]>
git.proxmox.com Git - mirror_ubuntu-hirsute-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)
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
))
366 /* Pretend the page is referenced if the task has the
367 swap token and is in the middle of a page fault. */
368 if (mm
!= current
->mm
&& has_swap_token(mm
) &&
369 rwsem_is_locked(&mm
->mmap_sem
))
374 pte_unmap_unlock(pte
, ptl
);
379 static int page_referenced_anon(struct page
*page
,
380 struct mem_cgroup
*mem_cont
)
382 unsigned int mapcount
;
383 struct anon_vma
*anon_vma
;
384 struct vm_area_struct
*vma
;
387 anon_vma
= page_lock_anon_vma(page
);
391 mapcount
= page_mapcount(page
);
392 list_for_each_entry(vma
, &anon_vma
->head
, anon_vma_node
) {
394 * If we are reclaiming on behalf of a cgroup, skip
395 * counting on behalf of references from different
398 if (mem_cont
&& !mm_match_cgroup(vma
->vm_mm
, mem_cont
))
400 referenced
+= page_referenced_one(page
, vma
, &mapcount
);
405 page_unlock_anon_vma(anon_vma
);
410 * page_referenced_file - referenced check for object-based rmap
411 * @page: the page we're checking references on.
412 * @mem_cont: target memory controller
414 * For an object-based mapped page, find all the places it is mapped and
415 * check/clear the referenced flag. This is done by following the page->mapping
416 * pointer, then walking the chain of vmas it holds. It returns the number
417 * of references it found.
419 * This function is only called from page_referenced for object-based pages.
421 static int page_referenced_file(struct page
*page
,
422 struct mem_cgroup
*mem_cont
)
424 unsigned int mapcount
;
425 struct address_space
*mapping
= page
->mapping
;
426 pgoff_t pgoff
= page
->index
<< (PAGE_CACHE_SHIFT
- PAGE_SHIFT
);
427 struct vm_area_struct
*vma
;
428 struct prio_tree_iter iter
;
432 * The caller's checks on page->mapping and !PageAnon have made
433 * sure that this is a file page: the check for page->mapping
434 * excludes the case just before it gets set on an anon page.
436 BUG_ON(PageAnon(page
));
439 * The page lock not only makes sure that page->mapping cannot
440 * suddenly be NULLified by truncation, it makes sure that the
441 * structure at mapping cannot be freed and reused yet,
442 * so we can safely take mapping->i_mmap_lock.
444 BUG_ON(!PageLocked(page
));
446 spin_lock(&mapping
->i_mmap_lock
);
449 * i_mmap_lock does not stabilize mapcount at all, but mapcount
450 * is more likely to be accurate if we note it after spinning.
452 mapcount
= page_mapcount(page
);
454 vma_prio_tree_foreach(vma
, &iter
, &mapping
->i_mmap
, pgoff
, pgoff
) {
456 * If we are reclaiming on behalf of a cgroup, skip
457 * counting on behalf of references from different
460 if (mem_cont
&& !mm_match_cgroup(vma
->vm_mm
, mem_cont
))
462 referenced
+= page_referenced_one(page
, vma
, &mapcount
);
467 spin_unlock(&mapping
->i_mmap_lock
);
472 * page_referenced - test if the page was referenced
473 * @page: the page to test
474 * @is_locked: caller holds lock on the page
475 * @mem_cont: target memory controller
477 * Quick test_and_clear_referenced for all mappings to a page,
478 * returns the number of ptes which referenced the page.
480 int page_referenced(struct page
*page
, int is_locked
,
481 struct mem_cgroup
*mem_cont
)
485 if (TestClearPageReferenced(page
))
488 if (page_mapped(page
) && page
->mapping
) {
490 referenced
+= page_referenced_anon(page
, mem_cont
);
492 referenced
+= page_referenced_file(page
, mem_cont
);
493 else if (!trylock_page(page
))
498 page_referenced_file(page
, mem_cont
);
503 if (page_test_and_clear_young(page
))
509 static int page_mkclean_one(struct page
*page
, struct vm_area_struct
*vma
)
511 struct mm_struct
*mm
= vma
->vm_mm
;
512 unsigned long address
;
517 address
= vma_address(page
, vma
);
518 if (address
== -EFAULT
)
521 pte
= page_check_address(page
, mm
, address
, &ptl
, 1);
525 if (pte_dirty(*pte
) || pte_write(*pte
)) {
528 flush_cache_page(vma
, address
, pte_pfn(*pte
));
529 entry
= ptep_clear_flush_notify(vma
, address
, pte
);
530 entry
= pte_wrprotect(entry
);
531 entry
= pte_mkclean(entry
);
532 set_pte_at(mm
, address
, pte
, entry
);
536 pte_unmap_unlock(pte
, ptl
);
541 static int page_mkclean_file(struct address_space
*mapping
, struct page
*page
)
543 pgoff_t pgoff
= page
->index
<< (PAGE_CACHE_SHIFT
- PAGE_SHIFT
);
544 struct vm_area_struct
*vma
;
545 struct prio_tree_iter iter
;
548 BUG_ON(PageAnon(page
));
550 spin_lock(&mapping
->i_mmap_lock
);
551 vma_prio_tree_foreach(vma
, &iter
, &mapping
->i_mmap
, pgoff
, pgoff
) {
552 if (vma
->vm_flags
& VM_SHARED
)
553 ret
+= page_mkclean_one(page
, vma
);
555 spin_unlock(&mapping
->i_mmap_lock
);
559 int page_mkclean(struct page
*page
)
563 BUG_ON(!PageLocked(page
));
565 if (page_mapped(page
)) {
566 struct address_space
*mapping
= page_mapping(page
);
568 ret
= page_mkclean_file(mapping
, page
);
569 if (page_test_dirty(page
)) {
570 page_clear_dirty(page
);
578 EXPORT_SYMBOL_GPL(page_mkclean
);
581 * __page_set_anon_rmap - setup new anonymous rmap
582 * @page: the page to add the mapping to
583 * @vma: the vm area in which the mapping is added
584 * @address: the user virtual address mapped
586 static void __page_set_anon_rmap(struct page
*page
,
587 struct vm_area_struct
*vma
, unsigned long address
)
589 struct anon_vma
*anon_vma
= vma
->anon_vma
;
592 anon_vma
= (void *) anon_vma
+ PAGE_MAPPING_ANON
;
593 page
->mapping
= (struct address_space
*) anon_vma
;
595 page
->index
= linear_page_index(vma
, address
);
598 * nr_mapped state can be updated without turning off
599 * interrupts because it is not modified via interrupt.
601 __inc_zone_page_state(page
, NR_ANON_PAGES
);
605 * __page_check_anon_rmap - sanity check anonymous rmap addition
606 * @page: the page to add the mapping to
607 * @vma: the vm area in which the mapping is added
608 * @address: the user virtual address mapped
610 static void __page_check_anon_rmap(struct page
*page
,
611 struct vm_area_struct
*vma
, unsigned long address
)
613 #ifdef CONFIG_DEBUG_VM
615 * The page's anon-rmap details (mapping and index) are guaranteed to
616 * be set up correctly at this point.
618 * We have exclusion against page_add_anon_rmap because the caller
619 * always holds the page locked, except if called from page_dup_rmap,
620 * in which case the page is already known to be setup.
622 * We have exclusion against page_add_new_anon_rmap because those pages
623 * are initially only visible via the pagetables, and the pte is locked
624 * over the call to page_add_new_anon_rmap.
626 struct anon_vma
*anon_vma
= vma
->anon_vma
;
627 anon_vma
= (void *) anon_vma
+ PAGE_MAPPING_ANON
;
628 BUG_ON(page
->mapping
!= (struct address_space
*)anon_vma
);
629 BUG_ON(page
->index
!= linear_page_index(vma
, address
));
634 * page_add_anon_rmap - add pte mapping to an anonymous page
635 * @page: the page to add the mapping to
636 * @vma: the vm area in which the mapping is added
637 * @address: the user virtual address mapped
639 * The caller needs to hold the pte lock and the page must be locked.
641 void page_add_anon_rmap(struct page
*page
,
642 struct vm_area_struct
*vma
, unsigned long address
)
644 VM_BUG_ON(!PageLocked(page
));
645 VM_BUG_ON(address
< vma
->vm_start
|| address
>= vma
->vm_end
);
646 if (atomic_inc_and_test(&page
->_mapcount
))
647 __page_set_anon_rmap(page
, vma
, address
);
649 __page_check_anon_rmap(page
, vma
, address
);
653 * page_add_new_anon_rmap - add pte mapping to a new anonymous page
654 * @page: the page to add the mapping to
655 * @vma: the vm area in which the mapping is added
656 * @address: the user virtual address mapped
658 * Same as page_add_anon_rmap but must only be called on *new* pages.
659 * This means the inc-and-test can be bypassed.
660 * Page does not have to be locked.
662 void page_add_new_anon_rmap(struct page
*page
,
663 struct vm_area_struct
*vma
, unsigned long address
)
665 BUG_ON(address
< vma
->vm_start
|| address
>= vma
->vm_end
);
666 atomic_set(&page
->_mapcount
, 0); /* elevate count by 1 (starts at -1) */
667 __page_set_anon_rmap(page
, vma
, address
);
671 * page_add_file_rmap - add pte mapping to a file page
672 * @page: the page to add the mapping to
674 * The caller needs to hold the pte lock.
676 void page_add_file_rmap(struct page
*page
)
678 if (atomic_inc_and_test(&page
->_mapcount
))
679 __inc_zone_page_state(page
, NR_FILE_MAPPED
);
682 #ifdef CONFIG_DEBUG_VM
684 * page_dup_rmap - duplicate pte mapping to a page
685 * @page: the page to add the mapping to
686 * @vma: the vm area being duplicated
687 * @address: the user virtual address mapped
689 * For copy_page_range only: minimal extract from page_add_file_rmap /
690 * page_add_anon_rmap, avoiding unnecessary tests (already checked) so it's
693 * The caller needs to hold the pte lock.
695 void page_dup_rmap(struct page
*page
, struct vm_area_struct
*vma
, unsigned long address
)
697 BUG_ON(page_mapcount(page
) == 0);
699 __page_check_anon_rmap(page
, vma
, address
);
700 atomic_inc(&page
->_mapcount
);
705 * page_remove_rmap - take down pte mapping from a page
706 * @page: page to remove mapping from
707 * @vma: the vm area in which the mapping is removed
709 * The caller needs to hold the pte lock.
711 void page_remove_rmap(struct page
*page
, struct vm_area_struct
*vma
)
713 if (atomic_add_negative(-1, &page
->_mapcount
)) {
714 if (unlikely(page_mapcount(page
) < 0)) {
715 printk (KERN_EMERG
"Eeek! page_mapcount(page) went negative! (%d)\n", page_mapcount(page
));
716 printk (KERN_EMERG
" page pfn = %lx\n", page_to_pfn(page
));
717 printk (KERN_EMERG
" page->flags = %lx\n", page
->flags
);
718 printk (KERN_EMERG
" page->count = %x\n", page_count(page
));
719 printk (KERN_EMERG
" page->mapping = %p\n", page
->mapping
);
720 print_symbol (KERN_EMERG
" vma->vm_ops = %s\n", (unsigned long)vma
->vm_ops
);
722 print_symbol (KERN_EMERG
" vma->vm_ops->fault = %s\n", (unsigned long)vma
->vm_ops
->fault
);
724 if (vma
->vm_file
&& vma
->vm_file
->f_op
)
725 print_symbol (KERN_EMERG
" vma->vm_file->f_op->mmap = %s\n", (unsigned long)vma
->vm_file
->f_op
->mmap
);
730 * Now that the last pte has gone, s390 must transfer dirty
731 * flag from storage key to struct page. We can usually skip
732 * this if the page is anon, so about to be freed; but perhaps
733 * not if it's in swapcache - there might be another pte slot
734 * containing the swap entry, but page not yet written to swap.
736 if ((!PageAnon(page
) || PageSwapCache(page
)) &&
737 page_test_dirty(page
)) {
738 page_clear_dirty(page
);
739 set_page_dirty(page
);
742 mem_cgroup_uncharge_page(page
);
743 __dec_zone_page_state(page
,
744 PageAnon(page
) ? NR_ANON_PAGES
: NR_FILE_MAPPED
);
746 * It would be tidy to reset the PageAnon mapping here,
747 * but that might overwrite a racing page_add_anon_rmap
748 * which increments mapcount after us but sets mapping
749 * before us: so leave the reset to free_hot_cold_page,
750 * and remember that it's only reliable while mapped.
751 * Leaving it set also helps swapoff to reinstate ptes
752 * faster for those pages still in swapcache.
758 * Subfunctions of try_to_unmap: try_to_unmap_one called
759 * repeatedly from either try_to_unmap_anon or try_to_unmap_file.
761 static int try_to_unmap_one(struct page
*page
, struct vm_area_struct
*vma
,
764 struct mm_struct
*mm
= vma
->vm_mm
;
765 unsigned long address
;
769 int ret
= SWAP_AGAIN
;
771 address
= vma_address(page
, vma
);
772 if (address
== -EFAULT
)
775 pte
= page_check_address(page
, mm
, address
, &ptl
, 0);
780 * If the page is mlock()d, we cannot swap it out.
781 * If it's recently referenced (perhaps page_referenced
782 * skipped over this mm) then we should reactivate it.
785 if (vma
->vm_flags
& VM_LOCKED
) {
789 if (ptep_clear_flush_young_notify(vma
, address
, pte
)) {
795 /* Nuke the page table entry. */
796 flush_cache_page(vma
, address
, page_to_pfn(page
));
797 pteval
= ptep_clear_flush_notify(vma
, address
, pte
);
799 /* Move the dirty bit to the physical page now the pte is gone. */
800 if (pte_dirty(pteval
))
801 set_page_dirty(page
);
803 /* Update high watermark before we lower rss */
804 update_hiwater_rss(mm
);
806 if (PageAnon(page
)) {
807 swp_entry_t entry
= { .val
= page_private(page
) };
809 if (PageSwapCache(page
)) {
811 * Store the swap location in the pte.
812 * See handle_pte_fault() ...
814 swap_duplicate(entry
);
815 if (list_empty(&mm
->mmlist
)) {
816 spin_lock(&mmlist_lock
);
817 if (list_empty(&mm
->mmlist
))
818 list_add(&mm
->mmlist
, &init_mm
.mmlist
);
819 spin_unlock(&mmlist_lock
);
821 dec_mm_counter(mm
, anon_rss
);
822 } else if (PAGE_MIGRATION
) {
824 * Store the pfn of the page in a special migration
825 * pte. do_swap_page() will wait until the migration
826 * pte is removed and then restart fault handling.
829 entry
= make_migration_entry(page
, pte_write(pteval
));
831 set_pte_at(mm
, address
, pte
, swp_entry_to_pte(entry
));
832 BUG_ON(pte_file(*pte
));
833 } else if (PAGE_MIGRATION
&& migration
) {
834 /* Establish migration entry for a file page */
836 entry
= make_migration_entry(page
, pte_write(pteval
));
837 set_pte_at(mm
, address
, pte
, swp_entry_to_pte(entry
));
839 dec_mm_counter(mm
, file_rss
);
842 page_remove_rmap(page
, vma
);
843 page_cache_release(page
);
846 pte_unmap_unlock(pte
, ptl
);
852 * objrmap doesn't work for nonlinear VMAs because the assumption that
853 * offset-into-file correlates with offset-into-virtual-addresses does not hold.
854 * Consequently, given a particular page and its ->index, we cannot locate the
855 * ptes which are mapping that page without an exhaustive linear search.
857 * So what this code does is a mini "virtual scan" of each nonlinear VMA which
858 * maps the file to which the target page belongs. The ->vm_private_data field
859 * holds the current cursor into that scan. Successive searches will circulate
860 * around the vma's virtual address space.
862 * So as more replacement pressure is applied to the pages in a nonlinear VMA,
863 * more scanning pressure is placed against them as well. Eventually pages
864 * will become fully unmapped and are eligible for eviction.
866 * For very sparsely populated VMAs this is a little inefficient - chances are
867 * there there won't be many ptes located within the scan cluster. In this case
868 * maybe we could scan further - to the end of the pte page, perhaps.
870 * Mlocked pages: check VM_LOCKED under mmap_sem held for read, if we can
871 * acquire it without blocking. If vma locked, mlock the pages in the cluster,
872 * rather than unmapping them. If we encounter the "check_page" that vmscan is
873 * trying to unmap, return SWAP_MLOCK, else default SWAP_AGAIN.
875 #define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE)
876 #define CLUSTER_MASK (~(CLUSTER_SIZE - 1))
878 static int try_to_unmap_cluster(unsigned long cursor
, unsigned int *mapcount
,
879 struct vm_area_struct
*vma
, struct page
*check_page
)
881 struct mm_struct
*mm
= vma
->vm_mm
;
889 unsigned long address
;
891 int ret
= SWAP_AGAIN
;
894 address
= (vma
->vm_start
+ cursor
) & CLUSTER_MASK
;
895 end
= address
+ CLUSTER_SIZE
;
896 if (address
< vma
->vm_start
)
897 address
= vma
->vm_start
;
898 if (end
> vma
->vm_end
)
901 pgd
= pgd_offset(mm
, address
);
902 if (!pgd_present(*pgd
))
905 pud
= pud_offset(pgd
, address
);
906 if (!pud_present(*pud
))
909 pmd
= pmd_offset(pud
, address
);
910 if (!pmd_present(*pmd
))
914 * MLOCK_PAGES => feature is configured.
915 * if we can acquire the mmap_sem for read, and vma is VM_LOCKED,
916 * keep the sem while scanning the cluster for mlocking pages.
918 if (MLOCK_PAGES
&& down_read_trylock(&vma
->vm_mm
->mmap_sem
)) {
919 locked_vma
= (vma
->vm_flags
& VM_LOCKED
);
921 up_read(&vma
->vm_mm
->mmap_sem
); /* don't need it */
924 pte
= pte_offset_map_lock(mm
, pmd
, address
, &ptl
);
926 /* Update high watermark before we lower rss */
927 update_hiwater_rss(mm
);
929 for (; address
< end
; pte
++, address
+= PAGE_SIZE
) {
930 if (!pte_present(*pte
))
932 page
= vm_normal_page(vma
, address
, *pte
);
933 BUG_ON(!page
|| PageAnon(page
));
936 mlock_vma_page(page
); /* no-op if already mlocked */
937 if (page
== check_page
)
939 continue; /* don't unmap */
942 if (ptep_clear_flush_young_notify(vma
, address
, pte
))
945 /* Nuke the page table entry. */
946 flush_cache_page(vma
, address
, pte_pfn(*pte
));
947 pteval
= ptep_clear_flush_notify(vma
, address
, pte
);
949 /* If nonlinear, store the file page offset in the pte. */
950 if (page
->index
!= linear_page_index(vma
, address
))
951 set_pte_at(mm
, address
, pte
, pgoff_to_pte(page
->index
));
953 /* Move the dirty bit to the physical page now the pte is gone. */
954 if (pte_dirty(pteval
))
955 set_page_dirty(page
);
957 page_remove_rmap(page
, vma
);
958 page_cache_release(page
);
959 dec_mm_counter(mm
, file_rss
);
962 pte_unmap_unlock(pte
- 1, ptl
);
964 up_read(&vma
->vm_mm
->mmap_sem
);
969 * common handling for pages mapped in VM_LOCKED vmas
971 static int try_to_mlock_page(struct page
*page
, struct vm_area_struct
*vma
)
975 if (down_read_trylock(&vma
->vm_mm
->mmap_sem
)) {
976 if (vma
->vm_flags
& VM_LOCKED
) {
977 mlock_vma_page(page
);
978 mlocked
++; /* really mlocked the page */
980 up_read(&vma
->vm_mm
->mmap_sem
);
986 * try_to_unmap_anon - unmap or unlock anonymous page using the object-based
988 * @page: the page to unmap/unlock
989 * @unlock: request for unlock rather than unmap [unlikely]
990 * @migration: unmapping for migration - ignored if @unlock
992 * Find all the mappings of a page using the mapping pointer and the vma chains
993 * contained in the anon_vma struct it points to.
995 * This function is only called from try_to_unmap/try_to_munlock for
997 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
998 * where the page was found will be held for write. So, we won't recheck
999 * vm_flags for that VMA. That should be OK, because that vma shouldn't be
1002 static int try_to_unmap_anon(struct page
*page
, int unlock
, int migration
)
1004 struct anon_vma
*anon_vma
;
1005 struct vm_area_struct
*vma
;
1006 unsigned int mlocked
= 0;
1007 int ret
= SWAP_AGAIN
;
1009 if (MLOCK_PAGES
&& unlikely(unlock
))
1010 ret
= SWAP_SUCCESS
; /* default for try_to_munlock() */
1012 anon_vma
= page_lock_anon_vma(page
);
1016 list_for_each_entry(vma
, &anon_vma
->head
, anon_vma_node
) {
1017 if (MLOCK_PAGES
&& unlikely(unlock
)) {
1018 if (!((vma
->vm_flags
& VM_LOCKED
) &&
1019 page_mapped_in_vma(page
, vma
)))
1020 continue; /* must visit all unlocked vmas */
1021 ret
= SWAP_MLOCK
; /* saw at least one mlocked vma */
1023 ret
= try_to_unmap_one(page
, vma
, migration
);
1024 if (ret
== SWAP_FAIL
|| !page_mapped(page
))
1027 if (ret
== SWAP_MLOCK
) {
1028 mlocked
= try_to_mlock_page(page
, vma
);
1030 break; /* stop if actually mlocked page */
1034 page_unlock_anon_vma(anon_vma
);
1037 ret
= SWAP_MLOCK
; /* actually mlocked the page */
1038 else if (ret
== SWAP_MLOCK
)
1039 ret
= SWAP_AGAIN
; /* saw VM_LOCKED vma */
1045 * try_to_unmap_file - unmap/unlock file page using the object-based rmap method
1046 * @page: the page to unmap/unlock
1047 * @unlock: request for unlock rather than unmap [unlikely]
1048 * @migration: unmapping for migration - ignored if @unlock
1050 * Find all the mappings of a page using the mapping pointer and the vma chains
1051 * contained in the address_space struct it points to.
1053 * This function is only called from try_to_unmap/try_to_munlock for
1054 * object-based pages.
1055 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1056 * where the page was found will be held for write. So, we won't recheck
1057 * vm_flags for that VMA. That should be OK, because that vma shouldn't be
1060 static int try_to_unmap_file(struct page
*page
, int unlock
, int migration
)
1062 struct address_space
*mapping
= page
->mapping
;
1063 pgoff_t pgoff
= page
->index
<< (PAGE_CACHE_SHIFT
- PAGE_SHIFT
);
1064 struct vm_area_struct
*vma
;
1065 struct prio_tree_iter iter
;
1066 int ret
= SWAP_AGAIN
;
1067 unsigned long cursor
;
1068 unsigned long max_nl_cursor
= 0;
1069 unsigned long max_nl_size
= 0;
1070 unsigned int mapcount
;
1071 unsigned int mlocked
= 0;
1073 if (MLOCK_PAGES
&& unlikely(unlock
))
1074 ret
= SWAP_SUCCESS
; /* default for try_to_munlock() */
1076 spin_lock(&mapping
->i_mmap_lock
);
1077 vma_prio_tree_foreach(vma
, &iter
, &mapping
->i_mmap
, pgoff
, pgoff
) {
1078 if (MLOCK_PAGES
&& unlikely(unlock
)) {
1079 if (!(vma
->vm_flags
& VM_LOCKED
))
1080 continue; /* must visit all vmas */
1083 ret
= try_to_unmap_one(page
, vma
, migration
);
1084 if (ret
== SWAP_FAIL
|| !page_mapped(page
))
1087 if (ret
== SWAP_MLOCK
) {
1088 mlocked
= try_to_mlock_page(page
, vma
);
1090 break; /* stop if actually mlocked page */
1097 if (list_empty(&mapping
->i_mmap_nonlinear
))
1100 list_for_each_entry(vma
, &mapping
->i_mmap_nonlinear
,
1101 shared
.vm_set
.list
) {
1102 if (MLOCK_PAGES
&& unlikely(unlock
)) {
1103 if (!(vma
->vm_flags
& VM_LOCKED
))
1104 continue; /* must visit all vmas */
1105 ret
= SWAP_MLOCK
; /* leave mlocked == 0 */
1106 goto out
; /* no need to look further */
1108 if (!MLOCK_PAGES
&& !migration
&& (vma
->vm_flags
& VM_LOCKED
))
1110 cursor
= (unsigned long) vma
->vm_private_data
;
1111 if (cursor
> max_nl_cursor
)
1112 max_nl_cursor
= cursor
;
1113 cursor
= vma
->vm_end
- vma
->vm_start
;
1114 if (cursor
> max_nl_size
)
1115 max_nl_size
= cursor
;
1118 if (max_nl_size
== 0) { /* all nonlinears locked or reserved ? */
1124 * We don't try to search for this page in the nonlinear vmas,
1125 * and page_referenced wouldn't have found it anyway. Instead
1126 * just walk the nonlinear vmas trying to age and unmap some.
1127 * The mapcount of the page we came in with is irrelevant,
1128 * but even so use it as a guide to how hard we should try?
1130 mapcount
= page_mapcount(page
);
1133 cond_resched_lock(&mapping
->i_mmap_lock
);
1135 max_nl_size
= (max_nl_size
+ CLUSTER_SIZE
- 1) & CLUSTER_MASK
;
1136 if (max_nl_cursor
== 0)
1137 max_nl_cursor
= CLUSTER_SIZE
;
1140 list_for_each_entry(vma
, &mapping
->i_mmap_nonlinear
,
1141 shared
.vm_set
.list
) {
1142 if (!MLOCK_PAGES
&& !migration
&&
1143 (vma
->vm_flags
& VM_LOCKED
))
1145 cursor
= (unsigned long) vma
->vm_private_data
;
1146 while ( cursor
< max_nl_cursor
&&
1147 cursor
< vma
->vm_end
- vma
->vm_start
) {
1148 ret
= try_to_unmap_cluster(cursor
, &mapcount
,
1150 if (ret
== SWAP_MLOCK
)
1151 mlocked
= 2; /* to return below */
1152 cursor
+= CLUSTER_SIZE
;
1153 vma
->vm_private_data
= (void *) cursor
;
1154 if ((int)mapcount
<= 0)
1157 vma
->vm_private_data
= (void *) max_nl_cursor
;
1159 cond_resched_lock(&mapping
->i_mmap_lock
);
1160 max_nl_cursor
+= CLUSTER_SIZE
;
1161 } while (max_nl_cursor
<= max_nl_size
);
1164 * Don't loop forever (perhaps all the remaining pages are
1165 * in locked vmas). Reset cursor on all unreserved nonlinear
1166 * vmas, now forgetting on which ones it had fallen behind.
1168 list_for_each_entry(vma
, &mapping
->i_mmap_nonlinear
, shared
.vm_set
.list
)
1169 vma
->vm_private_data
= NULL
;
1171 spin_unlock(&mapping
->i_mmap_lock
);
1173 ret
= SWAP_MLOCK
; /* actually mlocked the page */
1174 else if (ret
== SWAP_MLOCK
)
1175 ret
= SWAP_AGAIN
; /* saw VM_LOCKED vma */
1180 * try_to_unmap - try to remove all page table mappings to a page
1181 * @page: the page to get unmapped
1182 * @migration: migration flag
1184 * Tries to remove all the page table entries which are mapping this
1185 * page, used in the pageout path. Caller must hold the page lock.
1186 * Return values are:
1188 * SWAP_SUCCESS - we succeeded in removing all mappings
1189 * SWAP_AGAIN - we missed a mapping, try again later
1190 * SWAP_FAIL - the page is unswappable
1191 * SWAP_MLOCK - page is mlocked.
1193 int try_to_unmap(struct page
*page
, int migration
)
1197 BUG_ON(!PageLocked(page
));
1200 ret
= try_to_unmap_anon(page
, 0, migration
);
1202 ret
= try_to_unmap_file(page
, 0, migration
);
1203 if (ret
!= SWAP_MLOCK
&& !page_mapped(page
))
1208 #ifdef CONFIG_UNEVICTABLE_LRU
1210 * try_to_munlock - try to munlock a page
1211 * @page: the page to be munlocked
1213 * Called from munlock code. Checks all of the VMAs mapping the page
1214 * to make sure nobody else has this page mlocked. The page will be
1215 * returned with PG_mlocked cleared if no other vmas have it mlocked.
1217 * Return values are:
1219 * SWAP_SUCCESS - no vma's holding page mlocked.
1220 * SWAP_AGAIN - page mapped in mlocked vma -- couldn't acquire mmap sem
1221 * SWAP_MLOCK - page is now mlocked.
1223 int try_to_munlock(struct page
*page
)
1225 VM_BUG_ON(!PageLocked(page
) || PageLRU(page
));
1228 return try_to_unmap_anon(page
, 1, 0);
1230 return try_to_unmap_file(page
, 1, 0);