Merge git://git.kernel.org/pub/scm/linux/kernel/git/paulus/powerpc-merge
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / mm / rmap.c
blobdfbb89f99a15a610b9463ea84a35068712187d23
1 /*
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)
24 * inode->i_alloc_sem
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.
31 * mm->mmap_sem
32 * page->flags PG_locked (lock_page)
33 * mapping->i_mmap_lock
34 * anon_vma->lock
35 * mm->page_table_lock or pte_lock
36 * zone->lru_lock (in mark_page_accessed)
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)
47 #include <linux/mm.h>
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>
56 #include <asm/tlbflush.h>
58 //#define RMAP_DEBUG /* can be enabled only for debugging */
60 kmem_cache_t *anon_vma_cachep;
62 static inline void validate_anon_vma(struct vm_area_struct *find_vma)
64 #ifdef RMAP_DEBUG
65 struct anon_vma *anon_vma = find_vma->anon_vma;
66 struct vm_area_struct *vma;
67 unsigned int mapcount = 0;
68 int found = 0;
70 list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
71 mapcount++;
72 BUG_ON(mapcount > 100000);
73 if (vma == find_vma)
74 found = 1;
76 BUG_ON(!found);
77 #endif
80 /* This must be called under the mmap_sem. */
81 int anon_vma_prepare(struct vm_area_struct *vma)
83 struct anon_vma *anon_vma = vma->anon_vma;
85 might_sleep();
86 if (unlikely(!anon_vma)) {
87 struct mm_struct *mm = vma->vm_mm;
88 struct anon_vma *allocated, *locked;
90 anon_vma = find_mergeable_anon_vma(vma);
91 if (anon_vma) {
92 allocated = NULL;
93 locked = anon_vma;
94 spin_lock(&locked->lock);
95 } else {
96 anon_vma = anon_vma_alloc();
97 if (unlikely(!anon_vma))
98 return -ENOMEM;
99 allocated = anon_vma;
100 locked = NULL;
103 /* page_table_lock to protect against threads */
104 spin_lock(&mm->page_table_lock);
105 if (likely(!vma->anon_vma)) {
106 vma->anon_vma = anon_vma;
107 list_add(&vma->anon_vma_node, &anon_vma->head);
108 allocated = NULL;
110 spin_unlock(&mm->page_table_lock);
112 if (locked)
113 spin_unlock(&locked->lock);
114 if (unlikely(allocated))
115 anon_vma_free(allocated);
117 return 0;
120 void __anon_vma_merge(struct vm_area_struct *vma, struct vm_area_struct *next)
122 BUG_ON(vma->anon_vma != next->anon_vma);
123 list_del(&next->anon_vma_node);
126 void __anon_vma_link(struct vm_area_struct *vma)
128 struct anon_vma *anon_vma = vma->anon_vma;
130 if (anon_vma) {
131 list_add(&vma->anon_vma_node, &anon_vma->head);
132 validate_anon_vma(vma);
136 void anon_vma_link(struct vm_area_struct *vma)
138 struct anon_vma *anon_vma = vma->anon_vma;
140 if (anon_vma) {
141 spin_lock(&anon_vma->lock);
142 list_add(&vma->anon_vma_node, &anon_vma->head);
143 validate_anon_vma(vma);
144 spin_unlock(&anon_vma->lock);
148 void anon_vma_unlink(struct vm_area_struct *vma)
150 struct anon_vma *anon_vma = vma->anon_vma;
151 int empty;
153 if (!anon_vma)
154 return;
156 spin_lock(&anon_vma->lock);
157 validate_anon_vma(vma);
158 list_del(&vma->anon_vma_node);
160 /* We must garbage collect the anon_vma if it's empty */
161 empty = list_empty(&anon_vma->head);
162 spin_unlock(&anon_vma->lock);
164 if (empty)
165 anon_vma_free(anon_vma);
168 static void anon_vma_ctor(void *data, kmem_cache_t *cachep, unsigned long flags)
170 if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
171 SLAB_CTOR_CONSTRUCTOR) {
172 struct anon_vma *anon_vma = data;
174 spin_lock_init(&anon_vma->lock);
175 INIT_LIST_HEAD(&anon_vma->head);
179 void __init anon_vma_init(void)
181 anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
182 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor, NULL);
186 * Getting a lock on a stable anon_vma from a page off the LRU is
187 * tricky: page_lock_anon_vma rely on RCU to guard against the races.
189 static struct anon_vma *page_lock_anon_vma(struct page *page)
191 struct anon_vma *anon_vma = NULL;
192 unsigned long anon_mapping;
194 rcu_read_lock();
195 anon_mapping = (unsigned long) page->mapping;
196 if (!(anon_mapping & PAGE_MAPPING_ANON))
197 goto out;
198 if (!page_mapped(page))
199 goto out;
201 anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
202 spin_lock(&anon_vma->lock);
203 out:
204 rcu_read_unlock();
205 return anon_vma;
209 * At what user virtual address is page expected in vma?
211 static inline unsigned long
212 vma_address(struct page *page, struct vm_area_struct *vma)
214 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
215 unsigned long address;
217 address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
218 if (unlikely(address < vma->vm_start || address >= vma->vm_end)) {
219 /* page should be within any vma from prio_tree_next */
220 BUG_ON(!PageAnon(page));
221 return -EFAULT;
223 return address;
227 * At what user virtual address is page expected in vma? checking that the
228 * page matches the vma: currently only used on anon pages, by unuse_vma;
230 unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
232 if (PageAnon(page)) {
233 if ((void *)vma->anon_vma !=
234 (void *)page->mapping - PAGE_MAPPING_ANON)
235 return -EFAULT;
236 } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
237 if (!vma->vm_file ||
238 vma->vm_file->f_mapping != page->mapping)
239 return -EFAULT;
240 } else
241 return -EFAULT;
242 return vma_address(page, vma);
246 * Check that @page is mapped at @address into @mm.
248 * On success returns with pte mapped and locked.
250 pte_t *page_check_address(struct page *page, struct mm_struct *mm,
251 unsigned long address, spinlock_t **ptlp)
253 pgd_t *pgd;
254 pud_t *pud;
255 pmd_t *pmd;
256 pte_t *pte;
257 spinlock_t *ptl;
259 pgd = pgd_offset(mm, address);
260 if (!pgd_present(*pgd))
261 return NULL;
263 pud = pud_offset(pgd, address);
264 if (!pud_present(*pud))
265 return NULL;
267 pmd = pmd_offset(pud, address);
268 if (!pmd_present(*pmd))
269 return NULL;
271 pte = pte_offset_map(pmd, address);
272 /* Make a quick check before getting the lock */
273 if (!pte_present(*pte)) {
274 pte_unmap(pte);
275 return NULL;
278 ptl = pte_lockptr(mm, pmd);
279 spin_lock(ptl);
280 if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) {
281 *ptlp = ptl;
282 return pte;
284 pte_unmap_unlock(pte, ptl);
285 return NULL;
289 * Subfunctions of page_referenced: page_referenced_one called
290 * repeatedly from either page_referenced_anon or page_referenced_file.
292 static int page_referenced_one(struct page *page,
293 struct vm_area_struct *vma, unsigned int *mapcount)
295 struct mm_struct *mm = vma->vm_mm;
296 unsigned long address;
297 pte_t *pte;
298 spinlock_t *ptl;
299 int referenced = 0;
301 address = vma_address(page, vma);
302 if (address == -EFAULT)
303 goto out;
305 pte = page_check_address(page, mm, address, &ptl);
306 if (!pte)
307 goto out;
309 if (ptep_clear_flush_young(vma, address, pte))
310 referenced++;
312 /* Pretend the page is referenced if the task has the
313 swap token and is in the middle of a page fault. */
314 if (mm != current->mm && has_swap_token(mm) &&
315 rwsem_is_locked(&mm->mmap_sem))
316 referenced++;
318 (*mapcount)--;
319 pte_unmap_unlock(pte, ptl);
320 out:
321 return referenced;
324 static int page_referenced_anon(struct page *page)
326 unsigned int mapcount;
327 struct anon_vma *anon_vma;
328 struct vm_area_struct *vma;
329 int referenced = 0;
331 anon_vma = page_lock_anon_vma(page);
332 if (!anon_vma)
333 return referenced;
335 mapcount = page_mapcount(page);
336 list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
337 referenced += page_referenced_one(page, vma, &mapcount);
338 if (!mapcount)
339 break;
341 spin_unlock(&anon_vma->lock);
342 return referenced;
346 * page_referenced_file - referenced check for object-based rmap
347 * @page: the page we're checking references on.
349 * For an object-based mapped page, find all the places it is mapped and
350 * check/clear the referenced flag. This is done by following the page->mapping
351 * pointer, then walking the chain of vmas it holds. It returns the number
352 * of references it found.
354 * This function is only called from page_referenced for object-based pages.
356 static int page_referenced_file(struct page *page)
358 unsigned int mapcount;
359 struct address_space *mapping = page->mapping;
360 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
361 struct vm_area_struct *vma;
362 struct prio_tree_iter iter;
363 int referenced = 0;
366 * The caller's checks on page->mapping and !PageAnon have made
367 * sure that this is a file page: the check for page->mapping
368 * excludes the case just before it gets set on an anon page.
370 BUG_ON(PageAnon(page));
373 * The page lock not only makes sure that page->mapping cannot
374 * suddenly be NULLified by truncation, it makes sure that the
375 * structure at mapping cannot be freed and reused yet,
376 * so we can safely take mapping->i_mmap_lock.
378 BUG_ON(!PageLocked(page));
380 spin_lock(&mapping->i_mmap_lock);
383 * i_mmap_lock does not stabilize mapcount at all, but mapcount
384 * is more likely to be accurate if we note it after spinning.
386 mapcount = page_mapcount(page);
388 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
389 if ((vma->vm_flags & (VM_LOCKED|VM_MAYSHARE))
390 == (VM_LOCKED|VM_MAYSHARE)) {
391 referenced++;
392 break;
394 referenced += page_referenced_one(page, vma, &mapcount);
395 if (!mapcount)
396 break;
399 spin_unlock(&mapping->i_mmap_lock);
400 return referenced;
404 * page_referenced - test if the page was referenced
405 * @page: the page to test
406 * @is_locked: caller holds lock on the page
408 * Quick test_and_clear_referenced for all mappings to a page,
409 * returns the number of ptes which referenced the page.
411 int page_referenced(struct page *page, int is_locked)
413 int referenced = 0;
415 if (page_test_and_clear_young(page))
416 referenced++;
418 if (TestClearPageReferenced(page))
419 referenced++;
421 if (page_mapped(page) && page->mapping) {
422 if (PageAnon(page))
423 referenced += page_referenced_anon(page);
424 else if (is_locked)
425 referenced += page_referenced_file(page);
426 else if (TestSetPageLocked(page))
427 referenced++;
428 else {
429 if (page->mapping)
430 referenced += page_referenced_file(page);
431 unlock_page(page);
434 return referenced;
438 * page_set_anon_rmap - setup new anonymous rmap
439 * @page: the page to add the mapping to
440 * @vma: the vm area in which the mapping is added
441 * @address: the user virtual address mapped
443 static void __page_set_anon_rmap(struct page *page,
444 struct vm_area_struct *vma, unsigned long address)
446 struct anon_vma *anon_vma = vma->anon_vma;
448 BUG_ON(!anon_vma);
449 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
450 page->mapping = (struct address_space *) anon_vma;
452 page->index = linear_page_index(vma, address);
455 * nr_mapped state can be updated without turning off
456 * interrupts because it is not modified via interrupt.
458 __inc_page_state(nr_mapped);
462 * page_add_anon_rmap - add pte mapping to an anonymous page
463 * @page: the page to add the mapping to
464 * @vma: the vm area in which the mapping is added
465 * @address: the user virtual address mapped
467 * The caller needs to hold the pte lock.
469 void page_add_anon_rmap(struct page *page,
470 struct vm_area_struct *vma, unsigned long address)
472 if (atomic_inc_and_test(&page->_mapcount))
473 __page_set_anon_rmap(page, vma, address);
474 /* else checking page index and mapping is racy */
478 * page_add_new_anon_rmap - add pte mapping to a new anonymous page
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 * Same as page_add_anon_rmap but must only be called on *new* pages.
484 * This means the inc-and-test can be bypassed.
486 void page_add_new_anon_rmap(struct page *page,
487 struct vm_area_struct *vma, unsigned long address)
489 atomic_set(&page->_mapcount, 0); /* elevate count by 1 (starts at -1) */
490 __page_set_anon_rmap(page, vma, address);
494 * page_add_file_rmap - add pte mapping to a file page
495 * @page: the page to add the mapping to
497 * The caller needs to hold the pte lock.
499 void page_add_file_rmap(struct page *page)
501 BUG_ON(PageAnon(page));
502 BUG_ON(!pfn_valid(page_to_pfn(page)));
504 if (atomic_inc_and_test(&page->_mapcount))
505 __inc_page_state(nr_mapped);
509 * page_remove_rmap - take down pte mapping from a page
510 * @page: page to remove mapping from
512 * The caller needs to hold the pte lock.
514 void page_remove_rmap(struct page *page)
516 if (atomic_add_negative(-1, &page->_mapcount)) {
517 if (page_mapcount(page) < 0) {
518 printk (KERN_EMERG "Eeek! page_mapcount(page) went negative! (%d)\n", page_mapcount(page));
519 printk (KERN_EMERG " page->flags = %lx\n", page->flags);
520 printk (KERN_EMERG " page->count = %x\n", page_count(page));
521 printk (KERN_EMERG " page->mapping = %p\n", page->mapping);
524 BUG_ON(page_mapcount(page) < 0);
526 * It would be tidy to reset the PageAnon mapping here,
527 * but that might overwrite a racing page_add_anon_rmap
528 * which increments mapcount after us but sets mapping
529 * before us: so leave the reset to free_hot_cold_page,
530 * and remember that it's only reliable while mapped.
531 * Leaving it set also helps swapoff to reinstate ptes
532 * faster for those pages still in swapcache.
534 if (page_test_and_clear_dirty(page))
535 set_page_dirty(page);
536 __dec_page_state(nr_mapped);
541 * Subfunctions of try_to_unmap: try_to_unmap_one called
542 * repeatedly from either try_to_unmap_anon or try_to_unmap_file.
544 static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma)
546 struct mm_struct *mm = vma->vm_mm;
547 unsigned long address;
548 pte_t *pte;
549 pte_t pteval;
550 spinlock_t *ptl;
551 int ret = SWAP_AGAIN;
553 address = vma_address(page, vma);
554 if (address == -EFAULT)
555 goto out;
557 pte = page_check_address(page, mm, address, &ptl);
558 if (!pte)
559 goto out;
562 * If the page is mlock()d, we cannot swap it out.
563 * If it's recently referenced (perhaps page_referenced
564 * skipped over this mm) then we should reactivate it.
566 if ((vma->vm_flags & VM_LOCKED) ||
567 ptep_clear_flush_young(vma, address, pte)) {
568 ret = SWAP_FAIL;
569 goto out_unmap;
572 /* Nuke the page table entry. */
573 flush_cache_page(vma, address, page_to_pfn(page));
574 pteval = ptep_clear_flush(vma, address, pte);
576 /* Move the dirty bit to the physical page now the pte is gone. */
577 if (pte_dirty(pteval))
578 set_page_dirty(page);
580 /* Update high watermark before we lower rss */
581 update_hiwater_rss(mm);
583 if (PageAnon(page)) {
584 swp_entry_t entry = { .val = page_private(page) };
586 * Store the swap location in the pte.
587 * See handle_pte_fault() ...
589 BUG_ON(!PageSwapCache(page));
590 swap_duplicate(entry);
591 if (list_empty(&mm->mmlist)) {
592 spin_lock(&mmlist_lock);
593 if (list_empty(&mm->mmlist))
594 list_add(&mm->mmlist, &init_mm.mmlist);
595 spin_unlock(&mmlist_lock);
597 set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
598 BUG_ON(pte_file(*pte));
599 dec_mm_counter(mm, anon_rss);
600 } else
601 dec_mm_counter(mm, file_rss);
603 page_remove_rmap(page);
604 page_cache_release(page);
606 out_unmap:
607 pte_unmap_unlock(pte, ptl);
608 out:
609 return ret;
613 * objrmap doesn't work for nonlinear VMAs because the assumption that
614 * offset-into-file correlates with offset-into-virtual-addresses does not hold.
615 * Consequently, given a particular page and its ->index, we cannot locate the
616 * ptes which are mapping that page without an exhaustive linear search.
618 * So what this code does is a mini "virtual scan" of each nonlinear VMA which
619 * maps the file to which the target page belongs. The ->vm_private_data field
620 * holds the current cursor into that scan. Successive searches will circulate
621 * around the vma's virtual address space.
623 * So as more replacement pressure is applied to the pages in a nonlinear VMA,
624 * more scanning pressure is placed against them as well. Eventually pages
625 * will become fully unmapped and are eligible for eviction.
627 * For very sparsely populated VMAs this is a little inefficient - chances are
628 * there there won't be many ptes located within the scan cluster. In this case
629 * maybe we could scan further - to the end of the pte page, perhaps.
631 #define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE)
632 #define CLUSTER_MASK (~(CLUSTER_SIZE - 1))
634 static void try_to_unmap_cluster(unsigned long cursor,
635 unsigned int *mapcount, struct vm_area_struct *vma)
637 struct mm_struct *mm = vma->vm_mm;
638 pgd_t *pgd;
639 pud_t *pud;
640 pmd_t *pmd;
641 pte_t *pte;
642 pte_t pteval;
643 spinlock_t *ptl;
644 struct page *page;
645 unsigned long address;
646 unsigned long end;
648 address = (vma->vm_start + cursor) & CLUSTER_MASK;
649 end = address + CLUSTER_SIZE;
650 if (address < vma->vm_start)
651 address = vma->vm_start;
652 if (end > vma->vm_end)
653 end = vma->vm_end;
655 pgd = pgd_offset(mm, address);
656 if (!pgd_present(*pgd))
657 return;
659 pud = pud_offset(pgd, address);
660 if (!pud_present(*pud))
661 return;
663 pmd = pmd_offset(pud, address);
664 if (!pmd_present(*pmd))
665 return;
667 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
669 /* Update high watermark before we lower rss */
670 update_hiwater_rss(mm);
672 for (; address < end; pte++, address += PAGE_SIZE) {
673 if (!pte_present(*pte))
674 continue;
675 page = vm_normal_page(vma, address, *pte);
676 BUG_ON(!page || PageAnon(page));
678 if (ptep_clear_flush_young(vma, address, pte))
679 continue;
681 /* Nuke the page table entry. */
682 flush_cache_page(vma, address, pte_pfn(*pte));
683 pteval = ptep_clear_flush(vma, address, pte);
685 /* If nonlinear, store the file page offset in the pte. */
686 if (page->index != linear_page_index(vma, address))
687 set_pte_at(mm, address, pte, pgoff_to_pte(page->index));
689 /* Move the dirty bit to the physical page now the pte is gone. */
690 if (pte_dirty(pteval))
691 set_page_dirty(page);
693 page_remove_rmap(page);
694 page_cache_release(page);
695 dec_mm_counter(mm, file_rss);
696 (*mapcount)--;
698 pte_unmap_unlock(pte - 1, ptl);
701 static int try_to_unmap_anon(struct page *page)
703 struct anon_vma *anon_vma;
704 struct vm_area_struct *vma;
705 int ret = SWAP_AGAIN;
707 anon_vma = page_lock_anon_vma(page);
708 if (!anon_vma)
709 return ret;
711 list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
712 ret = try_to_unmap_one(page, vma);
713 if (ret == SWAP_FAIL || !page_mapped(page))
714 break;
716 spin_unlock(&anon_vma->lock);
717 return ret;
721 * try_to_unmap_file - unmap file page using the object-based rmap method
722 * @page: the page to unmap
724 * Find all the mappings of a page using the mapping pointer and the vma chains
725 * contained in the address_space struct it points to.
727 * This function is only called from try_to_unmap for object-based pages.
729 static int try_to_unmap_file(struct page *page)
731 struct address_space *mapping = page->mapping;
732 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
733 struct vm_area_struct *vma;
734 struct prio_tree_iter iter;
735 int ret = SWAP_AGAIN;
736 unsigned long cursor;
737 unsigned long max_nl_cursor = 0;
738 unsigned long max_nl_size = 0;
739 unsigned int mapcount;
741 spin_lock(&mapping->i_mmap_lock);
742 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
743 ret = try_to_unmap_one(page, vma);
744 if (ret == SWAP_FAIL || !page_mapped(page))
745 goto out;
748 if (list_empty(&mapping->i_mmap_nonlinear))
749 goto out;
751 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
752 shared.vm_set.list) {
753 if (vma->vm_flags & VM_LOCKED)
754 continue;
755 cursor = (unsigned long) vma->vm_private_data;
756 if (cursor > max_nl_cursor)
757 max_nl_cursor = cursor;
758 cursor = vma->vm_end - vma->vm_start;
759 if (cursor > max_nl_size)
760 max_nl_size = cursor;
763 if (max_nl_size == 0) { /* any nonlinears locked or reserved */
764 ret = SWAP_FAIL;
765 goto out;
769 * We don't try to search for this page in the nonlinear vmas,
770 * and page_referenced wouldn't have found it anyway. Instead
771 * just walk the nonlinear vmas trying to age and unmap some.
772 * The mapcount of the page we came in with is irrelevant,
773 * but even so use it as a guide to how hard we should try?
775 mapcount = page_mapcount(page);
776 if (!mapcount)
777 goto out;
778 cond_resched_lock(&mapping->i_mmap_lock);
780 max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK;
781 if (max_nl_cursor == 0)
782 max_nl_cursor = CLUSTER_SIZE;
784 do {
785 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
786 shared.vm_set.list) {
787 if (vma->vm_flags & VM_LOCKED)
788 continue;
789 cursor = (unsigned long) vma->vm_private_data;
790 while ( cursor < max_nl_cursor &&
791 cursor < vma->vm_end - vma->vm_start) {
792 try_to_unmap_cluster(cursor, &mapcount, vma);
793 cursor += CLUSTER_SIZE;
794 vma->vm_private_data = (void *) cursor;
795 if ((int)mapcount <= 0)
796 goto out;
798 vma->vm_private_data = (void *) max_nl_cursor;
800 cond_resched_lock(&mapping->i_mmap_lock);
801 max_nl_cursor += CLUSTER_SIZE;
802 } while (max_nl_cursor <= max_nl_size);
805 * Don't loop forever (perhaps all the remaining pages are
806 * in locked vmas). Reset cursor on all unreserved nonlinear
807 * vmas, now forgetting on which ones it had fallen behind.
809 list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list)
810 vma->vm_private_data = NULL;
811 out:
812 spin_unlock(&mapping->i_mmap_lock);
813 return ret;
817 * try_to_unmap - try to remove all page table mappings to a page
818 * @page: the page to get unmapped
820 * Tries to remove all the page table entries which are mapping this
821 * page, used in the pageout path. Caller must hold the page lock.
822 * Return values are:
824 * SWAP_SUCCESS - we succeeded in removing all mappings
825 * SWAP_AGAIN - we missed a mapping, try again later
826 * SWAP_FAIL - the page is unswappable
828 int try_to_unmap(struct page *page)
830 int ret;
832 BUG_ON(!PageLocked(page));
834 if (PageAnon(page))
835 ret = try_to_unmap_anon(page);
836 else
837 ret = try_to_unmap_file(page);
839 if (!page_mapped(page))
840 ret = SWAP_SUCCESS;
841 return ret;