]>
git.proxmox.com Git - mirror_ubuntu-bionic-kernel.git/blob - mm/rmap.c
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 struct kmem_cache
*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
, struct kmem_cache
*cachep
,
172 if ((flags
& (SLAB_CTOR_VERIFY
|SLAB_CTOR_CONSTRUCTOR
)) ==
173 SLAB_CTOR_CONSTRUCTOR
) {
174 struct anon_vma
*anon_vma
= data
;
176 spin_lock_init(&anon_vma
->lock
);
177 INIT_LIST_HEAD(&anon_vma
->head
);
181 void __init
anon_vma_init(void)
183 anon_vma_cachep
= kmem_cache_create("anon_vma", sizeof(struct anon_vma
),
184 0, SLAB_DESTROY_BY_RCU
|SLAB_PANIC
, anon_vma_ctor
, NULL
);
188 * Getting a lock on a stable anon_vma from a page off the LRU is
189 * tricky: page_lock_anon_vma rely on RCU to guard against the races.
191 static struct anon_vma
*page_lock_anon_vma(struct page
*page
)
193 struct anon_vma
*anon_vma
= NULL
;
194 unsigned long anon_mapping
;
197 anon_mapping
= (unsigned long) page
->mapping
;
198 if (!(anon_mapping
& PAGE_MAPPING_ANON
))
200 if (!page_mapped(page
))
203 anon_vma
= (struct anon_vma
*) (anon_mapping
- PAGE_MAPPING_ANON
);
204 spin_lock(&anon_vma
->lock
);
210 #ifdef CONFIG_MIGRATION
212 * Remove an anonymous page from swap replacing the swap pte's
213 * through real pte's pointing to valid pages and then releasing
214 * the page from the swap cache.
216 * Must hold page lock on page and mmap_sem of one vma that contains
219 void remove_from_swap(struct page
*page
)
221 struct anon_vma
*anon_vma
;
222 struct vm_area_struct
*vma
;
223 unsigned long mapping
;
225 if (!PageSwapCache(page
))
228 mapping
= (unsigned long)page
->mapping
;
230 if (!mapping
|| (mapping
& PAGE_MAPPING_ANON
) == 0)
234 * We hold the mmap_sem lock. So no need to call page_lock_anon_vma.
236 anon_vma
= (struct anon_vma
*) (mapping
- PAGE_MAPPING_ANON
);
237 spin_lock(&anon_vma
->lock
);
239 list_for_each_entry(vma
, &anon_vma
->head
, anon_vma_node
)
240 remove_vma_swap(vma
, page
);
242 spin_unlock(&anon_vma
->lock
);
243 delete_from_swap_cache(page
);
245 EXPORT_SYMBOL(remove_from_swap
);
249 * At what user virtual address is page expected in vma?
251 static inline unsigned long
252 vma_address(struct page
*page
, struct vm_area_struct
*vma
)
254 pgoff_t pgoff
= page
->index
<< (PAGE_CACHE_SHIFT
- PAGE_SHIFT
);
255 unsigned long address
;
257 address
= vma
->vm_start
+ ((pgoff
- vma
->vm_pgoff
) << PAGE_SHIFT
);
258 if (unlikely(address
< vma
->vm_start
|| address
>= vma
->vm_end
)) {
259 /* page should be within any vma from prio_tree_next */
260 BUG_ON(!PageAnon(page
));
267 * At what user virtual address is page expected in vma? checking that the
268 * page matches the vma: currently only used on anon pages, by unuse_vma;
270 unsigned long page_address_in_vma(struct page
*page
, struct vm_area_struct
*vma
)
272 if (PageAnon(page
)) {
273 if ((void *)vma
->anon_vma
!=
274 (void *)page
->mapping
- PAGE_MAPPING_ANON
)
276 } else if (page
->mapping
&& !(vma
->vm_flags
& VM_NONLINEAR
)) {
278 vma
->vm_file
->f_mapping
!= page
->mapping
)
282 return vma_address(page
, vma
);
286 * Check that @page is mapped at @address into @mm.
288 * On success returns with pte mapped and locked.
290 pte_t
*page_check_address(struct page
*page
, struct mm_struct
*mm
,
291 unsigned long address
, spinlock_t
**ptlp
)
299 pgd
= pgd_offset(mm
, address
);
300 if (!pgd_present(*pgd
))
303 pud
= pud_offset(pgd
, address
);
304 if (!pud_present(*pud
))
307 pmd
= pmd_offset(pud
, address
);
308 if (!pmd_present(*pmd
))
311 pte
= pte_offset_map(pmd
, address
);
312 /* Make a quick check before getting the lock */
313 if (!pte_present(*pte
)) {
318 ptl
= pte_lockptr(mm
, pmd
);
320 if (pte_present(*pte
) && page_to_pfn(page
) == pte_pfn(*pte
)) {
324 pte_unmap_unlock(pte
, ptl
);
329 * Subfunctions of page_referenced: page_referenced_one called
330 * repeatedly from either page_referenced_anon or page_referenced_file.
332 static int page_referenced_one(struct page
*page
,
333 struct vm_area_struct
*vma
, unsigned int *mapcount
)
335 struct mm_struct
*mm
= vma
->vm_mm
;
336 unsigned long address
;
341 address
= vma_address(page
, vma
);
342 if (address
== -EFAULT
)
345 pte
= page_check_address(page
, mm
, address
, &ptl
);
349 if (ptep_clear_flush_young(vma
, address
, pte
))
352 /* Pretend the page is referenced if the task has the
353 swap token and is in the middle of a page fault. */
354 if (mm
!= current
->mm
&& has_swap_token(mm
) &&
355 rwsem_is_locked(&mm
->mmap_sem
))
359 pte_unmap_unlock(pte
, ptl
);
364 static int page_referenced_anon(struct page
*page
)
366 unsigned int mapcount
;
367 struct anon_vma
*anon_vma
;
368 struct vm_area_struct
*vma
;
371 anon_vma
= page_lock_anon_vma(page
);
375 mapcount
= page_mapcount(page
);
376 list_for_each_entry(vma
, &anon_vma
->head
, anon_vma_node
) {
377 referenced
+= page_referenced_one(page
, vma
, &mapcount
);
381 spin_unlock(&anon_vma
->lock
);
386 * page_referenced_file - referenced check for object-based rmap
387 * @page: the page we're checking references on.
389 * For an object-based mapped page, find all the places it is mapped and
390 * check/clear the referenced flag. This is done by following the page->mapping
391 * pointer, then walking the chain of vmas it holds. It returns the number
392 * of references it found.
394 * This function is only called from page_referenced for object-based pages.
396 static int page_referenced_file(struct page
*page
)
398 unsigned int mapcount
;
399 struct address_space
*mapping
= page
->mapping
;
400 pgoff_t pgoff
= page
->index
<< (PAGE_CACHE_SHIFT
- PAGE_SHIFT
);
401 struct vm_area_struct
*vma
;
402 struct prio_tree_iter iter
;
406 * The caller's checks on page->mapping and !PageAnon have made
407 * sure that this is a file page: the check for page->mapping
408 * excludes the case just before it gets set on an anon page.
410 BUG_ON(PageAnon(page
));
413 * The page lock not only makes sure that page->mapping cannot
414 * suddenly be NULLified by truncation, it makes sure that the
415 * structure at mapping cannot be freed and reused yet,
416 * so we can safely take mapping->i_mmap_lock.
418 BUG_ON(!PageLocked(page
));
420 spin_lock(&mapping
->i_mmap_lock
);
423 * i_mmap_lock does not stabilize mapcount at all, but mapcount
424 * is more likely to be accurate if we note it after spinning.
426 mapcount
= page_mapcount(page
);
428 vma_prio_tree_foreach(vma
, &iter
, &mapping
->i_mmap
, pgoff
, pgoff
) {
429 if ((vma
->vm_flags
& (VM_LOCKED
|VM_MAYSHARE
))
430 == (VM_LOCKED
|VM_MAYSHARE
)) {
434 referenced
+= page_referenced_one(page
, vma
, &mapcount
);
439 spin_unlock(&mapping
->i_mmap_lock
);
444 * page_referenced - test if the page was referenced
445 * @page: the page to test
446 * @is_locked: caller holds lock on the page
448 * Quick test_and_clear_referenced for all mappings to a page,
449 * returns the number of ptes which referenced the page.
451 int page_referenced(struct page
*page
, int is_locked
)
455 if (page_test_and_clear_young(page
))
458 if (TestClearPageReferenced(page
))
461 if (page_mapped(page
) && page
->mapping
) {
463 referenced
+= page_referenced_anon(page
);
465 referenced
+= page_referenced_file(page
);
466 else if (TestSetPageLocked(page
))
470 referenced
+= page_referenced_file(page
);
478 * page_set_anon_rmap - setup new anonymous rmap
479 * @page: the page to add the mapping to
480 * @vma: the vm area in which the mapping is added
481 * @address: the user virtual address mapped
483 static void __page_set_anon_rmap(struct page
*page
,
484 struct vm_area_struct
*vma
, unsigned long address
)
486 struct anon_vma
*anon_vma
= vma
->anon_vma
;
489 anon_vma
= (void *) anon_vma
+ PAGE_MAPPING_ANON
;
490 page
->mapping
= (struct address_space
*) anon_vma
;
492 page
->index
= linear_page_index(vma
, address
);
495 * nr_mapped state can be updated without turning off
496 * interrupts because it is not modified via interrupt.
498 __inc_page_state(nr_mapped
);
502 * page_add_anon_rmap - add pte mapping to an anonymous page
503 * @page: the page to add the mapping to
504 * @vma: the vm area in which the mapping is added
505 * @address: the user virtual address mapped
507 * The caller needs to hold the pte lock.
509 void page_add_anon_rmap(struct page
*page
,
510 struct vm_area_struct
*vma
, unsigned long address
)
512 if (atomic_inc_and_test(&page
->_mapcount
))
513 __page_set_anon_rmap(page
, vma
, address
);
514 /* else checking page index and mapping is racy */
518 * page_add_new_anon_rmap - add pte mapping to a new anonymous page
519 * @page: the page to add the mapping to
520 * @vma: the vm area in which the mapping is added
521 * @address: the user virtual address mapped
523 * Same as page_add_anon_rmap but must only be called on *new* pages.
524 * This means the inc-and-test can be bypassed.
526 void page_add_new_anon_rmap(struct page
*page
,
527 struct vm_area_struct
*vma
, unsigned long address
)
529 atomic_set(&page
->_mapcount
, 0); /* elevate count by 1 (starts at -1) */
530 __page_set_anon_rmap(page
, vma
, address
);
534 * page_add_file_rmap - add pte mapping to a file page
535 * @page: the page to add the mapping to
537 * The caller needs to hold the pte lock.
539 void page_add_file_rmap(struct page
*page
)
541 if (atomic_inc_and_test(&page
->_mapcount
))
542 __inc_page_state(nr_mapped
);
546 * page_remove_rmap - take down pte mapping from a page
547 * @page: page to remove mapping from
549 * The caller needs to hold the pte lock.
551 void page_remove_rmap(struct page
*page
)
553 if (atomic_add_negative(-1, &page
->_mapcount
)) {
554 if (page_mapcount(page
) < 0) {
555 printk (KERN_EMERG
"Eeek! page_mapcount(page) went negative! (%d)\n", page_mapcount(page
));
556 printk (KERN_EMERG
" page->flags = %lx\n", page
->flags
);
557 printk (KERN_EMERG
" page->count = %x\n", page_count(page
));
558 printk (KERN_EMERG
" page->mapping = %p\n", page
->mapping
);
561 BUG_ON(page_mapcount(page
) < 0);
563 * It would be tidy to reset the PageAnon mapping here,
564 * but that might overwrite a racing page_add_anon_rmap
565 * which increments mapcount after us but sets mapping
566 * before us: so leave the reset to free_hot_cold_page,
567 * and remember that it's only reliable while mapped.
568 * Leaving it set also helps swapoff to reinstate ptes
569 * faster for those pages still in swapcache.
571 if (page_test_and_clear_dirty(page
))
572 set_page_dirty(page
);
573 __dec_page_state(nr_mapped
);
578 * Subfunctions of try_to_unmap: try_to_unmap_one called
579 * repeatedly from either try_to_unmap_anon or try_to_unmap_file.
581 static int try_to_unmap_one(struct page
*page
, struct vm_area_struct
*vma
,
584 struct mm_struct
*mm
= vma
->vm_mm
;
585 unsigned long address
;
589 int ret
= SWAP_AGAIN
;
591 address
= vma_address(page
, vma
);
592 if (address
== -EFAULT
)
595 pte
= page_check_address(page
, mm
, address
, &ptl
);
600 * If the page is mlock()d, we cannot swap it out.
601 * If it's recently referenced (perhaps page_referenced
602 * skipped over this mm) then we should reactivate it.
604 if ((vma
->vm_flags
& VM_LOCKED
) ||
605 (ptep_clear_flush_young(vma
, address
, pte
)
611 /* Nuke the page table entry. */
612 flush_cache_page(vma
, address
, page_to_pfn(page
));
613 pteval
= ptep_clear_flush(vma
, address
, pte
);
615 /* Move the dirty bit to the physical page now the pte is gone. */
616 if (pte_dirty(pteval
))
617 set_page_dirty(page
);
619 /* Update high watermark before we lower rss */
620 update_hiwater_rss(mm
);
622 if (PageAnon(page
)) {
623 swp_entry_t entry
= { .val
= page_private(page
) };
625 * Store the swap location in the pte.
626 * See handle_pte_fault() ...
628 BUG_ON(!PageSwapCache(page
));
629 swap_duplicate(entry
);
630 if (list_empty(&mm
->mmlist
)) {
631 spin_lock(&mmlist_lock
);
632 if (list_empty(&mm
->mmlist
))
633 list_add(&mm
->mmlist
, &init_mm
.mmlist
);
634 spin_unlock(&mmlist_lock
);
636 set_pte_at(mm
, address
, pte
, swp_entry_to_pte(entry
));
637 BUG_ON(pte_file(*pte
));
638 dec_mm_counter(mm
, anon_rss
);
640 dec_mm_counter(mm
, file_rss
);
642 page_remove_rmap(page
);
643 page_cache_release(page
);
646 pte_unmap_unlock(pte
, ptl
);
652 * objrmap doesn't work for nonlinear VMAs because the assumption that
653 * offset-into-file correlates with offset-into-virtual-addresses does not hold.
654 * Consequently, given a particular page and its ->index, we cannot locate the
655 * ptes which are mapping that page without an exhaustive linear search.
657 * So what this code does is a mini "virtual scan" of each nonlinear VMA which
658 * maps the file to which the target page belongs. The ->vm_private_data field
659 * holds the current cursor into that scan. Successive searches will circulate
660 * around the vma's virtual address space.
662 * So as more replacement pressure is applied to the pages in a nonlinear VMA,
663 * more scanning pressure is placed against them as well. Eventually pages
664 * will become fully unmapped and are eligible for eviction.
666 * For very sparsely populated VMAs this is a little inefficient - chances are
667 * there there won't be many ptes located within the scan cluster. In this case
668 * maybe we could scan further - to the end of the pte page, perhaps.
670 #define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE)
671 #define CLUSTER_MASK (~(CLUSTER_SIZE - 1))
673 static void try_to_unmap_cluster(unsigned long cursor
,
674 unsigned int *mapcount
, struct vm_area_struct
*vma
)
676 struct mm_struct
*mm
= vma
->vm_mm
;
684 unsigned long address
;
687 address
= (vma
->vm_start
+ cursor
) & CLUSTER_MASK
;
688 end
= address
+ CLUSTER_SIZE
;
689 if (address
< vma
->vm_start
)
690 address
= vma
->vm_start
;
691 if (end
> vma
->vm_end
)
694 pgd
= pgd_offset(mm
, address
);
695 if (!pgd_present(*pgd
))
698 pud
= pud_offset(pgd
, address
);
699 if (!pud_present(*pud
))
702 pmd
= pmd_offset(pud
, address
);
703 if (!pmd_present(*pmd
))
706 pte
= pte_offset_map_lock(mm
, pmd
, address
, &ptl
);
708 /* Update high watermark before we lower rss */
709 update_hiwater_rss(mm
);
711 for (; address
< end
; pte
++, address
+= PAGE_SIZE
) {
712 if (!pte_present(*pte
))
714 page
= vm_normal_page(vma
, address
, *pte
);
715 BUG_ON(!page
|| PageAnon(page
));
717 if (ptep_clear_flush_young(vma
, address
, pte
))
720 /* Nuke the page table entry. */
721 flush_cache_page(vma
, address
, pte_pfn(*pte
));
722 pteval
= ptep_clear_flush(vma
, address
, pte
);
724 /* If nonlinear, store the file page offset in the pte. */
725 if (page
->index
!= linear_page_index(vma
, address
))
726 set_pte_at(mm
, address
, pte
, pgoff_to_pte(page
->index
));
728 /* Move the dirty bit to the physical page now the pte is gone. */
729 if (pte_dirty(pteval
))
730 set_page_dirty(page
);
732 page_remove_rmap(page
);
733 page_cache_release(page
);
734 dec_mm_counter(mm
, file_rss
);
737 pte_unmap_unlock(pte
- 1, ptl
);
740 static int try_to_unmap_anon(struct page
*page
, int ignore_refs
)
742 struct anon_vma
*anon_vma
;
743 struct vm_area_struct
*vma
;
744 int ret
= SWAP_AGAIN
;
746 anon_vma
= page_lock_anon_vma(page
);
750 list_for_each_entry(vma
, &anon_vma
->head
, anon_vma_node
) {
751 ret
= try_to_unmap_one(page
, vma
, ignore_refs
);
752 if (ret
== SWAP_FAIL
|| !page_mapped(page
))
755 spin_unlock(&anon_vma
->lock
);
760 * try_to_unmap_file - unmap file page using the object-based rmap method
761 * @page: the page to unmap
763 * Find all the mappings of a page using the mapping pointer and the vma chains
764 * contained in the address_space struct it points to.
766 * This function is only called from try_to_unmap for object-based pages.
768 static int try_to_unmap_file(struct page
*page
, int ignore_refs
)
770 struct address_space
*mapping
= page
->mapping
;
771 pgoff_t pgoff
= page
->index
<< (PAGE_CACHE_SHIFT
- PAGE_SHIFT
);
772 struct vm_area_struct
*vma
;
773 struct prio_tree_iter iter
;
774 int ret
= SWAP_AGAIN
;
775 unsigned long cursor
;
776 unsigned long max_nl_cursor
= 0;
777 unsigned long max_nl_size
= 0;
778 unsigned int mapcount
;
780 spin_lock(&mapping
->i_mmap_lock
);
781 vma_prio_tree_foreach(vma
, &iter
, &mapping
->i_mmap
, pgoff
, pgoff
) {
782 ret
= try_to_unmap_one(page
, vma
, ignore_refs
);
783 if (ret
== SWAP_FAIL
|| !page_mapped(page
))
787 if (list_empty(&mapping
->i_mmap_nonlinear
))
790 list_for_each_entry(vma
, &mapping
->i_mmap_nonlinear
,
791 shared
.vm_set
.list
) {
792 if (vma
->vm_flags
& VM_LOCKED
)
794 cursor
= (unsigned long) vma
->vm_private_data
;
795 if (cursor
> max_nl_cursor
)
796 max_nl_cursor
= cursor
;
797 cursor
= vma
->vm_end
- vma
->vm_start
;
798 if (cursor
> max_nl_size
)
799 max_nl_size
= cursor
;
802 if (max_nl_size
== 0) { /* any nonlinears locked or reserved */
808 * We don't try to search for this page in the nonlinear vmas,
809 * and page_referenced wouldn't have found it anyway. Instead
810 * just walk the nonlinear vmas trying to age and unmap some.
811 * The mapcount of the page we came in with is irrelevant,
812 * but even so use it as a guide to how hard we should try?
814 mapcount
= page_mapcount(page
);
817 cond_resched_lock(&mapping
->i_mmap_lock
);
819 max_nl_size
= (max_nl_size
+ CLUSTER_SIZE
- 1) & CLUSTER_MASK
;
820 if (max_nl_cursor
== 0)
821 max_nl_cursor
= CLUSTER_SIZE
;
824 list_for_each_entry(vma
, &mapping
->i_mmap_nonlinear
,
825 shared
.vm_set
.list
) {
826 if (vma
->vm_flags
& VM_LOCKED
)
828 cursor
= (unsigned long) vma
->vm_private_data
;
829 while ( cursor
< max_nl_cursor
&&
830 cursor
< vma
->vm_end
- vma
->vm_start
) {
831 try_to_unmap_cluster(cursor
, &mapcount
, vma
);
832 cursor
+= CLUSTER_SIZE
;
833 vma
->vm_private_data
= (void *) cursor
;
834 if ((int)mapcount
<= 0)
837 vma
->vm_private_data
= (void *) max_nl_cursor
;
839 cond_resched_lock(&mapping
->i_mmap_lock
);
840 max_nl_cursor
+= CLUSTER_SIZE
;
841 } while (max_nl_cursor
<= max_nl_size
);
844 * Don't loop forever (perhaps all the remaining pages are
845 * in locked vmas). Reset cursor on all unreserved nonlinear
846 * vmas, now forgetting on which ones it had fallen behind.
848 list_for_each_entry(vma
, &mapping
->i_mmap_nonlinear
, shared
.vm_set
.list
)
849 vma
->vm_private_data
= NULL
;
851 spin_unlock(&mapping
->i_mmap_lock
);
856 * try_to_unmap - try to remove all page table mappings to a page
857 * @page: the page to get unmapped
859 * Tries to remove all the page table entries which are mapping this
860 * page, used in the pageout path. Caller must hold the page lock.
863 * SWAP_SUCCESS - we succeeded in removing all mappings
864 * SWAP_AGAIN - we missed a mapping, try again later
865 * SWAP_FAIL - the page is unswappable
867 int try_to_unmap(struct page
*page
, int ignore_refs
)
871 BUG_ON(!PageLocked(page
));
874 ret
= try_to_unmap_anon(page
, ignore_refs
);
876 ret
= try_to_unmap_file(page
, ignore_refs
);
878 if (!page_mapped(page
))