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