Merge tag 'del-shark-for-v3.13' of git://git.kernel.org/pub/scm/linux/kernel/git...
[linux-2.6.git] / mm / rmap.c
blobfd3ee7a54a13a52c7d8761ff8e20508f352d083b
1 /*
2 * mm/rmap.c - physical to virtual reverse mappings
4 * Copyright 2001, Rik van Riel <riel@conectiva.com.br>
5 * Released under the General Public License (GPL).
7 * Simple, low overhead reverse mapping scheme.
8 * Please try to keep this thing as modular as possible.
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.
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
21 * Lock ordering in mm:
23 * inode->i_mutex (while writing or truncating, not reading or faulting)
24 * mm->mmap_sem
25 * page->flags PG_locked (lock_page)
26 * mapping->i_mmap_mutex
27 * anon_vma->rwsem
28 * mm->page_table_lock or pte_lock
29 * zone->lru_lock (in mark_page_accessed, isolate_lru_page)
30 * swap_lock (in swap_duplicate, swap_info_get)
31 * mmlist_lock (in mmput, drain_mmlist and others)
32 * mapping->private_lock (in __set_page_dirty_buffers)
33 * inode->i_lock (in set_page_dirty's __mark_inode_dirty)
34 * bdi.wb->list_lock (in set_page_dirty's __mark_inode_dirty)
35 * sb_lock (within inode_lock in fs/fs-writeback.c)
36 * mapping->tree_lock (widely used, in set_page_dirty,
37 * in arch-dependent flush_dcache_mmap_lock,
38 * within bdi.wb->list_lock in __sync_single_inode)
40 * anon_vma->rwsem,mapping->i_mutex (memory_failure, collect_procs_anon)
41 * ->tasklist_lock
42 * pte map lock
45 #include <linux/mm.h>
46 #include <linux/pagemap.h>
47 #include <linux/swap.h>
48 #include <linux/swapops.h>
49 #include <linux/slab.h>
50 #include <linux/init.h>
51 #include <linux/ksm.h>
52 #include <linux/rmap.h>
53 #include <linux/rcupdate.h>
54 #include <linux/export.h>
55 #include <linux/memcontrol.h>
56 #include <linux/mmu_notifier.h>
57 #include <linux/migrate.h>
58 #include <linux/hugetlb.h>
59 #include <linux/backing-dev.h>
61 #include <asm/tlbflush.h>
63 #include "internal.h"
65 static struct kmem_cache *anon_vma_cachep;
66 static struct kmem_cache *anon_vma_chain_cachep;
68 static inline struct anon_vma *anon_vma_alloc(void)
70 struct anon_vma *anon_vma;
72 anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL);
73 if (anon_vma) {
74 atomic_set(&anon_vma->refcount, 1);
76 * Initialise the anon_vma root to point to itself. If called
77 * from fork, the root will be reset to the parents anon_vma.
79 anon_vma->root = anon_vma;
82 return anon_vma;
85 static inline void anon_vma_free(struct anon_vma *anon_vma)
87 VM_BUG_ON(atomic_read(&anon_vma->refcount));
90 * Synchronize against page_lock_anon_vma_read() such that
91 * we can safely hold the lock without the anon_vma getting
92 * freed.
94 * Relies on the full mb implied by the atomic_dec_and_test() from
95 * put_anon_vma() against the acquire barrier implied by
96 * down_read_trylock() from page_lock_anon_vma_read(). This orders:
98 * page_lock_anon_vma_read() VS put_anon_vma()
99 * down_read_trylock() atomic_dec_and_test()
100 * LOCK MB
101 * atomic_read() rwsem_is_locked()
103 * LOCK should suffice since the actual taking of the lock must
104 * happen _before_ what follows.
106 if (rwsem_is_locked(&anon_vma->root->rwsem)) {
107 anon_vma_lock_write(anon_vma);
108 anon_vma_unlock_write(anon_vma);
111 kmem_cache_free(anon_vma_cachep, anon_vma);
114 static inline struct anon_vma_chain *anon_vma_chain_alloc(gfp_t gfp)
116 return kmem_cache_alloc(anon_vma_chain_cachep, gfp);
119 static void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain)
121 kmem_cache_free(anon_vma_chain_cachep, anon_vma_chain);
124 static void anon_vma_chain_link(struct vm_area_struct *vma,
125 struct anon_vma_chain *avc,
126 struct anon_vma *anon_vma)
128 avc->vma = vma;
129 avc->anon_vma = anon_vma;
130 list_add(&avc->same_vma, &vma->anon_vma_chain);
131 anon_vma_interval_tree_insert(avc, &anon_vma->rb_root);
135 * anon_vma_prepare - attach an anon_vma to a memory region
136 * @vma: the memory region in question
138 * This makes sure the memory mapping described by 'vma' has
139 * an 'anon_vma' attached to it, so that we can associate the
140 * anonymous pages mapped into it with that anon_vma.
142 * The common case will be that we already have one, but if
143 * not we either need to find an adjacent mapping that we
144 * can re-use the anon_vma from (very common when the only
145 * reason for splitting a vma has been mprotect()), or we
146 * allocate a new one.
148 * Anon-vma allocations are very subtle, because we may have
149 * optimistically looked up an anon_vma in page_lock_anon_vma_read()
150 * and that may actually touch the spinlock even in the newly
151 * allocated vma (it depends on RCU to make sure that the
152 * anon_vma isn't actually destroyed).
154 * As a result, we need to do proper anon_vma locking even
155 * for the new allocation. At the same time, we do not want
156 * to do any locking for the common case of already having
157 * an anon_vma.
159 * This must be called with the mmap_sem held for reading.
161 int anon_vma_prepare(struct vm_area_struct *vma)
163 struct anon_vma *anon_vma = vma->anon_vma;
164 struct anon_vma_chain *avc;
166 might_sleep();
167 if (unlikely(!anon_vma)) {
168 struct mm_struct *mm = vma->vm_mm;
169 struct anon_vma *allocated;
171 avc = anon_vma_chain_alloc(GFP_KERNEL);
172 if (!avc)
173 goto out_enomem;
175 anon_vma = find_mergeable_anon_vma(vma);
176 allocated = NULL;
177 if (!anon_vma) {
178 anon_vma = anon_vma_alloc();
179 if (unlikely(!anon_vma))
180 goto out_enomem_free_avc;
181 allocated = anon_vma;
184 anon_vma_lock_write(anon_vma);
185 /* page_table_lock to protect against threads */
186 spin_lock(&mm->page_table_lock);
187 if (likely(!vma->anon_vma)) {
188 vma->anon_vma = anon_vma;
189 anon_vma_chain_link(vma, avc, anon_vma);
190 allocated = NULL;
191 avc = NULL;
193 spin_unlock(&mm->page_table_lock);
194 anon_vma_unlock_write(anon_vma);
196 if (unlikely(allocated))
197 put_anon_vma(allocated);
198 if (unlikely(avc))
199 anon_vma_chain_free(avc);
201 return 0;
203 out_enomem_free_avc:
204 anon_vma_chain_free(avc);
205 out_enomem:
206 return -ENOMEM;
210 * This is a useful helper function for locking the anon_vma root as
211 * we traverse the vma->anon_vma_chain, looping over anon_vma's that
212 * have the same vma.
214 * Such anon_vma's should have the same root, so you'd expect to see
215 * just a single mutex_lock for the whole traversal.
217 static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma)
219 struct anon_vma *new_root = anon_vma->root;
220 if (new_root != root) {
221 if (WARN_ON_ONCE(root))
222 up_write(&root->rwsem);
223 root = new_root;
224 down_write(&root->rwsem);
226 return root;
229 static inline void unlock_anon_vma_root(struct anon_vma *root)
231 if (root)
232 up_write(&root->rwsem);
236 * Attach the anon_vmas from src to dst.
237 * Returns 0 on success, -ENOMEM on failure.
239 int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
241 struct anon_vma_chain *avc, *pavc;
242 struct anon_vma *root = NULL;
244 list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
245 struct anon_vma *anon_vma;
247 avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN);
248 if (unlikely(!avc)) {
249 unlock_anon_vma_root(root);
250 root = NULL;
251 avc = anon_vma_chain_alloc(GFP_KERNEL);
252 if (!avc)
253 goto enomem_failure;
255 anon_vma = pavc->anon_vma;
256 root = lock_anon_vma_root(root, anon_vma);
257 anon_vma_chain_link(dst, avc, anon_vma);
259 unlock_anon_vma_root(root);
260 return 0;
262 enomem_failure:
263 unlink_anon_vmas(dst);
264 return -ENOMEM;
268 * Attach vma to its own anon_vma, as well as to the anon_vmas that
269 * the corresponding VMA in the parent process is attached to.
270 * Returns 0 on success, non-zero on failure.
272 int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
274 struct anon_vma_chain *avc;
275 struct anon_vma *anon_vma;
277 /* Don't bother if the parent process has no anon_vma here. */
278 if (!pvma->anon_vma)
279 return 0;
282 * First, attach the new VMA to the parent VMA's anon_vmas,
283 * so rmap can find non-COWed pages in child processes.
285 if (anon_vma_clone(vma, pvma))
286 return -ENOMEM;
288 /* Then add our own anon_vma. */
289 anon_vma = anon_vma_alloc();
290 if (!anon_vma)
291 goto out_error;
292 avc = anon_vma_chain_alloc(GFP_KERNEL);
293 if (!avc)
294 goto out_error_free_anon_vma;
297 * The root anon_vma's spinlock is the lock actually used when we
298 * lock any of the anon_vmas in this anon_vma tree.
300 anon_vma->root = pvma->anon_vma->root;
302 * With refcounts, an anon_vma can stay around longer than the
303 * process it belongs to. The root anon_vma needs to be pinned until
304 * this anon_vma is freed, because the lock lives in the root.
306 get_anon_vma(anon_vma->root);
307 /* Mark this anon_vma as the one where our new (COWed) pages go. */
308 vma->anon_vma = anon_vma;
309 anon_vma_lock_write(anon_vma);
310 anon_vma_chain_link(vma, avc, anon_vma);
311 anon_vma_unlock_write(anon_vma);
313 return 0;
315 out_error_free_anon_vma:
316 put_anon_vma(anon_vma);
317 out_error:
318 unlink_anon_vmas(vma);
319 return -ENOMEM;
322 void unlink_anon_vmas(struct vm_area_struct *vma)
324 struct anon_vma_chain *avc, *next;
325 struct anon_vma *root = NULL;
328 * Unlink each anon_vma chained to the VMA. This list is ordered
329 * from newest to oldest, ensuring the root anon_vma gets freed last.
331 list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
332 struct anon_vma *anon_vma = avc->anon_vma;
334 root = lock_anon_vma_root(root, anon_vma);
335 anon_vma_interval_tree_remove(avc, &anon_vma->rb_root);
338 * Leave empty anon_vmas on the list - we'll need
339 * to free them outside the lock.
341 if (RB_EMPTY_ROOT(&anon_vma->rb_root))
342 continue;
344 list_del(&avc->same_vma);
345 anon_vma_chain_free(avc);
347 unlock_anon_vma_root(root);
350 * Iterate the list once more, it now only contains empty and unlinked
351 * anon_vmas, destroy them. Could not do before due to __put_anon_vma()
352 * needing to write-acquire the anon_vma->root->rwsem.
354 list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
355 struct anon_vma *anon_vma = avc->anon_vma;
357 put_anon_vma(anon_vma);
359 list_del(&avc->same_vma);
360 anon_vma_chain_free(avc);
364 static void anon_vma_ctor(void *data)
366 struct anon_vma *anon_vma = data;
368 init_rwsem(&anon_vma->rwsem);
369 atomic_set(&anon_vma->refcount, 0);
370 anon_vma->rb_root = RB_ROOT;
373 void __init anon_vma_init(void)
375 anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
376 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor);
377 anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain, SLAB_PANIC);
381 * Getting a lock on a stable anon_vma from a page off the LRU is tricky!
383 * Since there is no serialization what so ever against page_remove_rmap()
384 * the best this function can do is return a locked anon_vma that might
385 * have been relevant to this page.
387 * The page might have been remapped to a different anon_vma or the anon_vma
388 * returned may already be freed (and even reused).
390 * In case it was remapped to a different anon_vma, the new anon_vma will be a
391 * child of the old anon_vma, and the anon_vma lifetime rules will therefore
392 * ensure that any anon_vma obtained from the page will still be valid for as
393 * long as we observe page_mapped() [ hence all those page_mapped() tests ].
395 * All users of this function must be very careful when walking the anon_vma
396 * chain and verify that the page in question is indeed mapped in it
397 * [ something equivalent to page_mapped_in_vma() ].
399 * Since anon_vma's slab is DESTROY_BY_RCU and we know from page_remove_rmap()
400 * that the anon_vma pointer from page->mapping is valid if there is a
401 * mapcount, we can dereference the anon_vma after observing those.
403 struct anon_vma *page_get_anon_vma(struct page *page)
405 struct anon_vma *anon_vma = NULL;
406 unsigned long anon_mapping;
408 rcu_read_lock();
409 anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping);
410 if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
411 goto out;
412 if (!page_mapped(page))
413 goto out;
415 anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
416 if (!atomic_inc_not_zero(&anon_vma->refcount)) {
417 anon_vma = NULL;
418 goto out;
422 * If this page is still mapped, then its anon_vma cannot have been
423 * freed. But if it has been unmapped, we have no security against the
424 * anon_vma structure being freed and reused (for another anon_vma:
425 * SLAB_DESTROY_BY_RCU guarantees that - so the atomic_inc_not_zero()
426 * above cannot corrupt).
428 if (!page_mapped(page)) {
429 put_anon_vma(anon_vma);
430 anon_vma = NULL;
432 out:
433 rcu_read_unlock();
435 return anon_vma;
439 * Similar to page_get_anon_vma() except it locks the anon_vma.
441 * Its a little more complex as it tries to keep the fast path to a single
442 * atomic op -- the trylock. If we fail the trylock, we fall back to getting a
443 * reference like with page_get_anon_vma() and then block on the mutex.
445 struct anon_vma *page_lock_anon_vma_read(struct page *page)
447 struct anon_vma *anon_vma = NULL;
448 struct anon_vma *root_anon_vma;
449 unsigned long anon_mapping;
451 rcu_read_lock();
452 anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping);
453 if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
454 goto out;
455 if (!page_mapped(page))
456 goto out;
458 anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
459 root_anon_vma = ACCESS_ONCE(anon_vma->root);
460 if (down_read_trylock(&root_anon_vma->rwsem)) {
462 * If the page is still mapped, then this anon_vma is still
463 * its anon_vma, and holding the mutex ensures that it will
464 * not go away, see anon_vma_free().
466 if (!page_mapped(page)) {
467 up_read(&root_anon_vma->rwsem);
468 anon_vma = NULL;
470 goto out;
473 /* trylock failed, we got to sleep */
474 if (!atomic_inc_not_zero(&anon_vma->refcount)) {
475 anon_vma = NULL;
476 goto out;
479 if (!page_mapped(page)) {
480 put_anon_vma(anon_vma);
481 anon_vma = NULL;
482 goto out;
485 /* we pinned the anon_vma, its safe to sleep */
486 rcu_read_unlock();
487 anon_vma_lock_read(anon_vma);
489 if (atomic_dec_and_test(&anon_vma->refcount)) {
491 * Oops, we held the last refcount, release the lock
492 * and bail -- can't simply use put_anon_vma() because
493 * we'll deadlock on the anon_vma_lock_write() recursion.
495 anon_vma_unlock_read(anon_vma);
496 __put_anon_vma(anon_vma);
497 anon_vma = NULL;
500 return anon_vma;
502 out:
503 rcu_read_unlock();
504 return anon_vma;
507 void page_unlock_anon_vma_read(struct anon_vma *anon_vma)
509 anon_vma_unlock_read(anon_vma);
513 * At what user virtual address is page expected in @vma?
515 static inline unsigned long
516 __vma_address(struct page *page, struct vm_area_struct *vma)
518 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
520 if (unlikely(is_vm_hugetlb_page(vma)))
521 pgoff = page->index << huge_page_order(page_hstate(page));
523 return vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
526 inline unsigned long
527 vma_address(struct page *page, struct vm_area_struct *vma)
529 unsigned long address = __vma_address(page, vma);
531 /* page should be within @vma mapping range */
532 VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
534 return address;
538 * At what user virtual address is page expected in vma?
539 * Caller should check the page is actually part of the vma.
541 unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
543 unsigned long address;
544 if (PageAnon(page)) {
545 struct anon_vma *page__anon_vma = page_anon_vma(page);
547 * Note: swapoff's unuse_vma() is more efficient with this
548 * check, and needs it to match anon_vma when KSM is active.
550 if (!vma->anon_vma || !page__anon_vma ||
551 vma->anon_vma->root != page__anon_vma->root)
552 return -EFAULT;
553 } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
554 if (!vma->vm_file ||
555 vma->vm_file->f_mapping != page->mapping)
556 return -EFAULT;
557 } else
558 return -EFAULT;
559 address = __vma_address(page, vma);
560 if (unlikely(address < vma->vm_start || address >= vma->vm_end))
561 return -EFAULT;
562 return address;
565 pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address)
567 pgd_t *pgd;
568 pud_t *pud;
569 pmd_t *pmd = NULL;
571 pgd = pgd_offset(mm, address);
572 if (!pgd_present(*pgd))
573 goto out;
575 pud = pud_offset(pgd, address);
576 if (!pud_present(*pud))
577 goto out;
579 pmd = pmd_offset(pud, address);
580 if (!pmd_present(*pmd))
581 pmd = NULL;
582 out:
583 return pmd;
587 * Check that @page is mapped at @address into @mm.
589 * If @sync is false, page_check_address may perform a racy check to avoid
590 * the page table lock when the pte is not present (helpful when reclaiming
591 * highly shared pages).
593 * On success returns with pte mapped and locked.
595 pte_t *__page_check_address(struct page *page, struct mm_struct *mm,
596 unsigned long address, spinlock_t **ptlp, int sync)
598 pmd_t *pmd;
599 pte_t *pte;
600 spinlock_t *ptl;
602 if (unlikely(PageHuge(page))) {
603 pte = huge_pte_offset(mm, address);
604 ptl = &mm->page_table_lock;
605 goto check;
608 pmd = mm_find_pmd(mm, address);
609 if (!pmd)
610 return NULL;
612 if (pmd_trans_huge(*pmd))
613 return NULL;
615 pte = pte_offset_map(pmd, address);
616 /* Make a quick check before getting the lock */
617 if (!sync && !pte_present(*pte)) {
618 pte_unmap(pte);
619 return NULL;
622 ptl = pte_lockptr(mm, pmd);
623 check:
624 spin_lock(ptl);
625 if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) {
626 *ptlp = ptl;
627 return pte;
629 pte_unmap_unlock(pte, ptl);
630 return NULL;
634 * page_mapped_in_vma - check whether a page is really mapped in a VMA
635 * @page: the page to test
636 * @vma: the VMA to test
638 * Returns 1 if the page is mapped into the page tables of the VMA, 0
639 * if the page is not mapped into the page tables of this VMA. Only
640 * valid for normal file or anonymous VMAs.
642 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
644 unsigned long address;
645 pte_t *pte;
646 spinlock_t *ptl;
648 address = __vma_address(page, vma);
649 if (unlikely(address < vma->vm_start || address >= vma->vm_end))
650 return 0;
651 pte = page_check_address(page, vma->vm_mm, address, &ptl, 1);
652 if (!pte) /* the page is not in this mm */
653 return 0;
654 pte_unmap_unlock(pte, ptl);
656 return 1;
660 * Subfunctions of page_referenced: page_referenced_one called
661 * repeatedly from either page_referenced_anon or page_referenced_file.
663 int page_referenced_one(struct page *page, struct vm_area_struct *vma,
664 unsigned long address, unsigned int *mapcount,
665 unsigned long *vm_flags)
667 struct mm_struct *mm = vma->vm_mm;
668 int referenced = 0;
670 if (unlikely(PageTransHuge(page))) {
671 pmd_t *pmd;
673 spin_lock(&mm->page_table_lock);
675 * rmap might return false positives; we must filter
676 * these out using page_check_address_pmd().
678 pmd = page_check_address_pmd(page, mm, address,
679 PAGE_CHECK_ADDRESS_PMD_FLAG);
680 if (!pmd) {
681 spin_unlock(&mm->page_table_lock);
682 goto out;
685 if (vma->vm_flags & VM_LOCKED) {
686 spin_unlock(&mm->page_table_lock);
687 *mapcount = 0; /* break early from loop */
688 *vm_flags |= VM_LOCKED;
689 goto out;
692 /* go ahead even if the pmd is pmd_trans_splitting() */
693 if (pmdp_clear_flush_young_notify(vma, address, pmd))
694 referenced++;
695 spin_unlock(&mm->page_table_lock);
696 } else {
697 pte_t *pte;
698 spinlock_t *ptl;
701 * rmap might return false positives; we must filter
702 * these out using page_check_address().
704 pte = page_check_address(page, mm, address, &ptl, 0);
705 if (!pte)
706 goto out;
708 if (vma->vm_flags & VM_LOCKED) {
709 pte_unmap_unlock(pte, ptl);
710 *mapcount = 0; /* break early from loop */
711 *vm_flags |= VM_LOCKED;
712 goto out;
715 if (ptep_clear_flush_young_notify(vma, address, pte)) {
717 * Don't treat a reference through a sequentially read
718 * mapping as such. If the page has been used in
719 * another mapping, we will catch it; if this other
720 * mapping is already gone, the unmap path will have
721 * set PG_referenced or activated the page.
723 if (likely(!(vma->vm_flags & VM_SEQ_READ)))
724 referenced++;
726 pte_unmap_unlock(pte, ptl);
729 (*mapcount)--;
731 if (referenced)
732 *vm_flags |= vma->vm_flags;
733 out:
734 return referenced;
737 static int page_referenced_anon(struct page *page,
738 struct mem_cgroup *memcg,
739 unsigned long *vm_flags)
741 unsigned int mapcount;
742 struct anon_vma *anon_vma;
743 pgoff_t pgoff;
744 struct anon_vma_chain *avc;
745 int referenced = 0;
747 anon_vma = page_lock_anon_vma_read(page);
748 if (!anon_vma)
749 return referenced;
751 mapcount = page_mapcount(page);
752 pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
753 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
754 struct vm_area_struct *vma = avc->vma;
755 unsigned long address = vma_address(page, vma);
757 * If we are reclaiming on behalf of a cgroup, skip
758 * counting on behalf of references from different
759 * cgroups
761 if (memcg && !mm_match_cgroup(vma->vm_mm, memcg))
762 continue;
763 referenced += page_referenced_one(page, vma, address,
764 &mapcount, vm_flags);
765 if (!mapcount)
766 break;
769 page_unlock_anon_vma_read(anon_vma);
770 return referenced;
774 * page_referenced_file - referenced check for object-based rmap
775 * @page: the page we're checking references on.
776 * @memcg: target memory control group
777 * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
779 * For an object-based mapped page, find all the places it is mapped and
780 * check/clear the referenced flag. This is done by following the page->mapping
781 * pointer, then walking the chain of vmas it holds. It returns the number
782 * of references it found.
784 * This function is only called from page_referenced for object-based pages.
786 static int page_referenced_file(struct page *page,
787 struct mem_cgroup *memcg,
788 unsigned long *vm_flags)
790 unsigned int mapcount;
791 struct address_space *mapping = page->mapping;
792 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
793 struct vm_area_struct *vma;
794 int referenced = 0;
797 * The caller's checks on page->mapping and !PageAnon have made
798 * sure that this is a file page: the check for page->mapping
799 * excludes the case just before it gets set on an anon page.
801 BUG_ON(PageAnon(page));
804 * The page lock not only makes sure that page->mapping cannot
805 * suddenly be NULLified by truncation, it makes sure that the
806 * structure at mapping cannot be freed and reused yet,
807 * so we can safely take mapping->i_mmap_mutex.
809 BUG_ON(!PageLocked(page));
811 mutex_lock(&mapping->i_mmap_mutex);
814 * i_mmap_mutex does not stabilize mapcount at all, but mapcount
815 * is more likely to be accurate if we note it after spinning.
817 mapcount = page_mapcount(page);
819 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
820 unsigned long address = vma_address(page, vma);
822 * If we are reclaiming on behalf of a cgroup, skip
823 * counting on behalf of references from different
824 * cgroups
826 if (memcg && !mm_match_cgroup(vma->vm_mm, memcg))
827 continue;
828 referenced += page_referenced_one(page, vma, address,
829 &mapcount, vm_flags);
830 if (!mapcount)
831 break;
834 mutex_unlock(&mapping->i_mmap_mutex);
835 return referenced;
839 * page_referenced - test if the page was referenced
840 * @page: the page to test
841 * @is_locked: caller holds lock on the page
842 * @memcg: target memory cgroup
843 * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
845 * Quick test_and_clear_referenced for all mappings to a page,
846 * returns the number of ptes which referenced the page.
848 int page_referenced(struct page *page,
849 int is_locked,
850 struct mem_cgroup *memcg,
851 unsigned long *vm_flags)
853 int referenced = 0;
854 int we_locked = 0;
856 *vm_flags = 0;
857 if (page_mapped(page) && page_rmapping(page)) {
858 if (!is_locked && (!PageAnon(page) || PageKsm(page))) {
859 we_locked = trylock_page(page);
860 if (!we_locked) {
861 referenced++;
862 goto out;
865 if (unlikely(PageKsm(page)))
866 referenced += page_referenced_ksm(page, memcg,
867 vm_flags);
868 else if (PageAnon(page))
869 referenced += page_referenced_anon(page, memcg,
870 vm_flags);
871 else if (page->mapping)
872 referenced += page_referenced_file(page, memcg,
873 vm_flags);
874 if (we_locked)
875 unlock_page(page);
877 out:
878 return referenced;
881 static int page_mkclean_one(struct page *page, struct vm_area_struct *vma,
882 unsigned long address)
884 struct mm_struct *mm = vma->vm_mm;
885 pte_t *pte;
886 spinlock_t *ptl;
887 int ret = 0;
889 pte = page_check_address(page, mm, address, &ptl, 1);
890 if (!pte)
891 goto out;
893 if (pte_dirty(*pte) || pte_write(*pte)) {
894 pte_t entry;
896 flush_cache_page(vma, address, pte_pfn(*pte));
897 entry = ptep_clear_flush(vma, address, pte);
898 entry = pte_wrprotect(entry);
899 entry = pte_mkclean(entry);
900 set_pte_at(mm, address, pte, entry);
901 ret = 1;
904 pte_unmap_unlock(pte, ptl);
906 if (ret)
907 mmu_notifier_invalidate_page(mm, address);
908 out:
909 return ret;
912 static int page_mkclean_file(struct address_space *mapping, struct page *page)
914 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
915 struct vm_area_struct *vma;
916 int ret = 0;
918 BUG_ON(PageAnon(page));
920 mutex_lock(&mapping->i_mmap_mutex);
921 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
922 if (vma->vm_flags & VM_SHARED) {
923 unsigned long address = vma_address(page, vma);
924 ret += page_mkclean_one(page, vma, address);
927 mutex_unlock(&mapping->i_mmap_mutex);
928 return ret;
931 int page_mkclean(struct page *page)
933 int ret = 0;
935 BUG_ON(!PageLocked(page));
937 if (page_mapped(page)) {
938 struct address_space *mapping = page_mapping(page);
939 if (mapping)
940 ret = page_mkclean_file(mapping, page);
943 return ret;
945 EXPORT_SYMBOL_GPL(page_mkclean);
948 * page_move_anon_rmap - move a page to our anon_vma
949 * @page: the page to move to our anon_vma
950 * @vma: the vma the page belongs to
951 * @address: the user virtual address mapped
953 * When a page belongs exclusively to one process after a COW event,
954 * that page can be moved into the anon_vma that belongs to just that
955 * process, so the rmap code will not search the parent or sibling
956 * processes.
958 void page_move_anon_rmap(struct page *page,
959 struct vm_area_struct *vma, unsigned long address)
961 struct anon_vma *anon_vma = vma->anon_vma;
963 VM_BUG_ON(!PageLocked(page));
964 VM_BUG_ON(!anon_vma);
965 VM_BUG_ON(page->index != linear_page_index(vma, address));
967 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
968 page->mapping = (struct address_space *) anon_vma;
972 * __page_set_anon_rmap - set up new anonymous rmap
973 * @page: Page to add to rmap
974 * @vma: VM area to add page to.
975 * @address: User virtual address of the mapping
976 * @exclusive: the page is exclusively owned by the current process
978 static void __page_set_anon_rmap(struct page *page,
979 struct vm_area_struct *vma, unsigned long address, int exclusive)
981 struct anon_vma *anon_vma = vma->anon_vma;
983 BUG_ON(!anon_vma);
985 if (PageAnon(page))
986 return;
989 * If the page isn't exclusively mapped into this vma,
990 * we must use the _oldest_ possible anon_vma for the
991 * page mapping!
993 if (!exclusive)
994 anon_vma = anon_vma->root;
996 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
997 page->mapping = (struct address_space *) anon_vma;
998 page->index = linear_page_index(vma, address);
1002 * __page_check_anon_rmap - sanity check anonymous rmap addition
1003 * @page: the page to add the mapping to
1004 * @vma: the vm area in which the mapping is added
1005 * @address: the user virtual address mapped
1007 static void __page_check_anon_rmap(struct page *page,
1008 struct vm_area_struct *vma, unsigned long address)
1010 #ifdef CONFIG_DEBUG_VM
1012 * The page's anon-rmap details (mapping and index) are guaranteed to
1013 * be set up correctly at this point.
1015 * We have exclusion against page_add_anon_rmap because the caller
1016 * always holds the page locked, except if called from page_dup_rmap,
1017 * in which case the page is already known to be setup.
1019 * We have exclusion against page_add_new_anon_rmap because those pages
1020 * are initially only visible via the pagetables, and the pte is locked
1021 * over the call to page_add_new_anon_rmap.
1023 BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root);
1024 BUG_ON(page->index != linear_page_index(vma, address));
1025 #endif
1029 * page_add_anon_rmap - add pte mapping to an anonymous page
1030 * @page: the page to add the mapping to
1031 * @vma: the vm area in which the mapping is added
1032 * @address: the user virtual address mapped
1034 * The caller needs to hold the pte lock, and the page must be locked in
1035 * the anon_vma case: to serialize mapping,index checking after setting,
1036 * and to ensure that PageAnon is not being upgraded racily to PageKsm
1037 * (but PageKsm is never downgraded to PageAnon).
1039 void page_add_anon_rmap(struct page *page,
1040 struct vm_area_struct *vma, unsigned long address)
1042 do_page_add_anon_rmap(page, vma, address, 0);
1046 * Special version of the above for do_swap_page, which often runs
1047 * into pages that are exclusively owned by the current process.
1048 * Everybody else should continue to use page_add_anon_rmap above.
1050 void do_page_add_anon_rmap(struct page *page,
1051 struct vm_area_struct *vma, unsigned long address, int exclusive)
1053 int first = atomic_inc_and_test(&page->_mapcount);
1054 if (first) {
1055 if (PageTransHuge(page))
1056 __inc_zone_page_state(page,
1057 NR_ANON_TRANSPARENT_HUGEPAGES);
1058 __mod_zone_page_state(page_zone(page), NR_ANON_PAGES,
1059 hpage_nr_pages(page));
1061 if (unlikely(PageKsm(page)))
1062 return;
1064 VM_BUG_ON(!PageLocked(page));
1065 /* address might be in next vma when migration races vma_adjust */
1066 if (first)
1067 __page_set_anon_rmap(page, vma, address, exclusive);
1068 else
1069 __page_check_anon_rmap(page, vma, address);
1073 * page_add_new_anon_rmap - add pte mapping to a new anonymous page
1074 * @page: the page to add the mapping to
1075 * @vma: the vm area in which the mapping is added
1076 * @address: the user virtual address mapped
1078 * Same as page_add_anon_rmap but must only be called on *new* pages.
1079 * This means the inc-and-test can be bypassed.
1080 * Page does not have to be locked.
1082 void page_add_new_anon_rmap(struct page *page,
1083 struct vm_area_struct *vma, unsigned long address)
1085 VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
1086 SetPageSwapBacked(page);
1087 atomic_set(&page->_mapcount, 0); /* increment count (starts at -1) */
1088 if (PageTransHuge(page))
1089 __inc_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
1090 __mod_zone_page_state(page_zone(page), NR_ANON_PAGES,
1091 hpage_nr_pages(page));
1092 __page_set_anon_rmap(page, vma, address, 1);
1093 if (!mlocked_vma_newpage(vma, page)) {
1094 SetPageActive(page);
1095 lru_cache_add(page);
1096 } else
1097 add_page_to_unevictable_list(page);
1101 * page_add_file_rmap - add pte mapping to a file page
1102 * @page: the page to add the mapping to
1104 * The caller needs to hold the pte lock.
1106 void page_add_file_rmap(struct page *page)
1108 bool locked;
1109 unsigned long flags;
1111 mem_cgroup_begin_update_page_stat(page, &locked, &flags);
1112 if (atomic_inc_and_test(&page->_mapcount)) {
1113 __inc_zone_page_state(page, NR_FILE_MAPPED);
1114 mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_FILE_MAPPED);
1116 mem_cgroup_end_update_page_stat(page, &locked, &flags);
1120 * page_remove_rmap - take down pte mapping from a page
1121 * @page: page to remove mapping from
1123 * The caller needs to hold the pte lock.
1125 void page_remove_rmap(struct page *page)
1127 bool anon = PageAnon(page);
1128 bool locked;
1129 unsigned long flags;
1132 * The anon case has no mem_cgroup page_stat to update; but may
1133 * uncharge_page() below, where the lock ordering can deadlock if
1134 * we hold the lock against page_stat move: so avoid it on anon.
1136 if (!anon)
1137 mem_cgroup_begin_update_page_stat(page, &locked, &flags);
1139 /* page still mapped by someone else? */
1140 if (!atomic_add_negative(-1, &page->_mapcount))
1141 goto out;
1144 * Hugepages are not counted in NR_ANON_PAGES nor NR_FILE_MAPPED
1145 * and not charged by memcg for now.
1147 if (unlikely(PageHuge(page)))
1148 goto out;
1149 if (anon) {
1150 mem_cgroup_uncharge_page(page);
1151 if (PageTransHuge(page))
1152 __dec_zone_page_state(page,
1153 NR_ANON_TRANSPARENT_HUGEPAGES);
1154 __mod_zone_page_state(page_zone(page), NR_ANON_PAGES,
1155 -hpage_nr_pages(page));
1156 } else {
1157 __dec_zone_page_state(page, NR_FILE_MAPPED);
1158 mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_FILE_MAPPED);
1159 mem_cgroup_end_update_page_stat(page, &locked, &flags);
1161 if (unlikely(PageMlocked(page)))
1162 clear_page_mlock(page);
1164 * It would be tidy to reset the PageAnon mapping here,
1165 * but that might overwrite a racing page_add_anon_rmap
1166 * which increments mapcount after us but sets mapping
1167 * before us: so leave the reset to free_hot_cold_page,
1168 * and remember that it's only reliable while mapped.
1169 * Leaving it set also helps swapoff to reinstate ptes
1170 * faster for those pages still in swapcache.
1172 return;
1173 out:
1174 if (!anon)
1175 mem_cgroup_end_update_page_stat(page, &locked, &flags);
1179 * Subfunctions of try_to_unmap: try_to_unmap_one called
1180 * repeatedly from try_to_unmap_ksm, try_to_unmap_anon or try_to_unmap_file.
1182 int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
1183 unsigned long address, enum ttu_flags flags)
1185 struct mm_struct *mm = vma->vm_mm;
1186 pte_t *pte;
1187 pte_t pteval;
1188 spinlock_t *ptl;
1189 int ret = SWAP_AGAIN;
1191 pte = page_check_address(page, mm, address, &ptl, 0);
1192 if (!pte)
1193 goto out;
1196 * If the page is mlock()d, we cannot swap it out.
1197 * If it's recently referenced (perhaps page_referenced
1198 * skipped over this mm) then we should reactivate it.
1200 if (!(flags & TTU_IGNORE_MLOCK)) {
1201 if (vma->vm_flags & VM_LOCKED)
1202 goto out_mlock;
1204 if (TTU_ACTION(flags) == TTU_MUNLOCK)
1205 goto out_unmap;
1207 if (!(flags & TTU_IGNORE_ACCESS)) {
1208 if (ptep_clear_flush_young_notify(vma, address, pte)) {
1209 ret = SWAP_FAIL;
1210 goto out_unmap;
1214 /* Nuke the page table entry. */
1215 flush_cache_page(vma, address, page_to_pfn(page));
1216 pteval = ptep_clear_flush(vma, address, pte);
1218 /* Move the dirty bit to the physical page now the pte is gone. */
1219 if (pte_dirty(pteval))
1220 set_page_dirty(page);
1222 /* Update high watermark before we lower rss */
1223 update_hiwater_rss(mm);
1225 if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
1226 if (!PageHuge(page)) {
1227 if (PageAnon(page))
1228 dec_mm_counter(mm, MM_ANONPAGES);
1229 else
1230 dec_mm_counter(mm, MM_FILEPAGES);
1232 set_pte_at(mm, address, pte,
1233 swp_entry_to_pte(make_hwpoison_entry(page)));
1234 } else if (PageAnon(page)) {
1235 swp_entry_t entry = { .val = page_private(page) };
1236 pte_t swp_pte;
1238 if (PageSwapCache(page)) {
1240 * Store the swap location in the pte.
1241 * See handle_pte_fault() ...
1243 if (swap_duplicate(entry) < 0) {
1244 set_pte_at(mm, address, pte, pteval);
1245 ret = SWAP_FAIL;
1246 goto out_unmap;
1248 if (list_empty(&mm->mmlist)) {
1249 spin_lock(&mmlist_lock);
1250 if (list_empty(&mm->mmlist))
1251 list_add(&mm->mmlist, &init_mm.mmlist);
1252 spin_unlock(&mmlist_lock);
1254 dec_mm_counter(mm, MM_ANONPAGES);
1255 inc_mm_counter(mm, MM_SWAPENTS);
1256 } else if (IS_ENABLED(CONFIG_MIGRATION)) {
1258 * Store the pfn of the page in a special migration
1259 * pte. do_swap_page() will wait until the migration
1260 * pte is removed and then restart fault handling.
1262 BUG_ON(TTU_ACTION(flags) != TTU_MIGRATION);
1263 entry = make_migration_entry(page, pte_write(pteval));
1265 swp_pte = swp_entry_to_pte(entry);
1266 if (pte_soft_dirty(pteval))
1267 swp_pte = pte_swp_mksoft_dirty(swp_pte);
1268 set_pte_at(mm, address, pte, swp_pte);
1269 BUG_ON(pte_file(*pte));
1270 } else if (IS_ENABLED(CONFIG_MIGRATION) &&
1271 (TTU_ACTION(flags) == TTU_MIGRATION)) {
1272 /* Establish migration entry for a file page */
1273 swp_entry_t entry;
1274 entry = make_migration_entry(page, pte_write(pteval));
1275 set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
1276 } else
1277 dec_mm_counter(mm, MM_FILEPAGES);
1279 page_remove_rmap(page);
1280 page_cache_release(page);
1282 out_unmap:
1283 pte_unmap_unlock(pte, ptl);
1284 if (ret != SWAP_FAIL)
1285 mmu_notifier_invalidate_page(mm, address);
1286 out:
1287 return ret;
1289 out_mlock:
1290 pte_unmap_unlock(pte, ptl);
1294 * We need mmap_sem locking, Otherwise VM_LOCKED check makes
1295 * unstable result and race. Plus, We can't wait here because
1296 * we now hold anon_vma->rwsem or mapping->i_mmap_mutex.
1297 * if trylock failed, the page remain in evictable lru and later
1298 * vmscan could retry to move the page to unevictable lru if the
1299 * page is actually mlocked.
1301 if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
1302 if (vma->vm_flags & VM_LOCKED) {
1303 mlock_vma_page(page);
1304 ret = SWAP_MLOCK;
1306 up_read(&vma->vm_mm->mmap_sem);
1308 return ret;
1312 * objrmap doesn't work for nonlinear VMAs because the assumption that
1313 * offset-into-file correlates with offset-into-virtual-addresses does not hold.
1314 * Consequently, given a particular page and its ->index, we cannot locate the
1315 * ptes which are mapping that page without an exhaustive linear search.
1317 * So what this code does is a mini "virtual scan" of each nonlinear VMA which
1318 * maps the file to which the target page belongs. The ->vm_private_data field
1319 * holds the current cursor into that scan. Successive searches will circulate
1320 * around the vma's virtual address space.
1322 * So as more replacement pressure is applied to the pages in a nonlinear VMA,
1323 * more scanning pressure is placed against them as well. Eventually pages
1324 * will become fully unmapped and are eligible for eviction.
1326 * For very sparsely populated VMAs this is a little inefficient - chances are
1327 * there there won't be many ptes located within the scan cluster. In this case
1328 * maybe we could scan further - to the end of the pte page, perhaps.
1330 * Mlocked pages: check VM_LOCKED under mmap_sem held for read, if we can
1331 * acquire it without blocking. If vma locked, mlock the pages in the cluster,
1332 * rather than unmapping them. If we encounter the "check_page" that vmscan is
1333 * trying to unmap, return SWAP_MLOCK, else default SWAP_AGAIN.
1335 #define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE)
1336 #define CLUSTER_MASK (~(CLUSTER_SIZE - 1))
1338 static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount,
1339 struct vm_area_struct *vma, struct page *check_page)
1341 struct mm_struct *mm = vma->vm_mm;
1342 pmd_t *pmd;
1343 pte_t *pte;
1344 pte_t pteval;
1345 spinlock_t *ptl;
1346 struct page *page;
1347 unsigned long address;
1348 unsigned long mmun_start; /* For mmu_notifiers */
1349 unsigned long mmun_end; /* For mmu_notifiers */
1350 unsigned long end;
1351 int ret = SWAP_AGAIN;
1352 int locked_vma = 0;
1354 address = (vma->vm_start + cursor) & CLUSTER_MASK;
1355 end = address + CLUSTER_SIZE;
1356 if (address < vma->vm_start)
1357 address = vma->vm_start;
1358 if (end > vma->vm_end)
1359 end = vma->vm_end;
1361 pmd = mm_find_pmd(mm, address);
1362 if (!pmd)
1363 return ret;
1365 mmun_start = address;
1366 mmun_end = end;
1367 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1370 * If we can acquire the mmap_sem for read, and vma is VM_LOCKED,
1371 * keep the sem while scanning the cluster for mlocking pages.
1373 if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
1374 locked_vma = (vma->vm_flags & VM_LOCKED);
1375 if (!locked_vma)
1376 up_read(&vma->vm_mm->mmap_sem); /* don't need it */
1379 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1381 /* Update high watermark before we lower rss */
1382 update_hiwater_rss(mm);
1384 for (; address < end; pte++, address += PAGE_SIZE) {
1385 if (!pte_present(*pte))
1386 continue;
1387 page = vm_normal_page(vma, address, *pte);
1388 BUG_ON(!page || PageAnon(page));
1390 if (locked_vma) {
1391 mlock_vma_page(page); /* no-op if already mlocked */
1392 if (page == check_page)
1393 ret = SWAP_MLOCK;
1394 continue; /* don't unmap */
1397 if (ptep_clear_flush_young_notify(vma, address, pte))
1398 continue;
1400 /* Nuke the page table entry. */
1401 flush_cache_page(vma, address, pte_pfn(*pte));
1402 pteval = ptep_clear_flush(vma, address, pte);
1404 /* If nonlinear, store the file page offset in the pte. */
1405 if (page->index != linear_page_index(vma, address)) {
1406 pte_t ptfile = pgoff_to_pte(page->index);
1407 if (pte_soft_dirty(pteval))
1408 pte_file_mksoft_dirty(ptfile);
1409 set_pte_at(mm, address, pte, ptfile);
1412 /* Move the dirty bit to the physical page now the pte is gone. */
1413 if (pte_dirty(pteval))
1414 set_page_dirty(page);
1416 page_remove_rmap(page);
1417 page_cache_release(page);
1418 dec_mm_counter(mm, MM_FILEPAGES);
1419 (*mapcount)--;
1421 pte_unmap_unlock(pte - 1, ptl);
1422 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1423 if (locked_vma)
1424 up_read(&vma->vm_mm->mmap_sem);
1425 return ret;
1428 bool is_vma_temporary_stack(struct vm_area_struct *vma)
1430 int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP);
1432 if (!maybe_stack)
1433 return false;
1435 if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) ==
1436 VM_STACK_INCOMPLETE_SETUP)
1437 return true;
1439 return false;
1443 * try_to_unmap_anon - unmap or unlock anonymous page using the object-based
1444 * rmap method
1445 * @page: the page to unmap/unlock
1446 * @flags: action and flags
1448 * Find all the mappings of a page using the mapping pointer and the vma chains
1449 * contained in the anon_vma struct it points to.
1451 * This function is only called from try_to_unmap/try_to_munlock for
1452 * anonymous pages.
1453 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1454 * where the page was found will be held for write. So, we won't recheck
1455 * vm_flags for that VMA. That should be OK, because that vma shouldn't be
1456 * 'LOCKED.
1458 static int try_to_unmap_anon(struct page *page, enum ttu_flags flags)
1460 struct anon_vma *anon_vma;
1461 pgoff_t pgoff;
1462 struct anon_vma_chain *avc;
1463 int ret = SWAP_AGAIN;
1465 anon_vma = page_lock_anon_vma_read(page);
1466 if (!anon_vma)
1467 return ret;
1469 pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1470 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1471 struct vm_area_struct *vma = avc->vma;
1472 unsigned long address;
1475 * During exec, a temporary VMA is setup and later moved.
1476 * The VMA is moved under the anon_vma lock but not the
1477 * page tables leading to a race where migration cannot
1478 * find the migration ptes. Rather than increasing the
1479 * locking requirements of exec(), migration skips
1480 * temporary VMAs until after exec() completes.
1482 if (IS_ENABLED(CONFIG_MIGRATION) && (flags & TTU_MIGRATION) &&
1483 is_vma_temporary_stack(vma))
1484 continue;
1486 address = vma_address(page, vma);
1487 ret = try_to_unmap_one(page, vma, address, flags);
1488 if (ret != SWAP_AGAIN || !page_mapped(page))
1489 break;
1492 page_unlock_anon_vma_read(anon_vma);
1493 return ret;
1497 * try_to_unmap_file - unmap/unlock file page using the object-based rmap method
1498 * @page: the page to unmap/unlock
1499 * @flags: action and flags
1501 * Find all the mappings of a page using the mapping pointer and the vma chains
1502 * contained in the address_space struct it points to.
1504 * This function is only called from try_to_unmap/try_to_munlock for
1505 * object-based pages.
1506 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1507 * where the page was found will be held for write. So, we won't recheck
1508 * vm_flags for that VMA. That should be OK, because that vma shouldn't be
1509 * 'LOCKED.
1511 static int try_to_unmap_file(struct page *page, enum ttu_flags flags)
1513 struct address_space *mapping = page->mapping;
1514 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1515 struct vm_area_struct *vma;
1516 int ret = SWAP_AGAIN;
1517 unsigned long cursor;
1518 unsigned long max_nl_cursor = 0;
1519 unsigned long max_nl_size = 0;
1520 unsigned int mapcount;
1522 if (PageHuge(page))
1523 pgoff = page->index << compound_order(page);
1525 mutex_lock(&mapping->i_mmap_mutex);
1526 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
1527 unsigned long address = vma_address(page, vma);
1528 ret = try_to_unmap_one(page, vma, address, flags);
1529 if (ret != SWAP_AGAIN || !page_mapped(page))
1530 goto out;
1533 if (list_empty(&mapping->i_mmap_nonlinear))
1534 goto out;
1537 * We don't bother to try to find the munlocked page in nonlinears.
1538 * It's costly. Instead, later, page reclaim logic may call
1539 * try_to_unmap(TTU_MUNLOCK) and recover PG_mlocked lazily.
1541 if (TTU_ACTION(flags) == TTU_MUNLOCK)
1542 goto out;
1544 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
1545 shared.nonlinear) {
1546 cursor = (unsigned long) vma->vm_private_data;
1547 if (cursor > max_nl_cursor)
1548 max_nl_cursor = cursor;
1549 cursor = vma->vm_end - vma->vm_start;
1550 if (cursor > max_nl_size)
1551 max_nl_size = cursor;
1554 if (max_nl_size == 0) { /* all nonlinears locked or reserved ? */
1555 ret = SWAP_FAIL;
1556 goto out;
1560 * We don't try to search for this page in the nonlinear vmas,
1561 * and page_referenced wouldn't have found it anyway. Instead
1562 * just walk the nonlinear vmas trying to age and unmap some.
1563 * The mapcount of the page we came in with is irrelevant,
1564 * but even so use it as a guide to how hard we should try?
1566 mapcount = page_mapcount(page);
1567 if (!mapcount)
1568 goto out;
1569 cond_resched();
1571 max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK;
1572 if (max_nl_cursor == 0)
1573 max_nl_cursor = CLUSTER_SIZE;
1575 do {
1576 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
1577 shared.nonlinear) {
1578 cursor = (unsigned long) vma->vm_private_data;
1579 while ( cursor < max_nl_cursor &&
1580 cursor < vma->vm_end - vma->vm_start) {
1581 if (try_to_unmap_cluster(cursor, &mapcount,
1582 vma, page) == SWAP_MLOCK)
1583 ret = SWAP_MLOCK;
1584 cursor += CLUSTER_SIZE;
1585 vma->vm_private_data = (void *) cursor;
1586 if ((int)mapcount <= 0)
1587 goto out;
1589 vma->vm_private_data = (void *) max_nl_cursor;
1591 cond_resched();
1592 max_nl_cursor += CLUSTER_SIZE;
1593 } while (max_nl_cursor <= max_nl_size);
1596 * Don't loop forever (perhaps all the remaining pages are
1597 * in locked vmas). Reset cursor on all unreserved nonlinear
1598 * vmas, now forgetting on which ones it had fallen behind.
1600 list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.nonlinear)
1601 vma->vm_private_data = NULL;
1602 out:
1603 mutex_unlock(&mapping->i_mmap_mutex);
1604 return ret;
1608 * try_to_unmap - try to remove all page table mappings to a page
1609 * @page: the page to get unmapped
1610 * @flags: action and flags
1612 * Tries to remove all the page table entries which are mapping this
1613 * page, used in the pageout path. Caller must hold the page lock.
1614 * Return values are:
1616 * SWAP_SUCCESS - we succeeded in removing all mappings
1617 * SWAP_AGAIN - we missed a mapping, try again later
1618 * SWAP_FAIL - the page is unswappable
1619 * SWAP_MLOCK - page is mlocked.
1621 int try_to_unmap(struct page *page, enum ttu_flags flags)
1623 int ret;
1625 BUG_ON(!PageLocked(page));
1626 VM_BUG_ON(!PageHuge(page) && PageTransHuge(page));
1628 if (unlikely(PageKsm(page)))
1629 ret = try_to_unmap_ksm(page, flags);
1630 else if (PageAnon(page))
1631 ret = try_to_unmap_anon(page, flags);
1632 else
1633 ret = try_to_unmap_file(page, flags);
1634 if (ret != SWAP_MLOCK && !page_mapped(page))
1635 ret = SWAP_SUCCESS;
1636 return ret;
1640 * try_to_munlock - try to munlock a page
1641 * @page: the page to be munlocked
1643 * Called from munlock code. Checks all of the VMAs mapping the page
1644 * to make sure nobody else has this page mlocked. The page will be
1645 * returned with PG_mlocked cleared if no other vmas have it mlocked.
1647 * Return values are:
1649 * SWAP_AGAIN - no vma is holding page mlocked, or,
1650 * SWAP_AGAIN - page mapped in mlocked vma -- couldn't acquire mmap sem
1651 * SWAP_FAIL - page cannot be located at present
1652 * SWAP_MLOCK - page is now mlocked.
1654 int try_to_munlock(struct page *page)
1656 VM_BUG_ON(!PageLocked(page) || PageLRU(page));
1658 if (unlikely(PageKsm(page)))
1659 return try_to_unmap_ksm(page, TTU_MUNLOCK);
1660 else if (PageAnon(page))
1661 return try_to_unmap_anon(page, TTU_MUNLOCK);
1662 else
1663 return try_to_unmap_file(page, TTU_MUNLOCK);
1666 void __put_anon_vma(struct anon_vma *anon_vma)
1668 struct anon_vma *root = anon_vma->root;
1670 if (root != anon_vma && atomic_dec_and_test(&root->refcount))
1671 anon_vma_free(root);
1673 anon_vma_free(anon_vma);
1676 #ifdef CONFIG_MIGRATION
1678 * rmap_walk() and its helpers rmap_walk_anon() and rmap_walk_file():
1679 * Called by migrate.c to remove migration ptes, but might be used more later.
1681 static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *,
1682 struct vm_area_struct *, unsigned long, void *), void *arg)
1684 struct anon_vma *anon_vma;
1685 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1686 struct anon_vma_chain *avc;
1687 int ret = SWAP_AGAIN;
1690 * Note: remove_migration_ptes() cannot use page_lock_anon_vma_read()
1691 * because that depends on page_mapped(); but not all its usages
1692 * are holding mmap_sem. Users without mmap_sem are required to
1693 * take a reference count to prevent the anon_vma disappearing
1695 anon_vma = page_anon_vma(page);
1696 if (!anon_vma)
1697 return ret;
1698 anon_vma_lock_read(anon_vma);
1699 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1700 struct vm_area_struct *vma = avc->vma;
1701 unsigned long address = vma_address(page, vma);
1702 ret = rmap_one(page, vma, address, arg);
1703 if (ret != SWAP_AGAIN)
1704 break;
1706 anon_vma_unlock_read(anon_vma);
1707 return ret;
1710 static int rmap_walk_file(struct page *page, int (*rmap_one)(struct page *,
1711 struct vm_area_struct *, unsigned long, void *), void *arg)
1713 struct address_space *mapping = page->mapping;
1714 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1715 struct vm_area_struct *vma;
1716 int ret = SWAP_AGAIN;
1718 if (!mapping)
1719 return ret;
1720 mutex_lock(&mapping->i_mmap_mutex);
1721 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
1722 unsigned long address = vma_address(page, vma);
1723 ret = rmap_one(page, vma, address, arg);
1724 if (ret != SWAP_AGAIN)
1725 break;
1728 * No nonlinear handling: being always shared, nonlinear vmas
1729 * never contain migration ptes. Decide what to do about this
1730 * limitation to linear when we need rmap_walk() on nonlinear.
1732 mutex_unlock(&mapping->i_mmap_mutex);
1733 return ret;
1736 int rmap_walk(struct page *page, int (*rmap_one)(struct page *,
1737 struct vm_area_struct *, unsigned long, void *), void *arg)
1739 VM_BUG_ON(!PageLocked(page));
1741 if (unlikely(PageKsm(page)))
1742 return rmap_walk_ksm(page, rmap_one, arg);
1743 else if (PageAnon(page))
1744 return rmap_walk_anon(page, rmap_one, arg);
1745 else
1746 return rmap_walk_file(page, rmap_one, arg);
1748 #endif /* CONFIG_MIGRATION */
1750 #ifdef CONFIG_HUGETLB_PAGE
1752 * The following three functions are for anonymous (private mapped) hugepages.
1753 * Unlike common anonymous pages, anonymous hugepages have no accounting code
1754 * and no lru code, because we handle hugepages differently from common pages.
1756 static void __hugepage_set_anon_rmap(struct page *page,
1757 struct vm_area_struct *vma, unsigned long address, int exclusive)
1759 struct anon_vma *anon_vma = vma->anon_vma;
1761 BUG_ON(!anon_vma);
1763 if (PageAnon(page))
1764 return;
1765 if (!exclusive)
1766 anon_vma = anon_vma->root;
1768 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1769 page->mapping = (struct address_space *) anon_vma;
1770 page->index = linear_page_index(vma, address);
1773 void hugepage_add_anon_rmap(struct page *page,
1774 struct vm_area_struct *vma, unsigned long address)
1776 struct anon_vma *anon_vma = vma->anon_vma;
1777 int first;
1779 BUG_ON(!PageLocked(page));
1780 BUG_ON(!anon_vma);
1781 /* address might be in next vma when migration races vma_adjust */
1782 first = atomic_inc_and_test(&page->_mapcount);
1783 if (first)
1784 __hugepage_set_anon_rmap(page, vma, address, 0);
1787 void hugepage_add_new_anon_rmap(struct page *page,
1788 struct vm_area_struct *vma, unsigned long address)
1790 BUG_ON(address < vma->vm_start || address >= vma->vm_end);
1791 atomic_set(&page->_mapcount, 0);
1792 __hugepage_set_anon_rmap(page, vma, address, 1);
1794 #endif /* CONFIG_HUGETLB_PAGE */