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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_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, but if
152 * not we either need to find an adjacent mapping that we
153 * can re-use the anon_vma from (very common when the only
154 * reason for splitting a vma has been mprotect()), or we
155 * allocate a new one.
156 *
157 * Anon-vma allocations are very subtle, because we may have
158 * optimistically looked up an anon_vma in page_lock_anon_vma_read()
159 * and that may actually touch the spinlock even in the newly
160 * allocated vma (it depends on RCU to make sure that the
161 * anon_vma isn't actually destroyed).
162 *
163 * As a result, we need to do proper anon_vma locking even
164 * for the new allocation. At the same time, we do not want
165 * to do any locking for the common case of already having
166 * an anon_vma.
167 *
168 * This must be called with the mmap_sem held for reading.
169 */
170int anon_vma_prepare(struct vm_area_struct *vma)
171{
172 struct anon_vma *anon_vma = vma->anon_vma;
173 struct anon_vma_chain *avc;
174
175 might_sleep();
176 if (unlikely(!anon_vma)) {
177 struct mm_struct *mm = vma->vm_mm;
178 struct anon_vma *allocated;
179
180 avc = anon_vma_chain_alloc(GFP_KERNEL);
181 if (!avc)
182 goto out_enomem;
183
184 anon_vma = find_mergeable_anon_vma(vma);
185 allocated = NULL;
186 if (!anon_vma) {
187 anon_vma = anon_vma_alloc();
188 if (unlikely(!anon_vma))
189 goto out_enomem_free_avc;
190 allocated = anon_vma;
191 }
192
193 anon_vma_lock_write(anon_vma);
194 /* page_table_lock to protect against threads */
195 spin_lock(&mm->page_table_lock);
196 if (likely(!vma->anon_vma)) {
197 vma->anon_vma = anon_vma;
198 anon_vma_chain_link(vma, avc, anon_vma);
199 /* vma reference or self-parent link for new root */
200 anon_vma->degree++;
201 allocated = NULL;
202 avc = NULL;
203 }
204 spin_unlock(&mm->page_table_lock);
205 anon_vma_unlock_write(anon_vma);
206
207 if (unlikely(allocated))
208 put_anon_vma(allocated);
209 if (unlikely(avc))
210 anon_vma_chain_free(avc);
211 }
212 return 0;
213
214 out_enomem_free_avc:
215 anon_vma_chain_free(avc);
216 out_enomem:
217 return -ENOMEM;
218}
219
220/*
221 * This is a useful helper function for locking the anon_vma root as
222 * we traverse the vma->anon_vma_chain, looping over anon_vma's that
223 * have the same vma.
224 *
225 * Such anon_vma's should have the same root, so you'd expect to see
226 * just a single mutex_lock for the whole traversal.
227 */
228static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma)
229{
230 struct anon_vma *new_root = anon_vma->root;
231 if (new_root != root) {
232 if (WARN_ON_ONCE(root))
233 up_write(&root->rwsem);
234 root = new_root;
235 down_write(&root->rwsem);
236 }
237 return root;
238}
239
240static inline void unlock_anon_vma_root(struct anon_vma *root)
241{
242 if (root)
243 up_write(&root->rwsem);
244}
245
246/*
247 * Attach the anon_vmas from src to dst.
248 * Returns 0 on success, -ENOMEM on failure.
249 *
250 * If dst->anon_vma is NULL this function tries to find and reuse existing
251 * anon_vma which has no vmas and only one child anon_vma. This prevents
252 * degradation of anon_vma hierarchy to endless linear chain in case of
253 * constantly forking task. On the other hand, an anon_vma with more than one
254 * child isn't reused even if there was no alive vma, thus rmap walker has a
255 * good chance of avoiding scanning the whole hierarchy when it searches where
256 * page is mapped.
257 */
258int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
259{
260 struct anon_vma_chain *avc, *pavc;
261 struct anon_vma *root = NULL;
262
263 list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
264 struct anon_vma *anon_vma;
265
266 avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN);
267 if (unlikely(!avc)) {
268 unlock_anon_vma_root(root);
269 root = NULL;
270 avc = anon_vma_chain_alloc(GFP_KERNEL);
271 if (!avc)
272 goto enomem_failure;
273 }
274 anon_vma = pavc->anon_vma;
275 root = lock_anon_vma_root(root, anon_vma);
276 anon_vma_chain_link(dst, avc, anon_vma);
277
278 /*
279 * Reuse existing anon_vma if its degree lower than two,
280 * that means it has no vma and only one anon_vma child.
281 *
282 * Do not chose parent anon_vma, otherwise first child
283 * will always reuse it. Root anon_vma is never reused:
284 * it has self-parent reference and at least one child.
285 */
286 if (!dst->anon_vma && anon_vma != src->anon_vma &&
287 anon_vma->degree < 2)
288 dst->anon_vma = anon_vma;
289 }
290 if (dst->anon_vma)
291 dst->anon_vma->degree++;
292 unlock_anon_vma_root(root);
293 return 0;
294
295 enomem_failure:
296 /*
297 * dst->anon_vma is dropped here otherwise its degree can be incorrectly
298 * decremented in unlink_anon_vmas().
299 * We can safely do this because callers of anon_vma_clone() don't care
300 * about dst->anon_vma if anon_vma_clone() failed.
301 */
302 dst->anon_vma = NULL;
303 unlink_anon_vmas(dst);
304 return -ENOMEM;
305}
306
307/*
308 * Attach vma to its own anon_vma, as well as to the anon_vmas that
309 * the corresponding VMA in the parent process is attached to.
310 * Returns 0 on success, non-zero on failure.
311 */
312int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
313{
314 struct anon_vma_chain *avc;
315 struct anon_vma *anon_vma;
316 int error;
317
318 /* Don't bother if the parent process has no anon_vma here. */
319 if (!pvma->anon_vma)
320 return 0;
321
322 /* Drop inherited anon_vma, we'll reuse existing or allocate new. */
323 vma->anon_vma = NULL;
324
325 /*
326 * First, attach the new VMA to the parent VMA's anon_vmas,
327 * so rmap can find non-COWed pages in child processes.
328 */
329 error = anon_vma_clone(vma, pvma);
330 if (error)
331 return error;
332
333 /* An existing anon_vma has been reused, all done then. */
334 if (vma->anon_vma)
335 return 0;
336
337 /* Then add our own anon_vma. */
338 anon_vma = anon_vma_alloc();
339 if (!anon_vma)
340 goto out_error;
341 avc = anon_vma_chain_alloc(GFP_KERNEL);
342 if (!avc)
343 goto out_error_free_anon_vma;
344
345 /*
346 * The root anon_vma's spinlock is the lock actually used when we
347 * lock any of the anon_vmas in this anon_vma tree.
348 */
349 anon_vma->root = pvma->anon_vma->root;
350 anon_vma->parent = pvma->anon_vma;
351 /*
352 * With refcounts, an anon_vma can stay around longer than the
353 * process it belongs to. The root anon_vma needs to be pinned until
354 * this anon_vma is freed, because the lock lives in the root.
355 */
356 get_anon_vma(anon_vma->root);
357 /* Mark this anon_vma as the one where our new (COWed) pages go. */
358 vma->anon_vma = anon_vma;
359 anon_vma_lock_write(anon_vma);
360 anon_vma_chain_link(vma, avc, anon_vma);
361 anon_vma->parent->degree++;
362 anon_vma_unlock_write(anon_vma);
363
364 return 0;
365
366 out_error_free_anon_vma:
367 put_anon_vma(anon_vma);
368 out_error:
369 unlink_anon_vmas(vma);
370 return -ENOMEM;
371}
372
373void unlink_anon_vmas(struct vm_area_struct *vma)
374{
375 struct anon_vma_chain *avc, *next;
376 struct anon_vma *root = NULL;
377
378 /*
379 * Unlink each anon_vma chained to the VMA. This list is ordered
380 * from newest to oldest, ensuring the root anon_vma gets freed last.
381 */
382 list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
383 struct anon_vma *anon_vma = avc->anon_vma;
384
385 root = lock_anon_vma_root(root, anon_vma);
386 anon_vma_interval_tree_remove(avc, &anon_vma->rb_root);
387
388 /*
389 * Leave empty anon_vmas on the list - we'll need
390 * to free them outside the lock.
391 */
392 if (RB_EMPTY_ROOT(&anon_vma->rb_root)) {
393 anon_vma->parent->degree--;
394 continue;
395 }
396
397 list_del(&avc->same_vma);
398 anon_vma_chain_free(avc);
399 }
400 if (vma->anon_vma)
401 vma->anon_vma->degree--;
402 unlock_anon_vma_root(root);
403
404 /*
405 * Iterate the list once more, it now only contains empty and unlinked
406 * anon_vmas, destroy them. Could not do before due to __put_anon_vma()
407 * needing to write-acquire the anon_vma->root->rwsem.
408 */
409 list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
410 struct anon_vma *anon_vma = avc->anon_vma;
411
412 BUG_ON(anon_vma->degree);
413 put_anon_vma(anon_vma);
414
415 list_del(&avc->same_vma);
416 anon_vma_chain_free(avc);
417 }
418}
419
420static void anon_vma_ctor(void *data)
421{
422 struct anon_vma *anon_vma = data;
423
424 init_rwsem(&anon_vma->rwsem);
425 atomic_set(&anon_vma->refcount, 0);
426 anon_vma->rb_root = RB_ROOT;
427}
428
429void __init anon_vma_init(void)
430{
431 anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
432 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC|SLAB_ACCOUNT,
433 anon_vma_ctor);
434 anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain,
435 SLAB_PANIC|SLAB_ACCOUNT);
436}
437
438/*
439 * Getting a lock on a stable anon_vma from a page off the LRU is tricky!
440 *
441 * Since there is no serialization what so ever against page_remove_rmap()
442 * the best this function can do is return a locked anon_vma that might
443 * have been relevant to this page.
444 *
445 * The page might have been remapped to a different anon_vma or the anon_vma
446 * returned may already be freed (and even reused).
447 *
448 * In case it was remapped to a different anon_vma, the new anon_vma will be a
449 * child of the old anon_vma, and the anon_vma lifetime rules will therefore
450 * ensure that any anon_vma obtained from the page will still be valid for as
451 * long as we observe page_mapped() [ hence all those page_mapped() tests ].
452 *
453 * All users of this function must be very careful when walking the anon_vma
454 * chain and verify that the page in question is indeed mapped in it
455 * [ something equivalent to page_mapped_in_vma() ].
456 *
457 * Since anon_vma's slab is DESTROY_BY_RCU and we know from page_remove_rmap()
458 * that the anon_vma pointer from page->mapping is valid if there is a
459 * mapcount, we can dereference the anon_vma after observing those.
460 */
461struct anon_vma *page_get_anon_vma(struct page *page)
462{
463 struct anon_vma *anon_vma = NULL;
464 unsigned long anon_mapping;
465
466 rcu_read_lock();
467 anon_mapping = (unsigned long)READ_ONCE(page->mapping);
468 if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
469 goto out;
470 if (!page_mapped(page))
471 goto out;
472
473 anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
474 if (!atomic_inc_not_zero(&anon_vma->refcount)) {
475 anon_vma = NULL;
476 goto out;
477 }
478
479 /*
480 * If this page is still mapped, then its anon_vma cannot have been
481 * freed. But if it has been unmapped, we have no security against the
482 * anon_vma structure being freed and reused (for another anon_vma:
483 * SLAB_DESTROY_BY_RCU guarantees that - so the atomic_inc_not_zero()
484 * above cannot corrupt).
485 */
486 if (!page_mapped(page)) {
487 rcu_read_unlock();
488 put_anon_vma(anon_vma);
489 return NULL;
490 }
491out:
492 rcu_read_unlock();
493
494 return anon_vma;
495}
496
497/*
498 * Similar to page_get_anon_vma() except it locks the anon_vma.
499 *
500 * Its a little more complex as it tries to keep the fast path to a single
501 * atomic op -- the trylock. If we fail the trylock, we fall back to getting a
502 * reference like with page_get_anon_vma() and then block on the mutex.
503 */
504struct anon_vma *page_lock_anon_vma_read(struct page *page)
505{
506 struct anon_vma *anon_vma = NULL;
507 struct anon_vma *root_anon_vma;
508 unsigned long anon_mapping;
509
510 rcu_read_lock();
511 anon_mapping = (unsigned long)READ_ONCE(page->mapping);
512 if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
513 goto out;
514 if (!page_mapped(page))
515 goto out;
516
517 anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
518 root_anon_vma = READ_ONCE(anon_vma->root);
519 if (down_read_trylock(&root_anon_vma->rwsem)) {
520 /*
521 * If the page is still mapped, then this anon_vma is still
522 * its anon_vma, and holding the mutex ensures that it will
523 * not go away, see anon_vma_free().
524 */
525 if (!page_mapped(page)) {
526 up_read(&root_anon_vma->rwsem);
527 anon_vma = NULL;
528 }
529 goto out;
530 }
531
532 /* trylock failed, we got to sleep */
533 if (!atomic_inc_not_zero(&anon_vma->refcount)) {
534 anon_vma = NULL;
535 goto out;
536 }
537
538 if (!page_mapped(page)) {
539 rcu_read_unlock();
540 put_anon_vma(anon_vma);
541 return NULL;
542 }
543
544 /* we pinned the anon_vma, its safe to sleep */
545 rcu_read_unlock();
546 anon_vma_lock_read(anon_vma);
547
548 if (atomic_dec_and_test(&anon_vma->refcount)) {
549 /*
550 * Oops, we held the last refcount, release the lock
551 * and bail -- can't simply use put_anon_vma() because
552 * we'll deadlock on the anon_vma_lock_write() recursion.
553 */
554 anon_vma_unlock_read(anon_vma);
555 __put_anon_vma(anon_vma);
556 anon_vma = NULL;
557 }
558
559 return anon_vma;
560
561out:
562 rcu_read_unlock();
563 return anon_vma;
564}
565
566void page_unlock_anon_vma_read(struct anon_vma *anon_vma)
567{
568 anon_vma_unlock_read(anon_vma);
569}
570
571#ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
572/*
573 * Flush TLB entries for recently unmapped pages from remote CPUs. It is
574 * important if a PTE was dirty when it was unmapped that it's flushed
575 * before any IO is initiated on the page to prevent lost writes. Similarly,
576 * it must be flushed before freeing to prevent data leakage.
577 */
578void try_to_unmap_flush(void)
579{
580 struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc;
581 int cpu;
582
583 if (!tlb_ubc->flush_required)
584 return;
585
586 cpu = get_cpu();
587
588 if (cpumask_test_cpu(cpu, &tlb_ubc->cpumask)) {
589 count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL);
590 local_flush_tlb();
591 trace_tlb_flush(TLB_LOCAL_SHOOTDOWN, TLB_FLUSH_ALL);
592 }
593
594 if (cpumask_any_but(&tlb_ubc->cpumask, cpu) < nr_cpu_ids)
595 flush_tlb_others(&tlb_ubc->cpumask, NULL, 0, TLB_FLUSH_ALL);
596 cpumask_clear(&tlb_ubc->cpumask);
597 tlb_ubc->flush_required = false;
598 tlb_ubc->writable = false;
599 put_cpu();
600}
601
602/* Flush iff there are potentially writable TLB entries that can race with IO */
603void try_to_unmap_flush_dirty(void)
604{
605 struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc;
606
607 if (tlb_ubc->writable)
608 try_to_unmap_flush();
609}
610
611static void set_tlb_ubc_flush_pending(struct mm_struct *mm,
612 struct page *page, bool writable)
613{
614 struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc;
615
616 cpumask_or(&tlb_ubc->cpumask, &tlb_ubc->cpumask, mm_cpumask(mm));
617 tlb_ubc->flush_required = true;
618
619 /*
620 * If the PTE was dirty then it's best to assume it's writable. The
621 * caller must use try_to_unmap_flush_dirty() or try_to_unmap_flush()
622 * before the page is queued for IO.
623 */
624 if (writable)
625 tlb_ubc->writable = true;
626}
627
628/*
629 * Returns true if the TLB flush should be deferred to the end of a batch of
630 * unmap operations to reduce IPIs.
631 */
632static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
633{
634 bool should_defer = false;
635
636 if (!(flags & TTU_BATCH_FLUSH))
637 return false;
638
639 /* If remote CPUs need to be flushed then defer batch the flush */
640 if (cpumask_any_but(mm_cpumask(mm), get_cpu()) < nr_cpu_ids)
641 should_defer = true;
642 put_cpu();
643
644 return should_defer;
645}
646#else
647static void set_tlb_ubc_flush_pending(struct mm_struct *mm,
648 struct page *page, bool writable)
649{
650}
651
652static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
653{
654 return false;
655}
656#endif /* CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH */
657
658/*
659 * At what user virtual address is page expected in vma?
660 * Caller should check the page is actually part of the vma.
661 */
662unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
663{
664 unsigned long address;
665 if (PageAnon(page)) {
666 struct anon_vma *page__anon_vma = page_anon_vma(page);
667 /*
668 * Note: swapoff's unuse_vma() is more efficient with this
669 * check, and needs it to match anon_vma when KSM is active.
670 */
671 if (!vma->anon_vma || !page__anon_vma ||
672 vma->anon_vma->root != page__anon_vma->root)
673 return -EFAULT;
674 } else if (page->mapping) {
675 if (!vma->vm_file || vma->vm_file->f_mapping != page->mapping)
676 return -EFAULT;
677 } else
678 return -EFAULT;
679 address = __vma_address(page, vma);
680 if (unlikely(address < vma->vm_start || address >= vma->vm_end))
681 return -EFAULT;
682 return address;
683}
684
685pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address)
686{
687 pgd_t *pgd;
688 pud_t *pud;
689 pmd_t *pmd = NULL;
690 pmd_t pmde;
691
692 pgd = pgd_offset(mm, address);
693 if (!pgd_present(*pgd))
694 goto out;
695
696 pud = pud_offset(pgd, address);
697 if (!pud_present(*pud))
698 goto out;
699
700 pmd = pmd_offset(pud, address);
701 /*
702 * Some THP functions use the sequence pmdp_huge_clear_flush(), set_pmd_at()
703 * without holding anon_vma lock for write. So when looking for a
704 * genuine pmde (in which to find pte), test present and !THP together.
705 */
706 pmde = *pmd;
707 barrier();
708 if (!pmd_present(pmde) || pmd_trans_huge(pmde))
709 pmd = NULL;
710out:
711 return pmd;
712}
713
714/*
715 * Check that @page is mapped at @address into @mm.
716 *
717 * If @sync is false, page_check_address may perform a racy check to avoid
718 * the page table lock when the pte is not present (helpful when reclaiming
719 * highly shared pages).
720 *
721 * On success returns with pte mapped and locked.
722 */
723pte_t *__page_check_address(struct page *page, struct mm_struct *mm,
724 unsigned long address, spinlock_t **ptlp, int sync)
725{
726 pmd_t *pmd;
727 pte_t *pte;
728 spinlock_t *ptl;
729
730 if (unlikely(PageHuge(page))) {
731 /* when pud is not present, pte will be NULL */
732 pte = huge_pte_offset(mm, address);
733 if (!pte)
734 return NULL;
735
736 ptl = huge_pte_lockptr(page_hstate(page), mm, pte);
737 goto check;
738 }
739
740 pmd = mm_find_pmd(mm, address);
741 if (!pmd)
742 return NULL;
743
744 pte = pte_offset_map(pmd, address);
745 /* Make a quick check before getting the lock */
746 if (!sync && !pte_present(*pte)) {
747 pte_unmap(pte);
748 return NULL;
749 }
750
751 ptl = pte_lockptr(mm, pmd);
752check:
753 spin_lock(ptl);
754 if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) {
755 *ptlp = ptl;
756 return pte;
757 }
758 pte_unmap_unlock(pte, ptl);
759 return NULL;
760}
761
762/**
763 * page_mapped_in_vma - check whether a page is really mapped in a VMA
764 * @page: the page to test
765 * @vma: the VMA to test
766 *
767 * Returns 1 if the page is mapped into the page tables of the VMA, 0
768 * if the page is not mapped into the page tables of this VMA. Only
769 * valid for normal file or anonymous VMAs.
770 */
771int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
772{
773 unsigned long address;
774 pte_t *pte;
775 spinlock_t *ptl;
776
777 address = __vma_address(page, vma);
778 if (unlikely(address < vma->vm_start || address >= vma->vm_end))
779 return 0;
780 pte = page_check_address(page, vma->vm_mm, address, &ptl, 1);
781 if (!pte) /* the page is not in this mm */
782 return 0;
783 pte_unmap_unlock(pte, ptl);
784
785 return 1;
786}
787
788#ifdef CONFIG_TRANSPARENT_HUGEPAGE
789/*
790 * Check that @page is mapped at @address into @mm. In contrast to
791 * page_check_address(), this function can handle transparent huge pages.
792 *
793 * On success returns true with pte mapped and locked. For PMD-mapped
794 * transparent huge pages *@ptep is set to NULL.
795 */
796bool page_check_address_transhuge(struct page *page, struct mm_struct *mm,
797 unsigned long address, pmd_t **pmdp,
798 pte_t **ptep, spinlock_t **ptlp)
799{
800 pgd_t *pgd;
801 pud_t *pud;
802 pmd_t *pmd;
803 pte_t *pte;
804 spinlock_t *ptl;
805
806 if (unlikely(PageHuge(page))) {
807 /* when pud is not present, pte will be NULL */
808 pte = huge_pte_offset(mm, address);
809 if (!pte)
810 return false;
811
812 ptl = huge_pte_lockptr(page_hstate(page), mm, pte);
813 pmd = NULL;
814 goto check_pte;
815 }
816
817 pgd = pgd_offset(mm, address);
818 if (!pgd_present(*pgd))
819 return false;
820 pud = pud_offset(pgd, address);
821 if (!pud_present(*pud))
822 return false;
823 pmd = pmd_offset(pud, address);
824
825 if (pmd_trans_huge(*pmd)) {
826 ptl = pmd_lock(mm, pmd);
827 if (!pmd_present(*pmd))
828 goto unlock_pmd;
829 if (unlikely(!pmd_trans_huge(*pmd))) {
830 spin_unlock(ptl);
831 goto map_pte;
832 }
833
834 if (pmd_page(*pmd) != page)
835 goto unlock_pmd;
836
837 pte = NULL;
838 goto found;
839unlock_pmd:
840 spin_unlock(ptl);
841 return false;
842 } else {
843 pmd_t pmde = *pmd;
844
845 barrier();
846 if (!pmd_present(pmde) || pmd_trans_huge(pmde))
847 return false;
848 }
849map_pte:
850 pte = pte_offset_map(pmd, address);
851 if (!pte_present(*pte)) {
852 pte_unmap(pte);
853 return false;
854 }
855
856 ptl = pte_lockptr(mm, pmd);
857check_pte:
858 spin_lock(ptl);
859
860 if (!pte_present(*pte)) {
861 pte_unmap_unlock(pte, ptl);
862 return false;
863 }
864
865 /* THP can be referenced by any subpage */
866 if (pte_pfn(*pte) - page_to_pfn(page) >= hpage_nr_pages(page)) {
867 pte_unmap_unlock(pte, ptl);
868 return false;
869 }
870found:
871 *ptep = pte;
872 *pmdp = pmd;
873 *ptlp = ptl;
874 return true;
875}
876#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
877
878struct page_referenced_arg {
879 int mapcount;
880 int referenced;
881 unsigned long vm_flags;
882 struct mem_cgroup *memcg;
883};
884/*
885 * arg: page_referenced_arg will be passed
886 */
887static int page_referenced_one(struct page *page, struct vm_area_struct *vma,
888 unsigned long address, void *arg)
889{
890 struct mm_struct *mm = vma->vm_mm;
891 struct page_referenced_arg *pra = arg;
892 pmd_t *pmd;
893 pte_t *pte;
894 spinlock_t *ptl;
895 int referenced = 0;
896
897 if (!page_check_address_transhuge(page, mm, address, &pmd, &pte, &ptl))
898 return SWAP_AGAIN;
899
900 if (vma->vm_flags & VM_LOCKED) {
901 if (pte)
902 pte_unmap(pte);
903 spin_unlock(ptl);
904 pra->vm_flags |= VM_LOCKED;
905 return SWAP_FAIL; /* To break the loop */
906 }
907
908 if (pte) {
909 if (ptep_clear_flush_young_notify(vma, address, pte)) {
910 /*
911 * Don't treat a reference through a sequentially read
912 * mapping as such. If the page has been used in
913 * another mapping, we will catch it; if this other
914 * mapping is already gone, the unmap path will have
915 * set PG_referenced or activated the page.
916 */
917 if (likely(!(vma->vm_flags & VM_SEQ_READ)))
918 referenced++;
919 }
920 pte_unmap(pte);
921 } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
922 if (pmdp_clear_flush_young_notify(vma, address, pmd))
923 referenced++;
924 } else {
925 /* unexpected pmd-mapped page? */
926 WARN_ON_ONCE(1);
927 }
928 spin_unlock(ptl);
929
930 if (referenced)
931 clear_page_idle(page);
932 if (test_and_clear_page_young(page))
933 referenced++;
934
935 if (referenced) {
936 pra->referenced++;
937 pra->vm_flags |= vma->vm_flags;
938 }
939
940 pra->mapcount--;
941 if (!pra->mapcount)
942 return SWAP_SUCCESS; /* To break the loop */
943
944 return SWAP_AGAIN;
945}
946
947static bool invalid_page_referenced_vma(struct vm_area_struct *vma, void *arg)
948{
949 struct page_referenced_arg *pra = arg;
950 struct mem_cgroup *memcg = pra->memcg;
951
952 if (!mm_match_cgroup(vma->vm_mm, memcg))
953 return true;
954
955 return false;
956}
957
958/**
959 * page_referenced - test if the page was referenced
960 * @page: the page to test
961 * @is_locked: caller holds lock on the page
962 * @memcg: target memory cgroup
963 * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
964 *
965 * Quick test_and_clear_referenced for all mappings to a page,
966 * returns the number of ptes which referenced the page.
967 */
968int page_referenced(struct page *page,
969 int is_locked,
970 struct mem_cgroup *memcg,
971 unsigned long *vm_flags)
972{
973 int ret;
974 int we_locked = 0;
975 struct page_referenced_arg pra = {
976 .mapcount = total_mapcount(page),
977 .memcg = memcg,
978 };
979 struct rmap_walk_control rwc = {
980 .rmap_one = page_referenced_one,
981 .arg = (void *)&pra,
982 .anon_lock = page_lock_anon_vma_read,
983 };
984
985 *vm_flags = 0;
986 if (!page_mapped(page))
987 return 0;
988
989 if (!page_rmapping(page))
990 return 0;
991
992 if (!is_locked && (!PageAnon(page) || PageKsm(page))) {
993 we_locked = trylock_page(page);
994 if (!we_locked)
995 return 1;
996 }
997
998 /*
999 * If we are reclaiming on behalf of a cgroup, skip
1000 * counting on behalf of references from different
1001 * cgroups
1002 */
1003 if (memcg) {
1004 rwc.invalid_vma = invalid_page_referenced_vma;
1005 }
1006
1007 ret = rmap_walk(page, &rwc);
1008 *vm_flags = pra.vm_flags;
1009
1010 if (we_locked)
1011 unlock_page(page);
1012
1013 return pra.referenced;
1014}
1015
1016static int page_mkclean_one(struct page *page, struct vm_area_struct *vma,
1017 unsigned long address, void *arg)
1018{
1019 struct mm_struct *mm = vma->vm_mm;
1020 pte_t *pte;
1021 spinlock_t *ptl;
1022 int ret = 0;
1023 int *cleaned = arg;
1024
1025 pte = page_check_address(page, mm, address, &ptl, 1);
1026 if (!pte)
1027 goto out;
1028
1029 if (pte_dirty(*pte) || pte_write(*pte)) {
1030 pte_t entry;
1031
1032 flush_cache_page(vma, address, pte_pfn(*pte));
1033 entry = ptep_clear_flush(vma, address, pte);
1034 entry = pte_wrprotect(entry);
1035 entry = pte_mkclean(entry);
1036 set_pte_at(mm, address, pte, entry);
1037 ret = 1;
1038 }
1039
1040 pte_unmap_unlock(pte, ptl);
1041
1042 if (ret) {
1043 mmu_notifier_invalidate_page(mm, address);
1044 (*cleaned)++;
1045 }
1046out:
1047 return SWAP_AGAIN;
1048}
1049
1050static bool invalid_mkclean_vma(struct vm_area_struct *vma, void *arg)
1051{
1052 if (vma->vm_flags & VM_SHARED)
1053 return false;
1054
1055 return true;
1056}
1057
1058int page_mkclean(struct page *page)
1059{
1060 int cleaned = 0;
1061 struct address_space *mapping;
1062 struct rmap_walk_control rwc = {
1063 .arg = (void *)&cleaned,
1064 .rmap_one = page_mkclean_one,
1065 .invalid_vma = invalid_mkclean_vma,
1066 };
1067
1068 BUG_ON(!PageLocked(page));
1069
1070 if (!page_mapped(page))
1071 return 0;
1072
1073 mapping = page_mapping(page);
1074 if (!mapping)
1075 return 0;
1076
1077 rmap_walk(page, &rwc);
1078
1079 return cleaned;
1080}
1081EXPORT_SYMBOL_GPL(page_mkclean);
1082
1083/**
1084 * page_move_anon_rmap - move a page to our anon_vma
1085 * @page: the page to move to our anon_vma
1086 * @vma: the vma the page belongs to
1087 * @address: the user virtual address mapped
1088 *
1089 * When a page belongs exclusively to one process after a COW event,
1090 * that page can be moved into the anon_vma that belongs to just that
1091 * process, so the rmap code will not search the parent or sibling
1092 * processes.
1093 */
1094void page_move_anon_rmap(struct page *page,
1095 struct vm_area_struct *vma, unsigned long address)
1096{
1097 struct anon_vma *anon_vma = vma->anon_vma;
1098
1099 VM_BUG_ON_PAGE(!PageLocked(page), page);
1100 VM_BUG_ON_VMA(!anon_vma, vma);
1101 VM_BUG_ON_PAGE(page->index != linear_page_index(vma, address), page);
1102
1103 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1104 /*
1105 * Ensure that anon_vma and the PAGE_MAPPING_ANON bit are written
1106 * simultaneously, so a concurrent reader (eg page_referenced()'s
1107 * PageAnon()) will not see one without the other.
1108 */
1109 WRITE_ONCE(page->mapping, (struct address_space *) anon_vma);
1110}
1111
1112/**
1113 * __page_set_anon_rmap - set up new anonymous rmap
1114 * @page: Page to add to rmap
1115 * @vma: VM area to add page to.
1116 * @address: User virtual address of the mapping
1117 * @exclusive: the page is exclusively owned by the current process
1118 */
1119static void __page_set_anon_rmap(struct page *page,
1120 struct vm_area_struct *vma, unsigned long address, int exclusive)
1121{
1122 struct anon_vma *anon_vma = vma->anon_vma;
1123
1124 BUG_ON(!anon_vma);
1125
1126 if (PageAnon(page))
1127 return;
1128
1129 /*
1130 * If the page isn't exclusively mapped into this vma,
1131 * we must use the _oldest_ possible anon_vma for the
1132 * page mapping!
1133 */
1134 if (!exclusive)
1135 anon_vma = anon_vma->root;
1136
1137 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1138 page->mapping = (struct address_space *) anon_vma;
1139 page->index = linear_page_index(vma, address);
1140}
1141
1142/**
1143 * __page_check_anon_rmap - sanity check anonymous rmap addition
1144 * @page: the page to add the mapping to
1145 * @vma: the vm area in which the mapping is added
1146 * @address: the user virtual address mapped
1147 */
1148static void __page_check_anon_rmap(struct page *page,
1149 struct vm_area_struct *vma, unsigned long address)
1150{
1151#ifdef CONFIG_DEBUG_VM
1152 /*
1153 * The page's anon-rmap details (mapping and index) are guaranteed to
1154 * be set up correctly at this point.
1155 *
1156 * We have exclusion against page_add_anon_rmap because the caller
1157 * always holds the page locked, except if called from page_dup_rmap,
1158 * in which case the page is already known to be setup.
1159 *
1160 * We have exclusion against page_add_new_anon_rmap because those pages
1161 * are initially only visible via the pagetables, and the pte is locked
1162 * over the call to page_add_new_anon_rmap.
1163 */
1164 BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root);
1165 BUG_ON(page_to_pgoff(page) != linear_page_index(vma, address));
1166#endif
1167}
1168
1169/**
1170 * page_add_anon_rmap - add pte mapping to an anonymous page
1171 * @page: the page to add the mapping to
1172 * @vma: the vm area in which the mapping is added
1173 * @address: the user virtual address mapped
1174 * @compound: charge the page as compound or small page
1175 *
1176 * The caller needs to hold the pte lock, and the page must be locked in
1177 * the anon_vma case: to serialize mapping,index checking after setting,
1178 * and to ensure that PageAnon is not being upgraded racily to PageKsm
1179 * (but PageKsm is never downgraded to PageAnon).
1180 */
1181void page_add_anon_rmap(struct page *page,
1182 struct vm_area_struct *vma, unsigned long address, bool compound)
1183{
1184 do_page_add_anon_rmap(page, vma, address, compound ? RMAP_COMPOUND : 0);
1185}
1186
1187/*
1188 * Special version of the above for do_swap_page, which often runs
1189 * into pages that are exclusively owned by the current process.
1190 * Everybody else should continue to use page_add_anon_rmap above.
1191 */
1192void do_page_add_anon_rmap(struct page *page,
1193 struct vm_area_struct *vma, unsigned long address, int flags)
1194{
1195 bool compound = flags & RMAP_COMPOUND;
1196 bool first;
1197
1198 if (compound) {
1199 atomic_t *mapcount;
1200 VM_BUG_ON_PAGE(!PageLocked(page), page);
1201 VM_BUG_ON_PAGE(!PageTransHuge(page), page);
1202 mapcount = compound_mapcount_ptr(page);
1203 first = atomic_inc_and_test(mapcount);
1204 } else {
1205 first = atomic_inc_and_test(&page->_mapcount);
1206 }
1207
1208 if (first) {
1209 int nr = compound ? hpage_nr_pages(page) : 1;
1210 /*
1211 * We use the irq-unsafe __{inc|mod}_zone_page_stat because
1212 * these counters are not modified in interrupt context, and
1213 * pte lock(a spinlock) is held, which implies preemption
1214 * disabled.
1215 */
1216 if (compound) {
1217 __inc_zone_page_state(page,
1218 NR_ANON_TRANSPARENT_HUGEPAGES);
1219 }
1220 __mod_zone_page_state(page_zone(page), NR_ANON_PAGES, nr);
1221 }
1222 if (unlikely(PageKsm(page)))
1223 return;
1224
1225 VM_BUG_ON_PAGE(!PageLocked(page), page);
1226
1227 /* address might be in next vma when migration races vma_adjust */
1228 if (first)
1229 __page_set_anon_rmap(page, vma, address,
1230 flags & RMAP_EXCLUSIVE);
1231 else
1232 __page_check_anon_rmap(page, vma, address);
1233}
1234
1235/**
1236 * page_add_new_anon_rmap - add pte mapping to a new anonymous page
1237 * @page: the page to add the mapping to
1238 * @vma: the vm area in which the mapping is added
1239 * @address: the user virtual address mapped
1240 * @compound: charge the page as compound or small page
1241 *
1242 * Same as page_add_anon_rmap but must only be called on *new* pages.
1243 * This means the inc-and-test can be bypassed.
1244 * Page does not have to be locked.
1245 */
1246void page_add_new_anon_rmap(struct page *page,
1247 struct vm_area_struct *vma, unsigned long address, bool compound)
1248{
1249 int nr = compound ? hpage_nr_pages(page) : 1;
1250
1251 VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
1252 SetPageSwapBacked(page);
1253 if (compound) {
1254 VM_BUG_ON_PAGE(!PageTransHuge(page), page);
1255 /* increment count (starts at -1) */
1256 atomic_set(compound_mapcount_ptr(page), 0);
1257 __inc_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
1258 } else {
1259 /* Anon THP always mapped first with PMD */
1260 VM_BUG_ON_PAGE(PageTransCompound(page), page);
1261 /* increment count (starts at -1) */
1262 atomic_set(&page->_mapcount, 0);
1263 }
1264 __mod_zone_page_state(page_zone(page), NR_ANON_PAGES, nr);
1265 __page_set_anon_rmap(page, vma, address, 1);
1266}
1267
1268/**
1269 * page_add_file_rmap - add pte mapping to a file page
1270 * @page: the page to add the mapping to
1271 *
1272 * The caller needs to hold the pte lock.
1273 */
1274void page_add_file_rmap(struct page *page)
1275{
1276 lock_page_memcg(page);
1277 if (atomic_inc_and_test(&page->_mapcount)) {
1278 __inc_zone_page_state(page, NR_FILE_MAPPED);
1279 mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_FILE_MAPPED);
1280 }
1281 unlock_page_memcg(page);
1282}
1283
1284static void page_remove_file_rmap(struct page *page)
1285{
1286 lock_page_memcg(page);
1287
1288 /* Hugepages are not counted in NR_FILE_MAPPED for now. */
1289 if (unlikely(PageHuge(page))) {
1290 /* hugetlb pages are always mapped with pmds */
1291 atomic_dec(compound_mapcount_ptr(page));
1292 goto out;
1293 }
1294
1295 /* page still mapped by someone else? */
1296 if (!atomic_add_negative(-1, &page->_mapcount))
1297 goto out;
1298
1299 /*
1300 * We use the irq-unsafe __{inc|mod}_zone_page_stat because
1301 * these counters are not modified in interrupt context, and
1302 * pte lock(a spinlock) is held, which implies preemption disabled.
1303 */
1304 __dec_zone_page_state(page, NR_FILE_MAPPED);
1305 mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_FILE_MAPPED);
1306
1307 if (unlikely(PageMlocked(page)))
1308 clear_page_mlock(page);
1309out:
1310 unlock_page_memcg(page);
1311}
1312
1313static void page_remove_anon_compound_rmap(struct page *page)
1314{
1315 int i, nr;
1316
1317 if (!atomic_add_negative(-1, compound_mapcount_ptr(page)))
1318 return;
1319
1320 /* Hugepages are not counted in NR_ANON_PAGES for now. */
1321 if (unlikely(PageHuge(page)))
1322 return;
1323
1324 if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
1325 return;
1326
1327 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
1328
1329 if (TestClearPageDoubleMap(page)) {
1330 /*
1331 * Subpages can be mapped with PTEs too. Check how many of
1332 * themi are still mapped.
1333 */
1334 for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) {
1335 if (atomic_add_negative(-1, &page[i]._mapcount))
1336 nr++;
1337 }
1338 } else {
1339 nr = HPAGE_PMD_NR;
1340 }
1341
1342 if (unlikely(PageMlocked(page)))
1343 clear_page_mlock(page);
1344
1345 if (nr) {
1346 __mod_zone_page_state(page_zone(page), NR_ANON_PAGES, -nr);
1347 deferred_split_huge_page(page);
1348 }
1349}
1350
1351/**
1352 * page_remove_rmap - take down pte mapping from a page
1353 * @page: page to remove mapping from
1354 * @compound: uncharge the page as compound or small page
1355 *
1356 * The caller needs to hold the pte lock.
1357 */
1358void page_remove_rmap(struct page *page, bool compound)
1359{
1360 if (!PageAnon(page)) {
1361 VM_BUG_ON_PAGE(compound && !PageHuge(page), page);
1362 page_remove_file_rmap(page);
1363 return;
1364 }
1365
1366 if (compound)
1367 return page_remove_anon_compound_rmap(page);
1368
1369 /* page still mapped by someone else? */
1370 if (!atomic_add_negative(-1, &page->_mapcount))
1371 return;
1372
1373 /*
1374 * We use the irq-unsafe __{inc|mod}_zone_page_stat because
1375 * these counters are not modified in interrupt context, and
1376 * pte lock(a spinlock) is held, which implies preemption disabled.
1377 */
1378 __dec_zone_page_state(page, NR_ANON_PAGES);
1379
1380 if (unlikely(PageMlocked(page)))
1381 clear_page_mlock(page);
1382
1383 if (PageTransCompound(page))
1384 deferred_split_huge_page(compound_head(page));
1385
1386 /*
1387 * It would be tidy to reset the PageAnon mapping here,
1388 * but that might overwrite a racing page_add_anon_rmap
1389 * which increments mapcount after us but sets mapping
1390 * before us: so leave the reset to free_hot_cold_page,
1391 * and remember that it's only reliable while mapped.
1392 * Leaving it set also helps swapoff to reinstate ptes
1393 * faster for those pages still in swapcache.
1394 */
1395}
1396
1397struct rmap_private {
1398 enum ttu_flags flags;
1399 int lazyfreed;
1400};
1401
1402/*
1403 * @arg: enum ttu_flags will be passed to this argument
1404 */
1405static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
1406 unsigned long address, void *arg)
1407{
1408 struct mm_struct *mm = vma->vm_mm;
1409 pte_t *pte;
1410 pte_t pteval;
1411 spinlock_t *ptl;
1412 int ret = SWAP_AGAIN;
1413 struct rmap_private *rp = arg;
1414 enum ttu_flags flags = rp->flags;
1415
1416 /* munlock has nothing to gain from examining un-locked vmas */
1417 if ((flags & TTU_MUNLOCK) && !(vma->vm_flags & VM_LOCKED))
1418 goto out;
1419
1420 if (flags & TTU_SPLIT_HUGE_PMD) {
1421 split_huge_pmd_address(vma, address,
1422 flags & TTU_MIGRATION, page);
1423 /* check if we have anything to do after split */
1424 if (page_mapcount(page) == 0)
1425 goto out;
1426 }
1427
1428 pte = page_check_address(page, mm, address, &ptl, 0);
1429 if (!pte)
1430 goto out;
1431
1432 /*
1433 * If the page is mlock()d, we cannot swap it out.
1434 * If it's recently referenced (perhaps page_referenced
1435 * skipped over this mm) then we should reactivate it.
1436 */
1437 if (!(flags & TTU_IGNORE_MLOCK)) {
1438 if (vma->vm_flags & VM_LOCKED) {
1439 /* Holding pte lock, we do *not* need mmap_sem here */
1440 mlock_vma_page(page);
1441 ret = SWAP_MLOCK;
1442 goto out_unmap;
1443 }
1444 if (flags & TTU_MUNLOCK)
1445 goto out_unmap;
1446 }
1447 if (!(flags & TTU_IGNORE_ACCESS)) {
1448 if (ptep_clear_flush_young_notify(vma, address, pte)) {
1449 ret = SWAP_FAIL;
1450 goto out_unmap;
1451 }
1452 }
1453
1454 /* Nuke the page table entry. */
1455 flush_cache_page(vma, address, page_to_pfn(page));
1456 if (should_defer_flush(mm, flags)) {
1457 /*
1458 * We clear the PTE but do not flush so potentially a remote
1459 * CPU could still be writing to the page. If the entry was
1460 * previously clean then the architecture must guarantee that
1461 * a clear->dirty transition on a cached TLB entry is written
1462 * through and traps if the PTE is unmapped.
1463 */
1464 pteval = ptep_get_and_clear(mm, address, pte);
1465
1466 set_tlb_ubc_flush_pending(mm, page, pte_dirty(pteval));
1467 } else {
1468 pteval = ptep_clear_flush(vma, address, pte);
1469 }
1470
1471 /* Move the dirty bit to the physical page now the pte is gone. */
1472 if (pte_dirty(pteval))
1473 set_page_dirty(page);
1474
1475 /* Update high watermark before we lower rss */
1476 update_hiwater_rss(mm);
1477
1478 if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
1479 if (PageHuge(page)) {
1480 hugetlb_count_sub(1 << compound_order(page), mm);
1481 } else {
1482 dec_mm_counter(mm, mm_counter(page));
1483 }
1484 set_pte_at(mm, address, pte,
1485 swp_entry_to_pte(make_hwpoison_entry(page)));
1486 } else if (pte_unused(pteval)) {
1487 /*
1488 * The guest indicated that the page content is of no
1489 * interest anymore. Simply discard the pte, vmscan
1490 * will take care of the rest.
1491 */
1492 dec_mm_counter(mm, mm_counter(page));
1493 } else if (IS_ENABLED(CONFIG_MIGRATION) && (flags & TTU_MIGRATION)) {
1494 swp_entry_t entry;
1495 pte_t swp_pte;
1496 /*
1497 * Store the pfn of the page in a special migration
1498 * pte. do_swap_page() will wait until the migration
1499 * pte is removed and then restart fault handling.
1500 */
1501 entry = make_migration_entry(page, pte_write(pteval));
1502 swp_pte = swp_entry_to_pte(entry);
1503 if (pte_soft_dirty(pteval))
1504 swp_pte = pte_swp_mksoft_dirty(swp_pte);
1505 set_pte_at(mm, address, pte, swp_pte);
1506 } else if (PageAnon(page)) {
1507 swp_entry_t entry = { .val = page_private(page) };
1508 pte_t swp_pte;
1509 /*
1510 * Store the swap location in the pte.
1511 * See handle_pte_fault() ...
1512 */
1513 VM_BUG_ON_PAGE(!PageSwapCache(page), page);
1514
1515 if (!PageDirty(page) && (flags & TTU_LZFREE)) {
1516 /* It's a freeable page by MADV_FREE */
1517 dec_mm_counter(mm, MM_ANONPAGES);
1518 rp->lazyfreed++;
1519 goto discard;
1520 }
1521
1522 if (swap_duplicate(entry) < 0) {
1523 set_pte_at(mm, address, pte, pteval);
1524 ret = SWAP_FAIL;
1525 goto out_unmap;
1526 }
1527 if (list_empty(&mm->mmlist)) {
1528 spin_lock(&mmlist_lock);
1529 if (list_empty(&mm->mmlist))
1530 list_add(&mm->mmlist, &init_mm.mmlist);
1531 spin_unlock(&mmlist_lock);
1532 }
1533 dec_mm_counter(mm, MM_ANONPAGES);
1534 inc_mm_counter(mm, MM_SWAPENTS);
1535 swp_pte = swp_entry_to_pte(entry);
1536 if (pte_soft_dirty(pteval))
1537 swp_pte = pte_swp_mksoft_dirty(swp_pte);
1538 set_pte_at(mm, address, pte, swp_pte);
1539 } else
1540 dec_mm_counter(mm, mm_counter_file(page));
1541
1542discard:
1543 page_remove_rmap(page, PageHuge(page));
1544 put_page(page);
1545
1546out_unmap:
1547 pte_unmap_unlock(pte, ptl);
1548 if (ret != SWAP_FAIL && ret != SWAP_MLOCK && !(flags & TTU_MUNLOCK))
1549 mmu_notifier_invalidate_page(mm, address);
1550out:
1551 return ret;
1552}
1553
1554bool is_vma_temporary_stack(struct vm_area_struct *vma)
1555{
1556 int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP);
1557
1558 if (!maybe_stack)
1559 return false;
1560
1561 if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) ==
1562 VM_STACK_INCOMPLETE_SETUP)
1563 return true;
1564
1565 return false;
1566}
1567
1568static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg)
1569{
1570 return is_vma_temporary_stack(vma);
1571}
1572
1573static int page_mapcount_is_zero(struct page *page)
1574{
1575 return !page_mapcount(page);
1576}
1577
1578/**
1579 * try_to_unmap - try to remove all page table mappings to a page
1580 * @page: the page to get unmapped
1581 * @flags: action and flags
1582 *
1583 * Tries to remove all the page table entries which are mapping this
1584 * page, used in the pageout path. Caller must hold the page lock.
1585 * Return values are:
1586 *
1587 * SWAP_SUCCESS - we succeeded in removing all mappings
1588 * SWAP_AGAIN - we missed a mapping, try again later
1589 * SWAP_FAIL - the page is unswappable
1590 * SWAP_MLOCK - page is mlocked.
1591 */
1592int try_to_unmap(struct page *page, enum ttu_flags flags)
1593{
1594 int ret;
1595 struct rmap_private rp = {
1596 .flags = flags,
1597 .lazyfreed = 0,
1598 };
1599
1600 struct rmap_walk_control rwc = {
1601 .rmap_one = try_to_unmap_one,
1602 .arg = &rp,
1603 .done = page_mapcount_is_zero,
1604 .anon_lock = page_lock_anon_vma_read,
1605 };
1606
1607 /*
1608 * During exec, a temporary VMA is setup and later moved.
1609 * The VMA is moved under the anon_vma lock but not the
1610 * page tables leading to a race where migration cannot
1611 * find the migration ptes. Rather than increasing the
1612 * locking requirements of exec(), migration skips
1613 * temporary VMAs until after exec() completes.
1614 */
1615 if ((flags & TTU_MIGRATION) && !PageKsm(page) && PageAnon(page))
1616 rwc.invalid_vma = invalid_migration_vma;
1617
1618 if (flags & TTU_RMAP_LOCKED)
1619 ret = rmap_walk_locked(page, &rwc);
1620 else
1621 ret = rmap_walk(page, &rwc);
1622
1623 if (ret != SWAP_MLOCK && !page_mapcount(page)) {
1624 ret = SWAP_SUCCESS;
1625 if (rp.lazyfreed && !PageDirty(page))
1626 ret = SWAP_LZFREE;
1627 }
1628 return ret;
1629}
1630
1631static int page_not_mapped(struct page *page)
1632{
1633 return !page_mapped(page);
1634};
1635
1636/**
1637 * try_to_munlock - try to munlock a page
1638 * @page: the page to be munlocked
1639 *
1640 * Called from munlock code. Checks all of the VMAs mapping the page
1641 * to make sure nobody else has this page mlocked. The page will be
1642 * returned with PG_mlocked cleared if no other vmas have it mlocked.
1643 *
1644 * Return values are:
1645 *
1646 * SWAP_AGAIN - no vma is holding page mlocked, or,
1647 * SWAP_AGAIN - page mapped in mlocked vma -- couldn't acquire mmap sem
1648 * SWAP_FAIL - page cannot be located at present
1649 * SWAP_MLOCK - page is now mlocked.
1650 */
1651int try_to_munlock(struct page *page)
1652{
1653 int ret;
1654 struct rmap_private rp = {
1655 .flags = TTU_MUNLOCK,
1656 .lazyfreed = 0,
1657 };
1658
1659 struct rmap_walk_control rwc = {
1660 .rmap_one = try_to_unmap_one,
1661 .arg = &rp,
1662 .done = page_not_mapped,
1663 .anon_lock = page_lock_anon_vma_read,
1664
1665 };
1666
1667 VM_BUG_ON_PAGE(!PageLocked(page) || PageLRU(page), page);
1668
1669 ret = rmap_walk(page, &rwc);
1670 return ret;
1671}
1672
1673void __put_anon_vma(struct anon_vma *anon_vma)
1674{
1675 struct anon_vma *root = anon_vma->root;
1676
1677 anon_vma_free(anon_vma);
1678 if (root != anon_vma && atomic_dec_and_test(&root->refcount))
1679 anon_vma_free(root);
1680}
1681
1682static struct anon_vma *rmap_walk_anon_lock(struct page *page,
1683 struct rmap_walk_control *rwc)
1684{
1685 struct anon_vma *anon_vma;
1686
1687 if (rwc->anon_lock)
1688 return rwc->anon_lock(page);
1689
1690 /*
1691 * Note: remove_migration_ptes() cannot use page_lock_anon_vma_read()
1692 * because that depends on page_mapped(); but not all its usages
1693 * are holding mmap_sem. Users without mmap_sem are required to
1694 * take a reference count to prevent the anon_vma disappearing
1695 */
1696 anon_vma = page_anon_vma(page);
1697 if (!anon_vma)
1698 return NULL;
1699
1700 anon_vma_lock_read(anon_vma);
1701 return anon_vma;
1702}
1703
1704/*
1705 * rmap_walk_anon - do something to anonymous page using the object-based
1706 * rmap method
1707 * @page: the page to be handled
1708 * @rwc: control variable according to each walk type
1709 *
1710 * Find all the mappings of a page using the mapping pointer and the vma chains
1711 * contained in the anon_vma struct it points to.
1712 *
1713 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1714 * where the page was found will be held for write. So, we won't recheck
1715 * vm_flags for that VMA. That should be OK, because that vma shouldn't be
1716 * LOCKED.
1717 */
1718static int rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc,
1719 bool locked)
1720{
1721 struct anon_vma *anon_vma;
1722 pgoff_t pgoff;
1723 struct anon_vma_chain *avc;
1724 int ret = SWAP_AGAIN;
1725
1726 if (locked) {
1727 anon_vma = page_anon_vma(page);
1728 /* anon_vma disappear under us? */
1729 VM_BUG_ON_PAGE(!anon_vma, page);
1730 } else {
1731 anon_vma = rmap_walk_anon_lock(page, rwc);
1732 }
1733 if (!anon_vma)
1734 return ret;
1735
1736 pgoff = page_to_pgoff(page);
1737 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1738 struct vm_area_struct *vma = avc->vma;
1739 unsigned long address = vma_address(page, vma);
1740
1741 cond_resched();
1742
1743 if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
1744 continue;
1745
1746 ret = rwc->rmap_one(page, vma, address, rwc->arg);
1747 if (ret != SWAP_AGAIN)
1748 break;
1749 if (rwc->done && rwc->done(page))
1750 break;
1751 }
1752
1753 if (!locked)
1754 anon_vma_unlock_read(anon_vma);
1755 return ret;
1756}
1757
1758/*
1759 * rmap_walk_file - do something to file page using the object-based rmap method
1760 * @page: the page to be handled
1761 * @rwc: control variable according to each walk type
1762 *
1763 * Find all the mappings of a page using the mapping pointer and the vma chains
1764 * contained in the address_space struct it points to.
1765 *
1766 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1767 * where the page was found will be held for write. So, we won't recheck
1768 * vm_flags for that VMA. That should be OK, because that vma shouldn't be
1769 * LOCKED.
1770 */
1771static int rmap_walk_file(struct page *page, struct rmap_walk_control *rwc,
1772 bool locked)
1773{
1774 struct address_space *mapping = page_mapping(page);
1775 pgoff_t pgoff;
1776 struct vm_area_struct *vma;
1777 int ret = SWAP_AGAIN;
1778
1779 /*
1780 * The page lock not only makes sure that page->mapping cannot
1781 * suddenly be NULLified by truncation, it makes sure that the
1782 * structure at mapping cannot be freed and reused yet,
1783 * so we can safely take mapping->i_mmap_rwsem.
1784 */
1785 VM_BUG_ON_PAGE(!PageLocked(page), page);
1786
1787 if (!mapping)
1788 return ret;
1789
1790 pgoff = page_to_pgoff(page);
1791 if (!locked)
1792 i_mmap_lock_read(mapping);
1793 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
1794 unsigned long address = vma_address(page, vma);
1795
1796 cond_resched();
1797
1798 if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
1799 continue;
1800
1801 ret = rwc->rmap_one(page, vma, address, rwc->arg);
1802 if (ret != SWAP_AGAIN)
1803 goto done;
1804 if (rwc->done && rwc->done(page))
1805 goto done;
1806 }
1807
1808done:
1809 if (!locked)
1810 i_mmap_unlock_read(mapping);
1811 return ret;
1812}
1813
1814int rmap_walk(struct page *page, struct rmap_walk_control *rwc)
1815{
1816 if (unlikely(PageKsm(page)))
1817 return rmap_walk_ksm(page, rwc);
1818 else if (PageAnon(page))
1819 return rmap_walk_anon(page, rwc, false);
1820 else
1821 return rmap_walk_file(page, rwc, false);
1822}
1823
1824/* Like rmap_walk, but caller holds relevant rmap lock */
1825int rmap_walk_locked(struct page *page, struct rmap_walk_control *rwc)
1826{
1827 /* no ksm support for now */
1828 VM_BUG_ON_PAGE(PageKsm(page), page);
1829 if (PageAnon(page))
1830 return rmap_walk_anon(page, rwc, true);
1831 else
1832 return rmap_walk_file(page, rwc, true);
1833}
1834
1835#ifdef CONFIG_HUGETLB_PAGE
1836/*
1837 * The following three functions are for anonymous (private mapped) hugepages.
1838 * Unlike common anonymous pages, anonymous hugepages have no accounting code
1839 * and no lru code, because we handle hugepages differently from common pages.
1840 */
1841static void __hugepage_set_anon_rmap(struct page *page,
1842 struct vm_area_struct *vma, unsigned long address, int exclusive)
1843{
1844 struct anon_vma *anon_vma = vma->anon_vma;
1845
1846 BUG_ON(!anon_vma);
1847
1848 if (PageAnon(page))
1849 return;
1850 if (!exclusive)
1851 anon_vma = anon_vma->root;
1852
1853 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1854 page->mapping = (struct address_space *) anon_vma;
1855 page->index = linear_page_index(vma, address);
1856}
1857
1858void hugepage_add_anon_rmap(struct page *page,
1859 struct vm_area_struct *vma, unsigned long address)
1860{
1861 struct anon_vma *anon_vma = vma->anon_vma;
1862 int first;
1863
1864 BUG_ON(!PageLocked(page));
1865 BUG_ON(!anon_vma);
1866 /* address might be in next vma when migration races vma_adjust */
1867 first = atomic_inc_and_test(compound_mapcount_ptr(page));
1868 if (first)
1869 __hugepage_set_anon_rmap(page, vma, address, 0);
1870}
1871
1872void hugepage_add_new_anon_rmap(struct page *page,
1873 struct vm_area_struct *vma, unsigned long address)
1874{
1875 BUG_ON(address < vma->vm_start || address >= vma->vm_end);
1876 atomic_set(compound_mapcount_ptr(page), 0);
1877 __hugepage_set_anon_rmap(page, vma, address, 1);
1878}
1879#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 * i_pages 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 * i_pages 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/sched/mm.h>
50#include <linux/sched/task.h>
51#include <linux/pagemap.h>
52#include <linux/swap.h>
53#include <linux/swapops.h>
54#include <linux/slab.h>
55#include <linux/init.h>
56#include <linux/ksm.h>
57#include <linux/rmap.h>
58#include <linux/rcupdate.h>
59#include <linux/export.h>
60#include <linux/memcontrol.h>
61#include <linux/mmu_notifier.h>
62#include <linux/migrate.h>
63#include <linux/hugetlb.h>
64#include <linux/backing-dev.h>
65#include <linux/page_idle.h>
66#include <linux/memremap.h>
67
68#include <asm/tlbflush.h>
69
70#include <trace/events/tlb.h>
71
72#include "internal.h"
73
74static struct kmem_cache *anon_vma_cachep;
75static struct kmem_cache *anon_vma_chain_cachep;
76
77static inline struct anon_vma *anon_vma_alloc(void)
78{
79 struct anon_vma *anon_vma;
80
81 anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL);
82 if (anon_vma) {
83 atomic_set(&anon_vma->refcount, 1);
84 anon_vma->degree = 1; /* Reference for first vma */
85 anon_vma->parent = anon_vma;
86 /*
87 * Initialise the anon_vma root to point to itself. If called
88 * from fork, the root will be reset to the parents anon_vma.
89 */
90 anon_vma->root = anon_vma;
91 }
92
93 return anon_vma;
94}
95
96static inline void anon_vma_free(struct anon_vma *anon_vma)
97{
98 VM_BUG_ON(atomic_read(&anon_vma->refcount));
99
100 /*
101 * Synchronize against page_lock_anon_vma_read() such that
102 * we can safely hold the lock without the anon_vma getting
103 * freed.
104 *
105 * Relies on the full mb implied by the atomic_dec_and_test() from
106 * put_anon_vma() against the acquire barrier implied by
107 * down_read_trylock() from page_lock_anon_vma_read(). This orders:
108 *
109 * page_lock_anon_vma_read() VS put_anon_vma()
110 * down_read_trylock() atomic_dec_and_test()
111 * LOCK MB
112 * atomic_read() rwsem_is_locked()
113 *
114 * LOCK should suffice since the actual taking of the lock must
115 * happen _before_ what follows.
116 */
117 might_sleep();
118 if (rwsem_is_locked(&anon_vma->root->rwsem)) {
119 anon_vma_lock_write(anon_vma);
120 anon_vma_unlock_write(anon_vma);
121 }
122
123 kmem_cache_free(anon_vma_cachep, anon_vma);
124}
125
126static inline struct anon_vma_chain *anon_vma_chain_alloc(gfp_t gfp)
127{
128 return kmem_cache_alloc(anon_vma_chain_cachep, gfp);
129}
130
131static void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain)
132{
133 kmem_cache_free(anon_vma_chain_cachep, anon_vma_chain);
134}
135
136static void anon_vma_chain_link(struct vm_area_struct *vma,
137 struct anon_vma_chain *avc,
138 struct anon_vma *anon_vma)
139{
140 avc->vma = vma;
141 avc->anon_vma = anon_vma;
142 list_add(&avc->same_vma, &vma->anon_vma_chain);
143 anon_vma_interval_tree_insert(avc, &anon_vma->rb_root);
144}
145
146/**
147 * __anon_vma_prepare - attach an anon_vma to a memory region
148 * @vma: the memory region in question
149 *
150 * This makes sure the memory mapping described by 'vma' has
151 * an 'anon_vma' attached to it, so that we can associate the
152 * anonymous pages mapped into it with that anon_vma.
153 *
154 * The common case will be that we already have one, which
155 * is handled inline by anon_vma_prepare(). But if
156 * not we either need to find an adjacent mapping that we
157 * can re-use the anon_vma from (very common when the only
158 * reason for splitting a vma has been mprotect()), or we
159 * allocate a new one.
160 *
161 * Anon-vma allocations are very subtle, because we may have
162 * optimistically looked up an anon_vma in page_lock_anon_vma_read()
163 * and that may actually touch the spinlock even in the newly
164 * allocated vma (it depends on RCU to make sure that the
165 * anon_vma isn't actually destroyed).
166 *
167 * As a result, we need to do proper anon_vma locking even
168 * for the new allocation. At the same time, we do not want
169 * to do any locking for the common case of already having
170 * an anon_vma.
171 *
172 * This must be called with the mmap_sem held for reading.
173 */
174int __anon_vma_prepare(struct vm_area_struct *vma)
175{
176 struct mm_struct *mm = vma->vm_mm;
177 struct anon_vma *anon_vma, *allocated;
178 struct anon_vma_chain *avc;
179
180 might_sleep();
181
182 avc = anon_vma_chain_alloc(GFP_KERNEL);
183 if (!avc)
184 goto out_enomem;
185
186 anon_vma = find_mergeable_anon_vma(vma);
187 allocated = NULL;
188 if (!anon_vma) {
189 anon_vma = anon_vma_alloc();
190 if (unlikely(!anon_vma))
191 goto out_enomem_free_avc;
192 allocated = anon_vma;
193 }
194
195 anon_vma_lock_write(anon_vma);
196 /* page_table_lock to protect against threads */
197 spin_lock(&mm->page_table_lock);
198 if (likely(!vma->anon_vma)) {
199 vma->anon_vma = anon_vma;
200 anon_vma_chain_link(vma, avc, anon_vma);
201 /* vma reference or self-parent link for new root */
202 anon_vma->degree++;
203 allocated = NULL;
204 avc = NULL;
205 }
206 spin_unlock(&mm->page_table_lock);
207 anon_vma_unlock_write(anon_vma);
208
209 if (unlikely(allocated))
210 put_anon_vma(allocated);
211 if (unlikely(avc))
212 anon_vma_chain_free(avc);
213
214 return 0;
215
216 out_enomem_free_avc:
217 anon_vma_chain_free(avc);
218 out_enomem:
219 return -ENOMEM;
220}
221
222/*
223 * This is a useful helper function for locking the anon_vma root as
224 * we traverse the vma->anon_vma_chain, looping over anon_vma's that
225 * have the same vma.
226 *
227 * Such anon_vma's should have the same root, so you'd expect to see
228 * just a single mutex_lock for the whole traversal.
229 */
230static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma)
231{
232 struct anon_vma *new_root = anon_vma->root;
233 if (new_root != root) {
234 if (WARN_ON_ONCE(root))
235 up_write(&root->rwsem);
236 root = new_root;
237 down_write(&root->rwsem);
238 }
239 return root;
240}
241
242static inline void unlock_anon_vma_root(struct anon_vma *root)
243{
244 if (root)
245 up_write(&root->rwsem);
246}
247
248/*
249 * Attach the anon_vmas from src to dst.
250 * Returns 0 on success, -ENOMEM on failure.
251 *
252 * If dst->anon_vma is NULL this function tries to find and reuse existing
253 * anon_vma which has no vmas and only one child anon_vma. This prevents
254 * degradation of anon_vma hierarchy to endless linear chain in case of
255 * constantly forking task. On the other hand, an anon_vma with more than one
256 * child isn't reused even if there was no alive vma, thus rmap walker has a
257 * good chance of avoiding scanning the whole hierarchy when it searches where
258 * page is mapped.
259 */
260int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
261{
262 struct anon_vma_chain *avc, *pavc;
263 struct anon_vma *root = NULL;
264
265 list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
266 struct anon_vma *anon_vma;
267
268 avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN);
269 if (unlikely(!avc)) {
270 unlock_anon_vma_root(root);
271 root = NULL;
272 avc = anon_vma_chain_alloc(GFP_KERNEL);
273 if (!avc)
274 goto enomem_failure;
275 }
276 anon_vma = pavc->anon_vma;
277 root = lock_anon_vma_root(root, anon_vma);
278 anon_vma_chain_link(dst, avc, anon_vma);
279
280 /*
281 * Reuse existing anon_vma if its degree lower than two,
282 * that means it has no vma and only one anon_vma child.
283 *
284 * Do not chose parent anon_vma, otherwise first child
285 * will always reuse it. Root anon_vma is never reused:
286 * it has self-parent reference and at least one child.
287 */
288 if (!dst->anon_vma && anon_vma != src->anon_vma &&
289 anon_vma->degree < 2)
290 dst->anon_vma = anon_vma;
291 }
292 if (dst->anon_vma)
293 dst->anon_vma->degree++;
294 unlock_anon_vma_root(root);
295 return 0;
296
297 enomem_failure:
298 /*
299 * dst->anon_vma is dropped here otherwise its degree can be incorrectly
300 * decremented in unlink_anon_vmas().
301 * We can safely do this because callers of anon_vma_clone() don't care
302 * about dst->anon_vma if anon_vma_clone() failed.
303 */
304 dst->anon_vma = NULL;
305 unlink_anon_vmas(dst);
306 return -ENOMEM;
307}
308
309/*
310 * Attach vma to its own anon_vma, as well as to the anon_vmas that
311 * the corresponding VMA in the parent process is attached to.
312 * Returns 0 on success, non-zero on failure.
313 */
314int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
315{
316 struct anon_vma_chain *avc;
317 struct anon_vma *anon_vma;
318 int error;
319
320 /* Don't bother if the parent process has no anon_vma here. */
321 if (!pvma->anon_vma)
322 return 0;
323
324 /* Drop inherited anon_vma, we'll reuse existing or allocate new. */
325 vma->anon_vma = NULL;
326
327 /*
328 * First, attach the new VMA to the parent VMA's anon_vmas,
329 * so rmap can find non-COWed pages in child processes.
330 */
331 error = anon_vma_clone(vma, pvma);
332 if (error)
333 return error;
334
335 /* An existing anon_vma has been reused, all done then. */
336 if (vma->anon_vma)
337 return 0;
338
339 /* Then add our own anon_vma. */
340 anon_vma = anon_vma_alloc();
341 if (!anon_vma)
342 goto out_error;
343 avc = anon_vma_chain_alloc(GFP_KERNEL);
344 if (!avc)
345 goto out_error_free_anon_vma;
346
347 /*
348 * The root anon_vma's spinlock is the lock actually used when we
349 * lock any of the anon_vmas in this anon_vma tree.
350 */
351 anon_vma->root = pvma->anon_vma->root;
352 anon_vma->parent = pvma->anon_vma;
353 /*
354 * With refcounts, an anon_vma can stay around longer than the
355 * process it belongs to. The root anon_vma needs to be pinned until
356 * this anon_vma is freed, because the lock lives in the root.
357 */
358 get_anon_vma(anon_vma->root);
359 /* Mark this anon_vma as the one where our new (COWed) pages go. */
360 vma->anon_vma = anon_vma;
361 anon_vma_lock_write(anon_vma);
362 anon_vma_chain_link(vma, avc, anon_vma);
363 anon_vma->parent->degree++;
364 anon_vma_unlock_write(anon_vma);
365
366 return 0;
367
368 out_error_free_anon_vma:
369 put_anon_vma(anon_vma);
370 out_error:
371 unlink_anon_vmas(vma);
372 return -ENOMEM;
373}
374
375void unlink_anon_vmas(struct vm_area_struct *vma)
376{
377 struct anon_vma_chain *avc, *next;
378 struct anon_vma *root = NULL;
379
380 /*
381 * Unlink each anon_vma chained to the VMA. This list is ordered
382 * from newest to oldest, ensuring the root anon_vma gets freed last.
383 */
384 list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
385 struct anon_vma *anon_vma = avc->anon_vma;
386
387 root = lock_anon_vma_root(root, anon_vma);
388 anon_vma_interval_tree_remove(avc, &anon_vma->rb_root);
389
390 /*
391 * Leave empty anon_vmas on the list - we'll need
392 * to free them outside the lock.
393 */
394 if (RB_EMPTY_ROOT(&anon_vma->rb_root.rb_root)) {
395 anon_vma->parent->degree--;
396 continue;
397 }
398
399 list_del(&avc->same_vma);
400 anon_vma_chain_free(avc);
401 }
402 if (vma->anon_vma)
403 vma->anon_vma->degree--;
404 unlock_anon_vma_root(root);
405
406 /*
407 * Iterate the list once more, it now only contains empty and unlinked
408 * anon_vmas, destroy them. Could not do before due to __put_anon_vma()
409 * needing to write-acquire the anon_vma->root->rwsem.
410 */
411 list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
412 struct anon_vma *anon_vma = avc->anon_vma;
413
414 VM_WARN_ON(anon_vma->degree);
415 put_anon_vma(anon_vma);
416
417 list_del(&avc->same_vma);
418 anon_vma_chain_free(avc);
419 }
420}
421
422static void anon_vma_ctor(void *data)
423{
424 struct anon_vma *anon_vma = data;
425
426 init_rwsem(&anon_vma->rwsem);
427 atomic_set(&anon_vma->refcount, 0);
428 anon_vma->rb_root = RB_ROOT_CACHED;
429}
430
431void __init anon_vma_init(void)
432{
433 anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
434 0, SLAB_TYPESAFE_BY_RCU|SLAB_PANIC|SLAB_ACCOUNT,
435 anon_vma_ctor);
436 anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain,
437 SLAB_PANIC|SLAB_ACCOUNT);
438}
439
440/*
441 * Getting a lock on a stable anon_vma from a page off the LRU is tricky!
442 *
443 * Since there is no serialization what so ever against page_remove_rmap()
444 * the best this function can do is return a locked anon_vma that might
445 * have been relevant to this page.
446 *
447 * The page might have been remapped to a different anon_vma or the anon_vma
448 * returned may already be freed (and even reused).
449 *
450 * In case it was remapped to a different anon_vma, the new anon_vma will be a
451 * child of the old anon_vma, and the anon_vma lifetime rules will therefore
452 * ensure that any anon_vma obtained from the page will still be valid for as
453 * long as we observe page_mapped() [ hence all those page_mapped() tests ].
454 *
455 * All users of this function must be very careful when walking the anon_vma
456 * chain and verify that the page in question is indeed mapped in it
457 * [ something equivalent to page_mapped_in_vma() ].
458 *
459 * Since anon_vma's slab is DESTROY_BY_RCU and we know from page_remove_rmap()
460 * that the anon_vma pointer from page->mapping is valid if there is a
461 * mapcount, we can dereference the anon_vma after observing those.
462 */
463struct anon_vma *page_get_anon_vma(struct page *page)
464{
465 struct anon_vma *anon_vma = NULL;
466 unsigned long anon_mapping;
467
468 rcu_read_lock();
469 anon_mapping = (unsigned long)READ_ONCE(page->mapping);
470 if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
471 goto out;
472 if (!page_mapped(page))
473 goto out;
474
475 anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
476 if (!atomic_inc_not_zero(&anon_vma->refcount)) {
477 anon_vma = NULL;
478 goto out;
479 }
480
481 /*
482 * If this page is still mapped, then its anon_vma cannot have been
483 * freed. But if it has been unmapped, we have no security against the
484 * anon_vma structure being freed and reused (for another anon_vma:
485 * SLAB_TYPESAFE_BY_RCU guarantees that - so the atomic_inc_not_zero()
486 * above cannot corrupt).
487 */
488 if (!page_mapped(page)) {
489 rcu_read_unlock();
490 put_anon_vma(anon_vma);
491 return NULL;
492 }
493out:
494 rcu_read_unlock();
495
496 return anon_vma;
497}
498
499/*
500 * Similar to page_get_anon_vma() except it locks the anon_vma.
501 *
502 * Its a little more complex as it tries to keep the fast path to a single
503 * atomic op -- the trylock. If we fail the trylock, we fall back to getting a
504 * reference like with page_get_anon_vma() and then block on the mutex.
505 */
506struct anon_vma *page_lock_anon_vma_read(struct page *page)
507{
508 struct anon_vma *anon_vma = NULL;
509 struct anon_vma *root_anon_vma;
510 unsigned long anon_mapping;
511
512 rcu_read_lock();
513 anon_mapping = (unsigned long)READ_ONCE(page->mapping);
514 if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
515 goto out;
516 if (!page_mapped(page))
517 goto out;
518
519 anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
520 root_anon_vma = READ_ONCE(anon_vma->root);
521 if (down_read_trylock(&root_anon_vma->rwsem)) {
522 /*
523 * If the page is still mapped, then this anon_vma is still
524 * its anon_vma, and holding the mutex ensures that it will
525 * not go away, see anon_vma_free().
526 */
527 if (!page_mapped(page)) {
528 up_read(&root_anon_vma->rwsem);
529 anon_vma = NULL;
530 }
531 goto out;
532 }
533
534 /* trylock failed, we got to sleep */
535 if (!atomic_inc_not_zero(&anon_vma->refcount)) {
536 anon_vma = NULL;
537 goto out;
538 }
539
540 if (!page_mapped(page)) {
541 rcu_read_unlock();
542 put_anon_vma(anon_vma);
543 return NULL;
544 }
545
546 /* we pinned the anon_vma, its safe to sleep */
547 rcu_read_unlock();
548 anon_vma_lock_read(anon_vma);
549
550 if (atomic_dec_and_test(&anon_vma->refcount)) {
551 /*
552 * Oops, we held the last refcount, release the lock
553 * and bail -- can't simply use put_anon_vma() because
554 * we'll deadlock on the anon_vma_lock_write() recursion.
555 */
556 anon_vma_unlock_read(anon_vma);
557 __put_anon_vma(anon_vma);
558 anon_vma = NULL;
559 }
560
561 return anon_vma;
562
563out:
564 rcu_read_unlock();
565 return anon_vma;
566}
567
568void page_unlock_anon_vma_read(struct anon_vma *anon_vma)
569{
570 anon_vma_unlock_read(anon_vma);
571}
572
573#ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
574/*
575 * Flush TLB entries for recently unmapped pages from remote CPUs. It is
576 * important if a PTE was dirty when it was unmapped that it's flushed
577 * before any IO is initiated on the page to prevent lost writes. Similarly,
578 * it must be flushed before freeing to prevent data leakage.
579 */
580void try_to_unmap_flush(void)
581{
582 struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc;
583
584 if (!tlb_ubc->flush_required)
585 return;
586
587 arch_tlbbatch_flush(&tlb_ubc->arch);
588 tlb_ubc->flush_required = false;
589 tlb_ubc->writable = false;
590}
591
592/* Flush iff there are potentially writable TLB entries that can race with IO */
593void try_to_unmap_flush_dirty(void)
594{
595 struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc;
596
597 if (tlb_ubc->writable)
598 try_to_unmap_flush();
599}
600
601static void set_tlb_ubc_flush_pending(struct mm_struct *mm, bool writable)
602{
603 struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc;
604
605 arch_tlbbatch_add_mm(&tlb_ubc->arch, mm);
606 tlb_ubc->flush_required = true;
607
608 /*
609 * Ensure compiler does not re-order the setting of tlb_flush_batched
610 * before the PTE is cleared.
611 */
612 barrier();
613 mm->tlb_flush_batched = true;
614
615 /*
616 * If the PTE was dirty then it's best to assume it's writable. The
617 * caller must use try_to_unmap_flush_dirty() or try_to_unmap_flush()
618 * before the page is queued for IO.
619 */
620 if (writable)
621 tlb_ubc->writable = true;
622}
623
624/*
625 * Returns true if the TLB flush should be deferred to the end of a batch of
626 * unmap operations to reduce IPIs.
627 */
628static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
629{
630 bool should_defer = false;
631
632 if (!(flags & TTU_BATCH_FLUSH))
633 return false;
634
635 /* If remote CPUs need to be flushed then defer batch the flush */
636 if (cpumask_any_but(mm_cpumask(mm), get_cpu()) < nr_cpu_ids)
637 should_defer = true;
638 put_cpu();
639
640 return should_defer;
641}
642
643/*
644 * Reclaim unmaps pages under the PTL but do not flush the TLB prior to
645 * releasing the PTL if TLB flushes are batched. It's possible for a parallel
646 * operation such as mprotect or munmap to race between reclaim unmapping
647 * the page and flushing the page. If this race occurs, it potentially allows
648 * access to data via a stale TLB entry. Tracking all mm's that have TLB
649 * batching in flight would be expensive during reclaim so instead track
650 * whether TLB batching occurred in the past and if so then do a flush here
651 * if required. This will cost one additional flush per reclaim cycle paid
652 * by the first operation at risk such as mprotect and mumap.
653 *
654 * This must be called under the PTL so that an access to tlb_flush_batched
655 * that is potentially a "reclaim vs mprotect/munmap/etc" race will synchronise
656 * via the PTL.
657 */
658void flush_tlb_batched_pending(struct mm_struct *mm)
659{
660 if (mm->tlb_flush_batched) {
661 flush_tlb_mm(mm);
662
663 /*
664 * Do not allow the compiler to re-order the clearing of
665 * tlb_flush_batched before the tlb is flushed.
666 */
667 barrier();
668 mm->tlb_flush_batched = false;
669 }
670}
671#else
672static void set_tlb_ubc_flush_pending(struct mm_struct *mm, bool writable)
673{
674}
675
676static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
677{
678 return false;
679}
680#endif /* CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH */
681
682/*
683 * At what user virtual address is page expected in vma?
684 * Caller should check the page is actually part of the vma.
685 */
686unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
687{
688 unsigned long address;
689 if (PageAnon(page)) {
690 struct anon_vma *page__anon_vma = page_anon_vma(page);
691 /*
692 * Note: swapoff's unuse_vma() is more efficient with this
693 * check, and needs it to match anon_vma when KSM is active.
694 */
695 if (!vma->anon_vma || !page__anon_vma ||
696 vma->anon_vma->root != page__anon_vma->root)
697 return -EFAULT;
698 } else if (page->mapping) {
699 if (!vma->vm_file || vma->vm_file->f_mapping != page->mapping)
700 return -EFAULT;
701 } else
702 return -EFAULT;
703 address = __vma_address(page, vma);
704 if (unlikely(address < vma->vm_start || address >= vma->vm_end))
705 return -EFAULT;
706 return address;
707}
708
709pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address)
710{
711 pgd_t *pgd;
712 p4d_t *p4d;
713 pud_t *pud;
714 pmd_t *pmd = NULL;
715 pmd_t pmde;
716
717 pgd = pgd_offset(mm, address);
718 if (!pgd_present(*pgd))
719 goto out;
720
721 p4d = p4d_offset(pgd, address);
722 if (!p4d_present(*p4d))
723 goto out;
724
725 pud = pud_offset(p4d, address);
726 if (!pud_present(*pud))
727 goto out;
728
729 pmd = pmd_offset(pud, address);
730 /*
731 * Some THP functions use the sequence pmdp_huge_clear_flush(), set_pmd_at()
732 * without holding anon_vma lock for write. So when looking for a
733 * genuine pmde (in which to find pte), test present and !THP together.
734 */
735 pmde = *pmd;
736 barrier();
737 if (!pmd_present(pmde) || pmd_trans_huge(pmde))
738 pmd = NULL;
739out:
740 return pmd;
741}
742
743struct page_referenced_arg {
744 int mapcount;
745 int referenced;
746 unsigned long vm_flags;
747 struct mem_cgroup *memcg;
748};
749/*
750 * arg: page_referenced_arg will be passed
751 */
752static bool page_referenced_one(struct page *page, struct vm_area_struct *vma,
753 unsigned long address, void *arg)
754{
755 struct page_referenced_arg *pra = arg;
756 struct page_vma_mapped_walk pvmw = {
757 .page = page,
758 .vma = vma,
759 .address = address,
760 };
761 int referenced = 0;
762
763 while (page_vma_mapped_walk(&pvmw)) {
764 address = pvmw.address;
765
766 if (vma->vm_flags & VM_LOCKED) {
767 page_vma_mapped_walk_done(&pvmw);
768 pra->vm_flags |= VM_LOCKED;
769 return false; /* To break the loop */
770 }
771
772 if (pvmw.pte) {
773 if (ptep_clear_flush_young_notify(vma, address,
774 pvmw.pte)) {
775 /*
776 * Don't treat a reference through
777 * a sequentially read mapping as such.
778 * If the page has been used in another mapping,
779 * we will catch it; if this other mapping is
780 * already gone, the unmap path will have set
781 * PG_referenced or activated the page.
782 */
783 if (likely(!(vma->vm_flags & VM_SEQ_READ)))
784 referenced++;
785 }
786 } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
787 if (pmdp_clear_flush_young_notify(vma, address,
788 pvmw.pmd))
789 referenced++;
790 } else {
791 /* unexpected pmd-mapped page? */
792 WARN_ON_ONCE(1);
793 }
794
795 pra->mapcount--;
796 }
797
798 if (referenced)
799 clear_page_idle(page);
800 if (test_and_clear_page_young(page))
801 referenced++;
802
803 if (referenced) {
804 pra->referenced++;
805 pra->vm_flags |= vma->vm_flags;
806 }
807
808 if (!pra->mapcount)
809 return false; /* To break the loop */
810
811 return true;
812}
813
814static bool invalid_page_referenced_vma(struct vm_area_struct *vma, void *arg)
815{
816 struct page_referenced_arg *pra = arg;
817 struct mem_cgroup *memcg = pra->memcg;
818
819 if (!mm_match_cgroup(vma->vm_mm, memcg))
820 return true;
821
822 return false;
823}
824
825/**
826 * page_referenced - test if the page was referenced
827 * @page: the page to test
828 * @is_locked: caller holds lock on the page
829 * @memcg: target memory cgroup
830 * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
831 *
832 * Quick test_and_clear_referenced for all mappings to a page,
833 * returns the number of ptes which referenced the page.
834 */
835int page_referenced(struct page *page,
836 int is_locked,
837 struct mem_cgroup *memcg,
838 unsigned long *vm_flags)
839{
840 int we_locked = 0;
841 struct page_referenced_arg pra = {
842 .mapcount = total_mapcount(page),
843 .memcg = memcg,
844 };
845 struct rmap_walk_control rwc = {
846 .rmap_one = page_referenced_one,
847 .arg = (void *)&pra,
848 .anon_lock = page_lock_anon_vma_read,
849 };
850
851 *vm_flags = 0;
852 if (!page_mapped(page))
853 return 0;
854
855 if (!page_rmapping(page))
856 return 0;
857
858 if (!is_locked && (!PageAnon(page) || PageKsm(page))) {
859 we_locked = trylock_page(page);
860 if (!we_locked)
861 return 1;
862 }
863
864 /*
865 * If we are reclaiming on behalf of a cgroup, skip
866 * counting on behalf of references from different
867 * cgroups
868 */
869 if (memcg) {
870 rwc.invalid_vma = invalid_page_referenced_vma;
871 }
872
873 rmap_walk(page, &rwc);
874 *vm_flags = pra.vm_flags;
875
876 if (we_locked)
877 unlock_page(page);
878
879 return pra.referenced;
880}
881
882static bool page_mkclean_one(struct page *page, struct vm_area_struct *vma,
883 unsigned long address, void *arg)
884{
885 struct page_vma_mapped_walk pvmw = {
886 .page = page,
887 .vma = vma,
888 .address = address,
889 .flags = PVMW_SYNC,
890 };
891 unsigned long start = address, end;
892 int *cleaned = arg;
893
894 /*
895 * We have to assume the worse case ie pmd for invalidation. Note that
896 * the page can not be free from this function.
897 */
898 end = min(vma->vm_end, start + (PAGE_SIZE << compound_order(page)));
899 mmu_notifier_invalidate_range_start(vma->vm_mm, start, end);
900
901 while (page_vma_mapped_walk(&pvmw)) {
902 unsigned long cstart;
903 int ret = 0;
904
905 cstart = address = pvmw.address;
906 if (pvmw.pte) {
907 pte_t entry;
908 pte_t *pte = pvmw.pte;
909
910 if (!pte_dirty(*pte) && !pte_write(*pte))
911 continue;
912
913 flush_cache_page(vma, address, pte_pfn(*pte));
914 entry = ptep_clear_flush(vma, address, pte);
915 entry = pte_wrprotect(entry);
916 entry = pte_mkclean(entry);
917 set_pte_at(vma->vm_mm, address, pte, entry);
918 ret = 1;
919 } else {
920#ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
921 pmd_t *pmd = pvmw.pmd;
922 pmd_t entry;
923
924 if (!pmd_dirty(*pmd) && !pmd_write(*pmd))
925 continue;
926
927 flush_cache_page(vma, address, page_to_pfn(page));
928 entry = pmdp_huge_clear_flush(vma, address, pmd);
929 entry = pmd_wrprotect(entry);
930 entry = pmd_mkclean(entry);
931 set_pmd_at(vma->vm_mm, address, pmd, entry);
932 cstart &= PMD_MASK;
933 ret = 1;
934#else
935 /* unexpected pmd-mapped page? */
936 WARN_ON_ONCE(1);
937#endif
938 }
939
940 /*
941 * No need to call mmu_notifier_invalidate_range() as we are
942 * downgrading page table protection not changing it to point
943 * to a new page.
944 *
945 * See Documentation/vm/mmu_notifier.txt
946 */
947 if (ret)
948 (*cleaned)++;
949 }
950
951 mmu_notifier_invalidate_range_end(vma->vm_mm, start, end);
952
953 return true;
954}
955
956static bool invalid_mkclean_vma(struct vm_area_struct *vma, void *arg)
957{
958 if (vma->vm_flags & VM_SHARED)
959 return false;
960
961 return true;
962}
963
964int page_mkclean(struct page *page)
965{
966 int cleaned = 0;
967 struct address_space *mapping;
968 struct rmap_walk_control rwc = {
969 .arg = (void *)&cleaned,
970 .rmap_one = page_mkclean_one,
971 .invalid_vma = invalid_mkclean_vma,
972 };
973
974 BUG_ON(!PageLocked(page));
975
976 if (!page_mapped(page))
977 return 0;
978
979 mapping = page_mapping(page);
980 if (!mapping)
981 return 0;
982
983 rmap_walk(page, &rwc);
984
985 return cleaned;
986}
987EXPORT_SYMBOL_GPL(page_mkclean);
988
989/**
990 * page_move_anon_rmap - move a page to our anon_vma
991 * @page: the page to move to our anon_vma
992 * @vma: the vma the page belongs to
993 *
994 * When a page belongs exclusively to one process after a COW event,
995 * that page can be moved into the anon_vma that belongs to just that
996 * process, so the rmap code will not search the parent or sibling
997 * processes.
998 */
999void page_move_anon_rmap(struct page *page, struct vm_area_struct *vma)
1000{
1001 struct anon_vma *anon_vma = vma->anon_vma;
1002
1003 page = compound_head(page);
1004
1005 VM_BUG_ON_PAGE(!PageLocked(page), page);
1006 VM_BUG_ON_VMA(!anon_vma, vma);
1007
1008 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1009 /*
1010 * Ensure that anon_vma and the PAGE_MAPPING_ANON bit are written
1011 * simultaneously, so a concurrent reader (eg page_referenced()'s
1012 * PageAnon()) will not see one without the other.
1013 */
1014 WRITE_ONCE(page->mapping, (struct address_space *) anon_vma);
1015}
1016
1017/**
1018 * __page_set_anon_rmap - set up new anonymous rmap
1019 * @page: Page to add to rmap
1020 * @vma: VM area to add page to.
1021 * @address: User virtual address of the mapping
1022 * @exclusive: the page is exclusively owned by the current process
1023 */
1024static void __page_set_anon_rmap(struct page *page,
1025 struct vm_area_struct *vma, unsigned long address, int exclusive)
1026{
1027 struct anon_vma *anon_vma = vma->anon_vma;
1028
1029 BUG_ON(!anon_vma);
1030
1031 if (PageAnon(page))
1032 return;
1033
1034 /*
1035 * If the page isn't exclusively mapped into this vma,
1036 * we must use the _oldest_ possible anon_vma for the
1037 * page mapping!
1038 */
1039 if (!exclusive)
1040 anon_vma = anon_vma->root;
1041
1042 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1043 page->mapping = (struct address_space *) anon_vma;
1044 page->index = linear_page_index(vma, address);
1045}
1046
1047/**
1048 * __page_check_anon_rmap - sanity check anonymous rmap addition
1049 * @page: the page to add the mapping to
1050 * @vma: the vm area in which the mapping is added
1051 * @address: the user virtual address mapped
1052 */
1053static void __page_check_anon_rmap(struct page *page,
1054 struct vm_area_struct *vma, unsigned long address)
1055{
1056#ifdef CONFIG_DEBUG_VM
1057 /*
1058 * The page's anon-rmap details (mapping and index) are guaranteed to
1059 * be set up correctly at this point.
1060 *
1061 * We have exclusion against page_add_anon_rmap because the caller
1062 * always holds the page locked, except if called from page_dup_rmap,
1063 * in which case the page is already known to be setup.
1064 *
1065 * We have exclusion against page_add_new_anon_rmap because those pages
1066 * are initially only visible via the pagetables, and the pte is locked
1067 * over the call to page_add_new_anon_rmap.
1068 */
1069 BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root);
1070 BUG_ON(page_to_pgoff(page) != linear_page_index(vma, address));
1071#endif
1072}
1073
1074/**
1075 * page_add_anon_rmap - add pte mapping to an anonymous page
1076 * @page: the page to add the mapping to
1077 * @vma: the vm area in which the mapping is added
1078 * @address: the user virtual address mapped
1079 * @compound: charge the page as compound or small page
1080 *
1081 * The caller needs to hold the pte lock, and the page must be locked in
1082 * the anon_vma case: to serialize mapping,index checking after setting,
1083 * and to ensure that PageAnon is not being upgraded racily to PageKsm
1084 * (but PageKsm is never downgraded to PageAnon).
1085 */
1086void page_add_anon_rmap(struct page *page,
1087 struct vm_area_struct *vma, unsigned long address, bool compound)
1088{
1089 do_page_add_anon_rmap(page, vma, address, compound ? RMAP_COMPOUND : 0);
1090}
1091
1092/*
1093 * Special version of the above for do_swap_page, which often runs
1094 * into pages that are exclusively owned by the current process.
1095 * Everybody else should continue to use page_add_anon_rmap above.
1096 */
1097void do_page_add_anon_rmap(struct page *page,
1098 struct vm_area_struct *vma, unsigned long address, int flags)
1099{
1100 bool compound = flags & RMAP_COMPOUND;
1101 bool first;
1102
1103 if (compound) {
1104 atomic_t *mapcount;
1105 VM_BUG_ON_PAGE(!PageLocked(page), page);
1106 VM_BUG_ON_PAGE(!PageTransHuge(page), page);
1107 mapcount = compound_mapcount_ptr(page);
1108 first = atomic_inc_and_test(mapcount);
1109 } else {
1110 first = atomic_inc_and_test(&page->_mapcount);
1111 }
1112
1113 if (first) {
1114 int nr = compound ? hpage_nr_pages(page) : 1;
1115 /*
1116 * We use the irq-unsafe __{inc|mod}_zone_page_stat because
1117 * these counters are not modified in interrupt context, and
1118 * pte lock(a spinlock) is held, which implies preemption
1119 * disabled.
1120 */
1121 if (compound)
1122 __inc_node_page_state(page, NR_ANON_THPS);
1123 __mod_node_page_state(page_pgdat(page), NR_ANON_MAPPED, nr);
1124 }
1125 if (unlikely(PageKsm(page)))
1126 return;
1127
1128 VM_BUG_ON_PAGE(!PageLocked(page), page);
1129
1130 /* address might be in next vma when migration races vma_adjust */
1131 if (first)
1132 __page_set_anon_rmap(page, vma, address,
1133 flags & RMAP_EXCLUSIVE);
1134 else
1135 __page_check_anon_rmap(page, vma, address);
1136}
1137
1138/**
1139 * page_add_new_anon_rmap - add pte mapping to a new anonymous page
1140 * @page: the page to add the mapping to
1141 * @vma: the vm area in which the mapping is added
1142 * @address: the user virtual address mapped
1143 * @compound: charge the page as compound or small page
1144 *
1145 * Same as page_add_anon_rmap but must only be called on *new* pages.
1146 * This means the inc-and-test can be bypassed.
1147 * Page does not have to be locked.
1148 */
1149void page_add_new_anon_rmap(struct page *page,
1150 struct vm_area_struct *vma, unsigned long address, bool compound)
1151{
1152 int nr = compound ? hpage_nr_pages(page) : 1;
1153
1154 VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
1155 __SetPageSwapBacked(page);
1156 if (compound) {
1157 VM_BUG_ON_PAGE(!PageTransHuge(page), page);
1158 /* increment count (starts at -1) */
1159 atomic_set(compound_mapcount_ptr(page), 0);
1160 __inc_node_page_state(page, NR_ANON_THPS);
1161 } else {
1162 /* Anon THP always mapped first with PMD */
1163 VM_BUG_ON_PAGE(PageTransCompound(page), page);
1164 /* increment count (starts at -1) */
1165 atomic_set(&page->_mapcount, 0);
1166 }
1167 __mod_node_page_state(page_pgdat(page), NR_ANON_MAPPED, nr);
1168 __page_set_anon_rmap(page, vma, address, 1);
1169}
1170
1171/**
1172 * page_add_file_rmap - add pte mapping to a file page
1173 * @page: the page to add the mapping to
1174 * @compound: charge the page as compound or small page
1175 *
1176 * The caller needs to hold the pte lock.
1177 */
1178void page_add_file_rmap(struct page *page, bool compound)
1179{
1180 int i, nr = 1;
1181
1182 VM_BUG_ON_PAGE(compound && !PageTransHuge(page), page);
1183 lock_page_memcg(page);
1184 if (compound && PageTransHuge(page)) {
1185 for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) {
1186 if (atomic_inc_and_test(&page[i]._mapcount))
1187 nr++;
1188 }
1189 if (!atomic_inc_and_test(compound_mapcount_ptr(page)))
1190 goto out;
1191 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
1192 __inc_node_page_state(page, NR_SHMEM_PMDMAPPED);
1193 } else {
1194 if (PageTransCompound(page) && page_mapping(page)) {
1195 VM_WARN_ON_ONCE(!PageLocked(page));
1196
1197 SetPageDoubleMap(compound_head(page));
1198 if (PageMlocked(page))
1199 clear_page_mlock(compound_head(page));
1200 }
1201 if (!atomic_inc_and_test(&page->_mapcount))
1202 goto out;
1203 }
1204 __mod_lruvec_page_state(page, NR_FILE_MAPPED, nr);
1205out:
1206 unlock_page_memcg(page);
1207}
1208
1209static void page_remove_file_rmap(struct page *page, bool compound)
1210{
1211 int i, nr = 1;
1212
1213 VM_BUG_ON_PAGE(compound && !PageHead(page), page);
1214 lock_page_memcg(page);
1215
1216 /* Hugepages are not counted in NR_FILE_MAPPED for now. */
1217 if (unlikely(PageHuge(page))) {
1218 /* hugetlb pages are always mapped with pmds */
1219 atomic_dec(compound_mapcount_ptr(page));
1220 goto out;
1221 }
1222
1223 /* page still mapped by someone else? */
1224 if (compound && PageTransHuge(page)) {
1225 for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) {
1226 if (atomic_add_negative(-1, &page[i]._mapcount))
1227 nr++;
1228 }
1229 if (!atomic_add_negative(-1, compound_mapcount_ptr(page)))
1230 goto out;
1231 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
1232 __dec_node_page_state(page, NR_SHMEM_PMDMAPPED);
1233 } else {
1234 if (!atomic_add_negative(-1, &page->_mapcount))
1235 goto out;
1236 }
1237
1238 /*
1239 * We use the irq-unsafe __{inc|mod}_lruvec_page_state because
1240 * these counters are not modified in interrupt context, and
1241 * pte lock(a spinlock) is held, which implies preemption disabled.
1242 */
1243 __mod_lruvec_page_state(page, NR_FILE_MAPPED, -nr);
1244
1245 if (unlikely(PageMlocked(page)))
1246 clear_page_mlock(page);
1247out:
1248 unlock_page_memcg(page);
1249}
1250
1251static void page_remove_anon_compound_rmap(struct page *page)
1252{
1253 int i, nr;
1254
1255 if (!atomic_add_negative(-1, compound_mapcount_ptr(page)))
1256 return;
1257
1258 /* Hugepages are not counted in NR_ANON_PAGES for now. */
1259 if (unlikely(PageHuge(page)))
1260 return;
1261
1262 if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
1263 return;
1264
1265 __dec_node_page_state(page, NR_ANON_THPS);
1266
1267 if (TestClearPageDoubleMap(page)) {
1268 /*
1269 * Subpages can be mapped with PTEs too. Check how many of
1270 * themi are still mapped.
1271 */
1272 for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) {
1273 if (atomic_add_negative(-1, &page[i]._mapcount))
1274 nr++;
1275 }
1276 } else {
1277 nr = HPAGE_PMD_NR;
1278 }
1279
1280 if (unlikely(PageMlocked(page)))
1281 clear_page_mlock(page);
1282
1283 if (nr) {
1284 __mod_node_page_state(page_pgdat(page), NR_ANON_MAPPED, -nr);
1285 deferred_split_huge_page(page);
1286 }
1287}
1288
1289/**
1290 * page_remove_rmap - take down pte mapping from a page
1291 * @page: page to remove mapping from
1292 * @compound: uncharge the page as compound or small page
1293 *
1294 * The caller needs to hold the pte lock.
1295 */
1296void page_remove_rmap(struct page *page, bool compound)
1297{
1298 if (!PageAnon(page))
1299 return page_remove_file_rmap(page, compound);
1300
1301 if (compound)
1302 return page_remove_anon_compound_rmap(page);
1303
1304 /* page still mapped by someone else? */
1305 if (!atomic_add_negative(-1, &page->_mapcount))
1306 return;
1307
1308 /*
1309 * We use the irq-unsafe __{inc|mod}_zone_page_stat because
1310 * these counters are not modified in interrupt context, and
1311 * pte lock(a spinlock) is held, which implies preemption disabled.
1312 */
1313 __dec_node_page_state(page, NR_ANON_MAPPED);
1314
1315 if (unlikely(PageMlocked(page)))
1316 clear_page_mlock(page);
1317
1318 if (PageTransCompound(page))
1319 deferred_split_huge_page(compound_head(page));
1320
1321 /*
1322 * It would be tidy to reset the PageAnon mapping here,
1323 * but that might overwrite a racing page_add_anon_rmap
1324 * which increments mapcount after us but sets mapping
1325 * before us: so leave the reset to free_unref_page,
1326 * and remember that it's only reliable while mapped.
1327 * Leaving it set also helps swapoff to reinstate ptes
1328 * faster for those pages still in swapcache.
1329 */
1330}
1331
1332/*
1333 * @arg: enum ttu_flags will be passed to this argument
1334 */
1335static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
1336 unsigned long address, void *arg)
1337{
1338 struct mm_struct *mm = vma->vm_mm;
1339 struct page_vma_mapped_walk pvmw = {
1340 .page = page,
1341 .vma = vma,
1342 .address = address,
1343 };
1344 pte_t pteval;
1345 struct page *subpage;
1346 bool ret = true;
1347 unsigned long start = address, end;
1348 enum ttu_flags flags = (enum ttu_flags)arg;
1349
1350 /* munlock has nothing to gain from examining un-locked vmas */
1351 if ((flags & TTU_MUNLOCK) && !(vma->vm_flags & VM_LOCKED))
1352 return true;
1353
1354 if (IS_ENABLED(CONFIG_MIGRATION) && (flags & TTU_MIGRATION) &&
1355 is_zone_device_page(page) && !is_device_private_page(page))
1356 return true;
1357
1358 if (flags & TTU_SPLIT_HUGE_PMD) {
1359 split_huge_pmd_address(vma, address,
1360 flags & TTU_SPLIT_FREEZE, page);
1361 }
1362
1363 /*
1364 * We have to assume the worse case ie pmd for invalidation. Note that
1365 * the page can not be free in this function as call of try_to_unmap()
1366 * must hold a reference on the page.
1367 */
1368 end = min(vma->vm_end, start + (PAGE_SIZE << compound_order(page)));
1369 mmu_notifier_invalidate_range_start(vma->vm_mm, start, end);
1370
1371 while (page_vma_mapped_walk(&pvmw)) {
1372#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1373 /* PMD-mapped THP migration entry */
1374 if (!pvmw.pte && (flags & TTU_MIGRATION)) {
1375 VM_BUG_ON_PAGE(PageHuge(page) || !PageTransCompound(page), page);
1376
1377 set_pmd_migration_entry(&pvmw, page);
1378 continue;
1379 }
1380#endif
1381
1382 /*
1383 * If the page is mlock()d, we cannot swap it out.
1384 * If it's recently referenced (perhaps page_referenced
1385 * skipped over this mm) then we should reactivate it.
1386 */
1387 if (!(flags & TTU_IGNORE_MLOCK)) {
1388 if (vma->vm_flags & VM_LOCKED) {
1389 /* PTE-mapped THP are never mlocked */
1390 if (!PageTransCompound(page)) {
1391 /*
1392 * Holding pte lock, we do *not* need
1393 * mmap_sem here
1394 */
1395 mlock_vma_page(page);
1396 }
1397 ret = false;
1398 page_vma_mapped_walk_done(&pvmw);
1399 break;
1400 }
1401 if (flags & TTU_MUNLOCK)
1402 continue;
1403 }
1404
1405 /* Unexpected PMD-mapped THP? */
1406 VM_BUG_ON_PAGE(!pvmw.pte, page);
1407
1408 subpage = page - page_to_pfn(page) + pte_pfn(*pvmw.pte);
1409 address = pvmw.address;
1410
1411
1412 if (IS_ENABLED(CONFIG_MIGRATION) &&
1413 (flags & TTU_MIGRATION) &&
1414 is_zone_device_page(page)) {
1415 swp_entry_t entry;
1416 pte_t swp_pte;
1417
1418 pteval = ptep_get_and_clear(mm, pvmw.address, pvmw.pte);
1419
1420 /*
1421 * Store the pfn of the page in a special migration
1422 * pte. do_swap_page() will wait until the migration
1423 * pte is removed and then restart fault handling.
1424 */
1425 entry = make_migration_entry(page, 0);
1426 swp_pte = swp_entry_to_pte(entry);
1427 if (pte_soft_dirty(pteval))
1428 swp_pte = pte_swp_mksoft_dirty(swp_pte);
1429 set_pte_at(mm, pvmw.address, pvmw.pte, swp_pte);
1430 /*
1431 * No need to invalidate here it will synchronize on
1432 * against the special swap migration pte.
1433 */
1434 goto discard;
1435 }
1436
1437 if (!(flags & TTU_IGNORE_ACCESS)) {
1438 if (ptep_clear_flush_young_notify(vma, address,
1439 pvmw.pte)) {
1440 ret = false;
1441 page_vma_mapped_walk_done(&pvmw);
1442 break;
1443 }
1444 }
1445
1446 /* Nuke the page table entry. */
1447 flush_cache_page(vma, address, pte_pfn(*pvmw.pte));
1448 if (should_defer_flush(mm, flags)) {
1449 /*
1450 * We clear the PTE but do not flush so potentially
1451 * a remote CPU could still be writing to the page.
1452 * If the entry was previously clean then the
1453 * architecture must guarantee that a clear->dirty
1454 * transition on a cached TLB entry is written through
1455 * and traps if the PTE is unmapped.
1456 */
1457 pteval = ptep_get_and_clear(mm, address, pvmw.pte);
1458
1459 set_tlb_ubc_flush_pending(mm, pte_dirty(pteval));
1460 } else {
1461 pteval = ptep_clear_flush(vma, address, pvmw.pte);
1462 }
1463
1464 /* Move the dirty bit to the page. Now the pte is gone. */
1465 if (pte_dirty(pteval))
1466 set_page_dirty(page);
1467
1468 /* Update high watermark before we lower rss */
1469 update_hiwater_rss(mm);
1470
1471 if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
1472 pteval = swp_entry_to_pte(make_hwpoison_entry(subpage));
1473 if (PageHuge(page)) {
1474 int nr = 1 << compound_order(page);
1475 hugetlb_count_sub(nr, mm);
1476 set_huge_swap_pte_at(mm, address,
1477 pvmw.pte, pteval,
1478 vma_mmu_pagesize(vma));
1479 } else {
1480 dec_mm_counter(mm, mm_counter(page));
1481 set_pte_at(mm, address, pvmw.pte, pteval);
1482 }
1483
1484 } else if (pte_unused(pteval)) {
1485 /*
1486 * The guest indicated that the page content is of no
1487 * interest anymore. Simply discard the pte, vmscan
1488 * will take care of the rest.
1489 */
1490 dec_mm_counter(mm, mm_counter(page));
1491 /* We have to invalidate as we cleared the pte */
1492 mmu_notifier_invalidate_range(mm, address,
1493 address + PAGE_SIZE);
1494 } else if (IS_ENABLED(CONFIG_MIGRATION) &&
1495 (flags & (TTU_MIGRATION|TTU_SPLIT_FREEZE))) {
1496 swp_entry_t entry;
1497 pte_t swp_pte;
1498
1499 if (arch_unmap_one(mm, vma, address, pteval) < 0) {
1500 set_pte_at(mm, address, pvmw.pte, pteval);
1501 ret = false;
1502 page_vma_mapped_walk_done(&pvmw);
1503 break;
1504 }
1505
1506 /*
1507 * Store the pfn of the page in a special migration
1508 * pte. do_swap_page() will wait until the migration
1509 * pte is removed and then restart fault handling.
1510 */
1511 entry = make_migration_entry(subpage,
1512 pte_write(pteval));
1513 swp_pte = swp_entry_to_pte(entry);
1514 if (pte_soft_dirty(pteval))
1515 swp_pte = pte_swp_mksoft_dirty(swp_pte);
1516 set_pte_at(mm, address, pvmw.pte, swp_pte);
1517 /*
1518 * No need to invalidate here it will synchronize on
1519 * against the special swap migration pte.
1520 */
1521 } else if (PageAnon(page)) {
1522 swp_entry_t entry = { .val = page_private(subpage) };
1523 pte_t swp_pte;
1524 /*
1525 * Store the swap location in the pte.
1526 * See handle_pte_fault() ...
1527 */
1528 if (unlikely(PageSwapBacked(page) != PageSwapCache(page))) {
1529 WARN_ON_ONCE(1);
1530 ret = false;
1531 /* We have to invalidate as we cleared the pte */
1532 mmu_notifier_invalidate_range(mm, address,
1533 address + PAGE_SIZE);
1534 page_vma_mapped_walk_done(&pvmw);
1535 break;
1536 }
1537
1538 /* MADV_FREE page check */
1539 if (!PageSwapBacked(page)) {
1540 if (!PageDirty(page)) {
1541 /* Invalidate as we cleared the pte */
1542 mmu_notifier_invalidate_range(mm,
1543 address, address + PAGE_SIZE);
1544 dec_mm_counter(mm, MM_ANONPAGES);
1545 goto discard;
1546 }
1547
1548 /*
1549 * If the page was redirtied, it cannot be
1550 * discarded. Remap the page to page table.
1551 */
1552 set_pte_at(mm, address, pvmw.pte, pteval);
1553 SetPageSwapBacked(page);
1554 ret = false;
1555 page_vma_mapped_walk_done(&pvmw);
1556 break;
1557 }
1558
1559 if (swap_duplicate(entry) < 0) {
1560 set_pte_at(mm, address, pvmw.pte, pteval);
1561 ret = false;
1562 page_vma_mapped_walk_done(&pvmw);
1563 break;
1564 }
1565 if (arch_unmap_one(mm, vma, address, pteval) < 0) {
1566 set_pte_at(mm, address, pvmw.pte, pteval);
1567 ret = false;
1568 page_vma_mapped_walk_done(&pvmw);
1569 break;
1570 }
1571 if (list_empty(&mm->mmlist)) {
1572 spin_lock(&mmlist_lock);
1573 if (list_empty(&mm->mmlist))
1574 list_add(&mm->mmlist, &init_mm.mmlist);
1575 spin_unlock(&mmlist_lock);
1576 }
1577 dec_mm_counter(mm, MM_ANONPAGES);
1578 inc_mm_counter(mm, MM_SWAPENTS);
1579 swp_pte = swp_entry_to_pte(entry);
1580 if (pte_soft_dirty(pteval))
1581 swp_pte = pte_swp_mksoft_dirty(swp_pte);
1582 set_pte_at(mm, address, pvmw.pte, swp_pte);
1583 /* Invalidate as we cleared the pte */
1584 mmu_notifier_invalidate_range(mm, address,
1585 address + PAGE_SIZE);
1586 } else {
1587 /*
1588 * We should not need to notify here as we reach this
1589 * case only from freeze_page() itself only call from
1590 * split_huge_page_to_list() so everything below must
1591 * be true:
1592 * - page is not anonymous
1593 * - page is locked
1594 *
1595 * So as it is a locked file back page thus it can not
1596 * be remove from the page cache and replace by a new
1597 * page before mmu_notifier_invalidate_range_end so no
1598 * concurrent thread might update its page table to
1599 * point at new page while a device still is using this
1600 * page.
1601 *
1602 * See Documentation/vm/mmu_notifier.txt
1603 */
1604 dec_mm_counter(mm, mm_counter_file(page));
1605 }
1606discard:
1607 /*
1608 * No need to call mmu_notifier_invalidate_range() it has be
1609 * done above for all cases requiring it to happen under page
1610 * table lock before mmu_notifier_invalidate_range_end()
1611 *
1612 * See Documentation/vm/mmu_notifier.txt
1613 */
1614 page_remove_rmap(subpage, PageHuge(page));
1615 put_page(page);
1616 }
1617
1618 mmu_notifier_invalidate_range_end(vma->vm_mm, start, end);
1619
1620 return ret;
1621}
1622
1623bool is_vma_temporary_stack(struct vm_area_struct *vma)
1624{
1625 int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP);
1626
1627 if (!maybe_stack)
1628 return false;
1629
1630 if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) ==
1631 VM_STACK_INCOMPLETE_SETUP)
1632 return true;
1633
1634 return false;
1635}
1636
1637static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg)
1638{
1639 return is_vma_temporary_stack(vma);
1640}
1641
1642static int page_mapcount_is_zero(struct page *page)
1643{
1644 return !total_mapcount(page);
1645}
1646
1647/**
1648 * try_to_unmap - try to remove all page table mappings to a page
1649 * @page: the page to get unmapped
1650 * @flags: action and flags
1651 *
1652 * Tries to remove all the page table entries which are mapping this
1653 * page, used in the pageout path. Caller must hold the page lock.
1654 *
1655 * If unmap is successful, return true. Otherwise, false.
1656 */
1657bool try_to_unmap(struct page *page, enum ttu_flags flags)
1658{
1659 struct rmap_walk_control rwc = {
1660 .rmap_one = try_to_unmap_one,
1661 .arg = (void *)flags,
1662 .done = page_mapcount_is_zero,
1663 .anon_lock = page_lock_anon_vma_read,
1664 };
1665
1666 /*
1667 * During exec, a temporary VMA is setup and later moved.
1668 * The VMA is moved under the anon_vma lock but not the
1669 * page tables leading to a race where migration cannot
1670 * find the migration ptes. Rather than increasing the
1671 * locking requirements of exec(), migration skips
1672 * temporary VMAs until after exec() completes.
1673 */
1674 if ((flags & (TTU_MIGRATION|TTU_SPLIT_FREEZE))
1675 && !PageKsm(page) && PageAnon(page))
1676 rwc.invalid_vma = invalid_migration_vma;
1677
1678 if (flags & TTU_RMAP_LOCKED)
1679 rmap_walk_locked(page, &rwc);
1680 else
1681 rmap_walk(page, &rwc);
1682
1683 return !page_mapcount(page) ? true : false;
1684}
1685
1686static int page_not_mapped(struct page *page)
1687{
1688 return !page_mapped(page);
1689};
1690
1691/**
1692 * try_to_munlock - try to munlock a page
1693 * @page: the page to be munlocked
1694 *
1695 * Called from munlock code. Checks all of the VMAs mapping the page
1696 * to make sure nobody else has this page mlocked. The page will be
1697 * returned with PG_mlocked cleared if no other vmas have it mlocked.
1698 */
1699
1700void try_to_munlock(struct page *page)
1701{
1702 struct rmap_walk_control rwc = {
1703 .rmap_one = try_to_unmap_one,
1704 .arg = (void *)TTU_MUNLOCK,
1705 .done = page_not_mapped,
1706 .anon_lock = page_lock_anon_vma_read,
1707
1708 };
1709
1710 VM_BUG_ON_PAGE(!PageLocked(page) || PageLRU(page), page);
1711 VM_BUG_ON_PAGE(PageCompound(page) && PageDoubleMap(page), page);
1712
1713 rmap_walk(page, &rwc);
1714}
1715
1716void __put_anon_vma(struct anon_vma *anon_vma)
1717{
1718 struct anon_vma *root = anon_vma->root;
1719
1720 anon_vma_free(anon_vma);
1721 if (root != anon_vma && atomic_dec_and_test(&root->refcount))
1722 anon_vma_free(root);
1723}
1724
1725static struct anon_vma *rmap_walk_anon_lock(struct page *page,
1726 struct rmap_walk_control *rwc)
1727{
1728 struct anon_vma *anon_vma;
1729
1730 if (rwc->anon_lock)
1731 return rwc->anon_lock(page);
1732
1733 /*
1734 * Note: remove_migration_ptes() cannot use page_lock_anon_vma_read()
1735 * because that depends on page_mapped(); but not all its usages
1736 * are holding mmap_sem. Users without mmap_sem are required to
1737 * take a reference count to prevent the anon_vma disappearing
1738 */
1739 anon_vma = page_anon_vma(page);
1740 if (!anon_vma)
1741 return NULL;
1742
1743 anon_vma_lock_read(anon_vma);
1744 return anon_vma;
1745}
1746
1747/*
1748 * rmap_walk_anon - do something to anonymous page using the object-based
1749 * rmap method
1750 * @page: the page to be handled
1751 * @rwc: control variable according to each walk type
1752 *
1753 * Find all the mappings of a page using the mapping pointer and the vma chains
1754 * contained in the anon_vma struct it points to.
1755 *
1756 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1757 * where the page was found will be held for write. So, we won't recheck
1758 * vm_flags for that VMA. That should be OK, because that vma shouldn't be
1759 * LOCKED.
1760 */
1761static void rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc,
1762 bool locked)
1763{
1764 struct anon_vma *anon_vma;
1765 pgoff_t pgoff_start, pgoff_end;
1766 struct anon_vma_chain *avc;
1767
1768 if (locked) {
1769 anon_vma = page_anon_vma(page);
1770 /* anon_vma disappear under us? */
1771 VM_BUG_ON_PAGE(!anon_vma, page);
1772 } else {
1773 anon_vma = rmap_walk_anon_lock(page, rwc);
1774 }
1775 if (!anon_vma)
1776 return;
1777
1778 pgoff_start = page_to_pgoff(page);
1779 pgoff_end = pgoff_start + hpage_nr_pages(page) - 1;
1780 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root,
1781 pgoff_start, pgoff_end) {
1782 struct vm_area_struct *vma = avc->vma;
1783 unsigned long address = vma_address(page, vma);
1784
1785 cond_resched();
1786
1787 if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
1788 continue;
1789
1790 if (!rwc->rmap_one(page, vma, address, rwc->arg))
1791 break;
1792 if (rwc->done && rwc->done(page))
1793 break;
1794 }
1795
1796 if (!locked)
1797 anon_vma_unlock_read(anon_vma);
1798}
1799
1800/*
1801 * rmap_walk_file - do something to file page using the object-based rmap method
1802 * @page: the page to be handled
1803 * @rwc: control variable according to each walk type
1804 *
1805 * Find all the mappings of a page using the mapping pointer and the vma chains
1806 * contained in the address_space struct it points to.
1807 *
1808 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1809 * where the page was found will be held for write. So, we won't recheck
1810 * vm_flags for that VMA. That should be OK, because that vma shouldn't be
1811 * LOCKED.
1812 */
1813static void rmap_walk_file(struct page *page, struct rmap_walk_control *rwc,
1814 bool locked)
1815{
1816 struct address_space *mapping = page_mapping(page);
1817 pgoff_t pgoff_start, pgoff_end;
1818 struct vm_area_struct *vma;
1819
1820 /*
1821 * The page lock not only makes sure that page->mapping cannot
1822 * suddenly be NULLified by truncation, it makes sure that the
1823 * structure at mapping cannot be freed and reused yet,
1824 * so we can safely take mapping->i_mmap_rwsem.
1825 */
1826 VM_BUG_ON_PAGE(!PageLocked(page), page);
1827
1828 if (!mapping)
1829 return;
1830
1831 pgoff_start = page_to_pgoff(page);
1832 pgoff_end = pgoff_start + hpage_nr_pages(page) - 1;
1833 if (!locked)
1834 i_mmap_lock_read(mapping);
1835 vma_interval_tree_foreach(vma, &mapping->i_mmap,
1836 pgoff_start, pgoff_end) {
1837 unsigned long address = vma_address(page, vma);
1838
1839 cond_resched();
1840
1841 if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
1842 continue;
1843
1844 if (!rwc->rmap_one(page, vma, address, rwc->arg))
1845 goto done;
1846 if (rwc->done && rwc->done(page))
1847 goto done;
1848 }
1849
1850done:
1851 if (!locked)
1852 i_mmap_unlock_read(mapping);
1853}
1854
1855void rmap_walk(struct page *page, struct rmap_walk_control *rwc)
1856{
1857 if (unlikely(PageKsm(page)))
1858 rmap_walk_ksm(page, rwc);
1859 else if (PageAnon(page))
1860 rmap_walk_anon(page, rwc, false);
1861 else
1862 rmap_walk_file(page, rwc, false);
1863}
1864
1865/* Like rmap_walk, but caller holds relevant rmap lock */
1866void rmap_walk_locked(struct page *page, struct rmap_walk_control *rwc)
1867{
1868 /* no ksm support for now */
1869 VM_BUG_ON_PAGE(PageKsm(page), page);
1870 if (PageAnon(page))
1871 rmap_walk_anon(page, rwc, true);
1872 else
1873 rmap_walk_file(page, rwc, true);
1874}
1875
1876#ifdef CONFIG_HUGETLB_PAGE
1877/*
1878 * The following three functions are for anonymous (private mapped) hugepages.
1879 * Unlike common anonymous pages, anonymous hugepages have no accounting code
1880 * and no lru code, because we handle hugepages differently from common pages.
1881 */
1882static void __hugepage_set_anon_rmap(struct page *page,
1883 struct vm_area_struct *vma, unsigned long address, int exclusive)
1884{
1885 struct anon_vma *anon_vma = vma->anon_vma;
1886
1887 BUG_ON(!anon_vma);
1888
1889 if (PageAnon(page))
1890 return;
1891 if (!exclusive)
1892 anon_vma = anon_vma->root;
1893
1894 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1895 page->mapping = (struct address_space *) anon_vma;
1896 page->index = linear_page_index(vma, address);
1897}
1898
1899void hugepage_add_anon_rmap(struct page *page,
1900 struct vm_area_struct *vma, unsigned long address)
1901{
1902 struct anon_vma *anon_vma = vma->anon_vma;
1903 int first;
1904
1905 BUG_ON(!PageLocked(page));
1906 BUG_ON(!anon_vma);
1907 /* address might be in next vma when migration races vma_adjust */
1908 first = atomic_inc_and_test(compound_mapcount_ptr(page));
1909 if (first)
1910 __hugepage_set_anon_rmap(page, vma, address, 0);
1911}
1912
1913void hugepage_add_new_anon_rmap(struct page *page,
1914 struct vm_area_struct *vma, unsigned long address)
1915{
1916 BUG_ON(address < vma->vm_start || address >= vma->vm_end);
1917 atomic_set(compound_mapcount_ptr(page), 0);
1918 __hugepage_set_anon_rmap(page, vma, address, 1);
1919}
1920#endif /* CONFIG_HUGETLB_PAGE */