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 <hugh@veritas.com> 2003, 2004
21 * Lock ordering in mm:
23 * inode->i_mutex (while writing or truncating, not reading or faulting)
26 * When a page fault occurs in writing from user to file, down_read
27 * of mmap_sem nests within i_mutex; in sys_msync, i_mutex nests within
28 * down_read of mmap_sem; i_mutex and down_write of mmap_sem are never
29 * taken together; in truncation, i_mutex is taken outermost.
32 * page->flags PG_locked (lock_page)
33 * mapping->i_mmap_lock
35 * mm->page_table_lock or pte_lock
36 * zone->lru_lock (in mark_page_accessed, isolate_lru_page)
37 * swap_lock (in swap_duplicate, swap_info_get)
38 * mmlist_lock (in mmput, drain_mmlist and others)
39 * mapping->private_lock (in __set_page_dirty_buffers)
40 * inode_lock (in set_page_dirty's __mark_inode_dirty)
41 * sb_lock (within inode_lock in fs/fs-writeback.c)
42 * mapping->tree_lock (widely used, in set_page_dirty,
43 * in arch-dependent flush_dcache_mmap_lock,
44 * within inode_lock in __sync_single_inode)
48 #include <linux/pagemap.h>
49 #include <linux/swap.h>
50 #include <linux/swapops.h>
51 #include <linux/slab.h>
52 #include <linux/init.h>
53 #include <linux/rmap.h>
54 #include <linux/rcupdate.h>
55 #include <linux/module.h>
57 #include <asm/tlbflush.h>
59 //#define RMAP_DEBUG /* can be enabled only for debugging */
61 kmem_cache_t *anon_vma_cachep;
63 static inline void validate_anon_vma(struct vm_area_struct *find_vma)
66 struct anon_vma *anon_vma = find_vma->anon_vma;
67 struct vm_area_struct *vma;
68 unsigned int mapcount = 0;
71 list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
73 BUG_ON(mapcount > 100000);
81 /* This must be called under the mmap_sem. */
82 int anon_vma_prepare(struct vm_area_struct *vma)
84 struct anon_vma *anon_vma = vma->anon_vma;
87 if (unlikely(!anon_vma)) {
88 struct mm_struct *mm = vma->vm_mm;
89 struct anon_vma *allocated, *locked;
91 anon_vma = find_mergeable_anon_vma(vma);
95 spin_lock(&locked->lock);
97 anon_vma = anon_vma_alloc();
98 if (unlikely(!anon_vma))
100 allocated = anon_vma;
104 /* page_table_lock to protect against threads */
105 spin_lock(&mm->page_table_lock);
106 if (likely(!vma->anon_vma)) {
107 vma->anon_vma = anon_vma;
108 list_add(&vma->anon_vma_node, &anon_vma->head);
111 spin_unlock(&mm->page_table_lock);
114 spin_unlock(&locked->lock);
115 if (unlikely(allocated))
116 anon_vma_free(allocated);
121 void __anon_vma_merge(struct vm_area_struct *vma, struct vm_area_struct *next)
123 BUG_ON(vma->anon_vma != next->anon_vma);
124 list_del(&next->anon_vma_node);
127 void __anon_vma_link(struct vm_area_struct *vma)
129 struct anon_vma *anon_vma = vma->anon_vma;
132 list_add(&vma->anon_vma_node, &anon_vma->head);
133 validate_anon_vma(vma);
137 void anon_vma_link(struct vm_area_struct *vma)
139 struct anon_vma *anon_vma = vma->anon_vma;
142 spin_lock(&anon_vma->lock);
143 list_add(&vma->anon_vma_node, &anon_vma->head);
144 validate_anon_vma(vma);
145 spin_unlock(&anon_vma->lock);
149 void anon_vma_unlink(struct vm_area_struct *vma)
151 struct anon_vma *anon_vma = vma->anon_vma;
157 spin_lock(&anon_vma->lock);
158 validate_anon_vma(vma);
159 list_del(&vma->anon_vma_node);
161 /* We must garbage collect the anon_vma if it's empty */
162 empty = list_empty(&anon_vma->head);
163 spin_unlock(&anon_vma->lock);
166 anon_vma_free(anon_vma);
169 static void anon_vma_ctor(void *data, kmem_cache_t *cachep, unsigned long flags)
171 if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
172 SLAB_CTOR_CONSTRUCTOR) {
173 struct anon_vma *anon_vma = data;
175 spin_lock_init(&anon_vma->lock);
176 INIT_LIST_HEAD(&anon_vma->head);
180 void __init anon_vma_init(void)
182 anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
183 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor, NULL);
187 * Getting a lock on a stable anon_vma from a page off the LRU is
188 * tricky: page_lock_anon_vma rely on RCU to guard against the races.
190 static struct anon_vma *page_lock_anon_vma(struct page *page)
192 struct anon_vma *anon_vma = NULL;
193 unsigned long anon_mapping;
196 anon_mapping = (unsigned long) page->mapping;
197 if (!(anon_mapping & PAGE_MAPPING_ANON))
199 if (!page_mapped(page))
202 anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
203 spin_lock(&anon_vma->lock);
209 #ifdef CONFIG_MIGRATION
211 * Remove an anonymous page from swap replacing the swap pte's
212 * through real pte's pointing to valid pages and then releasing
213 * the page from the swap cache.
215 * Must hold page lock on page.
217 void remove_from_swap(struct page *page)
219 struct anon_vma *anon_vma;
220 struct vm_area_struct *vma;
222 if (!PageAnon(page) || !PageSwapCache(page))
225 anon_vma = page_lock_anon_vma(page);
229 list_for_each_entry(vma, &anon_vma->head, anon_vma_node)
230 remove_vma_swap(vma, page);
232 spin_unlock(&anon_vma->lock);
234 delete_from_swap_cache(page);
239 * At what user virtual address is page expected in vma?
241 static inline unsigned long
242 vma_address(struct page *page, struct vm_area_struct *vma)
244 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
245 unsigned long address;
247 address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
248 if (unlikely(address < vma->vm_start || address >= vma->vm_end)) {
249 /* page should be within any vma from prio_tree_next */
250 BUG_ON(!PageAnon(page));
257 * At what user virtual address is page expected in vma? checking that the
258 * page matches the vma: currently only used on anon pages, by unuse_vma;
260 unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
262 if (PageAnon(page)) {
263 if ((void *)vma->anon_vma !=
264 (void *)page->mapping - PAGE_MAPPING_ANON)
266 } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
268 vma->vm_file->f_mapping != page->mapping)
272 return vma_address(page, vma);
276 * Check that @page is mapped at @address into @mm.
278 * On success returns with pte mapped and locked.
280 pte_t *page_check_address(struct page *page, struct mm_struct *mm,
281 unsigned long address, spinlock_t **ptlp)
289 pgd = pgd_offset(mm, address);
290 if (!pgd_present(*pgd))
293 pud = pud_offset(pgd, address);
294 if (!pud_present(*pud))
297 pmd = pmd_offset(pud, address);
298 if (!pmd_present(*pmd))
301 pte = pte_offset_map(pmd, address);
302 /* Make a quick check before getting the lock */
303 if (!pte_present(*pte)) {
308 ptl = pte_lockptr(mm, pmd);
310 if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) {
314 pte_unmap_unlock(pte, ptl);
319 * Subfunctions of page_referenced: page_referenced_one called
320 * repeatedly from either page_referenced_anon or page_referenced_file.
322 static int page_referenced_one(struct page *page,
323 struct vm_area_struct *vma, unsigned int *mapcount)
325 struct mm_struct *mm = vma->vm_mm;
326 unsigned long address;
331 address = vma_address(page, vma);
332 if (address == -EFAULT)
335 pte = page_check_address(page, mm, address, &ptl);
339 if (ptep_clear_flush_young(vma, address, pte))
342 /* Pretend the page is referenced if the task has the
343 swap token and is in the middle of a page fault. */
344 if (mm != current->mm && has_swap_token(mm) &&
345 rwsem_is_locked(&mm->mmap_sem))
349 pte_unmap_unlock(pte, ptl);
354 static int page_referenced_anon(struct page *page)
356 unsigned int mapcount;
357 struct anon_vma *anon_vma;
358 struct vm_area_struct *vma;
361 anon_vma = page_lock_anon_vma(page);
365 mapcount = page_mapcount(page);
366 list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
367 referenced += page_referenced_one(page, vma, &mapcount);
371 spin_unlock(&anon_vma->lock);
376 * page_referenced_file - referenced check for object-based rmap
377 * @page: the page we're checking references on.
379 * For an object-based mapped page, find all the places it is mapped and
380 * check/clear the referenced flag. This is done by following the page->mapping
381 * pointer, then walking the chain of vmas it holds. It returns the number
382 * of references it found.
384 * This function is only called from page_referenced for object-based pages.
386 static int page_referenced_file(struct page *page)
388 unsigned int mapcount;
389 struct address_space *mapping = page->mapping;
390 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
391 struct vm_area_struct *vma;
392 struct prio_tree_iter iter;
396 * The caller's checks on page->mapping and !PageAnon have made
397 * sure that this is a file page: the check for page->mapping
398 * excludes the case just before it gets set on an anon page.
400 BUG_ON(PageAnon(page));
403 * The page lock not only makes sure that page->mapping cannot
404 * suddenly be NULLified by truncation, it makes sure that the
405 * structure at mapping cannot be freed and reused yet,
406 * so we can safely take mapping->i_mmap_lock.
408 BUG_ON(!PageLocked(page));
410 spin_lock(&mapping->i_mmap_lock);
413 * i_mmap_lock does not stabilize mapcount at all, but mapcount
414 * is more likely to be accurate if we note it after spinning.
416 mapcount = page_mapcount(page);
418 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
419 if ((vma->vm_flags & (VM_LOCKED|VM_MAYSHARE))
420 == (VM_LOCKED|VM_MAYSHARE)) {
424 referenced += page_referenced_one(page, vma, &mapcount);
429 spin_unlock(&mapping->i_mmap_lock);
434 * page_referenced - test if the page was referenced
435 * @page: the page to test
436 * @is_locked: caller holds lock on the page
438 * Quick test_and_clear_referenced for all mappings to a page,
439 * returns the number of ptes which referenced the page.
441 int page_referenced(struct page *page, int is_locked)
445 if (page_test_and_clear_young(page))
448 if (TestClearPageReferenced(page))
451 if (page_mapped(page) && page->mapping) {
453 referenced += page_referenced_anon(page);
455 referenced += page_referenced_file(page);
456 else if (TestSetPageLocked(page))
460 referenced += page_referenced_file(page);
468 * page_set_anon_rmap - setup new anonymous rmap
469 * @page: the page to add the mapping to
470 * @vma: the vm area in which the mapping is added
471 * @address: the user virtual address mapped
473 static void __page_set_anon_rmap(struct page *page,
474 struct vm_area_struct *vma, unsigned long address)
476 struct anon_vma *anon_vma = vma->anon_vma;
479 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
480 page->mapping = (struct address_space *) anon_vma;
482 page->index = linear_page_index(vma, address);
485 * nr_mapped state can be updated without turning off
486 * interrupts because it is not modified via interrupt.
488 __inc_page_state(nr_mapped);
492 * page_add_anon_rmap - add pte mapping to an anonymous page
493 * @page: the page to add the mapping to
494 * @vma: the vm area in which the mapping is added
495 * @address: the user virtual address mapped
497 * The caller needs to hold the pte lock.
499 void page_add_anon_rmap(struct page *page,
500 struct vm_area_struct *vma, unsigned long address)
502 if (atomic_inc_and_test(&page->_mapcount))
503 __page_set_anon_rmap(page, vma, address);
504 /* else checking page index and mapping is racy */
508 * page_add_new_anon_rmap - add pte mapping to a new anonymous page
509 * @page: the page to add the mapping to
510 * @vma: the vm area in which the mapping is added
511 * @address: the user virtual address mapped
513 * Same as page_add_anon_rmap but must only be called on *new* pages.
514 * This means the inc-and-test can be bypassed.
516 void page_add_new_anon_rmap(struct page *page,
517 struct vm_area_struct *vma, unsigned long address)
519 atomic_set(&page->_mapcount, 0); /* elevate count by 1 (starts at -1) */
520 __page_set_anon_rmap(page, vma, address);
524 * page_add_file_rmap - add pte mapping to a file page
525 * @page: the page to add the mapping to
527 * The caller needs to hold the pte lock.
529 void page_add_file_rmap(struct page *page)
531 BUG_ON(PageAnon(page));
532 BUG_ON(!pfn_valid(page_to_pfn(page)));
534 if (atomic_inc_and_test(&page->_mapcount))
535 __inc_page_state(nr_mapped);
539 * page_remove_rmap - take down pte mapping from a page
540 * @page: page to remove mapping from
542 * The caller needs to hold the pte lock.
544 void page_remove_rmap(struct page *page)
546 if (atomic_add_negative(-1, &page->_mapcount)) {
547 if (page_mapcount(page) < 0) {
548 printk (KERN_EMERG "Eeek! page_mapcount(page) went negative! (%d)\n", page_mapcount(page));
549 printk (KERN_EMERG " page->flags = %lx\n", page->flags);
550 printk (KERN_EMERG " page->count = %x\n", page_count(page));
551 printk (KERN_EMERG " page->mapping = %p\n", page->mapping);
554 BUG_ON(page_mapcount(page) < 0);
556 * It would be tidy to reset the PageAnon mapping here,
557 * but that might overwrite a racing page_add_anon_rmap
558 * which increments mapcount after us but sets mapping
559 * before us: so leave the reset to free_hot_cold_page,
560 * and remember that it's only reliable while mapped.
561 * Leaving it set also helps swapoff to reinstate ptes
562 * faster for those pages still in swapcache.
564 if (page_test_and_clear_dirty(page))
565 set_page_dirty(page);
566 __dec_page_state(nr_mapped);
571 * Subfunctions of try_to_unmap: try_to_unmap_one called
572 * repeatedly from either try_to_unmap_anon or try_to_unmap_file.
574 static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
577 struct mm_struct *mm = vma->vm_mm;
578 unsigned long address;
582 int ret = SWAP_AGAIN;
584 address = vma_address(page, vma);
585 if (address == -EFAULT)
588 pte = page_check_address(page, mm, address, &ptl);
593 * If the page is mlock()d, we cannot swap it out.
594 * If it's recently referenced (perhaps page_referenced
595 * skipped over this mm) then we should reactivate it.
597 if ((vma->vm_flags & VM_LOCKED) ||
598 (ptep_clear_flush_young(vma, address, pte)
604 /* Nuke the page table entry. */
605 flush_cache_page(vma, address, page_to_pfn(page));
606 pteval = ptep_clear_flush(vma, address, pte);
608 /* Move the dirty bit to the physical page now the pte is gone. */
609 if (pte_dirty(pteval))
610 set_page_dirty(page);
612 /* Update high watermark before we lower rss */
613 update_hiwater_rss(mm);
615 if (PageAnon(page)) {
616 swp_entry_t entry = { .val = page_private(page) };
618 * Store the swap location in the pte.
619 * See handle_pte_fault() ...
621 BUG_ON(!PageSwapCache(page));
622 swap_duplicate(entry);
623 if (list_empty(&mm->mmlist)) {
624 spin_lock(&mmlist_lock);
625 if (list_empty(&mm->mmlist))
626 list_add(&mm->mmlist, &init_mm.mmlist);
627 spin_unlock(&mmlist_lock);
629 set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
630 BUG_ON(pte_file(*pte));
631 dec_mm_counter(mm, anon_rss);
633 dec_mm_counter(mm, file_rss);
635 page_remove_rmap(page);
636 page_cache_release(page);
639 pte_unmap_unlock(pte, ptl);
645 * objrmap doesn't work for nonlinear VMAs because the assumption that
646 * offset-into-file correlates with offset-into-virtual-addresses does not hold.
647 * Consequently, given a particular page and its ->index, we cannot locate the
648 * ptes which are mapping that page without an exhaustive linear search.
650 * So what this code does is a mini "virtual scan" of each nonlinear VMA which
651 * maps the file to which the target page belongs. The ->vm_private_data field
652 * holds the current cursor into that scan. Successive searches will circulate
653 * around the vma's virtual address space.
655 * So as more replacement pressure is applied to the pages in a nonlinear VMA,
656 * more scanning pressure is placed against them as well. Eventually pages
657 * will become fully unmapped and are eligible for eviction.
659 * For very sparsely populated VMAs this is a little inefficient - chances are
660 * there there won't be many ptes located within the scan cluster. In this case
661 * maybe we could scan further - to the end of the pte page, perhaps.
663 #define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE)
664 #define CLUSTER_MASK (~(CLUSTER_SIZE - 1))
666 static void try_to_unmap_cluster(unsigned long cursor,
667 unsigned int *mapcount, struct vm_area_struct *vma)
669 struct mm_struct *mm = vma->vm_mm;
677 unsigned long address;
680 address = (vma->vm_start + cursor) & CLUSTER_MASK;
681 end = address + CLUSTER_SIZE;
682 if (address < vma->vm_start)
683 address = vma->vm_start;
684 if (end > vma->vm_end)
687 pgd = pgd_offset(mm, address);
688 if (!pgd_present(*pgd))
691 pud = pud_offset(pgd, address);
692 if (!pud_present(*pud))
695 pmd = pmd_offset(pud, address);
696 if (!pmd_present(*pmd))
699 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
701 /* Update high watermark before we lower rss */
702 update_hiwater_rss(mm);
704 for (; address < end; pte++, address += PAGE_SIZE) {
705 if (!pte_present(*pte))
707 page = vm_normal_page(vma, address, *pte);
708 BUG_ON(!page || PageAnon(page));
710 if (ptep_clear_flush_young(vma, address, pte))
713 /* Nuke the page table entry. */
714 flush_cache_page(vma, address, pte_pfn(*pte));
715 pteval = ptep_clear_flush(vma, address, pte);
717 /* If nonlinear, store the file page offset in the pte. */
718 if (page->index != linear_page_index(vma, address))
719 set_pte_at(mm, address, pte, pgoff_to_pte(page->index));
721 /* Move the dirty bit to the physical page now the pte is gone. */
722 if (pte_dirty(pteval))
723 set_page_dirty(page);
725 page_remove_rmap(page);
726 page_cache_release(page);
727 dec_mm_counter(mm, file_rss);
730 pte_unmap_unlock(pte - 1, ptl);
733 static int try_to_unmap_anon(struct page *page, int ignore_refs)
735 struct anon_vma *anon_vma;
736 struct vm_area_struct *vma;
737 int ret = SWAP_AGAIN;
739 anon_vma = page_lock_anon_vma(page);
743 list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
744 ret = try_to_unmap_one(page, vma, ignore_refs);
745 if (ret == SWAP_FAIL || !page_mapped(page))
748 spin_unlock(&anon_vma->lock);
753 * try_to_unmap_file - unmap file page using the object-based rmap method
754 * @page: the page to unmap
756 * Find all the mappings of a page using the mapping pointer and the vma chains
757 * contained in the address_space struct it points to.
759 * This function is only called from try_to_unmap for object-based pages.
761 static int try_to_unmap_file(struct page *page, int ignore_refs)
763 struct address_space *mapping = page->mapping;
764 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
765 struct vm_area_struct *vma;
766 struct prio_tree_iter iter;
767 int ret = SWAP_AGAIN;
768 unsigned long cursor;
769 unsigned long max_nl_cursor = 0;
770 unsigned long max_nl_size = 0;
771 unsigned int mapcount;
773 spin_lock(&mapping->i_mmap_lock);
774 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
775 ret = try_to_unmap_one(page, vma, ignore_refs);
776 if (ret == SWAP_FAIL || !page_mapped(page))
780 if (list_empty(&mapping->i_mmap_nonlinear))
783 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
784 shared.vm_set.list) {
785 if (vma->vm_flags & VM_LOCKED)
787 cursor = (unsigned long) vma->vm_private_data;
788 if (cursor > max_nl_cursor)
789 max_nl_cursor = cursor;
790 cursor = vma->vm_end - vma->vm_start;
791 if (cursor > max_nl_size)
792 max_nl_size = cursor;
795 if (max_nl_size == 0) { /* any nonlinears locked or reserved */
801 * We don't try to search for this page in the nonlinear vmas,
802 * and page_referenced wouldn't have found it anyway. Instead
803 * just walk the nonlinear vmas trying to age and unmap some.
804 * The mapcount of the page we came in with is irrelevant,
805 * but even so use it as a guide to how hard we should try?
807 mapcount = page_mapcount(page);
810 cond_resched_lock(&mapping->i_mmap_lock);
812 max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK;
813 if (max_nl_cursor == 0)
814 max_nl_cursor = CLUSTER_SIZE;
817 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
818 shared.vm_set.list) {
819 if (vma->vm_flags & VM_LOCKED)
821 cursor = (unsigned long) vma->vm_private_data;
822 while ( cursor < max_nl_cursor &&
823 cursor < vma->vm_end - vma->vm_start) {
824 try_to_unmap_cluster(cursor, &mapcount, vma);
825 cursor += CLUSTER_SIZE;
826 vma->vm_private_data = (void *) cursor;
827 if ((int)mapcount <= 0)
830 vma->vm_private_data = (void *) max_nl_cursor;
832 cond_resched_lock(&mapping->i_mmap_lock);
833 max_nl_cursor += CLUSTER_SIZE;
834 } while (max_nl_cursor <= max_nl_size);
837 * Don't loop forever (perhaps all the remaining pages are
838 * in locked vmas). Reset cursor on all unreserved nonlinear
839 * vmas, now forgetting on which ones it had fallen behind.
841 list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list)
842 vma->vm_private_data = NULL;
844 spin_unlock(&mapping->i_mmap_lock);
849 * try_to_unmap - try to remove all page table mappings to a page
850 * @page: the page to get unmapped
852 * Tries to remove all the page table entries which are mapping this
853 * page, used in the pageout path. Caller must hold the page lock.
856 * SWAP_SUCCESS - we succeeded in removing all mappings
857 * SWAP_AGAIN - we missed a mapping, try again later
858 * SWAP_FAIL - the page is unswappable
860 int try_to_unmap(struct page *page, int ignore_refs)
864 BUG_ON(!PageLocked(page));
867 ret = try_to_unmap_anon(page, ignore_refs);
869 ret = try_to_unmap_file(page, ignore_refs);
871 if (!page_mapped(page))