Linux 3.8-rc7
[cris-mirror.git] / mm / migrate.c
blob2fd8b4af47440a39a31d48a1096e24b571028455
1 /*
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>
12 * Christoph Lameter
15 #include <linux/migrate.h>
16 #include <linux/export.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/ksm.h>
25 #include <linux/rmap.h>
26 #include <linux/topology.h>
27 #include <linux/cpu.h>
28 #include <linux/cpuset.h>
29 #include <linux/writeback.h>
30 #include <linux/mempolicy.h>
31 #include <linux/vmalloc.h>
32 #include <linux/security.h>
33 #include <linux/memcontrol.h>
34 #include <linux/syscalls.h>
35 #include <linux/hugetlb.h>
36 #include <linux/hugetlb_cgroup.h>
37 #include <linux/gfp.h>
38 #include <linux/balloon_compaction.h>
40 #include <asm/tlbflush.h>
42 #define CREATE_TRACE_POINTS
43 #include <trace/events/migrate.h>
45 #include "internal.h"
48 * migrate_prep() needs to be called before we start compiling a list of pages
49 * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
50 * undesirable, use migrate_prep_local()
52 int migrate_prep(void)
55 * Clear the LRU lists so pages can be isolated.
56 * Note that pages may be moved off the LRU after we have
57 * drained them. Those pages will fail to migrate like other
58 * pages that may be busy.
60 lru_add_drain_all();
62 return 0;
65 /* Do the necessary work of migrate_prep but not if it involves other CPUs */
66 int migrate_prep_local(void)
68 lru_add_drain();
70 return 0;
74 * Add isolated pages on the list back to the LRU under page lock
75 * to avoid leaking evictable pages back onto unevictable list.
77 void putback_lru_pages(struct list_head *l)
79 struct page *page;
80 struct page *page2;
82 list_for_each_entry_safe(page, page2, l, lru) {
83 list_del(&page->lru);
84 dec_zone_page_state(page, NR_ISOLATED_ANON +
85 page_is_file_cache(page));
86 putback_lru_page(page);
91 * Put previously isolated pages back onto the appropriate lists
92 * from where they were once taken off for compaction/migration.
94 * This function shall be used instead of putback_lru_pages(),
95 * whenever the isolated pageset has been built by isolate_migratepages_range()
97 void putback_movable_pages(struct list_head *l)
99 struct page *page;
100 struct page *page2;
102 list_for_each_entry_safe(page, page2, l, lru) {
103 list_del(&page->lru);
104 dec_zone_page_state(page, NR_ISOLATED_ANON +
105 page_is_file_cache(page));
106 if (unlikely(balloon_page_movable(page)))
107 balloon_page_putback(page);
108 else
109 putback_lru_page(page);
114 * Restore a potential migration pte to a working pte entry
116 static int remove_migration_pte(struct page *new, struct vm_area_struct *vma,
117 unsigned long addr, void *old)
119 struct mm_struct *mm = vma->vm_mm;
120 swp_entry_t entry;
121 pmd_t *pmd;
122 pte_t *ptep, pte;
123 spinlock_t *ptl;
125 if (unlikely(PageHuge(new))) {
126 ptep = huge_pte_offset(mm, addr);
127 if (!ptep)
128 goto out;
129 ptl = &mm->page_table_lock;
130 } else {
131 pmd = mm_find_pmd(mm, addr);
132 if (!pmd)
133 goto out;
134 if (pmd_trans_huge(*pmd))
135 goto out;
137 ptep = pte_offset_map(pmd, addr);
140 * Peek to check is_swap_pte() before taking ptlock? No, we
141 * can race mremap's move_ptes(), which skips anon_vma lock.
144 ptl = pte_lockptr(mm, pmd);
147 spin_lock(ptl);
148 pte = *ptep;
149 if (!is_swap_pte(pte))
150 goto unlock;
152 entry = pte_to_swp_entry(pte);
154 if (!is_migration_entry(entry) ||
155 migration_entry_to_page(entry) != old)
156 goto unlock;
158 get_page(new);
159 pte = pte_mkold(mk_pte(new, vma->vm_page_prot));
160 if (is_write_migration_entry(entry))
161 pte = pte_mkwrite(pte);
162 #ifdef CONFIG_HUGETLB_PAGE
163 if (PageHuge(new)) {
164 pte = pte_mkhuge(pte);
165 pte = arch_make_huge_pte(pte, vma, new, 0);
167 #endif
168 flush_cache_page(vma, addr, pte_pfn(pte));
169 set_pte_at(mm, addr, ptep, pte);
171 if (PageHuge(new)) {
172 if (PageAnon(new))
173 hugepage_add_anon_rmap(new, vma, addr);
174 else
175 page_dup_rmap(new);
176 } else if (PageAnon(new))
177 page_add_anon_rmap(new, vma, addr);
178 else
179 page_add_file_rmap(new);
181 /* No need to invalidate - it was non-present before */
182 update_mmu_cache(vma, addr, ptep);
183 unlock:
184 pte_unmap_unlock(ptep, ptl);
185 out:
186 return SWAP_AGAIN;
190 * Get rid of all migration entries and replace them by
191 * references to the indicated page.
193 static void remove_migration_ptes(struct page *old, struct page *new)
195 rmap_walk(new, remove_migration_pte, old);
199 * Something used the pte of a page under migration. We need to
200 * get to the page and wait until migration is finished.
201 * When we return from this function the fault will be retried.
203 void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
204 unsigned long address)
206 pte_t *ptep, pte;
207 spinlock_t *ptl;
208 swp_entry_t entry;
209 struct page *page;
211 ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
212 pte = *ptep;
213 if (!is_swap_pte(pte))
214 goto out;
216 entry = pte_to_swp_entry(pte);
217 if (!is_migration_entry(entry))
218 goto out;
220 page = migration_entry_to_page(entry);
223 * Once radix-tree replacement of page migration started, page_count
224 * *must* be zero. And, we don't want to call wait_on_page_locked()
225 * against a page without get_page().
226 * So, we use get_page_unless_zero(), here. Even failed, page fault
227 * will occur again.
229 if (!get_page_unless_zero(page))
230 goto out;
231 pte_unmap_unlock(ptep, ptl);
232 wait_on_page_locked(page);
233 put_page(page);
234 return;
235 out:
236 pte_unmap_unlock(ptep, ptl);
239 #ifdef CONFIG_BLOCK
240 /* Returns true if all buffers are successfully locked */
241 static bool buffer_migrate_lock_buffers(struct buffer_head *head,
242 enum migrate_mode mode)
244 struct buffer_head *bh = head;
246 /* Simple case, sync compaction */
247 if (mode != MIGRATE_ASYNC) {
248 do {
249 get_bh(bh);
250 lock_buffer(bh);
251 bh = bh->b_this_page;
253 } while (bh != head);
255 return true;
258 /* async case, we cannot block on lock_buffer so use trylock_buffer */
259 do {
260 get_bh(bh);
261 if (!trylock_buffer(bh)) {
263 * We failed to lock the buffer and cannot stall in
264 * async migration. Release the taken locks
266 struct buffer_head *failed_bh = bh;
267 put_bh(failed_bh);
268 bh = head;
269 while (bh != failed_bh) {
270 unlock_buffer(bh);
271 put_bh(bh);
272 bh = bh->b_this_page;
274 return false;
277 bh = bh->b_this_page;
278 } while (bh != head);
279 return true;
281 #else
282 static inline bool buffer_migrate_lock_buffers(struct buffer_head *head,
283 enum migrate_mode mode)
285 return true;
287 #endif /* CONFIG_BLOCK */
290 * Replace the page in the mapping.
292 * The number of remaining references must be:
293 * 1 for anonymous pages without a mapping
294 * 2 for pages with a mapping
295 * 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
297 static int migrate_page_move_mapping(struct address_space *mapping,
298 struct page *newpage, struct page *page,
299 struct buffer_head *head, enum migrate_mode mode)
301 int expected_count = 0;
302 void **pslot;
304 if (!mapping) {
305 /* Anonymous page without mapping */
306 if (page_count(page) != 1)
307 return -EAGAIN;
308 return MIGRATEPAGE_SUCCESS;
311 spin_lock_irq(&mapping->tree_lock);
313 pslot = radix_tree_lookup_slot(&mapping->page_tree,
314 page_index(page));
316 expected_count = 2 + page_has_private(page);
317 if (page_count(page) != expected_count ||
318 radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {
319 spin_unlock_irq(&mapping->tree_lock);
320 return -EAGAIN;
323 if (!page_freeze_refs(page, expected_count)) {
324 spin_unlock_irq(&mapping->tree_lock);
325 return -EAGAIN;
329 * In the async migration case of moving a page with buffers, lock the
330 * buffers using trylock before the mapping is moved. If the mapping
331 * was moved, we later failed to lock the buffers and could not move
332 * the mapping back due to an elevated page count, we would have to
333 * block waiting on other references to be dropped.
335 if (mode == MIGRATE_ASYNC && head &&
336 !buffer_migrate_lock_buffers(head, mode)) {
337 page_unfreeze_refs(page, expected_count);
338 spin_unlock_irq(&mapping->tree_lock);
339 return -EAGAIN;
343 * Now we know that no one else is looking at the page.
345 get_page(newpage); /* add cache reference */
346 if (PageSwapCache(page)) {
347 SetPageSwapCache(newpage);
348 set_page_private(newpage, page_private(page));
351 radix_tree_replace_slot(pslot, newpage);
354 * Drop cache reference from old page by unfreezing
355 * to one less reference.
356 * We know this isn't the last reference.
358 page_unfreeze_refs(page, expected_count - 1);
361 * If moved to a different zone then also account
362 * the page for that zone. Other VM counters will be
363 * taken care of when we establish references to the
364 * new page and drop references to the old page.
366 * Note that anonymous pages are accounted for
367 * via NR_FILE_PAGES and NR_ANON_PAGES if they
368 * are mapped to swap space.
370 __dec_zone_page_state(page, NR_FILE_PAGES);
371 __inc_zone_page_state(newpage, NR_FILE_PAGES);
372 if (!PageSwapCache(page) && PageSwapBacked(page)) {
373 __dec_zone_page_state(page, NR_SHMEM);
374 __inc_zone_page_state(newpage, NR_SHMEM);
376 spin_unlock_irq(&mapping->tree_lock);
378 return MIGRATEPAGE_SUCCESS;
382 * The expected number of remaining references is the same as that
383 * of migrate_page_move_mapping().
385 int migrate_huge_page_move_mapping(struct address_space *mapping,
386 struct page *newpage, struct page *page)
388 int expected_count;
389 void **pslot;
391 if (!mapping) {
392 if (page_count(page) != 1)
393 return -EAGAIN;
394 return MIGRATEPAGE_SUCCESS;
397 spin_lock_irq(&mapping->tree_lock);
399 pslot = radix_tree_lookup_slot(&mapping->page_tree,
400 page_index(page));
402 expected_count = 2 + page_has_private(page);
403 if (page_count(page) != expected_count ||
404 radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {
405 spin_unlock_irq(&mapping->tree_lock);
406 return -EAGAIN;
409 if (!page_freeze_refs(page, expected_count)) {
410 spin_unlock_irq(&mapping->tree_lock);
411 return -EAGAIN;
414 get_page(newpage);
416 radix_tree_replace_slot(pslot, newpage);
418 page_unfreeze_refs(page, expected_count - 1);
420 spin_unlock_irq(&mapping->tree_lock);
421 return MIGRATEPAGE_SUCCESS;
425 * Copy the page to its new location
427 void migrate_page_copy(struct page *newpage, struct page *page)
429 if (PageHuge(page) || PageTransHuge(page))
430 copy_huge_page(newpage, page);
431 else
432 copy_highpage(newpage, page);
434 if (PageError(page))
435 SetPageError(newpage);
436 if (PageReferenced(page))
437 SetPageReferenced(newpage);
438 if (PageUptodate(page))
439 SetPageUptodate(newpage);
440 if (TestClearPageActive(page)) {
441 VM_BUG_ON(PageUnevictable(page));
442 SetPageActive(newpage);
443 } else if (TestClearPageUnevictable(page))
444 SetPageUnevictable(newpage);
445 if (PageChecked(page))
446 SetPageChecked(newpage);
447 if (PageMappedToDisk(page))
448 SetPageMappedToDisk(newpage);
450 if (PageDirty(page)) {
451 clear_page_dirty_for_io(page);
453 * Want to mark the page and the radix tree as dirty, and
454 * redo the accounting that clear_page_dirty_for_io undid,
455 * but we can't use set_page_dirty because that function
456 * is actually a signal that all of the page has become dirty.
457 * Whereas only part of our page may be dirty.
459 if (PageSwapBacked(page))
460 SetPageDirty(newpage);
461 else
462 __set_page_dirty_nobuffers(newpage);
465 mlock_migrate_page(newpage, page);
466 ksm_migrate_page(newpage, page);
468 ClearPageSwapCache(page);
469 ClearPagePrivate(page);
470 set_page_private(page, 0);
473 * If any waiters have accumulated on the new page then
474 * wake them up.
476 if (PageWriteback(newpage))
477 end_page_writeback(newpage);
480 /************************************************************
481 * Migration functions
482 ***********************************************************/
484 /* Always fail migration. Used for mappings that are not movable */
485 int fail_migrate_page(struct address_space *mapping,
486 struct page *newpage, struct page *page)
488 return -EIO;
490 EXPORT_SYMBOL(fail_migrate_page);
493 * Common logic to directly migrate a single page suitable for
494 * pages that do not use PagePrivate/PagePrivate2.
496 * Pages are locked upon entry and exit.
498 int migrate_page(struct address_space *mapping,
499 struct page *newpage, struct page *page,
500 enum migrate_mode mode)
502 int rc;
504 BUG_ON(PageWriteback(page)); /* Writeback must be complete */
506 rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode);
508 if (rc != MIGRATEPAGE_SUCCESS)
509 return rc;
511 migrate_page_copy(newpage, page);
512 return MIGRATEPAGE_SUCCESS;
514 EXPORT_SYMBOL(migrate_page);
516 #ifdef CONFIG_BLOCK
518 * Migration function for pages with buffers. This function can only be used
519 * if the underlying filesystem guarantees that no other references to "page"
520 * exist.
522 int buffer_migrate_page(struct address_space *mapping,
523 struct page *newpage, struct page *page, enum migrate_mode mode)
525 struct buffer_head *bh, *head;
526 int rc;
528 if (!page_has_buffers(page))
529 return migrate_page(mapping, newpage, page, mode);
531 head = page_buffers(page);
533 rc = migrate_page_move_mapping(mapping, newpage, page, head, mode);
535 if (rc != MIGRATEPAGE_SUCCESS)
536 return rc;
539 * In the async case, migrate_page_move_mapping locked the buffers
540 * with an IRQ-safe spinlock held. In the sync case, the buffers
541 * need to be locked now
543 if (mode != MIGRATE_ASYNC)
544 BUG_ON(!buffer_migrate_lock_buffers(head, mode));
546 ClearPagePrivate(page);
547 set_page_private(newpage, page_private(page));
548 set_page_private(page, 0);
549 put_page(page);
550 get_page(newpage);
552 bh = head;
553 do {
554 set_bh_page(bh, newpage, bh_offset(bh));
555 bh = bh->b_this_page;
557 } while (bh != head);
559 SetPagePrivate(newpage);
561 migrate_page_copy(newpage, page);
563 bh = head;
564 do {
565 unlock_buffer(bh);
566 put_bh(bh);
567 bh = bh->b_this_page;
569 } while (bh != head);
571 return MIGRATEPAGE_SUCCESS;
573 EXPORT_SYMBOL(buffer_migrate_page);
574 #endif
577 * Writeback a page to clean the dirty state
579 static int writeout(struct address_space *mapping, struct page *page)
581 struct writeback_control wbc = {
582 .sync_mode = WB_SYNC_NONE,
583 .nr_to_write = 1,
584 .range_start = 0,
585 .range_end = LLONG_MAX,
586 .for_reclaim = 1
588 int rc;
590 if (!mapping->a_ops->writepage)
591 /* No write method for the address space */
592 return -EINVAL;
594 if (!clear_page_dirty_for_io(page))
595 /* Someone else already triggered a write */
596 return -EAGAIN;
599 * A dirty page may imply that the underlying filesystem has
600 * the page on some queue. So the page must be clean for
601 * migration. Writeout may mean we loose the lock and the
602 * page state is no longer what we checked for earlier.
603 * At this point we know that the migration attempt cannot
604 * be successful.
606 remove_migration_ptes(page, page);
608 rc = mapping->a_ops->writepage(page, &wbc);
610 if (rc != AOP_WRITEPAGE_ACTIVATE)
611 /* unlocked. Relock */
612 lock_page(page);
614 return (rc < 0) ? -EIO : -EAGAIN;
618 * Default handling if a filesystem does not provide a migration function.
620 static int fallback_migrate_page(struct address_space *mapping,
621 struct page *newpage, struct page *page, enum migrate_mode mode)
623 if (PageDirty(page)) {
624 /* Only writeback pages in full synchronous migration */
625 if (mode != MIGRATE_SYNC)
626 return -EBUSY;
627 return writeout(mapping, page);
631 * Buffers may be managed in a filesystem specific way.
632 * We must have no buffers or drop them.
634 if (page_has_private(page) &&
635 !try_to_release_page(page, GFP_KERNEL))
636 return -EAGAIN;
638 return migrate_page(mapping, newpage, page, mode);
642 * Move a page to a newly allocated page
643 * The page is locked and all ptes have been successfully removed.
645 * The new page will have replaced the old page if this function
646 * is successful.
648 * Return value:
649 * < 0 - error code
650 * MIGRATEPAGE_SUCCESS - success
652 static int move_to_new_page(struct page *newpage, struct page *page,
653 int remap_swapcache, enum migrate_mode mode)
655 struct address_space *mapping;
656 int rc;
659 * Block others from accessing the page when we get around to
660 * establishing additional references. We are the only one
661 * holding a reference to the new page at this point.
663 if (!trylock_page(newpage))
664 BUG();
666 /* Prepare mapping for the new page.*/
667 newpage->index = page->index;
668 newpage->mapping = page->mapping;
669 if (PageSwapBacked(page))
670 SetPageSwapBacked(newpage);
672 mapping = page_mapping(page);
673 if (!mapping)
674 rc = migrate_page(mapping, newpage, page, mode);
675 else if (mapping->a_ops->migratepage)
677 * Most pages have a mapping and most filesystems provide a
678 * migratepage callback. Anonymous pages are part of swap
679 * space which also has its own migratepage callback. This
680 * is the most common path for page migration.
682 rc = mapping->a_ops->migratepage(mapping,
683 newpage, page, mode);
684 else
685 rc = fallback_migrate_page(mapping, newpage, page, mode);
687 if (rc != MIGRATEPAGE_SUCCESS) {
688 newpage->mapping = NULL;
689 } else {
690 if (remap_swapcache)
691 remove_migration_ptes(page, newpage);
692 page->mapping = NULL;
695 unlock_page(newpage);
697 return rc;
700 static int __unmap_and_move(struct page *page, struct page *newpage,
701 int force, bool offlining, enum migrate_mode mode)
703 int rc = -EAGAIN;
704 int remap_swapcache = 1;
705 struct mem_cgroup *mem;
706 struct anon_vma *anon_vma = NULL;
708 if (!trylock_page(page)) {
709 if (!force || mode == MIGRATE_ASYNC)
710 goto out;
713 * It's not safe for direct compaction to call lock_page.
714 * For example, during page readahead pages are added locked
715 * to the LRU. Later, when the IO completes the pages are
716 * marked uptodate and unlocked. However, the queueing
717 * could be merging multiple pages for one bio (e.g.
718 * mpage_readpages). If an allocation happens for the
719 * second or third page, the process can end up locking
720 * the same page twice and deadlocking. Rather than
721 * trying to be clever about what pages can be locked,
722 * avoid the use of lock_page for direct compaction
723 * altogether.
725 if (current->flags & PF_MEMALLOC)
726 goto out;
728 lock_page(page);
732 * Only memory hotplug's offline_pages() caller has locked out KSM,
733 * and can safely migrate a KSM page. The other cases have skipped
734 * PageKsm along with PageReserved - but it is only now when we have
735 * the page lock that we can be certain it will not go KSM beneath us
736 * (KSM will not upgrade a page from PageAnon to PageKsm when it sees
737 * its pagecount raised, but only here do we take the page lock which
738 * serializes that).
740 if (PageKsm(page) && !offlining) {
741 rc = -EBUSY;
742 goto unlock;
745 /* charge against new page */
746 mem_cgroup_prepare_migration(page, newpage, &mem);
748 if (PageWriteback(page)) {
750 * Only in the case of a full syncronous migration is it
751 * necessary to wait for PageWriteback. In the async case,
752 * the retry loop is too short and in the sync-light case,
753 * the overhead of stalling is too much
755 if (mode != MIGRATE_SYNC) {
756 rc = -EBUSY;
757 goto uncharge;
759 if (!force)
760 goto uncharge;
761 wait_on_page_writeback(page);
764 * By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
765 * we cannot notice that anon_vma is freed while we migrates a page.
766 * This get_anon_vma() delays freeing anon_vma pointer until the end
767 * of migration. File cache pages are no problem because of page_lock()
768 * File Caches may use write_page() or lock_page() in migration, then,
769 * just care Anon page here.
771 if (PageAnon(page)) {
773 * Only page_lock_anon_vma_read() understands the subtleties of
774 * getting a hold on an anon_vma from outside one of its mms.
776 anon_vma = page_get_anon_vma(page);
777 if (anon_vma) {
779 * Anon page
781 } else if (PageSwapCache(page)) {
783 * We cannot be sure that the anon_vma of an unmapped
784 * swapcache page is safe to use because we don't
785 * know in advance if the VMA that this page belonged
786 * to still exists. If the VMA and others sharing the
787 * data have been freed, then the anon_vma could
788 * already be invalid.
790 * To avoid this possibility, swapcache pages get
791 * migrated but are not remapped when migration
792 * completes
794 remap_swapcache = 0;
795 } else {
796 goto uncharge;
800 if (unlikely(balloon_page_movable(page))) {
802 * A ballooned page does not need any special attention from
803 * physical to virtual reverse mapping procedures.
804 * Skip any attempt to unmap PTEs or to remap swap cache,
805 * in order to avoid burning cycles at rmap level, and perform
806 * the page migration right away (proteced by page lock).
808 rc = balloon_page_migrate(newpage, page, mode);
809 goto uncharge;
813 * Corner case handling:
814 * 1. When a new swap-cache page is read into, it is added to the LRU
815 * and treated as swapcache but it has no rmap yet.
816 * Calling try_to_unmap() against a page->mapping==NULL page will
817 * trigger a BUG. So handle it here.
818 * 2. An orphaned page (see truncate_complete_page) might have
819 * fs-private metadata. The page can be picked up due to memory
820 * offlining. Everywhere else except page reclaim, the page is
821 * invisible to the vm, so the page can not be migrated. So try to
822 * free the metadata, so the page can be freed.
824 if (!page->mapping) {
825 VM_BUG_ON(PageAnon(page));
826 if (page_has_private(page)) {
827 try_to_free_buffers(page);
828 goto uncharge;
830 goto skip_unmap;
833 /* Establish migration ptes or remove ptes */
834 try_to_unmap(page, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
836 skip_unmap:
837 if (!page_mapped(page))
838 rc = move_to_new_page(newpage, page, remap_swapcache, mode);
840 if (rc && remap_swapcache)
841 remove_migration_ptes(page, page);
843 /* Drop an anon_vma reference if we took one */
844 if (anon_vma)
845 put_anon_vma(anon_vma);
847 uncharge:
848 mem_cgroup_end_migration(mem, page, newpage,
849 (rc == MIGRATEPAGE_SUCCESS ||
850 rc == MIGRATEPAGE_BALLOON_SUCCESS));
851 unlock:
852 unlock_page(page);
853 out:
854 return rc;
858 * Obtain the lock on page, remove all ptes and migrate the page
859 * to the newly allocated page in newpage.
861 static int unmap_and_move(new_page_t get_new_page, unsigned long private,
862 struct page *page, int force, bool offlining,
863 enum migrate_mode mode)
865 int rc = 0;
866 int *result = NULL;
867 struct page *newpage = get_new_page(page, private, &result);
869 if (!newpage)
870 return -ENOMEM;
872 if (page_count(page) == 1) {
873 /* page was freed from under us. So we are done. */
874 goto out;
877 if (unlikely(PageTransHuge(page)))
878 if (unlikely(split_huge_page(page)))
879 goto out;
881 rc = __unmap_and_move(page, newpage, force, offlining, mode);
883 if (unlikely(rc == MIGRATEPAGE_BALLOON_SUCCESS)) {
885 * A ballooned page has been migrated already.
886 * Now, it's the time to wrap-up counters,
887 * handle the page back to Buddy and return.
889 dec_zone_page_state(page, NR_ISOLATED_ANON +
890 page_is_file_cache(page));
891 balloon_page_free(page);
892 return MIGRATEPAGE_SUCCESS;
894 out:
895 if (rc != -EAGAIN) {
897 * A page that has been migrated has all references
898 * removed and will be freed. A page that has not been
899 * migrated will have kepts its references and be
900 * restored.
902 list_del(&page->lru);
903 dec_zone_page_state(page, NR_ISOLATED_ANON +
904 page_is_file_cache(page));
905 putback_lru_page(page);
908 * Move the new page to the LRU. If migration was not successful
909 * then this will free the page.
911 putback_lru_page(newpage);
912 if (result) {
913 if (rc)
914 *result = rc;
915 else
916 *result = page_to_nid(newpage);
918 return rc;
922 * Counterpart of unmap_and_move_page() for hugepage migration.
924 * This function doesn't wait the completion of hugepage I/O
925 * because there is no race between I/O and migration for hugepage.
926 * Note that currently hugepage I/O occurs only in direct I/O
927 * where no lock is held and PG_writeback is irrelevant,
928 * and writeback status of all subpages are counted in the reference
929 * count of the head page (i.e. if all subpages of a 2MB hugepage are
930 * under direct I/O, the reference of the head page is 512 and a bit more.)
931 * This means that when we try to migrate hugepage whose subpages are
932 * doing direct I/O, some references remain after try_to_unmap() and
933 * hugepage migration fails without data corruption.
935 * There is also no race when direct I/O is issued on the page under migration,
936 * because then pte is replaced with migration swap entry and direct I/O code
937 * will wait in the page fault for migration to complete.
939 static int unmap_and_move_huge_page(new_page_t get_new_page,
940 unsigned long private, struct page *hpage,
941 int force, bool offlining,
942 enum migrate_mode mode)
944 int rc = 0;
945 int *result = NULL;
946 struct page *new_hpage = get_new_page(hpage, private, &result);
947 struct anon_vma *anon_vma = NULL;
949 if (!new_hpage)
950 return -ENOMEM;
952 rc = -EAGAIN;
954 if (!trylock_page(hpage)) {
955 if (!force || mode != MIGRATE_SYNC)
956 goto out;
957 lock_page(hpage);
960 if (PageAnon(hpage))
961 anon_vma = page_get_anon_vma(hpage);
963 try_to_unmap(hpage, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
965 if (!page_mapped(hpage))
966 rc = move_to_new_page(new_hpage, hpage, 1, mode);
968 if (rc)
969 remove_migration_ptes(hpage, hpage);
971 if (anon_vma)
972 put_anon_vma(anon_vma);
974 if (!rc)
975 hugetlb_cgroup_migrate(hpage, new_hpage);
977 unlock_page(hpage);
978 out:
979 put_page(new_hpage);
980 if (result) {
981 if (rc)
982 *result = rc;
983 else
984 *result = page_to_nid(new_hpage);
986 return rc;
990 * migrate_pages
992 * The function takes one list of pages to migrate and a function
993 * that determines from the page to be migrated and the private data
994 * the target of the move and allocates the page.
996 * The function returns after 10 attempts or if no pages
997 * are movable anymore because to has become empty
998 * or no retryable pages exist anymore.
999 * Caller should call putback_lru_pages to return pages to the LRU
1000 * or free list only if ret != 0.
1002 * Return: Number of pages not migrated or error code.
1004 int migrate_pages(struct list_head *from,
1005 new_page_t get_new_page, unsigned long private, bool offlining,
1006 enum migrate_mode mode, int reason)
1008 int retry = 1;
1009 int nr_failed = 0;
1010 int nr_succeeded = 0;
1011 int pass = 0;
1012 struct page *page;
1013 struct page *page2;
1014 int swapwrite = current->flags & PF_SWAPWRITE;
1015 int rc;
1017 if (!swapwrite)
1018 current->flags |= PF_SWAPWRITE;
1020 for(pass = 0; pass < 10 && retry; pass++) {
1021 retry = 0;
1023 list_for_each_entry_safe(page, page2, from, lru) {
1024 cond_resched();
1026 rc = unmap_and_move(get_new_page, private,
1027 page, pass > 2, offlining,
1028 mode);
1030 switch(rc) {
1031 case -ENOMEM:
1032 goto out;
1033 case -EAGAIN:
1034 retry++;
1035 break;
1036 case MIGRATEPAGE_SUCCESS:
1037 nr_succeeded++;
1038 break;
1039 default:
1040 /* Permanent failure */
1041 nr_failed++;
1042 break;
1046 rc = nr_failed + retry;
1047 out:
1048 if (nr_succeeded)
1049 count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
1050 if (nr_failed)
1051 count_vm_events(PGMIGRATE_FAIL, nr_failed);
1052 trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason);
1054 if (!swapwrite)
1055 current->flags &= ~PF_SWAPWRITE;
1057 return rc;
1060 int migrate_huge_page(struct page *hpage, new_page_t get_new_page,
1061 unsigned long private, bool offlining,
1062 enum migrate_mode mode)
1064 int pass, rc;
1066 for (pass = 0; pass < 10; pass++) {
1067 rc = unmap_and_move_huge_page(get_new_page,
1068 private, hpage, pass > 2, offlining,
1069 mode);
1070 switch (rc) {
1071 case -ENOMEM:
1072 goto out;
1073 case -EAGAIN:
1074 /* try again */
1075 cond_resched();
1076 break;
1077 case MIGRATEPAGE_SUCCESS:
1078 goto out;
1079 default:
1080 rc = -EIO;
1081 goto out;
1084 out:
1085 return rc;
1088 #ifdef CONFIG_NUMA
1090 * Move a list of individual pages
1092 struct page_to_node {
1093 unsigned long addr;
1094 struct page *page;
1095 int node;
1096 int status;
1099 static struct page *new_page_node(struct page *p, unsigned long private,
1100 int **result)
1102 struct page_to_node *pm = (struct page_to_node *)private;
1104 while (pm->node != MAX_NUMNODES && pm->page != p)
1105 pm++;
1107 if (pm->node == MAX_NUMNODES)
1108 return NULL;
1110 *result = &pm->status;
1112 return alloc_pages_exact_node(pm->node,
1113 GFP_HIGHUSER_MOVABLE | GFP_THISNODE, 0);
1117 * Move a set of pages as indicated in the pm array. The addr
1118 * field must be set to the virtual address of the page to be moved
1119 * and the node number must contain a valid target node.
1120 * The pm array ends with node = MAX_NUMNODES.
1122 static int do_move_page_to_node_array(struct mm_struct *mm,
1123 struct page_to_node *pm,
1124 int migrate_all)
1126 int err;
1127 struct page_to_node *pp;
1128 LIST_HEAD(pagelist);
1130 down_read(&mm->mmap_sem);
1133 * Build a list of pages to migrate
1135 for (pp = pm; pp->node != MAX_NUMNODES; pp++) {
1136 struct vm_area_struct *vma;
1137 struct page *page;
1139 err = -EFAULT;
1140 vma = find_vma(mm, pp->addr);
1141 if (!vma || pp->addr < vma->vm_start || !vma_migratable(vma))
1142 goto set_status;
1144 page = follow_page(vma, pp->addr, FOLL_GET|FOLL_SPLIT);
1146 err = PTR_ERR(page);
1147 if (IS_ERR(page))
1148 goto set_status;
1150 err = -ENOENT;
1151 if (!page)
1152 goto set_status;
1154 /* Use PageReserved to check for zero page */
1155 if (PageReserved(page) || PageKsm(page))
1156 goto put_and_set;
1158 pp->page = page;
1159 err = page_to_nid(page);
1161 if (err == pp->node)
1163 * Node already in the right place
1165 goto put_and_set;
1167 err = -EACCES;
1168 if (page_mapcount(page) > 1 &&
1169 !migrate_all)
1170 goto put_and_set;
1172 err = isolate_lru_page(page);
1173 if (!err) {
1174 list_add_tail(&page->lru, &pagelist);
1175 inc_zone_page_state(page, NR_ISOLATED_ANON +
1176 page_is_file_cache(page));
1178 put_and_set:
1180 * Either remove the duplicate refcount from
1181 * isolate_lru_page() or drop the page ref if it was
1182 * not isolated.
1184 put_page(page);
1185 set_status:
1186 pp->status = err;
1189 err = 0;
1190 if (!list_empty(&pagelist)) {
1191 err = migrate_pages(&pagelist, new_page_node,
1192 (unsigned long)pm, 0, MIGRATE_SYNC,
1193 MR_SYSCALL);
1194 if (err)
1195 putback_lru_pages(&pagelist);
1198 up_read(&mm->mmap_sem);
1199 return err;
1203 * Migrate an array of page address onto an array of nodes and fill
1204 * the corresponding array of status.
1206 static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
1207 unsigned long nr_pages,
1208 const void __user * __user *pages,
1209 const int __user *nodes,
1210 int __user *status, int flags)
1212 struct page_to_node *pm;
1213 unsigned long chunk_nr_pages;
1214 unsigned long chunk_start;
1215 int err;
1217 err = -ENOMEM;
1218 pm = (struct page_to_node *)__get_free_page(GFP_KERNEL);
1219 if (!pm)
1220 goto out;
1222 migrate_prep();
1225 * Store a chunk of page_to_node array in a page,
1226 * but keep the last one as a marker
1228 chunk_nr_pages = (PAGE_SIZE / sizeof(struct page_to_node)) - 1;
1230 for (chunk_start = 0;
1231 chunk_start < nr_pages;
1232 chunk_start += chunk_nr_pages) {
1233 int j;
1235 if (chunk_start + chunk_nr_pages > nr_pages)
1236 chunk_nr_pages = nr_pages - chunk_start;
1238 /* fill the chunk pm with addrs and nodes from user-space */
1239 for (j = 0; j < chunk_nr_pages; j++) {
1240 const void __user *p;
1241 int node;
1243 err = -EFAULT;
1244 if (get_user(p, pages + j + chunk_start))
1245 goto out_pm;
1246 pm[j].addr = (unsigned long) p;
1248 if (get_user(node, nodes + j + chunk_start))
1249 goto out_pm;
1251 err = -ENODEV;
1252 if (node < 0 || node >= MAX_NUMNODES)
1253 goto out_pm;
1255 if (!node_state(node, N_MEMORY))
1256 goto out_pm;
1258 err = -EACCES;
1259 if (!node_isset(node, task_nodes))
1260 goto out_pm;
1262 pm[j].node = node;
1265 /* End marker for this chunk */
1266 pm[chunk_nr_pages].node = MAX_NUMNODES;
1268 /* Migrate this chunk */
1269 err = do_move_page_to_node_array(mm, pm,
1270 flags & MPOL_MF_MOVE_ALL);
1271 if (err < 0)
1272 goto out_pm;
1274 /* Return status information */
1275 for (j = 0; j < chunk_nr_pages; j++)
1276 if (put_user(pm[j].status, status + j + chunk_start)) {
1277 err = -EFAULT;
1278 goto out_pm;
1281 err = 0;
1283 out_pm:
1284 free_page((unsigned long)pm);
1285 out:
1286 return err;
1290 * Determine the nodes of an array of pages and store it in an array of status.
1292 static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
1293 const void __user **pages, int *status)
1295 unsigned long i;
1297 down_read(&mm->mmap_sem);
1299 for (i = 0; i < nr_pages; i++) {
1300 unsigned long addr = (unsigned long)(*pages);
1301 struct vm_area_struct *vma;
1302 struct page *page;
1303 int err = -EFAULT;
1305 vma = find_vma(mm, addr);
1306 if (!vma || addr < vma->vm_start)
1307 goto set_status;
1309 page = follow_page(vma, addr, 0);
1311 err = PTR_ERR(page);
1312 if (IS_ERR(page))
1313 goto set_status;
1315 err = -ENOENT;
1316 /* Use PageReserved to check for zero page */
1317 if (!page || PageReserved(page) || PageKsm(page))
1318 goto set_status;
1320 err = page_to_nid(page);
1321 set_status:
1322 *status = err;
1324 pages++;
1325 status++;
1328 up_read(&mm->mmap_sem);
1332 * Determine the nodes of a user array of pages and store it in
1333 * a user array of status.
1335 static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
1336 const void __user * __user *pages,
1337 int __user *status)
1339 #define DO_PAGES_STAT_CHUNK_NR 16
1340 const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
1341 int chunk_status[DO_PAGES_STAT_CHUNK_NR];
1343 while (nr_pages) {
1344 unsigned long chunk_nr;
1346 chunk_nr = nr_pages;
1347 if (chunk_nr > DO_PAGES_STAT_CHUNK_NR)
1348 chunk_nr = DO_PAGES_STAT_CHUNK_NR;
1350 if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages)))
1351 break;
1353 do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
1355 if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
1356 break;
1358 pages += chunk_nr;
1359 status += chunk_nr;
1360 nr_pages -= chunk_nr;
1362 return nr_pages ? -EFAULT : 0;
1366 * Move a list of pages in the address space of the currently executing
1367 * process.
1369 SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
1370 const void __user * __user *, pages,
1371 const int __user *, nodes,
1372 int __user *, status, int, flags)
1374 const struct cred *cred = current_cred(), *tcred;
1375 struct task_struct *task;
1376 struct mm_struct *mm;
1377 int err;
1378 nodemask_t task_nodes;
1380 /* Check flags */
1381 if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
1382 return -EINVAL;
1384 if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
1385 return -EPERM;
1387 /* Find the mm_struct */
1388 rcu_read_lock();
1389 task = pid ? find_task_by_vpid(pid) : current;
1390 if (!task) {
1391 rcu_read_unlock();
1392 return -ESRCH;
1394 get_task_struct(task);
1397 * Check if this process has the right to modify the specified
1398 * process. The right exists if the process has administrative
1399 * capabilities, superuser privileges or the same
1400 * userid as the target process.
1402 tcred = __task_cred(task);
1403 if (!uid_eq(cred->euid, tcred->suid) && !uid_eq(cred->euid, tcred->uid) &&
1404 !uid_eq(cred->uid, tcred->suid) && !uid_eq(cred->uid, tcred->uid) &&
1405 !capable(CAP_SYS_NICE)) {
1406 rcu_read_unlock();
1407 err = -EPERM;
1408 goto out;
1410 rcu_read_unlock();
1412 err = security_task_movememory(task);
1413 if (err)
1414 goto out;
1416 task_nodes = cpuset_mems_allowed(task);
1417 mm = get_task_mm(task);
1418 put_task_struct(task);
1420 if (!mm)
1421 return -EINVAL;
1423 if (nodes)
1424 err = do_pages_move(mm, task_nodes, nr_pages, pages,
1425 nodes, status, flags);
1426 else
1427 err = do_pages_stat(mm, nr_pages, pages, status);
1429 mmput(mm);
1430 return err;
1432 out:
1433 put_task_struct(task);
1434 return err;
1438 * Call migration functions in the vma_ops that may prepare
1439 * memory in a vm for migration. migration functions may perform
1440 * the migration for vmas that do not have an underlying page struct.
1442 int migrate_vmas(struct mm_struct *mm, const nodemask_t *to,
1443 const nodemask_t *from, unsigned long flags)
1445 struct vm_area_struct *vma;
1446 int err = 0;
1448 for (vma = mm->mmap; vma && !err; vma = vma->vm_next) {
1449 if (vma->vm_ops && vma->vm_ops->migrate) {
1450 err = vma->vm_ops->migrate(vma, to, from, flags);
1451 if (err)
1452 break;
1455 return err;
1458 #ifdef CONFIG_NUMA_BALANCING
1460 * Returns true if this is a safe migration target node for misplaced NUMA
1461 * pages. Currently it only checks the watermarks which crude
1463 static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
1464 int nr_migrate_pages)
1466 int z;
1467 for (z = pgdat->nr_zones - 1; z >= 0; z--) {
1468 struct zone *zone = pgdat->node_zones + z;
1470 if (!populated_zone(zone))
1471 continue;
1473 if (zone->all_unreclaimable)
1474 continue;
1476 /* Avoid waking kswapd by allocating pages_to_migrate pages. */
1477 if (!zone_watermark_ok(zone, 0,
1478 high_wmark_pages(zone) +
1479 nr_migrate_pages,
1480 0, 0))
1481 continue;
1482 return true;
1484 return false;
1487 static struct page *alloc_misplaced_dst_page(struct page *page,
1488 unsigned long data,
1489 int **result)
1491 int nid = (int) data;
1492 struct page *newpage;
1494 newpage = alloc_pages_exact_node(nid,
1495 (GFP_HIGHUSER_MOVABLE | GFP_THISNODE |
1496 __GFP_NOMEMALLOC | __GFP_NORETRY |
1497 __GFP_NOWARN) &
1498 ~GFP_IOFS, 0);
1499 if (newpage)
1500 page_xchg_last_nid(newpage, page_last_nid(page));
1502 return newpage;
1506 * page migration rate limiting control.
1507 * Do not migrate more than @pages_to_migrate in a @migrate_interval_millisecs
1508 * window of time. Default here says do not migrate more than 1280M per second.
1509 * If a node is rate-limited then PTE NUMA updates are also rate-limited. However
1510 * as it is faults that reset the window, pte updates will happen unconditionally
1511 * if there has not been a fault since @pteupdate_interval_millisecs after the
1512 * throttle window closed.
1514 static unsigned int migrate_interval_millisecs __read_mostly = 100;
1515 static unsigned int pteupdate_interval_millisecs __read_mostly = 1000;
1516 static unsigned int ratelimit_pages __read_mostly = 128 << (20 - PAGE_SHIFT);
1518 /* Returns true if NUMA migration is currently rate limited */
1519 bool migrate_ratelimited(int node)
1521 pg_data_t *pgdat = NODE_DATA(node);
1523 if (time_after(jiffies, pgdat->numabalancing_migrate_next_window +
1524 msecs_to_jiffies(pteupdate_interval_millisecs)))
1525 return false;
1527 if (pgdat->numabalancing_migrate_nr_pages < ratelimit_pages)
1528 return false;
1530 return true;
1533 /* Returns true if the node is migrate rate-limited after the update */
1534 bool numamigrate_update_ratelimit(pg_data_t *pgdat, unsigned long nr_pages)
1536 bool rate_limited = false;
1539 * Rate-limit the amount of data that is being migrated to a node.
1540 * Optimal placement is no good if the memory bus is saturated and
1541 * all the time is being spent migrating!
1543 spin_lock(&pgdat->numabalancing_migrate_lock);
1544 if (time_after(jiffies, pgdat->numabalancing_migrate_next_window)) {
1545 pgdat->numabalancing_migrate_nr_pages = 0;
1546 pgdat->numabalancing_migrate_next_window = jiffies +
1547 msecs_to_jiffies(migrate_interval_millisecs);
1549 if (pgdat->numabalancing_migrate_nr_pages > ratelimit_pages)
1550 rate_limited = true;
1551 else
1552 pgdat->numabalancing_migrate_nr_pages += nr_pages;
1553 spin_unlock(&pgdat->numabalancing_migrate_lock);
1555 return rate_limited;
1558 int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
1560 int ret = 0;
1562 /* Avoid migrating to a node that is nearly full */
1563 if (migrate_balanced_pgdat(pgdat, 1)) {
1564 int page_lru;
1566 if (isolate_lru_page(page)) {
1567 put_page(page);
1568 return 0;
1571 /* Page is isolated */
1572 ret = 1;
1573 page_lru = page_is_file_cache(page);
1574 if (!PageTransHuge(page))
1575 inc_zone_page_state(page, NR_ISOLATED_ANON + page_lru);
1576 else
1577 mod_zone_page_state(page_zone(page),
1578 NR_ISOLATED_ANON + page_lru,
1579 HPAGE_PMD_NR);
1583 * Page is either isolated or there is not enough space on the target
1584 * node. If isolated, then it has taken a reference count and the
1585 * callers reference can be safely dropped without the page
1586 * disappearing underneath us during migration. Otherwise the page is
1587 * not to be migrated but the callers reference should still be
1588 * dropped so it does not leak.
1590 put_page(page);
1592 return ret;
1596 * Attempt to migrate a misplaced page to the specified destination
1597 * node. Caller is expected to have an elevated reference count on
1598 * the page that will be dropped by this function before returning.
1600 int migrate_misplaced_page(struct page *page, int node)
1602 pg_data_t *pgdat = NODE_DATA(node);
1603 int isolated = 0;
1604 int nr_remaining;
1605 LIST_HEAD(migratepages);
1608 * Don't migrate pages that are mapped in multiple processes.
1609 * TODO: Handle false sharing detection instead of this hammer
1611 if (page_mapcount(page) != 1) {
1612 put_page(page);
1613 goto out;
1617 * Rate-limit the amount of data that is being migrated to a node.
1618 * Optimal placement is no good if the memory bus is saturated and
1619 * all the time is being spent migrating!
1621 if (numamigrate_update_ratelimit(pgdat, 1)) {
1622 put_page(page);
1623 goto out;
1626 isolated = numamigrate_isolate_page(pgdat, page);
1627 if (!isolated)
1628 goto out;
1630 list_add(&page->lru, &migratepages);
1631 nr_remaining = migrate_pages(&migratepages,
1632 alloc_misplaced_dst_page,
1633 node, false, MIGRATE_ASYNC,
1634 MR_NUMA_MISPLACED);
1635 if (nr_remaining) {
1636 putback_lru_pages(&migratepages);
1637 isolated = 0;
1638 } else
1639 count_vm_numa_event(NUMA_PAGE_MIGRATE);
1640 BUG_ON(!list_empty(&migratepages));
1641 out:
1642 return isolated;
1644 #endif /* CONFIG_NUMA_BALANCING */
1646 #if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
1647 int migrate_misplaced_transhuge_page(struct mm_struct *mm,
1648 struct vm_area_struct *vma,
1649 pmd_t *pmd, pmd_t entry,
1650 unsigned long address,
1651 struct page *page, int node)
1653 unsigned long haddr = address & HPAGE_PMD_MASK;
1654 pg_data_t *pgdat = NODE_DATA(node);
1655 int isolated = 0;
1656 struct page *new_page = NULL;
1657 struct mem_cgroup *memcg = NULL;
1658 int page_lru = page_is_file_cache(page);
1661 * Don't migrate pages that are mapped in multiple processes.
1662 * TODO: Handle false sharing detection instead of this hammer
1664 if (page_mapcount(page) != 1)
1665 goto out_dropref;
1668 * Rate-limit the amount of data that is being migrated to a node.
1669 * Optimal placement is no good if the memory bus is saturated and
1670 * all the time is being spent migrating!
1672 if (numamigrate_update_ratelimit(pgdat, HPAGE_PMD_NR))
1673 goto out_dropref;
1675 new_page = alloc_pages_node(node,
1676 (GFP_TRANSHUGE | GFP_THISNODE) & ~__GFP_WAIT, HPAGE_PMD_ORDER);
1677 if (!new_page) {
1678 count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
1679 goto out_dropref;
1681 page_xchg_last_nid(new_page, page_last_nid(page));
1683 isolated = numamigrate_isolate_page(pgdat, page);
1686 * Failing to isolate or a GUP pin prevents migration. The expected
1687 * page count is 2. 1 for anonymous pages without a mapping and 1
1688 * for the callers pin. If the page was isolated, the page will
1689 * need to be put back on the LRU.
1691 if (!isolated || page_count(page) != 2) {
1692 count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
1693 put_page(new_page);
1694 if (isolated) {
1695 putback_lru_page(page);
1696 isolated = 0;
1697 goto out;
1699 goto out_keep_locked;
1702 /* Prepare a page as a migration target */
1703 __set_page_locked(new_page);
1704 SetPageSwapBacked(new_page);
1706 /* anon mapping, we can simply copy page->mapping to the new page: */
1707 new_page->mapping = page->mapping;
1708 new_page->index = page->index;
1709 migrate_page_copy(new_page, page);
1710 WARN_ON(PageLRU(new_page));
1712 /* Recheck the target PMD */
1713 spin_lock(&mm->page_table_lock);
1714 if (unlikely(!pmd_same(*pmd, entry))) {
1715 spin_unlock(&mm->page_table_lock);
1717 /* Reverse changes made by migrate_page_copy() */
1718 if (TestClearPageActive(new_page))
1719 SetPageActive(page);
1720 if (TestClearPageUnevictable(new_page))
1721 SetPageUnevictable(page);
1722 mlock_migrate_page(page, new_page);
1724 unlock_page(new_page);
1725 put_page(new_page); /* Free it */
1727 unlock_page(page);
1728 putback_lru_page(page);
1730 count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
1731 goto out;
1735 * Traditional migration needs to prepare the memcg charge
1736 * transaction early to prevent the old page from being
1737 * uncharged when installing migration entries. Here we can
1738 * save the potential rollback and start the charge transfer
1739 * only when migration is already known to end successfully.
1741 mem_cgroup_prepare_migration(page, new_page, &memcg);
1743 entry = mk_pmd(new_page, vma->vm_page_prot);
1744 entry = pmd_mknonnuma(entry);
1745 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1746 entry = pmd_mkhuge(entry);
1748 page_add_new_anon_rmap(new_page, vma, haddr);
1750 set_pmd_at(mm, haddr, pmd, entry);
1751 update_mmu_cache_pmd(vma, address, &entry);
1752 page_remove_rmap(page);
1754 * Finish the charge transaction under the page table lock to
1755 * prevent split_huge_page() from dividing up the charge
1756 * before it's fully transferred to the new page.
1758 mem_cgroup_end_migration(memcg, page, new_page, true);
1759 spin_unlock(&mm->page_table_lock);
1761 unlock_page(new_page);
1762 unlock_page(page);
1763 put_page(page); /* Drop the rmap reference */
1764 put_page(page); /* Drop the LRU isolation reference */
1766 count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR);
1767 count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR);
1769 out:
1770 mod_zone_page_state(page_zone(page),
1771 NR_ISOLATED_ANON + page_lru,
1772 -HPAGE_PMD_NR);
1773 return isolated;
1775 out_dropref:
1776 put_page(page);
1777 out_keep_locked:
1778 return 0;
1780 #endif /* CONFIG_NUMA_BALANCING */
1782 #endif /* CONFIG_NUMA */