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1/*
2 * mm/rmap.c - physical to virtual reverse mappings
3 *
4 * Copyright 2001, Rik van Riel <riel@conectiva.com.br>
5 * Released under the General Public License (GPL).
6 *
7 * Simple, low overhead reverse mapping scheme.
8 * Please try to keep this thing as modular as possible.
9 *
10 * Provides methods for unmapping each kind of mapped page:
11 * the anon methods track anonymous pages, and
12 * the file methods track pages belonging to an inode.
13 *
14 * Original design by Rik van Riel <riel@conectiva.com.br> 2001
15 * File methods by Dave McCracken <dmccr@us.ibm.com> 2003, 2004
16 * Anonymous methods by Andrea Arcangeli <andrea@suse.de> 2004
17 * Contributions by Hugh Dickins 2003, 2004
18 */
19
20/*
21 * Lock ordering in mm:
22 *
23 * inode->i_rwsem (while writing or truncating, not reading or faulting)
24 * mm->mmap_lock
25 * mapping->invalidate_lock (in filemap_fault)
26 * folio_lock
27 * hugetlbfs_i_mmap_rwsem_key (in huge_pmd_share, see hugetlbfs below)
28 * vma_start_write
29 * mapping->i_mmap_rwsem
30 * anon_vma->rwsem
31 * mm->page_table_lock or pte_lock
32 * swap_lock (in swap_duplicate, swap_info_get)
33 * mmlist_lock (in mmput, drain_mmlist and others)
34 * mapping->private_lock (in block_dirty_folio)
35 * i_pages lock (widely used)
36 * lruvec->lru_lock (in folio_lruvec_lock_irq)
37 * inode->i_lock (in set_page_dirty's __mark_inode_dirty)
38 * bdi.wb->list_lock (in set_page_dirty's __mark_inode_dirty)
39 * sb_lock (within inode_lock in fs/fs-writeback.c)
40 * i_pages lock (widely used, in set_page_dirty,
41 * in arch-dependent flush_dcache_mmap_lock,
42 * within bdi.wb->list_lock in __sync_single_inode)
43 *
44 * anon_vma->rwsem,mapping->i_mmap_rwsem (memory_failure, collect_procs_anon)
45 * ->tasklist_lock
46 * pte map lock
47 *
48 * hugetlbfs PageHuge() take locks in this order:
49 * hugetlb_fault_mutex (hugetlbfs specific page fault mutex)
50 * vma_lock (hugetlb specific lock for pmd_sharing)
51 * mapping->i_mmap_rwsem (also used for hugetlb pmd sharing)
52 * folio_lock
53 */
54
55#include <linux/mm.h>
56#include <linux/sched/mm.h>
57#include <linux/sched/task.h>
58#include <linux/pagemap.h>
59#include <linux/swap.h>
60#include <linux/swapops.h>
61#include <linux/slab.h>
62#include <linux/init.h>
63#include <linux/ksm.h>
64#include <linux/rmap.h>
65#include <linux/rcupdate.h>
66#include <linux/export.h>
67#include <linux/memcontrol.h>
68#include <linux/mmu_notifier.h>
69#include <linux/migrate.h>
70#include <linux/hugetlb.h>
71#include <linux/huge_mm.h>
72#include <linux/backing-dev.h>
73#include <linux/page_idle.h>
74#include <linux/memremap.h>
75#include <linux/userfaultfd_k.h>
76#include <linux/mm_inline.h>
77#include <linux/oom.h>
78
79#include <asm/tlbflush.h>
80
81#define CREATE_TRACE_POINTS
82#include <trace/events/tlb.h>
83#include <trace/events/migrate.h>
84
85#include "internal.h"
86
87static struct kmem_cache *anon_vma_cachep;
88static struct kmem_cache *anon_vma_chain_cachep;
89
90static inline struct anon_vma *anon_vma_alloc(void)
91{
92 struct anon_vma *anon_vma;
93
94 anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL);
95 if (anon_vma) {
96 atomic_set(&anon_vma->refcount, 1);
97 anon_vma->num_children = 0;
98 anon_vma->num_active_vmas = 0;
99 anon_vma->parent = anon_vma;
100 /*
101 * Initialise the anon_vma root to point to itself. If called
102 * from fork, the root will be reset to the parents anon_vma.
103 */
104 anon_vma->root = anon_vma;
105 }
106
107 return anon_vma;
108}
109
110static inline void anon_vma_free(struct anon_vma *anon_vma)
111{
112 VM_BUG_ON(atomic_read(&anon_vma->refcount));
113
114 /*
115 * Synchronize against folio_lock_anon_vma_read() such that
116 * we can safely hold the lock without the anon_vma getting
117 * freed.
118 *
119 * Relies on the full mb implied by the atomic_dec_and_test() from
120 * put_anon_vma() against the acquire barrier implied by
121 * down_read_trylock() from folio_lock_anon_vma_read(). This orders:
122 *
123 * folio_lock_anon_vma_read() VS put_anon_vma()
124 * down_read_trylock() atomic_dec_and_test()
125 * LOCK MB
126 * atomic_read() rwsem_is_locked()
127 *
128 * LOCK should suffice since the actual taking of the lock must
129 * happen _before_ what follows.
130 */
131 might_sleep();
132 if (rwsem_is_locked(&anon_vma->root->rwsem)) {
133 anon_vma_lock_write(anon_vma);
134 anon_vma_unlock_write(anon_vma);
135 }
136
137 kmem_cache_free(anon_vma_cachep, anon_vma);
138}
139
140static inline struct anon_vma_chain *anon_vma_chain_alloc(gfp_t gfp)
141{
142 return kmem_cache_alloc(anon_vma_chain_cachep, gfp);
143}
144
145static void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain)
146{
147 kmem_cache_free(anon_vma_chain_cachep, anon_vma_chain);
148}
149
150static void anon_vma_chain_link(struct vm_area_struct *vma,
151 struct anon_vma_chain *avc,
152 struct anon_vma *anon_vma)
153{
154 avc->vma = vma;
155 avc->anon_vma = anon_vma;
156 list_add(&avc->same_vma, &vma->anon_vma_chain);
157 anon_vma_interval_tree_insert(avc, &anon_vma->rb_root);
158}
159
160/**
161 * __anon_vma_prepare - attach an anon_vma to a memory region
162 * @vma: the memory region in question
163 *
164 * This makes sure the memory mapping described by 'vma' has
165 * an 'anon_vma' attached to it, so that we can associate the
166 * anonymous pages mapped into it with that anon_vma.
167 *
168 * The common case will be that we already have one, which
169 * is handled inline by anon_vma_prepare(). But if
170 * not we either need to find an adjacent mapping that we
171 * can re-use the anon_vma from (very common when the only
172 * reason for splitting a vma has been mprotect()), or we
173 * allocate a new one.
174 *
175 * Anon-vma allocations are very subtle, because we may have
176 * optimistically looked up an anon_vma in folio_lock_anon_vma_read()
177 * and that may actually touch the rwsem even in the newly
178 * allocated vma (it depends on RCU to make sure that the
179 * anon_vma isn't actually destroyed).
180 *
181 * As a result, we need to do proper anon_vma locking even
182 * for the new allocation. At the same time, we do not want
183 * to do any locking for the common case of already having
184 * an anon_vma.
185 */
186int __anon_vma_prepare(struct vm_area_struct *vma)
187{
188 struct mm_struct *mm = vma->vm_mm;
189 struct anon_vma *anon_vma, *allocated;
190 struct anon_vma_chain *avc;
191
192 mmap_assert_locked(mm);
193 might_sleep();
194
195 avc = anon_vma_chain_alloc(GFP_KERNEL);
196 if (!avc)
197 goto out_enomem;
198
199 anon_vma = find_mergeable_anon_vma(vma);
200 allocated = NULL;
201 if (!anon_vma) {
202 anon_vma = anon_vma_alloc();
203 if (unlikely(!anon_vma))
204 goto out_enomem_free_avc;
205 anon_vma->num_children++; /* self-parent link for new root */
206 allocated = anon_vma;
207 }
208
209 anon_vma_lock_write(anon_vma);
210 /* page_table_lock to protect against threads */
211 spin_lock(&mm->page_table_lock);
212 if (likely(!vma->anon_vma)) {
213 vma->anon_vma = anon_vma;
214 anon_vma_chain_link(vma, avc, anon_vma);
215 anon_vma->num_active_vmas++;
216 allocated = NULL;
217 avc = NULL;
218 }
219 spin_unlock(&mm->page_table_lock);
220 anon_vma_unlock_write(anon_vma);
221
222 if (unlikely(allocated))
223 put_anon_vma(allocated);
224 if (unlikely(avc))
225 anon_vma_chain_free(avc);
226
227 return 0;
228
229 out_enomem_free_avc:
230 anon_vma_chain_free(avc);
231 out_enomem:
232 return -ENOMEM;
233}
234
235/*
236 * This is a useful helper function for locking the anon_vma root as
237 * we traverse the vma->anon_vma_chain, looping over anon_vma's that
238 * have the same vma.
239 *
240 * Such anon_vma's should have the same root, so you'd expect to see
241 * just a single mutex_lock for the whole traversal.
242 */
243static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma)
244{
245 struct anon_vma *new_root = anon_vma->root;
246 if (new_root != root) {
247 if (WARN_ON_ONCE(root))
248 up_write(&root->rwsem);
249 root = new_root;
250 down_write(&root->rwsem);
251 }
252 return root;
253}
254
255static inline void unlock_anon_vma_root(struct anon_vma *root)
256{
257 if (root)
258 up_write(&root->rwsem);
259}
260
261/*
262 * Attach the anon_vmas from src to dst.
263 * Returns 0 on success, -ENOMEM on failure.
264 *
265 * anon_vma_clone() is called by vma_expand(), vma_merge(), __split_vma(),
266 * copy_vma() and anon_vma_fork(). The first four want an exact copy of src,
267 * while the last one, anon_vma_fork(), may try to reuse an existing anon_vma to
268 * prevent endless growth of anon_vma. Since dst->anon_vma is set to NULL before
269 * call, we can identify this case by checking (!dst->anon_vma &&
270 * src->anon_vma).
271 *
272 * If (!dst->anon_vma && src->anon_vma) is true, this function tries to find
273 * and reuse existing anon_vma which has no vmas and only one child anon_vma.
274 * This prevents degradation of anon_vma hierarchy to endless linear chain in
275 * case of constantly forking task. On the other hand, an anon_vma with more
276 * than one child isn't reused even if there was no alive vma, thus rmap
277 * walker has a good chance of avoiding scanning the whole hierarchy when it
278 * searches where page is mapped.
279 */
280int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
281{
282 struct anon_vma_chain *avc, *pavc;
283 struct anon_vma *root = NULL;
284
285 list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
286 struct anon_vma *anon_vma;
287
288 avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN);
289 if (unlikely(!avc)) {
290 unlock_anon_vma_root(root);
291 root = NULL;
292 avc = anon_vma_chain_alloc(GFP_KERNEL);
293 if (!avc)
294 goto enomem_failure;
295 }
296 anon_vma = pavc->anon_vma;
297 root = lock_anon_vma_root(root, anon_vma);
298 anon_vma_chain_link(dst, avc, anon_vma);
299
300 /*
301 * Reuse existing anon_vma if it has no vma and only one
302 * anon_vma child.
303 *
304 * Root anon_vma is never reused:
305 * it has self-parent reference and at least one child.
306 */
307 if (!dst->anon_vma && src->anon_vma &&
308 anon_vma->num_children < 2 &&
309 anon_vma->num_active_vmas == 0)
310 dst->anon_vma = anon_vma;
311 }
312 if (dst->anon_vma)
313 dst->anon_vma->num_active_vmas++;
314 unlock_anon_vma_root(root);
315 return 0;
316
317 enomem_failure:
318 /*
319 * dst->anon_vma is dropped here otherwise its num_active_vmas can
320 * be incorrectly decremented in unlink_anon_vmas().
321 * We can safely do this because callers of anon_vma_clone() don't care
322 * about dst->anon_vma if anon_vma_clone() failed.
323 */
324 dst->anon_vma = NULL;
325 unlink_anon_vmas(dst);
326 return -ENOMEM;
327}
328
329/*
330 * Attach vma to its own anon_vma, as well as to the anon_vmas that
331 * the corresponding VMA in the parent process is attached to.
332 * Returns 0 on success, non-zero on failure.
333 */
334int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
335{
336 struct anon_vma_chain *avc;
337 struct anon_vma *anon_vma;
338 int error;
339
340 /* Don't bother if the parent process has no anon_vma here. */
341 if (!pvma->anon_vma)
342 return 0;
343
344 /* Drop inherited anon_vma, we'll reuse existing or allocate new. */
345 vma->anon_vma = NULL;
346
347 /*
348 * First, attach the new VMA to the parent VMA's anon_vmas,
349 * so rmap can find non-COWed pages in child processes.
350 */
351 error = anon_vma_clone(vma, pvma);
352 if (error)
353 return error;
354
355 /* An existing anon_vma has been reused, all done then. */
356 if (vma->anon_vma)
357 return 0;
358
359 /* Then add our own anon_vma. */
360 anon_vma = anon_vma_alloc();
361 if (!anon_vma)
362 goto out_error;
363 anon_vma->num_active_vmas++;
364 avc = anon_vma_chain_alloc(GFP_KERNEL);
365 if (!avc)
366 goto out_error_free_anon_vma;
367
368 /*
369 * The root anon_vma's rwsem is the lock actually used when we
370 * lock any of the anon_vmas in this anon_vma tree.
371 */
372 anon_vma->root = pvma->anon_vma->root;
373 anon_vma->parent = pvma->anon_vma;
374 /*
375 * With refcounts, an anon_vma can stay around longer than the
376 * process it belongs to. The root anon_vma needs to be pinned until
377 * this anon_vma is freed, because the lock lives in the root.
378 */
379 get_anon_vma(anon_vma->root);
380 /* Mark this anon_vma as the one where our new (COWed) pages go. */
381 vma->anon_vma = anon_vma;
382 anon_vma_lock_write(anon_vma);
383 anon_vma_chain_link(vma, avc, anon_vma);
384 anon_vma->parent->num_children++;
385 anon_vma_unlock_write(anon_vma);
386
387 return 0;
388
389 out_error_free_anon_vma:
390 put_anon_vma(anon_vma);
391 out_error:
392 unlink_anon_vmas(vma);
393 return -ENOMEM;
394}
395
396void unlink_anon_vmas(struct vm_area_struct *vma)
397{
398 struct anon_vma_chain *avc, *next;
399 struct anon_vma *root = NULL;
400
401 /*
402 * Unlink each anon_vma chained to the VMA. This list is ordered
403 * from newest to oldest, ensuring the root anon_vma gets freed last.
404 */
405 list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
406 struct anon_vma *anon_vma = avc->anon_vma;
407
408 root = lock_anon_vma_root(root, anon_vma);
409 anon_vma_interval_tree_remove(avc, &anon_vma->rb_root);
410
411 /*
412 * Leave empty anon_vmas on the list - we'll need
413 * to free them outside the lock.
414 */
415 if (RB_EMPTY_ROOT(&anon_vma->rb_root.rb_root)) {
416 anon_vma->parent->num_children--;
417 continue;
418 }
419
420 list_del(&avc->same_vma);
421 anon_vma_chain_free(avc);
422 }
423 if (vma->anon_vma) {
424 vma->anon_vma->num_active_vmas--;
425
426 /*
427 * vma would still be needed after unlink, and anon_vma will be prepared
428 * when handle fault.
429 */
430 vma->anon_vma = NULL;
431 }
432 unlock_anon_vma_root(root);
433
434 /*
435 * Iterate the list once more, it now only contains empty and unlinked
436 * anon_vmas, destroy them. Could not do before due to __put_anon_vma()
437 * needing to write-acquire the anon_vma->root->rwsem.
438 */
439 list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
440 struct anon_vma *anon_vma = avc->anon_vma;
441
442 VM_WARN_ON(anon_vma->num_children);
443 VM_WARN_ON(anon_vma->num_active_vmas);
444 put_anon_vma(anon_vma);
445
446 list_del(&avc->same_vma);
447 anon_vma_chain_free(avc);
448 }
449}
450
451static void anon_vma_ctor(void *data)
452{
453 struct anon_vma *anon_vma = data;
454
455 init_rwsem(&anon_vma->rwsem);
456 atomic_set(&anon_vma->refcount, 0);
457 anon_vma->rb_root = RB_ROOT_CACHED;
458}
459
460void __init anon_vma_init(void)
461{
462 anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
463 0, SLAB_TYPESAFE_BY_RCU|SLAB_PANIC|SLAB_ACCOUNT,
464 anon_vma_ctor);
465 anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain,
466 SLAB_PANIC|SLAB_ACCOUNT);
467}
468
469/*
470 * Getting a lock on a stable anon_vma from a page off the LRU is tricky!
471 *
472 * Since there is no serialization what so ever against folio_remove_rmap_*()
473 * the best this function can do is return a refcount increased anon_vma
474 * that might have been relevant to this page.
475 *
476 * The page might have been remapped to a different anon_vma or the anon_vma
477 * returned may already be freed (and even reused).
478 *
479 * In case it was remapped to a different anon_vma, the new anon_vma will be a
480 * child of the old anon_vma, and the anon_vma lifetime rules will therefore
481 * ensure that any anon_vma obtained from the page will still be valid for as
482 * long as we observe page_mapped() [ hence all those page_mapped() tests ].
483 *
484 * All users of this function must be very careful when walking the anon_vma
485 * chain and verify that the page in question is indeed mapped in it
486 * [ something equivalent to page_mapped_in_vma() ].
487 *
488 * Since anon_vma's slab is SLAB_TYPESAFE_BY_RCU and we know from
489 * folio_remove_rmap_*() that the anon_vma pointer from page->mapping is valid
490 * if there is a mapcount, we can dereference the anon_vma after observing
491 * those.
492 *
493 * NOTE: the caller should normally hold folio lock when calling this. If
494 * not, the caller needs to double check the anon_vma didn't change after
495 * taking the anon_vma lock for either read or write (UFFDIO_MOVE can modify it
496 * concurrently without folio lock protection). See folio_lock_anon_vma_read()
497 * which has already covered that, and comment above remap_pages().
498 */
499struct anon_vma *folio_get_anon_vma(const struct folio *folio)
500{
501 struct anon_vma *anon_vma = NULL;
502 unsigned long anon_mapping;
503
504 rcu_read_lock();
505 anon_mapping = (unsigned long)READ_ONCE(folio->mapping);
506 if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
507 goto out;
508 if (!folio_mapped(folio))
509 goto out;
510
511 anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
512 if (!atomic_inc_not_zero(&anon_vma->refcount)) {
513 anon_vma = NULL;
514 goto out;
515 }
516
517 /*
518 * If this folio is still mapped, then its anon_vma cannot have been
519 * freed. But if it has been unmapped, we have no security against the
520 * anon_vma structure being freed and reused (for another anon_vma:
521 * SLAB_TYPESAFE_BY_RCU guarantees that - so the atomic_inc_not_zero()
522 * above cannot corrupt).
523 */
524 if (!folio_mapped(folio)) {
525 rcu_read_unlock();
526 put_anon_vma(anon_vma);
527 return NULL;
528 }
529out:
530 rcu_read_unlock();
531
532 return anon_vma;
533}
534
535/*
536 * Similar to folio_get_anon_vma() except it locks the anon_vma.
537 *
538 * Its a little more complex as it tries to keep the fast path to a single
539 * atomic op -- the trylock. If we fail the trylock, we fall back to getting a
540 * reference like with folio_get_anon_vma() and then block on the mutex
541 * on !rwc->try_lock case.
542 */
543struct anon_vma *folio_lock_anon_vma_read(const struct folio *folio,
544 struct rmap_walk_control *rwc)
545{
546 struct anon_vma *anon_vma = NULL;
547 struct anon_vma *root_anon_vma;
548 unsigned long anon_mapping;
549
550retry:
551 rcu_read_lock();
552 anon_mapping = (unsigned long)READ_ONCE(folio->mapping);
553 if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
554 goto out;
555 if (!folio_mapped(folio))
556 goto out;
557
558 anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
559 root_anon_vma = READ_ONCE(anon_vma->root);
560 if (down_read_trylock(&root_anon_vma->rwsem)) {
561 /*
562 * folio_move_anon_rmap() might have changed the anon_vma as we
563 * might not hold the folio lock here.
564 */
565 if (unlikely((unsigned long)READ_ONCE(folio->mapping) !=
566 anon_mapping)) {
567 up_read(&root_anon_vma->rwsem);
568 rcu_read_unlock();
569 goto retry;
570 }
571
572 /*
573 * If the folio is still mapped, then this anon_vma is still
574 * its anon_vma, and holding the mutex ensures that it will
575 * not go away, see anon_vma_free().
576 */
577 if (!folio_mapped(folio)) {
578 up_read(&root_anon_vma->rwsem);
579 anon_vma = NULL;
580 }
581 goto out;
582 }
583
584 if (rwc && rwc->try_lock) {
585 anon_vma = NULL;
586 rwc->contended = true;
587 goto out;
588 }
589
590 /* trylock failed, we got to sleep */
591 if (!atomic_inc_not_zero(&anon_vma->refcount)) {
592 anon_vma = NULL;
593 goto out;
594 }
595
596 if (!folio_mapped(folio)) {
597 rcu_read_unlock();
598 put_anon_vma(anon_vma);
599 return NULL;
600 }
601
602 /* we pinned the anon_vma, its safe to sleep */
603 rcu_read_unlock();
604 anon_vma_lock_read(anon_vma);
605
606 /*
607 * folio_move_anon_rmap() might have changed the anon_vma as we might
608 * not hold the folio lock here.
609 */
610 if (unlikely((unsigned long)READ_ONCE(folio->mapping) !=
611 anon_mapping)) {
612 anon_vma_unlock_read(anon_vma);
613 put_anon_vma(anon_vma);
614 anon_vma = NULL;
615 goto retry;
616 }
617
618 if (atomic_dec_and_test(&anon_vma->refcount)) {
619 /*
620 * Oops, we held the last refcount, release the lock
621 * and bail -- can't simply use put_anon_vma() because
622 * we'll deadlock on the anon_vma_lock_write() recursion.
623 */
624 anon_vma_unlock_read(anon_vma);
625 __put_anon_vma(anon_vma);
626 anon_vma = NULL;
627 }
628
629 return anon_vma;
630
631out:
632 rcu_read_unlock();
633 return anon_vma;
634}
635
636#ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
637/*
638 * Flush TLB entries for recently unmapped pages from remote CPUs. It is
639 * important if a PTE was dirty when it was unmapped that it's flushed
640 * before any IO is initiated on the page to prevent lost writes. Similarly,
641 * it must be flushed before freeing to prevent data leakage.
642 */
643void try_to_unmap_flush(void)
644{
645 struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc;
646
647 if (!tlb_ubc->flush_required)
648 return;
649
650 arch_tlbbatch_flush(&tlb_ubc->arch);
651 tlb_ubc->flush_required = false;
652 tlb_ubc->writable = false;
653}
654
655/* Flush iff there are potentially writable TLB entries that can race with IO */
656void try_to_unmap_flush_dirty(void)
657{
658 struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc;
659
660 if (tlb_ubc->writable)
661 try_to_unmap_flush();
662}
663
664/*
665 * Bits 0-14 of mm->tlb_flush_batched record pending generations.
666 * Bits 16-30 of mm->tlb_flush_batched bit record flushed generations.
667 */
668#define TLB_FLUSH_BATCH_FLUSHED_SHIFT 16
669#define TLB_FLUSH_BATCH_PENDING_MASK \
670 ((1 << (TLB_FLUSH_BATCH_FLUSHED_SHIFT - 1)) - 1)
671#define TLB_FLUSH_BATCH_PENDING_LARGE \
672 (TLB_FLUSH_BATCH_PENDING_MASK / 2)
673
674static void set_tlb_ubc_flush_pending(struct mm_struct *mm, pte_t pteval,
675 unsigned long uaddr)
676{
677 struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc;
678 int batch;
679 bool writable = pte_dirty(pteval);
680
681 if (!pte_accessible(mm, pteval))
682 return;
683
684 arch_tlbbatch_add_pending(&tlb_ubc->arch, mm, uaddr);
685 tlb_ubc->flush_required = true;
686
687 /*
688 * Ensure compiler does not re-order the setting of tlb_flush_batched
689 * before the PTE is cleared.
690 */
691 barrier();
692 batch = atomic_read(&mm->tlb_flush_batched);
693retry:
694 if ((batch & TLB_FLUSH_BATCH_PENDING_MASK) > TLB_FLUSH_BATCH_PENDING_LARGE) {
695 /*
696 * Prevent `pending' from catching up with `flushed' because of
697 * overflow. Reset `pending' and `flushed' to be 1 and 0 if
698 * `pending' becomes large.
699 */
700 if (!atomic_try_cmpxchg(&mm->tlb_flush_batched, &batch, 1))
701 goto retry;
702 } else {
703 atomic_inc(&mm->tlb_flush_batched);
704 }
705
706 /*
707 * If the PTE was dirty then it's best to assume it's writable. The
708 * caller must use try_to_unmap_flush_dirty() or try_to_unmap_flush()
709 * before the page is queued for IO.
710 */
711 if (writable)
712 tlb_ubc->writable = true;
713}
714
715/*
716 * Returns true if the TLB flush should be deferred to the end of a batch of
717 * unmap operations to reduce IPIs.
718 */
719static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
720{
721 if (!(flags & TTU_BATCH_FLUSH))
722 return false;
723
724 return arch_tlbbatch_should_defer(mm);
725}
726
727/*
728 * Reclaim unmaps pages under the PTL but do not flush the TLB prior to
729 * releasing the PTL if TLB flushes are batched. It's possible for a parallel
730 * operation such as mprotect or munmap to race between reclaim unmapping
731 * the page and flushing the page. If this race occurs, it potentially allows
732 * access to data via a stale TLB entry. Tracking all mm's that have TLB
733 * batching in flight would be expensive during reclaim so instead track
734 * whether TLB batching occurred in the past and if so then do a flush here
735 * if required. This will cost one additional flush per reclaim cycle paid
736 * by the first operation at risk such as mprotect and mumap.
737 *
738 * This must be called under the PTL so that an access to tlb_flush_batched
739 * that is potentially a "reclaim vs mprotect/munmap/etc" race will synchronise
740 * via the PTL.
741 */
742void flush_tlb_batched_pending(struct mm_struct *mm)
743{
744 int batch = atomic_read(&mm->tlb_flush_batched);
745 int pending = batch & TLB_FLUSH_BATCH_PENDING_MASK;
746 int flushed = batch >> TLB_FLUSH_BATCH_FLUSHED_SHIFT;
747
748 if (pending != flushed) {
749 arch_flush_tlb_batched_pending(mm);
750 /*
751 * If the new TLB flushing is pending during flushing, leave
752 * mm->tlb_flush_batched as is, to avoid losing flushing.
753 */
754 atomic_cmpxchg(&mm->tlb_flush_batched, batch,
755 pending | (pending << TLB_FLUSH_BATCH_FLUSHED_SHIFT));
756 }
757}
758#else
759static void set_tlb_ubc_flush_pending(struct mm_struct *mm, pte_t pteval,
760 unsigned long uaddr)
761{
762}
763
764static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
765{
766 return false;
767}
768#endif /* CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH */
769
770/**
771 * page_address_in_vma - The virtual address of a page in this VMA.
772 * @folio: The folio containing the page.
773 * @page: The page within the folio.
774 * @vma: The VMA we need to know the address in.
775 *
776 * Calculates the user virtual address of this page in the specified VMA.
777 * It is the caller's responsibililty to check the page is actually
778 * within the VMA. There may not currently be a PTE pointing at this
779 * page, but if a page fault occurs at this address, this is the page
780 * which will be accessed.
781 *
782 * Context: Caller should hold a reference to the folio. Caller should
783 * hold a lock (eg the i_mmap_lock or the mmap_lock) which keeps the
784 * VMA from being altered.
785 *
786 * Return: The virtual address corresponding to this page in the VMA.
787 */
788unsigned long page_address_in_vma(const struct folio *folio,
789 const struct page *page, const struct vm_area_struct *vma)
790{
791 if (folio_test_anon(folio)) {
792 struct anon_vma *page__anon_vma = folio_anon_vma(folio);
793 /*
794 * Note: swapoff's unuse_vma() is more efficient with this
795 * check, and needs it to match anon_vma when KSM is active.
796 */
797 if (!vma->anon_vma || !page__anon_vma ||
798 vma->anon_vma->root != page__anon_vma->root)
799 return -EFAULT;
800 } else if (!vma->vm_file) {
801 return -EFAULT;
802 } else if (vma->vm_file->f_mapping != folio->mapping) {
803 return -EFAULT;
804 }
805
806 /* KSM folios don't reach here because of the !page__anon_vma check */
807 return vma_address(vma, page_pgoff(folio, page), 1);
808}
809
810/*
811 * Returns the actual pmd_t* where we expect 'address' to be mapped from, or
812 * NULL if it doesn't exist. No guarantees / checks on what the pmd_t*
813 * represents.
814 */
815pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address)
816{
817 pgd_t *pgd;
818 p4d_t *p4d;
819 pud_t *pud;
820 pmd_t *pmd = NULL;
821
822 pgd = pgd_offset(mm, address);
823 if (!pgd_present(*pgd))
824 goto out;
825
826 p4d = p4d_offset(pgd, address);
827 if (!p4d_present(*p4d))
828 goto out;
829
830 pud = pud_offset(p4d, address);
831 if (!pud_present(*pud))
832 goto out;
833
834 pmd = pmd_offset(pud, address);
835out:
836 return pmd;
837}
838
839struct folio_referenced_arg {
840 int mapcount;
841 int referenced;
842 unsigned long vm_flags;
843 struct mem_cgroup *memcg;
844};
845
846/*
847 * arg: folio_referenced_arg will be passed
848 */
849static bool folio_referenced_one(struct folio *folio,
850 struct vm_area_struct *vma, unsigned long address, void *arg)
851{
852 struct folio_referenced_arg *pra = arg;
853 DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
854 int referenced = 0;
855 unsigned long start = address, ptes = 0;
856
857 while (page_vma_mapped_walk(&pvmw)) {
858 address = pvmw.address;
859
860 if (vma->vm_flags & VM_LOCKED) {
861 if (!folio_test_large(folio) || !pvmw.pte) {
862 /* Restore the mlock which got missed */
863 mlock_vma_folio(folio, vma);
864 page_vma_mapped_walk_done(&pvmw);
865 pra->vm_flags |= VM_LOCKED;
866 return false; /* To break the loop */
867 }
868 /*
869 * For large folio fully mapped to VMA, will
870 * be handled after the pvmw loop.
871 *
872 * For large folio cross VMA boundaries, it's
873 * expected to be picked by page reclaim. But
874 * should skip reference of pages which are in
875 * the range of VM_LOCKED vma. As page reclaim
876 * should just count the reference of pages out
877 * the range of VM_LOCKED vma.
878 */
879 ptes++;
880 pra->mapcount--;
881 continue;
882 }
883
884 /*
885 * Skip the non-shared swapbacked folio mapped solely by
886 * the exiting or OOM-reaped process. This avoids redundant
887 * swap-out followed by an immediate unmap.
888 */
889 if ((!atomic_read(&vma->vm_mm->mm_users) ||
890 check_stable_address_space(vma->vm_mm)) &&
891 folio_test_anon(folio) && folio_test_swapbacked(folio) &&
892 !folio_likely_mapped_shared(folio)) {
893 pra->referenced = -1;
894 page_vma_mapped_walk_done(&pvmw);
895 return false;
896 }
897
898 if (lru_gen_enabled() && pvmw.pte) {
899 if (lru_gen_look_around(&pvmw))
900 referenced++;
901 } else if (pvmw.pte) {
902 if (ptep_clear_flush_young_notify(vma, address,
903 pvmw.pte))
904 referenced++;
905 } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
906 if (pmdp_clear_flush_young_notify(vma, address,
907 pvmw.pmd))
908 referenced++;
909 } else {
910 /* unexpected pmd-mapped folio? */
911 WARN_ON_ONCE(1);
912 }
913
914 pra->mapcount--;
915 }
916
917 if ((vma->vm_flags & VM_LOCKED) &&
918 folio_test_large(folio) &&
919 folio_within_vma(folio, vma)) {
920 unsigned long s_align, e_align;
921
922 s_align = ALIGN_DOWN(start, PMD_SIZE);
923 e_align = ALIGN_DOWN(start + folio_size(folio) - 1, PMD_SIZE);
924
925 /* folio doesn't cross page table boundary and fully mapped */
926 if ((s_align == e_align) && (ptes == folio_nr_pages(folio))) {
927 /* Restore the mlock which got missed */
928 mlock_vma_folio(folio, vma);
929 pra->vm_flags |= VM_LOCKED;
930 return false; /* To break the loop */
931 }
932 }
933
934 if (referenced)
935 folio_clear_idle(folio);
936 if (folio_test_clear_young(folio))
937 referenced++;
938
939 if (referenced) {
940 pra->referenced++;
941 pra->vm_flags |= vma->vm_flags & ~VM_LOCKED;
942 }
943
944 if (!pra->mapcount)
945 return false; /* To break the loop */
946
947 return true;
948}
949
950static bool invalid_folio_referenced_vma(struct vm_area_struct *vma, void *arg)
951{
952 struct folio_referenced_arg *pra = arg;
953 struct mem_cgroup *memcg = pra->memcg;
954
955 /*
956 * Ignore references from this mapping if it has no recency. If the
957 * folio has been used in another mapping, we will catch it; if this
958 * other mapping is already gone, the unmap path will have set the
959 * referenced flag or activated the folio in zap_pte_range().
960 */
961 if (!vma_has_recency(vma))
962 return true;
963
964 /*
965 * If we are reclaiming on behalf of a cgroup, skip counting on behalf
966 * of references from different cgroups.
967 */
968 if (memcg && !mm_match_cgroup(vma->vm_mm, memcg))
969 return true;
970
971 return false;
972}
973
974/**
975 * folio_referenced() - Test if the folio was referenced.
976 * @folio: The folio to test.
977 * @is_locked: Caller holds lock on the folio.
978 * @memcg: target memory cgroup
979 * @vm_flags: A combination of all the vma->vm_flags which referenced the folio.
980 *
981 * Quick test_and_clear_referenced for all mappings of a folio,
982 *
983 * Return: The number of mappings which referenced the folio. Return -1 if
984 * the function bailed out due to rmap lock contention.
985 */
986int folio_referenced(struct folio *folio, int is_locked,
987 struct mem_cgroup *memcg, unsigned long *vm_flags)
988{
989 bool we_locked = false;
990 struct folio_referenced_arg pra = {
991 .mapcount = folio_mapcount(folio),
992 .memcg = memcg,
993 };
994 struct rmap_walk_control rwc = {
995 .rmap_one = folio_referenced_one,
996 .arg = (void *)&pra,
997 .anon_lock = folio_lock_anon_vma_read,
998 .try_lock = true,
999 .invalid_vma = invalid_folio_referenced_vma,
1000 };
1001
1002 *vm_flags = 0;
1003 if (!pra.mapcount)
1004 return 0;
1005
1006 if (!folio_raw_mapping(folio))
1007 return 0;
1008
1009 if (!is_locked && (!folio_test_anon(folio) || folio_test_ksm(folio))) {
1010 we_locked = folio_trylock(folio);
1011 if (!we_locked)
1012 return 1;
1013 }
1014
1015 rmap_walk(folio, &rwc);
1016 *vm_flags = pra.vm_flags;
1017
1018 if (we_locked)
1019 folio_unlock(folio);
1020
1021 return rwc.contended ? -1 : pra.referenced;
1022}
1023
1024static int page_vma_mkclean_one(struct page_vma_mapped_walk *pvmw)
1025{
1026 int cleaned = 0;
1027 struct vm_area_struct *vma = pvmw->vma;
1028 struct mmu_notifier_range range;
1029 unsigned long address = pvmw->address;
1030
1031 /*
1032 * We have to assume the worse case ie pmd for invalidation. Note that
1033 * the folio can not be freed from this function.
1034 */
1035 mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_PAGE, 0,
1036 vma->vm_mm, address, vma_address_end(pvmw));
1037 mmu_notifier_invalidate_range_start(&range);
1038
1039 while (page_vma_mapped_walk(pvmw)) {
1040 int ret = 0;
1041
1042 address = pvmw->address;
1043 if (pvmw->pte) {
1044 pte_t *pte = pvmw->pte;
1045 pte_t entry = ptep_get(pte);
1046
1047 if (!pte_dirty(entry) && !pte_write(entry))
1048 continue;
1049
1050 flush_cache_page(vma, address, pte_pfn(entry));
1051 entry = ptep_clear_flush(vma, address, pte);
1052 entry = pte_wrprotect(entry);
1053 entry = pte_mkclean(entry);
1054 set_pte_at(vma->vm_mm, address, pte, entry);
1055 ret = 1;
1056 } else {
1057#ifdef CONFIG_TRANSPARENT_HUGEPAGE
1058 pmd_t *pmd = pvmw->pmd;
1059 pmd_t entry;
1060
1061 if (!pmd_dirty(*pmd) && !pmd_write(*pmd))
1062 continue;
1063
1064 flush_cache_range(vma, address,
1065 address + HPAGE_PMD_SIZE);
1066 entry = pmdp_invalidate(vma, address, pmd);
1067 entry = pmd_wrprotect(entry);
1068 entry = pmd_mkclean(entry);
1069 set_pmd_at(vma->vm_mm, address, pmd, entry);
1070 ret = 1;
1071#else
1072 /* unexpected pmd-mapped folio? */
1073 WARN_ON_ONCE(1);
1074#endif
1075 }
1076
1077 if (ret)
1078 cleaned++;
1079 }
1080
1081 mmu_notifier_invalidate_range_end(&range);
1082
1083 return cleaned;
1084}
1085
1086static bool page_mkclean_one(struct folio *folio, struct vm_area_struct *vma,
1087 unsigned long address, void *arg)
1088{
1089 DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, PVMW_SYNC);
1090 int *cleaned = arg;
1091
1092 *cleaned += page_vma_mkclean_one(&pvmw);
1093
1094 return true;
1095}
1096
1097static bool invalid_mkclean_vma(struct vm_area_struct *vma, void *arg)
1098{
1099 if (vma->vm_flags & VM_SHARED)
1100 return false;
1101
1102 return true;
1103}
1104
1105int folio_mkclean(struct folio *folio)
1106{
1107 int cleaned = 0;
1108 struct address_space *mapping;
1109 struct rmap_walk_control rwc = {
1110 .arg = (void *)&cleaned,
1111 .rmap_one = page_mkclean_one,
1112 .invalid_vma = invalid_mkclean_vma,
1113 };
1114
1115 BUG_ON(!folio_test_locked(folio));
1116
1117 if (!folio_mapped(folio))
1118 return 0;
1119
1120 mapping = folio_mapping(folio);
1121 if (!mapping)
1122 return 0;
1123
1124 rmap_walk(folio, &rwc);
1125
1126 return cleaned;
1127}
1128EXPORT_SYMBOL_GPL(folio_mkclean);
1129
1130/**
1131 * pfn_mkclean_range - Cleans the PTEs (including PMDs) mapped with range of
1132 * [@pfn, @pfn + @nr_pages) at the specific offset (@pgoff)
1133 * within the @vma of shared mappings. And since clean PTEs
1134 * should also be readonly, write protects them too.
1135 * @pfn: start pfn.
1136 * @nr_pages: number of physically contiguous pages srarting with @pfn.
1137 * @pgoff: page offset that the @pfn mapped with.
1138 * @vma: vma that @pfn mapped within.
1139 *
1140 * Returns the number of cleaned PTEs (including PMDs).
1141 */
1142int pfn_mkclean_range(unsigned long pfn, unsigned long nr_pages, pgoff_t pgoff,
1143 struct vm_area_struct *vma)
1144{
1145 struct page_vma_mapped_walk pvmw = {
1146 .pfn = pfn,
1147 .nr_pages = nr_pages,
1148 .pgoff = pgoff,
1149 .vma = vma,
1150 .flags = PVMW_SYNC,
1151 };
1152
1153 if (invalid_mkclean_vma(vma, NULL))
1154 return 0;
1155
1156 pvmw.address = vma_address(vma, pgoff, nr_pages);
1157 VM_BUG_ON_VMA(pvmw.address == -EFAULT, vma);
1158
1159 return page_vma_mkclean_one(&pvmw);
1160}
1161
1162static __always_inline unsigned int __folio_add_rmap(struct folio *folio,
1163 struct page *page, int nr_pages, enum rmap_level level,
1164 int *nr_pmdmapped)
1165{
1166 atomic_t *mapped = &folio->_nr_pages_mapped;
1167 const int orig_nr_pages = nr_pages;
1168 int first = 0, nr = 0;
1169
1170 __folio_rmap_sanity_checks(folio, page, nr_pages, level);
1171
1172 switch (level) {
1173 case RMAP_LEVEL_PTE:
1174 if (!folio_test_large(folio)) {
1175 nr = atomic_inc_and_test(&folio->_mapcount);
1176 break;
1177 }
1178
1179 do {
1180 first += atomic_inc_and_test(&page->_mapcount);
1181 } while (page++, --nr_pages > 0);
1182
1183 if (first &&
1184 atomic_add_return_relaxed(first, mapped) < ENTIRELY_MAPPED)
1185 nr = first;
1186
1187 atomic_add(orig_nr_pages, &folio->_large_mapcount);
1188 break;
1189 case RMAP_LEVEL_PMD:
1190 first = atomic_inc_and_test(&folio->_entire_mapcount);
1191 if (first) {
1192 nr = atomic_add_return_relaxed(ENTIRELY_MAPPED, mapped);
1193 if (likely(nr < ENTIRELY_MAPPED + ENTIRELY_MAPPED)) {
1194 *nr_pmdmapped = folio_nr_pages(folio);
1195 nr = *nr_pmdmapped - (nr & FOLIO_PAGES_MAPPED);
1196 /* Raced ahead of a remove and another add? */
1197 if (unlikely(nr < 0))
1198 nr = 0;
1199 } else {
1200 /* Raced ahead of a remove of ENTIRELY_MAPPED */
1201 nr = 0;
1202 }
1203 }
1204 atomic_inc(&folio->_large_mapcount);
1205 break;
1206 }
1207 return nr;
1208}
1209
1210/**
1211 * folio_move_anon_rmap - move a folio to our anon_vma
1212 * @folio: The folio to move to our anon_vma
1213 * @vma: The vma the folio belongs to
1214 *
1215 * When a folio belongs exclusively to one process after a COW event,
1216 * that folio can be moved into the anon_vma that belongs to just that
1217 * process, so the rmap code will not search the parent or sibling processes.
1218 */
1219void folio_move_anon_rmap(struct folio *folio, struct vm_area_struct *vma)
1220{
1221 void *anon_vma = vma->anon_vma;
1222
1223 VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
1224 VM_BUG_ON_VMA(!anon_vma, vma);
1225
1226 anon_vma += PAGE_MAPPING_ANON;
1227 /*
1228 * Ensure that anon_vma and the PAGE_MAPPING_ANON bit are written
1229 * simultaneously, so a concurrent reader (eg folio_referenced()'s
1230 * folio_test_anon()) will not see one without the other.
1231 */
1232 WRITE_ONCE(folio->mapping, anon_vma);
1233}
1234
1235/**
1236 * __folio_set_anon - set up a new anonymous rmap for a folio
1237 * @folio: The folio to set up the new anonymous rmap for.
1238 * @vma: VM area to add the folio to.
1239 * @address: User virtual address of the mapping
1240 * @exclusive: Whether the folio is exclusive to the process.
1241 */
1242static void __folio_set_anon(struct folio *folio, struct vm_area_struct *vma,
1243 unsigned long address, bool exclusive)
1244{
1245 struct anon_vma *anon_vma = vma->anon_vma;
1246
1247 BUG_ON(!anon_vma);
1248
1249 /*
1250 * If the folio isn't exclusive to this vma, we must use the _oldest_
1251 * possible anon_vma for the folio mapping!
1252 */
1253 if (!exclusive)
1254 anon_vma = anon_vma->root;
1255
1256 /*
1257 * page_idle does a lockless/optimistic rmap scan on folio->mapping.
1258 * Make sure the compiler doesn't split the stores of anon_vma and
1259 * the PAGE_MAPPING_ANON type identifier, otherwise the rmap code
1260 * could mistake the mapping for a struct address_space and crash.
1261 */
1262 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1263 WRITE_ONCE(folio->mapping, (struct address_space *) anon_vma);
1264 folio->index = linear_page_index(vma, address);
1265}
1266
1267/**
1268 * __page_check_anon_rmap - sanity check anonymous rmap addition
1269 * @folio: The folio containing @page.
1270 * @page: the page to check the mapping of
1271 * @vma: the vm area in which the mapping is added
1272 * @address: the user virtual address mapped
1273 */
1274static void __page_check_anon_rmap(const struct folio *folio,
1275 const struct page *page, struct vm_area_struct *vma,
1276 unsigned long address)
1277{
1278 /*
1279 * The page's anon-rmap details (mapping and index) are guaranteed to
1280 * be set up correctly at this point.
1281 *
1282 * We have exclusion against folio_add_anon_rmap_*() because the caller
1283 * always holds the page locked.
1284 *
1285 * We have exclusion against folio_add_new_anon_rmap because those pages
1286 * are initially only visible via the pagetables, and the pte is locked
1287 * over the call to folio_add_new_anon_rmap.
1288 */
1289 VM_BUG_ON_FOLIO(folio_anon_vma(folio)->root != vma->anon_vma->root,
1290 folio);
1291 VM_BUG_ON_PAGE(page_pgoff(folio, page) != linear_page_index(vma, address),
1292 page);
1293}
1294
1295static void __folio_mod_stat(struct folio *folio, int nr, int nr_pmdmapped)
1296{
1297 int idx;
1298
1299 if (nr) {
1300 idx = folio_test_anon(folio) ? NR_ANON_MAPPED : NR_FILE_MAPPED;
1301 __lruvec_stat_mod_folio(folio, idx, nr);
1302 }
1303 if (nr_pmdmapped) {
1304 if (folio_test_anon(folio)) {
1305 idx = NR_ANON_THPS;
1306 __lruvec_stat_mod_folio(folio, idx, nr_pmdmapped);
1307 } else {
1308 /* NR_*_PMDMAPPED are not maintained per-memcg */
1309 idx = folio_test_swapbacked(folio) ?
1310 NR_SHMEM_PMDMAPPED : NR_FILE_PMDMAPPED;
1311 __mod_node_page_state(folio_pgdat(folio), idx,
1312 nr_pmdmapped);
1313 }
1314 }
1315}
1316
1317static __always_inline void __folio_add_anon_rmap(struct folio *folio,
1318 struct page *page, int nr_pages, struct vm_area_struct *vma,
1319 unsigned long address, rmap_t flags, enum rmap_level level)
1320{
1321 int i, nr, nr_pmdmapped = 0;
1322
1323 VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio);
1324
1325 nr = __folio_add_rmap(folio, page, nr_pages, level, &nr_pmdmapped);
1326
1327 if (likely(!folio_test_ksm(folio)))
1328 __page_check_anon_rmap(folio, page, vma, address);
1329
1330 __folio_mod_stat(folio, nr, nr_pmdmapped);
1331
1332 if (flags & RMAP_EXCLUSIVE) {
1333 switch (level) {
1334 case RMAP_LEVEL_PTE:
1335 for (i = 0; i < nr_pages; i++)
1336 SetPageAnonExclusive(page + i);
1337 break;
1338 case RMAP_LEVEL_PMD:
1339 SetPageAnonExclusive(page);
1340 break;
1341 }
1342 }
1343 for (i = 0; i < nr_pages; i++) {
1344 struct page *cur_page = page + i;
1345
1346 /* While PTE-mapping a THP we have a PMD and a PTE mapping. */
1347 VM_WARN_ON_FOLIO((atomic_read(&cur_page->_mapcount) > 0 ||
1348 (folio_test_large(folio) &&
1349 folio_entire_mapcount(folio) > 1)) &&
1350 PageAnonExclusive(cur_page), folio);
1351 }
1352
1353 /*
1354 * For large folio, only mlock it if it's fully mapped to VMA. It's
1355 * not easy to check whether the large folio is fully mapped to VMA
1356 * here. Only mlock normal 4K folio and leave page reclaim to handle
1357 * large folio.
1358 */
1359 if (!folio_test_large(folio))
1360 mlock_vma_folio(folio, vma);
1361}
1362
1363/**
1364 * folio_add_anon_rmap_ptes - add PTE mappings to a page range of an anon folio
1365 * @folio: The folio to add the mappings to
1366 * @page: The first page to add
1367 * @nr_pages: The number of pages which will be mapped
1368 * @vma: The vm area in which the mappings are added
1369 * @address: The user virtual address of the first page to map
1370 * @flags: The rmap flags
1371 *
1372 * The page range of folio is defined by [first_page, first_page + nr_pages)
1373 *
1374 * The caller needs to hold the page table lock, and the page must be locked in
1375 * the anon_vma case: to serialize mapping,index checking after setting,
1376 * and to ensure that an anon folio is not being upgraded racily to a KSM folio
1377 * (but KSM folios are never downgraded).
1378 */
1379void folio_add_anon_rmap_ptes(struct folio *folio, struct page *page,
1380 int nr_pages, struct vm_area_struct *vma, unsigned long address,
1381 rmap_t flags)
1382{
1383 __folio_add_anon_rmap(folio, page, nr_pages, vma, address, flags,
1384 RMAP_LEVEL_PTE);
1385}
1386
1387/**
1388 * folio_add_anon_rmap_pmd - add a PMD mapping to a page range of an anon folio
1389 * @folio: The folio to add the mapping to
1390 * @page: The first page to add
1391 * @vma: The vm area in which the mapping is added
1392 * @address: The user virtual address of the first page to map
1393 * @flags: The rmap flags
1394 *
1395 * The page range of folio is defined by [first_page, first_page + HPAGE_PMD_NR)
1396 *
1397 * The caller needs to hold the page table lock, and the page must be locked in
1398 * the anon_vma case: to serialize mapping,index checking after setting.
1399 */
1400void folio_add_anon_rmap_pmd(struct folio *folio, struct page *page,
1401 struct vm_area_struct *vma, unsigned long address, rmap_t flags)
1402{
1403#ifdef CONFIG_TRANSPARENT_HUGEPAGE
1404 __folio_add_anon_rmap(folio, page, HPAGE_PMD_NR, vma, address, flags,
1405 RMAP_LEVEL_PMD);
1406#else
1407 WARN_ON_ONCE(true);
1408#endif
1409}
1410
1411/**
1412 * folio_add_new_anon_rmap - Add mapping to a new anonymous folio.
1413 * @folio: The folio to add the mapping to.
1414 * @vma: the vm area in which the mapping is added
1415 * @address: the user virtual address mapped
1416 * @flags: The rmap flags
1417 *
1418 * Like folio_add_anon_rmap_*() but must only be called on *new* folios.
1419 * This means the inc-and-test can be bypassed.
1420 * The folio doesn't necessarily need to be locked while it's exclusive
1421 * unless two threads map it concurrently. However, the folio must be
1422 * locked if it's shared.
1423 *
1424 * If the folio is pmd-mappable, it is accounted as a THP.
1425 */
1426void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
1427 unsigned long address, rmap_t flags)
1428{
1429 const int nr = folio_nr_pages(folio);
1430 const bool exclusive = flags & RMAP_EXCLUSIVE;
1431 int nr_pmdmapped = 0;
1432
1433 VM_WARN_ON_FOLIO(folio_test_hugetlb(folio), folio);
1434 VM_WARN_ON_FOLIO(!exclusive && !folio_test_locked(folio), folio);
1435 VM_BUG_ON_VMA(address < vma->vm_start ||
1436 address + (nr << PAGE_SHIFT) > vma->vm_end, vma);
1437
1438 /*
1439 * VM_DROPPABLE mappings don't swap; instead they're just dropped when
1440 * under memory pressure.
1441 */
1442 if (!folio_test_swapbacked(folio) && !(vma->vm_flags & VM_DROPPABLE))
1443 __folio_set_swapbacked(folio);
1444 __folio_set_anon(folio, vma, address, exclusive);
1445
1446 if (likely(!folio_test_large(folio))) {
1447 /* increment count (starts at -1) */
1448 atomic_set(&folio->_mapcount, 0);
1449 if (exclusive)
1450 SetPageAnonExclusive(&folio->page);
1451 } else if (!folio_test_pmd_mappable(folio)) {
1452 int i;
1453
1454 for (i = 0; i < nr; i++) {
1455 struct page *page = folio_page(folio, i);
1456
1457 /* increment count (starts at -1) */
1458 atomic_set(&page->_mapcount, 0);
1459 if (exclusive)
1460 SetPageAnonExclusive(page);
1461 }
1462
1463 /* increment count (starts at -1) */
1464 atomic_set(&folio->_large_mapcount, nr - 1);
1465 atomic_set(&folio->_nr_pages_mapped, nr);
1466 } else {
1467 /* increment count (starts at -1) */
1468 atomic_set(&folio->_entire_mapcount, 0);
1469 /* increment count (starts at -1) */
1470 atomic_set(&folio->_large_mapcount, 0);
1471 atomic_set(&folio->_nr_pages_mapped, ENTIRELY_MAPPED);
1472 if (exclusive)
1473 SetPageAnonExclusive(&folio->page);
1474 nr_pmdmapped = nr;
1475 }
1476
1477 __folio_mod_stat(folio, nr, nr_pmdmapped);
1478 mod_mthp_stat(folio_order(folio), MTHP_STAT_NR_ANON, 1);
1479}
1480
1481static __always_inline void __folio_add_file_rmap(struct folio *folio,
1482 struct page *page, int nr_pages, struct vm_area_struct *vma,
1483 enum rmap_level level)
1484{
1485 int nr, nr_pmdmapped = 0;
1486
1487 VM_WARN_ON_FOLIO(folio_test_anon(folio), folio);
1488
1489 nr = __folio_add_rmap(folio, page, nr_pages, level, &nr_pmdmapped);
1490 __folio_mod_stat(folio, nr, nr_pmdmapped);
1491
1492 /* See comments in folio_add_anon_rmap_*() */
1493 if (!folio_test_large(folio))
1494 mlock_vma_folio(folio, vma);
1495}
1496
1497/**
1498 * folio_add_file_rmap_ptes - add PTE mappings to a page range of a folio
1499 * @folio: The folio to add the mappings to
1500 * @page: The first page to add
1501 * @nr_pages: The number of pages that will be mapped using PTEs
1502 * @vma: The vm area in which the mappings are added
1503 *
1504 * The page range of the folio is defined by [page, page + nr_pages)
1505 *
1506 * The caller needs to hold the page table lock.
1507 */
1508void folio_add_file_rmap_ptes(struct folio *folio, struct page *page,
1509 int nr_pages, struct vm_area_struct *vma)
1510{
1511 __folio_add_file_rmap(folio, page, nr_pages, vma, RMAP_LEVEL_PTE);
1512}
1513
1514/**
1515 * folio_add_file_rmap_pmd - add a PMD mapping to a page range of a folio
1516 * @folio: The folio to add the mapping to
1517 * @page: The first page to add
1518 * @vma: The vm area in which the mapping is added
1519 *
1520 * The page range of the folio is defined by [page, page + HPAGE_PMD_NR)
1521 *
1522 * The caller needs to hold the page table lock.
1523 */
1524void folio_add_file_rmap_pmd(struct folio *folio, struct page *page,
1525 struct vm_area_struct *vma)
1526{
1527#ifdef CONFIG_TRANSPARENT_HUGEPAGE
1528 __folio_add_file_rmap(folio, page, HPAGE_PMD_NR, vma, RMAP_LEVEL_PMD);
1529#else
1530 WARN_ON_ONCE(true);
1531#endif
1532}
1533
1534static __always_inline void __folio_remove_rmap(struct folio *folio,
1535 struct page *page, int nr_pages, struct vm_area_struct *vma,
1536 enum rmap_level level)
1537{
1538 atomic_t *mapped = &folio->_nr_pages_mapped;
1539 int last = 0, nr = 0, nr_pmdmapped = 0;
1540 bool partially_mapped = false;
1541
1542 __folio_rmap_sanity_checks(folio, page, nr_pages, level);
1543
1544 switch (level) {
1545 case RMAP_LEVEL_PTE:
1546 if (!folio_test_large(folio)) {
1547 nr = atomic_add_negative(-1, &folio->_mapcount);
1548 break;
1549 }
1550
1551 atomic_sub(nr_pages, &folio->_large_mapcount);
1552 do {
1553 last += atomic_add_negative(-1, &page->_mapcount);
1554 } while (page++, --nr_pages > 0);
1555
1556 if (last &&
1557 atomic_sub_return_relaxed(last, mapped) < ENTIRELY_MAPPED)
1558 nr = last;
1559
1560 partially_mapped = nr && atomic_read(mapped);
1561 break;
1562 case RMAP_LEVEL_PMD:
1563 atomic_dec(&folio->_large_mapcount);
1564 last = atomic_add_negative(-1, &folio->_entire_mapcount);
1565 if (last) {
1566 nr = atomic_sub_return_relaxed(ENTIRELY_MAPPED, mapped);
1567 if (likely(nr < ENTIRELY_MAPPED)) {
1568 nr_pmdmapped = folio_nr_pages(folio);
1569 nr = nr_pmdmapped - (nr & FOLIO_PAGES_MAPPED);
1570 /* Raced ahead of another remove and an add? */
1571 if (unlikely(nr < 0))
1572 nr = 0;
1573 } else {
1574 /* An add of ENTIRELY_MAPPED raced ahead */
1575 nr = 0;
1576 }
1577 }
1578
1579 partially_mapped = nr && nr < nr_pmdmapped;
1580 break;
1581 }
1582
1583 /*
1584 * Queue anon large folio for deferred split if at least one page of
1585 * the folio is unmapped and at least one page is still mapped.
1586 *
1587 * Check partially_mapped first to ensure it is a large folio.
1588 */
1589 if (partially_mapped && folio_test_anon(folio) &&
1590 !folio_test_partially_mapped(folio))
1591 deferred_split_folio(folio, true);
1592
1593 __folio_mod_stat(folio, -nr, -nr_pmdmapped);
1594
1595 /*
1596 * It would be tidy to reset folio_test_anon mapping when fully
1597 * unmapped, but that might overwrite a racing folio_add_anon_rmap_*()
1598 * which increments mapcount after us but sets mapping before us:
1599 * so leave the reset to free_pages_prepare, and remember that
1600 * it's only reliable while mapped.
1601 */
1602
1603 munlock_vma_folio(folio, vma);
1604}
1605
1606/**
1607 * folio_remove_rmap_ptes - remove PTE mappings from a page range of a folio
1608 * @folio: The folio to remove the mappings from
1609 * @page: The first page to remove
1610 * @nr_pages: The number of pages that will be removed from the mapping
1611 * @vma: The vm area from which the mappings are removed
1612 *
1613 * The page range of the folio is defined by [page, page + nr_pages)
1614 *
1615 * The caller needs to hold the page table lock.
1616 */
1617void folio_remove_rmap_ptes(struct folio *folio, struct page *page,
1618 int nr_pages, struct vm_area_struct *vma)
1619{
1620 __folio_remove_rmap(folio, page, nr_pages, vma, RMAP_LEVEL_PTE);
1621}
1622
1623/**
1624 * folio_remove_rmap_pmd - remove a PMD mapping from a page range of a folio
1625 * @folio: The folio to remove the mapping from
1626 * @page: The first page to remove
1627 * @vma: The vm area from which the mapping is removed
1628 *
1629 * The page range of the folio is defined by [page, page + HPAGE_PMD_NR)
1630 *
1631 * The caller needs to hold the page table lock.
1632 */
1633void folio_remove_rmap_pmd(struct folio *folio, struct page *page,
1634 struct vm_area_struct *vma)
1635{
1636#ifdef CONFIG_TRANSPARENT_HUGEPAGE
1637 __folio_remove_rmap(folio, page, HPAGE_PMD_NR, vma, RMAP_LEVEL_PMD);
1638#else
1639 WARN_ON_ONCE(true);
1640#endif
1641}
1642
1643/*
1644 * @arg: enum ttu_flags will be passed to this argument
1645 */
1646static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
1647 unsigned long address, void *arg)
1648{
1649 struct mm_struct *mm = vma->vm_mm;
1650 DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
1651 pte_t pteval;
1652 struct page *subpage;
1653 bool anon_exclusive, ret = true;
1654 struct mmu_notifier_range range;
1655 enum ttu_flags flags = (enum ttu_flags)(long)arg;
1656 unsigned long pfn;
1657 unsigned long hsz = 0;
1658
1659 /*
1660 * When racing against e.g. zap_pte_range() on another cpu,
1661 * in between its ptep_get_and_clear_full() and folio_remove_rmap_*(),
1662 * try_to_unmap() may return before page_mapped() has become false,
1663 * if page table locking is skipped: use TTU_SYNC to wait for that.
1664 */
1665 if (flags & TTU_SYNC)
1666 pvmw.flags = PVMW_SYNC;
1667
1668 /*
1669 * For THP, we have to assume the worse case ie pmd for invalidation.
1670 * For hugetlb, it could be much worse if we need to do pud
1671 * invalidation in the case of pmd sharing.
1672 *
1673 * Note that the folio can not be freed in this function as call of
1674 * try_to_unmap() must hold a reference on the folio.
1675 */
1676 range.end = vma_address_end(&pvmw);
1677 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
1678 address, range.end);
1679 if (folio_test_hugetlb(folio)) {
1680 /*
1681 * If sharing is possible, start and end will be adjusted
1682 * accordingly.
1683 */
1684 adjust_range_if_pmd_sharing_possible(vma, &range.start,
1685 &range.end);
1686
1687 /* We need the huge page size for set_huge_pte_at() */
1688 hsz = huge_page_size(hstate_vma(vma));
1689 }
1690 mmu_notifier_invalidate_range_start(&range);
1691
1692 while (page_vma_mapped_walk(&pvmw)) {
1693 /*
1694 * If the folio is in an mlock()d vma, we must not swap it out.
1695 */
1696 if (!(flags & TTU_IGNORE_MLOCK) &&
1697 (vma->vm_flags & VM_LOCKED)) {
1698 /* Restore the mlock which got missed */
1699 if (!folio_test_large(folio))
1700 mlock_vma_folio(folio, vma);
1701 goto walk_abort;
1702 }
1703
1704 if (!pvmw.pte) {
1705 if (unmap_huge_pmd_locked(vma, pvmw.address, pvmw.pmd,
1706 folio))
1707 goto walk_done;
1708
1709 if (flags & TTU_SPLIT_HUGE_PMD) {
1710 /*
1711 * We temporarily have to drop the PTL and
1712 * restart so we can process the PTE-mapped THP.
1713 */
1714 split_huge_pmd_locked(vma, pvmw.address,
1715 pvmw.pmd, false, folio);
1716 flags &= ~TTU_SPLIT_HUGE_PMD;
1717 page_vma_mapped_walk_restart(&pvmw);
1718 continue;
1719 }
1720 }
1721
1722 /* Unexpected PMD-mapped THP? */
1723 VM_BUG_ON_FOLIO(!pvmw.pte, folio);
1724
1725 pfn = pte_pfn(ptep_get(pvmw.pte));
1726 subpage = folio_page(folio, pfn - folio_pfn(folio));
1727 address = pvmw.address;
1728 anon_exclusive = folio_test_anon(folio) &&
1729 PageAnonExclusive(subpage);
1730
1731 if (folio_test_hugetlb(folio)) {
1732 bool anon = folio_test_anon(folio);
1733
1734 /*
1735 * The try_to_unmap() is only passed a hugetlb page
1736 * in the case where the hugetlb page is poisoned.
1737 */
1738 VM_BUG_ON_PAGE(!PageHWPoison(subpage), subpage);
1739 /*
1740 * huge_pmd_unshare may unmap an entire PMD page.
1741 * There is no way of knowing exactly which PMDs may
1742 * be cached for this mm, so we must flush them all.
1743 * start/end were already adjusted above to cover this
1744 * range.
1745 */
1746 flush_cache_range(vma, range.start, range.end);
1747
1748 /*
1749 * To call huge_pmd_unshare, i_mmap_rwsem must be
1750 * held in write mode. Caller needs to explicitly
1751 * do this outside rmap routines.
1752 *
1753 * We also must hold hugetlb vma_lock in write mode.
1754 * Lock order dictates acquiring vma_lock BEFORE
1755 * i_mmap_rwsem. We can only try lock here and fail
1756 * if unsuccessful.
1757 */
1758 if (!anon) {
1759 VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
1760 if (!hugetlb_vma_trylock_write(vma))
1761 goto walk_abort;
1762 if (huge_pmd_unshare(mm, vma, address, pvmw.pte)) {
1763 hugetlb_vma_unlock_write(vma);
1764 flush_tlb_range(vma,
1765 range.start, range.end);
1766 /*
1767 * The ref count of the PMD page was
1768 * dropped which is part of the way map
1769 * counting is done for shared PMDs.
1770 * Return 'true' here. When there is
1771 * no other sharing, huge_pmd_unshare
1772 * returns false and we will unmap the
1773 * actual page and drop map count
1774 * to zero.
1775 */
1776 goto walk_done;
1777 }
1778 hugetlb_vma_unlock_write(vma);
1779 }
1780 pteval = huge_ptep_clear_flush(vma, address, pvmw.pte);
1781 } else {
1782 flush_cache_page(vma, address, pfn);
1783 /* Nuke the page table entry. */
1784 if (should_defer_flush(mm, flags)) {
1785 /*
1786 * We clear the PTE but do not flush so potentially
1787 * a remote CPU could still be writing to the folio.
1788 * If the entry was previously clean then the
1789 * architecture must guarantee that a clear->dirty
1790 * transition on a cached TLB entry is written through
1791 * and traps if the PTE is unmapped.
1792 */
1793 pteval = ptep_get_and_clear(mm, address, pvmw.pte);
1794
1795 set_tlb_ubc_flush_pending(mm, pteval, address);
1796 } else {
1797 pteval = ptep_clear_flush(vma, address, pvmw.pte);
1798 }
1799 }
1800
1801 /*
1802 * Now the pte is cleared. If this pte was uffd-wp armed,
1803 * we may want to replace a none pte with a marker pte if
1804 * it's file-backed, so we don't lose the tracking info.
1805 */
1806 pte_install_uffd_wp_if_needed(vma, address, pvmw.pte, pteval);
1807
1808 /* Set the dirty flag on the folio now the pte is gone. */
1809 if (pte_dirty(pteval))
1810 folio_mark_dirty(folio);
1811
1812 /* Update high watermark before we lower rss */
1813 update_hiwater_rss(mm);
1814
1815 if (PageHWPoison(subpage) && (flags & TTU_HWPOISON)) {
1816 pteval = swp_entry_to_pte(make_hwpoison_entry(subpage));
1817 if (folio_test_hugetlb(folio)) {
1818 hugetlb_count_sub(folio_nr_pages(folio), mm);
1819 set_huge_pte_at(mm, address, pvmw.pte, pteval,
1820 hsz);
1821 } else {
1822 dec_mm_counter(mm, mm_counter(folio));
1823 set_pte_at(mm, address, pvmw.pte, pteval);
1824 }
1825
1826 } else if (pte_unused(pteval) && !userfaultfd_armed(vma)) {
1827 /*
1828 * The guest indicated that the page content is of no
1829 * interest anymore. Simply discard the pte, vmscan
1830 * will take care of the rest.
1831 * A future reference will then fault in a new zero
1832 * page. When userfaultfd is active, we must not drop
1833 * this page though, as its main user (postcopy
1834 * migration) will not expect userfaults on already
1835 * copied pages.
1836 */
1837 dec_mm_counter(mm, mm_counter(folio));
1838 } else if (folio_test_anon(folio)) {
1839 swp_entry_t entry = page_swap_entry(subpage);
1840 pte_t swp_pte;
1841 /*
1842 * Store the swap location in the pte.
1843 * See handle_pte_fault() ...
1844 */
1845 if (unlikely(folio_test_swapbacked(folio) !=
1846 folio_test_swapcache(folio))) {
1847 WARN_ON_ONCE(1);
1848 goto walk_abort;
1849 }
1850
1851 /* MADV_FREE page check */
1852 if (!folio_test_swapbacked(folio)) {
1853 int ref_count, map_count;
1854
1855 /*
1856 * Synchronize with gup_pte_range():
1857 * - clear PTE; barrier; read refcount
1858 * - inc refcount; barrier; read PTE
1859 */
1860 smp_mb();
1861
1862 ref_count = folio_ref_count(folio);
1863 map_count = folio_mapcount(folio);
1864
1865 /*
1866 * Order reads for page refcount and dirty flag
1867 * (see comments in __remove_mapping()).
1868 */
1869 smp_rmb();
1870
1871 /*
1872 * The only page refs must be one from isolation
1873 * plus the rmap(s) (dropped by discard:).
1874 */
1875 if (ref_count == 1 + map_count &&
1876 (!folio_test_dirty(folio) ||
1877 /*
1878 * Unlike MADV_FREE mappings, VM_DROPPABLE
1879 * ones can be dropped even if they've
1880 * been dirtied.
1881 */
1882 (vma->vm_flags & VM_DROPPABLE))) {
1883 dec_mm_counter(mm, MM_ANONPAGES);
1884 goto discard;
1885 }
1886
1887 /*
1888 * If the folio was redirtied, it cannot be
1889 * discarded. Remap the page to page table.
1890 */
1891 set_pte_at(mm, address, pvmw.pte, pteval);
1892 /*
1893 * Unlike MADV_FREE mappings, VM_DROPPABLE ones
1894 * never get swap backed on failure to drop.
1895 */
1896 if (!(vma->vm_flags & VM_DROPPABLE))
1897 folio_set_swapbacked(folio);
1898 goto walk_abort;
1899 }
1900
1901 if (swap_duplicate(entry) < 0) {
1902 set_pte_at(mm, address, pvmw.pte, pteval);
1903 goto walk_abort;
1904 }
1905 if (arch_unmap_one(mm, vma, address, pteval) < 0) {
1906 swap_free(entry);
1907 set_pte_at(mm, address, pvmw.pte, pteval);
1908 goto walk_abort;
1909 }
1910
1911 /* See folio_try_share_anon_rmap(): clear PTE first. */
1912 if (anon_exclusive &&
1913 folio_try_share_anon_rmap_pte(folio, subpage)) {
1914 swap_free(entry);
1915 set_pte_at(mm, address, pvmw.pte, pteval);
1916 goto walk_abort;
1917 }
1918 if (list_empty(&mm->mmlist)) {
1919 spin_lock(&mmlist_lock);
1920 if (list_empty(&mm->mmlist))
1921 list_add(&mm->mmlist, &init_mm.mmlist);
1922 spin_unlock(&mmlist_lock);
1923 }
1924 dec_mm_counter(mm, MM_ANONPAGES);
1925 inc_mm_counter(mm, MM_SWAPENTS);
1926 swp_pte = swp_entry_to_pte(entry);
1927 if (anon_exclusive)
1928 swp_pte = pte_swp_mkexclusive(swp_pte);
1929 if (pte_soft_dirty(pteval))
1930 swp_pte = pte_swp_mksoft_dirty(swp_pte);
1931 if (pte_uffd_wp(pteval))
1932 swp_pte = pte_swp_mkuffd_wp(swp_pte);
1933 set_pte_at(mm, address, pvmw.pte, swp_pte);
1934 } else {
1935 /*
1936 * This is a locked file-backed folio,
1937 * so it cannot be removed from the page
1938 * cache and replaced by a new folio before
1939 * mmu_notifier_invalidate_range_end, so no
1940 * concurrent thread might update its page table
1941 * to point at a new folio while a device is
1942 * still using this folio.
1943 *
1944 * See Documentation/mm/mmu_notifier.rst
1945 */
1946 dec_mm_counter(mm, mm_counter_file(folio));
1947 }
1948discard:
1949 if (unlikely(folio_test_hugetlb(folio)))
1950 hugetlb_remove_rmap(folio);
1951 else
1952 folio_remove_rmap_pte(folio, subpage, vma);
1953 if (vma->vm_flags & VM_LOCKED)
1954 mlock_drain_local();
1955 folio_put(folio);
1956 continue;
1957walk_abort:
1958 ret = false;
1959walk_done:
1960 page_vma_mapped_walk_done(&pvmw);
1961 break;
1962 }
1963
1964 mmu_notifier_invalidate_range_end(&range);
1965
1966 return ret;
1967}
1968
1969static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg)
1970{
1971 return vma_is_temporary_stack(vma);
1972}
1973
1974static int folio_not_mapped(struct folio *folio)
1975{
1976 return !folio_mapped(folio);
1977}
1978
1979/**
1980 * try_to_unmap - Try to remove all page table mappings to a folio.
1981 * @folio: The folio to unmap.
1982 * @flags: action and flags
1983 *
1984 * Tries to remove all the page table entries which are mapping this
1985 * folio. It is the caller's responsibility to check if the folio is
1986 * still mapped if needed (use TTU_SYNC to prevent accounting races).
1987 *
1988 * Context: Caller must hold the folio lock.
1989 */
1990void try_to_unmap(struct folio *folio, enum ttu_flags flags)
1991{
1992 struct rmap_walk_control rwc = {
1993 .rmap_one = try_to_unmap_one,
1994 .arg = (void *)flags,
1995 .done = folio_not_mapped,
1996 .anon_lock = folio_lock_anon_vma_read,
1997 };
1998
1999 if (flags & TTU_RMAP_LOCKED)
2000 rmap_walk_locked(folio, &rwc);
2001 else
2002 rmap_walk(folio, &rwc);
2003}
2004
2005/*
2006 * @arg: enum ttu_flags will be passed to this argument.
2007 *
2008 * If TTU_SPLIT_HUGE_PMD is specified any PMD mappings will be split into PTEs
2009 * containing migration entries.
2010 */
2011static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
2012 unsigned long address, void *arg)
2013{
2014 struct mm_struct *mm = vma->vm_mm;
2015 DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
2016 pte_t pteval;
2017 struct page *subpage;
2018 bool anon_exclusive, ret = true;
2019 struct mmu_notifier_range range;
2020 enum ttu_flags flags = (enum ttu_flags)(long)arg;
2021 unsigned long pfn;
2022 unsigned long hsz = 0;
2023
2024 /*
2025 * When racing against e.g. zap_pte_range() on another cpu,
2026 * in between its ptep_get_and_clear_full() and folio_remove_rmap_*(),
2027 * try_to_migrate() may return before page_mapped() has become false,
2028 * if page table locking is skipped: use TTU_SYNC to wait for that.
2029 */
2030 if (flags & TTU_SYNC)
2031 pvmw.flags = PVMW_SYNC;
2032
2033 /*
2034 * unmap_page() in mm/huge_memory.c is the only user of migration with
2035 * TTU_SPLIT_HUGE_PMD and it wants to freeze.
2036 */
2037 if (flags & TTU_SPLIT_HUGE_PMD)
2038 split_huge_pmd_address(vma, address, true, folio);
2039
2040 /*
2041 * For THP, we have to assume the worse case ie pmd for invalidation.
2042 * For hugetlb, it could be much worse if we need to do pud
2043 * invalidation in the case of pmd sharing.
2044 *
2045 * Note that the page can not be free in this function as call of
2046 * try_to_unmap() must hold a reference on the page.
2047 */
2048 range.end = vma_address_end(&pvmw);
2049 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
2050 address, range.end);
2051 if (folio_test_hugetlb(folio)) {
2052 /*
2053 * If sharing is possible, start and end will be adjusted
2054 * accordingly.
2055 */
2056 adjust_range_if_pmd_sharing_possible(vma, &range.start,
2057 &range.end);
2058
2059 /* We need the huge page size for set_huge_pte_at() */
2060 hsz = huge_page_size(hstate_vma(vma));
2061 }
2062 mmu_notifier_invalidate_range_start(&range);
2063
2064 while (page_vma_mapped_walk(&pvmw)) {
2065#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2066 /* PMD-mapped THP migration entry */
2067 if (!pvmw.pte) {
2068 subpage = folio_page(folio,
2069 pmd_pfn(*pvmw.pmd) - folio_pfn(folio));
2070 VM_BUG_ON_FOLIO(folio_test_hugetlb(folio) ||
2071 !folio_test_pmd_mappable(folio), folio);
2072
2073 if (set_pmd_migration_entry(&pvmw, subpage)) {
2074 ret = false;
2075 page_vma_mapped_walk_done(&pvmw);
2076 break;
2077 }
2078 continue;
2079 }
2080#endif
2081
2082 /* Unexpected PMD-mapped THP? */
2083 VM_BUG_ON_FOLIO(!pvmw.pte, folio);
2084
2085 pfn = pte_pfn(ptep_get(pvmw.pte));
2086
2087 if (folio_is_zone_device(folio)) {
2088 /*
2089 * Our PTE is a non-present device exclusive entry and
2090 * calculating the subpage as for the common case would
2091 * result in an invalid pointer.
2092 *
2093 * Since only PAGE_SIZE pages can currently be
2094 * migrated, just set it to page. This will need to be
2095 * changed when hugepage migrations to device private
2096 * memory are supported.
2097 */
2098 VM_BUG_ON_FOLIO(folio_nr_pages(folio) > 1, folio);
2099 subpage = &folio->page;
2100 } else {
2101 subpage = folio_page(folio, pfn - folio_pfn(folio));
2102 }
2103 address = pvmw.address;
2104 anon_exclusive = folio_test_anon(folio) &&
2105 PageAnonExclusive(subpage);
2106
2107 if (folio_test_hugetlb(folio)) {
2108 bool anon = folio_test_anon(folio);
2109
2110 /*
2111 * huge_pmd_unshare may unmap an entire PMD page.
2112 * There is no way of knowing exactly which PMDs may
2113 * be cached for this mm, so we must flush them all.
2114 * start/end were already adjusted above to cover this
2115 * range.
2116 */
2117 flush_cache_range(vma, range.start, range.end);
2118
2119 /*
2120 * To call huge_pmd_unshare, i_mmap_rwsem must be
2121 * held in write mode. Caller needs to explicitly
2122 * do this outside rmap routines.
2123 *
2124 * We also must hold hugetlb vma_lock in write mode.
2125 * Lock order dictates acquiring vma_lock BEFORE
2126 * i_mmap_rwsem. We can only try lock here and
2127 * fail if unsuccessful.
2128 */
2129 if (!anon) {
2130 VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
2131 if (!hugetlb_vma_trylock_write(vma)) {
2132 page_vma_mapped_walk_done(&pvmw);
2133 ret = false;
2134 break;
2135 }
2136 if (huge_pmd_unshare(mm, vma, address, pvmw.pte)) {
2137 hugetlb_vma_unlock_write(vma);
2138 flush_tlb_range(vma,
2139 range.start, range.end);
2140
2141 /*
2142 * The ref count of the PMD page was
2143 * dropped which is part of the way map
2144 * counting is done for shared PMDs.
2145 * Return 'true' here. When there is
2146 * no other sharing, huge_pmd_unshare
2147 * returns false and we will unmap the
2148 * actual page and drop map count
2149 * to zero.
2150 */
2151 page_vma_mapped_walk_done(&pvmw);
2152 break;
2153 }
2154 hugetlb_vma_unlock_write(vma);
2155 }
2156 /* Nuke the hugetlb page table entry */
2157 pteval = huge_ptep_clear_flush(vma, address, pvmw.pte);
2158 } else {
2159 flush_cache_page(vma, address, pfn);
2160 /* Nuke the page table entry. */
2161 if (should_defer_flush(mm, flags)) {
2162 /*
2163 * We clear the PTE but do not flush so potentially
2164 * a remote CPU could still be writing to the folio.
2165 * If the entry was previously clean then the
2166 * architecture must guarantee that a clear->dirty
2167 * transition on a cached TLB entry is written through
2168 * and traps if the PTE is unmapped.
2169 */
2170 pteval = ptep_get_and_clear(mm, address, pvmw.pte);
2171
2172 set_tlb_ubc_flush_pending(mm, pteval, address);
2173 } else {
2174 pteval = ptep_clear_flush(vma, address, pvmw.pte);
2175 }
2176 }
2177
2178 /* Set the dirty flag on the folio now the pte is gone. */
2179 if (pte_dirty(pteval))
2180 folio_mark_dirty(folio);
2181
2182 /* Update high watermark before we lower rss */
2183 update_hiwater_rss(mm);
2184
2185 if (folio_is_device_private(folio)) {
2186 unsigned long pfn = folio_pfn(folio);
2187 swp_entry_t entry;
2188 pte_t swp_pte;
2189
2190 if (anon_exclusive)
2191 WARN_ON_ONCE(folio_try_share_anon_rmap_pte(folio,
2192 subpage));
2193
2194 /*
2195 * Store the pfn of the page in a special migration
2196 * pte. do_swap_page() will wait until the migration
2197 * pte is removed and then restart fault handling.
2198 */
2199 entry = pte_to_swp_entry(pteval);
2200 if (is_writable_device_private_entry(entry))
2201 entry = make_writable_migration_entry(pfn);
2202 else if (anon_exclusive)
2203 entry = make_readable_exclusive_migration_entry(pfn);
2204 else
2205 entry = make_readable_migration_entry(pfn);
2206 swp_pte = swp_entry_to_pte(entry);
2207
2208 /*
2209 * pteval maps a zone device page and is therefore
2210 * a swap pte.
2211 */
2212 if (pte_swp_soft_dirty(pteval))
2213 swp_pte = pte_swp_mksoft_dirty(swp_pte);
2214 if (pte_swp_uffd_wp(pteval))
2215 swp_pte = pte_swp_mkuffd_wp(swp_pte);
2216 set_pte_at(mm, pvmw.address, pvmw.pte, swp_pte);
2217 trace_set_migration_pte(pvmw.address, pte_val(swp_pte),
2218 folio_order(folio));
2219 /*
2220 * No need to invalidate here it will synchronize on
2221 * against the special swap migration pte.
2222 */
2223 } else if (PageHWPoison(subpage)) {
2224 pteval = swp_entry_to_pte(make_hwpoison_entry(subpage));
2225 if (folio_test_hugetlb(folio)) {
2226 hugetlb_count_sub(folio_nr_pages(folio), mm);
2227 set_huge_pte_at(mm, address, pvmw.pte, pteval,
2228 hsz);
2229 } else {
2230 dec_mm_counter(mm, mm_counter(folio));
2231 set_pte_at(mm, address, pvmw.pte, pteval);
2232 }
2233
2234 } else if (pte_unused(pteval) && !userfaultfd_armed(vma)) {
2235 /*
2236 * The guest indicated that the page content is of no
2237 * interest anymore. Simply discard the pte, vmscan
2238 * will take care of the rest.
2239 * A future reference will then fault in a new zero
2240 * page. When userfaultfd is active, we must not drop
2241 * this page though, as its main user (postcopy
2242 * migration) will not expect userfaults on already
2243 * copied pages.
2244 */
2245 dec_mm_counter(mm, mm_counter(folio));
2246 } else {
2247 swp_entry_t entry;
2248 pte_t swp_pte;
2249
2250 if (arch_unmap_one(mm, vma, address, pteval) < 0) {
2251 if (folio_test_hugetlb(folio))
2252 set_huge_pte_at(mm, address, pvmw.pte,
2253 pteval, hsz);
2254 else
2255 set_pte_at(mm, address, pvmw.pte, pteval);
2256 ret = false;
2257 page_vma_mapped_walk_done(&pvmw);
2258 break;
2259 }
2260 VM_BUG_ON_PAGE(pte_write(pteval) && folio_test_anon(folio) &&
2261 !anon_exclusive, subpage);
2262
2263 /* See folio_try_share_anon_rmap_pte(): clear PTE first. */
2264 if (folio_test_hugetlb(folio)) {
2265 if (anon_exclusive &&
2266 hugetlb_try_share_anon_rmap(folio)) {
2267 set_huge_pte_at(mm, address, pvmw.pte,
2268 pteval, hsz);
2269 ret = false;
2270 page_vma_mapped_walk_done(&pvmw);
2271 break;
2272 }
2273 } else if (anon_exclusive &&
2274 folio_try_share_anon_rmap_pte(folio, subpage)) {
2275 set_pte_at(mm, address, pvmw.pte, pteval);
2276 ret = false;
2277 page_vma_mapped_walk_done(&pvmw);
2278 break;
2279 }
2280
2281 /*
2282 * Store the pfn of the page in a special migration
2283 * pte. do_swap_page() will wait until the migration
2284 * pte is removed and then restart fault handling.
2285 */
2286 if (pte_write(pteval))
2287 entry = make_writable_migration_entry(
2288 page_to_pfn(subpage));
2289 else if (anon_exclusive)
2290 entry = make_readable_exclusive_migration_entry(
2291 page_to_pfn(subpage));
2292 else
2293 entry = make_readable_migration_entry(
2294 page_to_pfn(subpage));
2295 if (pte_young(pteval))
2296 entry = make_migration_entry_young(entry);
2297 if (pte_dirty(pteval))
2298 entry = make_migration_entry_dirty(entry);
2299 swp_pte = swp_entry_to_pte(entry);
2300 if (pte_soft_dirty(pteval))
2301 swp_pte = pte_swp_mksoft_dirty(swp_pte);
2302 if (pte_uffd_wp(pteval))
2303 swp_pte = pte_swp_mkuffd_wp(swp_pte);
2304 if (folio_test_hugetlb(folio))
2305 set_huge_pte_at(mm, address, pvmw.pte, swp_pte,
2306 hsz);
2307 else
2308 set_pte_at(mm, address, pvmw.pte, swp_pte);
2309 trace_set_migration_pte(address, pte_val(swp_pte),
2310 folio_order(folio));
2311 /*
2312 * No need to invalidate here it will synchronize on
2313 * against the special swap migration pte.
2314 */
2315 }
2316
2317 if (unlikely(folio_test_hugetlb(folio)))
2318 hugetlb_remove_rmap(folio);
2319 else
2320 folio_remove_rmap_pte(folio, subpage, vma);
2321 if (vma->vm_flags & VM_LOCKED)
2322 mlock_drain_local();
2323 folio_put(folio);
2324 }
2325
2326 mmu_notifier_invalidate_range_end(&range);
2327
2328 return ret;
2329}
2330
2331/**
2332 * try_to_migrate - try to replace all page table mappings with swap entries
2333 * @folio: the folio to replace page table entries for
2334 * @flags: action and flags
2335 *
2336 * Tries to remove all the page table entries which are mapping this folio and
2337 * replace them with special swap entries. Caller must hold the folio lock.
2338 */
2339void try_to_migrate(struct folio *folio, enum ttu_flags flags)
2340{
2341 struct rmap_walk_control rwc = {
2342 .rmap_one = try_to_migrate_one,
2343 .arg = (void *)flags,
2344 .done = folio_not_mapped,
2345 .anon_lock = folio_lock_anon_vma_read,
2346 };
2347
2348 /*
2349 * Migration always ignores mlock and only supports TTU_RMAP_LOCKED and
2350 * TTU_SPLIT_HUGE_PMD, TTU_SYNC, and TTU_BATCH_FLUSH flags.
2351 */
2352 if (WARN_ON_ONCE(flags & ~(TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD |
2353 TTU_SYNC | TTU_BATCH_FLUSH)))
2354 return;
2355
2356 if (folio_is_zone_device(folio) &&
2357 (!folio_is_device_private(folio) && !folio_is_device_coherent(folio)))
2358 return;
2359
2360 /*
2361 * During exec, a temporary VMA is setup and later moved.
2362 * The VMA is moved under the anon_vma lock but not the
2363 * page tables leading to a race where migration cannot
2364 * find the migration ptes. Rather than increasing the
2365 * locking requirements of exec(), migration skips
2366 * temporary VMAs until after exec() completes.
2367 */
2368 if (!folio_test_ksm(folio) && folio_test_anon(folio))
2369 rwc.invalid_vma = invalid_migration_vma;
2370
2371 if (flags & TTU_RMAP_LOCKED)
2372 rmap_walk_locked(folio, &rwc);
2373 else
2374 rmap_walk(folio, &rwc);
2375}
2376
2377#ifdef CONFIG_DEVICE_PRIVATE
2378struct make_exclusive_args {
2379 struct mm_struct *mm;
2380 unsigned long address;
2381 void *owner;
2382 bool valid;
2383};
2384
2385static bool page_make_device_exclusive_one(struct folio *folio,
2386 struct vm_area_struct *vma, unsigned long address, void *priv)
2387{
2388 struct mm_struct *mm = vma->vm_mm;
2389 DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
2390 struct make_exclusive_args *args = priv;
2391 pte_t pteval;
2392 struct page *subpage;
2393 bool ret = true;
2394 struct mmu_notifier_range range;
2395 swp_entry_t entry;
2396 pte_t swp_pte;
2397 pte_t ptent;
2398
2399 mmu_notifier_range_init_owner(&range, MMU_NOTIFY_EXCLUSIVE, 0,
2400 vma->vm_mm, address, min(vma->vm_end,
2401 address + folio_size(folio)),
2402 args->owner);
2403 mmu_notifier_invalidate_range_start(&range);
2404
2405 while (page_vma_mapped_walk(&pvmw)) {
2406 /* Unexpected PMD-mapped THP? */
2407 VM_BUG_ON_FOLIO(!pvmw.pte, folio);
2408
2409 ptent = ptep_get(pvmw.pte);
2410 if (!pte_present(ptent)) {
2411 ret = false;
2412 page_vma_mapped_walk_done(&pvmw);
2413 break;
2414 }
2415
2416 subpage = folio_page(folio,
2417 pte_pfn(ptent) - folio_pfn(folio));
2418 address = pvmw.address;
2419
2420 /* Nuke the page table entry. */
2421 flush_cache_page(vma, address, pte_pfn(ptent));
2422 pteval = ptep_clear_flush(vma, address, pvmw.pte);
2423
2424 /* Set the dirty flag on the folio now the pte is gone. */
2425 if (pte_dirty(pteval))
2426 folio_mark_dirty(folio);
2427
2428 /*
2429 * Check that our target page is still mapped at the expected
2430 * address.
2431 */
2432 if (args->mm == mm && args->address == address &&
2433 pte_write(pteval))
2434 args->valid = true;
2435
2436 /*
2437 * Store the pfn of the page in a special migration
2438 * pte. do_swap_page() will wait until the migration
2439 * pte is removed and then restart fault handling.
2440 */
2441 if (pte_write(pteval))
2442 entry = make_writable_device_exclusive_entry(
2443 page_to_pfn(subpage));
2444 else
2445 entry = make_readable_device_exclusive_entry(
2446 page_to_pfn(subpage));
2447 swp_pte = swp_entry_to_pte(entry);
2448 if (pte_soft_dirty(pteval))
2449 swp_pte = pte_swp_mksoft_dirty(swp_pte);
2450 if (pte_uffd_wp(pteval))
2451 swp_pte = pte_swp_mkuffd_wp(swp_pte);
2452
2453 set_pte_at(mm, address, pvmw.pte, swp_pte);
2454
2455 /*
2456 * There is a reference on the page for the swap entry which has
2457 * been removed, so shouldn't take another.
2458 */
2459 folio_remove_rmap_pte(folio, subpage, vma);
2460 }
2461
2462 mmu_notifier_invalidate_range_end(&range);
2463
2464 return ret;
2465}
2466
2467/**
2468 * folio_make_device_exclusive - Mark the folio exclusively owned by a device.
2469 * @folio: The folio to replace page table entries for.
2470 * @mm: The mm_struct where the folio is expected to be mapped.
2471 * @address: Address where the folio is expected to be mapped.
2472 * @owner: passed to MMU_NOTIFY_EXCLUSIVE range notifier callbacks
2473 *
2474 * Tries to remove all the page table entries which are mapping this
2475 * folio and replace them with special device exclusive swap entries to
2476 * grant a device exclusive access to the folio.
2477 *
2478 * Context: Caller must hold the folio lock.
2479 * Return: false if the page is still mapped, or if it could not be unmapped
2480 * from the expected address. Otherwise returns true (success).
2481 */
2482static bool folio_make_device_exclusive(struct folio *folio,
2483 struct mm_struct *mm, unsigned long address, void *owner)
2484{
2485 struct make_exclusive_args args = {
2486 .mm = mm,
2487 .address = address,
2488 .owner = owner,
2489 .valid = false,
2490 };
2491 struct rmap_walk_control rwc = {
2492 .rmap_one = page_make_device_exclusive_one,
2493 .done = folio_not_mapped,
2494 .anon_lock = folio_lock_anon_vma_read,
2495 .arg = &args,
2496 };
2497
2498 /*
2499 * Restrict to anonymous folios for now to avoid potential writeback
2500 * issues.
2501 */
2502 if (!folio_test_anon(folio))
2503 return false;
2504
2505 rmap_walk(folio, &rwc);
2506
2507 return args.valid && !folio_mapcount(folio);
2508}
2509
2510/**
2511 * make_device_exclusive_range() - Mark a range for exclusive use by a device
2512 * @mm: mm_struct of associated target process
2513 * @start: start of the region to mark for exclusive device access
2514 * @end: end address of region
2515 * @pages: returns the pages which were successfully marked for exclusive access
2516 * @owner: passed to MMU_NOTIFY_EXCLUSIVE range notifier to allow filtering
2517 *
2518 * Returns: number of pages found in the range by GUP. A page is marked for
2519 * exclusive access only if the page pointer is non-NULL.
2520 *
2521 * This function finds ptes mapping page(s) to the given address range, locks
2522 * them and replaces mappings with special swap entries preventing userspace CPU
2523 * access. On fault these entries are replaced with the original mapping after
2524 * calling MMU notifiers.
2525 *
2526 * A driver using this to program access from a device must use a mmu notifier
2527 * critical section to hold a device specific lock during programming. Once
2528 * programming is complete it should drop the page lock and reference after
2529 * which point CPU access to the page will revoke the exclusive access.
2530 */
2531int make_device_exclusive_range(struct mm_struct *mm, unsigned long start,
2532 unsigned long end, struct page **pages,
2533 void *owner)
2534{
2535 long npages = (end - start) >> PAGE_SHIFT;
2536 long i;
2537
2538 npages = get_user_pages_remote(mm, start, npages,
2539 FOLL_GET | FOLL_WRITE | FOLL_SPLIT_PMD,
2540 pages, NULL);
2541 if (npages < 0)
2542 return npages;
2543
2544 for (i = 0; i < npages; i++, start += PAGE_SIZE) {
2545 struct folio *folio = page_folio(pages[i]);
2546 if (PageTail(pages[i]) || !folio_trylock(folio)) {
2547 folio_put(folio);
2548 pages[i] = NULL;
2549 continue;
2550 }
2551
2552 if (!folio_make_device_exclusive(folio, mm, start, owner)) {
2553 folio_unlock(folio);
2554 folio_put(folio);
2555 pages[i] = NULL;
2556 }
2557 }
2558
2559 return npages;
2560}
2561EXPORT_SYMBOL_GPL(make_device_exclusive_range);
2562#endif
2563
2564void __put_anon_vma(struct anon_vma *anon_vma)
2565{
2566 struct anon_vma *root = anon_vma->root;
2567
2568 anon_vma_free(anon_vma);
2569 if (root != anon_vma && atomic_dec_and_test(&root->refcount))
2570 anon_vma_free(root);
2571}
2572
2573static struct anon_vma *rmap_walk_anon_lock(const struct folio *folio,
2574 struct rmap_walk_control *rwc)
2575{
2576 struct anon_vma *anon_vma;
2577
2578 if (rwc->anon_lock)
2579 return rwc->anon_lock(folio, rwc);
2580
2581 /*
2582 * Note: remove_migration_ptes() cannot use folio_lock_anon_vma_read()
2583 * because that depends on page_mapped(); but not all its usages
2584 * are holding mmap_lock. Users without mmap_lock are required to
2585 * take a reference count to prevent the anon_vma disappearing
2586 */
2587 anon_vma = folio_anon_vma(folio);
2588 if (!anon_vma)
2589 return NULL;
2590
2591 if (anon_vma_trylock_read(anon_vma))
2592 goto out;
2593
2594 if (rwc->try_lock) {
2595 anon_vma = NULL;
2596 rwc->contended = true;
2597 goto out;
2598 }
2599
2600 anon_vma_lock_read(anon_vma);
2601out:
2602 return anon_vma;
2603}
2604
2605/*
2606 * rmap_walk_anon - do something to anonymous page using the object-based
2607 * rmap method
2608 * @folio: the folio to be handled
2609 * @rwc: control variable according to each walk type
2610 * @locked: caller holds relevant rmap lock
2611 *
2612 * Find all the mappings of a folio using the mapping pointer and the vma
2613 * chains contained in the anon_vma struct it points to.
2614 */
2615static void rmap_walk_anon(struct folio *folio,
2616 struct rmap_walk_control *rwc, bool locked)
2617{
2618 struct anon_vma *anon_vma;
2619 pgoff_t pgoff_start, pgoff_end;
2620 struct anon_vma_chain *avc;
2621
2622 if (locked) {
2623 anon_vma = folio_anon_vma(folio);
2624 /* anon_vma disappear under us? */
2625 VM_BUG_ON_FOLIO(!anon_vma, folio);
2626 } else {
2627 anon_vma = rmap_walk_anon_lock(folio, rwc);
2628 }
2629 if (!anon_vma)
2630 return;
2631
2632 pgoff_start = folio_pgoff(folio);
2633 pgoff_end = pgoff_start + folio_nr_pages(folio) - 1;
2634 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root,
2635 pgoff_start, pgoff_end) {
2636 struct vm_area_struct *vma = avc->vma;
2637 unsigned long address = vma_address(vma, pgoff_start,
2638 folio_nr_pages(folio));
2639
2640 VM_BUG_ON_VMA(address == -EFAULT, vma);
2641 cond_resched();
2642
2643 if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
2644 continue;
2645
2646 if (!rwc->rmap_one(folio, vma, address, rwc->arg))
2647 break;
2648 if (rwc->done && rwc->done(folio))
2649 break;
2650 }
2651
2652 if (!locked)
2653 anon_vma_unlock_read(anon_vma);
2654}
2655
2656/*
2657 * rmap_walk_file - do something to file page using the object-based rmap method
2658 * @folio: the folio to be handled
2659 * @rwc: control variable according to each walk type
2660 * @locked: caller holds relevant rmap lock
2661 *
2662 * Find all the mappings of a folio using the mapping pointer and the vma chains
2663 * contained in the address_space struct it points to.
2664 */
2665static void rmap_walk_file(struct folio *folio,
2666 struct rmap_walk_control *rwc, bool locked)
2667{
2668 struct address_space *mapping = folio_mapping(folio);
2669 pgoff_t pgoff_start, pgoff_end;
2670 struct vm_area_struct *vma;
2671
2672 /*
2673 * The page lock not only makes sure that page->mapping cannot
2674 * suddenly be NULLified by truncation, it makes sure that the
2675 * structure at mapping cannot be freed and reused yet,
2676 * so we can safely take mapping->i_mmap_rwsem.
2677 */
2678 VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
2679
2680 if (!mapping)
2681 return;
2682
2683 pgoff_start = folio_pgoff(folio);
2684 pgoff_end = pgoff_start + folio_nr_pages(folio) - 1;
2685 if (!locked) {
2686 if (i_mmap_trylock_read(mapping))
2687 goto lookup;
2688
2689 if (rwc->try_lock) {
2690 rwc->contended = true;
2691 return;
2692 }
2693
2694 i_mmap_lock_read(mapping);
2695 }
2696lookup:
2697 vma_interval_tree_foreach(vma, &mapping->i_mmap,
2698 pgoff_start, pgoff_end) {
2699 unsigned long address = vma_address(vma, pgoff_start,
2700 folio_nr_pages(folio));
2701
2702 VM_BUG_ON_VMA(address == -EFAULT, vma);
2703 cond_resched();
2704
2705 if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
2706 continue;
2707
2708 if (!rwc->rmap_one(folio, vma, address, rwc->arg))
2709 goto done;
2710 if (rwc->done && rwc->done(folio))
2711 goto done;
2712 }
2713
2714done:
2715 if (!locked)
2716 i_mmap_unlock_read(mapping);
2717}
2718
2719void rmap_walk(struct folio *folio, struct rmap_walk_control *rwc)
2720{
2721 if (unlikely(folio_test_ksm(folio)))
2722 rmap_walk_ksm(folio, rwc);
2723 else if (folio_test_anon(folio))
2724 rmap_walk_anon(folio, rwc, false);
2725 else
2726 rmap_walk_file(folio, rwc, false);
2727}
2728
2729/* Like rmap_walk, but caller holds relevant rmap lock */
2730void rmap_walk_locked(struct folio *folio, struct rmap_walk_control *rwc)
2731{
2732 /* no ksm support for now */
2733 VM_BUG_ON_FOLIO(folio_test_ksm(folio), folio);
2734 if (folio_test_anon(folio))
2735 rmap_walk_anon(folio, rwc, true);
2736 else
2737 rmap_walk_file(folio, rwc, true);
2738}
2739
2740#ifdef CONFIG_HUGETLB_PAGE
2741/*
2742 * The following two functions are for anonymous (private mapped) hugepages.
2743 * Unlike common anonymous pages, anonymous hugepages have no accounting code
2744 * and no lru code, because we handle hugepages differently from common pages.
2745 */
2746void hugetlb_add_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
2747 unsigned long address, rmap_t flags)
2748{
2749 VM_WARN_ON_FOLIO(!folio_test_hugetlb(folio), folio);
2750 VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio);
2751
2752 atomic_inc(&folio->_entire_mapcount);
2753 atomic_inc(&folio->_large_mapcount);
2754 if (flags & RMAP_EXCLUSIVE)
2755 SetPageAnonExclusive(&folio->page);
2756 VM_WARN_ON_FOLIO(folio_entire_mapcount(folio) > 1 &&
2757 PageAnonExclusive(&folio->page), folio);
2758}
2759
2760void hugetlb_add_new_anon_rmap(struct folio *folio,
2761 struct vm_area_struct *vma, unsigned long address)
2762{
2763 VM_WARN_ON_FOLIO(!folio_test_hugetlb(folio), folio);
2764
2765 BUG_ON(address < vma->vm_start || address >= vma->vm_end);
2766 /* increment count (starts at -1) */
2767 atomic_set(&folio->_entire_mapcount, 0);
2768 atomic_set(&folio->_large_mapcount, 0);
2769 folio_clear_hugetlb_restore_reserve(folio);
2770 __folio_set_anon(folio, vma, address, true);
2771 SetPageAnonExclusive(&folio->page);
2772}
2773#endif /* CONFIG_HUGETLB_PAGE */