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)
25 * page->flags PG_locked (lock_page)
26 * mapping->i_mmap_mutex
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->mutex,mapping->i_mutex (memory_failure, collect_procs_anon)
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/module.h>
55 #include <linux/memcontrol.h>
56 #include <linux/mmu_notifier.h>
57 #include <linux/migrate.h>
58 #include <linux/hugetlb.h>
60 #include <asm/tlbflush.h>
64 static struct kmem_cache *anon_vma_cachep;
65 static struct kmem_cache *anon_vma_chain_cachep;
67 static inline struct anon_vma *anon_vma_alloc(void)
69 struct anon_vma *anon_vma;
71 anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL);
73 atomic_set(&anon_vma->refcount, 1);
75 * Initialise the anon_vma root to point to itself. If called
76 * from fork, the root will be reset to the parents anon_vma.
78 anon_vma->root = anon_vma;
84 static inline void anon_vma_free(struct anon_vma *anon_vma)
86 VM_BUG_ON(atomic_read(&anon_vma->refcount));
89 * Synchronize against page_lock_anon_vma() such that
90 * we can safely hold the lock without the anon_vma getting
93 * Relies on the full mb implied by the atomic_dec_and_test() from
94 * put_anon_vma() against the acquire barrier implied by
95 * mutex_trylock() from page_lock_anon_vma(). This orders:
97 * page_lock_anon_vma() VS put_anon_vma()
98 * mutex_trylock() atomic_dec_and_test()
100 * atomic_read() mutex_is_locked()
102 * LOCK should suffice since the actual taking of the lock must
103 * happen _before_ what follows.
105 if (mutex_is_locked(&anon_vma->root->mutex)) {
106 anon_vma_lock(anon_vma);
107 anon_vma_unlock(anon_vma);
110 kmem_cache_free(anon_vma_cachep, anon_vma);
113 static inline struct anon_vma_chain *anon_vma_chain_alloc(gfp_t gfp)
115 return kmem_cache_alloc(anon_vma_chain_cachep, gfp);
118 static void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain)
120 kmem_cache_free(anon_vma_chain_cachep, anon_vma_chain);
124 * anon_vma_prepare - attach an anon_vma to a memory region
125 * @vma: the memory region in question
127 * This makes sure the memory mapping described by 'vma' has
128 * an 'anon_vma' attached to it, so that we can associate the
129 * anonymous pages mapped into it with that anon_vma.
131 * The common case will be that we already have one, but if
132 * not we either need to find an adjacent mapping that we
133 * can re-use the anon_vma from (very common when the only
134 * reason for splitting a vma has been mprotect()), or we
135 * allocate a new one.
137 * Anon-vma allocations are very subtle, because we may have
138 * optimistically looked up an anon_vma in page_lock_anon_vma()
139 * and that may actually touch the spinlock even in the newly
140 * allocated vma (it depends on RCU to make sure that the
141 * anon_vma isn't actually destroyed).
143 * As a result, we need to do proper anon_vma locking even
144 * for the new allocation. At the same time, we do not want
145 * to do any locking for the common case of already having
148 * This must be called with the mmap_sem held for reading.
150 int anon_vma_prepare(struct vm_area_struct *vma)
152 struct anon_vma *anon_vma = vma->anon_vma;
153 struct anon_vma_chain *avc;
156 if (unlikely(!anon_vma)) {
157 struct mm_struct *mm = vma->vm_mm;
158 struct anon_vma *allocated;
160 avc = anon_vma_chain_alloc(GFP_KERNEL);
164 anon_vma = find_mergeable_anon_vma(vma);
167 anon_vma = anon_vma_alloc();
168 if (unlikely(!anon_vma))
169 goto out_enomem_free_avc;
170 allocated = anon_vma;
173 anon_vma_lock(anon_vma);
174 /* page_table_lock to protect against threads */
175 spin_lock(&mm->page_table_lock);
176 if (likely(!vma->anon_vma)) {
177 vma->anon_vma = anon_vma;
178 avc->anon_vma = anon_vma;
180 list_add(&avc->same_vma, &vma->anon_vma_chain);
181 list_add_tail(&avc->same_anon_vma, &anon_vma->head);
185 spin_unlock(&mm->page_table_lock);
186 anon_vma_unlock(anon_vma);
188 if (unlikely(allocated))
189 put_anon_vma(allocated);
191 anon_vma_chain_free(avc);
196 anon_vma_chain_free(avc);
202 * This is a useful helper function for locking the anon_vma root as
203 * we traverse the vma->anon_vma_chain, looping over anon_vma's that
206 * Such anon_vma's should have the same root, so you'd expect to see
207 * just a single mutex_lock for the whole traversal.
209 static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma)
211 struct anon_vma *new_root = anon_vma->root;
212 if (new_root != root) {
213 if (WARN_ON_ONCE(root))
214 mutex_unlock(&root->mutex);
216 mutex_lock(&root->mutex);
221 static inline void unlock_anon_vma_root(struct anon_vma *root)
224 mutex_unlock(&root->mutex);
227 static void anon_vma_chain_link(struct vm_area_struct *vma,
228 struct anon_vma_chain *avc,
229 struct anon_vma *anon_vma)
232 avc->anon_vma = anon_vma;
233 list_add(&avc->same_vma, &vma->anon_vma_chain);
236 * It's critical to add new vmas to the tail of the anon_vma,
237 * see comment in huge_memory.c:__split_huge_page().
239 list_add_tail(&avc->same_anon_vma, &anon_vma->head);
243 * Attach the anon_vmas from src to dst.
244 * Returns 0 on success, -ENOMEM on failure.
246 int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
248 struct anon_vma_chain *avc, *pavc;
249 struct anon_vma *root = NULL;
251 list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
252 struct anon_vma *anon_vma;
254 avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN);
255 if (unlikely(!avc)) {
256 unlock_anon_vma_root(root);
258 avc = anon_vma_chain_alloc(GFP_KERNEL);
262 anon_vma = pavc->anon_vma;
263 root = lock_anon_vma_root(root, anon_vma);
264 anon_vma_chain_link(dst, avc, anon_vma);
266 unlock_anon_vma_root(root);
270 unlink_anon_vmas(dst);
275 * Attach vma to its own anon_vma, as well as to the anon_vmas that
276 * the corresponding VMA in the parent process is attached to.
277 * Returns 0 on success, non-zero on failure.
279 int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
281 struct anon_vma_chain *avc;
282 struct anon_vma *anon_vma;
284 /* Don't bother if the parent process has no anon_vma here. */
289 * First, attach the new VMA to the parent VMA's anon_vmas,
290 * so rmap can find non-COWed pages in child processes.
292 if (anon_vma_clone(vma, pvma))
295 /* Then add our own anon_vma. */
296 anon_vma = anon_vma_alloc();
299 avc = anon_vma_chain_alloc(GFP_KERNEL);
301 goto out_error_free_anon_vma;
304 * The root anon_vma's spinlock is the lock actually used when we
305 * lock any of the anon_vmas in this anon_vma tree.
307 anon_vma->root = pvma->anon_vma->root;
309 * With refcounts, an anon_vma can stay around longer than the
310 * process it belongs to. The root anon_vma needs to be pinned until
311 * this anon_vma is freed, because the lock lives in the root.
313 get_anon_vma(anon_vma->root);
314 /* Mark this anon_vma as the one where our new (COWed) pages go. */
315 vma->anon_vma = anon_vma;
316 anon_vma_lock(anon_vma);
317 anon_vma_chain_link(vma, avc, anon_vma);
318 anon_vma_unlock(anon_vma);
322 out_error_free_anon_vma:
323 put_anon_vma(anon_vma);
325 unlink_anon_vmas(vma);
329 void unlink_anon_vmas(struct vm_area_struct *vma)
331 struct anon_vma_chain *avc, *next;
332 struct anon_vma *root = NULL;
335 * Unlink each anon_vma chained to the VMA. This list is ordered
336 * from newest to oldest, ensuring the root anon_vma gets freed last.
338 list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
339 struct anon_vma *anon_vma = avc->anon_vma;
341 root = lock_anon_vma_root(root, anon_vma);
342 list_del(&avc->same_anon_vma);
345 * Leave empty anon_vmas on the list - we'll need
346 * to free them outside the lock.
348 if (list_empty(&anon_vma->head))
351 list_del(&avc->same_vma);
352 anon_vma_chain_free(avc);
354 unlock_anon_vma_root(root);
357 * Iterate the list once more, it now only contains empty and unlinked
358 * anon_vmas, destroy them. Could not do before due to __put_anon_vma()
359 * needing to acquire the anon_vma->root->mutex.
361 list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
362 struct anon_vma *anon_vma = avc->anon_vma;
364 put_anon_vma(anon_vma);
366 list_del(&avc->same_vma);
367 anon_vma_chain_free(avc);
371 static void anon_vma_ctor(void *data)
373 struct anon_vma *anon_vma = data;
375 mutex_init(&anon_vma->mutex);
376 atomic_set(&anon_vma->refcount, 0);
377 INIT_LIST_HEAD(&anon_vma->head);
380 void __init anon_vma_init(void)
382 anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
383 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor);
384 anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain, SLAB_PANIC);
388 * Getting a lock on a stable anon_vma from a page off the LRU is tricky!
390 * Since there is no serialization what so ever against page_remove_rmap()
391 * the best this function can do is return a locked anon_vma that might
392 * have been relevant to this page.
394 * The page might have been remapped to a different anon_vma or the anon_vma
395 * returned may already be freed (and even reused).
397 * In case it was remapped to a different anon_vma, the new anon_vma will be a
398 * child of the old anon_vma, and the anon_vma lifetime rules will therefore
399 * ensure that any anon_vma obtained from the page will still be valid for as
400 * long as we observe page_mapped() [ hence all those page_mapped() tests ].
402 * All users of this function must be very careful when walking the anon_vma
403 * chain and verify that the page in question is indeed mapped in it
404 * [ something equivalent to page_mapped_in_vma() ].
406 * Since anon_vma's slab is DESTROY_BY_RCU and we know from page_remove_rmap()
407 * that the anon_vma pointer from page->mapping is valid if there is a
408 * mapcount, we can dereference the anon_vma after observing those.
410 struct anon_vma *page_get_anon_vma(struct page *page)
412 struct anon_vma *anon_vma = NULL;
413 unsigned long anon_mapping;
416 anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping);
417 if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
419 if (!page_mapped(page))
422 anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
423 if (!atomic_inc_not_zero(&anon_vma->refcount)) {
429 * If this page is still mapped, then its anon_vma cannot have been
430 * freed. But if it has been unmapped, we have no security against the
431 * anon_vma structure being freed and reused (for another anon_vma:
432 * SLAB_DESTROY_BY_RCU guarantees that - so the atomic_inc_not_zero()
433 * above cannot corrupt).
435 if (!page_mapped(page)) {
436 put_anon_vma(anon_vma);
446 * Similar to page_get_anon_vma() except it locks the anon_vma.
448 * Its a little more complex as it tries to keep the fast path to a single
449 * atomic op -- the trylock. If we fail the trylock, we fall back to getting a
450 * reference like with page_get_anon_vma() and then block on the mutex.
452 struct anon_vma *page_lock_anon_vma(struct page *page)
454 struct anon_vma *anon_vma = NULL;
455 struct anon_vma *root_anon_vma;
456 unsigned long anon_mapping;
459 anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping);
460 if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
462 if (!page_mapped(page))
465 anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
466 root_anon_vma = ACCESS_ONCE(anon_vma->root);
467 if (mutex_trylock(&root_anon_vma->mutex)) {
469 * If the page is still mapped, then this anon_vma is still
470 * its anon_vma, and holding the mutex ensures that it will
471 * not go away, see anon_vma_free().
473 if (!page_mapped(page)) {
474 mutex_unlock(&root_anon_vma->mutex);
480 /* trylock failed, we got to sleep */
481 if (!atomic_inc_not_zero(&anon_vma->refcount)) {
486 if (!page_mapped(page)) {
487 put_anon_vma(anon_vma);
492 /* we pinned the anon_vma, its safe to sleep */
494 anon_vma_lock(anon_vma);
496 if (atomic_dec_and_test(&anon_vma->refcount)) {
498 * Oops, we held the last refcount, release the lock
499 * and bail -- can't simply use put_anon_vma() because
500 * we'll deadlock on the anon_vma_lock() recursion.
502 anon_vma_unlock(anon_vma);
503 __put_anon_vma(anon_vma);
514 void page_unlock_anon_vma(struct anon_vma *anon_vma)
516 anon_vma_unlock(anon_vma);
520 * At what user virtual address is page expected in @vma?
521 * Returns virtual address or -EFAULT if page's index/offset is not
522 * within the range mapped the @vma.
525 vma_address(struct page *page, struct vm_area_struct *vma)
527 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
528 unsigned long address;
530 if (unlikely(is_vm_hugetlb_page(vma)))
531 pgoff = page->index << huge_page_order(page_hstate(page));
532 address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
533 if (unlikely(address < vma->vm_start || address >= vma->vm_end)) {
534 /* page should be within @vma mapping range */
541 * At what user virtual address is page expected in vma?
542 * Caller should check the page is actually part of the vma.
544 unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
546 if (PageAnon(page)) {
547 struct anon_vma *page__anon_vma = page_anon_vma(page);
549 * Note: swapoff's unuse_vma() is more efficient with this
550 * check, and needs it to match anon_vma when KSM is active.
552 if (!vma->anon_vma || !page__anon_vma ||
553 vma->anon_vma->root != page__anon_vma->root)
555 } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
557 vma->vm_file->f_mapping != page->mapping)
561 return vma_address(page, vma);
565 * Check that @page is mapped at @address into @mm.
567 * If @sync is false, page_check_address may perform a racy check to avoid
568 * the page table lock when the pte is not present (helpful when reclaiming
569 * highly shared pages).
571 * On success returns with pte mapped and locked.
573 pte_t *__page_check_address(struct page *page, struct mm_struct *mm,
574 unsigned long address, spinlock_t **ptlp, int sync)
582 if (unlikely(PageHuge(page))) {
583 pte = huge_pte_offset(mm, address);
584 ptl = &mm->page_table_lock;
588 pgd = pgd_offset(mm, address);
589 if (!pgd_present(*pgd))
592 pud = pud_offset(pgd, address);
593 if (!pud_present(*pud))
596 pmd = pmd_offset(pud, address);
597 if (!pmd_present(*pmd))
599 if (pmd_trans_huge(*pmd))
602 pte = pte_offset_map(pmd, address);
603 /* Make a quick check before getting the lock */
604 if (!sync && !pte_present(*pte)) {
609 ptl = pte_lockptr(mm, pmd);
612 if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) {
616 pte_unmap_unlock(pte, ptl);
621 * page_mapped_in_vma - check whether a page is really mapped in a VMA
622 * @page: the page to test
623 * @vma: the VMA to test
625 * Returns 1 if the page is mapped into the page tables of the VMA, 0
626 * if the page is not mapped into the page tables of this VMA. Only
627 * valid for normal file or anonymous VMAs.
629 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
631 unsigned long address;
635 address = vma_address(page, vma);
636 if (address == -EFAULT) /* out of vma range */
638 pte = page_check_address(page, vma->vm_mm, address, &ptl, 1);
639 if (!pte) /* the page is not in this mm */
641 pte_unmap_unlock(pte, ptl);
647 * Subfunctions of page_referenced: page_referenced_one called
648 * repeatedly from either page_referenced_anon or page_referenced_file.
650 int page_referenced_one(struct page *page, struct vm_area_struct *vma,
651 unsigned long address, unsigned int *mapcount,
652 unsigned long *vm_flags)
654 struct mm_struct *mm = vma->vm_mm;
657 if (unlikely(PageTransHuge(page))) {
660 spin_lock(&mm->page_table_lock);
662 * rmap might return false positives; we must filter
663 * these out using page_check_address_pmd().
665 pmd = page_check_address_pmd(page, mm, address,
666 PAGE_CHECK_ADDRESS_PMD_FLAG);
668 spin_unlock(&mm->page_table_lock);
672 if (vma->vm_flags & VM_LOCKED) {
673 spin_unlock(&mm->page_table_lock);
674 *mapcount = 0; /* break early from loop */
675 *vm_flags |= VM_LOCKED;
679 /* go ahead even if the pmd is pmd_trans_splitting() */
680 if (pmdp_clear_flush_young_notify(vma, address, pmd))
682 spin_unlock(&mm->page_table_lock);
688 * rmap might return false positives; we must filter
689 * these out using page_check_address().
691 pte = page_check_address(page, mm, address, &ptl, 0);
695 if (vma->vm_flags & VM_LOCKED) {
696 pte_unmap_unlock(pte, ptl);
697 *mapcount = 0; /* break early from loop */
698 *vm_flags |= VM_LOCKED;
702 if (ptep_clear_flush_young_notify(vma, address, pte)) {
704 * Don't treat a reference through a sequentially read
705 * mapping as such. If the page has been used in
706 * another mapping, we will catch it; if this other
707 * mapping is already gone, the unmap path will have
708 * set PG_referenced or activated the page.
710 if (likely(!VM_SequentialReadHint(vma)))
713 pte_unmap_unlock(pte, ptl);
716 /* Pretend the page is referenced if the task has the
717 swap token and is in the middle of a page fault. */
718 if (mm != current->mm && has_swap_token(mm) &&
719 rwsem_is_locked(&mm->mmap_sem))
725 *vm_flags |= vma->vm_flags;
730 static int page_referenced_anon(struct page *page,
731 struct mem_cgroup *mem_cont,
732 unsigned long *vm_flags)
734 unsigned int mapcount;
735 struct anon_vma *anon_vma;
736 struct anon_vma_chain *avc;
739 anon_vma = page_lock_anon_vma(page);
743 mapcount = page_mapcount(page);
744 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
745 struct vm_area_struct *vma = avc->vma;
746 unsigned long address = vma_address(page, vma);
747 if (address == -EFAULT)
750 * If we are reclaiming on behalf of a cgroup, skip
751 * counting on behalf of references from different
754 if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont))
756 referenced += page_referenced_one(page, vma, address,
757 &mapcount, vm_flags);
762 page_unlock_anon_vma(anon_vma);
767 * page_referenced_file - referenced check for object-based rmap
768 * @page: the page we're checking references on.
769 * @mem_cont: target memory controller
770 * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
772 * For an object-based mapped page, find all the places it is mapped and
773 * check/clear the referenced flag. This is done by following the page->mapping
774 * pointer, then walking the chain of vmas it holds. It returns the number
775 * of references it found.
777 * This function is only called from page_referenced for object-based pages.
779 static int page_referenced_file(struct page *page,
780 struct mem_cgroup *mem_cont,
781 unsigned long *vm_flags)
783 unsigned int mapcount;
784 struct address_space *mapping = page->mapping;
785 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
786 struct vm_area_struct *vma;
787 struct prio_tree_iter iter;
791 * The caller's checks on page->mapping and !PageAnon have made
792 * sure that this is a file page: the check for page->mapping
793 * excludes the case just before it gets set on an anon page.
795 BUG_ON(PageAnon(page));
798 * The page lock not only makes sure that page->mapping cannot
799 * suddenly be NULLified by truncation, it makes sure that the
800 * structure at mapping cannot be freed and reused yet,
801 * so we can safely take mapping->i_mmap_mutex.
803 BUG_ON(!PageLocked(page));
805 mutex_lock(&mapping->i_mmap_mutex);
808 * i_mmap_mutex does not stabilize mapcount at all, but mapcount
809 * is more likely to be accurate if we note it after spinning.
811 mapcount = page_mapcount(page);
813 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
814 unsigned long address = vma_address(page, vma);
815 if (address == -EFAULT)
818 * If we are reclaiming on behalf of a cgroup, skip
819 * counting on behalf of references from different
822 if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont))
824 referenced += page_referenced_one(page, vma, address,
825 &mapcount, vm_flags);
830 mutex_unlock(&mapping->i_mmap_mutex);
835 * page_referenced - test if the page was referenced
836 * @page: the page to test
837 * @is_locked: caller holds lock on the page
838 * @mem_cont: target memory controller
839 * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
841 * Quick test_and_clear_referenced for all mappings to a page,
842 * returns the number of ptes which referenced the page.
844 int page_referenced(struct page *page,
846 struct mem_cgroup *mem_cont,
847 unsigned long *vm_flags)
853 if (page_mapped(page) && page_rmapping(page)) {
854 if (!is_locked && (!PageAnon(page) || PageKsm(page))) {
855 we_locked = trylock_page(page);
861 if (unlikely(PageKsm(page)))
862 referenced += page_referenced_ksm(page, mem_cont,
864 else if (PageAnon(page))
865 referenced += page_referenced_anon(page, mem_cont,
867 else if (page->mapping)
868 referenced += page_referenced_file(page, mem_cont,
873 if (page_test_and_clear_young(page_to_pfn(page)))
880 static int page_mkclean_one(struct page *page, struct vm_area_struct *vma,
881 unsigned long address)
883 struct mm_struct *mm = vma->vm_mm;
888 pte = page_check_address(page, mm, address, &ptl, 1);
892 if (pte_dirty(*pte) || pte_write(*pte)) {
895 flush_cache_page(vma, address, pte_pfn(*pte));
896 entry = ptep_clear_flush_notify(vma, address, pte);
897 entry = pte_wrprotect(entry);
898 entry = pte_mkclean(entry);
899 set_pte_at(mm, address, pte, entry);
903 pte_unmap_unlock(pte, ptl);
908 static int page_mkclean_file(struct address_space *mapping, struct page *page)
910 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
911 struct vm_area_struct *vma;
912 struct prio_tree_iter iter;
915 BUG_ON(PageAnon(page));
917 mutex_lock(&mapping->i_mmap_mutex);
918 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
919 if (vma->vm_flags & VM_SHARED) {
920 unsigned long address = vma_address(page, vma);
921 if (address == -EFAULT)
923 ret += page_mkclean_one(page, vma, address);
926 mutex_unlock(&mapping->i_mmap_mutex);
930 int page_mkclean(struct page *page)
934 BUG_ON(!PageLocked(page));
936 if (page_mapped(page)) {
937 struct address_space *mapping = page_mapping(page);
939 ret = page_mkclean_file(mapping, page);
940 if (page_test_and_clear_dirty(page_to_pfn(page), 1))
947 EXPORT_SYMBOL_GPL(page_mkclean);
950 * page_move_anon_rmap - move a page to our anon_vma
951 * @page: the page to move to our anon_vma
952 * @vma: the vma the page belongs to
953 * @address: the user virtual address mapped
955 * When a page belongs exclusively to one process after a COW event,
956 * that page can be moved into the anon_vma that belongs to just that
957 * process, so the rmap code will not search the parent or sibling
960 void page_move_anon_rmap(struct page *page,
961 struct vm_area_struct *vma, unsigned long address)
963 struct anon_vma *anon_vma = vma->anon_vma;
965 VM_BUG_ON(!PageLocked(page));
966 VM_BUG_ON(!anon_vma);
967 VM_BUG_ON(page->index != linear_page_index(vma, address));
969 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
970 page->mapping = (struct address_space *) anon_vma;
974 * __page_set_anon_rmap - set up new anonymous rmap
975 * @page: Page to add to rmap
976 * @vma: VM area to add page to.
977 * @address: User virtual address of the mapping
978 * @exclusive: the page is exclusively owned by the current process
980 static void __page_set_anon_rmap(struct page *page,
981 struct vm_area_struct *vma, unsigned long address, int exclusive)
983 struct anon_vma *anon_vma = vma->anon_vma;
991 * If the page isn't exclusively mapped into this vma,
992 * we must use the _oldest_ possible anon_vma for the
996 anon_vma = anon_vma->root;
998 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
999 page->mapping = (struct address_space *) anon_vma;
1000 page->index = linear_page_index(vma, address);
1004 * __page_check_anon_rmap - sanity check anonymous rmap addition
1005 * @page: the page to add the mapping to
1006 * @vma: the vm area in which the mapping is added
1007 * @address: the user virtual address mapped
1009 static void __page_check_anon_rmap(struct page *page,
1010 struct vm_area_struct *vma, unsigned long address)
1012 #ifdef CONFIG_DEBUG_VM
1014 * The page's anon-rmap details (mapping and index) are guaranteed to
1015 * be set up correctly at this point.
1017 * We have exclusion against page_add_anon_rmap because the caller
1018 * always holds the page locked, except if called from page_dup_rmap,
1019 * in which case the page is already known to be setup.
1021 * We have exclusion against page_add_new_anon_rmap because those pages
1022 * are initially only visible via the pagetables, and the pte is locked
1023 * over the call to page_add_new_anon_rmap.
1025 BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root);
1026 BUG_ON(page->index != linear_page_index(vma, address));
1031 * page_add_anon_rmap - add pte mapping to an anonymous page
1032 * @page: the page to add the mapping to
1033 * @vma: the vm area in which the mapping is added
1034 * @address: the user virtual address mapped
1036 * The caller needs to hold the pte lock, and the page must be locked in
1037 * the anon_vma case: to serialize mapping,index checking after setting,
1038 * and to ensure that PageAnon is not being upgraded racily to PageKsm
1039 * (but PageKsm is never downgraded to PageAnon).
1041 void page_add_anon_rmap(struct page *page,
1042 struct vm_area_struct *vma, unsigned long address)
1044 do_page_add_anon_rmap(page, vma, address, 0);
1048 * Special version of the above for do_swap_page, which often runs
1049 * into pages that are exclusively owned by the current process.
1050 * Everybody else should continue to use page_add_anon_rmap above.
1052 void do_page_add_anon_rmap(struct page *page,
1053 struct vm_area_struct *vma, unsigned long address, int exclusive)
1055 int first = atomic_inc_and_test(&page->_mapcount);
1057 if (!PageTransHuge(page))
1058 __inc_zone_page_state(page, NR_ANON_PAGES);
1060 __inc_zone_page_state(page,
1061 NR_ANON_TRANSPARENT_HUGEPAGES);
1063 if (unlikely(PageKsm(page)))
1066 VM_BUG_ON(!PageLocked(page));
1067 /* address might be in next vma when migration races vma_adjust */
1069 __page_set_anon_rmap(page, vma, address, exclusive);
1071 __page_check_anon_rmap(page, vma, address);
1075 * page_add_new_anon_rmap - add pte mapping to a new anonymous page
1076 * @page: the page to add the mapping to
1077 * @vma: the vm area in which the mapping is added
1078 * @address: the user virtual address mapped
1080 * Same as page_add_anon_rmap but must only be called on *new* pages.
1081 * This means the inc-and-test can be bypassed.
1082 * Page does not have to be locked.
1084 void page_add_new_anon_rmap(struct page *page,
1085 struct vm_area_struct *vma, unsigned long address)
1087 VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
1088 SetPageSwapBacked(page);
1089 atomic_set(&page->_mapcount, 0); /* increment count (starts at -1) */
1090 if (!PageTransHuge(page))
1091 __inc_zone_page_state(page, NR_ANON_PAGES);
1093 __inc_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
1094 __page_set_anon_rmap(page, vma, address, 1);
1095 if (page_evictable(page, vma))
1096 lru_cache_add_lru(page, LRU_ACTIVE_ANON);
1098 add_page_to_unevictable_list(page);
1102 * page_add_file_rmap - add pte mapping to a file page
1103 * @page: the page to add the mapping to
1105 * The caller needs to hold the pte lock.
1107 void page_add_file_rmap(struct page *page)
1109 if (atomic_inc_and_test(&page->_mapcount)) {
1110 __inc_zone_page_state(page, NR_FILE_MAPPED);
1111 mem_cgroup_inc_page_stat(page, MEMCG_NR_FILE_MAPPED);
1116 * page_remove_rmap - take down pte mapping from a page
1117 * @page: page to remove mapping from
1119 * The caller needs to hold the pte lock.
1121 void page_remove_rmap(struct page *page)
1123 /* page still mapped by someone else? */
1124 if (!atomic_add_negative(-1, &page->_mapcount))
1128 * Now that the last pte has gone, s390 must transfer dirty
1129 * flag from storage key to struct page. We can usually skip
1130 * this if the page is anon, so about to be freed; but perhaps
1131 * not if it's in swapcache - there might be another pte slot
1132 * containing the swap entry, but page not yet written to swap.
1134 if ((!PageAnon(page) || PageSwapCache(page)) &&
1135 page_test_and_clear_dirty(page_to_pfn(page), 1))
1136 set_page_dirty(page);
1138 * Hugepages are not counted in NR_ANON_PAGES nor NR_FILE_MAPPED
1139 * and not charged by memcg for now.
1141 if (unlikely(PageHuge(page)))
1143 if (PageAnon(page)) {
1144 mem_cgroup_uncharge_page(page);
1145 if (!PageTransHuge(page))
1146 __dec_zone_page_state(page, NR_ANON_PAGES);
1148 __dec_zone_page_state(page,
1149 NR_ANON_TRANSPARENT_HUGEPAGES);
1151 __dec_zone_page_state(page, NR_FILE_MAPPED);
1152 mem_cgroup_dec_page_stat(page, MEMCG_NR_FILE_MAPPED);
1155 * It would be tidy to reset the PageAnon mapping here,
1156 * but that might overwrite a racing page_add_anon_rmap
1157 * which increments mapcount after us but sets mapping
1158 * before us: so leave the reset to free_hot_cold_page,
1159 * and remember that it's only reliable while mapped.
1160 * Leaving it set also helps swapoff to reinstate ptes
1161 * faster for those pages still in swapcache.
1166 * Subfunctions of try_to_unmap: try_to_unmap_one called
1167 * repeatedly from try_to_unmap_ksm, try_to_unmap_anon or try_to_unmap_file.
1169 int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
1170 unsigned long address, enum ttu_flags flags)
1172 struct mm_struct *mm = vma->vm_mm;
1176 int ret = SWAP_AGAIN;
1178 pte = page_check_address(page, mm, address, &ptl, 0);
1183 * If the page is mlock()d, we cannot swap it out.
1184 * If it's recently referenced (perhaps page_referenced
1185 * skipped over this mm) then we should reactivate it.
1187 if (!(flags & TTU_IGNORE_MLOCK)) {
1188 if (vma->vm_flags & VM_LOCKED)
1191 if (TTU_ACTION(flags) == TTU_MUNLOCK)
1194 if (!(flags & TTU_IGNORE_ACCESS)) {
1195 if (ptep_clear_flush_young_notify(vma, address, pte)) {
1201 /* Nuke the page table entry. */
1202 flush_cache_page(vma, address, page_to_pfn(page));
1203 pteval = ptep_clear_flush_notify(vma, address, pte);
1205 /* Move the dirty bit to the physical page now the pte is gone. */
1206 if (pte_dirty(pteval))
1207 set_page_dirty(page);
1209 /* Update high watermark before we lower rss */
1210 update_hiwater_rss(mm);
1212 if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
1214 dec_mm_counter(mm, MM_ANONPAGES);
1216 dec_mm_counter(mm, MM_FILEPAGES);
1217 set_pte_at(mm, address, pte,
1218 swp_entry_to_pte(make_hwpoison_entry(page)));
1219 } else if (PageAnon(page)) {
1220 swp_entry_t entry = { .val = page_private(page) };
1222 if (PageSwapCache(page)) {
1224 * Store the swap location in the pte.
1225 * See handle_pte_fault() ...
1227 if (swap_duplicate(entry) < 0) {
1228 set_pte_at(mm, address, pte, pteval);
1232 if (list_empty(&mm->mmlist)) {
1233 spin_lock(&mmlist_lock);
1234 if (list_empty(&mm->mmlist))
1235 list_add(&mm->mmlist, &init_mm.mmlist);
1236 spin_unlock(&mmlist_lock);
1238 dec_mm_counter(mm, MM_ANONPAGES);
1239 inc_mm_counter(mm, MM_SWAPENTS);
1240 } else if (PAGE_MIGRATION) {
1242 * Store the pfn of the page in a special migration
1243 * pte. do_swap_page() will wait until the migration
1244 * pte is removed and then restart fault handling.
1246 BUG_ON(TTU_ACTION(flags) != TTU_MIGRATION);
1247 entry = make_migration_entry(page, pte_write(pteval));
1249 set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
1250 BUG_ON(pte_file(*pte));
1251 } else if (PAGE_MIGRATION && (TTU_ACTION(flags) == TTU_MIGRATION)) {
1252 /* Establish migration entry for a file page */
1254 entry = make_migration_entry(page, pte_write(pteval));
1255 set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
1257 dec_mm_counter(mm, MM_FILEPAGES);
1259 page_remove_rmap(page);
1260 page_cache_release(page);
1263 pte_unmap_unlock(pte, ptl);
1268 pte_unmap_unlock(pte, ptl);
1272 * We need mmap_sem locking, Otherwise VM_LOCKED check makes
1273 * unstable result and race. Plus, We can't wait here because
1274 * we now hold anon_vma->mutex or mapping->i_mmap_mutex.
1275 * if trylock failed, the page remain in evictable lru and later
1276 * vmscan could retry to move the page to unevictable lru if the
1277 * page is actually mlocked.
1279 if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
1280 if (vma->vm_flags & VM_LOCKED) {
1281 mlock_vma_page(page);
1284 up_read(&vma->vm_mm->mmap_sem);
1290 * objrmap doesn't work for nonlinear VMAs because the assumption that
1291 * offset-into-file correlates with offset-into-virtual-addresses does not hold.
1292 * Consequently, given a particular page and its ->index, we cannot locate the
1293 * ptes which are mapping that page without an exhaustive linear search.
1295 * So what this code does is a mini "virtual scan" of each nonlinear VMA which
1296 * maps the file to which the target page belongs. The ->vm_private_data field
1297 * holds the current cursor into that scan. Successive searches will circulate
1298 * around the vma's virtual address space.
1300 * So as more replacement pressure is applied to the pages in a nonlinear VMA,
1301 * more scanning pressure is placed against them as well. Eventually pages
1302 * will become fully unmapped and are eligible for eviction.
1304 * For very sparsely populated VMAs this is a little inefficient - chances are
1305 * there there won't be many ptes located within the scan cluster. In this case
1306 * maybe we could scan further - to the end of the pte page, perhaps.
1308 * Mlocked pages: check VM_LOCKED under mmap_sem held for read, if we can
1309 * acquire it without blocking. If vma locked, mlock the pages in the cluster,
1310 * rather than unmapping them. If we encounter the "check_page" that vmscan is
1311 * trying to unmap, return SWAP_MLOCK, else default SWAP_AGAIN.
1313 #define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE)
1314 #define CLUSTER_MASK (~(CLUSTER_SIZE - 1))
1316 static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount,
1317 struct vm_area_struct *vma, struct page *check_page)
1319 struct mm_struct *mm = vma->vm_mm;
1327 unsigned long address;
1329 int ret = SWAP_AGAIN;
1332 address = (vma->vm_start + cursor) & CLUSTER_MASK;
1333 end = address + CLUSTER_SIZE;
1334 if (address < vma->vm_start)
1335 address = vma->vm_start;
1336 if (end > vma->vm_end)
1339 pgd = pgd_offset(mm, address);
1340 if (!pgd_present(*pgd))
1343 pud = pud_offset(pgd, address);
1344 if (!pud_present(*pud))
1347 pmd = pmd_offset(pud, address);
1348 if (!pmd_present(*pmd))
1352 * If we can acquire the mmap_sem for read, and vma is VM_LOCKED,
1353 * keep the sem while scanning the cluster for mlocking pages.
1355 if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
1356 locked_vma = (vma->vm_flags & VM_LOCKED);
1358 up_read(&vma->vm_mm->mmap_sem); /* don't need it */
1361 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1363 /* Update high watermark before we lower rss */
1364 update_hiwater_rss(mm);
1366 for (; address < end; pte++, address += PAGE_SIZE) {
1367 if (!pte_present(*pte))
1369 page = vm_normal_page(vma, address, *pte);
1370 BUG_ON(!page || PageAnon(page));
1373 mlock_vma_page(page); /* no-op if already mlocked */
1374 if (page == check_page)
1376 continue; /* don't unmap */
1379 if (ptep_clear_flush_young_notify(vma, address, pte))
1382 /* Nuke the page table entry. */
1383 flush_cache_page(vma, address, pte_pfn(*pte));
1384 pteval = ptep_clear_flush_notify(vma, address, pte);
1386 /* If nonlinear, store the file page offset in the pte. */
1387 if (page->index != linear_page_index(vma, address))
1388 set_pte_at(mm, address, pte, pgoff_to_pte(page->index));
1390 /* Move the dirty bit to the physical page now the pte is gone. */
1391 if (pte_dirty(pteval))
1392 set_page_dirty(page);
1394 page_remove_rmap(page);
1395 page_cache_release(page);
1396 dec_mm_counter(mm, MM_FILEPAGES);
1399 pte_unmap_unlock(pte - 1, ptl);
1401 up_read(&vma->vm_mm->mmap_sem);
1405 bool is_vma_temporary_stack(struct vm_area_struct *vma)
1407 int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP);
1412 if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) ==
1413 VM_STACK_INCOMPLETE_SETUP)
1420 * try_to_unmap_anon - unmap or unlock anonymous page using the object-based
1422 * @page: the page to unmap/unlock
1423 * @flags: action and flags
1425 * Find all the mappings of a page using the mapping pointer and the vma chains
1426 * contained in the anon_vma struct it points to.
1428 * This function is only called from try_to_unmap/try_to_munlock for
1430 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1431 * where the page was found will be held for write. So, we won't recheck
1432 * vm_flags for that VMA. That should be OK, because that vma shouldn't be
1435 static int try_to_unmap_anon(struct page *page, enum ttu_flags flags)
1437 struct anon_vma *anon_vma;
1438 struct anon_vma_chain *avc;
1439 int ret = SWAP_AGAIN;
1441 anon_vma = page_lock_anon_vma(page);
1445 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1446 struct vm_area_struct *vma = avc->vma;
1447 unsigned long address;
1450 * During exec, a temporary VMA is setup and later moved.
1451 * The VMA is moved under the anon_vma lock but not the
1452 * page tables leading to a race where migration cannot
1453 * find the migration ptes. Rather than increasing the
1454 * locking requirements of exec(), migration skips
1455 * temporary VMAs until after exec() completes.
1457 if (PAGE_MIGRATION && (flags & TTU_MIGRATION) &&
1458 is_vma_temporary_stack(vma))
1461 address = vma_address(page, vma);
1462 if (address == -EFAULT)
1464 ret = try_to_unmap_one(page, vma, address, flags);
1465 if (ret != SWAP_AGAIN || !page_mapped(page))
1469 page_unlock_anon_vma(anon_vma);
1474 * try_to_unmap_file - unmap/unlock file page using the object-based rmap method
1475 * @page: the page to unmap/unlock
1476 * @flags: action and flags
1478 * Find all the mappings of a page using the mapping pointer and the vma chains
1479 * contained in the address_space struct it points to.
1481 * This function is only called from try_to_unmap/try_to_munlock for
1482 * object-based pages.
1483 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1484 * where the page was found will be held for write. So, we won't recheck
1485 * vm_flags for that VMA. That should be OK, because that vma shouldn't be
1488 static int try_to_unmap_file(struct page *page, enum ttu_flags flags)
1490 struct address_space *mapping = page->mapping;
1491 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1492 struct vm_area_struct *vma;
1493 struct prio_tree_iter iter;
1494 int ret = SWAP_AGAIN;
1495 unsigned long cursor;
1496 unsigned long max_nl_cursor = 0;
1497 unsigned long max_nl_size = 0;
1498 unsigned int mapcount;
1500 mutex_lock(&mapping->i_mmap_mutex);
1501 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
1502 unsigned long address = vma_address(page, vma);
1503 if (address == -EFAULT)
1505 ret = try_to_unmap_one(page, vma, address, flags);
1506 if (ret != SWAP_AGAIN || !page_mapped(page))
1510 if (list_empty(&mapping->i_mmap_nonlinear))
1514 * We don't bother to try to find the munlocked page in nonlinears.
1515 * It's costly. Instead, later, page reclaim logic may call
1516 * try_to_unmap(TTU_MUNLOCK) and recover PG_mlocked lazily.
1518 if (TTU_ACTION(flags) == TTU_MUNLOCK)
1521 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
1522 shared.vm_set.list) {
1523 cursor = (unsigned long) vma->vm_private_data;
1524 if (cursor > max_nl_cursor)
1525 max_nl_cursor = cursor;
1526 cursor = vma->vm_end - vma->vm_start;
1527 if (cursor > max_nl_size)
1528 max_nl_size = cursor;
1531 if (max_nl_size == 0) { /* all nonlinears locked or reserved ? */
1537 * We don't try to search for this page in the nonlinear vmas,
1538 * and page_referenced wouldn't have found it anyway. Instead
1539 * just walk the nonlinear vmas trying to age and unmap some.
1540 * The mapcount of the page we came in with is irrelevant,
1541 * but even so use it as a guide to how hard we should try?
1543 mapcount = page_mapcount(page);
1548 max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK;
1549 if (max_nl_cursor == 0)
1550 max_nl_cursor = CLUSTER_SIZE;
1553 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
1554 shared.vm_set.list) {
1555 cursor = (unsigned long) vma->vm_private_data;
1556 while ( cursor < max_nl_cursor &&
1557 cursor < vma->vm_end - vma->vm_start) {
1558 if (try_to_unmap_cluster(cursor, &mapcount,
1559 vma, page) == SWAP_MLOCK)
1561 cursor += CLUSTER_SIZE;
1562 vma->vm_private_data = (void *) cursor;
1563 if ((int)mapcount <= 0)
1566 vma->vm_private_data = (void *) max_nl_cursor;
1569 max_nl_cursor += CLUSTER_SIZE;
1570 } while (max_nl_cursor <= max_nl_size);
1573 * Don't loop forever (perhaps all the remaining pages are
1574 * in locked vmas). Reset cursor on all unreserved nonlinear
1575 * vmas, now forgetting on which ones it had fallen behind.
1577 list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list)
1578 vma->vm_private_data = NULL;
1580 mutex_unlock(&mapping->i_mmap_mutex);
1585 * try_to_unmap - try to remove all page table mappings to a page
1586 * @page: the page to get unmapped
1587 * @flags: action and flags
1589 * Tries to remove all the page table entries which are mapping this
1590 * page, used in the pageout path. Caller must hold the page lock.
1591 * Return values are:
1593 * SWAP_SUCCESS - we succeeded in removing all mappings
1594 * SWAP_AGAIN - we missed a mapping, try again later
1595 * SWAP_FAIL - the page is unswappable
1596 * SWAP_MLOCK - page is mlocked.
1598 int try_to_unmap(struct page *page, enum ttu_flags flags)
1602 BUG_ON(!PageLocked(page));
1603 VM_BUG_ON(!PageHuge(page) && PageTransHuge(page));
1605 if (unlikely(PageKsm(page)))
1606 ret = try_to_unmap_ksm(page, flags);
1607 else if (PageAnon(page))
1608 ret = try_to_unmap_anon(page, flags);
1610 ret = try_to_unmap_file(page, flags);
1611 if (ret != SWAP_MLOCK && !page_mapped(page))
1617 * try_to_munlock - try to munlock a page
1618 * @page: the page to be munlocked
1620 * Called from munlock code. Checks all of the VMAs mapping the page
1621 * to make sure nobody else has this page mlocked. The page will be
1622 * returned with PG_mlocked cleared if no other vmas have it mlocked.
1624 * Return values are:
1626 * SWAP_AGAIN - no vma is holding page mlocked, or,
1627 * SWAP_AGAIN - page mapped in mlocked vma -- couldn't acquire mmap sem
1628 * SWAP_FAIL - page cannot be located at present
1629 * SWAP_MLOCK - page is now mlocked.
1631 int try_to_munlock(struct page *page)
1633 VM_BUG_ON(!PageLocked(page) || PageLRU(page));
1635 if (unlikely(PageKsm(page)))
1636 return try_to_unmap_ksm(page, TTU_MUNLOCK);
1637 else if (PageAnon(page))
1638 return try_to_unmap_anon(page, TTU_MUNLOCK);
1640 return try_to_unmap_file(page, TTU_MUNLOCK);
1643 void __put_anon_vma(struct anon_vma *anon_vma)
1645 struct anon_vma *root = anon_vma->root;
1647 if (root != anon_vma && atomic_dec_and_test(&root->refcount))
1648 anon_vma_free(root);
1650 anon_vma_free(anon_vma);
1653 #ifdef CONFIG_MIGRATION
1655 * rmap_walk() and its helpers rmap_walk_anon() and rmap_walk_file():
1656 * Called by migrate.c to remove migration ptes, but might be used more later.
1658 static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *,
1659 struct vm_area_struct *, unsigned long, void *), void *arg)
1661 struct anon_vma *anon_vma;
1662 struct anon_vma_chain *avc;
1663 int ret = SWAP_AGAIN;
1666 * Note: remove_migration_ptes() cannot use page_lock_anon_vma()
1667 * because that depends on page_mapped(); but not all its usages
1668 * are holding mmap_sem. Users without mmap_sem are required to
1669 * take a reference count to prevent the anon_vma disappearing
1671 anon_vma = page_anon_vma(page);
1674 anon_vma_lock(anon_vma);
1675 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1676 struct vm_area_struct *vma = avc->vma;
1677 unsigned long address = vma_address(page, vma);
1678 if (address == -EFAULT)
1680 ret = rmap_one(page, vma, address, arg);
1681 if (ret != SWAP_AGAIN)
1684 anon_vma_unlock(anon_vma);
1688 static int rmap_walk_file(struct page *page, int (*rmap_one)(struct page *,
1689 struct vm_area_struct *, unsigned long, void *), void *arg)
1691 struct address_space *mapping = page->mapping;
1692 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1693 struct vm_area_struct *vma;
1694 struct prio_tree_iter iter;
1695 int ret = SWAP_AGAIN;
1699 mutex_lock(&mapping->i_mmap_mutex);
1700 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
1701 unsigned long address = vma_address(page, vma);
1702 if (address == -EFAULT)
1704 ret = rmap_one(page, vma, address, arg);
1705 if (ret != SWAP_AGAIN)
1709 * No nonlinear handling: being always shared, nonlinear vmas
1710 * never contain migration ptes. Decide what to do about this
1711 * limitation to linear when we need rmap_walk() on nonlinear.
1713 mutex_unlock(&mapping->i_mmap_mutex);
1717 int rmap_walk(struct page *page, int (*rmap_one)(struct page *,
1718 struct vm_area_struct *, unsigned long, void *), void *arg)
1720 VM_BUG_ON(!PageLocked(page));
1722 if (unlikely(PageKsm(page)))
1723 return rmap_walk_ksm(page, rmap_one, arg);
1724 else if (PageAnon(page))
1725 return rmap_walk_anon(page, rmap_one, arg);
1727 return rmap_walk_file(page, rmap_one, arg);
1729 #endif /* CONFIG_MIGRATION */
1731 #ifdef CONFIG_HUGETLB_PAGE
1733 * The following three functions are for anonymous (private mapped) hugepages.
1734 * Unlike common anonymous pages, anonymous hugepages have no accounting code
1735 * and no lru code, because we handle hugepages differently from common pages.
1737 static void __hugepage_set_anon_rmap(struct page *page,
1738 struct vm_area_struct *vma, unsigned long address, int exclusive)
1740 struct anon_vma *anon_vma = vma->anon_vma;
1747 anon_vma = anon_vma->root;
1749 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1750 page->mapping = (struct address_space *) anon_vma;
1751 page->index = linear_page_index(vma, address);
1754 void hugepage_add_anon_rmap(struct page *page,
1755 struct vm_area_struct *vma, unsigned long address)
1757 struct anon_vma *anon_vma = vma->anon_vma;
1760 BUG_ON(!PageLocked(page));
1762 /* address might be in next vma when migration races vma_adjust */
1763 first = atomic_inc_and_test(&page->_mapcount);
1765 __hugepage_set_anon_rmap(page, vma, address, 0);
1768 void hugepage_add_new_anon_rmap(struct page *page,
1769 struct vm_area_struct *vma, unsigned long address)
1771 BUG_ON(address < vma->vm_start || address >= vma->vm_end);
1772 atomic_set(&page->_mapcount, 0);
1773 __hugepage_set_anon_rmap(page, vma, address, 1);
1775 #endif /* CONFIG_HUGETLB_PAGE */