2 * Memory Migration functionality - linux/mm/migration.c
4 * Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter
6 * Page migration was first developed in the context of the memory hotplug
7 * project. The main authors of the migration code are:
9 * IWAMOTO Toshihiro <iwamoto@valinux.co.jp>
10 * Hirokazu Takahashi <taka@valinux.co.jp>
11 * Dave Hansen <haveblue@us.ibm.com>
15 #include <linux/migrate.h>
16 #include <linux/module.h>
17 #include <linux/swap.h>
18 #include <linux/swapops.h>
19 #include <linux/pagemap.h>
20 #include <linux/buffer_head.h>
21 #include <linux/mm_inline.h>
22 #include <linux/nsproxy.h>
23 #include <linux/pagevec.h>
24 #include <linux/rmap.h>
25 #include <linux/topology.h>
26 #include <linux/cpu.h>
27 #include <linux/cpuset.h>
28 #include <linux/writeback.h>
29 #include <linux/mempolicy.h>
30 #include <linux/vmalloc.h>
31 #include <linux/security.h>
32 #include <linux/memcontrol.h>
36 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
39 * Isolate one page from the LRU lists. If successful put it onto
40 * the indicated list with elevated page count.
43 * -EBUSY: page not on LRU list
44 * 0: page removed from LRU list and added to the specified list.
46 int isolate_lru_page(struct page
*page
, struct list_head
*pagelist
)
51 struct zone
*zone
= page_zone(page
);
53 spin_lock_irq(&zone
->lru_lock
);
54 if (PageLRU(page
) && get_page_unless_zero(page
)) {
58 del_page_from_active_list(zone
, page
);
60 del_page_from_inactive_list(zone
, page
);
61 list_add_tail(&page
->lru
, pagelist
);
63 spin_unlock_irq(&zone
->lru_lock
);
69 * migrate_prep() needs to be called before we start compiling a list of pages
70 * to be migrated using isolate_lru_page().
72 int migrate_prep(void)
75 * Clear the LRU lists so pages can be isolated.
76 * Note that pages may be moved off the LRU after we have
77 * drained them. Those pages will fail to migrate like other
78 * pages that may be busy.
85 static inline void move_to_lru(struct page
*page
)
87 if (PageActive(page
)) {
89 * lru_cache_add_active checks that
90 * the PG_active bit is off.
92 ClearPageActive(page
);
93 lru_cache_add_active(page
);
101 * Add isolated pages on the list back to the LRU.
103 * returns the number of pages put back.
105 int putback_lru_pages(struct list_head
*l
)
111 list_for_each_entry_safe(page
, page2
, l
, lru
) {
112 list_del(&page
->lru
);
120 * Restore a potential migration pte to a working pte entry
122 static void remove_migration_pte(struct vm_area_struct
*vma
,
123 struct page
*old
, struct page
*new)
125 struct mm_struct
*mm
= vma
->vm_mm
;
132 unsigned long addr
= page_address_in_vma(new, vma
);
137 pgd
= pgd_offset(mm
, addr
);
138 if (!pgd_present(*pgd
))
141 pud
= pud_offset(pgd
, addr
);
142 if (!pud_present(*pud
))
145 pmd
= pmd_offset(pud
, addr
);
146 if (!pmd_present(*pmd
))
149 ptep
= pte_offset_map(pmd
, addr
);
151 if (!is_swap_pte(*ptep
)) {
156 ptl
= pte_lockptr(mm
, pmd
);
159 if (!is_swap_pte(pte
))
162 entry
= pte_to_swp_entry(pte
);
164 if (!is_migration_entry(entry
) || migration_entry_to_page(entry
) != old
)
168 * Yes, ignore the return value from a GFP_ATOMIC mem_cgroup_charge.
169 * Failure is not an option here: we're now expected to remove every
170 * migration pte, and will cause crashes otherwise. Normally this
171 * is not an issue: mem_cgroup_prepare_migration bumped up the old
172 * page_cgroup count for safety, that's now attached to the new page,
173 * so this charge should just be another incrementation of the count,
174 * to keep in balance with rmap.c's mem_cgroup_uncharging. But if
175 * there's been a force_empty, those reference counts may no longer
176 * be reliable, and this charge can actually fail: oh well, we don't
177 * make the situation any worse by proceeding as if it had succeeded.
179 mem_cgroup_charge(new, mm
, GFP_ATOMIC
);
182 pte
= pte_mkold(mk_pte(new, vma
->vm_page_prot
));
183 if (is_write_migration_entry(entry
))
184 pte
= pte_mkwrite(pte
);
185 flush_cache_page(vma
, addr
, pte_pfn(pte
));
186 set_pte_at(mm
, addr
, ptep
, pte
);
189 page_add_anon_rmap(new, vma
, addr
);
191 page_add_file_rmap(new);
193 /* No need to invalidate - it was non-present before */
194 update_mmu_cache(vma
, addr
, pte
);
197 pte_unmap_unlock(ptep
, ptl
);
201 * Note that remove_file_migration_ptes will only work on regular mappings,
202 * Nonlinear mappings do not use migration entries.
204 static void remove_file_migration_ptes(struct page
*old
, struct page
*new)
206 struct vm_area_struct
*vma
;
207 struct address_space
*mapping
= page_mapping(new);
208 struct prio_tree_iter iter
;
209 pgoff_t pgoff
= new->index
<< (PAGE_CACHE_SHIFT
- PAGE_SHIFT
);
214 spin_lock(&mapping
->i_mmap_lock
);
216 vma_prio_tree_foreach(vma
, &iter
, &mapping
->i_mmap
, pgoff
, pgoff
)
217 remove_migration_pte(vma
, old
, new);
219 spin_unlock(&mapping
->i_mmap_lock
);
223 * Must hold mmap_sem lock on at least one of the vmas containing
224 * the page so that the anon_vma cannot vanish.
226 static void remove_anon_migration_ptes(struct page
*old
, struct page
*new)
228 struct anon_vma
*anon_vma
;
229 struct vm_area_struct
*vma
;
230 unsigned long mapping
;
232 mapping
= (unsigned long)new->mapping
;
234 if (!mapping
|| (mapping
& PAGE_MAPPING_ANON
) == 0)
238 * We hold the mmap_sem lock. So no need to call page_lock_anon_vma.
240 anon_vma
= (struct anon_vma
*) (mapping
- PAGE_MAPPING_ANON
);
241 spin_lock(&anon_vma
->lock
);
243 list_for_each_entry(vma
, &anon_vma
->head
, anon_vma_node
)
244 remove_migration_pte(vma
, old
, new);
246 spin_unlock(&anon_vma
->lock
);
250 * Get rid of all migration entries and replace them by
251 * references to the indicated page.
253 static void remove_migration_ptes(struct page
*old
, struct page
*new)
256 remove_anon_migration_ptes(old
, new);
258 remove_file_migration_ptes(old
, new);
262 * Something used the pte of a page under migration. We need to
263 * get to the page and wait until migration is finished.
264 * When we return from this function the fault will be retried.
266 * This function is called from do_swap_page().
268 void migration_entry_wait(struct mm_struct
*mm
, pmd_t
*pmd
,
269 unsigned long address
)
276 ptep
= pte_offset_map_lock(mm
, pmd
, address
, &ptl
);
278 if (!is_swap_pte(pte
))
281 entry
= pte_to_swp_entry(pte
);
282 if (!is_migration_entry(entry
))
285 page
= migration_entry_to_page(entry
);
288 pte_unmap_unlock(ptep
, ptl
);
289 wait_on_page_locked(page
);
293 pte_unmap_unlock(ptep
, ptl
);
297 * Replace the page in the mapping.
299 * The number of remaining references must be:
300 * 1 for anonymous pages without a mapping
301 * 2 for pages with a mapping
302 * 3 for pages with a mapping and PagePrivate set.
304 static int migrate_page_move_mapping(struct address_space
*mapping
,
305 struct page
*newpage
, struct page
*page
)
310 /* Anonymous page without mapping */
311 if (page_count(page
) != 1)
316 write_lock_irq(&mapping
->tree_lock
);
318 pslot
= radix_tree_lookup_slot(&mapping
->page_tree
,
321 if (page_count(page
) != 2 + !!PagePrivate(page
) ||
322 (struct page
*)radix_tree_deref_slot(pslot
) != page
) {
323 write_unlock_irq(&mapping
->tree_lock
);
328 * Now we know that no one else is looking at the page.
330 get_page(newpage
); /* add cache reference */
332 if (PageSwapCache(page
)) {
333 SetPageSwapCache(newpage
);
334 set_page_private(newpage
, page_private(page
));
338 radix_tree_replace_slot(pslot
, newpage
);
341 * Drop cache reference from old page.
342 * We know this isn't the last reference.
347 * If moved to a different zone then also account
348 * the page for that zone. Other VM counters will be
349 * taken care of when we establish references to the
350 * new page and drop references to the old page.
352 * Note that anonymous pages are accounted for
353 * via NR_FILE_PAGES and NR_ANON_PAGES if they
354 * are mapped to swap space.
356 __dec_zone_page_state(page
, NR_FILE_PAGES
);
357 __inc_zone_page_state(newpage
, NR_FILE_PAGES
);
359 write_unlock_irq(&mapping
->tree_lock
);
365 * Copy the page to its new location
367 static void migrate_page_copy(struct page
*newpage
, struct page
*page
)
369 copy_highpage(newpage
, page
);
372 SetPageError(newpage
);
373 if (PageReferenced(page
))
374 SetPageReferenced(newpage
);
375 if (PageUptodate(page
))
376 SetPageUptodate(newpage
);
377 if (PageActive(page
))
378 SetPageActive(newpage
);
379 if (PageChecked(page
))
380 SetPageChecked(newpage
);
381 if (PageMappedToDisk(page
))
382 SetPageMappedToDisk(newpage
);
384 if (PageDirty(page
)) {
385 clear_page_dirty_for_io(page
);
387 * Want to mark the page and the radix tree as dirty, and
388 * redo the accounting that clear_page_dirty_for_io undid,
389 * but we can't use set_page_dirty because that function
390 * is actually a signal that all of the page has become dirty.
391 * Wheras only part of our page may be dirty.
393 __set_page_dirty_nobuffers(newpage
);
397 ClearPageSwapCache(page
);
399 ClearPageActive(page
);
400 ClearPagePrivate(page
);
401 set_page_private(page
, 0);
402 page
->mapping
= NULL
;
405 * If any waiters have accumulated on the new page then
408 if (PageWriteback(newpage
))
409 end_page_writeback(newpage
);
412 /************************************************************
413 * Migration functions
414 ***********************************************************/
416 /* Always fail migration. Used for mappings that are not movable */
417 int fail_migrate_page(struct address_space
*mapping
,
418 struct page
*newpage
, struct page
*page
)
422 EXPORT_SYMBOL(fail_migrate_page
);
425 * Common logic to directly migrate a single page suitable for
426 * pages that do not use PagePrivate.
428 * Pages are locked upon entry and exit.
430 int migrate_page(struct address_space
*mapping
,
431 struct page
*newpage
, struct page
*page
)
435 BUG_ON(PageWriteback(page
)); /* Writeback must be complete */
437 rc
= migrate_page_move_mapping(mapping
, newpage
, page
);
442 migrate_page_copy(newpage
, page
);
445 EXPORT_SYMBOL(migrate_page
);
449 * Migration function for pages with buffers. This function can only be used
450 * if the underlying filesystem guarantees that no other references to "page"
453 int buffer_migrate_page(struct address_space
*mapping
,
454 struct page
*newpage
, struct page
*page
)
456 struct buffer_head
*bh
, *head
;
459 if (!page_has_buffers(page
))
460 return migrate_page(mapping
, newpage
, page
);
462 head
= page_buffers(page
);
464 rc
= migrate_page_move_mapping(mapping
, newpage
, page
);
473 bh
= bh
->b_this_page
;
475 } while (bh
!= head
);
477 ClearPagePrivate(page
);
478 set_page_private(newpage
, page_private(page
));
479 set_page_private(page
, 0);
485 set_bh_page(bh
, newpage
, bh_offset(bh
));
486 bh
= bh
->b_this_page
;
488 } while (bh
!= head
);
490 SetPagePrivate(newpage
);
492 migrate_page_copy(newpage
, page
);
498 bh
= bh
->b_this_page
;
500 } while (bh
!= head
);
504 EXPORT_SYMBOL(buffer_migrate_page
);
508 * Writeback a page to clean the dirty state
510 static int writeout(struct address_space
*mapping
, struct page
*page
)
512 struct writeback_control wbc
= {
513 .sync_mode
= WB_SYNC_NONE
,
516 .range_end
= LLONG_MAX
,
522 if (!mapping
->a_ops
->writepage
)
523 /* No write method for the address space */
526 if (!clear_page_dirty_for_io(page
))
527 /* Someone else already triggered a write */
531 * A dirty page may imply that the underlying filesystem has
532 * the page on some queue. So the page must be clean for
533 * migration. Writeout may mean we loose the lock and the
534 * page state is no longer what we checked for earlier.
535 * At this point we know that the migration attempt cannot
538 remove_migration_ptes(page
, page
);
540 rc
= mapping
->a_ops
->writepage(page
, &wbc
);
542 /* I/O Error writing */
545 if (rc
!= AOP_WRITEPAGE_ACTIVATE
)
546 /* unlocked. Relock */
553 * Default handling if a filesystem does not provide a migration function.
555 static int fallback_migrate_page(struct address_space
*mapping
,
556 struct page
*newpage
, struct page
*page
)
559 return writeout(mapping
, page
);
562 * Buffers may be managed in a filesystem specific way.
563 * We must have no buffers or drop them.
565 if (PagePrivate(page
) &&
566 !try_to_release_page(page
, GFP_KERNEL
))
569 return migrate_page(mapping
, newpage
, page
);
573 * Move a page to a newly allocated page
574 * The page is locked and all ptes have been successfully removed.
576 * The new page will have replaced the old page if this function
579 static int move_to_new_page(struct page
*newpage
, struct page
*page
)
581 struct address_space
*mapping
;
585 * Block others from accessing the page when we get around to
586 * establishing additional references. We are the only one
587 * holding a reference to the new page at this point.
589 if (TestSetPageLocked(newpage
))
592 /* Prepare mapping for the new page.*/
593 newpage
->index
= page
->index
;
594 newpage
->mapping
= page
->mapping
;
596 mapping
= page_mapping(page
);
598 rc
= migrate_page(mapping
, newpage
, page
);
599 else if (mapping
->a_ops
->migratepage
)
601 * Most pages have a mapping and most filesystems
602 * should provide a migration function. Anonymous
603 * pages are part of swap space which also has its
604 * own migration function. This is the most common
605 * path for page migration.
607 rc
= mapping
->a_ops
->migratepage(mapping
,
610 rc
= fallback_migrate_page(mapping
, newpage
, page
);
613 mem_cgroup_page_migration(page
, newpage
);
614 remove_migration_ptes(page
, newpage
);
616 newpage
->mapping
= NULL
;
618 unlock_page(newpage
);
624 * Obtain the lock on page, remove all ptes and migrate the page
625 * to the newly allocated page in newpage.
627 static int unmap_and_move(new_page_t get_new_page
, unsigned long private,
628 struct page
*page
, int force
)
632 struct page
*newpage
= get_new_page(page
, private, &result
);
639 if (page_count(page
) == 1)
640 /* page was freed from under us. So we are done. */
644 if (TestSetPageLocked(page
)) {
650 if (PageWriteback(page
)) {
653 wait_on_page_writeback(page
);
656 * By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
657 * we cannot notice that anon_vma is freed while we migrates a page.
658 * This rcu_read_lock() delays freeing anon_vma pointer until the end
659 * of migration. File cache pages are no problem because of page_lock()
660 * File Caches may use write_page() or lock_page() in migration, then,
661 * just care Anon page here.
663 if (PageAnon(page
)) {
669 * Corner case handling:
670 * 1. When a new swap-cache page is read into, it is added to the LRU
671 * and treated as swapcache but it has no rmap yet.
672 * Calling try_to_unmap() against a page->mapping==NULL page will
673 * trigger a BUG. So handle it here.
674 * 2. An orphaned page (see truncate_complete_page) might have
675 * fs-private metadata. The page can be picked up due to memory
676 * offlining. Everywhere else except page reclaim, the page is
677 * invisible to the vm, so the page can not be migrated. So try to
678 * free the metadata, so the page can be freed.
680 if (!page
->mapping
) {
681 if (!PageAnon(page
) && PagePrivate(page
)) {
683 * Go direct to try_to_free_buffers() here because
684 * a) that's what try_to_release_page() would do anyway
685 * b) we may be under rcu_read_lock() here, so we can't
686 * use GFP_KERNEL which is what try_to_release_page()
687 * needs to be effective.
689 try_to_free_buffers(page
);
694 charge
= mem_cgroup_prepare_migration(page
);
695 /* Establish migration ptes or remove ptes */
696 try_to_unmap(page
, 1);
698 if (!page_mapped(page
))
699 rc
= move_to_new_page(newpage
, page
);
702 remove_migration_ptes(page
, page
);
704 mem_cgroup_end_migration(page
);
706 mem_cgroup_end_migration(newpage
);
717 * A page that has been migrated has all references
718 * removed and will be freed. A page that has not been
719 * migrated will have kepts its references and be
722 list_del(&page
->lru
);
728 * Move the new page to the LRU. If migration was not successful
729 * then this will free the page.
731 move_to_lru(newpage
);
736 *result
= page_to_nid(newpage
);
744 * The function takes one list of pages to migrate and a function
745 * that determines from the page to be migrated and the private data
746 * the target of the move and allocates the page.
748 * The function returns after 10 attempts or if no pages
749 * are movable anymore because to has become empty
750 * or no retryable pages exist anymore. All pages will be
751 * returned to the LRU or freed.
753 * Return: Number of pages not migrated or error code.
755 int migrate_pages(struct list_head
*from
,
756 new_page_t get_new_page
, unsigned long private)
763 int swapwrite
= current
->flags
& PF_SWAPWRITE
;
767 current
->flags
|= PF_SWAPWRITE
;
769 for(pass
= 0; pass
< 10 && retry
; pass
++) {
772 list_for_each_entry_safe(page
, page2
, from
, lru
) {
775 rc
= unmap_and_move(get_new_page
, private,
787 /* Permanent failure */
796 current
->flags
&= ~PF_SWAPWRITE
;
798 putback_lru_pages(from
);
803 return nr_failed
+ retry
;
808 * Move a list of individual pages
810 struct page_to_node
{
817 static struct page
*new_page_node(struct page
*p
, unsigned long private,
820 struct page_to_node
*pm
= (struct page_to_node
*)private;
822 while (pm
->node
!= MAX_NUMNODES
&& pm
->page
!= p
)
825 if (pm
->node
== MAX_NUMNODES
)
828 *result
= &pm
->status
;
830 return alloc_pages_node(pm
->node
,
831 GFP_HIGHUSER_MOVABLE
| GFP_THISNODE
, 0);
835 * Move a set of pages as indicated in the pm array. The addr
836 * field must be set to the virtual address of the page to be moved
837 * and the node number must contain a valid target node.
839 static int do_move_pages(struct mm_struct
*mm
, struct page_to_node
*pm
,
843 struct page_to_node
*pp
;
846 down_read(&mm
->mmap_sem
);
849 * Build a list of pages to migrate
852 for (pp
= pm
; pp
->node
!= MAX_NUMNODES
; pp
++) {
853 struct vm_area_struct
*vma
;
857 * A valid page pointer that will not match any of the
858 * pages that will be moved.
860 pp
->page
= ZERO_PAGE(0);
863 vma
= find_vma(mm
, pp
->addr
);
864 if (!vma
|| !vma_migratable(vma
))
867 page
= follow_page(vma
, pp
->addr
, FOLL_GET
);
877 if (PageReserved(page
)) /* Check for zero page */
881 err
= page_to_nid(page
);
885 * Node already in the right place
890 if (page_mapcount(page
) > 1 &&
894 err
= isolate_lru_page(page
, &pagelist
);
897 * Either remove the duplicate refcount from
898 * isolate_lru_page() or drop the page ref if it was
906 if (!list_empty(&pagelist
))
907 err
= migrate_pages(&pagelist
, new_page_node
,
912 up_read(&mm
->mmap_sem
);
917 * Determine the nodes of a list of pages. The addr in the pm array
918 * must have been set to the virtual address of which we want to determine
921 static int do_pages_stat(struct mm_struct
*mm
, struct page_to_node
*pm
)
923 down_read(&mm
->mmap_sem
);
925 for ( ; pm
->node
!= MAX_NUMNODES
; pm
++) {
926 struct vm_area_struct
*vma
;
931 vma
= find_vma(mm
, pm
->addr
);
935 page
= follow_page(vma
, pm
->addr
, 0);
942 /* Use PageReserved to check for zero page */
943 if (!page
|| PageReserved(page
))
946 err
= page_to_nid(page
);
951 up_read(&mm
->mmap_sem
);
956 * Move a list of pages in the address space of the currently executing
959 asmlinkage
long sys_move_pages(pid_t pid
, unsigned long nr_pages
,
960 const void __user
* __user
*pages
,
961 const int __user
*nodes
,
962 int __user
*status
, int flags
)
966 struct task_struct
*task
;
967 nodemask_t task_nodes
;
968 struct mm_struct
*mm
;
969 struct page_to_node
*pm
= NULL
;
972 if (flags
& ~(MPOL_MF_MOVE
|MPOL_MF_MOVE_ALL
))
975 if ((flags
& MPOL_MF_MOVE_ALL
) && !capable(CAP_SYS_NICE
))
978 /* Find the mm_struct */
979 read_lock(&tasklist_lock
);
980 task
= pid
? find_task_by_vpid(pid
) : current
;
982 read_unlock(&tasklist_lock
);
985 mm
= get_task_mm(task
);
986 read_unlock(&tasklist_lock
);
992 * Check if this process has the right to modify the specified
993 * process. The right exists if the process has administrative
994 * capabilities, superuser privileges or the same
995 * userid as the target process.
997 if ((current
->euid
!= task
->suid
) && (current
->euid
!= task
->uid
) &&
998 (current
->uid
!= task
->suid
) && (current
->uid
!= task
->uid
) &&
999 !capable(CAP_SYS_NICE
)) {
1004 err
= security_task_movememory(task
);
1009 task_nodes
= cpuset_mems_allowed(task
);
1011 /* Limit nr_pages so that the multiplication may not overflow */
1012 if (nr_pages
>= ULONG_MAX
/ sizeof(struct page_to_node
) - 1) {
1017 pm
= vmalloc((nr_pages
+ 1) * sizeof(struct page_to_node
));
1024 * Get parameters from user space and initialize the pm
1025 * array. Return various errors if the user did something wrong.
1027 for (i
= 0; i
< nr_pages
; i
++) {
1028 const void __user
*p
;
1031 if (get_user(p
, pages
+ i
))
1034 pm
[i
].addr
= (unsigned long)p
;
1038 if (get_user(node
, nodes
+ i
))
1042 if (!node_state(node
, N_HIGH_MEMORY
))
1046 if (!node_isset(node
, task_nodes
))
1051 pm
[i
].node
= 0; /* anything to not match MAX_NUMNODES */
1054 pm
[nr_pages
].node
= MAX_NUMNODES
;
1057 err
= do_move_pages(mm
, pm
, flags
& MPOL_MF_MOVE_ALL
);
1059 err
= do_pages_stat(mm
, pm
);
1062 /* Return status information */
1063 for (i
= 0; i
< nr_pages
; i
++)
1064 if (put_user(pm
[i
].status
, status
+ i
))
1076 * Call migration functions in the vma_ops that may prepare
1077 * memory in a vm for migration. migration functions may perform
1078 * the migration for vmas that do not have an underlying page struct.
1080 int migrate_vmas(struct mm_struct
*mm
, const nodemask_t
*to
,
1081 const nodemask_t
*from
, unsigned long flags
)
1083 struct vm_area_struct
*vma
;
1086 for(vma
= mm
->mmap
; vma
->vm_next
&& !err
; vma
= vma
->vm_next
) {
1087 if (vma
->vm_ops
&& vma
->vm_ops
->migrate
) {
1088 err
= vma
->vm_ops
->migrate(vma
, to
, from
, flags
);
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