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 (vmtruncate_range)
26 * page->flags PG_locked (lock_page)
27 * mapping->i_mmap_lock
29 * mm->page_table_lock or pte_lock
30 * zone->lru_lock (in mark_page_accessed, isolate_lru_page)
31 * swap_lock (in swap_duplicate, swap_info_get)
32 * mmlist_lock (in mmput, drain_mmlist and others)
33 * mapping->private_lock (in __set_page_dirty_buffers)
34 * inode_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 inode_lock in __sync_single_inode)
42 #include <linux/pagemap.h>
43 #include <linux/swap.h>
44 #include <linux/swapops.h>
45 #include <linux/slab.h>
46 #include <linux/init.h>
47 #include <linux/rmap.h>
48 #include <linux/rcupdate.h>
49 #include <linux/module.h>
50 #include <linux/kallsyms.h>
51 #include <linux/memcontrol.h>
52 #include <linux/mmu_notifier.h>
53 #include <linux/migrate.h>
55 #include <asm/tlbflush.h>
59 static struct kmem_cache
*anon_vma_cachep
;
61 static inline struct anon_vma
*anon_vma_alloc(void)
63 return kmem_cache_alloc(anon_vma_cachep
, GFP_KERNEL
);
66 static inline void anon_vma_free(struct anon_vma
*anon_vma
)
68 kmem_cache_free(anon_vma_cachep
, anon_vma
);
72 * anon_vma_prepare - attach an anon_vma to a memory region
73 * @vma: the memory region in question
75 * This makes sure the memory mapping described by 'vma' has
76 * an 'anon_vma' attached to it, so that we can associate the
77 * anonymous pages mapped into it with that anon_vma.
79 * The common case will be that we already have one, but if
80 * if not we either need to find an adjacent mapping that we
81 * can re-use the anon_vma from (very common when the only
82 * reason for splitting a vma has been mprotect()), or we
85 * Anon-vma allocations are very subtle, because we may have
86 * optimistically looked up an anon_vma in page_lock_anon_vma()
87 * and that may actually touch the spinlock even in the newly
88 * allocated vma (it depends on RCU to make sure that the
89 * anon_vma isn't actually destroyed).
91 * As a result, we need to do proper anon_vma locking even
92 * for the new allocation. At the same time, we do not want
93 * to do any locking for the common case of already having
96 * This must be called with the mmap_sem held for reading.
98 int anon_vma_prepare(struct vm_area_struct
*vma
)
100 struct anon_vma
*anon_vma
= vma
->anon_vma
;
103 if (unlikely(!anon_vma
)) {
104 struct mm_struct
*mm
= vma
->vm_mm
;
105 struct anon_vma
*allocated
;
107 anon_vma
= find_mergeable_anon_vma(vma
);
110 anon_vma
= anon_vma_alloc();
111 if (unlikely(!anon_vma
))
113 allocated
= anon_vma
;
115 spin_lock(&anon_vma
->lock
);
117 /* page_table_lock to protect against threads */
118 spin_lock(&mm
->page_table_lock
);
119 if (likely(!vma
->anon_vma
)) {
120 vma
->anon_vma
= anon_vma
;
121 list_add_tail(&vma
->anon_vma_node
, &anon_vma
->head
);
124 spin_unlock(&mm
->page_table_lock
);
126 spin_unlock(&anon_vma
->lock
);
127 if (unlikely(allocated
))
128 anon_vma_free(allocated
);
133 void __anon_vma_merge(struct vm_area_struct
*vma
, struct vm_area_struct
*next
)
135 BUG_ON(vma
->anon_vma
!= next
->anon_vma
);
136 list_del(&next
->anon_vma_node
);
139 void __anon_vma_link(struct vm_area_struct
*vma
)
141 struct anon_vma
*anon_vma
= vma
->anon_vma
;
144 list_add_tail(&vma
->anon_vma_node
, &anon_vma
->head
);
147 void anon_vma_link(struct vm_area_struct
*vma
)
149 struct anon_vma
*anon_vma
= vma
->anon_vma
;
152 spin_lock(&anon_vma
->lock
);
153 list_add_tail(&vma
->anon_vma_node
, &anon_vma
->head
);
154 spin_unlock(&anon_vma
->lock
);
158 void anon_vma_unlink(struct vm_area_struct
*vma
)
160 struct anon_vma
*anon_vma
= vma
->anon_vma
;
166 spin_lock(&anon_vma
->lock
);
167 list_del(&vma
->anon_vma_node
);
169 /* We must garbage collect the anon_vma if it's empty */
170 empty
= list_empty(&anon_vma
->head
);
171 spin_unlock(&anon_vma
->lock
);
174 anon_vma_free(anon_vma
);
177 static void anon_vma_ctor(void *data
)
179 struct anon_vma
*anon_vma
= data
;
181 spin_lock_init(&anon_vma
->lock
);
182 INIT_LIST_HEAD(&anon_vma
->head
);
185 void __init
anon_vma_init(void)
187 anon_vma_cachep
= kmem_cache_create("anon_vma", sizeof(struct anon_vma
),
188 0, SLAB_DESTROY_BY_RCU
|SLAB_PANIC
, anon_vma_ctor
);
192 * Getting a lock on a stable anon_vma from a page off the LRU is
193 * tricky: page_lock_anon_vma rely on RCU to guard against the races.
195 struct anon_vma
*page_lock_anon_vma(struct page
*page
)
197 struct anon_vma
*anon_vma
;
198 unsigned long anon_mapping
;
201 anon_mapping
= (unsigned long) page
->mapping
;
202 if (!(anon_mapping
& PAGE_MAPPING_ANON
))
204 if (!page_mapped(page
))
207 anon_vma
= (struct anon_vma
*) (anon_mapping
- PAGE_MAPPING_ANON
);
208 spin_lock(&anon_vma
->lock
);
215 void page_unlock_anon_vma(struct anon_vma
*anon_vma
)
217 spin_unlock(&anon_vma
->lock
);
222 * At what user virtual address is page expected in @vma?
223 * Returns virtual address or -EFAULT if page's index/offset is not
224 * within the range mapped the @vma.
226 static inline unsigned long
227 vma_address(struct page
*page
, struct vm_area_struct
*vma
)
229 pgoff_t pgoff
= page
->index
<< (PAGE_CACHE_SHIFT
- PAGE_SHIFT
);
230 unsigned long address
;
232 address
= vma
->vm_start
+ ((pgoff
- vma
->vm_pgoff
) << PAGE_SHIFT
);
233 if (unlikely(address
< vma
->vm_start
|| address
>= vma
->vm_end
)) {
234 /* page should be within @vma mapping range */
241 * At what user virtual address is page expected in vma? checking that the
242 * page matches the vma: currently only used on anon pages, by unuse_vma;
244 unsigned long page_address_in_vma(struct page
*page
, struct vm_area_struct
*vma
)
246 if (PageAnon(page
)) {
247 if ((void *)vma
->anon_vma
!=
248 (void *)page
->mapping
- PAGE_MAPPING_ANON
)
250 } else if (page
->mapping
&& !(vma
->vm_flags
& VM_NONLINEAR
)) {
252 vma
->vm_file
->f_mapping
!= page
->mapping
)
256 return vma_address(page
, vma
);
260 * Check that @page is mapped at @address into @mm.
262 * If @sync is false, page_check_address may perform a racy check to avoid
263 * the page table lock when the pte is not present (helpful when reclaiming
264 * highly shared pages).
266 * On success returns with pte mapped and locked.
268 pte_t
*page_check_address(struct page
*page
, struct mm_struct
*mm
,
269 unsigned long address
, spinlock_t
**ptlp
, int sync
)
277 pgd
= pgd_offset(mm
, address
);
278 if (!pgd_present(*pgd
))
281 pud
= pud_offset(pgd
, address
);
282 if (!pud_present(*pud
))
285 pmd
= pmd_offset(pud
, address
);
286 if (!pmd_present(*pmd
))
289 pte
= pte_offset_map(pmd
, address
);
290 /* Make a quick check before getting the lock */
291 if (!sync
&& !pte_present(*pte
)) {
296 ptl
= pte_lockptr(mm
, pmd
);
298 if (pte_present(*pte
) && page_to_pfn(page
) == pte_pfn(*pte
)) {
302 pte_unmap_unlock(pte
, ptl
);
307 * page_mapped_in_vma - check whether a page is really mapped in a VMA
308 * @page: the page to test
309 * @vma: the VMA to test
311 * Returns 1 if the page is mapped into the page tables of the VMA, 0
312 * if the page is not mapped into the page tables of this VMA. Only
313 * valid for normal file or anonymous VMAs.
315 static int page_mapped_in_vma(struct page
*page
, struct vm_area_struct
*vma
)
317 unsigned long address
;
321 address
= vma_address(page
, vma
);
322 if (address
== -EFAULT
) /* out of vma range */
324 pte
= page_check_address(page
, vma
->vm_mm
, address
, &ptl
, 1);
325 if (!pte
) /* the page is not in this mm */
327 pte_unmap_unlock(pte
, ptl
);
333 * Subfunctions of page_referenced: page_referenced_one called
334 * repeatedly from either page_referenced_anon or page_referenced_file.
336 static int page_referenced_one(struct page
*page
,
337 struct vm_area_struct
*vma
, unsigned int *mapcount
)
339 struct mm_struct
*mm
= vma
->vm_mm
;
340 unsigned long address
;
345 address
= vma_address(page
, vma
);
346 if (address
== -EFAULT
)
349 pte
= page_check_address(page
, mm
, address
, &ptl
, 0);
354 * Don't want to elevate referenced for mlocked page that gets this far,
355 * in order that it progresses to try_to_unmap and is moved to the
358 if (vma
->vm_flags
& VM_LOCKED
) {
359 *mapcount
= 1; /* break early from loop */
363 if (ptep_clear_flush_young_notify(vma
, address
, pte
)) {
365 * Don't treat a reference through a sequentially read
366 * mapping as such. If the page has been used in
367 * another mapping, we will catch it; if this other
368 * mapping is already gone, the unmap path will have
369 * set PG_referenced or activated the page.
371 if (likely(!VM_SequentialReadHint(vma
)))
375 /* Pretend the page is referenced if the task has the
376 swap token and is in the middle of a page fault. */
377 if (mm
!= current
->mm
&& has_swap_token(mm
) &&
378 rwsem_is_locked(&mm
->mmap_sem
))
383 pte_unmap_unlock(pte
, ptl
);
388 static int page_referenced_anon(struct page
*page
,
389 struct mem_cgroup
*mem_cont
)
391 unsigned int mapcount
;
392 struct anon_vma
*anon_vma
;
393 struct vm_area_struct
*vma
;
396 anon_vma
= page_lock_anon_vma(page
);
400 mapcount
= page_mapcount(page
);
401 list_for_each_entry(vma
, &anon_vma
->head
, anon_vma_node
) {
403 * If we are reclaiming on behalf of a cgroup, skip
404 * counting on behalf of references from different
407 if (mem_cont
&& !mm_match_cgroup(vma
->vm_mm
, mem_cont
))
409 referenced
+= page_referenced_one(page
, vma
, &mapcount
);
414 page_unlock_anon_vma(anon_vma
);
419 * page_referenced_file - referenced check for object-based rmap
420 * @page: the page we're checking references on.
421 * @mem_cont: target memory controller
423 * For an object-based mapped page, find all the places it is mapped and
424 * check/clear the referenced flag. This is done by following the page->mapping
425 * pointer, then walking the chain of vmas it holds. It returns the number
426 * of references it found.
428 * This function is only called from page_referenced for object-based pages.
430 static int page_referenced_file(struct page
*page
,
431 struct mem_cgroup
*mem_cont
)
433 unsigned int mapcount
;
434 struct address_space
*mapping
= page
->mapping
;
435 pgoff_t pgoff
= page
->index
<< (PAGE_CACHE_SHIFT
- PAGE_SHIFT
);
436 struct vm_area_struct
*vma
;
437 struct prio_tree_iter iter
;
441 * The caller's checks on page->mapping and !PageAnon have made
442 * sure that this is a file page: the check for page->mapping
443 * excludes the case just before it gets set on an anon page.
445 BUG_ON(PageAnon(page
));
448 * The page lock not only makes sure that page->mapping cannot
449 * suddenly be NULLified by truncation, it makes sure that the
450 * structure at mapping cannot be freed and reused yet,
451 * so we can safely take mapping->i_mmap_lock.
453 BUG_ON(!PageLocked(page
));
455 spin_lock(&mapping
->i_mmap_lock
);
458 * i_mmap_lock does not stabilize mapcount at all, but mapcount
459 * is more likely to be accurate if we note it after spinning.
461 mapcount
= page_mapcount(page
);
463 vma_prio_tree_foreach(vma
, &iter
, &mapping
->i_mmap
, pgoff
, pgoff
) {
465 * If we are reclaiming on behalf of a cgroup, skip
466 * counting on behalf of references from different
469 if (mem_cont
&& !mm_match_cgroup(vma
->vm_mm
, mem_cont
))
471 referenced
+= page_referenced_one(page
, vma
, &mapcount
);
476 spin_unlock(&mapping
->i_mmap_lock
);
481 * page_referenced - test if the page was referenced
482 * @page: the page to test
483 * @is_locked: caller holds lock on the page
484 * @mem_cont: target memory controller
486 * Quick test_and_clear_referenced for all mappings to a page,
487 * returns the number of ptes which referenced the page.
489 int page_referenced(struct page
*page
, int is_locked
,
490 struct mem_cgroup
*mem_cont
)
494 if (TestClearPageReferenced(page
))
497 if (page_mapped(page
) && page
->mapping
) {
499 referenced
+= page_referenced_anon(page
, mem_cont
);
501 referenced
+= page_referenced_file(page
, mem_cont
);
502 else if (!trylock_page(page
))
507 page_referenced_file(page
, mem_cont
);
512 if (page_test_and_clear_young(page
))
518 static int page_mkclean_one(struct page
*page
, struct vm_area_struct
*vma
)
520 struct mm_struct
*mm
= vma
->vm_mm
;
521 unsigned long address
;
526 address
= vma_address(page
, vma
);
527 if (address
== -EFAULT
)
530 pte
= page_check_address(page
, mm
, address
, &ptl
, 1);
534 if (pte_dirty(*pte
) || pte_write(*pte
)) {
537 flush_cache_page(vma
, address
, pte_pfn(*pte
));
538 entry
= ptep_clear_flush_notify(vma
, address
, pte
);
539 entry
= pte_wrprotect(entry
);
540 entry
= pte_mkclean(entry
);
541 set_pte_at(mm
, address
, pte
, entry
);
545 pte_unmap_unlock(pte
, ptl
);
550 static int page_mkclean_file(struct address_space
*mapping
, struct page
*page
)
552 pgoff_t pgoff
= page
->index
<< (PAGE_CACHE_SHIFT
- PAGE_SHIFT
);
553 struct vm_area_struct
*vma
;
554 struct prio_tree_iter iter
;
557 BUG_ON(PageAnon(page
));
559 spin_lock(&mapping
->i_mmap_lock
);
560 vma_prio_tree_foreach(vma
, &iter
, &mapping
->i_mmap
, pgoff
, pgoff
) {
561 if (vma
->vm_flags
& VM_SHARED
)
562 ret
+= page_mkclean_one(page
, vma
);
564 spin_unlock(&mapping
->i_mmap_lock
);
568 int page_mkclean(struct page
*page
)
572 BUG_ON(!PageLocked(page
));
574 if (page_mapped(page
)) {
575 struct address_space
*mapping
= page_mapping(page
);
577 ret
= page_mkclean_file(mapping
, page
);
578 if (page_test_dirty(page
)) {
579 page_clear_dirty(page
);
587 EXPORT_SYMBOL_GPL(page_mkclean
);
590 * __page_set_anon_rmap - setup new anonymous rmap
591 * @page: the page to add the mapping to
592 * @vma: the vm area in which the mapping is added
593 * @address: the user virtual address mapped
595 static void __page_set_anon_rmap(struct page
*page
,
596 struct vm_area_struct
*vma
, unsigned long address
)
598 struct anon_vma
*anon_vma
= vma
->anon_vma
;
601 anon_vma
= (void *) anon_vma
+ PAGE_MAPPING_ANON
;
602 page
->mapping
= (struct address_space
*) anon_vma
;
604 page
->index
= linear_page_index(vma
, address
);
607 * nr_mapped state can be updated without turning off
608 * interrupts because it is not modified via interrupt.
610 __inc_zone_page_state(page
, NR_ANON_PAGES
);
614 * __page_check_anon_rmap - sanity check anonymous rmap addition
615 * @page: the page to add the mapping to
616 * @vma: the vm area in which the mapping is added
617 * @address: the user virtual address mapped
619 static void __page_check_anon_rmap(struct page
*page
,
620 struct vm_area_struct
*vma
, unsigned long address
)
622 #ifdef CONFIG_DEBUG_VM
624 * The page's anon-rmap details (mapping and index) are guaranteed to
625 * be set up correctly at this point.
627 * We have exclusion against page_add_anon_rmap because the caller
628 * always holds the page locked, except if called from page_dup_rmap,
629 * in which case the page is already known to be setup.
631 * We have exclusion against page_add_new_anon_rmap because those pages
632 * are initially only visible via the pagetables, and the pte is locked
633 * over the call to page_add_new_anon_rmap.
635 struct anon_vma
*anon_vma
= vma
->anon_vma
;
636 anon_vma
= (void *) anon_vma
+ PAGE_MAPPING_ANON
;
637 BUG_ON(page
->mapping
!= (struct address_space
*)anon_vma
);
638 BUG_ON(page
->index
!= linear_page_index(vma
, address
));
643 * page_add_anon_rmap - add pte mapping to an anonymous page
644 * @page: the page to add the mapping to
645 * @vma: the vm area in which the mapping is added
646 * @address: the user virtual address mapped
648 * The caller needs to hold the pte lock and the page must be locked.
650 void page_add_anon_rmap(struct page
*page
,
651 struct vm_area_struct
*vma
, unsigned long address
)
653 VM_BUG_ON(!PageLocked(page
));
654 VM_BUG_ON(address
< vma
->vm_start
|| address
>= vma
->vm_end
);
655 if (atomic_inc_and_test(&page
->_mapcount
))
656 __page_set_anon_rmap(page
, vma
, address
);
658 __page_check_anon_rmap(page
, vma
, address
);
662 * page_add_new_anon_rmap - add pte mapping to a new anonymous page
663 * @page: the page to add the mapping to
664 * @vma: the vm area in which the mapping is added
665 * @address: the user virtual address mapped
667 * Same as page_add_anon_rmap but must only be called on *new* pages.
668 * This means the inc-and-test can be bypassed.
669 * Page does not have to be locked.
671 void page_add_new_anon_rmap(struct page
*page
,
672 struct vm_area_struct
*vma
, unsigned long address
)
674 BUG_ON(address
< vma
->vm_start
|| address
>= vma
->vm_end
);
675 atomic_set(&page
->_mapcount
, 0); /* elevate count by 1 (starts at -1) */
676 __page_set_anon_rmap(page
, vma
, address
);
680 * page_add_file_rmap - add pte mapping to a file page
681 * @page: the page to add the mapping to
683 * The caller needs to hold the pte lock.
685 void page_add_file_rmap(struct page
*page
)
687 if (atomic_inc_and_test(&page
->_mapcount
))
688 __inc_zone_page_state(page
, NR_FILE_MAPPED
);
691 #ifdef CONFIG_DEBUG_VM
693 * page_dup_rmap - duplicate pte mapping to a page
694 * @page: the page to add the mapping to
695 * @vma: the vm area being duplicated
696 * @address: the user virtual address mapped
698 * For copy_page_range only: minimal extract from page_add_file_rmap /
699 * page_add_anon_rmap, avoiding unnecessary tests (already checked) so it's
702 * The caller needs to hold the pte lock.
704 void page_dup_rmap(struct page
*page
, struct vm_area_struct
*vma
, unsigned long address
)
706 BUG_ON(page_mapcount(page
) == 0);
708 __page_check_anon_rmap(page
, vma
, address
);
709 atomic_inc(&page
->_mapcount
);
714 * page_remove_rmap - take down pte mapping from a page
715 * @page: page to remove mapping from
716 * @vma: the vm area in which the mapping is removed
718 * The caller needs to hold the pte lock.
720 void page_remove_rmap(struct page
*page
, struct vm_area_struct
*vma
)
722 if (atomic_add_negative(-1, &page
->_mapcount
)) {
723 if (unlikely(page_mapcount(page
) < 0)) {
724 printk (KERN_EMERG
"Eeek! page_mapcount(page) went negative! (%d)\n", page_mapcount(page
));
725 printk (KERN_EMERG
" page pfn = %lx\n", page_to_pfn(page
));
726 printk (KERN_EMERG
" page->flags = %lx\n", page
->flags
);
727 printk (KERN_EMERG
" page->count = %x\n", page_count(page
));
728 printk (KERN_EMERG
" page->mapping = %p\n", page
->mapping
);
729 print_symbol (KERN_EMERG
" vma->vm_ops = %s\n", (unsigned long)vma
->vm_ops
);
731 print_symbol (KERN_EMERG
" vma->vm_ops->fault = %s\n", (unsigned long)vma
->vm_ops
->fault
);
733 if (vma
->vm_file
&& vma
->vm_file
->f_op
)
734 print_symbol (KERN_EMERG
" vma->vm_file->f_op->mmap = %s\n", (unsigned long)vma
->vm_file
->f_op
->mmap
);
739 * Now that the last pte has gone, s390 must transfer dirty
740 * flag from storage key to struct page. We can usually skip
741 * this if the page is anon, so about to be freed; but perhaps
742 * not if it's in swapcache - there might be another pte slot
743 * containing the swap entry, but page not yet written to swap.
745 if ((!PageAnon(page
) || PageSwapCache(page
)) &&
746 page_test_dirty(page
)) {
747 page_clear_dirty(page
);
748 set_page_dirty(page
);
751 mem_cgroup_uncharge_page(page
);
752 __dec_zone_page_state(page
,
753 PageAnon(page
) ? NR_ANON_PAGES
: NR_FILE_MAPPED
);
755 * It would be tidy to reset the PageAnon mapping here,
756 * but that might overwrite a racing page_add_anon_rmap
757 * which increments mapcount after us but sets mapping
758 * before us: so leave the reset to free_hot_cold_page,
759 * and remember that it's only reliable while mapped.
760 * Leaving it set also helps swapoff to reinstate ptes
761 * faster for those pages still in swapcache.
767 * Subfunctions of try_to_unmap: try_to_unmap_one called
768 * repeatedly from either try_to_unmap_anon or try_to_unmap_file.
770 static int try_to_unmap_one(struct page
*page
, struct vm_area_struct
*vma
,
773 struct mm_struct
*mm
= vma
->vm_mm
;
774 unsigned long address
;
778 int ret
= SWAP_AGAIN
;
780 address
= vma_address(page
, vma
);
781 if (address
== -EFAULT
)
784 pte
= page_check_address(page
, mm
, address
, &ptl
, 0);
789 * If the page is mlock()d, we cannot swap it out.
790 * If it's recently referenced (perhaps page_referenced
791 * skipped over this mm) then we should reactivate it.
794 if (vma
->vm_flags
& VM_LOCKED
) {
798 if (ptep_clear_flush_young_notify(vma
, address
, pte
)) {
804 /* Nuke the page table entry. */
805 flush_cache_page(vma
, address
, page_to_pfn(page
));
806 pteval
= ptep_clear_flush_notify(vma
, address
, pte
);
808 /* Move the dirty bit to the physical page now the pte is gone. */
809 if (pte_dirty(pteval
))
810 set_page_dirty(page
);
812 /* Update high watermark before we lower rss */
813 update_hiwater_rss(mm
);
815 if (PageAnon(page
)) {
816 swp_entry_t entry
= { .val
= page_private(page
) };
818 if (PageSwapCache(page
)) {
820 * Store the swap location in the pte.
821 * See handle_pte_fault() ...
823 swap_duplicate(entry
);
824 if (list_empty(&mm
->mmlist
)) {
825 spin_lock(&mmlist_lock
);
826 if (list_empty(&mm
->mmlist
))
827 list_add(&mm
->mmlist
, &init_mm
.mmlist
);
828 spin_unlock(&mmlist_lock
);
830 dec_mm_counter(mm
, anon_rss
);
831 } else if (PAGE_MIGRATION
) {
833 * Store the pfn of the page in a special migration
834 * pte. do_swap_page() will wait until the migration
835 * pte is removed and then restart fault handling.
838 entry
= make_migration_entry(page
, pte_write(pteval
));
840 set_pte_at(mm
, address
, pte
, swp_entry_to_pte(entry
));
841 BUG_ON(pte_file(*pte
));
842 } else if (PAGE_MIGRATION
&& migration
) {
843 /* Establish migration entry for a file page */
845 entry
= make_migration_entry(page
, pte_write(pteval
));
846 set_pte_at(mm
, address
, pte
, swp_entry_to_pte(entry
));
848 dec_mm_counter(mm
, file_rss
);
851 page_remove_rmap(page
, vma
);
852 page_cache_release(page
);
855 pte_unmap_unlock(pte
, ptl
);
861 * objrmap doesn't work for nonlinear VMAs because the assumption that
862 * offset-into-file correlates with offset-into-virtual-addresses does not hold.
863 * Consequently, given a particular page and its ->index, we cannot locate the
864 * ptes which are mapping that page without an exhaustive linear search.
866 * So what this code does is a mini "virtual scan" of each nonlinear VMA which
867 * maps the file to which the target page belongs. The ->vm_private_data field
868 * holds the current cursor into that scan. Successive searches will circulate
869 * around the vma's virtual address space.
871 * So as more replacement pressure is applied to the pages in a nonlinear VMA,
872 * more scanning pressure is placed against them as well. Eventually pages
873 * will become fully unmapped and are eligible for eviction.
875 * For very sparsely populated VMAs this is a little inefficient - chances are
876 * there there won't be many ptes located within the scan cluster. In this case
877 * maybe we could scan further - to the end of the pte page, perhaps.
879 * Mlocked pages: check VM_LOCKED under mmap_sem held for read, if we can
880 * acquire it without blocking. If vma locked, mlock the pages in the cluster,
881 * rather than unmapping them. If we encounter the "check_page" that vmscan is
882 * trying to unmap, return SWAP_MLOCK, else default SWAP_AGAIN.
884 #define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE)
885 #define CLUSTER_MASK (~(CLUSTER_SIZE - 1))
887 static int try_to_unmap_cluster(unsigned long cursor
, unsigned int *mapcount
,
888 struct vm_area_struct
*vma
, struct page
*check_page
)
890 struct mm_struct
*mm
= vma
->vm_mm
;
898 unsigned long address
;
900 int ret
= SWAP_AGAIN
;
903 address
= (vma
->vm_start
+ cursor
) & CLUSTER_MASK
;
904 end
= address
+ CLUSTER_SIZE
;
905 if (address
< vma
->vm_start
)
906 address
= vma
->vm_start
;
907 if (end
> vma
->vm_end
)
910 pgd
= pgd_offset(mm
, address
);
911 if (!pgd_present(*pgd
))
914 pud
= pud_offset(pgd
, address
);
915 if (!pud_present(*pud
))
918 pmd
= pmd_offset(pud
, address
);
919 if (!pmd_present(*pmd
))
923 * MLOCK_PAGES => feature is configured.
924 * if we can acquire the mmap_sem for read, and vma is VM_LOCKED,
925 * keep the sem while scanning the cluster for mlocking pages.
927 if (MLOCK_PAGES
&& down_read_trylock(&vma
->vm_mm
->mmap_sem
)) {
928 locked_vma
= (vma
->vm_flags
& VM_LOCKED
);
930 up_read(&vma
->vm_mm
->mmap_sem
); /* don't need it */
933 pte
= pte_offset_map_lock(mm
, pmd
, address
, &ptl
);
935 /* Update high watermark before we lower rss */
936 update_hiwater_rss(mm
);
938 for (; address
< end
; pte
++, address
+= PAGE_SIZE
) {
939 if (!pte_present(*pte
))
941 page
= vm_normal_page(vma
, address
, *pte
);
942 BUG_ON(!page
|| PageAnon(page
));
945 mlock_vma_page(page
); /* no-op if already mlocked */
946 if (page
== check_page
)
948 continue; /* don't unmap */
951 if (ptep_clear_flush_young_notify(vma
, address
, pte
))
954 /* Nuke the page table entry. */
955 flush_cache_page(vma
, address
, pte_pfn(*pte
));
956 pteval
= ptep_clear_flush_notify(vma
, address
, pte
);
958 /* If nonlinear, store the file page offset in the pte. */
959 if (page
->index
!= linear_page_index(vma
, address
))
960 set_pte_at(mm
, address
, pte
, pgoff_to_pte(page
->index
));
962 /* Move the dirty bit to the physical page now the pte is gone. */
963 if (pte_dirty(pteval
))
964 set_page_dirty(page
);
966 page_remove_rmap(page
, vma
);
967 page_cache_release(page
);
968 dec_mm_counter(mm
, file_rss
);
971 pte_unmap_unlock(pte
- 1, ptl
);
973 up_read(&vma
->vm_mm
->mmap_sem
);
978 * common handling for pages mapped in VM_LOCKED vmas
980 static int try_to_mlock_page(struct page
*page
, struct vm_area_struct
*vma
)
984 if (down_read_trylock(&vma
->vm_mm
->mmap_sem
)) {
985 if (vma
->vm_flags
& VM_LOCKED
) {
986 mlock_vma_page(page
);
987 mlocked
++; /* really mlocked the page */
989 up_read(&vma
->vm_mm
->mmap_sem
);
995 * try_to_unmap_anon - unmap or unlock anonymous page using the object-based
997 * @page: the page to unmap/unlock
998 * @unlock: request for unlock rather than unmap [unlikely]
999 * @migration: unmapping for migration - ignored if @unlock
1001 * Find all the mappings of a page using the mapping pointer and the vma chains
1002 * contained in the anon_vma struct it points to.
1004 * This function is only called from try_to_unmap/try_to_munlock for
1006 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1007 * where the page was found will be held for write. So, we won't recheck
1008 * vm_flags for that VMA. That should be OK, because that vma shouldn't be
1011 static int try_to_unmap_anon(struct page
*page
, int unlock
, int migration
)
1013 struct anon_vma
*anon_vma
;
1014 struct vm_area_struct
*vma
;
1015 unsigned int mlocked
= 0;
1016 int ret
= SWAP_AGAIN
;
1018 if (MLOCK_PAGES
&& unlikely(unlock
))
1019 ret
= SWAP_SUCCESS
; /* default for try_to_munlock() */
1021 anon_vma
= page_lock_anon_vma(page
);
1025 list_for_each_entry(vma
, &anon_vma
->head
, anon_vma_node
) {
1026 if (MLOCK_PAGES
&& unlikely(unlock
)) {
1027 if (!((vma
->vm_flags
& VM_LOCKED
) &&
1028 page_mapped_in_vma(page
, vma
)))
1029 continue; /* must visit all unlocked vmas */
1030 ret
= SWAP_MLOCK
; /* saw at least one mlocked vma */
1032 ret
= try_to_unmap_one(page
, vma
, migration
);
1033 if (ret
== SWAP_FAIL
|| !page_mapped(page
))
1036 if (ret
== SWAP_MLOCK
) {
1037 mlocked
= try_to_mlock_page(page
, vma
);
1039 break; /* stop if actually mlocked page */
1043 page_unlock_anon_vma(anon_vma
);
1046 ret
= SWAP_MLOCK
; /* actually mlocked the page */
1047 else if (ret
== SWAP_MLOCK
)
1048 ret
= SWAP_AGAIN
; /* saw VM_LOCKED vma */
1054 * try_to_unmap_file - unmap/unlock file page using the object-based rmap method
1055 * @page: the page to unmap/unlock
1056 * @unlock: request for unlock rather than unmap [unlikely]
1057 * @migration: unmapping for migration - ignored if @unlock
1059 * Find all the mappings of a page using the mapping pointer and the vma chains
1060 * contained in the address_space struct it points to.
1062 * This function is only called from try_to_unmap/try_to_munlock for
1063 * object-based pages.
1064 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1065 * where the page was found will be held for write. So, we won't recheck
1066 * vm_flags for that VMA. That should be OK, because that vma shouldn't be
1069 static int try_to_unmap_file(struct page
*page
, int unlock
, int migration
)
1071 struct address_space
*mapping
= page
->mapping
;
1072 pgoff_t pgoff
= page
->index
<< (PAGE_CACHE_SHIFT
- PAGE_SHIFT
);
1073 struct vm_area_struct
*vma
;
1074 struct prio_tree_iter iter
;
1075 int ret
= SWAP_AGAIN
;
1076 unsigned long cursor
;
1077 unsigned long max_nl_cursor
= 0;
1078 unsigned long max_nl_size
= 0;
1079 unsigned int mapcount
;
1080 unsigned int mlocked
= 0;
1082 if (MLOCK_PAGES
&& unlikely(unlock
))
1083 ret
= SWAP_SUCCESS
; /* default for try_to_munlock() */
1085 spin_lock(&mapping
->i_mmap_lock
);
1086 vma_prio_tree_foreach(vma
, &iter
, &mapping
->i_mmap
, pgoff
, pgoff
) {
1087 if (MLOCK_PAGES
&& unlikely(unlock
)) {
1088 if (!(vma
->vm_flags
& VM_LOCKED
))
1089 continue; /* must visit all vmas */
1092 ret
= try_to_unmap_one(page
, vma
, migration
);
1093 if (ret
== SWAP_FAIL
|| !page_mapped(page
))
1096 if (ret
== SWAP_MLOCK
) {
1097 mlocked
= try_to_mlock_page(page
, vma
);
1099 break; /* stop if actually mlocked page */
1106 if (list_empty(&mapping
->i_mmap_nonlinear
))
1109 list_for_each_entry(vma
, &mapping
->i_mmap_nonlinear
,
1110 shared
.vm_set
.list
) {
1111 if (MLOCK_PAGES
&& unlikely(unlock
)) {
1112 if (!(vma
->vm_flags
& VM_LOCKED
))
1113 continue; /* must visit all vmas */
1114 ret
= SWAP_MLOCK
; /* leave mlocked == 0 */
1115 goto out
; /* no need to look further */
1117 if (!MLOCK_PAGES
&& !migration
&& (vma
->vm_flags
& VM_LOCKED
))
1119 cursor
= (unsigned long) vma
->vm_private_data
;
1120 if (cursor
> max_nl_cursor
)
1121 max_nl_cursor
= cursor
;
1122 cursor
= vma
->vm_end
- vma
->vm_start
;
1123 if (cursor
> max_nl_size
)
1124 max_nl_size
= cursor
;
1127 if (max_nl_size
== 0) { /* all nonlinears locked or reserved ? */
1133 * We don't try to search for this page in the nonlinear vmas,
1134 * and page_referenced wouldn't have found it anyway. Instead
1135 * just walk the nonlinear vmas trying to age and unmap some.
1136 * The mapcount of the page we came in with is irrelevant,
1137 * but even so use it as a guide to how hard we should try?
1139 mapcount
= page_mapcount(page
);
1142 cond_resched_lock(&mapping
->i_mmap_lock
);
1144 max_nl_size
= (max_nl_size
+ CLUSTER_SIZE
- 1) & CLUSTER_MASK
;
1145 if (max_nl_cursor
== 0)
1146 max_nl_cursor
= CLUSTER_SIZE
;
1149 list_for_each_entry(vma
, &mapping
->i_mmap_nonlinear
,
1150 shared
.vm_set
.list
) {
1151 if (!MLOCK_PAGES
&& !migration
&&
1152 (vma
->vm_flags
& VM_LOCKED
))
1154 cursor
= (unsigned long) vma
->vm_private_data
;
1155 while ( cursor
< max_nl_cursor
&&
1156 cursor
< vma
->vm_end
- vma
->vm_start
) {
1157 ret
= try_to_unmap_cluster(cursor
, &mapcount
,
1159 if (ret
== SWAP_MLOCK
)
1160 mlocked
= 2; /* to return below */
1161 cursor
+= CLUSTER_SIZE
;
1162 vma
->vm_private_data
= (void *) cursor
;
1163 if ((int)mapcount
<= 0)
1166 vma
->vm_private_data
= (void *) max_nl_cursor
;
1168 cond_resched_lock(&mapping
->i_mmap_lock
);
1169 max_nl_cursor
+= CLUSTER_SIZE
;
1170 } while (max_nl_cursor
<= max_nl_size
);
1173 * Don't loop forever (perhaps all the remaining pages are
1174 * in locked vmas). Reset cursor on all unreserved nonlinear
1175 * vmas, now forgetting on which ones it had fallen behind.
1177 list_for_each_entry(vma
, &mapping
->i_mmap_nonlinear
, shared
.vm_set
.list
)
1178 vma
->vm_private_data
= NULL
;
1180 spin_unlock(&mapping
->i_mmap_lock
);
1182 ret
= SWAP_MLOCK
; /* actually mlocked the page */
1183 else if (ret
== SWAP_MLOCK
)
1184 ret
= SWAP_AGAIN
; /* saw VM_LOCKED vma */
1189 * try_to_unmap - try to remove all page table mappings to a page
1190 * @page: the page to get unmapped
1191 * @migration: migration flag
1193 * Tries to remove all the page table entries which are mapping this
1194 * page, used in the pageout path. Caller must hold the page lock.
1195 * Return values are:
1197 * SWAP_SUCCESS - we succeeded in removing all mappings
1198 * SWAP_AGAIN - we missed a mapping, try again later
1199 * SWAP_FAIL - the page is unswappable
1200 * SWAP_MLOCK - page is mlocked.
1202 int try_to_unmap(struct page
*page
, int migration
)
1206 BUG_ON(!PageLocked(page
));
1209 ret
= try_to_unmap_anon(page
, 0, migration
);
1211 ret
= try_to_unmap_file(page
, 0, migration
);
1212 if (ret
!= SWAP_MLOCK
&& !page_mapped(page
))
1217 #ifdef CONFIG_UNEVICTABLE_LRU
1219 * try_to_munlock - try to munlock a page
1220 * @page: the page to be munlocked
1222 * Called from munlock code. Checks all of the VMAs mapping the page
1223 * to make sure nobody else has this page mlocked. The page will be
1224 * returned with PG_mlocked cleared if no other vmas have it mlocked.
1226 * Return values are:
1228 * SWAP_SUCCESS - no vma's holding page mlocked.
1229 * SWAP_AGAIN - page mapped in mlocked vma -- couldn't acquire mmap sem
1230 * SWAP_MLOCK - page is now mlocked.
1232 int try_to_munlock(struct page
*page
)
1234 VM_BUG_ON(!PageLocked(page
) || PageLRU(page
));
1237 return try_to_unmap_anon(page
, 1, 0);
1239 return try_to_unmap_file(page
, 1, 0);
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