Merge tag 'fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/arm...
[linux-2.6.git] / mm / migrate.c
blob27ed22579fd97a21171b952deb78316438e69297
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 * Please do not reorder this without considering how mm/ksm.c's
469 * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
471 ClearPageSwapCache(page);
472 ClearPagePrivate(page);
473 set_page_private(page, 0);
476 * If any waiters have accumulated on the new page then
477 * wake them up.
479 if (PageWriteback(newpage))
480 end_page_writeback(newpage);
483 /************************************************************
484 * Migration functions
485 ***********************************************************/
487 /* Always fail migration. Used for mappings that are not movable */
488 int fail_migrate_page(struct address_space *mapping,
489 struct page *newpage, struct page *page)
491 return -EIO;
493 EXPORT_SYMBOL(fail_migrate_page);
496 * Common logic to directly migrate a single page suitable for
497 * pages that do not use PagePrivate/PagePrivate2.
499 * Pages are locked upon entry and exit.
501 int migrate_page(struct address_space *mapping,
502 struct page *newpage, struct page *page,
503 enum migrate_mode mode)
505 int rc;
507 BUG_ON(PageWriteback(page)); /* Writeback must be complete */
509 rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode);
511 if (rc != MIGRATEPAGE_SUCCESS)
512 return rc;
514 migrate_page_copy(newpage, page);
515 return MIGRATEPAGE_SUCCESS;
517 EXPORT_SYMBOL(migrate_page);
519 #ifdef CONFIG_BLOCK
521 * Migration function for pages with buffers. This function can only be used
522 * if the underlying filesystem guarantees that no other references to "page"
523 * exist.
525 int buffer_migrate_page(struct address_space *mapping,
526 struct page *newpage, struct page *page, enum migrate_mode mode)
528 struct buffer_head *bh, *head;
529 int rc;
531 if (!page_has_buffers(page))
532 return migrate_page(mapping, newpage, page, mode);
534 head = page_buffers(page);
536 rc = migrate_page_move_mapping(mapping, newpage, page, head, mode);
538 if (rc != MIGRATEPAGE_SUCCESS)
539 return rc;
542 * In the async case, migrate_page_move_mapping locked the buffers
543 * with an IRQ-safe spinlock held. In the sync case, the buffers
544 * need to be locked now
546 if (mode != MIGRATE_ASYNC)
547 BUG_ON(!buffer_migrate_lock_buffers(head, mode));
549 ClearPagePrivate(page);
550 set_page_private(newpage, page_private(page));
551 set_page_private(page, 0);
552 put_page(page);
553 get_page(newpage);
555 bh = head;
556 do {
557 set_bh_page(bh, newpage, bh_offset(bh));
558 bh = bh->b_this_page;
560 } while (bh != head);
562 SetPagePrivate(newpage);
564 migrate_page_copy(newpage, page);
566 bh = head;
567 do {
568 unlock_buffer(bh);
569 put_bh(bh);
570 bh = bh->b_this_page;
572 } while (bh != head);
574 return MIGRATEPAGE_SUCCESS;
576 EXPORT_SYMBOL(buffer_migrate_page);
577 #endif
580 * Writeback a page to clean the dirty state
582 static int writeout(struct address_space *mapping, struct page *page)
584 struct writeback_control wbc = {
585 .sync_mode = WB_SYNC_NONE,
586 .nr_to_write = 1,
587 .range_start = 0,
588 .range_end = LLONG_MAX,
589 .for_reclaim = 1
591 int rc;
593 if (!mapping->a_ops->writepage)
594 /* No write method for the address space */
595 return -EINVAL;
597 if (!clear_page_dirty_for_io(page))
598 /* Someone else already triggered a write */
599 return -EAGAIN;
602 * A dirty page may imply that the underlying filesystem has
603 * the page on some queue. So the page must be clean for
604 * migration. Writeout may mean we loose the lock and the
605 * page state is no longer what we checked for earlier.
606 * At this point we know that the migration attempt cannot
607 * be successful.
609 remove_migration_ptes(page, page);
611 rc = mapping->a_ops->writepage(page, &wbc);
613 if (rc != AOP_WRITEPAGE_ACTIVATE)
614 /* unlocked. Relock */
615 lock_page(page);
617 return (rc < 0) ? -EIO : -EAGAIN;
621 * Default handling if a filesystem does not provide a migration function.
623 static int fallback_migrate_page(struct address_space *mapping,
624 struct page *newpage, struct page *page, enum migrate_mode mode)
626 if (PageDirty(page)) {
627 /* Only writeback pages in full synchronous migration */
628 if (mode != MIGRATE_SYNC)
629 return -EBUSY;
630 return writeout(mapping, page);
634 * Buffers may be managed in a filesystem specific way.
635 * We must have no buffers or drop them.
637 if (page_has_private(page) &&
638 !try_to_release_page(page, GFP_KERNEL))
639 return -EAGAIN;
641 return migrate_page(mapping, newpage, page, mode);
645 * Move a page to a newly allocated page
646 * The page is locked and all ptes have been successfully removed.
648 * The new page will have replaced the old page if this function
649 * is successful.
651 * Return value:
652 * < 0 - error code
653 * MIGRATEPAGE_SUCCESS - success
655 static int move_to_new_page(struct page *newpage, struct page *page,
656 int remap_swapcache, enum migrate_mode mode)
658 struct address_space *mapping;
659 int rc;
662 * Block others from accessing the page when we get around to
663 * establishing additional references. We are the only one
664 * holding a reference to the new page at this point.
666 if (!trylock_page(newpage))
667 BUG();
669 /* Prepare mapping for the new page.*/
670 newpage->index = page->index;
671 newpage->mapping = page->mapping;
672 if (PageSwapBacked(page))
673 SetPageSwapBacked(newpage);
675 mapping = page_mapping(page);
676 if (!mapping)
677 rc = migrate_page(mapping, newpage, page, mode);
678 else if (mapping->a_ops->migratepage)
680 * Most pages have a mapping and most filesystems provide a
681 * migratepage callback. Anonymous pages are part of swap
682 * space which also has its own migratepage callback. This
683 * is the most common path for page migration.
685 rc = mapping->a_ops->migratepage(mapping,
686 newpage, page, mode);
687 else
688 rc = fallback_migrate_page(mapping, newpage, page, mode);
690 if (rc != MIGRATEPAGE_SUCCESS) {
691 newpage->mapping = NULL;
692 } else {
693 if (remap_swapcache)
694 remove_migration_ptes(page, newpage);
695 page->mapping = NULL;
698 unlock_page(newpage);
700 return rc;
703 static int __unmap_and_move(struct page *page, struct page *newpage,
704 int force, enum migrate_mode mode)
706 int rc = -EAGAIN;
707 int remap_swapcache = 1;
708 struct mem_cgroup *mem;
709 struct anon_vma *anon_vma = NULL;
711 if (!trylock_page(page)) {
712 if (!force || mode == MIGRATE_ASYNC)
713 goto out;
716 * It's not safe for direct compaction to call lock_page.
717 * For example, during page readahead pages are added locked
718 * to the LRU. Later, when the IO completes the pages are
719 * marked uptodate and unlocked. However, the queueing
720 * could be merging multiple pages for one bio (e.g.
721 * mpage_readpages). If an allocation happens for the
722 * second or third page, the process can end up locking
723 * the same page twice and deadlocking. Rather than
724 * trying to be clever about what pages can be locked,
725 * avoid the use of lock_page for direct compaction
726 * altogether.
728 if (current->flags & PF_MEMALLOC)
729 goto out;
731 lock_page(page);
734 /* charge against new page */
735 mem_cgroup_prepare_migration(page, newpage, &mem);
737 if (PageWriteback(page)) {
739 * Only in the case of a full synchronous migration is it
740 * necessary to wait for PageWriteback. In the async case,
741 * the retry loop is too short and in the sync-light case,
742 * the overhead of stalling is too much
744 if (mode != MIGRATE_SYNC) {
745 rc = -EBUSY;
746 goto uncharge;
748 if (!force)
749 goto uncharge;
750 wait_on_page_writeback(page);
753 * By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
754 * we cannot notice that anon_vma is freed while we migrates a page.
755 * This get_anon_vma() delays freeing anon_vma pointer until the end
756 * of migration. File cache pages are no problem because of page_lock()
757 * File Caches may use write_page() or lock_page() in migration, then,
758 * just care Anon page here.
760 if (PageAnon(page) && !PageKsm(page)) {
762 * Only page_lock_anon_vma_read() understands the subtleties of
763 * getting a hold on an anon_vma from outside one of its mms.
765 anon_vma = page_get_anon_vma(page);
766 if (anon_vma) {
768 * Anon page
770 } else if (PageSwapCache(page)) {
772 * We cannot be sure that the anon_vma of an unmapped
773 * swapcache page is safe to use because we don't
774 * know in advance if the VMA that this page belonged
775 * to still exists. If the VMA and others sharing the
776 * data have been freed, then the anon_vma could
777 * already be invalid.
779 * To avoid this possibility, swapcache pages get
780 * migrated but are not remapped when migration
781 * completes
783 remap_swapcache = 0;
784 } else {
785 goto uncharge;
789 if (unlikely(balloon_page_movable(page))) {
791 * A ballooned page does not need any special attention from
792 * physical to virtual reverse mapping procedures.
793 * Skip any attempt to unmap PTEs or to remap swap cache,
794 * in order to avoid burning cycles at rmap level, and perform
795 * the page migration right away (proteced by page lock).
797 rc = balloon_page_migrate(newpage, page, mode);
798 goto uncharge;
802 * Corner case handling:
803 * 1. When a new swap-cache page is read into, it is added to the LRU
804 * and treated as swapcache but it has no rmap yet.
805 * Calling try_to_unmap() against a page->mapping==NULL page will
806 * trigger a BUG. So handle it here.
807 * 2. An orphaned page (see truncate_complete_page) might have
808 * fs-private metadata. The page can be picked up due to memory
809 * offlining. Everywhere else except page reclaim, the page is
810 * invisible to the vm, so the page can not be migrated. So try to
811 * free the metadata, so the page can be freed.
813 if (!page->mapping) {
814 VM_BUG_ON(PageAnon(page));
815 if (page_has_private(page)) {
816 try_to_free_buffers(page);
817 goto uncharge;
819 goto skip_unmap;
822 /* Establish migration ptes or remove ptes */
823 try_to_unmap(page, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
825 skip_unmap:
826 if (!page_mapped(page))
827 rc = move_to_new_page(newpage, page, remap_swapcache, mode);
829 if (rc && remap_swapcache)
830 remove_migration_ptes(page, page);
832 /* Drop an anon_vma reference if we took one */
833 if (anon_vma)
834 put_anon_vma(anon_vma);
836 uncharge:
837 mem_cgroup_end_migration(mem, page, newpage,
838 (rc == MIGRATEPAGE_SUCCESS ||
839 rc == MIGRATEPAGE_BALLOON_SUCCESS));
840 unlock_page(page);
841 out:
842 return rc;
846 * Obtain the lock on page, remove all ptes and migrate the page
847 * to the newly allocated page in newpage.
849 static int unmap_and_move(new_page_t get_new_page, unsigned long private,
850 struct page *page, int force, enum migrate_mode mode)
852 int rc = 0;
853 int *result = NULL;
854 struct page *newpage = get_new_page(page, private, &result);
856 if (!newpage)
857 return -ENOMEM;
859 if (page_count(page) == 1) {
860 /* page was freed from under us. So we are done. */
861 goto out;
864 if (unlikely(PageTransHuge(page)))
865 if (unlikely(split_huge_page(page)))
866 goto out;
868 rc = __unmap_and_move(page, newpage, force, mode);
870 if (unlikely(rc == MIGRATEPAGE_BALLOON_SUCCESS)) {
872 * A ballooned page has been migrated already.
873 * Now, it's the time to wrap-up counters,
874 * handle the page back to Buddy and return.
876 dec_zone_page_state(page, NR_ISOLATED_ANON +
877 page_is_file_cache(page));
878 balloon_page_free(page);
879 return MIGRATEPAGE_SUCCESS;
881 out:
882 if (rc != -EAGAIN) {
884 * A page that has been migrated has all references
885 * removed and will be freed. A page that has not been
886 * migrated will have kepts its references and be
887 * restored.
889 list_del(&page->lru);
890 dec_zone_page_state(page, NR_ISOLATED_ANON +
891 page_is_file_cache(page));
892 putback_lru_page(page);
895 * Move the new page to the LRU. If migration was not successful
896 * then this will free the page.
898 putback_lru_page(newpage);
899 if (result) {
900 if (rc)
901 *result = rc;
902 else
903 *result = page_to_nid(newpage);
905 return rc;
909 * Counterpart of unmap_and_move_page() for hugepage migration.
911 * This function doesn't wait the completion of hugepage I/O
912 * because there is no race between I/O and migration for hugepage.
913 * Note that currently hugepage I/O occurs only in direct I/O
914 * where no lock is held and PG_writeback is irrelevant,
915 * and writeback status of all subpages are counted in the reference
916 * count of the head page (i.e. if all subpages of a 2MB hugepage are
917 * under direct I/O, the reference of the head page is 512 and a bit more.)
918 * This means that when we try to migrate hugepage whose subpages are
919 * doing direct I/O, some references remain after try_to_unmap() and
920 * hugepage migration fails without data corruption.
922 * There is also no race when direct I/O is issued on the page under migration,
923 * because then pte is replaced with migration swap entry and direct I/O code
924 * will wait in the page fault for migration to complete.
926 static int unmap_and_move_huge_page(new_page_t get_new_page,
927 unsigned long private, struct page *hpage,
928 int force, enum migrate_mode mode)
930 int rc = 0;
931 int *result = NULL;
932 struct page *new_hpage = get_new_page(hpage, private, &result);
933 struct anon_vma *anon_vma = NULL;
935 if (!new_hpage)
936 return -ENOMEM;
938 rc = -EAGAIN;
940 if (!trylock_page(hpage)) {
941 if (!force || mode != MIGRATE_SYNC)
942 goto out;
943 lock_page(hpage);
946 if (PageAnon(hpage))
947 anon_vma = page_get_anon_vma(hpage);
949 try_to_unmap(hpage, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
951 if (!page_mapped(hpage))
952 rc = move_to_new_page(new_hpage, hpage, 1, mode);
954 if (rc)
955 remove_migration_ptes(hpage, hpage);
957 if (anon_vma)
958 put_anon_vma(anon_vma);
960 if (!rc)
961 hugetlb_cgroup_migrate(hpage, new_hpage);
963 unlock_page(hpage);
964 out:
965 put_page(new_hpage);
966 if (result) {
967 if (rc)
968 *result = rc;
969 else
970 *result = page_to_nid(new_hpage);
972 return rc;
976 * migrate_pages - migrate the pages specified in a list, to the free pages
977 * supplied as the target for the page migration
979 * @from: The list of pages to be migrated.
980 * @get_new_page: The function used to allocate free pages to be used
981 * as the target of the page migration.
982 * @private: Private data to be passed on to get_new_page()
983 * @mode: The migration mode that specifies the constraints for
984 * page migration, if any.
985 * @reason: The reason for page migration.
987 * The function returns after 10 attempts or if no pages are movable any more
988 * because the list has become empty or no retryable pages exist any more.
989 * The caller should call putback_lru_pages() to return pages to the LRU
990 * or free list only if ret != 0.
992 * Returns the number of pages that were not migrated, or an error code.
994 int migrate_pages(struct list_head *from, new_page_t get_new_page,
995 unsigned long private, enum migrate_mode mode, int reason)
997 int retry = 1;
998 int nr_failed = 0;
999 int nr_succeeded = 0;
1000 int pass = 0;
1001 struct page *page;
1002 struct page *page2;
1003 int swapwrite = current->flags & PF_SWAPWRITE;
1004 int rc;
1006 if (!swapwrite)
1007 current->flags |= PF_SWAPWRITE;
1009 for(pass = 0; pass < 10 && retry; pass++) {
1010 retry = 0;
1012 list_for_each_entry_safe(page, page2, from, lru) {
1013 cond_resched();
1015 rc = unmap_and_move(get_new_page, private,
1016 page, pass > 2, mode);
1018 switch(rc) {
1019 case -ENOMEM:
1020 goto out;
1021 case -EAGAIN:
1022 retry++;
1023 break;
1024 case MIGRATEPAGE_SUCCESS:
1025 nr_succeeded++;
1026 break;
1027 default:
1028 /* Permanent failure */
1029 nr_failed++;
1030 break;
1034 rc = nr_failed + retry;
1035 out:
1036 if (nr_succeeded)
1037 count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
1038 if (nr_failed)
1039 count_vm_events(PGMIGRATE_FAIL, nr_failed);
1040 trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason);
1042 if (!swapwrite)
1043 current->flags &= ~PF_SWAPWRITE;
1045 return rc;
1048 int migrate_huge_page(struct page *hpage, new_page_t get_new_page,
1049 unsigned long private, enum migrate_mode mode)
1051 int pass, rc;
1053 for (pass = 0; pass < 10; pass++) {
1054 rc = unmap_and_move_huge_page(get_new_page, private,
1055 hpage, pass > 2, mode);
1056 switch (rc) {
1057 case -ENOMEM:
1058 goto out;
1059 case -EAGAIN:
1060 /* try again */
1061 cond_resched();
1062 break;
1063 case MIGRATEPAGE_SUCCESS:
1064 goto out;
1065 default:
1066 rc = -EIO;
1067 goto out;
1070 out:
1071 return rc;
1074 #ifdef CONFIG_NUMA
1076 * Move a list of individual pages
1078 struct page_to_node {
1079 unsigned long addr;
1080 struct page *page;
1081 int node;
1082 int status;
1085 static struct page *new_page_node(struct page *p, unsigned long private,
1086 int **result)
1088 struct page_to_node *pm = (struct page_to_node *)private;
1090 while (pm->node != MAX_NUMNODES && pm->page != p)
1091 pm++;
1093 if (pm->node == MAX_NUMNODES)
1094 return NULL;
1096 *result = &pm->status;
1098 return alloc_pages_exact_node(pm->node,
1099 GFP_HIGHUSER_MOVABLE | GFP_THISNODE, 0);
1103 * Move a set of pages as indicated in the pm array. The addr
1104 * field must be set to the virtual address of the page to be moved
1105 * and the node number must contain a valid target node.
1106 * The pm array ends with node = MAX_NUMNODES.
1108 static int do_move_page_to_node_array(struct mm_struct *mm,
1109 struct page_to_node *pm,
1110 int migrate_all)
1112 int err;
1113 struct page_to_node *pp;
1114 LIST_HEAD(pagelist);
1116 down_read(&mm->mmap_sem);
1119 * Build a list of pages to migrate
1121 for (pp = pm; pp->node != MAX_NUMNODES; pp++) {
1122 struct vm_area_struct *vma;
1123 struct page *page;
1125 err = -EFAULT;
1126 vma = find_vma(mm, pp->addr);
1127 if (!vma || pp->addr < vma->vm_start || !vma_migratable(vma))
1128 goto set_status;
1130 page = follow_page(vma, pp->addr, FOLL_GET|FOLL_SPLIT);
1132 err = PTR_ERR(page);
1133 if (IS_ERR(page))
1134 goto set_status;
1136 err = -ENOENT;
1137 if (!page)
1138 goto set_status;
1140 /* Use PageReserved to check for zero page */
1141 if (PageReserved(page))
1142 goto put_and_set;
1144 pp->page = page;
1145 err = page_to_nid(page);
1147 if (err == pp->node)
1149 * Node already in the right place
1151 goto put_and_set;
1153 err = -EACCES;
1154 if (page_mapcount(page) > 1 &&
1155 !migrate_all)
1156 goto put_and_set;
1158 err = isolate_lru_page(page);
1159 if (!err) {
1160 list_add_tail(&page->lru, &pagelist);
1161 inc_zone_page_state(page, NR_ISOLATED_ANON +
1162 page_is_file_cache(page));
1164 put_and_set:
1166 * Either remove the duplicate refcount from
1167 * isolate_lru_page() or drop the page ref if it was
1168 * not isolated.
1170 put_page(page);
1171 set_status:
1172 pp->status = err;
1175 err = 0;
1176 if (!list_empty(&pagelist)) {
1177 err = migrate_pages(&pagelist, new_page_node,
1178 (unsigned long)pm, MIGRATE_SYNC, MR_SYSCALL);
1179 if (err)
1180 putback_lru_pages(&pagelist);
1183 up_read(&mm->mmap_sem);
1184 return err;
1188 * Migrate an array of page address onto an array of nodes and fill
1189 * the corresponding array of status.
1191 static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
1192 unsigned long nr_pages,
1193 const void __user * __user *pages,
1194 const int __user *nodes,
1195 int __user *status, int flags)
1197 struct page_to_node *pm;
1198 unsigned long chunk_nr_pages;
1199 unsigned long chunk_start;
1200 int err;
1202 err = -ENOMEM;
1203 pm = (struct page_to_node *)__get_free_page(GFP_KERNEL);
1204 if (!pm)
1205 goto out;
1207 migrate_prep();
1210 * Store a chunk of page_to_node array in a page,
1211 * but keep the last one as a marker
1213 chunk_nr_pages = (PAGE_SIZE / sizeof(struct page_to_node)) - 1;
1215 for (chunk_start = 0;
1216 chunk_start < nr_pages;
1217 chunk_start += chunk_nr_pages) {
1218 int j;
1220 if (chunk_start + chunk_nr_pages > nr_pages)
1221 chunk_nr_pages = nr_pages - chunk_start;
1223 /* fill the chunk pm with addrs and nodes from user-space */
1224 for (j = 0; j < chunk_nr_pages; j++) {
1225 const void __user *p;
1226 int node;
1228 err = -EFAULT;
1229 if (get_user(p, pages + j + chunk_start))
1230 goto out_pm;
1231 pm[j].addr = (unsigned long) p;
1233 if (get_user(node, nodes + j + chunk_start))
1234 goto out_pm;
1236 err = -ENODEV;
1237 if (node < 0 || node >= MAX_NUMNODES)
1238 goto out_pm;
1240 if (!node_state(node, N_MEMORY))
1241 goto out_pm;
1243 err = -EACCES;
1244 if (!node_isset(node, task_nodes))
1245 goto out_pm;
1247 pm[j].node = node;
1250 /* End marker for this chunk */
1251 pm[chunk_nr_pages].node = MAX_NUMNODES;
1253 /* Migrate this chunk */
1254 err = do_move_page_to_node_array(mm, pm,
1255 flags & MPOL_MF_MOVE_ALL);
1256 if (err < 0)
1257 goto out_pm;
1259 /* Return status information */
1260 for (j = 0; j < chunk_nr_pages; j++)
1261 if (put_user(pm[j].status, status + j + chunk_start)) {
1262 err = -EFAULT;
1263 goto out_pm;
1266 err = 0;
1268 out_pm:
1269 free_page((unsigned long)pm);
1270 out:
1271 return err;
1275 * Determine the nodes of an array of pages and store it in an array of status.
1277 static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
1278 const void __user **pages, int *status)
1280 unsigned long i;
1282 down_read(&mm->mmap_sem);
1284 for (i = 0; i < nr_pages; i++) {
1285 unsigned long addr = (unsigned long)(*pages);
1286 struct vm_area_struct *vma;
1287 struct page *page;
1288 int err = -EFAULT;
1290 vma = find_vma(mm, addr);
1291 if (!vma || addr < vma->vm_start)
1292 goto set_status;
1294 page = follow_page(vma, addr, 0);
1296 err = PTR_ERR(page);
1297 if (IS_ERR(page))
1298 goto set_status;
1300 err = -ENOENT;
1301 /* Use PageReserved to check for zero page */
1302 if (!page || PageReserved(page))
1303 goto set_status;
1305 err = page_to_nid(page);
1306 set_status:
1307 *status = err;
1309 pages++;
1310 status++;
1313 up_read(&mm->mmap_sem);
1317 * Determine the nodes of a user array of pages and store it in
1318 * a user array of status.
1320 static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
1321 const void __user * __user *pages,
1322 int __user *status)
1324 #define DO_PAGES_STAT_CHUNK_NR 16
1325 const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
1326 int chunk_status[DO_PAGES_STAT_CHUNK_NR];
1328 while (nr_pages) {
1329 unsigned long chunk_nr;
1331 chunk_nr = nr_pages;
1332 if (chunk_nr > DO_PAGES_STAT_CHUNK_NR)
1333 chunk_nr = DO_PAGES_STAT_CHUNK_NR;
1335 if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages)))
1336 break;
1338 do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
1340 if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
1341 break;
1343 pages += chunk_nr;
1344 status += chunk_nr;
1345 nr_pages -= chunk_nr;
1347 return nr_pages ? -EFAULT : 0;
1351 * Move a list of pages in the address space of the currently executing
1352 * process.
1354 SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
1355 const void __user * __user *, pages,
1356 const int __user *, nodes,
1357 int __user *, status, int, flags)
1359 const struct cred *cred = current_cred(), *tcred;
1360 struct task_struct *task;
1361 struct mm_struct *mm;
1362 int err;
1363 nodemask_t task_nodes;
1365 /* Check flags */
1366 if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
1367 return -EINVAL;
1369 if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
1370 return -EPERM;
1372 /* Find the mm_struct */
1373 rcu_read_lock();
1374 task = pid ? find_task_by_vpid(pid) : current;
1375 if (!task) {
1376 rcu_read_unlock();
1377 return -ESRCH;
1379 get_task_struct(task);
1382 * Check if this process has the right to modify the specified
1383 * process. The right exists if the process has administrative
1384 * capabilities, superuser privileges or the same
1385 * userid as the target process.
1387 tcred = __task_cred(task);
1388 if (!uid_eq(cred->euid, tcred->suid) && !uid_eq(cred->euid, tcred->uid) &&
1389 !uid_eq(cred->uid, tcred->suid) && !uid_eq(cred->uid, tcred->uid) &&
1390 !capable(CAP_SYS_NICE)) {
1391 rcu_read_unlock();
1392 err = -EPERM;
1393 goto out;
1395 rcu_read_unlock();
1397 err = security_task_movememory(task);
1398 if (err)
1399 goto out;
1401 task_nodes = cpuset_mems_allowed(task);
1402 mm = get_task_mm(task);
1403 put_task_struct(task);
1405 if (!mm)
1406 return -EINVAL;
1408 if (nodes)
1409 err = do_pages_move(mm, task_nodes, nr_pages, pages,
1410 nodes, status, flags);
1411 else
1412 err = do_pages_stat(mm, nr_pages, pages, status);
1414 mmput(mm);
1415 return err;
1417 out:
1418 put_task_struct(task);
1419 return err;
1423 * Call migration functions in the vma_ops that may prepare
1424 * memory in a vm for migration. migration functions may perform
1425 * the migration for vmas that do not have an underlying page struct.
1427 int migrate_vmas(struct mm_struct *mm, const nodemask_t *to,
1428 const nodemask_t *from, unsigned long flags)
1430 struct vm_area_struct *vma;
1431 int err = 0;
1433 for (vma = mm->mmap; vma && !err; vma = vma->vm_next) {
1434 if (vma->vm_ops && vma->vm_ops->migrate) {
1435 err = vma->vm_ops->migrate(vma, to, from, flags);
1436 if (err)
1437 break;
1440 return err;
1443 #ifdef CONFIG_NUMA_BALANCING
1445 * Returns true if this is a safe migration target node for misplaced NUMA
1446 * pages. Currently it only checks the watermarks which crude
1448 static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
1449 unsigned long nr_migrate_pages)
1451 int z;
1452 for (z = pgdat->nr_zones - 1; z >= 0; z--) {
1453 struct zone *zone = pgdat->node_zones + z;
1455 if (!populated_zone(zone))
1456 continue;
1458 if (zone->all_unreclaimable)
1459 continue;
1461 /* Avoid waking kswapd by allocating pages_to_migrate pages. */
1462 if (!zone_watermark_ok(zone, 0,
1463 high_wmark_pages(zone) +
1464 nr_migrate_pages,
1465 0, 0))
1466 continue;
1467 return true;
1469 return false;
1472 static struct page *alloc_misplaced_dst_page(struct page *page,
1473 unsigned long data,
1474 int **result)
1476 int nid = (int) data;
1477 struct page *newpage;
1479 newpage = alloc_pages_exact_node(nid,
1480 (GFP_HIGHUSER_MOVABLE | GFP_THISNODE |
1481 __GFP_NOMEMALLOC | __GFP_NORETRY |
1482 __GFP_NOWARN) &
1483 ~GFP_IOFS, 0);
1484 if (newpage)
1485 page_nid_xchg_last(newpage, page_nid_last(page));
1487 return newpage;
1491 * page migration rate limiting control.
1492 * Do not migrate more than @pages_to_migrate in a @migrate_interval_millisecs
1493 * window of time. Default here says do not migrate more than 1280M per second.
1494 * If a node is rate-limited then PTE NUMA updates are also rate-limited. However
1495 * as it is faults that reset the window, pte updates will happen unconditionally
1496 * if there has not been a fault since @pteupdate_interval_millisecs after the
1497 * throttle window closed.
1499 static unsigned int migrate_interval_millisecs __read_mostly = 100;
1500 static unsigned int pteupdate_interval_millisecs __read_mostly = 1000;
1501 static unsigned int ratelimit_pages __read_mostly = 128 << (20 - PAGE_SHIFT);
1503 /* Returns true if NUMA migration is currently rate limited */
1504 bool migrate_ratelimited(int node)
1506 pg_data_t *pgdat = NODE_DATA(node);
1508 if (time_after(jiffies, pgdat->numabalancing_migrate_next_window +
1509 msecs_to_jiffies(pteupdate_interval_millisecs)))
1510 return false;
1512 if (pgdat->numabalancing_migrate_nr_pages < ratelimit_pages)
1513 return false;
1515 return true;
1518 /* Returns true if the node is migrate rate-limited after the update */
1519 bool numamigrate_update_ratelimit(pg_data_t *pgdat, unsigned long nr_pages)
1521 bool rate_limited = false;
1524 * Rate-limit the amount of data that is being migrated to a node.
1525 * Optimal placement is no good if the memory bus is saturated and
1526 * all the time is being spent migrating!
1528 spin_lock(&pgdat->numabalancing_migrate_lock);
1529 if (time_after(jiffies, pgdat->numabalancing_migrate_next_window)) {
1530 pgdat->numabalancing_migrate_nr_pages = 0;
1531 pgdat->numabalancing_migrate_next_window = jiffies +
1532 msecs_to_jiffies(migrate_interval_millisecs);
1534 if (pgdat->numabalancing_migrate_nr_pages > ratelimit_pages)
1535 rate_limited = true;
1536 else
1537 pgdat->numabalancing_migrate_nr_pages += nr_pages;
1538 spin_unlock(&pgdat->numabalancing_migrate_lock);
1540 return rate_limited;
1543 int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
1545 int page_lru;
1547 VM_BUG_ON(compound_order(page) && !PageTransHuge(page));
1549 /* Avoid migrating to a node that is nearly full */
1550 if (!migrate_balanced_pgdat(pgdat, 1UL << compound_order(page)))
1551 return 0;
1553 if (isolate_lru_page(page))
1554 return 0;
1557 * migrate_misplaced_transhuge_page() skips page migration's usual
1558 * check on page_count(), so we must do it here, now that the page
1559 * has been isolated: a GUP pin, or any other pin, prevents migration.
1560 * The expected page count is 3: 1 for page's mapcount and 1 for the
1561 * caller's pin and 1 for the reference taken by isolate_lru_page().
1563 if (PageTransHuge(page) && page_count(page) != 3) {
1564 putback_lru_page(page);
1565 return 0;
1568 page_lru = page_is_file_cache(page);
1569 mod_zone_page_state(page_zone(page), NR_ISOLATED_ANON + page_lru,
1570 hpage_nr_pages(page));
1573 * Isolating the page has taken another reference, so the
1574 * caller's reference can be safely dropped without the page
1575 * disappearing underneath us during migration.
1577 put_page(page);
1578 return 1;
1582 * Attempt to migrate a misplaced page to the specified destination
1583 * node. Caller is expected to have an elevated reference count on
1584 * the page that will be dropped by this function before returning.
1586 int migrate_misplaced_page(struct page *page, int node)
1588 pg_data_t *pgdat = NODE_DATA(node);
1589 int isolated;
1590 int nr_remaining;
1591 LIST_HEAD(migratepages);
1594 * Don't migrate pages that are mapped in multiple processes.
1595 * TODO: Handle false sharing detection instead of this hammer
1597 if (page_mapcount(page) != 1)
1598 goto out;
1601 * Rate-limit the amount of data that is being migrated to a node.
1602 * Optimal placement is no good if the memory bus is saturated and
1603 * all the time is being spent migrating!
1605 if (numamigrate_update_ratelimit(pgdat, 1))
1606 goto out;
1608 isolated = numamigrate_isolate_page(pgdat, page);
1609 if (!isolated)
1610 goto out;
1612 list_add(&page->lru, &migratepages);
1613 nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page,
1614 node, MIGRATE_ASYNC, MR_NUMA_MISPLACED);
1615 if (nr_remaining) {
1616 putback_lru_pages(&migratepages);
1617 isolated = 0;
1618 } else
1619 count_vm_numa_event(NUMA_PAGE_MIGRATE);
1620 BUG_ON(!list_empty(&migratepages));
1621 return isolated;
1623 out:
1624 put_page(page);
1625 return 0;
1627 #endif /* CONFIG_NUMA_BALANCING */
1629 #if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
1631 * Migrates a THP to a given target node. page must be locked and is unlocked
1632 * before returning.
1634 int migrate_misplaced_transhuge_page(struct mm_struct *mm,
1635 struct vm_area_struct *vma,
1636 pmd_t *pmd, pmd_t entry,
1637 unsigned long address,
1638 struct page *page, int node)
1640 unsigned long haddr = address & HPAGE_PMD_MASK;
1641 pg_data_t *pgdat = NODE_DATA(node);
1642 int isolated = 0;
1643 struct page *new_page = NULL;
1644 struct mem_cgroup *memcg = NULL;
1645 int page_lru = page_is_file_cache(page);
1648 * Don't migrate pages that are mapped in multiple processes.
1649 * TODO: Handle false sharing detection instead of this hammer
1651 if (page_mapcount(page) != 1)
1652 goto out_dropref;
1655 * Rate-limit the amount of data that is being migrated to a node.
1656 * Optimal placement is no good if the memory bus is saturated and
1657 * all the time is being spent migrating!
1659 if (numamigrate_update_ratelimit(pgdat, HPAGE_PMD_NR))
1660 goto out_dropref;
1662 new_page = alloc_pages_node(node,
1663 (GFP_TRANSHUGE | GFP_THISNODE) & ~__GFP_WAIT, HPAGE_PMD_ORDER);
1664 if (!new_page)
1665 goto out_fail;
1667 page_nid_xchg_last(new_page, page_nid_last(page));
1669 isolated = numamigrate_isolate_page(pgdat, page);
1670 if (!isolated) {
1671 put_page(new_page);
1672 goto out_fail;
1675 /* Prepare a page as a migration target */
1676 __set_page_locked(new_page);
1677 SetPageSwapBacked(new_page);
1679 /* anon mapping, we can simply copy page->mapping to the new page: */
1680 new_page->mapping = page->mapping;
1681 new_page->index = page->index;
1682 migrate_page_copy(new_page, page);
1683 WARN_ON(PageLRU(new_page));
1685 /* Recheck the target PMD */
1686 spin_lock(&mm->page_table_lock);
1687 if (unlikely(!pmd_same(*pmd, entry))) {
1688 spin_unlock(&mm->page_table_lock);
1690 /* Reverse changes made by migrate_page_copy() */
1691 if (TestClearPageActive(new_page))
1692 SetPageActive(page);
1693 if (TestClearPageUnevictable(new_page))
1694 SetPageUnevictable(page);
1695 mlock_migrate_page(page, new_page);
1697 unlock_page(new_page);
1698 put_page(new_page); /* Free it */
1700 unlock_page(page);
1701 putback_lru_page(page);
1703 count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
1704 isolated = 0;
1705 goto out;
1709 * Traditional migration needs to prepare the memcg charge
1710 * transaction early to prevent the old page from being
1711 * uncharged when installing migration entries. Here we can
1712 * save the potential rollback and start the charge transfer
1713 * only when migration is already known to end successfully.
1715 mem_cgroup_prepare_migration(page, new_page, &memcg);
1717 entry = mk_pmd(new_page, vma->vm_page_prot);
1718 entry = pmd_mknonnuma(entry);
1719 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1720 entry = pmd_mkhuge(entry);
1722 page_add_new_anon_rmap(new_page, vma, haddr);
1724 set_pmd_at(mm, haddr, pmd, entry);
1725 update_mmu_cache_pmd(vma, address, &entry);
1726 page_remove_rmap(page);
1728 * Finish the charge transaction under the page table lock to
1729 * prevent split_huge_page() from dividing up the charge
1730 * before it's fully transferred to the new page.
1732 mem_cgroup_end_migration(memcg, page, new_page, true);
1733 spin_unlock(&mm->page_table_lock);
1735 unlock_page(new_page);
1736 unlock_page(page);
1737 put_page(page); /* Drop the rmap reference */
1738 put_page(page); /* Drop the LRU isolation reference */
1740 count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR);
1741 count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR);
1743 out:
1744 mod_zone_page_state(page_zone(page),
1745 NR_ISOLATED_ANON + page_lru,
1746 -HPAGE_PMD_NR);
1747 return isolated;
1749 out_fail:
1750 count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
1751 out_dropref:
1752 unlock_page(page);
1753 put_page(page);
1754 return 0;
1756 #endif /* CONFIG_NUMA_BALANCING */
1758 #endif /* CONFIG_NUMA */