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/export.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);
123 static void anon_vma_chain_link(struct vm_area_struct *vma,
124 struct anon_vma_chain *avc,
125 struct anon_vma *anon_vma)
128 avc->anon_vma = anon_vma;
129 list_add(&avc->same_vma, &vma->anon_vma_chain);
130 anon_vma_interval_tree_insert(avc, &anon_vma->rb_root);
134 * anon_vma_prepare - attach an anon_vma to a memory region
135 * @vma: the memory region in question
137 * This makes sure the memory mapping described by 'vma' has
138 * an 'anon_vma' attached to it, so that we can associate the
139 * anonymous pages mapped into it with that anon_vma.
141 * The common case will be that we already have one, but if
142 * not we either need to find an adjacent mapping that we
143 * can re-use the anon_vma from (very common when the only
144 * reason for splitting a vma has been mprotect()), or we
145 * allocate a new one.
147 * Anon-vma allocations are very subtle, because we may have
148 * optimistically looked up an anon_vma in page_lock_anon_vma()
149 * and that may actually touch the spinlock even in the newly
150 * allocated vma (it depends on RCU to make sure that the
151 * anon_vma isn't actually destroyed).
153 * As a result, we need to do proper anon_vma locking even
154 * for the new allocation. At the same time, we do not want
155 * to do any locking for the common case of already having
158 * This must be called with the mmap_sem held for reading.
160 int anon_vma_prepare(struct vm_area_struct *vma)
162 struct anon_vma *anon_vma = vma->anon_vma;
163 struct anon_vma_chain *avc;
166 if (unlikely(!anon_vma)) {
167 struct mm_struct *mm = vma->vm_mm;
168 struct anon_vma *allocated;
170 avc = anon_vma_chain_alloc(GFP_KERNEL);
174 anon_vma = find_mergeable_anon_vma(vma);
177 anon_vma = anon_vma_alloc();
178 if (unlikely(!anon_vma))
179 goto out_enomem_free_avc;
180 allocated = anon_vma;
183 anon_vma_lock(anon_vma);
184 /* page_table_lock to protect against threads */
185 spin_lock(&mm->page_table_lock);
186 if (likely(!vma->anon_vma)) {
187 vma->anon_vma = anon_vma;
188 anon_vma_chain_link(vma, avc, anon_vma);
192 spin_unlock(&mm->page_table_lock);
193 anon_vma_unlock(anon_vma);
195 if (unlikely(allocated))
196 put_anon_vma(allocated);
198 anon_vma_chain_free(avc);
203 anon_vma_chain_free(avc);
209 * This is a useful helper function for locking the anon_vma root as
210 * we traverse the vma->anon_vma_chain, looping over anon_vma's that
213 * Such anon_vma's should have the same root, so you'd expect to see
214 * just a single mutex_lock for the whole traversal.
216 static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma)
218 struct anon_vma *new_root = anon_vma->root;
219 if (new_root != root) {
220 if (WARN_ON_ONCE(root))
221 mutex_unlock(&root->mutex);
223 mutex_lock(&root->mutex);
228 static inline void unlock_anon_vma_root(struct anon_vma *root)
231 mutex_unlock(&root->mutex);
235 * Attach the anon_vmas from src to dst.
236 * Returns 0 on success, -ENOMEM on failure.
238 int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
240 struct anon_vma_chain *avc, *pavc;
241 struct anon_vma *root = NULL;
243 list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
244 struct anon_vma *anon_vma;
246 avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN);
247 if (unlikely(!avc)) {
248 unlock_anon_vma_root(root);
250 avc = anon_vma_chain_alloc(GFP_KERNEL);
254 anon_vma = pavc->anon_vma;
255 root = lock_anon_vma_root(root, anon_vma);
256 anon_vma_chain_link(dst, avc, anon_vma);
258 unlock_anon_vma_root(root);
262 unlink_anon_vmas(dst);
267 * Attach vma to its own anon_vma, as well as to the anon_vmas that
268 * the corresponding VMA in the parent process is attached to.
269 * Returns 0 on success, non-zero on failure.
271 int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
273 struct anon_vma_chain *avc;
274 struct anon_vma *anon_vma;
276 /* Don't bother if the parent process has no anon_vma here. */
281 * First, attach the new VMA to the parent VMA's anon_vmas,
282 * so rmap can find non-COWed pages in child processes.
284 if (anon_vma_clone(vma, pvma))
287 /* Then add our own anon_vma. */
288 anon_vma = anon_vma_alloc();
291 avc = anon_vma_chain_alloc(GFP_KERNEL);
293 goto out_error_free_anon_vma;
296 * The root anon_vma's spinlock is the lock actually used when we
297 * lock any of the anon_vmas in this anon_vma tree.
299 anon_vma->root = pvma->anon_vma->root;
301 * With refcounts, an anon_vma can stay around longer than the
302 * process it belongs to. The root anon_vma needs to be pinned until
303 * this anon_vma is freed, because the lock lives in the root.
305 get_anon_vma(anon_vma->root);
306 /* Mark this anon_vma as the one where our new (COWed) pages go. */
307 vma->anon_vma = anon_vma;
308 anon_vma_lock(anon_vma);
309 anon_vma_chain_link(vma, avc, anon_vma);
310 anon_vma_unlock(anon_vma);
314 out_error_free_anon_vma:
315 put_anon_vma(anon_vma);
317 unlink_anon_vmas(vma);
321 void unlink_anon_vmas(struct vm_area_struct *vma)
323 struct anon_vma_chain *avc, *next;
324 struct anon_vma *root = NULL;
327 * Unlink each anon_vma chained to the VMA. This list is ordered
328 * from newest to oldest, ensuring the root anon_vma gets freed last.
330 list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
331 struct anon_vma *anon_vma = avc->anon_vma;
333 root = lock_anon_vma_root(root, anon_vma);
334 anon_vma_interval_tree_remove(avc, &anon_vma->rb_root);
337 * Leave empty anon_vmas on the list - we'll need
338 * to free them outside the lock.
340 if (RB_EMPTY_ROOT(&anon_vma->rb_root))
343 list_del(&avc->same_vma);
344 anon_vma_chain_free(avc);
346 unlock_anon_vma_root(root);
349 * Iterate the list once more, it now only contains empty and unlinked
350 * anon_vmas, destroy them. Could not do before due to __put_anon_vma()
351 * needing to acquire the anon_vma->root->mutex.
353 list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
354 struct anon_vma *anon_vma = avc->anon_vma;
356 put_anon_vma(anon_vma);
358 list_del(&avc->same_vma);
359 anon_vma_chain_free(avc);
363 static void anon_vma_ctor(void *data)
365 struct anon_vma *anon_vma = data;
367 mutex_init(&anon_vma->mutex);
368 atomic_set(&anon_vma->refcount, 0);
369 anon_vma->rb_root = RB_ROOT;
372 void __init anon_vma_init(void)
374 anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
375 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor);
376 anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain, SLAB_PANIC);
380 * Getting a lock on a stable anon_vma from a page off the LRU is tricky!
382 * Since there is no serialization what so ever against page_remove_rmap()
383 * the best this function can do is return a locked anon_vma that might
384 * have been relevant to this page.
386 * The page might have been remapped to a different anon_vma or the anon_vma
387 * returned may already be freed (and even reused).
389 * In case it was remapped to a different anon_vma, the new anon_vma will be a
390 * child of the old anon_vma, and the anon_vma lifetime rules will therefore
391 * ensure that any anon_vma obtained from the page will still be valid for as
392 * long as we observe page_mapped() [ hence all those page_mapped() tests ].
394 * All users of this function must be very careful when walking the anon_vma
395 * chain and verify that the page in question is indeed mapped in it
396 * [ something equivalent to page_mapped_in_vma() ].
398 * Since anon_vma's slab is DESTROY_BY_RCU and we know from page_remove_rmap()
399 * that the anon_vma pointer from page->mapping is valid if there is a
400 * mapcount, we can dereference the anon_vma after observing those.
402 struct anon_vma *page_get_anon_vma(struct page *page)
404 struct anon_vma *anon_vma = NULL;
405 unsigned long anon_mapping;
408 anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping);
409 if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
411 if (!page_mapped(page))
414 anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
415 if (!atomic_inc_not_zero(&anon_vma->refcount)) {
421 * If this page is still mapped, then its anon_vma cannot have been
422 * freed. But if it has been unmapped, we have no security against the
423 * anon_vma structure being freed and reused (for another anon_vma:
424 * SLAB_DESTROY_BY_RCU guarantees that - so the atomic_inc_not_zero()
425 * above cannot corrupt).
427 if (!page_mapped(page)) {
428 put_anon_vma(anon_vma);
438 * Similar to page_get_anon_vma() except it locks the anon_vma.
440 * Its a little more complex as it tries to keep the fast path to a single
441 * atomic op -- the trylock. If we fail the trylock, we fall back to getting a
442 * reference like with page_get_anon_vma() and then block on the mutex.
444 struct anon_vma *page_lock_anon_vma(struct page *page)
446 struct anon_vma *anon_vma = NULL;
447 struct anon_vma *root_anon_vma;
448 unsigned long anon_mapping;
451 anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping);
452 if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
454 if (!page_mapped(page))
457 anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
458 root_anon_vma = ACCESS_ONCE(anon_vma->root);
459 if (mutex_trylock(&root_anon_vma->mutex)) {
461 * If the page is still mapped, then this anon_vma is still
462 * its anon_vma, and holding the mutex ensures that it will
463 * not go away, see anon_vma_free().
465 if (!page_mapped(page)) {
466 mutex_unlock(&root_anon_vma->mutex);
472 /* trylock failed, we got to sleep */
473 if (!atomic_inc_not_zero(&anon_vma->refcount)) {
478 if (!page_mapped(page)) {
479 put_anon_vma(anon_vma);
484 /* we pinned the anon_vma, its safe to sleep */
486 anon_vma_lock(anon_vma);
488 if (atomic_dec_and_test(&anon_vma->refcount)) {
490 * Oops, we held the last refcount, release the lock
491 * and bail -- can't simply use put_anon_vma() because
492 * we'll deadlock on the anon_vma_lock() recursion.
494 anon_vma_unlock(anon_vma);
495 __put_anon_vma(anon_vma);
506 void page_unlock_anon_vma(struct anon_vma *anon_vma)
508 anon_vma_unlock(anon_vma);
512 * At what user virtual address is page expected in @vma?
514 static inline unsigned long
515 __vma_address(struct page *page, struct vm_area_struct *vma)
517 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
519 if (unlikely(is_vm_hugetlb_page(vma)))
520 pgoff = page->index << huge_page_order(page_hstate(page));
522 return vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
526 vma_address(struct page *page, struct vm_area_struct *vma)
528 unsigned long address = __vma_address(page, vma);
530 /* page should be within @vma mapping range */
531 VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
537 * At what user virtual address is page expected in vma?
538 * Caller should check the page is actually part of the vma.
540 unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
542 unsigned long address;
543 if (PageAnon(page)) {
544 struct anon_vma *page__anon_vma = page_anon_vma(page);
546 * Note: swapoff's unuse_vma() is more efficient with this
547 * check, and needs it to match anon_vma when KSM is active.
549 if (!vma->anon_vma || !page__anon_vma ||
550 vma->anon_vma->root != page__anon_vma->root)
552 } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
554 vma->vm_file->f_mapping != page->mapping)
558 address = __vma_address(page, vma);
559 if (unlikely(address < vma->vm_start || address >= vma->vm_end))
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 (unlikely(address < vma->vm_start || address >= vma->vm_end))
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);
719 *vm_flags |= vma->vm_flags;
724 static int page_referenced_anon(struct page *page,
725 struct mem_cgroup *memcg,
726 unsigned long *vm_flags)
728 unsigned int mapcount;
729 struct anon_vma *anon_vma;
731 struct anon_vma_chain *avc;
734 anon_vma = page_lock_anon_vma(page);
738 mapcount = page_mapcount(page);
739 pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
740 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
741 struct vm_area_struct *vma = avc->vma;
742 unsigned long address = vma_address(page, vma);
744 * If we are reclaiming on behalf of a cgroup, skip
745 * counting on behalf of references from different
748 if (memcg && !mm_match_cgroup(vma->vm_mm, memcg))
750 referenced += page_referenced_one(page, vma, address,
751 &mapcount, vm_flags);
756 page_unlock_anon_vma(anon_vma);
761 * page_referenced_file - referenced check for object-based rmap
762 * @page: the page we're checking references on.
763 * @memcg: target memory control group
764 * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
766 * For an object-based mapped page, find all the places it is mapped and
767 * check/clear the referenced flag. This is done by following the page->mapping
768 * pointer, then walking the chain of vmas it holds. It returns the number
769 * of references it found.
771 * This function is only called from page_referenced for object-based pages.
773 static int page_referenced_file(struct page *page,
774 struct mem_cgroup *memcg,
775 unsigned long *vm_flags)
777 unsigned int mapcount;
778 struct address_space *mapping = page->mapping;
779 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
780 struct vm_area_struct *vma;
784 * The caller's checks on page->mapping and !PageAnon have made
785 * sure that this is a file page: the check for page->mapping
786 * excludes the case just before it gets set on an anon page.
788 BUG_ON(PageAnon(page));
791 * The page lock not only makes sure that page->mapping cannot
792 * suddenly be NULLified by truncation, it makes sure that the
793 * structure at mapping cannot be freed and reused yet,
794 * so we can safely take mapping->i_mmap_mutex.
796 BUG_ON(!PageLocked(page));
798 mutex_lock(&mapping->i_mmap_mutex);
801 * i_mmap_mutex does not stabilize mapcount at all, but mapcount
802 * is more likely to be accurate if we note it after spinning.
804 mapcount = page_mapcount(page);
806 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
807 unsigned long address = vma_address(page, vma);
809 * If we are reclaiming on behalf of a cgroup, skip
810 * counting on behalf of references from different
813 if (memcg && !mm_match_cgroup(vma->vm_mm, memcg))
815 referenced += page_referenced_one(page, vma, address,
816 &mapcount, vm_flags);
821 mutex_unlock(&mapping->i_mmap_mutex);
826 * page_referenced - test if the page was referenced
827 * @page: the page to test
828 * @is_locked: caller holds lock on the page
829 * @memcg: target memory cgroup
830 * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
832 * Quick test_and_clear_referenced for all mappings to a page,
833 * returns the number of ptes which referenced the page.
835 int page_referenced(struct page *page,
837 struct mem_cgroup *memcg,
838 unsigned long *vm_flags)
844 if (page_mapped(page) && page_rmapping(page)) {
845 if (!is_locked && (!PageAnon(page) || PageKsm(page))) {
846 we_locked = trylock_page(page);
852 if (unlikely(PageKsm(page)))
853 referenced += page_referenced_ksm(page, memcg,
855 else if (PageAnon(page))
856 referenced += page_referenced_anon(page, memcg,
858 else if (page->mapping)
859 referenced += page_referenced_file(page, memcg,
864 if (page_test_and_clear_young(page_to_pfn(page)))
871 static int page_mkclean_one(struct page *page, struct vm_area_struct *vma,
872 unsigned long address)
874 struct mm_struct *mm = vma->vm_mm;
879 pte = page_check_address(page, mm, address, &ptl, 1);
883 if (pte_dirty(*pte) || pte_write(*pte)) {
886 flush_cache_page(vma, address, pte_pfn(*pte));
887 entry = ptep_clear_flush_notify(vma, address, pte);
888 entry = pte_wrprotect(entry);
889 entry = pte_mkclean(entry);
890 set_pte_at(mm, address, pte, entry);
894 pte_unmap_unlock(pte, ptl);
899 static int page_mkclean_file(struct address_space *mapping, struct page *page)
901 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
902 struct vm_area_struct *vma;
905 BUG_ON(PageAnon(page));
907 mutex_lock(&mapping->i_mmap_mutex);
908 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
909 if (vma->vm_flags & VM_SHARED) {
910 unsigned long address = vma_address(page, vma);
911 ret += page_mkclean_one(page, vma, address);
914 mutex_unlock(&mapping->i_mmap_mutex);
918 int page_mkclean(struct page *page)
922 BUG_ON(!PageLocked(page));
924 if (page_mapped(page)) {
925 struct address_space *mapping = page_mapping(page);
927 ret = page_mkclean_file(mapping, page);
928 if (page_test_and_clear_dirty(page_to_pfn(page), 1))
935 EXPORT_SYMBOL_GPL(page_mkclean);
938 * page_move_anon_rmap - move a page to our anon_vma
939 * @page: the page to move to our anon_vma
940 * @vma: the vma the page belongs to
941 * @address: the user virtual address mapped
943 * When a page belongs exclusively to one process after a COW event,
944 * that page can be moved into the anon_vma that belongs to just that
945 * process, so the rmap code will not search the parent or sibling
948 void page_move_anon_rmap(struct page *page,
949 struct vm_area_struct *vma, unsigned long address)
951 struct anon_vma *anon_vma = vma->anon_vma;
953 VM_BUG_ON(!PageLocked(page));
954 VM_BUG_ON(!anon_vma);
955 VM_BUG_ON(page->index != linear_page_index(vma, address));
957 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
958 page->mapping = (struct address_space *) anon_vma;
962 * __page_set_anon_rmap - set up new anonymous rmap
963 * @page: Page to add to rmap
964 * @vma: VM area to add page to.
965 * @address: User virtual address of the mapping
966 * @exclusive: the page is exclusively owned by the current process
968 static void __page_set_anon_rmap(struct page *page,
969 struct vm_area_struct *vma, unsigned long address, int exclusive)
971 struct anon_vma *anon_vma = vma->anon_vma;
979 * If the page isn't exclusively mapped into this vma,
980 * we must use the _oldest_ possible anon_vma for the
984 anon_vma = anon_vma->root;
986 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
987 page->mapping = (struct address_space *) anon_vma;
988 page->index = linear_page_index(vma, address);
992 * __page_check_anon_rmap - sanity check anonymous rmap addition
993 * @page: the page to add the mapping to
994 * @vma: the vm area in which the mapping is added
995 * @address: the user virtual address mapped
997 static void __page_check_anon_rmap(struct page *page,
998 struct vm_area_struct *vma, unsigned long address)
1000 #ifdef CONFIG_DEBUG_VM
1002 * The page's anon-rmap details (mapping and index) are guaranteed to
1003 * be set up correctly at this point.
1005 * We have exclusion against page_add_anon_rmap because the caller
1006 * always holds the page locked, except if called from page_dup_rmap,
1007 * in which case the page is already known to be setup.
1009 * We have exclusion against page_add_new_anon_rmap because those pages
1010 * are initially only visible via the pagetables, and the pte is locked
1011 * over the call to page_add_new_anon_rmap.
1013 BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root);
1014 BUG_ON(page->index != linear_page_index(vma, address));
1019 * page_add_anon_rmap - add pte mapping to an anonymous page
1020 * @page: the page to add the mapping to
1021 * @vma: the vm area in which the mapping is added
1022 * @address: the user virtual address mapped
1024 * The caller needs to hold the pte lock, and the page must be locked in
1025 * the anon_vma case: to serialize mapping,index checking after setting,
1026 * and to ensure that PageAnon is not being upgraded racily to PageKsm
1027 * (but PageKsm is never downgraded to PageAnon).
1029 void page_add_anon_rmap(struct page *page,
1030 struct vm_area_struct *vma, unsigned long address)
1032 do_page_add_anon_rmap(page, vma, address, 0);
1036 * Special version of the above for do_swap_page, which often runs
1037 * into pages that are exclusively owned by the current process.
1038 * Everybody else should continue to use page_add_anon_rmap above.
1040 void do_page_add_anon_rmap(struct page *page,
1041 struct vm_area_struct *vma, unsigned long address, int exclusive)
1043 int first = atomic_inc_and_test(&page->_mapcount);
1045 if (!PageTransHuge(page))
1046 __inc_zone_page_state(page, NR_ANON_PAGES);
1048 __inc_zone_page_state(page,
1049 NR_ANON_TRANSPARENT_HUGEPAGES);
1051 if (unlikely(PageKsm(page)))
1054 VM_BUG_ON(!PageLocked(page));
1055 /* address might be in next vma when migration races vma_adjust */
1057 __page_set_anon_rmap(page, vma, address, exclusive);
1059 __page_check_anon_rmap(page, vma, address);
1063 * page_add_new_anon_rmap - add pte mapping to a new anonymous page
1064 * @page: the page to add the mapping to
1065 * @vma: the vm area in which the mapping is added
1066 * @address: the user virtual address mapped
1068 * Same as page_add_anon_rmap but must only be called on *new* pages.
1069 * This means the inc-and-test can be bypassed.
1070 * Page does not have to be locked.
1072 void page_add_new_anon_rmap(struct page *page,
1073 struct vm_area_struct *vma, unsigned long address)
1075 VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
1076 SetPageSwapBacked(page);
1077 atomic_set(&page->_mapcount, 0); /* increment count (starts at -1) */
1078 if (!PageTransHuge(page))
1079 __inc_zone_page_state(page, NR_ANON_PAGES);
1081 __inc_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
1082 __page_set_anon_rmap(page, vma, address, 1);
1083 if (!mlocked_vma_newpage(vma, page))
1084 lru_cache_add_lru(page, LRU_ACTIVE_ANON);
1086 add_page_to_unevictable_list(page);
1090 * page_add_file_rmap - add pte mapping to a file page
1091 * @page: the page to add the mapping to
1093 * The caller needs to hold the pte lock.
1095 void page_add_file_rmap(struct page *page)
1098 unsigned long flags;
1100 mem_cgroup_begin_update_page_stat(page, &locked, &flags);
1101 if (atomic_inc_and_test(&page->_mapcount)) {
1102 __inc_zone_page_state(page, NR_FILE_MAPPED);
1103 mem_cgroup_inc_page_stat(page, MEMCG_NR_FILE_MAPPED);
1105 mem_cgroup_end_update_page_stat(page, &locked, &flags);
1109 * page_remove_rmap - take down pte mapping from a page
1110 * @page: page to remove mapping from
1112 * The caller needs to hold the pte lock.
1114 void page_remove_rmap(struct page *page)
1116 bool anon = PageAnon(page);
1118 unsigned long flags;
1121 * The anon case has no mem_cgroup page_stat to update; but may
1122 * uncharge_page() below, where the lock ordering can deadlock if
1123 * we hold the lock against page_stat move: so avoid it on anon.
1126 mem_cgroup_begin_update_page_stat(page, &locked, &flags);
1128 /* page still mapped by someone else? */
1129 if (!atomic_add_negative(-1, &page->_mapcount))
1133 * Now that the last pte has gone, s390 must transfer dirty
1134 * flag from storage key to struct page. We can usually skip
1135 * this if the page is anon, so about to be freed; but perhaps
1136 * not if it's in swapcache - there might be another pte slot
1137 * containing the swap entry, but page not yet written to swap.
1139 if ((!anon || PageSwapCache(page)) &&
1140 page_test_and_clear_dirty(page_to_pfn(page), 1))
1141 set_page_dirty(page);
1143 * Hugepages are not counted in NR_ANON_PAGES nor NR_FILE_MAPPED
1144 * and not charged by memcg for now.
1146 if (unlikely(PageHuge(page)))
1149 mem_cgroup_uncharge_page(page);
1150 if (!PageTransHuge(page))
1151 __dec_zone_page_state(page, NR_ANON_PAGES);
1153 __dec_zone_page_state(page,
1154 NR_ANON_TRANSPARENT_HUGEPAGES);
1156 __dec_zone_page_state(page, NR_FILE_MAPPED);
1157 mem_cgroup_dec_page_stat(page, MEMCG_NR_FILE_MAPPED);
1160 * It would be tidy to reset the PageAnon mapping here,
1161 * but that might overwrite a racing page_add_anon_rmap
1162 * which increments mapcount after us but sets mapping
1163 * before us: so leave the reset to free_hot_cold_page,
1164 * and remember that it's only reliable while mapped.
1165 * Leaving it set also helps swapoff to reinstate ptes
1166 * faster for those pages still in swapcache.
1170 mem_cgroup_end_update_page_stat(page, &locked, &flags);
1174 * Subfunctions of try_to_unmap: try_to_unmap_one called
1175 * repeatedly from try_to_unmap_ksm, try_to_unmap_anon or try_to_unmap_file.
1177 int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
1178 unsigned long address, enum ttu_flags flags)
1180 struct mm_struct *mm = vma->vm_mm;
1184 int ret = SWAP_AGAIN;
1186 pte = page_check_address(page, mm, address, &ptl, 0);
1191 * If the page is mlock()d, we cannot swap it out.
1192 * If it's recently referenced (perhaps page_referenced
1193 * skipped over this mm) then we should reactivate it.
1195 if (!(flags & TTU_IGNORE_MLOCK)) {
1196 if (vma->vm_flags & VM_LOCKED)
1199 if (TTU_ACTION(flags) == TTU_MUNLOCK)
1202 if (!(flags & TTU_IGNORE_ACCESS)) {
1203 if (ptep_clear_flush_young_notify(vma, address, pte)) {
1209 /* Nuke the page table entry. */
1210 flush_cache_page(vma, address, page_to_pfn(page));
1211 pteval = ptep_clear_flush_notify(vma, address, pte);
1213 /* Move the dirty bit to the physical page now the pte is gone. */
1214 if (pte_dirty(pteval))
1215 set_page_dirty(page);
1217 /* Update high watermark before we lower rss */
1218 update_hiwater_rss(mm);
1220 if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
1222 dec_mm_counter(mm, MM_ANONPAGES);
1224 dec_mm_counter(mm, MM_FILEPAGES);
1225 set_pte_at(mm, address, pte,
1226 swp_entry_to_pte(make_hwpoison_entry(page)));
1227 } else if (PageAnon(page)) {
1228 swp_entry_t entry = { .val = page_private(page) };
1230 if (PageSwapCache(page)) {
1232 * Store the swap location in the pte.
1233 * See handle_pte_fault() ...
1235 if (swap_duplicate(entry) < 0) {
1236 set_pte_at(mm, address, pte, pteval);
1240 if (list_empty(&mm->mmlist)) {
1241 spin_lock(&mmlist_lock);
1242 if (list_empty(&mm->mmlist))
1243 list_add(&mm->mmlist, &init_mm.mmlist);
1244 spin_unlock(&mmlist_lock);
1246 dec_mm_counter(mm, MM_ANONPAGES);
1247 inc_mm_counter(mm, MM_SWAPENTS);
1248 } else if (IS_ENABLED(CONFIG_MIGRATION)) {
1250 * Store the pfn of the page in a special migration
1251 * pte. do_swap_page() will wait until the migration
1252 * pte is removed and then restart fault handling.
1254 BUG_ON(TTU_ACTION(flags) != TTU_MIGRATION);
1255 entry = make_migration_entry(page, pte_write(pteval));
1257 set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
1258 BUG_ON(pte_file(*pte));
1259 } else if (IS_ENABLED(CONFIG_MIGRATION) &&
1260 (TTU_ACTION(flags) == TTU_MIGRATION)) {
1261 /* Establish migration entry for a file page */
1263 entry = make_migration_entry(page, pte_write(pteval));
1264 set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
1266 dec_mm_counter(mm, MM_FILEPAGES);
1268 page_remove_rmap(page);
1269 page_cache_release(page);
1272 pte_unmap_unlock(pte, ptl);
1277 pte_unmap_unlock(pte, ptl);
1281 * We need mmap_sem locking, Otherwise VM_LOCKED check makes
1282 * unstable result and race. Plus, We can't wait here because
1283 * we now hold anon_vma->mutex or mapping->i_mmap_mutex.
1284 * if trylock failed, the page remain in evictable lru and later
1285 * vmscan could retry to move the page to unevictable lru if the
1286 * page is actually mlocked.
1288 if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
1289 if (vma->vm_flags & VM_LOCKED) {
1290 mlock_vma_page(page);
1293 up_read(&vma->vm_mm->mmap_sem);
1299 * objrmap doesn't work for nonlinear VMAs because the assumption that
1300 * offset-into-file correlates with offset-into-virtual-addresses does not hold.
1301 * Consequently, given a particular page and its ->index, we cannot locate the
1302 * ptes which are mapping that page without an exhaustive linear search.
1304 * So what this code does is a mini "virtual scan" of each nonlinear VMA which
1305 * maps the file to which the target page belongs. The ->vm_private_data field
1306 * holds the current cursor into that scan. Successive searches will circulate
1307 * around the vma's virtual address space.
1309 * So as more replacement pressure is applied to the pages in a nonlinear VMA,
1310 * more scanning pressure is placed against them as well. Eventually pages
1311 * will become fully unmapped and are eligible for eviction.
1313 * For very sparsely populated VMAs this is a little inefficient - chances are
1314 * there there won't be many ptes located within the scan cluster. In this case
1315 * maybe we could scan further - to the end of the pte page, perhaps.
1317 * Mlocked pages: check VM_LOCKED under mmap_sem held for read, if we can
1318 * acquire it without blocking. If vma locked, mlock the pages in the cluster,
1319 * rather than unmapping them. If we encounter the "check_page" that vmscan is
1320 * trying to unmap, return SWAP_MLOCK, else default SWAP_AGAIN.
1322 #define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE)
1323 #define CLUSTER_MASK (~(CLUSTER_SIZE - 1))
1325 static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount,
1326 struct vm_area_struct *vma, struct page *check_page)
1328 struct mm_struct *mm = vma->vm_mm;
1336 unsigned long address;
1338 int ret = SWAP_AGAIN;
1341 address = (vma->vm_start + cursor) & CLUSTER_MASK;
1342 end = address + CLUSTER_SIZE;
1343 if (address < vma->vm_start)
1344 address = vma->vm_start;
1345 if (end > vma->vm_end)
1348 pgd = pgd_offset(mm, address);
1349 if (!pgd_present(*pgd))
1352 pud = pud_offset(pgd, address);
1353 if (!pud_present(*pud))
1356 pmd = pmd_offset(pud, address);
1357 if (!pmd_present(*pmd))
1361 * If we can acquire the mmap_sem for read, and vma is VM_LOCKED,
1362 * keep the sem while scanning the cluster for mlocking pages.
1364 if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
1365 locked_vma = (vma->vm_flags & VM_LOCKED);
1367 up_read(&vma->vm_mm->mmap_sem); /* don't need it */
1370 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1372 /* Update high watermark before we lower rss */
1373 update_hiwater_rss(mm);
1375 for (; address < end; pte++, address += PAGE_SIZE) {
1376 if (!pte_present(*pte))
1378 page = vm_normal_page(vma, address, *pte);
1379 BUG_ON(!page || PageAnon(page));
1382 mlock_vma_page(page); /* no-op if already mlocked */
1383 if (page == check_page)
1385 continue; /* don't unmap */
1388 if (ptep_clear_flush_young_notify(vma, address, pte))
1391 /* Nuke the page table entry. */
1392 flush_cache_page(vma, address, pte_pfn(*pte));
1393 pteval = ptep_clear_flush_notify(vma, address, pte);
1395 /* If nonlinear, store the file page offset in the pte. */
1396 if (page->index != linear_page_index(vma, address))
1397 set_pte_at(mm, address, pte, pgoff_to_pte(page->index));
1399 /* Move the dirty bit to the physical page now the pte is gone. */
1400 if (pte_dirty(pteval))
1401 set_page_dirty(page);
1403 page_remove_rmap(page);
1404 page_cache_release(page);
1405 dec_mm_counter(mm, MM_FILEPAGES);
1408 pte_unmap_unlock(pte - 1, ptl);
1410 up_read(&vma->vm_mm->mmap_sem);
1414 bool is_vma_temporary_stack(struct vm_area_struct *vma)
1416 int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP);
1421 if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) ==
1422 VM_STACK_INCOMPLETE_SETUP)
1429 * try_to_unmap_anon - unmap or unlock anonymous page using the object-based
1431 * @page: the page to unmap/unlock
1432 * @flags: action and flags
1434 * Find all the mappings of a page using the mapping pointer and the vma chains
1435 * contained in the anon_vma struct it points to.
1437 * This function is only called from try_to_unmap/try_to_munlock for
1439 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1440 * where the page was found will be held for write. So, we won't recheck
1441 * vm_flags for that VMA. That should be OK, because that vma shouldn't be
1444 static int try_to_unmap_anon(struct page *page, enum ttu_flags flags)
1446 struct anon_vma *anon_vma;
1448 struct anon_vma_chain *avc;
1449 int ret = SWAP_AGAIN;
1451 anon_vma = page_lock_anon_vma(page);
1455 pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1456 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1457 struct vm_area_struct *vma = avc->vma;
1458 unsigned long address;
1461 * During exec, a temporary VMA is setup and later moved.
1462 * The VMA is moved under the anon_vma lock but not the
1463 * page tables leading to a race where migration cannot
1464 * find the migration ptes. Rather than increasing the
1465 * locking requirements of exec(), migration skips
1466 * temporary VMAs until after exec() completes.
1468 if (IS_ENABLED(CONFIG_MIGRATION) && (flags & TTU_MIGRATION) &&
1469 is_vma_temporary_stack(vma))
1472 address = vma_address(page, vma);
1473 ret = try_to_unmap_one(page, vma, address, flags);
1474 if (ret != SWAP_AGAIN || !page_mapped(page))
1478 page_unlock_anon_vma(anon_vma);
1483 * try_to_unmap_file - unmap/unlock file page using the object-based rmap method
1484 * @page: the page to unmap/unlock
1485 * @flags: action and flags
1487 * Find all the mappings of a page using the mapping pointer and the vma chains
1488 * contained in the address_space struct it points to.
1490 * This function is only called from try_to_unmap/try_to_munlock for
1491 * object-based pages.
1492 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1493 * where the page was found will be held for write. So, we won't recheck
1494 * vm_flags for that VMA. That should be OK, because that vma shouldn't be
1497 static int try_to_unmap_file(struct page *page, enum ttu_flags flags)
1499 struct address_space *mapping = page->mapping;
1500 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1501 struct vm_area_struct *vma;
1502 int ret = SWAP_AGAIN;
1503 unsigned long cursor;
1504 unsigned long max_nl_cursor = 0;
1505 unsigned long max_nl_size = 0;
1506 unsigned int mapcount;
1508 mutex_lock(&mapping->i_mmap_mutex);
1509 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
1510 unsigned long address = vma_address(page, vma);
1511 ret = try_to_unmap_one(page, vma, address, flags);
1512 if (ret != SWAP_AGAIN || !page_mapped(page))
1516 if (list_empty(&mapping->i_mmap_nonlinear))
1520 * We don't bother to try to find the munlocked page in nonlinears.
1521 * It's costly. Instead, later, page reclaim logic may call
1522 * try_to_unmap(TTU_MUNLOCK) and recover PG_mlocked lazily.
1524 if (TTU_ACTION(flags) == TTU_MUNLOCK)
1527 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
1529 cursor = (unsigned long) vma->vm_private_data;
1530 if (cursor > max_nl_cursor)
1531 max_nl_cursor = cursor;
1532 cursor = vma->vm_end - vma->vm_start;
1533 if (cursor > max_nl_size)
1534 max_nl_size = cursor;
1537 if (max_nl_size == 0) { /* all nonlinears locked or reserved ? */
1543 * We don't try to search for this page in the nonlinear vmas,
1544 * and page_referenced wouldn't have found it anyway. Instead
1545 * just walk the nonlinear vmas trying to age and unmap some.
1546 * The mapcount of the page we came in with is irrelevant,
1547 * but even so use it as a guide to how hard we should try?
1549 mapcount = page_mapcount(page);
1554 max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK;
1555 if (max_nl_cursor == 0)
1556 max_nl_cursor = CLUSTER_SIZE;
1559 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
1561 cursor = (unsigned long) vma->vm_private_data;
1562 while ( cursor < max_nl_cursor &&
1563 cursor < vma->vm_end - vma->vm_start) {
1564 if (try_to_unmap_cluster(cursor, &mapcount,
1565 vma, page) == SWAP_MLOCK)
1567 cursor += CLUSTER_SIZE;
1568 vma->vm_private_data = (void *) cursor;
1569 if ((int)mapcount <= 0)
1572 vma->vm_private_data = (void *) max_nl_cursor;
1575 max_nl_cursor += CLUSTER_SIZE;
1576 } while (max_nl_cursor <= max_nl_size);
1579 * Don't loop forever (perhaps all the remaining pages are
1580 * in locked vmas). Reset cursor on all unreserved nonlinear
1581 * vmas, now forgetting on which ones it had fallen behind.
1583 list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.nonlinear)
1584 vma->vm_private_data = NULL;
1586 mutex_unlock(&mapping->i_mmap_mutex);
1591 * try_to_unmap - try to remove all page table mappings to a page
1592 * @page: the page to get unmapped
1593 * @flags: action and flags
1595 * Tries to remove all the page table entries which are mapping this
1596 * page, used in the pageout path. Caller must hold the page lock.
1597 * Return values are:
1599 * SWAP_SUCCESS - we succeeded in removing all mappings
1600 * SWAP_AGAIN - we missed a mapping, try again later
1601 * SWAP_FAIL - the page is unswappable
1602 * SWAP_MLOCK - page is mlocked.
1604 int try_to_unmap(struct page *page, enum ttu_flags flags)
1608 BUG_ON(!PageLocked(page));
1609 VM_BUG_ON(!PageHuge(page) && PageTransHuge(page));
1611 if (unlikely(PageKsm(page)))
1612 ret = try_to_unmap_ksm(page, flags);
1613 else if (PageAnon(page))
1614 ret = try_to_unmap_anon(page, flags);
1616 ret = try_to_unmap_file(page, flags);
1617 if (ret != SWAP_MLOCK && !page_mapped(page))
1623 * try_to_munlock - try to munlock a page
1624 * @page: the page to be munlocked
1626 * Called from munlock code. Checks all of the VMAs mapping the page
1627 * to make sure nobody else has this page mlocked. The page will be
1628 * returned with PG_mlocked cleared if no other vmas have it mlocked.
1630 * Return values are:
1632 * SWAP_AGAIN - no vma is holding page mlocked, or,
1633 * SWAP_AGAIN - page mapped in mlocked vma -- couldn't acquire mmap sem
1634 * SWAP_FAIL - page cannot be located at present
1635 * SWAP_MLOCK - page is now mlocked.
1637 int try_to_munlock(struct page *page)
1639 VM_BUG_ON(!PageLocked(page) || PageLRU(page));
1641 if (unlikely(PageKsm(page)))
1642 return try_to_unmap_ksm(page, TTU_MUNLOCK);
1643 else if (PageAnon(page))
1644 return try_to_unmap_anon(page, TTU_MUNLOCK);
1646 return try_to_unmap_file(page, TTU_MUNLOCK);
1649 void __put_anon_vma(struct anon_vma *anon_vma)
1651 struct anon_vma *root = anon_vma->root;
1653 if (root != anon_vma && atomic_dec_and_test(&root->refcount))
1654 anon_vma_free(root);
1656 anon_vma_free(anon_vma);
1659 #ifdef CONFIG_MIGRATION
1661 * rmap_walk() and its helpers rmap_walk_anon() and rmap_walk_file():
1662 * Called by migrate.c to remove migration ptes, but might be used more later.
1664 static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *,
1665 struct vm_area_struct *, unsigned long, void *), void *arg)
1667 struct anon_vma *anon_vma;
1668 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1669 struct anon_vma_chain *avc;
1670 int ret = SWAP_AGAIN;
1673 * Note: remove_migration_ptes() cannot use page_lock_anon_vma()
1674 * because that depends on page_mapped(); but not all its usages
1675 * are holding mmap_sem. Users without mmap_sem are required to
1676 * take a reference count to prevent the anon_vma disappearing
1678 anon_vma = page_anon_vma(page);
1681 anon_vma_lock(anon_vma);
1682 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1683 struct vm_area_struct *vma = avc->vma;
1684 unsigned long address = vma_address(page, vma);
1685 ret = rmap_one(page, vma, address, arg);
1686 if (ret != SWAP_AGAIN)
1689 anon_vma_unlock(anon_vma);
1693 static int rmap_walk_file(struct page *page, int (*rmap_one)(struct page *,
1694 struct vm_area_struct *, unsigned long, void *), void *arg)
1696 struct address_space *mapping = page->mapping;
1697 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1698 struct vm_area_struct *vma;
1699 int ret = SWAP_AGAIN;
1703 mutex_lock(&mapping->i_mmap_mutex);
1704 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
1705 unsigned long address = vma_address(page, vma);
1706 ret = rmap_one(page, vma, address, arg);
1707 if (ret != SWAP_AGAIN)
1711 * No nonlinear handling: being always shared, nonlinear vmas
1712 * never contain migration ptes. Decide what to do about this
1713 * limitation to linear when we need rmap_walk() on nonlinear.
1715 mutex_unlock(&mapping->i_mmap_mutex);
1719 int rmap_walk(struct page *page, int (*rmap_one)(struct page *,
1720 struct vm_area_struct *, unsigned long, void *), void *arg)
1722 VM_BUG_ON(!PageLocked(page));
1724 if (unlikely(PageKsm(page)))
1725 return rmap_walk_ksm(page, rmap_one, arg);
1726 else if (PageAnon(page))
1727 return rmap_walk_anon(page, rmap_one, arg);
1729 return rmap_walk_file(page, rmap_one, arg);
1731 #endif /* CONFIG_MIGRATION */
1733 #ifdef CONFIG_HUGETLB_PAGE
1735 * The following three functions are for anonymous (private mapped) hugepages.
1736 * Unlike common anonymous pages, anonymous hugepages have no accounting code
1737 * and no lru code, because we handle hugepages differently from common pages.
1739 static void __hugepage_set_anon_rmap(struct page *page,
1740 struct vm_area_struct *vma, unsigned long address, int exclusive)
1742 struct anon_vma *anon_vma = vma->anon_vma;
1749 anon_vma = anon_vma->root;
1751 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1752 page->mapping = (struct address_space *) anon_vma;
1753 page->index = linear_page_index(vma, address);
1756 void hugepage_add_anon_rmap(struct page *page,
1757 struct vm_area_struct *vma, unsigned long address)
1759 struct anon_vma *anon_vma = vma->anon_vma;
1762 BUG_ON(!PageLocked(page));
1764 /* address might be in next vma when migration races vma_adjust */
1765 first = atomic_inc_and_test(&page->_mapcount);
1767 __hugepage_set_anon_rmap(page, vma, address, 0);
1770 void hugepage_add_new_anon_rmap(struct page *page,
1771 struct vm_area_struct *vma, unsigned long address)
1773 BUG_ON(address < vma->vm_start || address >= vma->vm_end);
1774 atomic_set(&page->_mapcount, 0);
1775 __hugepage_set_anon_rmap(page, vma, address, 1);
1777 #endif /* CONFIG_HUGETLB_PAGE */