]>
git.proxmox.com Git - mirror_ubuntu-bionic-kernel.git/blob - mm/migrate.c
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>
33 #include <linux/syscalls.h>
37 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
40 * migrate_prep() needs to be called before we start compiling a list of pages
41 * to be migrated using isolate_lru_page().
43 int migrate_prep(void)
46 * Clear the LRU lists so pages can be isolated.
47 * Note that pages may be moved off the LRU after we have
48 * drained them. Those pages will fail to migrate like other
49 * pages that may be busy.
56 static inline void move_to_lru(struct page
*page
)
58 lru_cache_add_lru(page
, page_lru(page
));
63 * Add isolated pages on the list back to the LRU.
65 * returns the number of pages put back.
67 int putback_lru_pages(struct list_head
*l
)
73 list_for_each_entry_safe(page
, page2
, l
, lru
) {
82 * Restore a potential migration pte to a working pte entry
84 static void remove_migration_pte(struct vm_area_struct
*vma
,
85 struct page
*old
, struct page
*new)
87 struct mm_struct
*mm
= vma
->vm_mm
;
94 unsigned long addr
= page_address_in_vma(new, vma
);
99 pgd
= pgd_offset(mm
, addr
);
100 if (!pgd_present(*pgd
))
103 pud
= pud_offset(pgd
, addr
);
104 if (!pud_present(*pud
))
107 pmd
= pmd_offset(pud
, addr
);
108 if (!pmd_present(*pmd
))
111 ptep
= pte_offset_map(pmd
, addr
);
113 if (!is_swap_pte(*ptep
)) {
118 ptl
= pte_lockptr(mm
, pmd
);
121 if (!is_swap_pte(pte
))
124 entry
= pte_to_swp_entry(pte
);
126 if (!is_migration_entry(entry
) || migration_entry_to_page(entry
) != old
)
130 * Yes, ignore the return value from a GFP_ATOMIC mem_cgroup_charge.
131 * Failure is not an option here: we're now expected to remove every
132 * migration pte, and will cause crashes otherwise. Normally this
133 * is not an issue: mem_cgroup_prepare_migration bumped up the old
134 * page_cgroup count for safety, that's now attached to the new page,
135 * so this charge should just be another incrementation of the count,
136 * to keep in balance with rmap.c's mem_cgroup_uncharging. But if
137 * there's been a force_empty, those reference counts may no longer
138 * be reliable, and this charge can actually fail: oh well, we don't
139 * make the situation any worse by proceeding as if it had succeeded.
141 mem_cgroup_charge(new, mm
, GFP_ATOMIC
);
144 pte
= pte_mkold(mk_pte(new, vma
->vm_page_prot
));
145 if (is_write_migration_entry(entry
))
146 pte
= pte_mkwrite(pte
);
147 flush_cache_page(vma
, addr
, pte_pfn(pte
));
148 set_pte_at(mm
, addr
, ptep
, pte
);
151 page_add_anon_rmap(new, vma
, addr
);
153 page_add_file_rmap(new);
155 /* No need to invalidate - it was non-present before */
156 update_mmu_cache(vma
, addr
, pte
);
159 pte_unmap_unlock(ptep
, ptl
);
163 * Note that remove_file_migration_ptes will only work on regular mappings,
164 * Nonlinear mappings do not use migration entries.
166 static void remove_file_migration_ptes(struct page
*old
, struct page
*new)
168 struct vm_area_struct
*vma
;
169 struct address_space
*mapping
= page_mapping(new);
170 struct prio_tree_iter iter
;
171 pgoff_t pgoff
= new->index
<< (PAGE_CACHE_SHIFT
- PAGE_SHIFT
);
176 spin_lock(&mapping
->i_mmap_lock
);
178 vma_prio_tree_foreach(vma
, &iter
, &mapping
->i_mmap
, pgoff
, pgoff
)
179 remove_migration_pte(vma
, old
, new);
181 spin_unlock(&mapping
->i_mmap_lock
);
185 * Must hold mmap_sem lock on at least one of the vmas containing
186 * the page so that the anon_vma cannot vanish.
188 static void remove_anon_migration_ptes(struct page
*old
, struct page
*new)
190 struct anon_vma
*anon_vma
;
191 struct vm_area_struct
*vma
;
192 unsigned long mapping
;
194 mapping
= (unsigned long)new->mapping
;
196 if (!mapping
|| (mapping
& PAGE_MAPPING_ANON
) == 0)
200 * We hold the mmap_sem lock. So no need to call page_lock_anon_vma.
202 anon_vma
= (struct anon_vma
*) (mapping
- PAGE_MAPPING_ANON
);
203 spin_lock(&anon_vma
->lock
);
205 list_for_each_entry(vma
, &anon_vma
->head
, anon_vma_node
)
206 remove_migration_pte(vma
, old
, new);
208 spin_unlock(&anon_vma
->lock
);
212 * Get rid of all migration entries and replace them by
213 * references to the indicated page.
215 static void remove_migration_ptes(struct page
*old
, struct page
*new)
218 remove_anon_migration_ptes(old
, new);
220 remove_file_migration_ptes(old
, new);
224 * Something used the pte of a page under migration. We need to
225 * get to the page and wait until migration is finished.
226 * When we return from this function the fault will be retried.
228 * This function is called from do_swap_page().
230 void migration_entry_wait(struct mm_struct
*mm
, pmd_t
*pmd
,
231 unsigned long address
)
238 ptep
= pte_offset_map_lock(mm
, pmd
, address
, &ptl
);
240 if (!is_swap_pte(pte
))
243 entry
= pte_to_swp_entry(pte
);
244 if (!is_migration_entry(entry
))
247 page
= migration_entry_to_page(entry
);
250 * Once radix-tree replacement of page migration started, page_count
251 * *must* be zero. And, we don't want to call wait_on_page_locked()
252 * against a page without get_page().
253 * So, we use get_page_unless_zero(), here. Even failed, page fault
256 if (!get_page_unless_zero(page
))
258 pte_unmap_unlock(ptep
, ptl
);
259 wait_on_page_locked(page
);
263 pte_unmap_unlock(ptep
, ptl
);
267 * Replace the page in the mapping.
269 * The number of remaining references must be:
270 * 1 for anonymous pages without a mapping
271 * 2 for pages with a mapping
272 * 3 for pages with a mapping and PagePrivate set.
274 static int migrate_page_move_mapping(struct address_space
*mapping
,
275 struct page
*newpage
, struct page
*page
)
281 /* Anonymous page without mapping */
282 if (page_count(page
) != 1)
287 spin_lock_irq(&mapping
->tree_lock
);
289 pslot
= radix_tree_lookup_slot(&mapping
->page_tree
,
292 expected_count
= 2 + !!PagePrivate(page
);
293 if (page_count(page
) != expected_count
||
294 (struct page
*)radix_tree_deref_slot(pslot
) != page
) {
295 spin_unlock_irq(&mapping
->tree_lock
);
299 if (!page_freeze_refs(page
, expected_count
)) {
300 spin_unlock_irq(&mapping
->tree_lock
);
305 * Now we know that no one else is looking at the page.
307 get_page(newpage
); /* add cache reference */
309 if (PageSwapCache(page
)) {
310 SetPageSwapCache(newpage
);
311 set_page_private(newpage
, page_private(page
));
315 radix_tree_replace_slot(pslot
, newpage
);
317 page_unfreeze_refs(page
, expected_count
);
319 * Drop cache reference from old page.
320 * We know this isn't the last reference.
325 * If moved to a different zone then also account
326 * the page for that zone. Other VM counters will be
327 * taken care of when we establish references to the
328 * new page and drop references to the old page.
330 * Note that anonymous pages are accounted for
331 * via NR_FILE_PAGES and NR_ANON_PAGES if they
332 * are mapped to swap space.
334 __dec_zone_page_state(page
, NR_FILE_PAGES
);
335 __inc_zone_page_state(newpage
, NR_FILE_PAGES
);
337 spin_unlock_irq(&mapping
->tree_lock
);
338 if (!PageSwapCache(newpage
))
339 mem_cgroup_uncharge_cache_page(page
);
345 * Copy the page to its new location
347 static void migrate_page_copy(struct page
*newpage
, struct page
*page
)
349 copy_highpage(newpage
, page
);
352 SetPageError(newpage
);
353 if (PageReferenced(page
))
354 SetPageReferenced(newpage
);
355 if (PageUptodate(page
))
356 SetPageUptodate(newpage
);
357 if (PageActive(page
))
358 SetPageActive(newpage
);
359 if (PageChecked(page
))
360 SetPageChecked(newpage
);
361 if (PageMappedToDisk(page
))
362 SetPageMappedToDisk(newpage
);
364 if (PageDirty(page
)) {
365 clear_page_dirty_for_io(page
);
367 * Want to mark the page and the radix tree as dirty, and
368 * redo the accounting that clear_page_dirty_for_io undid,
369 * but we can't use set_page_dirty because that function
370 * is actually a signal that all of the page has become dirty.
371 * Wheras only part of our page may be dirty.
373 __set_page_dirty_nobuffers(newpage
);
377 ClearPageSwapCache(page
);
379 ClearPageActive(page
);
380 ClearPagePrivate(page
);
381 set_page_private(page
, 0);
382 page
->mapping
= NULL
;
385 * If any waiters have accumulated on the new page then
388 if (PageWriteback(newpage
))
389 end_page_writeback(newpage
);
392 /************************************************************
393 * Migration functions
394 ***********************************************************/
396 /* Always fail migration. Used for mappings that are not movable */
397 int fail_migrate_page(struct address_space
*mapping
,
398 struct page
*newpage
, struct page
*page
)
402 EXPORT_SYMBOL(fail_migrate_page
);
405 * Common logic to directly migrate a single page suitable for
406 * pages that do not use PagePrivate.
408 * Pages are locked upon entry and exit.
410 int migrate_page(struct address_space
*mapping
,
411 struct page
*newpage
, struct page
*page
)
415 BUG_ON(PageWriteback(page
)); /* Writeback must be complete */
417 rc
= migrate_page_move_mapping(mapping
, newpage
, page
);
422 migrate_page_copy(newpage
, page
);
425 EXPORT_SYMBOL(migrate_page
);
429 * Migration function for pages with buffers. This function can only be used
430 * if the underlying filesystem guarantees that no other references to "page"
433 int buffer_migrate_page(struct address_space
*mapping
,
434 struct page
*newpage
, struct page
*page
)
436 struct buffer_head
*bh
, *head
;
439 if (!page_has_buffers(page
))
440 return migrate_page(mapping
, newpage
, page
);
442 head
= page_buffers(page
);
444 rc
= migrate_page_move_mapping(mapping
, newpage
, page
);
453 bh
= bh
->b_this_page
;
455 } while (bh
!= head
);
457 ClearPagePrivate(page
);
458 set_page_private(newpage
, page_private(page
));
459 set_page_private(page
, 0);
465 set_bh_page(bh
, newpage
, bh_offset(bh
));
466 bh
= bh
->b_this_page
;
468 } while (bh
!= head
);
470 SetPagePrivate(newpage
);
472 migrate_page_copy(newpage
, page
);
478 bh
= bh
->b_this_page
;
480 } while (bh
!= head
);
484 EXPORT_SYMBOL(buffer_migrate_page
);
488 * Writeback a page to clean the dirty state
490 static int writeout(struct address_space
*mapping
, struct page
*page
)
492 struct writeback_control wbc
= {
493 .sync_mode
= WB_SYNC_NONE
,
496 .range_end
= LLONG_MAX
,
502 if (!mapping
->a_ops
->writepage
)
503 /* No write method for the address space */
506 if (!clear_page_dirty_for_io(page
))
507 /* Someone else already triggered a write */
511 * A dirty page may imply that the underlying filesystem has
512 * the page on some queue. So the page must be clean for
513 * migration. Writeout may mean we loose the lock and the
514 * page state is no longer what we checked for earlier.
515 * At this point we know that the migration attempt cannot
518 remove_migration_ptes(page
, page
);
520 rc
= mapping
->a_ops
->writepage(page
, &wbc
);
522 /* I/O Error writing */
525 if (rc
!= AOP_WRITEPAGE_ACTIVATE
)
526 /* unlocked. Relock */
533 * Default handling if a filesystem does not provide a migration function.
535 static int fallback_migrate_page(struct address_space
*mapping
,
536 struct page
*newpage
, struct page
*page
)
539 return writeout(mapping
, page
);
542 * Buffers may be managed in a filesystem specific way.
543 * We must have no buffers or drop them.
545 if (PagePrivate(page
) &&
546 !try_to_release_page(page
, GFP_KERNEL
))
549 return migrate_page(mapping
, newpage
, page
);
553 * Move a page to a newly allocated page
554 * The page is locked and all ptes have been successfully removed.
556 * The new page will have replaced the old page if this function
559 static int move_to_new_page(struct page
*newpage
, struct page
*page
)
561 struct address_space
*mapping
;
565 * Block others from accessing the page when we get around to
566 * establishing additional references. We are the only one
567 * holding a reference to the new page at this point.
569 if (!trylock_page(newpage
))
572 /* Prepare mapping for the new page.*/
573 newpage
->index
= page
->index
;
574 newpage
->mapping
= page
->mapping
;
576 mapping
= page_mapping(page
);
578 rc
= migrate_page(mapping
, newpage
, page
);
579 else if (mapping
->a_ops
->migratepage
)
581 * Most pages have a mapping and most filesystems
582 * should provide a migration function. Anonymous
583 * pages are part of swap space which also has its
584 * own migration function. This is the most common
585 * path for page migration.
587 rc
= mapping
->a_ops
->migratepage(mapping
,
590 rc
= fallback_migrate_page(mapping
, newpage
, page
);
593 remove_migration_ptes(page
, newpage
);
595 newpage
->mapping
= NULL
;
597 unlock_page(newpage
);
603 * Obtain the lock on page, remove all ptes and migrate the page
604 * to the newly allocated page in newpage.
606 static int unmap_and_move(new_page_t get_new_page
, unsigned long private,
607 struct page
*page
, int force
)
611 struct page
*newpage
= get_new_page(page
, private, &result
);
618 if (page_count(page
) == 1)
619 /* page was freed from under us. So we are done. */
622 charge
= mem_cgroup_prepare_migration(page
, newpage
);
623 if (charge
== -ENOMEM
) {
627 /* prepare cgroup just returns 0 or -ENOMEM */
631 if (!trylock_page(page
)) {
637 if (PageWriteback(page
)) {
640 wait_on_page_writeback(page
);
643 * By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
644 * we cannot notice that anon_vma is freed while we migrates a page.
645 * This rcu_read_lock() delays freeing anon_vma pointer until the end
646 * of migration. File cache pages are no problem because of page_lock()
647 * File Caches may use write_page() or lock_page() in migration, then,
648 * just care Anon page here.
650 if (PageAnon(page
)) {
656 * Corner case handling:
657 * 1. When a new swap-cache page is read into, it is added to the LRU
658 * and treated as swapcache but it has no rmap yet.
659 * Calling try_to_unmap() against a page->mapping==NULL page will
660 * trigger a BUG. So handle it here.
661 * 2. An orphaned page (see truncate_complete_page) might have
662 * fs-private metadata. The page can be picked up due to memory
663 * offlining. Everywhere else except page reclaim, the page is
664 * invisible to the vm, so the page can not be migrated. So try to
665 * free the metadata, so the page can be freed.
667 if (!page
->mapping
) {
668 if (!PageAnon(page
) && PagePrivate(page
)) {
670 * Go direct to try_to_free_buffers() here because
671 * a) that's what try_to_release_page() would do anyway
672 * b) we may be under rcu_read_lock() here, so we can't
673 * use GFP_KERNEL which is what try_to_release_page()
674 * needs to be effective.
676 try_to_free_buffers(page
);
681 /* Establish migration ptes or remove ptes */
682 try_to_unmap(page
, 1);
684 if (!page_mapped(page
))
685 rc
= move_to_new_page(newpage
, page
);
688 remove_migration_ptes(page
, page
);
699 * A page that has been migrated has all references
700 * removed and will be freed. A page that has not been
701 * migrated will have kepts its references and be
704 list_del(&page
->lru
);
710 mem_cgroup_end_migration(newpage
);
712 * Move the new page to the LRU. If migration was not successful
713 * then this will free the page.
715 move_to_lru(newpage
);
720 *result
= page_to_nid(newpage
);
728 * The function takes one list of pages to migrate and a function
729 * that determines from the page to be migrated and the private data
730 * the target of the move and allocates the page.
732 * The function returns after 10 attempts or if no pages
733 * are movable anymore because to has become empty
734 * or no retryable pages exist anymore. All pages will be
735 * returned to the LRU or freed.
737 * Return: Number of pages not migrated or error code.
739 int migrate_pages(struct list_head
*from
,
740 new_page_t get_new_page
, unsigned long private)
747 int swapwrite
= current
->flags
& PF_SWAPWRITE
;
751 current
->flags
|= PF_SWAPWRITE
;
753 for(pass
= 0; pass
< 10 && retry
; pass
++) {
756 list_for_each_entry_safe(page
, page2
, from
, lru
) {
759 rc
= unmap_and_move(get_new_page
, private,
771 /* Permanent failure */
780 current
->flags
&= ~PF_SWAPWRITE
;
782 putback_lru_pages(from
);
787 return nr_failed
+ retry
;
792 * Move a list of individual pages
794 struct page_to_node
{
801 static struct page
*new_page_node(struct page
*p
, unsigned long private,
804 struct page_to_node
*pm
= (struct page_to_node
*)private;
806 while (pm
->node
!= MAX_NUMNODES
&& pm
->page
!= p
)
809 if (pm
->node
== MAX_NUMNODES
)
812 *result
= &pm
->status
;
814 return alloc_pages_node(pm
->node
,
815 GFP_HIGHUSER_MOVABLE
| GFP_THISNODE
, 0);
819 * Move a set of pages as indicated in the pm array. The addr
820 * field must be set to the virtual address of the page to be moved
821 * and the node number must contain a valid target node.
823 static int do_move_pages(struct mm_struct
*mm
, struct page_to_node
*pm
,
827 struct page_to_node
*pp
;
830 down_read(&mm
->mmap_sem
);
833 * Build a list of pages to migrate
836 for (pp
= pm
; pp
->node
!= MAX_NUMNODES
; pp
++) {
837 struct vm_area_struct
*vma
;
841 * A valid page pointer that will not match any of the
842 * pages that will be moved.
844 pp
->page
= ZERO_PAGE(0);
847 vma
= find_vma(mm
, pp
->addr
);
848 if (!vma
|| !vma_migratable(vma
))
851 page
= follow_page(vma
, pp
->addr
, FOLL_GET
);
861 if (PageReserved(page
)) /* Check for zero page */
865 err
= page_to_nid(page
);
869 * Node already in the right place
874 if (page_mapcount(page
) > 1 &&
878 err
= isolate_lru_page(page
);
880 list_add_tail(&page
->lru
, &pagelist
);
883 * Either remove the duplicate refcount from
884 * isolate_lru_page() or drop the page ref if it was
892 if (!list_empty(&pagelist
))
893 err
= migrate_pages(&pagelist
, new_page_node
,
898 up_read(&mm
->mmap_sem
);
903 * Determine the nodes of a list of pages. The addr in the pm array
904 * must have been set to the virtual address of which we want to determine
907 static int do_pages_stat(struct mm_struct
*mm
, struct page_to_node
*pm
)
909 down_read(&mm
->mmap_sem
);
911 for ( ; pm
->node
!= MAX_NUMNODES
; pm
++) {
912 struct vm_area_struct
*vma
;
917 vma
= find_vma(mm
, pm
->addr
);
921 page
= follow_page(vma
, pm
->addr
, 0);
928 /* Use PageReserved to check for zero page */
929 if (!page
|| PageReserved(page
))
932 err
= page_to_nid(page
);
937 up_read(&mm
->mmap_sem
);
942 * Move a list of pages in the address space of the currently executing
945 asmlinkage
long sys_move_pages(pid_t pid
, unsigned long nr_pages
,
946 const void __user
* __user
*pages
,
947 const int __user
*nodes
,
948 int __user
*status
, int flags
)
952 struct task_struct
*task
;
953 nodemask_t task_nodes
;
954 struct mm_struct
*mm
;
955 struct page_to_node
*pm
= NULL
;
958 if (flags
& ~(MPOL_MF_MOVE
|MPOL_MF_MOVE_ALL
))
961 if ((flags
& MPOL_MF_MOVE_ALL
) && !capable(CAP_SYS_NICE
))
964 /* Find the mm_struct */
965 read_lock(&tasklist_lock
);
966 task
= pid
? find_task_by_vpid(pid
) : current
;
968 read_unlock(&tasklist_lock
);
971 mm
= get_task_mm(task
);
972 read_unlock(&tasklist_lock
);
978 * Check if this process has the right to modify the specified
979 * process. The right exists if the process has administrative
980 * capabilities, superuser privileges or the same
981 * userid as the target process.
983 if ((current
->euid
!= task
->suid
) && (current
->euid
!= task
->uid
) &&
984 (current
->uid
!= task
->suid
) && (current
->uid
!= task
->uid
) &&
985 !capable(CAP_SYS_NICE
)) {
990 err
= security_task_movememory(task
);
995 task_nodes
= cpuset_mems_allowed(task
);
997 /* Limit nr_pages so that the multiplication may not overflow */
998 if (nr_pages
>= ULONG_MAX
/ sizeof(struct page_to_node
) - 1) {
1003 pm
= vmalloc((nr_pages
+ 1) * sizeof(struct page_to_node
));
1010 * Get parameters from user space and initialize the pm
1011 * array. Return various errors if the user did something wrong.
1013 for (i
= 0; i
< nr_pages
; i
++) {
1014 const void __user
*p
;
1017 if (get_user(p
, pages
+ i
))
1020 pm
[i
].addr
= (unsigned long)p
;
1024 if (get_user(node
, nodes
+ i
))
1028 if (!node_state(node
, N_HIGH_MEMORY
))
1032 if (!node_isset(node
, task_nodes
))
1037 pm
[i
].node
= 0; /* anything to not match MAX_NUMNODES */
1040 pm
[nr_pages
].node
= MAX_NUMNODES
;
1043 err
= do_move_pages(mm
, pm
, flags
& MPOL_MF_MOVE_ALL
);
1045 err
= do_pages_stat(mm
, pm
);
1048 /* Return status information */
1049 for (i
= 0; i
< nr_pages
; i
++)
1050 if (put_user(pm
[i
].status
, status
+ i
))
1061 * Call migration functions in the vma_ops that may prepare
1062 * memory in a vm for migration. migration functions may perform
1063 * the migration for vmas that do not have an underlying page struct.
1065 int migrate_vmas(struct mm_struct
*mm
, const nodemask_t
*to
,
1066 const nodemask_t
*from
, unsigned long flags
)
1068 struct vm_area_struct
*vma
;
1071 for(vma
= mm
->mmap
; vma
->vm_next
&& !err
; vma
= vma
->vm_next
) {
1072 if (vma
->vm_ops
&& vma
->vm_ops
->migrate
) {
1073 err
= vma
->vm_ops
->migrate(vma
, to
, from
, flags
);