]> git.proxmox.com Git - mirror_ubuntu-zesty-kernel.git/blob - mm/rmap.c
mm/slub.c: run free_partial() outside of the kmem_cache_node->list_lock
[mirror_ubuntu-zesty-kernel.git] / mm / rmap.c
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
71 static struct kmem_cache *anon_vma_cachep;
72 static struct kmem_cache *anon_vma_chain_cachep;
73
74 static 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
93 static 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
123 static 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
128 static 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
133 static 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 */
170 int 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 */
228 static 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
240 static 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 */
258 int 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 */
312 int 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
373 void 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 VM_WARN_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
420 static 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
429 void __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 */
461 struct 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 }
491 out:
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 */
504 struct 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
561 out:
562 rcu_read_unlock();
563 return anon_vma;
564 }
565
566 void 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 */
578 void try_to_unmap_flush(void)
579 {
580 struct tlbflush_unmap_batch *tlb_ubc = &current->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 */
603 void try_to_unmap_flush_dirty(void)
604 {
605 struct tlbflush_unmap_batch *tlb_ubc = &current->tlb_ubc;
606
607 if (tlb_ubc->writable)
608 try_to_unmap_flush();
609 }
610
611 static void set_tlb_ubc_flush_pending(struct mm_struct *mm,
612 struct page *page, bool writable)
613 {
614 struct tlbflush_unmap_batch *tlb_ubc = &current->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 */
632 static 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
647 static void set_tlb_ubc_flush_pending(struct mm_struct *mm,
648 struct page *page, bool writable)
649 {
650 }
651
652 static 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 */
662 unsigned 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
685 pmd_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;
710 out:
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 */
723 pte_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);
752 check:
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 */
771 int 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 */
796 bool 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;
839 unlock_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 }
849 map_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);
857 check_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 }
870 found:
871 *ptep = pte;
872 *pmdp = pmd;
873 *ptlp = ptl;
874 return true;
875 }
876 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
877
878 struct 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 */
887 static 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
947 static 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 */
968 int 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
1016 static 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 }
1046 out:
1047 return SWAP_AGAIN;
1048 }
1049
1050 static 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
1058 int 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 }
1081 EXPORT_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 *
1088 * When a page belongs exclusively to one process after a COW event,
1089 * that page can be moved into the anon_vma that belongs to just that
1090 * process, so the rmap code will not search the parent or sibling
1091 * processes.
1092 */
1093 void page_move_anon_rmap(struct page *page, struct vm_area_struct *vma)
1094 {
1095 struct anon_vma *anon_vma = vma->anon_vma;
1096
1097 page = compound_head(page);
1098
1099 VM_BUG_ON_PAGE(!PageLocked(page), page);
1100 VM_BUG_ON_VMA(!anon_vma, vma);
1101
1102 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1103 /*
1104 * Ensure that anon_vma and the PAGE_MAPPING_ANON bit are written
1105 * simultaneously, so a concurrent reader (eg page_referenced()'s
1106 * PageAnon()) will not see one without the other.
1107 */
1108 WRITE_ONCE(page->mapping, (struct address_space *) anon_vma);
1109 }
1110
1111 /**
1112 * __page_set_anon_rmap - set up new anonymous rmap
1113 * @page: Page to add to rmap
1114 * @vma: VM area to add page to.
1115 * @address: User virtual address of the mapping
1116 * @exclusive: the page is exclusively owned by the current process
1117 */
1118 static void __page_set_anon_rmap(struct page *page,
1119 struct vm_area_struct *vma, unsigned long address, int exclusive)
1120 {
1121 struct anon_vma *anon_vma = vma->anon_vma;
1122
1123 BUG_ON(!anon_vma);
1124
1125 if (PageAnon(page))
1126 return;
1127
1128 /*
1129 * If the page isn't exclusively mapped into this vma,
1130 * we must use the _oldest_ possible anon_vma for the
1131 * page mapping!
1132 */
1133 if (!exclusive)
1134 anon_vma = anon_vma->root;
1135
1136 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1137 page->mapping = (struct address_space *) anon_vma;
1138 page->index = linear_page_index(vma, address);
1139 }
1140
1141 /**
1142 * __page_check_anon_rmap - sanity check anonymous rmap addition
1143 * @page: the page to add the mapping to
1144 * @vma: the vm area in which the mapping is added
1145 * @address: the user virtual address mapped
1146 */
1147 static void __page_check_anon_rmap(struct page *page,
1148 struct vm_area_struct *vma, unsigned long address)
1149 {
1150 #ifdef CONFIG_DEBUG_VM
1151 /*
1152 * The page's anon-rmap details (mapping and index) are guaranteed to
1153 * be set up correctly at this point.
1154 *
1155 * We have exclusion against page_add_anon_rmap because the caller
1156 * always holds the page locked, except if called from page_dup_rmap,
1157 * in which case the page is already known to be setup.
1158 *
1159 * We have exclusion against page_add_new_anon_rmap because those pages
1160 * are initially only visible via the pagetables, and the pte is locked
1161 * over the call to page_add_new_anon_rmap.
1162 */
1163 BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root);
1164 BUG_ON(page_to_pgoff(page) != linear_page_index(vma, address));
1165 #endif
1166 }
1167
1168 /**
1169 * page_add_anon_rmap - add pte mapping to an anonymous page
1170 * @page: the page to add the mapping to
1171 * @vma: the vm area in which the mapping is added
1172 * @address: the user virtual address mapped
1173 * @compound: charge the page as compound or small page
1174 *
1175 * The caller needs to hold the pte lock, and the page must be locked in
1176 * the anon_vma case: to serialize mapping,index checking after setting,
1177 * and to ensure that PageAnon is not being upgraded racily to PageKsm
1178 * (but PageKsm is never downgraded to PageAnon).
1179 */
1180 void page_add_anon_rmap(struct page *page,
1181 struct vm_area_struct *vma, unsigned long address, bool compound)
1182 {
1183 do_page_add_anon_rmap(page, vma, address, compound ? RMAP_COMPOUND : 0);
1184 }
1185
1186 /*
1187 * Special version of the above for do_swap_page, which often runs
1188 * into pages that are exclusively owned by the current process.
1189 * Everybody else should continue to use page_add_anon_rmap above.
1190 */
1191 void do_page_add_anon_rmap(struct page *page,
1192 struct vm_area_struct *vma, unsigned long address, int flags)
1193 {
1194 bool compound = flags & RMAP_COMPOUND;
1195 bool first;
1196
1197 if (compound) {
1198 atomic_t *mapcount;
1199 VM_BUG_ON_PAGE(!PageLocked(page), page);
1200 VM_BUG_ON_PAGE(!PageTransHuge(page), page);
1201 mapcount = compound_mapcount_ptr(page);
1202 first = atomic_inc_and_test(mapcount);
1203 } else {
1204 first = atomic_inc_and_test(&page->_mapcount);
1205 }
1206
1207 if (first) {
1208 int nr = compound ? hpage_nr_pages(page) : 1;
1209 /*
1210 * We use the irq-unsafe __{inc|mod}_zone_page_stat because
1211 * these counters are not modified in interrupt context, and
1212 * pte lock(a spinlock) is held, which implies preemption
1213 * disabled.
1214 */
1215 if (compound)
1216 __inc_node_page_state(page, NR_ANON_THPS);
1217 __mod_node_page_state(page_pgdat(page), NR_ANON_MAPPED, nr);
1218 }
1219 if (unlikely(PageKsm(page)))
1220 return;
1221
1222 VM_BUG_ON_PAGE(!PageLocked(page), page);
1223
1224 /* address might be in next vma when migration races vma_adjust */
1225 if (first)
1226 __page_set_anon_rmap(page, vma, address,
1227 flags & RMAP_EXCLUSIVE);
1228 else
1229 __page_check_anon_rmap(page, vma, address);
1230 }
1231
1232 /**
1233 * page_add_new_anon_rmap - add pte mapping to a new anonymous page
1234 * @page: the page to add the mapping to
1235 * @vma: the vm area in which the mapping is added
1236 * @address: the user virtual address mapped
1237 * @compound: charge the page as compound or small page
1238 *
1239 * Same as page_add_anon_rmap but must only be called on *new* pages.
1240 * This means the inc-and-test can be bypassed.
1241 * Page does not have to be locked.
1242 */
1243 void page_add_new_anon_rmap(struct page *page,
1244 struct vm_area_struct *vma, unsigned long address, bool compound)
1245 {
1246 int nr = compound ? hpage_nr_pages(page) : 1;
1247
1248 VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
1249 __SetPageSwapBacked(page);
1250 if (compound) {
1251 VM_BUG_ON_PAGE(!PageTransHuge(page), page);
1252 /* increment count (starts at -1) */
1253 atomic_set(compound_mapcount_ptr(page), 0);
1254 __inc_node_page_state(page, NR_ANON_THPS);
1255 } else {
1256 /* Anon THP always mapped first with PMD */
1257 VM_BUG_ON_PAGE(PageTransCompound(page), page);
1258 /* increment count (starts at -1) */
1259 atomic_set(&page->_mapcount, 0);
1260 }
1261 __mod_node_page_state(page_pgdat(page), NR_ANON_MAPPED, nr);
1262 __page_set_anon_rmap(page, vma, address, 1);
1263 }
1264
1265 /**
1266 * page_add_file_rmap - add pte mapping to a file page
1267 * @page: the page to add the mapping to
1268 *
1269 * The caller needs to hold the pte lock.
1270 */
1271 void page_add_file_rmap(struct page *page, bool compound)
1272 {
1273 int i, nr = 1;
1274
1275 VM_BUG_ON_PAGE(compound && !PageTransHuge(page), page);
1276 lock_page_memcg(page);
1277 if (compound && PageTransHuge(page)) {
1278 for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) {
1279 if (atomic_inc_and_test(&page[i]._mapcount))
1280 nr++;
1281 }
1282 if (!atomic_inc_and_test(compound_mapcount_ptr(page)))
1283 goto out;
1284 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
1285 __inc_node_page_state(page, NR_SHMEM_PMDMAPPED);
1286 } else {
1287 if (PageTransCompound(page) && page_mapping(page)) {
1288 VM_WARN_ON_ONCE(!PageLocked(page));
1289
1290 SetPageDoubleMap(compound_head(page));
1291 if (PageMlocked(page))
1292 clear_page_mlock(compound_head(page));
1293 }
1294 if (!atomic_inc_and_test(&page->_mapcount))
1295 goto out;
1296 }
1297 __mod_node_page_state(page_pgdat(page), NR_FILE_MAPPED, nr);
1298 mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_FILE_MAPPED);
1299 out:
1300 unlock_page_memcg(page);
1301 }
1302
1303 static void page_remove_file_rmap(struct page *page, bool compound)
1304 {
1305 int i, nr = 1;
1306
1307 VM_BUG_ON_PAGE(compound && !PageHead(page), page);
1308 lock_page_memcg(page);
1309
1310 /* Hugepages are not counted in NR_FILE_MAPPED for now. */
1311 if (unlikely(PageHuge(page))) {
1312 /* hugetlb pages are always mapped with pmds */
1313 atomic_dec(compound_mapcount_ptr(page));
1314 goto out;
1315 }
1316
1317 /* page still mapped by someone else? */
1318 if (compound && PageTransHuge(page)) {
1319 for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) {
1320 if (atomic_add_negative(-1, &page[i]._mapcount))
1321 nr++;
1322 }
1323 if (!atomic_add_negative(-1, compound_mapcount_ptr(page)))
1324 goto out;
1325 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
1326 __dec_node_page_state(page, NR_SHMEM_PMDMAPPED);
1327 } else {
1328 if (!atomic_add_negative(-1, &page->_mapcount))
1329 goto out;
1330 }
1331
1332 /*
1333 * We use the irq-unsafe __{inc|mod}_zone_page_state because
1334 * these counters are not modified in interrupt context, and
1335 * pte lock(a spinlock) is held, which implies preemption disabled.
1336 */
1337 __mod_node_page_state(page_pgdat(page), NR_FILE_MAPPED, -nr);
1338 mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_FILE_MAPPED);
1339
1340 if (unlikely(PageMlocked(page)))
1341 clear_page_mlock(page);
1342 out:
1343 unlock_page_memcg(page);
1344 }
1345
1346 static void page_remove_anon_compound_rmap(struct page *page)
1347 {
1348 int i, nr;
1349
1350 if (!atomic_add_negative(-1, compound_mapcount_ptr(page)))
1351 return;
1352
1353 /* Hugepages are not counted in NR_ANON_PAGES for now. */
1354 if (unlikely(PageHuge(page)))
1355 return;
1356
1357 if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
1358 return;
1359
1360 __dec_node_page_state(page, NR_ANON_THPS);
1361
1362 if (TestClearPageDoubleMap(page)) {
1363 /*
1364 * Subpages can be mapped with PTEs too. Check how many of
1365 * themi are still mapped.
1366 */
1367 for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) {
1368 if (atomic_add_negative(-1, &page[i]._mapcount))
1369 nr++;
1370 }
1371 } else {
1372 nr = HPAGE_PMD_NR;
1373 }
1374
1375 if (unlikely(PageMlocked(page)))
1376 clear_page_mlock(page);
1377
1378 if (nr) {
1379 __mod_node_page_state(page_pgdat(page), NR_ANON_MAPPED, -nr);
1380 deferred_split_huge_page(page);
1381 }
1382 }
1383
1384 /**
1385 * page_remove_rmap - take down pte mapping from a page
1386 * @page: page to remove mapping from
1387 * @compound: uncharge the page as compound or small page
1388 *
1389 * The caller needs to hold the pte lock.
1390 */
1391 void page_remove_rmap(struct page *page, bool compound)
1392 {
1393 if (!PageAnon(page))
1394 return page_remove_file_rmap(page, compound);
1395
1396 if (compound)
1397 return page_remove_anon_compound_rmap(page);
1398
1399 /* page still mapped by someone else? */
1400 if (!atomic_add_negative(-1, &page->_mapcount))
1401 return;
1402
1403 /*
1404 * We use the irq-unsafe __{inc|mod}_zone_page_stat because
1405 * these counters are not modified in interrupt context, and
1406 * pte lock(a spinlock) is held, which implies preemption disabled.
1407 */
1408 __dec_node_page_state(page, NR_ANON_MAPPED);
1409
1410 if (unlikely(PageMlocked(page)))
1411 clear_page_mlock(page);
1412
1413 if (PageTransCompound(page))
1414 deferred_split_huge_page(compound_head(page));
1415
1416 /*
1417 * It would be tidy to reset the PageAnon mapping here,
1418 * but that might overwrite a racing page_add_anon_rmap
1419 * which increments mapcount after us but sets mapping
1420 * before us: so leave the reset to free_hot_cold_page,
1421 * and remember that it's only reliable while mapped.
1422 * Leaving it set also helps swapoff to reinstate ptes
1423 * faster for those pages still in swapcache.
1424 */
1425 }
1426
1427 struct rmap_private {
1428 enum ttu_flags flags;
1429 int lazyfreed;
1430 };
1431
1432 /*
1433 * @arg: enum ttu_flags will be passed to this argument
1434 */
1435 static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
1436 unsigned long address, void *arg)
1437 {
1438 struct mm_struct *mm = vma->vm_mm;
1439 pte_t *pte;
1440 pte_t pteval;
1441 spinlock_t *ptl;
1442 int ret = SWAP_AGAIN;
1443 struct rmap_private *rp = arg;
1444 enum ttu_flags flags = rp->flags;
1445
1446 /* munlock has nothing to gain from examining un-locked vmas */
1447 if ((flags & TTU_MUNLOCK) && !(vma->vm_flags & VM_LOCKED))
1448 goto out;
1449
1450 if (flags & TTU_SPLIT_HUGE_PMD) {
1451 split_huge_pmd_address(vma, address,
1452 flags & TTU_MIGRATION, page);
1453 /* check if we have anything to do after split */
1454 if (page_mapcount(page) == 0)
1455 goto out;
1456 }
1457
1458 pte = page_check_address(page, mm, address, &ptl,
1459 PageTransCompound(page));
1460 if (!pte)
1461 goto out;
1462
1463 /*
1464 * If the page is mlock()d, we cannot swap it out.
1465 * If it's recently referenced (perhaps page_referenced
1466 * skipped over this mm) then we should reactivate it.
1467 */
1468 if (!(flags & TTU_IGNORE_MLOCK)) {
1469 if (vma->vm_flags & VM_LOCKED) {
1470 /* PTE-mapped THP are never mlocked */
1471 if (!PageTransCompound(page)) {
1472 /*
1473 * Holding pte lock, we do *not* need
1474 * mmap_sem here
1475 */
1476 mlock_vma_page(page);
1477 }
1478 ret = SWAP_MLOCK;
1479 goto out_unmap;
1480 }
1481 if (flags & TTU_MUNLOCK)
1482 goto out_unmap;
1483 }
1484 if (!(flags & TTU_IGNORE_ACCESS)) {
1485 if (ptep_clear_flush_young_notify(vma, address, pte)) {
1486 ret = SWAP_FAIL;
1487 goto out_unmap;
1488 }
1489 }
1490
1491 /* Nuke the page table entry. */
1492 flush_cache_page(vma, address, page_to_pfn(page));
1493 if (should_defer_flush(mm, flags)) {
1494 /*
1495 * We clear the PTE but do not flush so potentially a remote
1496 * CPU could still be writing to the page. If the entry was
1497 * previously clean then the architecture must guarantee that
1498 * a clear->dirty transition on a cached TLB entry is written
1499 * through and traps if the PTE is unmapped.
1500 */
1501 pteval = ptep_get_and_clear(mm, address, pte);
1502
1503 set_tlb_ubc_flush_pending(mm, page, pte_dirty(pteval));
1504 } else {
1505 pteval = ptep_clear_flush(vma, address, pte);
1506 }
1507
1508 /* Move the dirty bit to the physical page now the pte is gone. */
1509 if (pte_dirty(pteval))
1510 set_page_dirty(page);
1511
1512 /* Update high watermark before we lower rss */
1513 update_hiwater_rss(mm);
1514
1515 if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
1516 if (PageHuge(page)) {
1517 hugetlb_count_sub(1 << compound_order(page), mm);
1518 } else {
1519 dec_mm_counter(mm, mm_counter(page));
1520 }
1521 set_pte_at(mm, address, pte,
1522 swp_entry_to_pte(make_hwpoison_entry(page)));
1523 } else if (pte_unused(pteval)) {
1524 /*
1525 * The guest indicated that the page content is of no
1526 * interest anymore. Simply discard the pte, vmscan
1527 * will take care of the rest.
1528 */
1529 dec_mm_counter(mm, mm_counter(page));
1530 } else if (IS_ENABLED(CONFIG_MIGRATION) && (flags & TTU_MIGRATION)) {
1531 swp_entry_t entry;
1532 pte_t swp_pte;
1533 /*
1534 * Store the pfn of the page in a special migration
1535 * pte. do_swap_page() will wait until the migration
1536 * pte is removed and then restart fault handling.
1537 */
1538 entry = make_migration_entry(page, pte_write(pteval));
1539 swp_pte = swp_entry_to_pte(entry);
1540 if (pte_soft_dirty(pteval))
1541 swp_pte = pte_swp_mksoft_dirty(swp_pte);
1542 set_pte_at(mm, address, pte, swp_pte);
1543 } else if (PageAnon(page)) {
1544 swp_entry_t entry = { .val = page_private(page) };
1545 pte_t swp_pte;
1546 /*
1547 * Store the swap location in the pte.
1548 * See handle_pte_fault() ...
1549 */
1550 VM_BUG_ON_PAGE(!PageSwapCache(page), page);
1551
1552 if (!PageDirty(page) && (flags & TTU_LZFREE)) {
1553 /* It's a freeable page by MADV_FREE */
1554 dec_mm_counter(mm, MM_ANONPAGES);
1555 rp->lazyfreed++;
1556 goto discard;
1557 }
1558
1559 if (swap_duplicate(entry) < 0) {
1560 set_pte_at(mm, address, pte, pteval);
1561 ret = SWAP_FAIL;
1562 goto out_unmap;
1563 }
1564 if (list_empty(&mm->mmlist)) {
1565 spin_lock(&mmlist_lock);
1566 if (list_empty(&mm->mmlist))
1567 list_add(&mm->mmlist, &init_mm.mmlist);
1568 spin_unlock(&mmlist_lock);
1569 }
1570 dec_mm_counter(mm, MM_ANONPAGES);
1571 inc_mm_counter(mm, MM_SWAPENTS);
1572 swp_pte = swp_entry_to_pte(entry);
1573 if (pte_soft_dirty(pteval))
1574 swp_pte = pte_swp_mksoft_dirty(swp_pte);
1575 set_pte_at(mm, address, pte, swp_pte);
1576 } else
1577 dec_mm_counter(mm, mm_counter_file(page));
1578
1579 discard:
1580 page_remove_rmap(page, PageHuge(page));
1581 put_page(page);
1582
1583 out_unmap:
1584 pte_unmap_unlock(pte, ptl);
1585 if (ret != SWAP_FAIL && ret != SWAP_MLOCK && !(flags & TTU_MUNLOCK))
1586 mmu_notifier_invalidate_page(mm, address);
1587 out:
1588 return ret;
1589 }
1590
1591 bool is_vma_temporary_stack(struct vm_area_struct *vma)
1592 {
1593 int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP);
1594
1595 if (!maybe_stack)
1596 return false;
1597
1598 if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) ==
1599 VM_STACK_INCOMPLETE_SETUP)
1600 return true;
1601
1602 return false;
1603 }
1604
1605 static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg)
1606 {
1607 return is_vma_temporary_stack(vma);
1608 }
1609
1610 static int page_mapcount_is_zero(struct page *page)
1611 {
1612 return !page_mapcount(page);
1613 }
1614
1615 /**
1616 * try_to_unmap - try to remove all page table mappings to a page
1617 * @page: the page to get unmapped
1618 * @flags: action and flags
1619 *
1620 * Tries to remove all the page table entries which are mapping this
1621 * page, used in the pageout path. Caller must hold the page lock.
1622 * Return values are:
1623 *
1624 * SWAP_SUCCESS - we succeeded in removing all mappings
1625 * SWAP_AGAIN - we missed a mapping, try again later
1626 * SWAP_FAIL - the page is unswappable
1627 * SWAP_MLOCK - page is mlocked.
1628 */
1629 int try_to_unmap(struct page *page, enum ttu_flags flags)
1630 {
1631 int ret;
1632 struct rmap_private rp = {
1633 .flags = flags,
1634 .lazyfreed = 0,
1635 };
1636
1637 struct rmap_walk_control rwc = {
1638 .rmap_one = try_to_unmap_one,
1639 .arg = &rp,
1640 .done = page_mapcount_is_zero,
1641 .anon_lock = page_lock_anon_vma_read,
1642 };
1643
1644 /*
1645 * During exec, a temporary VMA is setup and later moved.
1646 * The VMA is moved under the anon_vma lock but not the
1647 * page tables leading to a race where migration cannot
1648 * find the migration ptes. Rather than increasing the
1649 * locking requirements of exec(), migration skips
1650 * temporary VMAs until after exec() completes.
1651 */
1652 if ((flags & TTU_MIGRATION) && !PageKsm(page) && PageAnon(page))
1653 rwc.invalid_vma = invalid_migration_vma;
1654
1655 if (flags & TTU_RMAP_LOCKED)
1656 ret = rmap_walk_locked(page, &rwc);
1657 else
1658 ret = rmap_walk(page, &rwc);
1659
1660 if (ret != SWAP_MLOCK && !page_mapcount(page)) {
1661 ret = SWAP_SUCCESS;
1662 if (rp.lazyfreed && !PageDirty(page))
1663 ret = SWAP_LZFREE;
1664 }
1665 return ret;
1666 }
1667
1668 static int page_not_mapped(struct page *page)
1669 {
1670 return !page_mapped(page);
1671 };
1672
1673 /**
1674 * try_to_munlock - try to munlock a page
1675 * @page: the page to be munlocked
1676 *
1677 * Called from munlock code. Checks all of the VMAs mapping the page
1678 * to make sure nobody else has this page mlocked. The page will be
1679 * returned with PG_mlocked cleared if no other vmas have it mlocked.
1680 *
1681 * Return values are:
1682 *
1683 * SWAP_AGAIN - no vma is holding page mlocked, or,
1684 * SWAP_AGAIN - page mapped in mlocked vma -- couldn't acquire mmap sem
1685 * SWAP_FAIL - page cannot be located at present
1686 * SWAP_MLOCK - page is now mlocked.
1687 */
1688 int try_to_munlock(struct page *page)
1689 {
1690 int ret;
1691 struct rmap_private rp = {
1692 .flags = TTU_MUNLOCK,
1693 .lazyfreed = 0,
1694 };
1695
1696 struct rmap_walk_control rwc = {
1697 .rmap_one = try_to_unmap_one,
1698 .arg = &rp,
1699 .done = page_not_mapped,
1700 .anon_lock = page_lock_anon_vma_read,
1701
1702 };
1703
1704 VM_BUG_ON_PAGE(!PageLocked(page) || PageLRU(page), page);
1705
1706 ret = rmap_walk(page, &rwc);
1707 return ret;
1708 }
1709
1710 void __put_anon_vma(struct anon_vma *anon_vma)
1711 {
1712 struct anon_vma *root = anon_vma->root;
1713
1714 anon_vma_free(anon_vma);
1715 if (root != anon_vma && atomic_dec_and_test(&root->refcount))
1716 anon_vma_free(root);
1717 }
1718
1719 static struct anon_vma *rmap_walk_anon_lock(struct page *page,
1720 struct rmap_walk_control *rwc)
1721 {
1722 struct anon_vma *anon_vma;
1723
1724 if (rwc->anon_lock)
1725 return rwc->anon_lock(page);
1726
1727 /*
1728 * Note: remove_migration_ptes() cannot use page_lock_anon_vma_read()
1729 * because that depends on page_mapped(); but not all its usages
1730 * are holding mmap_sem. Users without mmap_sem are required to
1731 * take a reference count to prevent the anon_vma disappearing
1732 */
1733 anon_vma = page_anon_vma(page);
1734 if (!anon_vma)
1735 return NULL;
1736
1737 anon_vma_lock_read(anon_vma);
1738 return anon_vma;
1739 }
1740
1741 /*
1742 * rmap_walk_anon - do something to anonymous page using the object-based
1743 * rmap method
1744 * @page: the page to be handled
1745 * @rwc: control variable according to each walk type
1746 *
1747 * Find all the mappings of a page using the mapping pointer and the vma chains
1748 * contained in the anon_vma struct it points to.
1749 *
1750 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1751 * where the page was found will be held for write. So, we won't recheck
1752 * vm_flags for that VMA. That should be OK, because that vma shouldn't be
1753 * LOCKED.
1754 */
1755 static int rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc,
1756 bool locked)
1757 {
1758 struct anon_vma *anon_vma;
1759 pgoff_t pgoff;
1760 struct anon_vma_chain *avc;
1761 int ret = SWAP_AGAIN;
1762
1763 if (locked) {
1764 anon_vma = page_anon_vma(page);
1765 /* anon_vma disappear under us? */
1766 VM_BUG_ON_PAGE(!anon_vma, page);
1767 } else {
1768 anon_vma = rmap_walk_anon_lock(page, rwc);
1769 }
1770 if (!anon_vma)
1771 return ret;
1772
1773 pgoff = page_to_pgoff(page);
1774 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1775 struct vm_area_struct *vma = avc->vma;
1776 unsigned long address = vma_address(page, vma);
1777
1778 cond_resched();
1779
1780 if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
1781 continue;
1782
1783 ret = rwc->rmap_one(page, vma, address, rwc->arg);
1784 if (ret != SWAP_AGAIN)
1785 break;
1786 if (rwc->done && rwc->done(page))
1787 break;
1788 }
1789
1790 if (!locked)
1791 anon_vma_unlock_read(anon_vma);
1792 return ret;
1793 }
1794
1795 /*
1796 * rmap_walk_file - do something to file page using the object-based rmap method
1797 * @page: the page to be handled
1798 * @rwc: control variable according to each walk type
1799 *
1800 * Find all the mappings of a page using the mapping pointer and the vma chains
1801 * contained in the address_space struct it points to.
1802 *
1803 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1804 * where the page was found will be held for write. So, we won't recheck
1805 * vm_flags for that VMA. That should be OK, because that vma shouldn't be
1806 * LOCKED.
1807 */
1808 static int rmap_walk_file(struct page *page, struct rmap_walk_control *rwc,
1809 bool locked)
1810 {
1811 struct address_space *mapping = page_mapping(page);
1812 pgoff_t pgoff;
1813 struct vm_area_struct *vma;
1814 int ret = SWAP_AGAIN;
1815
1816 /*
1817 * The page lock not only makes sure that page->mapping cannot
1818 * suddenly be NULLified by truncation, it makes sure that the
1819 * structure at mapping cannot be freed and reused yet,
1820 * so we can safely take mapping->i_mmap_rwsem.
1821 */
1822 VM_BUG_ON_PAGE(!PageLocked(page), page);
1823
1824 if (!mapping)
1825 return ret;
1826
1827 pgoff = page_to_pgoff(page);
1828 if (!locked)
1829 i_mmap_lock_read(mapping);
1830 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
1831 unsigned long address = vma_address(page, vma);
1832
1833 cond_resched();
1834
1835 if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
1836 continue;
1837
1838 ret = rwc->rmap_one(page, vma, address, rwc->arg);
1839 if (ret != SWAP_AGAIN)
1840 goto done;
1841 if (rwc->done && rwc->done(page))
1842 goto done;
1843 }
1844
1845 done:
1846 if (!locked)
1847 i_mmap_unlock_read(mapping);
1848 return ret;
1849 }
1850
1851 int rmap_walk(struct page *page, struct rmap_walk_control *rwc)
1852 {
1853 if (unlikely(PageKsm(page)))
1854 return rmap_walk_ksm(page, rwc);
1855 else if (PageAnon(page))
1856 return rmap_walk_anon(page, rwc, false);
1857 else
1858 return rmap_walk_file(page, rwc, false);
1859 }
1860
1861 /* Like rmap_walk, but caller holds relevant rmap lock */
1862 int rmap_walk_locked(struct page *page, struct rmap_walk_control *rwc)
1863 {
1864 /* no ksm support for now */
1865 VM_BUG_ON_PAGE(PageKsm(page), page);
1866 if (PageAnon(page))
1867 return rmap_walk_anon(page, rwc, true);
1868 else
1869 return rmap_walk_file(page, rwc, true);
1870 }
1871
1872 #ifdef CONFIG_HUGETLB_PAGE
1873 /*
1874 * The following three functions are for anonymous (private mapped) hugepages.
1875 * Unlike common anonymous pages, anonymous hugepages have no accounting code
1876 * and no lru code, because we handle hugepages differently from common pages.
1877 */
1878 static void __hugepage_set_anon_rmap(struct page *page,
1879 struct vm_area_struct *vma, unsigned long address, int exclusive)
1880 {
1881 struct anon_vma *anon_vma = vma->anon_vma;
1882
1883 BUG_ON(!anon_vma);
1884
1885 if (PageAnon(page))
1886 return;
1887 if (!exclusive)
1888 anon_vma = anon_vma->root;
1889
1890 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1891 page->mapping = (struct address_space *) anon_vma;
1892 page->index = linear_page_index(vma, address);
1893 }
1894
1895 void hugepage_add_anon_rmap(struct page *page,
1896 struct vm_area_struct *vma, unsigned long address)
1897 {
1898 struct anon_vma *anon_vma = vma->anon_vma;
1899 int first;
1900
1901 BUG_ON(!PageLocked(page));
1902 BUG_ON(!anon_vma);
1903 /* address might be in next vma when migration races vma_adjust */
1904 first = atomic_inc_and_test(compound_mapcount_ptr(page));
1905 if (first)
1906 __hugepage_set_anon_rmap(page, vma, address, 0);
1907 }
1908
1909 void hugepage_add_new_anon_rmap(struct page *page,
1910 struct vm_area_struct *vma, unsigned long address)
1911 {
1912 BUG_ON(address < vma->vm_start || address >= vma->vm_end);
1913 atomic_set(compound_mapcount_ptr(page), 0);
1914 __hugepage_set_anon_rmap(page, vma, address, 1);
1915 }
1916 #endif /* CONFIG_HUGETLB_PAGE */