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_rwsem
28 * mm->page_table_lock or pte_lock
29 * zone->lru_lock (in mark_page_accessed, isolate_lru_page)
30 * swap_lock (in swap_duplicate, swap_info_get)
31 * mmlist_lock (in mmput, drain_mmlist and others)
32 * mapping->private_lock (in __set_page_dirty_buffers)
33 * inode->i_lock (in set_page_dirty's __mark_inode_dirty)
34 * bdi.wb->list_lock (in set_page_dirty's __mark_inode_dirty)
35 * sb_lock (within inode_lock in fs/fs-writeback.c)
36 * mapping->tree_lock (widely used, in set_page_dirty,
37 * in arch-dependent flush_dcache_mmap_lock,
38 * within bdi.wb->list_lock in __sync_single_inode)
40 * anon_vma->rwsem,mapping->i_mutex (memory_failure, collect_procs_anon)
46 #include <linux/pagemap.h>
47 #include <linux/swap.h>
48 #include <linux/swapops.h>
49 #include <linux/slab.h>
50 #include <linux/init.h>
51 #include <linux/ksm.h>
52 #include <linux/rmap.h>
53 #include <linux/rcupdate.h>
54 #include <linux/export.h>
55 #include <linux/memcontrol.h>
56 #include <linux/mmu_notifier.h>
57 #include <linux/migrate.h>
58 #include <linux/hugetlb.h>
59 #include <linux/backing-dev.h>
61 #include <asm/tlbflush.h>
65 static struct kmem_cache *anon_vma_cachep;
66 static struct kmem_cache *anon_vma_chain_cachep;
68 static inline struct anon_vma *anon_vma_alloc(void)
70 struct anon_vma *anon_vma;
72 anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL);
74 atomic_set(&anon_vma->refcount, 1);
75 anon_vma->degree = 1; /* Reference for first vma */
76 anon_vma->parent = anon_vma;
78 * Initialise the anon_vma root to point to itself. If called
79 * from fork, the root will be reset to the parents anon_vma.
81 anon_vma->root = anon_vma;
87 static inline void anon_vma_free(struct anon_vma *anon_vma)
89 VM_BUG_ON(atomic_read(&anon_vma->refcount));
92 * Synchronize against page_lock_anon_vma_read() such that
93 * we can safely hold the lock without the anon_vma getting
96 * Relies on the full mb implied by the atomic_dec_and_test() from
97 * put_anon_vma() against the acquire barrier implied by
98 * down_read_trylock() from page_lock_anon_vma_read(). This orders:
100 * page_lock_anon_vma_read() VS put_anon_vma()
101 * down_read_trylock() atomic_dec_and_test()
103 * atomic_read() rwsem_is_locked()
105 * LOCK should suffice since the actual taking of the lock must
106 * happen _before_ what follows.
109 if (rwsem_is_locked(&anon_vma->root->rwsem)) {
110 anon_vma_lock_write(anon_vma);
111 anon_vma_unlock_write(anon_vma);
114 kmem_cache_free(anon_vma_cachep, anon_vma);
117 static inline struct anon_vma_chain *anon_vma_chain_alloc(gfp_t gfp)
119 return kmem_cache_alloc(anon_vma_chain_cachep, gfp);
122 static void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain)
124 kmem_cache_free(anon_vma_chain_cachep, anon_vma_chain);
127 static void anon_vma_chain_link(struct vm_area_struct *vma,
128 struct anon_vma_chain *avc,
129 struct anon_vma *anon_vma)
132 avc->anon_vma = anon_vma;
133 list_add(&avc->same_vma, &vma->anon_vma_chain);
134 anon_vma_interval_tree_insert(avc, &anon_vma->rb_root);
138 * anon_vma_prepare - attach an anon_vma to a memory region
139 * @vma: the memory region in question
141 * This makes sure the memory mapping described by 'vma' has
142 * an 'anon_vma' attached to it, so that we can associate the
143 * anonymous pages mapped into it with that anon_vma.
145 * The common case will be that we already have one, but if
146 * not we either need to find an adjacent mapping that we
147 * can re-use the anon_vma from (very common when the only
148 * reason for splitting a vma has been mprotect()), or we
149 * allocate a new one.
151 * Anon-vma allocations are very subtle, because we may have
152 * optimistically looked up an anon_vma in page_lock_anon_vma_read()
153 * and that may actually touch the spinlock even in the newly
154 * allocated vma (it depends on RCU to make sure that the
155 * anon_vma isn't actually destroyed).
157 * As a result, we need to do proper anon_vma locking even
158 * for the new allocation. At the same time, we do not want
159 * to do any locking for the common case of already having
162 * This must be called with the mmap_sem held for reading.
164 int anon_vma_prepare(struct vm_area_struct *vma)
166 struct anon_vma *anon_vma = vma->anon_vma;
167 struct anon_vma_chain *avc;
170 if (unlikely(!anon_vma)) {
171 struct mm_struct *mm = vma->vm_mm;
172 struct anon_vma *allocated;
174 avc = anon_vma_chain_alloc(GFP_KERNEL);
178 anon_vma = find_mergeable_anon_vma(vma);
181 anon_vma = anon_vma_alloc();
182 if (unlikely(!anon_vma))
183 goto out_enomem_free_avc;
184 allocated = anon_vma;
187 anon_vma_lock_write(anon_vma);
188 /* page_table_lock to protect against threads */
189 spin_lock(&mm->page_table_lock);
190 if (likely(!vma->anon_vma)) {
191 vma->anon_vma = anon_vma;
192 anon_vma_chain_link(vma, avc, anon_vma);
193 /* vma reference or self-parent link for new root */
198 spin_unlock(&mm->page_table_lock);
199 anon_vma_unlock_write(anon_vma);
201 if (unlikely(allocated))
202 put_anon_vma(allocated);
204 anon_vma_chain_free(avc);
209 anon_vma_chain_free(avc);
215 * This is a useful helper function for locking the anon_vma root as
216 * we traverse the vma->anon_vma_chain, looping over anon_vma's that
219 * Such anon_vma's should have the same root, so you'd expect to see
220 * just a single mutex_lock for the whole traversal.
222 static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma)
224 struct anon_vma *new_root = anon_vma->root;
225 if (new_root != root) {
226 if (WARN_ON_ONCE(root))
227 up_write(&root->rwsem);
229 down_write(&root->rwsem);
234 static inline void unlock_anon_vma_root(struct anon_vma *root)
237 up_write(&root->rwsem);
241 * Attach the anon_vmas from src to dst.
242 * Returns 0 on success, -ENOMEM on failure.
244 * If dst->anon_vma is NULL this function tries to find and reuse existing
245 * anon_vma which has no vmas and only one child anon_vma. This prevents
246 * degradation of anon_vma hierarchy to endless linear chain in case of
247 * constantly forking task. On the other hand, an anon_vma with more than one
248 * child isn't reused even if there was no alive vma, thus rmap walker has a
249 * good chance of avoiding scanning the whole hierarchy when it searches where
252 int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
254 struct anon_vma_chain *avc, *pavc;
255 struct anon_vma *root = NULL;
257 list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
258 struct anon_vma *anon_vma;
260 avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN);
261 if (unlikely(!avc)) {
262 unlock_anon_vma_root(root);
264 avc = anon_vma_chain_alloc(GFP_KERNEL);
268 anon_vma = pavc->anon_vma;
269 root = lock_anon_vma_root(root, anon_vma);
270 anon_vma_chain_link(dst, avc, anon_vma);
273 * Reuse existing anon_vma if its degree lower than two,
274 * that means it has no vma and only one anon_vma child.
276 * Do not chose parent anon_vma, otherwise first child
277 * will always reuse it. Root anon_vma is never reused:
278 * it has self-parent reference and at least one child.
280 if (!dst->anon_vma && anon_vma != src->anon_vma &&
281 anon_vma->degree < 2)
282 dst->anon_vma = anon_vma;
285 dst->anon_vma->degree++;
286 unlock_anon_vma_root(root);
291 * dst->anon_vma is dropped here otherwise its degree can be incorrectly
292 * decremented in unlink_anon_vmas().
293 * We can safely do this because callers of anon_vma_clone() don't care
294 * about dst->anon_vma if anon_vma_clone() failed.
296 dst->anon_vma = NULL;
297 unlink_anon_vmas(dst);
302 * Attach vma to its own anon_vma, as well as to the anon_vmas that
303 * the corresponding VMA in the parent process is attached to.
304 * Returns 0 on success, non-zero on failure.
306 int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
308 struct anon_vma_chain *avc;
309 struct anon_vma *anon_vma;
312 /* Don't bother if the parent process has no anon_vma here. */
316 /* Drop inherited anon_vma, we'll reuse existing or allocate new. */
317 vma->anon_vma = NULL;
320 * First, attach the new VMA to the parent VMA's anon_vmas,
321 * so rmap can find non-COWed pages in child processes.
323 error = anon_vma_clone(vma, pvma);
327 /* An existing anon_vma has been reused, all done then. */
331 /* Then add our own anon_vma. */
332 anon_vma = anon_vma_alloc();
335 avc = anon_vma_chain_alloc(GFP_KERNEL);
337 goto out_error_free_anon_vma;
340 * The root anon_vma's spinlock is the lock actually used when we
341 * lock any of the anon_vmas in this anon_vma tree.
343 anon_vma->root = pvma->anon_vma->root;
344 anon_vma->parent = pvma->anon_vma;
346 * With refcounts, an anon_vma can stay around longer than the
347 * process it belongs to. The root anon_vma needs to be pinned until
348 * this anon_vma is freed, because the lock lives in the root.
350 get_anon_vma(anon_vma->root);
351 /* Mark this anon_vma as the one where our new (COWed) pages go. */
352 vma->anon_vma = anon_vma;
353 anon_vma_lock_write(anon_vma);
354 anon_vma_chain_link(vma, avc, anon_vma);
355 anon_vma->parent->degree++;
356 anon_vma_unlock_write(anon_vma);
360 out_error_free_anon_vma:
361 put_anon_vma(anon_vma);
363 unlink_anon_vmas(vma);
367 void unlink_anon_vmas(struct vm_area_struct *vma)
369 struct anon_vma_chain *avc, *next;
370 struct anon_vma *root = NULL;
373 * Unlink each anon_vma chained to the VMA. This list is ordered
374 * from newest to oldest, ensuring the root anon_vma gets freed last.
376 list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
377 struct anon_vma *anon_vma = avc->anon_vma;
379 root = lock_anon_vma_root(root, anon_vma);
380 anon_vma_interval_tree_remove(avc, &anon_vma->rb_root);
383 * Leave empty anon_vmas on the list - we'll need
384 * to free them outside the lock.
386 if (RB_EMPTY_ROOT(&anon_vma->rb_root)) {
387 anon_vma->parent->degree--;
391 list_del(&avc->same_vma);
392 anon_vma_chain_free(avc);
395 vma->anon_vma->degree--;
396 unlock_anon_vma_root(root);
399 * Iterate the list once more, it now only contains empty and unlinked
400 * anon_vmas, destroy them. Could not do before due to __put_anon_vma()
401 * needing to write-acquire the anon_vma->root->rwsem.
403 list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
404 struct anon_vma *anon_vma = avc->anon_vma;
406 BUG_ON(anon_vma->degree);
407 put_anon_vma(anon_vma);
409 list_del(&avc->same_vma);
410 anon_vma_chain_free(avc);
414 static void anon_vma_ctor(void *data)
416 struct anon_vma *anon_vma = data;
418 init_rwsem(&anon_vma->rwsem);
419 atomic_set(&anon_vma->refcount, 0);
420 anon_vma->rb_root = RB_ROOT;
423 void __init anon_vma_init(void)
425 anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
426 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor);
427 anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain, SLAB_PANIC);
431 * Getting a lock on a stable anon_vma from a page off the LRU is tricky!
433 * Since there is no serialization what so ever against page_remove_rmap()
434 * the best this function can do is return a locked anon_vma that might
435 * have been relevant to this page.
437 * The page might have been remapped to a different anon_vma or the anon_vma
438 * returned may already be freed (and even reused).
440 * In case it was remapped to a different anon_vma, the new anon_vma will be a
441 * child of the old anon_vma, and the anon_vma lifetime rules will therefore
442 * ensure that any anon_vma obtained from the page will still be valid for as
443 * long as we observe page_mapped() [ hence all those page_mapped() tests ].
445 * All users of this function must be very careful when walking the anon_vma
446 * chain and verify that the page in question is indeed mapped in it
447 * [ something equivalent to page_mapped_in_vma() ].
449 * Since anon_vma's slab is DESTROY_BY_RCU and we know from page_remove_rmap()
450 * that the anon_vma pointer from page->mapping is valid if there is a
451 * mapcount, we can dereference the anon_vma after observing those.
453 struct anon_vma *page_get_anon_vma(struct page *page)
455 struct anon_vma *anon_vma = NULL;
456 unsigned long anon_mapping;
459 anon_mapping = (unsigned long)READ_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 if (!atomic_inc_not_zero(&anon_vma->refcount)) {
472 * If this page is still mapped, then its anon_vma cannot have been
473 * freed. But if it has been unmapped, we have no security against the
474 * anon_vma structure being freed and reused (for another anon_vma:
475 * SLAB_DESTROY_BY_RCU guarantees that - so the atomic_inc_not_zero()
476 * above cannot corrupt).
478 if (!page_mapped(page)) {
480 put_anon_vma(anon_vma);
490 * Similar to page_get_anon_vma() except it locks the anon_vma.
492 * Its a little more complex as it tries to keep the fast path to a single
493 * atomic op -- the trylock. If we fail the trylock, we fall back to getting a
494 * reference like with page_get_anon_vma() and then block on the mutex.
496 struct anon_vma *page_lock_anon_vma_read(struct page *page)
498 struct anon_vma *anon_vma = NULL;
499 struct anon_vma *root_anon_vma;
500 unsigned long anon_mapping;
503 anon_mapping = (unsigned long)READ_ONCE(page->mapping);
504 if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
506 if (!page_mapped(page))
509 anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
510 root_anon_vma = READ_ONCE(anon_vma->root);
511 if (down_read_trylock(&root_anon_vma->rwsem)) {
513 * If the page is still mapped, then this anon_vma is still
514 * its anon_vma, and holding the mutex ensures that it will
515 * not go away, see anon_vma_free().
517 if (!page_mapped(page)) {
518 up_read(&root_anon_vma->rwsem);
524 /* trylock failed, we got to sleep */
525 if (!atomic_inc_not_zero(&anon_vma->refcount)) {
530 if (!page_mapped(page)) {
532 put_anon_vma(anon_vma);
536 /* we pinned the anon_vma, its safe to sleep */
538 anon_vma_lock_read(anon_vma);
540 if (atomic_dec_and_test(&anon_vma->refcount)) {
542 * Oops, we held the last refcount, release the lock
543 * and bail -- can't simply use put_anon_vma() because
544 * we'll deadlock on the anon_vma_lock_write() recursion.
546 anon_vma_unlock_read(anon_vma);
547 __put_anon_vma(anon_vma);
558 void page_unlock_anon_vma_read(struct anon_vma *anon_vma)
560 anon_vma_unlock_read(anon_vma);
564 * At what user virtual address is page expected in @vma?
566 static inline unsigned long
567 __vma_address(struct page *page, struct vm_area_struct *vma)
569 pgoff_t pgoff = page_to_pgoff(page);
570 return vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
574 vma_address(struct page *page, struct vm_area_struct *vma)
576 unsigned long address = __vma_address(page, vma);
578 /* page should be within @vma mapping range */
579 VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
585 * At what user virtual address is page expected in vma?
586 * Caller should check the page is actually part of the vma.
588 unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
590 unsigned long address;
591 if (PageAnon(page)) {
592 struct anon_vma *page__anon_vma = page_anon_vma(page);
594 * Note: swapoff's unuse_vma() is more efficient with this
595 * check, and needs it to match anon_vma when KSM is active.
597 if (!vma->anon_vma || !page__anon_vma ||
598 vma->anon_vma->root != page__anon_vma->root)
600 } else if (page->mapping) {
601 if (!vma->vm_file || vma->vm_file->f_mapping != page->mapping)
605 address = __vma_address(page, vma);
606 if (unlikely(address < vma->vm_start || address >= vma->vm_end))
611 pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address)
618 pgd = pgd_offset(mm, address);
619 if (!pgd_present(*pgd))
622 pud = pud_offset(pgd, address);
623 if (!pud_present(*pud))
626 pmd = pmd_offset(pud, address);
628 * Some THP functions use the sequence pmdp_huge_clear_flush(), set_pmd_at()
629 * without holding anon_vma lock for write. So when looking for a
630 * genuine pmde (in which to find pte), test present and !THP together.
634 if (!pmd_present(pmde) || pmd_trans_huge(pmde))
641 * Check that @page is mapped at @address into @mm.
643 * If @sync is false, page_check_address may perform a racy check to avoid
644 * the page table lock when the pte is not present (helpful when reclaiming
645 * highly shared pages).
647 * On success returns with pte mapped and locked.
649 pte_t *__page_check_address(struct page *page, struct mm_struct *mm,
650 unsigned long address, spinlock_t **ptlp, int sync)
656 if (unlikely(PageHuge(page))) {
657 /* when pud is not present, pte will be NULL */
658 pte = huge_pte_offset(mm, address);
662 ptl = huge_pte_lockptr(page_hstate(page), mm, pte);
666 pmd = mm_find_pmd(mm, address);
670 pte = pte_offset_map(pmd, address);
671 /* Make a quick check before getting the lock */
672 if (!sync && !pte_present(*pte)) {
677 ptl = pte_lockptr(mm, pmd);
680 if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) {
684 pte_unmap_unlock(pte, ptl);
689 * page_mapped_in_vma - check whether a page is really mapped in a VMA
690 * @page: the page to test
691 * @vma: the VMA to test
693 * Returns 1 if the page is mapped into the page tables of the VMA, 0
694 * if the page is not mapped into the page tables of this VMA. Only
695 * valid for normal file or anonymous VMAs.
697 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
699 unsigned long address;
703 address = __vma_address(page, vma);
704 if (unlikely(address < vma->vm_start || address >= vma->vm_end))
706 pte = page_check_address(page, vma->vm_mm, address, &ptl, 1);
707 if (!pte) /* the page is not in this mm */
709 pte_unmap_unlock(pte, ptl);
714 struct page_referenced_arg {
717 unsigned long vm_flags;
718 struct mem_cgroup *memcg;
721 * arg: page_referenced_arg will be passed
723 static int page_referenced_one(struct page *page, struct vm_area_struct *vma,
724 unsigned long address, void *arg)
726 struct mm_struct *mm = vma->vm_mm;
729 struct page_referenced_arg *pra = arg;
731 if (unlikely(PageTransHuge(page))) {
735 * rmap might return false positives; we must filter
736 * these out using page_check_address_pmd().
738 pmd = page_check_address_pmd(page, mm, address,
739 PAGE_CHECK_ADDRESS_PMD_FLAG, &ptl);
743 if (vma->vm_flags & VM_LOCKED) {
745 pra->vm_flags |= VM_LOCKED;
746 return SWAP_FAIL; /* To break the loop */
749 /* go ahead even if the pmd is pmd_trans_splitting() */
750 if (pmdp_clear_flush_young_notify(vma, address, pmd))
757 * rmap might return false positives; we must filter
758 * these out using page_check_address().
760 pte = page_check_address(page, mm, address, &ptl, 0);
764 if (vma->vm_flags & VM_LOCKED) {
765 pte_unmap_unlock(pte, ptl);
766 pra->vm_flags |= VM_LOCKED;
767 return SWAP_FAIL; /* To break the loop */
770 if (ptep_clear_flush_young_notify(vma, address, pte)) {
772 * Don't treat a reference through a sequentially read
773 * mapping as such. If the page has been used in
774 * another mapping, we will catch it; if this other
775 * mapping is already gone, the unmap path will have
776 * set PG_referenced or activated the page.
778 if (likely(!(vma->vm_flags & VM_SEQ_READ)))
781 pte_unmap_unlock(pte, ptl);
786 pra->vm_flags |= vma->vm_flags;
791 return SWAP_SUCCESS; /* To break the loop */
796 static bool invalid_page_referenced_vma(struct vm_area_struct *vma, void *arg)
798 struct page_referenced_arg *pra = arg;
799 struct mem_cgroup *memcg = pra->memcg;
801 if (!mm_match_cgroup(vma->vm_mm, memcg))
808 * page_referenced - test if the page was referenced
809 * @page: the page to test
810 * @is_locked: caller holds lock on the page
811 * @memcg: target memory cgroup
812 * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
814 * Quick test_and_clear_referenced for all mappings to a page,
815 * returns the number of ptes which referenced the page.
817 int page_referenced(struct page *page,
819 struct mem_cgroup *memcg,
820 unsigned long *vm_flags)
824 struct page_referenced_arg pra = {
825 .mapcount = page_mapcount(page),
828 struct rmap_walk_control rwc = {
829 .rmap_one = page_referenced_one,
831 .anon_lock = page_lock_anon_vma_read,
835 if (!page_mapped(page))
838 if (!page_rmapping(page))
841 if (!is_locked && (!PageAnon(page) || PageKsm(page))) {
842 we_locked = trylock_page(page);
848 * If we are reclaiming on behalf of a cgroup, skip
849 * counting on behalf of references from different
853 rwc.invalid_vma = invalid_page_referenced_vma;
856 ret = rmap_walk(page, &rwc);
857 *vm_flags = pra.vm_flags;
862 return pra.referenced;
865 static int page_mkclean_one(struct page *page, struct vm_area_struct *vma,
866 unsigned long address, void *arg)
868 struct mm_struct *mm = vma->vm_mm;
874 pte = page_check_address(page, mm, address, &ptl, 1);
878 if (pte_dirty(*pte) || pte_write(*pte)) {
881 flush_cache_page(vma, address, pte_pfn(*pte));
882 entry = ptep_clear_flush(vma, address, pte);
883 entry = pte_wrprotect(entry);
884 entry = pte_mkclean(entry);
885 set_pte_at(mm, address, pte, entry);
889 pte_unmap_unlock(pte, ptl);
892 mmu_notifier_invalidate_page(mm, address);
899 static bool invalid_mkclean_vma(struct vm_area_struct *vma, void *arg)
901 if (vma->vm_flags & VM_SHARED)
907 int page_mkclean(struct page *page)
910 struct address_space *mapping;
911 struct rmap_walk_control rwc = {
912 .arg = (void *)&cleaned,
913 .rmap_one = page_mkclean_one,
914 .invalid_vma = invalid_mkclean_vma,
917 BUG_ON(!PageLocked(page));
919 if (!page_mapped(page))
922 mapping = page_mapping(page);
926 rmap_walk(page, &rwc);
930 EXPORT_SYMBOL_GPL(page_mkclean);
933 * page_move_anon_rmap - move a page to our anon_vma
934 * @page: the page to move to our anon_vma
935 * @vma: the vma the page belongs to
936 * @address: the user virtual address mapped
938 * When a page belongs exclusively to one process after a COW event,
939 * that page can be moved into the anon_vma that belongs to just that
940 * process, so the rmap code will not search the parent or sibling
943 void page_move_anon_rmap(struct page *page,
944 struct vm_area_struct *vma, unsigned long address)
946 struct anon_vma *anon_vma = vma->anon_vma;
948 VM_BUG_ON_PAGE(!PageLocked(page), page);
949 VM_BUG_ON_VMA(!anon_vma, vma);
950 VM_BUG_ON_PAGE(page->index != linear_page_index(vma, address), page);
952 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
954 * Ensure that anon_vma and the PAGE_MAPPING_ANON bit are written
955 * simultaneously, so a concurrent reader (eg page_referenced()'s
956 * PageAnon()) will not see one without the other.
958 WRITE_ONCE(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);
1046 * We use the irq-unsafe __{inc|mod}_zone_page_stat because
1047 * these counters are not modified in interrupt context, and
1048 * pte lock(a spinlock) is held, which implies preemption
1051 if (PageTransHuge(page))
1052 __inc_zone_page_state(page,
1053 NR_ANON_TRANSPARENT_HUGEPAGES);
1054 __mod_zone_page_state(page_zone(page), NR_ANON_PAGES,
1055 hpage_nr_pages(page));
1057 if (unlikely(PageKsm(page)))
1060 VM_BUG_ON_PAGE(!PageLocked(page), page);
1061 /* address might be in next vma when migration races vma_adjust */
1063 __page_set_anon_rmap(page, vma, address, exclusive);
1065 __page_check_anon_rmap(page, vma, address);
1069 * page_add_new_anon_rmap - add pte mapping to a new anonymous page
1070 * @page: the page to add the mapping to
1071 * @vma: the vm area in which the mapping is added
1072 * @address: the user virtual address mapped
1074 * Same as page_add_anon_rmap but must only be called on *new* pages.
1075 * This means the inc-and-test can be bypassed.
1076 * Page does not have to be locked.
1078 void page_add_new_anon_rmap(struct page *page,
1079 struct vm_area_struct *vma, unsigned long address)
1081 VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
1082 SetPageSwapBacked(page);
1083 atomic_set(&page->_mapcount, 0); /* increment count (starts at -1) */
1084 if (PageTransHuge(page))
1085 __inc_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
1086 __mod_zone_page_state(page_zone(page), NR_ANON_PAGES,
1087 hpage_nr_pages(page));
1088 __page_set_anon_rmap(page, vma, address, 1);
1092 * page_add_file_rmap - add pte mapping to a file page
1093 * @page: the page to add the mapping to
1095 * The caller needs to hold the pte lock.
1097 void page_add_file_rmap(struct page *page)
1099 struct mem_cgroup *memcg;
1101 memcg = mem_cgroup_begin_page_stat(page);
1102 if (atomic_inc_and_test(&page->_mapcount)) {
1103 __inc_zone_page_state(page, NR_FILE_MAPPED);
1104 mem_cgroup_inc_page_stat(memcg, MEM_CGROUP_STAT_FILE_MAPPED);
1106 mem_cgroup_end_page_stat(memcg);
1109 static void page_remove_file_rmap(struct page *page)
1111 struct mem_cgroup *memcg;
1113 memcg = mem_cgroup_begin_page_stat(page);
1115 /* page still mapped by someone else? */
1116 if (!atomic_add_negative(-1, &page->_mapcount))
1119 /* Hugepages are not counted in NR_FILE_MAPPED for now. */
1120 if (unlikely(PageHuge(page)))
1124 * We use the irq-unsafe __{inc|mod}_zone_page_stat because
1125 * these counters are not modified in interrupt context, and
1126 * pte lock(a spinlock) is held, which implies preemption disabled.
1128 __dec_zone_page_state(page, NR_FILE_MAPPED);
1129 mem_cgroup_dec_page_stat(memcg, MEM_CGROUP_STAT_FILE_MAPPED);
1131 if (unlikely(PageMlocked(page)))
1132 clear_page_mlock(page);
1134 mem_cgroup_end_page_stat(memcg);
1138 * page_remove_rmap - take down pte mapping from a page
1139 * @page: page to remove mapping from
1141 * The caller needs to hold the pte lock.
1143 void page_remove_rmap(struct page *page)
1145 if (!PageAnon(page)) {
1146 page_remove_file_rmap(page);
1150 /* page still mapped by someone else? */
1151 if (!atomic_add_negative(-1, &page->_mapcount))
1154 /* Hugepages are not counted in NR_ANON_PAGES for now. */
1155 if (unlikely(PageHuge(page)))
1159 * We use the irq-unsafe __{inc|mod}_zone_page_stat because
1160 * these counters are not modified in interrupt context, and
1161 * pte lock(a spinlock) is held, which implies preemption disabled.
1163 if (PageTransHuge(page))
1164 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
1166 __mod_zone_page_state(page_zone(page), NR_ANON_PAGES,
1167 -hpage_nr_pages(page));
1169 if (unlikely(PageMlocked(page)))
1170 clear_page_mlock(page);
1173 * It would be tidy to reset the PageAnon mapping here,
1174 * but that might overwrite a racing page_add_anon_rmap
1175 * which increments mapcount after us but sets mapping
1176 * before us: so leave the reset to free_hot_cold_page,
1177 * and remember that it's only reliable while mapped.
1178 * Leaving it set also helps swapoff to reinstate ptes
1179 * faster for those pages still in swapcache.
1184 * @arg: enum ttu_flags will be passed to this argument
1186 static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
1187 unsigned long address, void *arg)
1189 struct mm_struct *mm = vma->vm_mm;
1193 int ret = SWAP_AGAIN;
1194 enum ttu_flags flags = (enum ttu_flags)arg;
1196 pte = page_check_address(page, mm, address, &ptl, 0);
1201 * If the page is mlock()d, we cannot swap it out.
1202 * If it's recently referenced (perhaps page_referenced
1203 * skipped over this mm) then we should reactivate it.
1205 if (!(flags & TTU_IGNORE_MLOCK)) {
1206 if (vma->vm_flags & VM_LOCKED)
1209 if (flags & TTU_MUNLOCK)
1212 if (!(flags & TTU_IGNORE_ACCESS)) {
1213 if (ptep_clear_flush_young_notify(vma, address, pte)) {
1219 /* Nuke the page table entry. */
1220 flush_cache_page(vma, address, page_to_pfn(page));
1221 pteval = ptep_clear_flush(vma, address, pte);
1223 /* Move the dirty bit to the physical page now the pte is gone. */
1224 if (pte_dirty(pteval))
1225 set_page_dirty(page);
1227 /* Update high watermark before we lower rss */
1228 update_hiwater_rss(mm);
1230 if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
1231 if (!PageHuge(page)) {
1233 dec_mm_counter(mm, MM_ANONPAGES);
1235 dec_mm_counter(mm, MM_FILEPAGES);
1237 set_pte_at(mm, address, pte,
1238 swp_entry_to_pte(make_hwpoison_entry(page)));
1239 } else if (pte_unused(pteval)) {
1241 * The guest indicated that the page content is of no
1242 * interest anymore. Simply discard the pte, vmscan
1243 * will take care of the rest.
1246 dec_mm_counter(mm, MM_ANONPAGES);
1248 dec_mm_counter(mm, MM_FILEPAGES);
1249 } else if (PageAnon(page)) {
1250 swp_entry_t entry = { .val = page_private(page) };
1253 if (PageSwapCache(page)) {
1255 * Store the swap location in the pte.
1256 * See handle_pte_fault() ...
1258 if (swap_duplicate(entry) < 0) {
1259 set_pte_at(mm, address, pte, pteval);
1263 if (list_empty(&mm->mmlist)) {
1264 spin_lock(&mmlist_lock);
1265 if (list_empty(&mm->mmlist))
1266 list_add(&mm->mmlist, &init_mm.mmlist);
1267 spin_unlock(&mmlist_lock);
1269 dec_mm_counter(mm, MM_ANONPAGES);
1270 inc_mm_counter(mm, MM_SWAPENTS);
1271 } else if (IS_ENABLED(CONFIG_MIGRATION)) {
1273 * Store the pfn of the page in a special migration
1274 * pte. do_swap_page() will wait until the migration
1275 * pte is removed and then restart fault handling.
1277 BUG_ON(!(flags & TTU_MIGRATION));
1278 entry = make_migration_entry(page, pte_write(pteval));
1280 swp_pte = swp_entry_to_pte(entry);
1281 if (pte_soft_dirty(pteval))
1282 swp_pte = pte_swp_mksoft_dirty(swp_pte);
1283 set_pte_at(mm, address, pte, swp_pte);
1284 } else if (IS_ENABLED(CONFIG_MIGRATION) &&
1285 (flags & TTU_MIGRATION)) {
1286 /* Establish migration entry for a file page */
1288 entry = make_migration_entry(page, pte_write(pteval));
1289 set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
1291 dec_mm_counter(mm, MM_FILEPAGES);
1293 page_remove_rmap(page);
1294 page_cache_release(page);
1297 pte_unmap_unlock(pte, ptl);
1298 if (ret != SWAP_FAIL && !(flags & TTU_MUNLOCK))
1299 mmu_notifier_invalidate_page(mm, address);
1304 pte_unmap_unlock(pte, ptl);
1308 * We need mmap_sem locking, Otherwise VM_LOCKED check makes
1309 * unstable result and race. Plus, We can't wait here because
1310 * we now hold anon_vma->rwsem or mapping->i_mmap_rwsem.
1311 * if trylock failed, the page remain in evictable lru and later
1312 * vmscan could retry to move the page to unevictable lru if the
1313 * page is actually mlocked.
1315 if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
1316 if (vma->vm_flags & VM_LOCKED) {
1317 mlock_vma_page(page);
1320 up_read(&vma->vm_mm->mmap_sem);
1325 bool is_vma_temporary_stack(struct vm_area_struct *vma)
1327 int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP);
1332 if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) ==
1333 VM_STACK_INCOMPLETE_SETUP)
1339 static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg)
1341 return is_vma_temporary_stack(vma);
1344 static int page_not_mapped(struct page *page)
1346 return !page_mapped(page);
1350 * try_to_unmap - try to remove all page table mappings to a page
1351 * @page: the page to get unmapped
1352 * @flags: action and flags
1354 * Tries to remove all the page table entries which are mapping this
1355 * page, used in the pageout path. Caller must hold the page lock.
1356 * Return values are:
1358 * SWAP_SUCCESS - we succeeded in removing all mappings
1359 * SWAP_AGAIN - we missed a mapping, try again later
1360 * SWAP_FAIL - the page is unswappable
1361 * SWAP_MLOCK - page is mlocked.
1363 int try_to_unmap(struct page *page, enum ttu_flags flags)
1366 struct rmap_walk_control rwc = {
1367 .rmap_one = try_to_unmap_one,
1368 .arg = (void *)flags,
1369 .done = page_not_mapped,
1370 .anon_lock = page_lock_anon_vma_read,
1373 VM_BUG_ON_PAGE(!PageHuge(page) && PageTransHuge(page), page);
1376 * During exec, a temporary VMA is setup and later moved.
1377 * The VMA is moved under the anon_vma lock but not the
1378 * page tables leading to a race where migration cannot
1379 * find the migration ptes. Rather than increasing the
1380 * locking requirements of exec(), migration skips
1381 * temporary VMAs until after exec() completes.
1383 if ((flags & TTU_MIGRATION) && !PageKsm(page) && PageAnon(page))
1384 rwc.invalid_vma = invalid_migration_vma;
1386 ret = rmap_walk(page, &rwc);
1388 if (ret != SWAP_MLOCK && !page_mapped(page))
1394 * try_to_munlock - try to munlock a page
1395 * @page: the page to be munlocked
1397 * Called from munlock code. Checks all of the VMAs mapping the page
1398 * to make sure nobody else has this page mlocked. The page will be
1399 * returned with PG_mlocked cleared if no other vmas have it mlocked.
1401 * Return values are:
1403 * SWAP_AGAIN - no vma is holding page mlocked, or,
1404 * SWAP_AGAIN - page mapped in mlocked vma -- couldn't acquire mmap sem
1405 * SWAP_FAIL - page cannot be located at present
1406 * SWAP_MLOCK - page is now mlocked.
1408 int try_to_munlock(struct page *page)
1411 struct rmap_walk_control rwc = {
1412 .rmap_one = try_to_unmap_one,
1413 .arg = (void *)TTU_MUNLOCK,
1414 .done = page_not_mapped,
1415 .anon_lock = page_lock_anon_vma_read,
1419 VM_BUG_ON_PAGE(!PageLocked(page) || PageLRU(page), page);
1421 ret = rmap_walk(page, &rwc);
1425 void __put_anon_vma(struct anon_vma *anon_vma)
1427 struct anon_vma *root = anon_vma->root;
1429 anon_vma_free(anon_vma);
1430 if (root != anon_vma && atomic_dec_and_test(&root->refcount))
1431 anon_vma_free(root);
1434 static struct anon_vma *rmap_walk_anon_lock(struct page *page,
1435 struct rmap_walk_control *rwc)
1437 struct anon_vma *anon_vma;
1440 return rwc->anon_lock(page);
1443 * Note: remove_migration_ptes() cannot use page_lock_anon_vma_read()
1444 * because that depends on page_mapped(); but not all its usages
1445 * are holding mmap_sem. Users without mmap_sem are required to
1446 * take a reference count to prevent the anon_vma disappearing
1448 anon_vma = page_anon_vma(page);
1452 anon_vma_lock_read(anon_vma);
1457 * rmap_walk_anon - do something to anonymous page using the object-based
1459 * @page: the page to be handled
1460 * @rwc: control variable according to each walk type
1462 * Find all the mappings of a page using the mapping pointer and the vma chains
1463 * contained in the anon_vma struct it points to.
1465 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1466 * where the page was found will be held for write. So, we won't recheck
1467 * vm_flags for that VMA. That should be OK, because that vma shouldn't be
1470 static int rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc)
1472 struct anon_vma *anon_vma;
1474 struct anon_vma_chain *avc;
1475 int ret = SWAP_AGAIN;
1477 anon_vma = rmap_walk_anon_lock(page, rwc);
1481 pgoff = page_to_pgoff(page);
1482 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1483 struct vm_area_struct *vma = avc->vma;
1484 unsigned long address = vma_address(page, vma);
1486 if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
1489 ret = rwc->rmap_one(page, vma, address, rwc->arg);
1490 if (ret != SWAP_AGAIN)
1492 if (rwc->done && rwc->done(page))
1495 anon_vma_unlock_read(anon_vma);
1500 * rmap_walk_file - do something to file page using the object-based rmap method
1501 * @page: the page to be handled
1502 * @rwc: control variable according to each walk type
1504 * Find all the mappings of a page using the mapping pointer and the vma chains
1505 * contained in the address_space struct it points to.
1507 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1508 * where the page was found will be held for write. So, we won't recheck
1509 * vm_flags for that VMA. That should be OK, because that vma shouldn't be
1512 static int rmap_walk_file(struct page *page, struct rmap_walk_control *rwc)
1514 struct address_space *mapping = page->mapping;
1516 struct vm_area_struct *vma;
1517 int ret = SWAP_AGAIN;
1520 * The page lock not only makes sure that page->mapping cannot
1521 * suddenly be NULLified by truncation, it makes sure that the
1522 * structure at mapping cannot be freed and reused yet,
1523 * so we can safely take mapping->i_mmap_rwsem.
1525 VM_BUG_ON_PAGE(!PageLocked(page), page);
1530 pgoff = page_to_pgoff(page);
1531 i_mmap_lock_read(mapping);
1532 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
1533 unsigned long address = vma_address(page, vma);
1535 if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
1538 ret = rwc->rmap_one(page, vma, address, rwc->arg);
1539 if (ret != SWAP_AGAIN)
1541 if (rwc->done && rwc->done(page))
1546 i_mmap_unlock_read(mapping);
1550 int rmap_walk(struct page *page, struct rmap_walk_control *rwc)
1552 if (unlikely(PageKsm(page)))
1553 return rmap_walk_ksm(page, rwc);
1554 else if (PageAnon(page))
1555 return rmap_walk_anon(page, rwc);
1557 return rmap_walk_file(page, rwc);
1560 #ifdef CONFIG_HUGETLB_PAGE
1562 * The following three functions are for anonymous (private mapped) hugepages.
1563 * Unlike common anonymous pages, anonymous hugepages have no accounting code
1564 * and no lru code, because we handle hugepages differently from common pages.
1566 static void __hugepage_set_anon_rmap(struct page *page,
1567 struct vm_area_struct *vma, unsigned long address, int exclusive)
1569 struct anon_vma *anon_vma = vma->anon_vma;
1576 anon_vma = anon_vma->root;
1578 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1579 page->mapping = (struct address_space *) anon_vma;
1580 page->index = linear_page_index(vma, address);
1583 void hugepage_add_anon_rmap(struct page *page,
1584 struct vm_area_struct *vma, unsigned long address)
1586 struct anon_vma *anon_vma = vma->anon_vma;
1589 BUG_ON(!PageLocked(page));
1591 /* address might be in next vma when migration races vma_adjust */
1592 first = atomic_inc_and_test(&page->_mapcount);
1594 __hugepage_set_anon_rmap(page, vma, address, 0);
1597 void hugepage_add_new_anon_rmap(struct page *page,
1598 struct vm_area_struct *vma, unsigned long address)
1600 BUG_ON(address < vma->vm_start || address >= vma->vm_end);
1601 atomic_set(&page->_mapcount, 0);
1602 __hugepage_set_anon_rmap(page, vma, address, 1);
1604 #endif /* CONFIG_HUGETLB_PAGE */