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);
132 * It's critical to add new vmas to the tail of the anon_vma,
133 * see comment in huge_memory.c:__split_huge_page().
135 list_add_tail(&avc->same_anon_vma, &anon_vma->head);
139 * anon_vma_prepare - attach an anon_vma to a memory region
140 * @vma: the memory region in question
142 * This makes sure the memory mapping described by 'vma' has
143 * an 'anon_vma' attached to it, so that we can associate the
144 * anonymous pages mapped into it with that anon_vma.
146 * The common case will be that we already have one, but if
147 * not we either need to find an adjacent mapping that we
148 * can re-use the anon_vma from (very common when the only
149 * reason for splitting a vma has been mprotect()), or we
150 * allocate a new one.
152 * Anon-vma allocations are very subtle, because we may have
153 * optimistically looked up an anon_vma in page_lock_anon_vma()
154 * and that may actually touch the spinlock even in the newly
155 * allocated vma (it depends on RCU to make sure that the
156 * anon_vma isn't actually destroyed).
158 * As a result, we need to do proper anon_vma locking even
159 * for the new allocation. At the same time, we do not want
160 * to do any locking for the common case of already having
163 * This must be called with the mmap_sem held for reading.
165 int anon_vma_prepare(struct vm_area_struct *vma)
167 struct anon_vma *anon_vma = vma->anon_vma;
168 struct anon_vma_chain *avc;
171 if (unlikely(!anon_vma)) {
172 struct mm_struct *mm = vma->vm_mm;
173 struct anon_vma *allocated;
175 avc = anon_vma_chain_alloc(GFP_KERNEL);
179 anon_vma = find_mergeable_anon_vma(vma);
182 anon_vma = anon_vma_alloc();
183 if (unlikely(!anon_vma))
184 goto out_enomem_free_avc;
185 allocated = anon_vma;
188 anon_vma_lock(anon_vma);
189 /* page_table_lock to protect against threads */
190 spin_lock(&mm->page_table_lock);
191 if (likely(!vma->anon_vma)) {
192 vma->anon_vma = anon_vma;
193 anon_vma_chain_link(vma, avc, anon_vma);
197 spin_unlock(&mm->page_table_lock);
198 anon_vma_unlock(anon_vma);
200 if (unlikely(allocated))
201 put_anon_vma(allocated);
203 anon_vma_chain_free(avc);
208 anon_vma_chain_free(avc);
214 * This is a useful helper function for locking the anon_vma root as
215 * we traverse the vma->anon_vma_chain, looping over anon_vma's that
218 * Such anon_vma's should have the same root, so you'd expect to see
219 * just a single mutex_lock for the whole traversal.
221 static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma)
223 struct anon_vma *new_root = anon_vma->root;
224 if (new_root != root) {
225 if (WARN_ON_ONCE(root))
226 mutex_unlock(&root->mutex);
228 mutex_lock(&root->mutex);
233 static inline void unlock_anon_vma_root(struct anon_vma *root)
236 mutex_unlock(&root->mutex);
240 * Attach the anon_vmas from src to dst.
241 * Returns 0 on success, -ENOMEM on failure.
243 int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
245 struct anon_vma_chain *avc, *pavc;
246 struct anon_vma *root = NULL;
248 list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
249 struct anon_vma *anon_vma;
251 avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN);
252 if (unlikely(!avc)) {
253 unlock_anon_vma_root(root);
255 avc = anon_vma_chain_alloc(GFP_KERNEL);
259 anon_vma = pavc->anon_vma;
260 root = lock_anon_vma_root(root, anon_vma);
261 anon_vma_chain_link(dst, avc, anon_vma);
263 unlock_anon_vma_root(root);
267 unlink_anon_vmas(dst);
272 * Some rmap walk that needs to find all ptes/hugepmds without false
273 * negatives (like migrate and split_huge_page) running concurrent
274 * with operations that copy or move pagetables (like mremap() and
275 * fork()) to be safe. They depend on the anon_vma "same_anon_vma"
276 * list to be in a certain order: the dst_vma must be placed after the
277 * src_vma in the list. This is always guaranteed by fork() but
278 * mremap() needs to call this function to enforce it in case the
279 * dst_vma isn't newly allocated and chained with the anon_vma_clone()
280 * function but just an extension of a pre-existing vma through
283 * NOTE: the same_anon_vma list can still be changed by other
284 * processes while mremap runs because mremap doesn't hold the
285 * anon_vma mutex to prevent modifications to the list while it
286 * runs. All we need to enforce is that the relative order of this
287 * process vmas isn't changing (we don't care about other vmas
288 * order). Each vma corresponds to an anon_vma_chain structure so
289 * there's no risk that other processes calling anon_vma_moveto_tail()
290 * and changing the same_anon_vma list under mremap() will screw with
291 * the relative order of this process vmas in the list, because we
292 * they can't alter the order of any vma that belongs to this
293 * process. And there can't be another anon_vma_moveto_tail() running
294 * concurrently with mremap() coming from this process because we hold
295 * the mmap_sem for the whole mremap(). fork() ordering dependency
296 * also shouldn't be affected because fork() only cares that the
297 * parent vmas are placed in the list before the child vmas and
298 * anon_vma_moveto_tail() won't reorder vmas from either the fork()
301 void anon_vma_moveto_tail(struct vm_area_struct *dst)
303 struct anon_vma_chain *pavc;
304 struct anon_vma *root = NULL;
306 list_for_each_entry_reverse(pavc, &dst->anon_vma_chain, same_vma) {
307 struct anon_vma *anon_vma = pavc->anon_vma;
308 VM_BUG_ON(pavc->vma != dst);
309 root = lock_anon_vma_root(root, anon_vma);
310 list_del(&pavc->same_anon_vma);
311 list_add_tail(&pavc->same_anon_vma, &anon_vma->head);
313 unlock_anon_vma_root(root);
317 * Attach vma to its own anon_vma, as well as to the anon_vmas that
318 * the corresponding VMA in the parent process is attached to.
319 * Returns 0 on success, non-zero on failure.
321 int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
323 struct anon_vma_chain *avc;
324 struct anon_vma *anon_vma;
326 /* Don't bother if the parent process has no anon_vma here. */
331 * First, attach the new VMA to the parent VMA's anon_vmas,
332 * so rmap can find non-COWed pages in child processes.
334 if (anon_vma_clone(vma, pvma))
337 /* Then add our own anon_vma. */
338 anon_vma = anon_vma_alloc();
341 avc = anon_vma_chain_alloc(GFP_KERNEL);
343 goto out_error_free_anon_vma;
346 * The root anon_vma's spinlock is the lock actually used when we
347 * lock any of the anon_vmas in this anon_vma tree.
349 anon_vma->root = pvma->anon_vma->root;
351 * With refcounts, an anon_vma can stay around longer than the
352 * process it belongs to. The root anon_vma needs to be pinned until
353 * this anon_vma is freed, because the lock lives in the root.
355 get_anon_vma(anon_vma->root);
356 /* Mark this anon_vma as the one where our new (COWed) pages go. */
357 vma->anon_vma = anon_vma;
358 anon_vma_lock(anon_vma);
359 anon_vma_chain_link(vma, avc, anon_vma);
360 anon_vma_unlock(anon_vma);
364 out_error_free_anon_vma:
365 put_anon_vma(anon_vma);
367 unlink_anon_vmas(vma);
371 void unlink_anon_vmas(struct vm_area_struct *vma)
373 struct anon_vma_chain *avc, *next;
374 struct anon_vma *root = NULL;
377 * Unlink each anon_vma chained to the VMA. This list is ordered
378 * from newest to oldest, ensuring the root anon_vma gets freed last.
380 list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
381 struct anon_vma *anon_vma = avc->anon_vma;
383 root = lock_anon_vma_root(root, anon_vma);
384 list_del(&avc->same_anon_vma);
387 * Leave empty anon_vmas on the list - we'll need
388 * to free them outside the lock.
390 if (list_empty(&anon_vma->head))
393 list_del(&avc->same_vma);
394 anon_vma_chain_free(avc);
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 acquire the anon_vma->root->mutex.
403 list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
404 struct anon_vma *anon_vma = avc->anon_vma;
406 put_anon_vma(anon_vma);
408 list_del(&avc->same_vma);
409 anon_vma_chain_free(avc);
413 static void anon_vma_ctor(void *data)
415 struct anon_vma *anon_vma = data;
417 mutex_init(&anon_vma->mutex);
418 atomic_set(&anon_vma->refcount, 0);
419 INIT_LIST_HEAD(&anon_vma->head);
422 void __init anon_vma_init(void)
424 anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
425 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor);
426 anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain, SLAB_PANIC);
430 * Getting a lock on a stable anon_vma from a page off the LRU is tricky!
432 * Since there is no serialization what so ever against page_remove_rmap()
433 * the best this function can do is return a locked anon_vma that might
434 * have been relevant to this page.
436 * The page might have been remapped to a different anon_vma or the anon_vma
437 * returned may already be freed (and even reused).
439 * In case it was remapped to a different anon_vma, the new anon_vma will be a
440 * child of the old anon_vma, and the anon_vma lifetime rules will therefore
441 * ensure that any anon_vma obtained from the page will still be valid for as
442 * long as we observe page_mapped() [ hence all those page_mapped() tests ].
444 * All users of this function must be very careful when walking the anon_vma
445 * chain and verify that the page in question is indeed mapped in it
446 * [ something equivalent to page_mapped_in_vma() ].
448 * Since anon_vma's slab is DESTROY_BY_RCU and we know from page_remove_rmap()
449 * that the anon_vma pointer from page->mapping is valid if there is a
450 * mapcount, we can dereference the anon_vma after observing those.
452 struct anon_vma *page_get_anon_vma(struct page *page)
454 struct anon_vma *anon_vma = NULL;
455 unsigned long anon_mapping;
458 anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping);
459 if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
461 if (!page_mapped(page))
464 anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
465 if (!atomic_inc_not_zero(&anon_vma->refcount)) {
471 * If this page is still mapped, then its anon_vma cannot have been
472 * freed. But if it has been unmapped, we have no security against the
473 * anon_vma structure being freed and reused (for another anon_vma:
474 * SLAB_DESTROY_BY_RCU guarantees that - so the atomic_inc_not_zero()
475 * above cannot corrupt).
477 if (!page_mapped(page)) {
478 put_anon_vma(anon_vma);
488 * Similar to page_get_anon_vma() except it locks the anon_vma.
490 * Its a little more complex as it tries to keep the fast path to a single
491 * atomic op -- the trylock. If we fail the trylock, we fall back to getting a
492 * reference like with page_get_anon_vma() and then block on the mutex.
494 struct anon_vma *page_lock_anon_vma(struct page *page)
496 struct anon_vma *anon_vma = NULL;
497 struct anon_vma *root_anon_vma;
498 unsigned long anon_mapping;
501 anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping);
502 if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
504 if (!page_mapped(page))
507 anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
508 root_anon_vma = ACCESS_ONCE(anon_vma->root);
509 if (mutex_trylock(&root_anon_vma->mutex)) {
511 * If the page is still mapped, then this anon_vma is still
512 * its anon_vma, and holding the mutex ensures that it will
513 * not go away, see anon_vma_free().
515 if (!page_mapped(page)) {
516 mutex_unlock(&root_anon_vma->mutex);
522 /* trylock failed, we got to sleep */
523 if (!atomic_inc_not_zero(&anon_vma->refcount)) {
528 if (!page_mapped(page)) {
529 put_anon_vma(anon_vma);
534 /* we pinned the anon_vma, its safe to sleep */
536 anon_vma_lock(anon_vma);
538 if (atomic_dec_and_test(&anon_vma->refcount)) {
540 * Oops, we held the last refcount, release the lock
541 * and bail -- can't simply use put_anon_vma() because
542 * we'll deadlock on the anon_vma_lock() recursion.
544 anon_vma_unlock(anon_vma);
545 __put_anon_vma(anon_vma);
556 void page_unlock_anon_vma(struct anon_vma *anon_vma)
558 anon_vma_unlock(anon_vma);
562 * At what user virtual address is page expected in @vma?
563 * Returns virtual address or -EFAULT if page's index/offset is not
564 * within the range mapped the @vma.
567 vma_address(struct page *page, struct vm_area_struct *vma)
569 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
570 unsigned long address;
572 if (unlikely(is_vm_hugetlb_page(vma)))
573 pgoff = page->index << huge_page_order(page_hstate(page));
574 address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
575 if (unlikely(address < vma->vm_start || address >= vma->vm_end)) {
576 /* page should be within @vma mapping range */
583 * At what user virtual address is page expected in vma?
584 * Caller should check the page is actually part of the vma.
586 unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
588 if (PageAnon(page)) {
589 struct anon_vma *page__anon_vma = page_anon_vma(page);
591 * Note: swapoff's unuse_vma() is more efficient with this
592 * check, and needs it to match anon_vma when KSM is active.
594 if (!vma->anon_vma || !page__anon_vma ||
595 vma->anon_vma->root != page__anon_vma->root)
597 } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
599 vma->vm_file->f_mapping != page->mapping)
603 return vma_address(page, vma);
607 * Check that @page is mapped at @address into @mm.
609 * If @sync is false, page_check_address may perform a racy check to avoid
610 * the page table lock when the pte is not present (helpful when reclaiming
611 * highly shared pages).
613 * On success returns with pte mapped and locked.
615 pte_t *__page_check_address(struct page *page, struct mm_struct *mm,
616 unsigned long address, spinlock_t **ptlp, int sync)
624 if (unlikely(PageHuge(page))) {
625 pte = huge_pte_offset(mm, address);
626 ptl = &mm->page_table_lock;
630 pgd = pgd_offset(mm, address);
631 if (!pgd_present(*pgd))
634 pud = pud_offset(pgd, address);
635 if (!pud_present(*pud))
638 pmd = pmd_offset(pud, address);
639 if (!pmd_present(*pmd))
641 if (pmd_trans_huge(*pmd))
644 pte = pte_offset_map(pmd, address);
645 /* Make a quick check before getting the lock */
646 if (!sync && !pte_present(*pte)) {
651 ptl = pte_lockptr(mm, pmd);
654 if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) {
658 pte_unmap_unlock(pte, ptl);
663 * page_mapped_in_vma - check whether a page is really mapped in a VMA
664 * @page: the page to test
665 * @vma: the VMA to test
667 * Returns 1 if the page is mapped into the page tables of the VMA, 0
668 * if the page is not mapped into the page tables of this VMA. Only
669 * valid for normal file or anonymous VMAs.
671 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
673 unsigned long address;
677 address = vma_address(page, vma);
678 if (address == -EFAULT) /* out of vma range */
680 pte = page_check_address(page, vma->vm_mm, address, &ptl, 1);
681 if (!pte) /* the page is not in this mm */
683 pte_unmap_unlock(pte, ptl);
689 * Subfunctions of page_referenced: page_referenced_one called
690 * repeatedly from either page_referenced_anon or page_referenced_file.
692 int page_referenced_one(struct page *page, struct vm_area_struct *vma,
693 unsigned long address, unsigned int *mapcount,
694 unsigned long *vm_flags)
696 struct mm_struct *mm = vma->vm_mm;
699 if (unlikely(PageTransHuge(page))) {
702 spin_lock(&mm->page_table_lock);
704 * rmap might return false positives; we must filter
705 * these out using page_check_address_pmd().
707 pmd = page_check_address_pmd(page, mm, address,
708 PAGE_CHECK_ADDRESS_PMD_FLAG);
710 spin_unlock(&mm->page_table_lock);
714 if (vma->vm_flags & VM_LOCKED) {
715 spin_unlock(&mm->page_table_lock);
716 *mapcount = 0; /* break early from loop */
717 *vm_flags |= VM_LOCKED;
721 /* go ahead even if the pmd is pmd_trans_splitting() */
722 if (pmdp_clear_flush_young_notify(vma, address, pmd))
724 spin_unlock(&mm->page_table_lock);
730 * rmap might return false positives; we must filter
731 * these out using page_check_address().
733 pte = page_check_address(page, mm, address, &ptl, 0);
737 if (vma->vm_flags & VM_LOCKED) {
738 pte_unmap_unlock(pte, ptl);
739 *mapcount = 0; /* break early from loop */
740 *vm_flags |= VM_LOCKED;
744 if (ptep_clear_flush_young_notify(vma, address, pte)) {
746 * Don't treat a reference through a sequentially read
747 * mapping as such. If the page has been used in
748 * another mapping, we will catch it; if this other
749 * mapping is already gone, the unmap path will have
750 * set PG_referenced or activated the page.
752 if (likely(!VM_SequentialReadHint(vma)))
755 pte_unmap_unlock(pte, ptl);
758 /* Pretend the page is referenced if the task has the
759 swap token and is in the middle of a page fault. */
760 if (mm != current->mm && has_swap_token(mm) &&
761 rwsem_is_locked(&mm->mmap_sem))
767 *vm_flags |= vma->vm_flags;
772 static int page_referenced_anon(struct page *page,
773 struct mem_cgroup *memcg,
774 unsigned long *vm_flags)
776 unsigned int mapcount;
777 struct anon_vma *anon_vma;
778 struct anon_vma_chain *avc;
781 anon_vma = page_lock_anon_vma(page);
785 mapcount = page_mapcount(page);
786 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
787 struct vm_area_struct *vma = avc->vma;
788 unsigned long address = vma_address(page, vma);
789 if (address == -EFAULT)
792 * If we are reclaiming on behalf of a cgroup, skip
793 * counting on behalf of references from different
796 if (memcg && !mm_match_cgroup(vma->vm_mm, memcg))
798 referenced += page_referenced_one(page, vma, address,
799 &mapcount, vm_flags);
804 page_unlock_anon_vma(anon_vma);
809 * page_referenced_file - referenced check for object-based rmap
810 * @page: the page we're checking references on.
811 * @memcg: target memory control group
812 * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
814 * For an object-based mapped page, find all the places it is mapped and
815 * check/clear the referenced flag. This is done by following the page->mapping
816 * pointer, then walking the chain of vmas it holds. It returns the number
817 * of references it found.
819 * This function is only called from page_referenced for object-based pages.
821 static int page_referenced_file(struct page *page,
822 struct mem_cgroup *memcg,
823 unsigned long *vm_flags)
825 unsigned int mapcount;
826 struct address_space *mapping = page->mapping;
827 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
828 struct vm_area_struct *vma;
829 struct prio_tree_iter iter;
833 * The caller's checks on page->mapping and !PageAnon have made
834 * sure that this is a file page: the check for page->mapping
835 * excludes the case just before it gets set on an anon page.
837 BUG_ON(PageAnon(page));
840 * The page lock not only makes sure that page->mapping cannot
841 * suddenly be NULLified by truncation, it makes sure that the
842 * structure at mapping cannot be freed and reused yet,
843 * so we can safely take mapping->i_mmap_mutex.
845 BUG_ON(!PageLocked(page));
847 mutex_lock(&mapping->i_mmap_mutex);
850 * i_mmap_mutex does not stabilize mapcount at all, but mapcount
851 * is more likely to be accurate if we note it after spinning.
853 mapcount = page_mapcount(page);
855 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
856 unsigned long address = vma_address(page, vma);
857 if (address == -EFAULT)
860 * If we are reclaiming on behalf of a cgroup, skip
861 * counting on behalf of references from different
864 if (memcg && !mm_match_cgroup(vma->vm_mm, memcg))
866 referenced += page_referenced_one(page, vma, address,
867 &mapcount, vm_flags);
872 mutex_unlock(&mapping->i_mmap_mutex);
877 * page_referenced - test if the page was referenced
878 * @page: the page to test
879 * @is_locked: caller holds lock on the page
880 * @memcg: target memory cgroup
881 * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
883 * Quick test_and_clear_referenced for all mappings to a page,
884 * returns the number of ptes which referenced the page.
886 int page_referenced(struct page *page,
888 struct mem_cgroup *memcg,
889 unsigned long *vm_flags)
895 if (page_mapped(page) && page_rmapping(page)) {
896 if (!is_locked && (!PageAnon(page) || PageKsm(page))) {
897 we_locked = trylock_page(page);
903 if (unlikely(PageKsm(page)))
904 referenced += page_referenced_ksm(page, memcg,
906 else if (PageAnon(page))
907 referenced += page_referenced_anon(page, memcg,
909 else if (page->mapping)
910 referenced += page_referenced_file(page, memcg,
915 if (page_test_and_clear_young(page_to_pfn(page)))
922 static int page_mkclean_one(struct page *page, struct vm_area_struct *vma,
923 unsigned long address)
925 struct mm_struct *mm = vma->vm_mm;
930 pte = page_check_address(page, mm, address, &ptl, 1);
934 if (pte_dirty(*pte) || pte_write(*pte)) {
937 flush_cache_page(vma, address, pte_pfn(*pte));
938 entry = ptep_clear_flush_notify(vma, address, pte);
939 entry = pte_wrprotect(entry);
940 entry = pte_mkclean(entry);
941 set_pte_at(mm, address, pte, entry);
945 pte_unmap_unlock(pte, ptl);
950 static int page_mkclean_file(struct address_space *mapping, struct page *page)
952 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
953 struct vm_area_struct *vma;
954 struct prio_tree_iter iter;
957 BUG_ON(PageAnon(page));
959 mutex_lock(&mapping->i_mmap_mutex);
960 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
961 if (vma->vm_flags & VM_SHARED) {
962 unsigned long address = vma_address(page, vma);
963 if (address == -EFAULT)
965 ret += page_mkclean_one(page, vma, address);
968 mutex_unlock(&mapping->i_mmap_mutex);
972 int page_mkclean(struct page *page)
976 BUG_ON(!PageLocked(page));
978 if (page_mapped(page)) {
979 struct address_space *mapping = page_mapping(page);
981 ret = page_mkclean_file(mapping, page);
982 if (page_test_and_clear_dirty(page_to_pfn(page), 1))
989 EXPORT_SYMBOL_GPL(page_mkclean);
992 * page_move_anon_rmap - move a page to our anon_vma
993 * @page: the page to move to our anon_vma
994 * @vma: the vma the page belongs to
995 * @address: the user virtual address mapped
997 * When a page belongs exclusively to one process after a COW event,
998 * that page can be moved into the anon_vma that belongs to just that
999 * process, so the rmap code will not search the parent or sibling
1002 void page_move_anon_rmap(struct page *page,
1003 struct vm_area_struct *vma, unsigned long address)
1005 struct anon_vma *anon_vma = vma->anon_vma;
1007 VM_BUG_ON(!PageLocked(page));
1008 VM_BUG_ON(!anon_vma);
1009 VM_BUG_ON(page->index != linear_page_index(vma, address));
1011 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1012 page->mapping = (struct address_space *) anon_vma;
1016 * __page_set_anon_rmap - set up new anonymous rmap
1017 * @page: Page to add to rmap
1018 * @vma: VM area to add page to.
1019 * @address: User virtual address of the mapping
1020 * @exclusive: the page is exclusively owned by the current process
1022 static void __page_set_anon_rmap(struct page *page,
1023 struct vm_area_struct *vma, unsigned long address, int exclusive)
1025 struct anon_vma *anon_vma = vma->anon_vma;
1033 * If the page isn't exclusively mapped into this vma,
1034 * we must use the _oldest_ possible anon_vma for the
1038 anon_vma = anon_vma->root;
1040 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1041 page->mapping = (struct address_space *) anon_vma;
1042 page->index = linear_page_index(vma, address);
1046 * __page_check_anon_rmap - sanity check anonymous rmap addition
1047 * @page: the page to add the mapping to
1048 * @vma: the vm area in which the mapping is added
1049 * @address: the user virtual address mapped
1051 static void __page_check_anon_rmap(struct page *page,
1052 struct vm_area_struct *vma, unsigned long address)
1054 #ifdef CONFIG_DEBUG_VM
1056 * The page's anon-rmap details (mapping and index) are guaranteed to
1057 * be set up correctly at this point.
1059 * We have exclusion against page_add_anon_rmap because the caller
1060 * always holds the page locked, except if called from page_dup_rmap,
1061 * in which case the page is already known to be setup.
1063 * We have exclusion against page_add_new_anon_rmap because those pages
1064 * are initially only visible via the pagetables, and the pte is locked
1065 * over the call to page_add_new_anon_rmap.
1067 BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root);
1068 BUG_ON(page->index != linear_page_index(vma, address));
1073 * page_add_anon_rmap - add pte mapping to an anonymous page
1074 * @page: the page to add the mapping to
1075 * @vma: the vm area in which the mapping is added
1076 * @address: the user virtual address mapped
1078 * The caller needs to hold the pte lock, and the page must be locked in
1079 * the anon_vma case: to serialize mapping,index checking after setting,
1080 * and to ensure that PageAnon is not being upgraded racily to PageKsm
1081 * (but PageKsm is never downgraded to PageAnon).
1083 void page_add_anon_rmap(struct page *page,
1084 struct vm_area_struct *vma, unsigned long address)
1086 do_page_add_anon_rmap(page, vma, address, 0);
1090 * Special version of the above for do_swap_page, which often runs
1091 * into pages that are exclusively owned by the current process.
1092 * Everybody else should continue to use page_add_anon_rmap above.
1094 void do_page_add_anon_rmap(struct page *page,
1095 struct vm_area_struct *vma, unsigned long address, int exclusive)
1097 int first = atomic_inc_and_test(&page->_mapcount);
1099 if (!PageTransHuge(page))
1100 __inc_zone_page_state(page, NR_ANON_PAGES);
1102 __inc_zone_page_state(page,
1103 NR_ANON_TRANSPARENT_HUGEPAGES);
1105 if (unlikely(PageKsm(page)))
1108 VM_BUG_ON(!PageLocked(page));
1109 /* address might be in next vma when migration races vma_adjust */
1111 __page_set_anon_rmap(page, vma, address, exclusive);
1113 __page_check_anon_rmap(page, vma, address);
1117 * page_add_new_anon_rmap - add pte mapping to a new anonymous page
1118 * @page: the page to add the mapping to
1119 * @vma: the vm area in which the mapping is added
1120 * @address: the user virtual address mapped
1122 * Same as page_add_anon_rmap but must only be called on *new* pages.
1123 * This means the inc-and-test can be bypassed.
1124 * Page does not have to be locked.
1126 void page_add_new_anon_rmap(struct page *page,
1127 struct vm_area_struct *vma, unsigned long address)
1129 VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
1130 SetPageSwapBacked(page);
1131 atomic_set(&page->_mapcount, 0); /* increment count (starts at -1) */
1132 if (!PageTransHuge(page))
1133 __inc_zone_page_state(page, NR_ANON_PAGES);
1135 __inc_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
1136 __page_set_anon_rmap(page, vma, address, 1);
1137 if (page_evictable(page, vma))
1138 lru_cache_add_lru(page, LRU_ACTIVE_ANON);
1140 add_page_to_unevictable_list(page);
1144 * page_add_file_rmap - add pte mapping to a file page
1145 * @page: the page to add the mapping to
1147 * The caller needs to hold the pte lock.
1149 void page_add_file_rmap(struct page *page)
1152 unsigned long flags;
1154 mem_cgroup_begin_update_page_stat(page, &locked, &flags);
1155 if (atomic_inc_and_test(&page->_mapcount)) {
1156 __inc_zone_page_state(page, NR_FILE_MAPPED);
1157 mem_cgroup_inc_page_stat(page, MEMCG_NR_FILE_MAPPED);
1159 mem_cgroup_end_update_page_stat(page, &locked, &flags);
1163 * page_remove_rmap - take down pte mapping from a page
1164 * @page: page to remove mapping from
1166 * The caller needs to hold the pte lock.
1168 void page_remove_rmap(struct page *page)
1170 bool anon = PageAnon(page);
1172 unsigned long flags;
1175 * The anon case has no mem_cgroup page_stat to update; but may
1176 * uncharge_page() below, where the lock ordering can deadlock if
1177 * we hold the lock against page_stat move: so avoid it on anon.
1180 mem_cgroup_begin_update_page_stat(page, &locked, &flags);
1182 /* page still mapped by someone else? */
1183 if (!atomic_add_negative(-1, &page->_mapcount))
1187 * Now that the last pte has gone, s390 must transfer dirty
1188 * flag from storage key to struct page. We can usually skip
1189 * this if the page is anon, so about to be freed; but perhaps
1190 * not if it's in swapcache - there might be another pte slot
1191 * containing the swap entry, but page not yet written to swap.
1193 if ((!anon || PageSwapCache(page)) &&
1194 page_test_and_clear_dirty(page_to_pfn(page), 1))
1195 set_page_dirty(page);
1197 * Hugepages are not counted in NR_ANON_PAGES nor NR_FILE_MAPPED
1198 * and not charged by memcg for now.
1200 if (unlikely(PageHuge(page)))
1203 mem_cgroup_uncharge_page(page);
1204 if (!PageTransHuge(page))
1205 __dec_zone_page_state(page, NR_ANON_PAGES);
1207 __dec_zone_page_state(page,
1208 NR_ANON_TRANSPARENT_HUGEPAGES);
1210 __dec_zone_page_state(page, NR_FILE_MAPPED);
1211 mem_cgroup_dec_page_stat(page, MEMCG_NR_FILE_MAPPED);
1214 * It would be tidy to reset the PageAnon mapping here,
1215 * but that might overwrite a racing page_add_anon_rmap
1216 * which increments mapcount after us but sets mapping
1217 * before us: so leave the reset to free_hot_cold_page,
1218 * and remember that it's only reliable while mapped.
1219 * Leaving it set also helps swapoff to reinstate ptes
1220 * faster for those pages still in swapcache.
1224 mem_cgroup_end_update_page_stat(page, &locked, &flags);
1228 * Subfunctions of try_to_unmap: try_to_unmap_one called
1229 * repeatedly from try_to_unmap_ksm, try_to_unmap_anon or try_to_unmap_file.
1231 int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
1232 unsigned long address, enum ttu_flags flags)
1234 struct mm_struct *mm = vma->vm_mm;
1238 int ret = SWAP_AGAIN;
1240 pte = page_check_address(page, mm, address, &ptl, 0);
1245 * If the page is mlock()d, we cannot swap it out.
1246 * If it's recently referenced (perhaps page_referenced
1247 * skipped over this mm) then we should reactivate it.
1249 if (!(flags & TTU_IGNORE_MLOCK)) {
1250 if (vma->vm_flags & VM_LOCKED)
1253 if (TTU_ACTION(flags) == TTU_MUNLOCK)
1256 if (!(flags & TTU_IGNORE_ACCESS)) {
1257 if (ptep_clear_flush_young_notify(vma, address, pte)) {
1263 /* Nuke the page table entry. */
1264 flush_cache_page(vma, address, page_to_pfn(page));
1265 pteval = ptep_clear_flush_notify(vma, address, pte);
1267 /* Move the dirty bit to the physical page now the pte is gone. */
1268 if (pte_dirty(pteval))
1269 set_page_dirty(page);
1271 /* Update high watermark before we lower rss */
1272 update_hiwater_rss(mm);
1274 if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
1276 dec_mm_counter(mm, MM_ANONPAGES);
1278 dec_mm_counter(mm, MM_FILEPAGES);
1279 set_pte_at(mm, address, pte,
1280 swp_entry_to_pte(make_hwpoison_entry(page)));
1281 } else if (PageAnon(page)) {
1282 swp_entry_t entry = { .val = page_private(page) };
1284 if (PageSwapCache(page)) {
1286 * Store the swap location in the pte.
1287 * See handle_pte_fault() ...
1289 if (swap_duplicate(entry) < 0) {
1290 set_pte_at(mm, address, pte, pteval);
1294 if (list_empty(&mm->mmlist)) {
1295 spin_lock(&mmlist_lock);
1296 if (list_empty(&mm->mmlist))
1297 list_add(&mm->mmlist, &init_mm.mmlist);
1298 spin_unlock(&mmlist_lock);
1300 dec_mm_counter(mm, MM_ANONPAGES);
1301 inc_mm_counter(mm, MM_SWAPENTS);
1302 } else if (IS_ENABLED(CONFIG_MIGRATION)) {
1304 * Store the pfn of the page in a special migration
1305 * pte. do_swap_page() will wait until the migration
1306 * pte is removed and then restart fault handling.
1308 BUG_ON(TTU_ACTION(flags) != TTU_MIGRATION);
1309 entry = make_migration_entry(page, pte_write(pteval));
1311 set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
1312 BUG_ON(pte_file(*pte));
1313 } else if (IS_ENABLED(CONFIG_MIGRATION) &&
1314 (TTU_ACTION(flags) == TTU_MIGRATION)) {
1315 /* Establish migration entry for a file page */
1317 entry = make_migration_entry(page, pte_write(pteval));
1318 set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
1320 dec_mm_counter(mm, MM_FILEPAGES);
1322 page_remove_rmap(page);
1323 page_cache_release(page);
1326 pte_unmap_unlock(pte, ptl);
1331 pte_unmap_unlock(pte, ptl);
1335 * We need mmap_sem locking, Otherwise VM_LOCKED check makes
1336 * unstable result and race. Plus, We can't wait here because
1337 * we now hold anon_vma->mutex or mapping->i_mmap_mutex.
1338 * if trylock failed, the page remain in evictable lru and later
1339 * vmscan could retry to move the page to unevictable lru if the
1340 * page is actually mlocked.
1342 if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
1343 if (vma->vm_flags & VM_LOCKED) {
1344 mlock_vma_page(page);
1347 up_read(&vma->vm_mm->mmap_sem);
1353 * objrmap doesn't work for nonlinear VMAs because the assumption that
1354 * offset-into-file correlates with offset-into-virtual-addresses does not hold.
1355 * Consequently, given a particular page and its ->index, we cannot locate the
1356 * ptes which are mapping that page without an exhaustive linear search.
1358 * So what this code does is a mini "virtual scan" of each nonlinear VMA which
1359 * maps the file to which the target page belongs. The ->vm_private_data field
1360 * holds the current cursor into that scan. Successive searches will circulate
1361 * around the vma's virtual address space.
1363 * So as more replacement pressure is applied to the pages in a nonlinear VMA,
1364 * more scanning pressure is placed against them as well. Eventually pages
1365 * will become fully unmapped and are eligible for eviction.
1367 * For very sparsely populated VMAs this is a little inefficient - chances are
1368 * there there won't be many ptes located within the scan cluster. In this case
1369 * maybe we could scan further - to the end of the pte page, perhaps.
1371 * Mlocked pages: check VM_LOCKED under mmap_sem held for read, if we can
1372 * acquire it without blocking. If vma locked, mlock the pages in the cluster,
1373 * rather than unmapping them. If we encounter the "check_page" that vmscan is
1374 * trying to unmap, return SWAP_MLOCK, else default SWAP_AGAIN.
1376 #define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE)
1377 #define CLUSTER_MASK (~(CLUSTER_SIZE - 1))
1379 static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount,
1380 struct vm_area_struct *vma, struct page *check_page)
1382 struct mm_struct *mm = vma->vm_mm;
1390 unsigned long address;
1392 int ret = SWAP_AGAIN;
1395 address = (vma->vm_start + cursor) & CLUSTER_MASK;
1396 end = address + CLUSTER_SIZE;
1397 if (address < vma->vm_start)
1398 address = vma->vm_start;
1399 if (end > vma->vm_end)
1402 pgd = pgd_offset(mm, address);
1403 if (!pgd_present(*pgd))
1406 pud = pud_offset(pgd, address);
1407 if (!pud_present(*pud))
1410 pmd = pmd_offset(pud, address);
1411 if (!pmd_present(*pmd))
1415 * If we can acquire the mmap_sem for read, and vma is VM_LOCKED,
1416 * keep the sem while scanning the cluster for mlocking pages.
1418 if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
1419 locked_vma = (vma->vm_flags & VM_LOCKED);
1421 up_read(&vma->vm_mm->mmap_sem); /* don't need it */
1424 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1426 /* Update high watermark before we lower rss */
1427 update_hiwater_rss(mm);
1429 for (; address < end; pte++, address += PAGE_SIZE) {
1430 if (!pte_present(*pte))
1432 page = vm_normal_page(vma, address, *pte);
1433 BUG_ON(!page || PageAnon(page));
1436 mlock_vma_page(page); /* no-op if already mlocked */
1437 if (page == check_page)
1439 continue; /* don't unmap */
1442 if (ptep_clear_flush_young_notify(vma, address, pte))
1445 /* Nuke the page table entry. */
1446 flush_cache_page(vma, address, pte_pfn(*pte));
1447 pteval = ptep_clear_flush_notify(vma, address, pte);
1449 /* If nonlinear, store the file page offset in the pte. */
1450 if (page->index != linear_page_index(vma, address))
1451 set_pte_at(mm, address, pte, pgoff_to_pte(page->index));
1453 /* Move the dirty bit to the physical page now the pte is gone. */
1454 if (pte_dirty(pteval))
1455 set_page_dirty(page);
1457 page_remove_rmap(page);
1458 page_cache_release(page);
1459 dec_mm_counter(mm, MM_FILEPAGES);
1462 pte_unmap_unlock(pte - 1, ptl);
1464 up_read(&vma->vm_mm->mmap_sem);
1468 bool is_vma_temporary_stack(struct vm_area_struct *vma)
1470 int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP);
1475 if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) ==
1476 VM_STACK_INCOMPLETE_SETUP)
1483 * try_to_unmap_anon - unmap or unlock anonymous page using the object-based
1485 * @page: the page to unmap/unlock
1486 * @flags: action and flags
1488 * Find all the mappings of a page using the mapping pointer and the vma chains
1489 * contained in the anon_vma struct it points to.
1491 * This function is only called from try_to_unmap/try_to_munlock for
1493 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1494 * where the page was found will be held for write. So, we won't recheck
1495 * vm_flags for that VMA. That should be OK, because that vma shouldn't be
1498 static int try_to_unmap_anon(struct page *page, enum ttu_flags flags)
1500 struct anon_vma *anon_vma;
1501 struct anon_vma_chain *avc;
1502 int ret = SWAP_AGAIN;
1504 anon_vma = page_lock_anon_vma(page);
1508 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1509 struct vm_area_struct *vma = avc->vma;
1510 unsigned long address;
1513 * During exec, a temporary VMA is setup and later moved.
1514 * The VMA is moved under the anon_vma lock but not the
1515 * page tables leading to a race where migration cannot
1516 * find the migration ptes. Rather than increasing the
1517 * locking requirements of exec(), migration skips
1518 * temporary VMAs until after exec() completes.
1520 if (IS_ENABLED(CONFIG_MIGRATION) && (flags & TTU_MIGRATION) &&
1521 is_vma_temporary_stack(vma))
1524 address = vma_address(page, vma);
1525 if (address == -EFAULT)
1527 ret = try_to_unmap_one(page, vma, address, flags);
1528 if (ret != SWAP_AGAIN || !page_mapped(page))
1532 page_unlock_anon_vma(anon_vma);
1537 * try_to_unmap_file - unmap/unlock file page using the object-based rmap method
1538 * @page: the page to unmap/unlock
1539 * @flags: action and flags
1541 * Find all the mappings of a page using the mapping pointer and the vma chains
1542 * contained in the address_space struct it points to.
1544 * This function is only called from try_to_unmap/try_to_munlock for
1545 * object-based pages.
1546 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1547 * where the page was found will be held for write. So, we won't recheck
1548 * vm_flags for that VMA. That should be OK, because that vma shouldn't be
1551 static int try_to_unmap_file(struct page *page, enum ttu_flags flags)
1553 struct address_space *mapping = page->mapping;
1554 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1555 struct vm_area_struct *vma;
1556 struct prio_tree_iter iter;
1557 int ret = SWAP_AGAIN;
1558 unsigned long cursor;
1559 unsigned long max_nl_cursor = 0;
1560 unsigned long max_nl_size = 0;
1561 unsigned int mapcount;
1563 mutex_lock(&mapping->i_mmap_mutex);
1564 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
1565 unsigned long address = vma_address(page, vma);
1566 if (address == -EFAULT)
1568 ret = try_to_unmap_one(page, vma, address, flags);
1569 if (ret != SWAP_AGAIN || !page_mapped(page))
1573 if (list_empty(&mapping->i_mmap_nonlinear))
1577 * We don't bother to try to find the munlocked page in nonlinears.
1578 * It's costly. Instead, later, page reclaim logic may call
1579 * try_to_unmap(TTU_MUNLOCK) and recover PG_mlocked lazily.
1581 if (TTU_ACTION(flags) == TTU_MUNLOCK)
1584 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
1585 shared.vm_set.list) {
1586 cursor = (unsigned long) vma->vm_private_data;
1587 if (cursor > max_nl_cursor)
1588 max_nl_cursor = cursor;
1589 cursor = vma->vm_end - vma->vm_start;
1590 if (cursor > max_nl_size)
1591 max_nl_size = cursor;
1594 if (max_nl_size == 0) { /* all nonlinears locked or reserved ? */
1600 * We don't try to search for this page in the nonlinear vmas,
1601 * and page_referenced wouldn't have found it anyway. Instead
1602 * just walk the nonlinear vmas trying to age and unmap some.
1603 * The mapcount of the page we came in with is irrelevant,
1604 * but even so use it as a guide to how hard we should try?
1606 mapcount = page_mapcount(page);
1611 max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK;
1612 if (max_nl_cursor == 0)
1613 max_nl_cursor = CLUSTER_SIZE;
1616 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
1617 shared.vm_set.list) {
1618 cursor = (unsigned long) vma->vm_private_data;
1619 while ( cursor < max_nl_cursor &&
1620 cursor < vma->vm_end - vma->vm_start) {
1621 if (try_to_unmap_cluster(cursor, &mapcount,
1622 vma, page) == SWAP_MLOCK)
1624 cursor += CLUSTER_SIZE;
1625 vma->vm_private_data = (void *) cursor;
1626 if ((int)mapcount <= 0)
1629 vma->vm_private_data = (void *) max_nl_cursor;
1632 max_nl_cursor += CLUSTER_SIZE;
1633 } while (max_nl_cursor <= max_nl_size);
1636 * Don't loop forever (perhaps all the remaining pages are
1637 * in locked vmas). Reset cursor on all unreserved nonlinear
1638 * vmas, now forgetting on which ones it had fallen behind.
1640 list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list)
1641 vma->vm_private_data = NULL;
1643 mutex_unlock(&mapping->i_mmap_mutex);
1648 * try_to_unmap - try to remove all page table mappings to a page
1649 * @page: the page to get unmapped
1650 * @flags: action and flags
1652 * Tries to remove all the page table entries which are mapping this
1653 * page, used in the pageout path. Caller must hold the page lock.
1654 * Return values are:
1656 * SWAP_SUCCESS - we succeeded in removing all mappings
1657 * SWAP_AGAIN - we missed a mapping, try again later
1658 * SWAP_FAIL - the page is unswappable
1659 * SWAP_MLOCK - page is mlocked.
1661 int try_to_unmap(struct page *page, enum ttu_flags flags)
1665 BUG_ON(!PageLocked(page));
1666 VM_BUG_ON(!PageHuge(page) && PageTransHuge(page));
1668 if (unlikely(PageKsm(page)))
1669 ret = try_to_unmap_ksm(page, flags);
1670 else if (PageAnon(page))
1671 ret = try_to_unmap_anon(page, flags);
1673 ret = try_to_unmap_file(page, flags);
1674 if (ret != SWAP_MLOCK && !page_mapped(page))
1680 * try_to_munlock - try to munlock a page
1681 * @page: the page to be munlocked
1683 * Called from munlock code. Checks all of the VMAs mapping the page
1684 * to make sure nobody else has this page mlocked. The page will be
1685 * returned with PG_mlocked cleared if no other vmas have it mlocked.
1687 * Return values are:
1689 * SWAP_AGAIN - no vma is holding page mlocked, or,
1690 * SWAP_AGAIN - page mapped in mlocked vma -- couldn't acquire mmap sem
1691 * SWAP_FAIL - page cannot be located at present
1692 * SWAP_MLOCK - page is now mlocked.
1694 int try_to_munlock(struct page *page)
1696 VM_BUG_ON(!PageLocked(page) || PageLRU(page));
1698 if (unlikely(PageKsm(page)))
1699 return try_to_unmap_ksm(page, TTU_MUNLOCK);
1700 else if (PageAnon(page))
1701 return try_to_unmap_anon(page, TTU_MUNLOCK);
1703 return try_to_unmap_file(page, TTU_MUNLOCK);
1706 void __put_anon_vma(struct anon_vma *anon_vma)
1708 struct anon_vma *root = anon_vma->root;
1710 if (root != anon_vma && atomic_dec_and_test(&root->refcount))
1711 anon_vma_free(root);
1713 anon_vma_free(anon_vma);
1716 #ifdef CONFIG_MIGRATION
1718 * rmap_walk() and its helpers rmap_walk_anon() and rmap_walk_file():
1719 * Called by migrate.c to remove migration ptes, but might be used more later.
1721 static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *,
1722 struct vm_area_struct *, unsigned long, void *), void *arg)
1724 struct anon_vma *anon_vma;
1725 struct anon_vma_chain *avc;
1726 int ret = SWAP_AGAIN;
1729 * Note: remove_migration_ptes() cannot use page_lock_anon_vma()
1730 * because that depends on page_mapped(); but not all its usages
1731 * are holding mmap_sem. Users without mmap_sem are required to
1732 * take a reference count to prevent the anon_vma disappearing
1734 anon_vma = page_anon_vma(page);
1737 anon_vma_lock(anon_vma);
1738 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1739 struct vm_area_struct *vma = avc->vma;
1740 unsigned long address = vma_address(page, vma);
1741 if (address == -EFAULT)
1743 ret = rmap_one(page, vma, address, arg);
1744 if (ret != SWAP_AGAIN)
1747 anon_vma_unlock(anon_vma);
1751 static int rmap_walk_file(struct page *page, int (*rmap_one)(struct page *,
1752 struct vm_area_struct *, unsigned long, void *), void *arg)
1754 struct address_space *mapping = page->mapping;
1755 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1756 struct vm_area_struct *vma;
1757 struct prio_tree_iter iter;
1758 int ret = SWAP_AGAIN;
1762 mutex_lock(&mapping->i_mmap_mutex);
1763 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
1764 unsigned long address = vma_address(page, vma);
1765 if (address == -EFAULT)
1767 ret = rmap_one(page, vma, address, arg);
1768 if (ret != SWAP_AGAIN)
1772 * No nonlinear handling: being always shared, nonlinear vmas
1773 * never contain migration ptes. Decide what to do about this
1774 * limitation to linear when we need rmap_walk() on nonlinear.
1776 mutex_unlock(&mapping->i_mmap_mutex);
1780 int rmap_walk(struct page *page, int (*rmap_one)(struct page *,
1781 struct vm_area_struct *, unsigned long, void *), void *arg)
1783 VM_BUG_ON(!PageLocked(page));
1785 if (unlikely(PageKsm(page)))
1786 return rmap_walk_ksm(page, rmap_one, arg);
1787 else if (PageAnon(page))
1788 return rmap_walk_anon(page, rmap_one, arg);
1790 return rmap_walk_file(page, rmap_one, arg);
1792 #endif /* CONFIG_MIGRATION */
1794 #ifdef CONFIG_HUGETLB_PAGE
1796 * The following three functions are for anonymous (private mapped) hugepages.
1797 * Unlike common anonymous pages, anonymous hugepages have no accounting code
1798 * and no lru code, because we handle hugepages differently from common pages.
1800 static void __hugepage_set_anon_rmap(struct page *page,
1801 struct vm_area_struct *vma, unsigned long address, int exclusive)
1803 struct anon_vma *anon_vma = vma->anon_vma;
1810 anon_vma = anon_vma->root;
1812 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1813 page->mapping = (struct address_space *) anon_vma;
1814 page->index = linear_page_index(vma, address);
1817 void hugepage_add_anon_rmap(struct page *page,
1818 struct vm_area_struct *vma, unsigned long address)
1820 struct anon_vma *anon_vma = vma->anon_vma;
1823 BUG_ON(!PageLocked(page));
1825 /* address might be in next vma when migration races vma_adjust */
1826 first = atomic_inc_and_test(&page->_mapcount);
1828 __hugepage_set_anon_rmap(page, vma, address, 0);
1831 void hugepage_add_new_anon_rmap(struct page *page,
1832 struct vm_area_struct *vma, unsigned long address)
1834 BUG_ON(address < vma->vm_start || address >= vma->vm_end);
1835 atomic_set(&page->_mapcount, 0);
1836 __hugepage_set_anon_rmap(page, vma, address, 1);
1838 #endif /* CONFIG_HUGETLB_PAGE */