mapped page shared can only fail if the folio maybe pinned;
861 * device private folios cannot get pinned and consequently this function cannot
862 * fail.
863 *
864 * Returns 0 if marking the mapped page possibly shared succeeded. Returns
865 * -EBUSY otherwise.
866 */
867static inline int folio_try_share_anon_rmap_pte(struct folio *folio,
868 struct page *page)
869{
870 return __folio_try_share_anon_rmap(folio, page, 1, PGTABLE_LEVEL_PTE);
871}
872
873/**
874 * folio_try_share_anon_rmap_pmd - try marking an exclusive anonymous page
875 * range mapped by a PMD possibly shared to
876 * prepare for temporary unmapping
877 * @folio: The folio to share the mapping of
878 * @page: The first page to share the mapping of
879 *
880 * The page range of the folio is defined by [page, page + HPAGE_PMD_NR)
881 *
882 * The caller needs to hold the page table lock and has to have the page table
883 * entries cleared/invalidated.
884 *
885 * This is similar to folio_try_dup_anon_rmap_pmd(), however, not used during
886 * fork() to duplicate a mapping, but instead to prepare for temporarily
887 * unmapping parts of a folio (swap, migration) via folio_remove_rmap_pmd().
888 *
889 * Marking the mapped pages shared can only fail if the folio maybe pinned;
890 * device private folios cannot get pinned and consequently this function cannot
891 * fail.
892 *
893 * Returns 0 if marking the mapped pages possibly shared succeeded. Returns
894 * -EBUSY otherwise.
895 */
896static inline int folio_try_share_anon_rmap_pmd(struct folio *folio,
897 struct page *page)
898{
899#ifdef CONFIG_TRANSPARENT_HUGEPAGE
900 return __folio_try_share_anon_rmap(folio, page, HPAGE_PMD_NR,
901 PGTABLE_LEVEL_PMD);
902#else
903 WARN_ON_ONCE(true);
904 return -EBUSY;
905#endif
906}
907
908/*
909 * Called from mm/vmscan.c to handle paging out
910 */
911int folio_referenced(struct folio *, int is_locked,
912 struct mem_cgroup *memcg, vm_flags_t *vm_flags);
913
914void try_to_migrate(struct folio *folio, enum ttu_flags flags);
915void try_to_unmap(struct folio *, enum ttu_flags flags);
916
917struct page *make_device_exclusive(struct mm_struct *mm, unsigned long addr,
918 void *owner, struct folio **foliop);
919
920/* Avoid racy checks */
921#define PVMW_SYNC (1 << 0)
922/* Look for migration entries rather than present PTEs */
923#define PVMW_MIGRATION (1 << 1)
924
925/* Result flags */
926
927/* The page is mapped across page table boundary */
928#define PVMW_PGTABLE_CROSSED (1 << 16)
929
930struct page_vma_mapped_walk {
931 unsigned long pfn;
932 unsigned long nr_pages;
933 pgoff_t pgoff;
934 struct vm_area_struct *vma;
935 unsigned long address;
936 pmd_t *pmd;
937 pte_t *pte;
938 spinlock_t *ptl;
939 unsigned int flags;
940};
941
942#define DEFINE_FOLIO_VMA_WALK(name, _folio, _vma, _address, _flags) \
943 struct page_vma_mapped_walk name = { \
944 .pfn = folio_pfn(_folio), \
945 .nr_pages = folio_nr_pages(_folio), \
946 .pgoff = folio_pgoff(_folio), \
947 .vma = _vma, \
948 .address = _address, \
949 .flags = _flags, \
950 }
951
952static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
953{
954 /* HugeTLB pte is set to the relevant page table entry without pte_mapped. */
955 if (pvmw->pte && !is_vm_hugetlb_page(pvmw->vma))
956 pte_unmap(pvmw->pte);
957 if (pvmw->ptl)
958 spin_unlock(pvmw->ptl);
959}
960
961/**
962 * page_vma_mapped_walk_restart - Restart the page table walk.
963 * @pvmw: Pointer to struct page_vma_mapped_walk.
964 *
965 * It restarts the page table walk when changes occur in the page
966 * table, such as splitting a PMD. Ensures that the PTL held during
967 * the previous walk is released and resets the state to allow for
968 * a new walk starting at the current address stored in pvmw->address.
969 */
970static inline void
971page_vma_mapped_walk_restart(struct page_vma_mapped_walk *pvmw)
972{
973 WARN_ON_ONCE(!pvmw->pmd && !pvmw->pte);
974
975 if (likely(pvmw->ptl))
976 spin_unlock(pvmw->ptl);
977 else
978 WARN_ON_ONCE(1);
979
980 pvmw->ptl = NULL;
981 pvmw->pmd = NULL;
982 pvmw->pte = NULL;
983}
984
985bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw);
986unsigned long page_address_in_vma(const struct folio *folio,
987 const struct page *, const struct vm_area_struct *);
988
989/*
990 * Cleans the PTEs of shared mappings.
991 * (and since clean PTEs should also be readonly, write protects them too)
992 *
993 * returns the number of cleaned PTEs.
994 */
995int folio_mkclean(struct folio *);
996
997int mapping_wrprotect_range(struct address_space *mapping, pgoff_t pgoff,
998 unsigned long pfn, unsigned long nr_pages);
999
1000int pfn_mkclean_range(unsigned long pfn, unsigned long nr_pages, pgoff_t pgoff,
1001 struct vm_area_struct *vma);
1002
1003enum rmp_flags {
1004 RMP_LOCKED = 1 << 0,
1005 RMP_USE_SHARED_ZEROPAGE = 1 << 1,
1006};
1007
1008void remove_migration_ptes(struct folio *src, struct folio *dst, int flags);
1009
1010/*
1011 * rmap_walk_control: To control rmap traversing for specific needs
1012 *
1013 * arg: passed to rmap_one() and invalid_vma()
1014 * try_lock: bail out if the rmap lock is contended
1015 * contended: indicate the rmap traversal bailed out due to lock contention
1016 * rmap_one: executed on each vma where page is mapped
1017 * done: for checking traversing termination condition
1018 * anon_lock: for getting anon_lock by optimized way rather than default
1019 * invalid_vma: for skipping uninterested vma
1020 */
1021struct rmap_walk_control {
1022 void *arg;
1023 bool try_lock;
1024 bool contended;
1025 /*
1026 * Return false if page table scanning in rmap_walk should be stopped.
1027 * Otherwise, return true.
1028 */
1029 bool (*rmap_one)(struct folio *folio, struct vm_area_struct *vma,
1030 unsigned long addr, void *arg);
1031 int (*done)(struct folio *folio);
1032 struct anon_vma *(*anon_lock)(const struct folio *folio,
1033 struct rmap_walk_control *rwc);
1034 bool (*invalid_vma)(struct vm_area_struct *vma, void *arg);
1035};
1036
1037void rmap_walk(struct folio *folio, struct rmap_walk_control *rwc);
1038void rmap_walk_locked(struct folio *folio, struct rmap_walk_control *rwc);
1039struct anon_vma *folio_lock_anon_vma_read(const struct folio *folio,
1040 struct rmap_walk_control *rwc);
1041
1042#else /* !CONFIG_MMU */
1043
1044#define anon_vma_init() do {} while (0)
1045#define anon_vma_prepare(vma) (0)
1046
1047static inline int folio_referenced(struct folio *folio, int is_locked,
1048 struct mem_cgroup *memcg,
1049 vm_flags_t *vm_flags)
1050{
1051 *vm_flags = 0;
1052 return 0;
1053}
1054
1055static inline void try_to_unmap(struct folio *folio, enum ttu_flags flags)
1056{
1057}
1058
1059static inline int folio_mkclean(struct folio *folio)
1060{
1061 return 0;
1062}
1063#endif /* CONFIG_MMU */
1064
1065#endif /* _LINUX_RMAP_H */