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1 /*
2 * Memory Migration functionality - linux/mm/migration.c
3 *
4 * Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter
5 *
6 * Page migration was first developed in the context of the memory hotplug
7 * project. The main authors of the migration code are:
8 *
9 * IWAMOTO Toshihiro <iwamoto@valinux.co.jp>
10 * Hirokazu Takahashi <taka@valinux.co.jp>
11 * Dave Hansen <haveblue@us.ibm.com>
12 * Christoph Lameter
13 */
14
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>
39 #include <linux/mmu_notifier.h>
40
41 #include <asm/tlbflush.h>
42
43 #define CREATE_TRACE_POINTS
44 #include <trace/events/migrate.h>
45
46 #include "internal.h"
47
48 /*
49 * migrate_prep() needs to be called before we start compiling a list of pages
50 * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
51 * undesirable, use migrate_prep_local()
52 */
53 int migrate_prep(void)
54 {
55 /*
56 * Clear the LRU lists so pages can be isolated.
57 * Note that pages may be moved off the LRU after we have
58 * drained them. Those pages will fail to migrate like other
59 * pages that may be busy.
60 */
61 lru_add_drain_all();
62
63 return 0;
64 }
65
66 /* Do the necessary work of migrate_prep but not if it involves other CPUs */
67 int migrate_prep_local(void)
68 {
69 lru_add_drain();
70
71 return 0;
72 }
73
74 /*
75 * Put previously isolated pages back onto the appropriate lists
76 * from where they were once taken off for compaction/migration.
77 *
78 * This function shall be used whenever the isolated pageset has been
79 * built from lru, balloon, hugetlbfs page. See isolate_migratepages_range()
80 * and isolate_huge_page().
81 */
82 void putback_movable_pages(struct list_head *l)
83 {
84 struct page *page;
85 struct page *page2;
86
87 list_for_each_entry_safe(page, page2, l, lru) {
88 if (unlikely(PageHuge(page))) {
89 putback_active_hugepage(page);
90 continue;
91 }
92 list_del(&page->lru);
93 dec_zone_page_state(page, NR_ISOLATED_ANON +
94 page_is_file_cache(page));
95 if (unlikely(isolated_balloon_page(page)))
96 balloon_page_putback(page);
97 else
98 putback_lru_page(page);
99 }
100 }
101
102 /*
103 * Restore a potential migration pte to a working pte entry
104 */
105 static int remove_migration_pte(struct page *new, struct vm_area_struct *vma,
106 unsigned long addr, void *old)
107 {
108 struct mm_struct *mm = vma->vm_mm;
109 swp_entry_t entry;
110 pmd_t *pmd;
111 pte_t *ptep, pte;
112 spinlock_t *ptl;
113
114 if (unlikely(PageHuge(new))) {
115 ptep = huge_pte_offset(mm, addr);
116 if (!ptep)
117 goto out;
118 ptl = huge_pte_lockptr(hstate_vma(vma), mm, ptep);
119 } else {
120 pmd = mm_find_pmd(mm, addr);
121 if (!pmd)
122 goto out;
123
124 ptep = pte_offset_map(pmd, addr);
125
126 /*
127 * Peek to check is_swap_pte() before taking ptlock? No, we
128 * can race mremap's move_ptes(), which skips anon_vma lock.
129 */
130
131 ptl = pte_lockptr(mm, pmd);
132 }
133
134 spin_lock(ptl);
135 pte = *ptep;
136 if (!is_swap_pte(pte))
137 goto unlock;
138
139 entry = pte_to_swp_entry(pte);
140
141 if (!is_migration_entry(entry) ||
142 migration_entry_to_page(entry) != old)
143 goto unlock;
144
145 get_page(new);
146 pte = pte_mkold(mk_pte(new, vma->vm_page_prot));
147 if (pte_swp_soft_dirty(*ptep))
148 pte = pte_mksoft_dirty(pte);
149
150 /* Recheck VMA as permissions can change since migration started */
151 if (is_write_migration_entry(entry))
152 pte = maybe_mkwrite(pte, vma);
153
154 #ifdef CONFIG_HUGETLB_PAGE
155 if (PageHuge(new)) {
156 pte = pte_mkhuge(pte);
157 pte = arch_make_huge_pte(pte, vma, new, 0);
158 }
159 #endif
160 flush_dcache_page(new);
161 set_pte_at(mm, addr, ptep, pte);
162
163 if (PageHuge(new)) {
164 if (PageAnon(new))
165 hugepage_add_anon_rmap(new, vma, addr);
166 else
167 page_dup_rmap(new);
168 } else if (PageAnon(new))
169 page_add_anon_rmap(new, vma, addr);
170 else
171 page_add_file_rmap(new);
172
173 /* No need to invalidate - it was non-present before */
174 update_mmu_cache(vma, addr, ptep);
175 unlock:
176 pte_unmap_unlock(ptep, ptl);
177 out:
178 return SWAP_AGAIN;
179 }
180
181 /*
182 * Get rid of all migration entries and replace them by
183 * references to the indicated page.
184 */
185 static void remove_migration_ptes(struct page *old, struct page *new)
186 {
187 struct rmap_walk_control rwc = {
188 .rmap_one = remove_migration_pte,
189 .arg = old,
190 };
191
192 rmap_walk(new, &rwc);
193 }
194
195 /*
196 * Something used the pte of a page under migration. We need to
197 * get to the page and wait until migration is finished.
198 * When we return from this function the fault will be retried.
199 */
200 void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
201 spinlock_t *ptl)
202 {
203 pte_t pte;
204 swp_entry_t entry;
205 struct page *page;
206
207 spin_lock(ptl);
208 pte = *ptep;
209 if (!is_swap_pte(pte))
210 goto out;
211
212 entry = pte_to_swp_entry(pte);
213 if (!is_migration_entry(entry))
214 goto out;
215
216 page = migration_entry_to_page(entry);
217
218 /*
219 * Once radix-tree replacement of page migration started, page_count
220 * *must* be zero. And, we don't want to call wait_on_page_locked()
221 * against a page without get_page().
222 * So, we use get_page_unless_zero(), here. Even failed, page fault
223 * will occur again.
224 */
225 if (!get_page_unless_zero(page))
226 goto out;
227 pte_unmap_unlock(ptep, ptl);
228 wait_on_page_locked(page);
229 put_page(page);
230 return;
231 out:
232 pte_unmap_unlock(ptep, ptl);
233 }
234
235 void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
236 unsigned long address)
237 {
238 spinlock_t *ptl = pte_lockptr(mm, pmd);
239 pte_t *ptep = pte_offset_map(pmd, address);
240 __migration_entry_wait(mm, ptep, ptl);
241 }
242
243 void migration_entry_wait_huge(struct vm_area_struct *vma,
244 struct mm_struct *mm, pte_t *pte)
245 {
246 spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), mm, pte);
247 __migration_entry_wait(mm, pte, ptl);
248 }
249
250 #ifdef CONFIG_BLOCK
251 /* Returns true if all buffers are successfully locked */
252 static bool buffer_migrate_lock_buffers(struct buffer_head *head,
253 enum migrate_mode mode)
254 {
255 struct buffer_head *bh = head;
256
257 /* Simple case, sync compaction */
258 if (mode != MIGRATE_ASYNC) {
259 do {
260 get_bh(bh);
261 lock_buffer(bh);
262 bh = bh->b_this_page;
263
264 } while (bh != head);
265
266 return true;
267 }
268
269 /* async case, we cannot block on lock_buffer so use trylock_buffer */
270 do {
271 get_bh(bh);
272 if (!trylock_buffer(bh)) {
273 /*
274 * We failed to lock the buffer and cannot stall in
275 * async migration. Release the taken locks
276 */
277 struct buffer_head *failed_bh = bh;
278 put_bh(failed_bh);
279 bh = head;
280 while (bh != failed_bh) {
281 unlock_buffer(bh);
282 put_bh(bh);
283 bh = bh->b_this_page;
284 }
285 return false;
286 }
287
288 bh = bh->b_this_page;
289 } while (bh != head);
290 return true;
291 }
292 #else
293 static inline bool buffer_migrate_lock_buffers(struct buffer_head *head,
294 enum migrate_mode mode)
295 {
296 return true;
297 }
298 #endif /* CONFIG_BLOCK */
299
300 /*
301 * Replace the page in the mapping.
302 *
303 * The number of remaining references must be:
304 * 1 for anonymous pages without a mapping
305 * 2 for pages with a mapping
306 * 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
307 */
308 int migrate_page_move_mapping(struct address_space *mapping,
309 struct page *newpage, struct page *page,
310 struct buffer_head *head, enum migrate_mode mode,
311 int extra_count)
312 {
313 int expected_count = 1 + extra_count;
314 void **pslot;
315
316 if (!mapping) {
317 /* Anonymous page without mapping */
318 if (page_count(page) != expected_count)
319 return -EAGAIN;
320 return MIGRATEPAGE_SUCCESS;
321 }
322
323 spin_lock_irq(&mapping->tree_lock);
324
325 pslot = radix_tree_lookup_slot(&mapping->page_tree,
326 page_index(page));
327
328 expected_count += 1 + page_has_private(page);
329 if (page_count(page) != expected_count ||
330 radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {
331 spin_unlock_irq(&mapping->tree_lock);
332 return -EAGAIN;
333 }
334
335 if (!page_freeze_refs(page, expected_count)) {
336 spin_unlock_irq(&mapping->tree_lock);
337 return -EAGAIN;
338 }
339
340 /*
341 * In the async migration case of moving a page with buffers, lock the
342 * buffers using trylock before the mapping is moved. If the mapping
343 * was moved, we later failed to lock the buffers and could not move
344 * the mapping back due to an elevated page count, we would have to
345 * block waiting on other references to be dropped.
346 */
347 if (mode == MIGRATE_ASYNC && head &&
348 !buffer_migrate_lock_buffers(head, mode)) {
349 page_unfreeze_refs(page, expected_count);
350 spin_unlock_irq(&mapping->tree_lock);
351 return -EAGAIN;
352 }
353
354 /*
355 * Now we know that no one else is looking at the page.
356 */
357 get_page(newpage); /* add cache reference */
358 if (PageSwapCache(page)) {
359 SetPageSwapCache(newpage);
360 set_page_private(newpage, page_private(page));
361 }
362
363 radix_tree_replace_slot(pslot, newpage);
364
365 /*
366 * Drop cache reference from old page by unfreezing
367 * to one less reference.
368 * We know this isn't the last reference.
369 */
370 page_unfreeze_refs(page, expected_count - 1);
371
372 /*
373 * If moved to a different zone then also account
374 * the page for that zone. Other VM counters will be
375 * taken care of when we establish references to the
376 * new page and drop references to the old page.
377 *
378 * Note that anonymous pages are accounted for
379 * via NR_FILE_PAGES and NR_ANON_PAGES if they
380 * are mapped to swap space.
381 */
382 __dec_zone_page_state(page, NR_FILE_PAGES);
383 __inc_zone_page_state(newpage, NR_FILE_PAGES);
384 if (!PageSwapCache(page) && PageSwapBacked(page)) {
385 __dec_zone_page_state(page, NR_SHMEM);
386 __inc_zone_page_state(newpage, NR_SHMEM);
387 }
388 spin_unlock_irq(&mapping->tree_lock);
389
390 return MIGRATEPAGE_SUCCESS;
391 }
392
393 /*
394 * The expected number of remaining references is the same as that
395 * of migrate_page_move_mapping().
396 */
397 int migrate_huge_page_move_mapping(struct address_space *mapping,
398 struct page *newpage, struct page *page)
399 {
400 int expected_count;
401 void **pslot;
402
403 if (!mapping) {
404 if (page_count(page) != 1)
405 return -EAGAIN;
406 return MIGRATEPAGE_SUCCESS;
407 }
408
409 spin_lock_irq(&mapping->tree_lock);
410
411 pslot = radix_tree_lookup_slot(&mapping->page_tree,
412 page_index(page));
413
414 expected_count = 2 + page_has_private(page);
415 if (page_count(page) != expected_count ||
416 radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {
417 spin_unlock_irq(&mapping->tree_lock);
418 return -EAGAIN;
419 }
420
421 if (!page_freeze_refs(page, expected_count)) {
422 spin_unlock_irq(&mapping->tree_lock);
423 return -EAGAIN;
424 }
425
426 get_page(newpage);
427
428 radix_tree_replace_slot(pslot, newpage);
429
430 page_unfreeze_refs(page, expected_count - 1);
431
432 spin_unlock_irq(&mapping->tree_lock);
433 return MIGRATEPAGE_SUCCESS;
434 }
435
436 /*
437 * Gigantic pages are so large that we do not guarantee that page++ pointer
438 * arithmetic will work across the entire page. We need something more
439 * specialized.
440 */
441 static void __copy_gigantic_page(struct page *dst, struct page *src,
442 int nr_pages)
443 {
444 int i;
445 struct page *dst_base = dst;
446 struct page *src_base = src;
447
448 for (i = 0; i < nr_pages; ) {
449 cond_resched();
450 copy_highpage(dst, src);
451
452 i++;
453 dst = mem_map_next(dst, dst_base, i);
454 src = mem_map_next(src, src_base, i);
455 }
456 }
457
458 static void copy_huge_page(struct page *dst, struct page *src)
459 {
460 int i;
461 int nr_pages;
462
463 if (PageHuge(src)) {
464 /* hugetlbfs page */
465 struct hstate *h = page_hstate(src);
466 nr_pages = pages_per_huge_page(h);
467
468 if (unlikely(nr_pages > MAX_ORDER_NR_PAGES)) {
469 __copy_gigantic_page(dst, src, nr_pages);
470 return;
471 }
472 } else {
473 /* thp page */
474 BUG_ON(!PageTransHuge(src));
475 nr_pages = hpage_nr_pages(src);
476 }
477
478 for (i = 0; i < nr_pages; i++) {
479 cond_resched();
480 copy_highpage(dst + i, src + i);
481 }
482 }
483
484 /*
485 * Copy the page to its new location
486 */
487 void migrate_page_copy(struct page *newpage, struct page *page)
488 {
489 int cpupid;
490
491 if (PageHuge(page) || PageTransHuge(page))
492 copy_huge_page(newpage, page);
493 else
494 copy_highpage(newpage, page);
495
496 if (PageError(page))
497 SetPageError(newpage);
498 if (PageReferenced(page))
499 SetPageReferenced(newpage);
500 if (PageUptodate(page))
501 SetPageUptodate(newpage);
502 if (TestClearPageActive(page)) {
503 VM_BUG_ON_PAGE(PageUnevictable(page), page);
504 SetPageActive(newpage);
505 } else if (TestClearPageUnevictable(page))
506 SetPageUnevictable(newpage);
507 if (PageChecked(page))
508 SetPageChecked(newpage);
509 if (PageMappedToDisk(page))
510 SetPageMappedToDisk(newpage);
511
512 if (PageDirty(page)) {
513 clear_page_dirty_for_io(page);
514 /*
515 * Want to mark the page and the radix tree as dirty, and
516 * redo the accounting that clear_page_dirty_for_io undid,
517 * but we can't use set_page_dirty because that function
518 * is actually a signal that all of the page has become dirty.
519 * Whereas only part of our page may be dirty.
520 */
521 if (PageSwapBacked(page))
522 SetPageDirty(newpage);
523 else
524 __set_page_dirty_nobuffers(newpage);
525 }
526
527 /*
528 * Copy NUMA information to the new page, to prevent over-eager
529 * future migrations of this same page.
530 */
531 cpupid = page_cpupid_xchg_last(page, -1);
532 page_cpupid_xchg_last(newpage, cpupid);
533
534 mlock_migrate_page(newpage, page);
535 ksm_migrate_page(newpage, page);
536 /*
537 * Please do not reorder this without considering how mm/ksm.c's
538 * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
539 */
540 if (PageSwapCache(page))
541 ClearPageSwapCache(page);
542 ClearPagePrivate(page);
543 set_page_private(page, 0);
544
545 /*
546 * If any waiters have accumulated on the new page then
547 * wake them up.
548 */
549 if (PageWriteback(newpage))
550 end_page_writeback(newpage);
551 }
552
553 /************************************************************
554 * Migration functions
555 ***********************************************************/
556
557 /*
558 * Common logic to directly migrate a single page suitable for
559 * pages that do not use PagePrivate/PagePrivate2.
560 *
561 * Pages are locked upon entry and exit.
562 */
563 int migrate_page(struct address_space *mapping,
564 struct page *newpage, struct page *page,
565 enum migrate_mode mode)
566 {
567 int rc;
568
569 BUG_ON(PageWriteback(page)); /* Writeback must be complete */
570
571 rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode, 0);
572
573 if (rc != MIGRATEPAGE_SUCCESS)
574 return rc;
575
576 migrate_page_copy(newpage, page);
577 return MIGRATEPAGE_SUCCESS;
578 }
579 EXPORT_SYMBOL(migrate_page);
580
581 #ifdef CONFIG_BLOCK
582 /*
583 * Migration function for pages with buffers. This function can only be used
584 * if the underlying filesystem guarantees that no other references to "page"
585 * exist.
586 */
587 int buffer_migrate_page(struct address_space *mapping,
588 struct page *newpage, struct page *page, enum migrate_mode mode)
589 {
590 struct buffer_head *bh, *head;
591 int rc;
592
593 if (!page_has_buffers(page))
594 return migrate_page(mapping, newpage, page, mode);
595
596 head = page_buffers(page);
597
598 rc = migrate_page_move_mapping(mapping, newpage, page, head, mode, 0);
599
600 if (rc != MIGRATEPAGE_SUCCESS)
601 return rc;
602
603 /*
604 * In the async case, migrate_page_move_mapping locked the buffers
605 * with an IRQ-safe spinlock held. In the sync case, the buffers
606 * need to be locked now
607 */
608 if (mode != MIGRATE_ASYNC)
609 BUG_ON(!buffer_migrate_lock_buffers(head, mode));
610
611 ClearPagePrivate(page);
612 set_page_private(newpage, page_private(page));
613 set_page_private(page, 0);
614 put_page(page);
615 get_page(newpage);
616
617 bh = head;
618 do {
619 set_bh_page(bh, newpage, bh_offset(bh));
620 bh = bh->b_this_page;
621
622 } while (bh != head);
623
624 SetPagePrivate(newpage);
625
626 migrate_page_copy(newpage, page);
627
628 bh = head;
629 do {
630 unlock_buffer(bh);
631 put_bh(bh);
632 bh = bh->b_this_page;
633
634 } while (bh != head);
635
636 return MIGRATEPAGE_SUCCESS;
637 }
638 EXPORT_SYMBOL(buffer_migrate_page);
639 #endif
640
641 /*
642 * Writeback a page to clean the dirty state
643 */
644 static int writeout(struct address_space *mapping, struct page *page)
645 {
646 struct writeback_control wbc = {
647 .sync_mode = WB_SYNC_NONE,
648 .nr_to_write = 1,
649 .range_start = 0,
650 .range_end = LLONG_MAX,
651 .for_reclaim = 1
652 };
653 int rc;
654
655 if (!mapping->a_ops->writepage)
656 /* No write method for the address space */
657 return -EINVAL;
658
659 if (!clear_page_dirty_for_io(page))
660 /* Someone else already triggered a write */
661 return -EAGAIN;
662
663 /*
664 * A dirty page may imply that the underlying filesystem has
665 * the page on some queue. So the page must be clean for
666 * migration. Writeout may mean we loose the lock and the
667 * page state is no longer what we checked for earlier.
668 * At this point we know that the migration attempt cannot
669 * be successful.
670 */
671 remove_migration_ptes(page, page);
672
673 rc = mapping->a_ops->writepage(page, &wbc);
674
675 if (rc != AOP_WRITEPAGE_ACTIVATE)
676 /* unlocked. Relock */
677 lock_page(page);
678
679 return (rc < 0) ? -EIO : -EAGAIN;
680 }
681
682 /*
683 * Default handling if a filesystem does not provide a migration function.
684 */
685 static int fallback_migrate_page(struct address_space *mapping,
686 struct page *newpage, struct page *page, enum migrate_mode mode)
687 {
688 if (PageDirty(page)) {
689 /* Only writeback pages in full synchronous migration */
690 if (mode != MIGRATE_SYNC)
691 return -EBUSY;
692 return writeout(mapping, page);
693 }
694
695 /*
696 * Buffers may be managed in a filesystem specific way.
697 * We must have no buffers or drop them.
698 */
699 if (page_has_private(page) &&
700 !try_to_release_page(page, GFP_KERNEL))
701 return -EAGAIN;
702
703 return migrate_page(mapping, newpage, page, mode);
704 }
705
706 /*
707 * Move a page to a newly allocated page
708 * The page is locked and all ptes have been successfully removed.
709 *
710 * The new page will have replaced the old page if this function
711 * is successful.
712 *
713 * Return value:
714 * < 0 - error code
715 * MIGRATEPAGE_SUCCESS - success
716 */
717 static int move_to_new_page(struct page *newpage, struct page *page,
718 int page_was_mapped, enum migrate_mode mode)
719 {
720 struct address_space *mapping;
721 int rc;
722
723 /*
724 * Block others from accessing the page when we get around to
725 * establishing additional references. We are the only one
726 * holding a reference to the new page at this point.
727 */
728 if (!trylock_page(newpage))
729 BUG();
730
731 /* Prepare mapping for the new page.*/
732 newpage->index = page->index;
733 newpage->mapping = page->mapping;
734 if (PageSwapBacked(page))
735 SetPageSwapBacked(newpage);
736
737 mapping = page_mapping(page);
738 if (!mapping)
739 rc = migrate_page(mapping, newpage, page, mode);
740 else if (mapping->a_ops->migratepage)
741 /*
742 * Most pages have a mapping and most filesystems provide a
743 * migratepage callback. Anonymous pages are part of swap
744 * space which also has its own migratepage callback. This
745 * is the most common path for page migration.
746 */
747 rc = mapping->a_ops->migratepage(mapping,
748 newpage, page, mode);
749 else
750 rc = fallback_migrate_page(mapping, newpage, page, mode);
751
752 if (rc != MIGRATEPAGE_SUCCESS) {
753 newpage->mapping = NULL;
754 } else {
755 mem_cgroup_migrate(page, newpage, false);
756 if (page_was_mapped)
757 remove_migration_ptes(page, newpage);
758 page->mapping = NULL;
759 }
760
761 unlock_page(newpage);
762
763 return rc;
764 }
765
766 static int __unmap_and_move(struct page *page, struct page *newpage,
767 int force, enum migrate_mode mode)
768 {
769 int rc = -EAGAIN;
770 int page_was_mapped = 0;
771 struct anon_vma *anon_vma = NULL;
772
773 if (!trylock_page(page)) {
774 if (!force || mode == MIGRATE_ASYNC)
775 goto out;
776
777 /*
778 * It's not safe for direct compaction to call lock_page.
779 * For example, during page readahead pages are added locked
780 * to the LRU. Later, when the IO completes the pages are
781 * marked uptodate and unlocked. However, the queueing
782 * could be merging multiple pages for one bio (e.g.
783 * mpage_readpages). If an allocation happens for the
784 * second or third page, the process can end up locking
785 * the same page twice and deadlocking. Rather than
786 * trying to be clever about what pages can be locked,
787 * avoid the use of lock_page for direct compaction
788 * altogether.
789 */
790 if (current->flags & PF_MEMALLOC)
791 goto out;
792
793 lock_page(page);
794 }
795
796 if (PageWriteback(page)) {
797 /*
798 * Only in the case of a full synchronous migration is it
799 * necessary to wait for PageWriteback. In the async case,
800 * the retry loop is too short and in the sync-light case,
801 * the overhead of stalling is too much
802 */
803 if (mode != MIGRATE_SYNC) {
804 rc = -EBUSY;
805 goto out_unlock;
806 }
807 if (!force)
808 goto out_unlock;
809 wait_on_page_writeback(page);
810 }
811 /*
812 * By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
813 * we cannot notice that anon_vma is freed while we migrates a page.
814 * This get_anon_vma() delays freeing anon_vma pointer until the end
815 * of migration. File cache pages are no problem because of page_lock()
816 * File Caches may use write_page() or lock_page() in migration, then,
817 * just care Anon page here.
818 */
819 if (PageAnon(page) && !PageKsm(page)) {
820 /*
821 * Only page_lock_anon_vma_read() understands the subtleties of
822 * getting a hold on an anon_vma from outside one of its mms.
823 */
824 anon_vma = page_get_anon_vma(page);
825 if (anon_vma) {
826 /*
827 * Anon page
828 */
829 } else if (PageSwapCache(page)) {
830 /*
831 * We cannot be sure that the anon_vma of an unmapped
832 * swapcache page is safe to use because we don't
833 * know in advance if the VMA that this page belonged
834 * to still exists. If the VMA and others sharing the
835 * data have been freed, then the anon_vma could
836 * already be invalid.
837 *
838 * To avoid this possibility, swapcache pages get
839 * migrated but are not remapped when migration
840 * completes
841 */
842 } else {
843 goto out_unlock;
844 }
845 }
846
847 if (unlikely(isolated_balloon_page(page))) {
848 /*
849 * A ballooned page does not need any special attention from
850 * physical to virtual reverse mapping procedures.
851 * Skip any attempt to unmap PTEs or to remap swap cache,
852 * in order to avoid burning cycles at rmap level, and perform
853 * the page migration right away (proteced by page lock).
854 */
855 rc = balloon_page_migrate(newpage, page, mode);
856 goto out_unlock;
857 }
858
859 /*
860 * Corner case handling:
861 * 1. When a new swap-cache page is read into, it is added to the LRU
862 * and treated as swapcache but it has no rmap yet.
863 * Calling try_to_unmap() against a page->mapping==NULL page will
864 * trigger a BUG. So handle it here.
865 * 2. An orphaned page (see truncate_complete_page) might have
866 * fs-private metadata. The page can be picked up due to memory
867 * offlining. Everywhere else except page reclaim, the page is
868 * invisible to the vm, so the page can not be migrated. So try to
869 * free the metadata, so the page can be freed.
870 */
871 if (!page->mapping) {
872 VM_BUG_ON_PAGE(PageAnon(page), page);
873 if (page_has_private(page)) {
874 try_to_free_buffers(page);
875 goto out_unlock;
876 }
877 goto skip_unmap;
878 }
879
880 /* Establish migration ptes or remove ptes */
881 if (page_mapped(page)) {
882 try_to_unmap(page,
883 TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
884 page_was_mapped = 1;
885 }
886
887 skip_unmap:
888 if (!page_mapped(page))
889 rc = move_to_new_page(newpage, page, page_was_mapped, mode);
890
891 if (rc && page_was_mapped)
892 remove_migration_ptes(page, page);
893
894 /* Drop an anon_vma reference if we took one */
895 if (anon_vma)
896 put_anon_vma(anon_vma);
897
898 out_unlock:
899 unlock_page(page);
900 out:
901 return rc;
902 }
903
904 /*
905 * gcc 4.7 and 4.8 on arm get an ICEs when inlining unmap_and_move(). Work
906 * around it.
907 */
908 #if (GCC_VERSION >= 40700 && GCC_VERSION < 40900) && defined(CONFIG_ARM)
909 #define ICE_noinline noinline
910 #else
911 #define ICE_noinline
912 #endif
913
914 /*
915 * Obtain the lock on page, remove all ptes and migrate the page
916 * to the newly allocated page in newpage.
917 */
918 static ICE_noinline int unmap_and_move(new_page_t get_new_page,
919 free_page_t put_new_page,
920 unsigned long private, struct page *page,
921 int force, enum migrate_mode mode)
922 {
923 int rc = 0;
924 int *result = NULL;
925 struct page *newpage = get_new_page(page, private, &result);
926
927 if (!newpage)
928 return -ENOMEM;
929
930 if (page_count(page) == 1) {
931 /* page was freed from under us. So we are done. */
932 goto out;
933 }
934
935 if (unlikely(PageTransHuge(page)))
936 if (unlikely(split_huge_page(page)))
937 goto out;
938
939 rc = __unmap_and_move(page, newpage, force, mode);
940
941 out:
942 if (rc != -EAGAIN) {
943 /*
944 * A page that has been migrated has all references
945 * removed and will be freed. A page that has not been
946 * migrated will have kepts its references and be
947 * restored.
948 */
949 list_del(&page->lru);
950 dec_zone_page_state(page, NR_ISOLATED_ANON +
951 page_is_file_cache(page));
952 putback_lru_page(page);
953 }
954
955 /*
956 * If migration was not successful and there's a freeing callback, use
957 * it. Otherwise, putback_lru_page() will drop the reference grabbed
958 * during isolation.
959 */
960 if (rc != MIGRATEPAGE_SUCCESS && put_new_page) {
961 ClearPageSwapBacked(newpage);
962 put_new_page(newpage, private);
963 } else if (unlikely(__is_movable_balloon_page(newpage))) {
964 /* drop our reference, page already in the balloon */
965 put_page(newpage);
966 } else
967 putback_lru_page(newpage);
968
969 if (result) {
970 if (rc)
971 *result = rc;
972 else
973 *result = page_to_nid(newpage);
974 }
975 return rc;
976 }
977
978 /*
979 * Counterpart of unmap_and_move_page() for hugepage migration.
980 *
981 * This function doesn't wait the completion of hugepage I/O
982 * because there is no race between I/O and migration for hugepage.
983 * Note that currently hugepage I/O occurs only in direct I/O
984 * where no lock is held and PG_writeback is irrelevant,
985 * and writeback status of all subpages are counted in the reference
986 * count of the head page (i.e. if all subpages of a 2MB hugepage are
987 * under direct I/O, the reference of the head page is 512 and a bit more.)
988 * This means that when we try to migrate hugepage whose subpages are
989 * doing direct I/O, some references remain after try_to_unmap() and
990 * hugepage migration fails without data corruption.
991 *
992 * There is also no race when direct I/O is issued on the page under migration,
993 * because then pte is replaced with migration swap entry and direct I/O code
994 * will wait in the page fault for migration to complete.
995 */
996 static int unmap_and_move_huge_page(new_page_t get_new_page,
997 free_page_t put_new_page, unsigned long private,
998 struct page *hpage, int force,
999 enum migrate_mode mode)
1000 {
1001 int rc = 0;
1002 int *result = NULL;
1003 int page_was_mapped = 0;
1004 struct page *new_hpage;
1005 struct anon_vma *anon_vma = NULL;
1006
1007 /*
1008 * Movability of hugepages depends on architectures and hugepage size.
1009 * This check is necessary because some callers of hugepage migration
1010 * like soft offline and memory hotremove don't walk through page
1011 * tables or check whether the hugepage is pmd-based or not before
1012 * kicking migration.
1013 */
1014 if (!hugepage_migration_supported(page_hstate(hpage))) {
1015 putback_active_hugepage(hpage);
1016 return -ENOSYS;
1017 }
1018
1019 new_hpage = get_new_page(hpage, private, &result);
1020 if (!new_hpage)
1021 return -ENOMEM;
1022
1023 rc = -EAGAIN;
1024
1025 if (!trylock_page(hpage)) {
1026 if (!force || mode != MIGRATE_SYNC)
1027 goto out;
1028 lock_page(hpage);
1029 }
1030
1031 if (PageAnon(hpage))
1032 anon_vma = page_get_anon_vma(hpage);
1033
1034 if (page_mapped(hpage)) {
1035 try_to_unmap(hpage,
1036 TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
1037 page_was_mapped = 1;
1038 }
1039
1040 if (!page_mapped(hpage))
1041 rc = move_to_new_page(new_hpage, hpage, page_was_mapped, mode);
1042
1043 if (rc != MIGRATEPAGE_SUCCESS && page_was_mapped)
1044 remove_migration_ptes(hpage, hpage);
1045
1046 if (anon_vma)
1047 put_anon_vma(anon_vma);
1048
1049 if (rc == MIGRATEPAGE_SUCCESS)
1050 hugetlb_cgroup_migrate(hpage, new_hpage);
1051
1052 unlock_page(hpage);
1053 out:
1054 if (rc != -EAGAIN)
1055 putback_active_hugepage(hpage);
1056
1057 /*
1058 * If migration was not successful and there's a freeing callback, use
1059 * it. Otherwise, put_page() will drop the reference grabbed during
1060 * isolation.
1061 */
1062 if (rc != MIGRATEPAGE_SUCCESS && put_new_page)
1063 put_new_page(new_hpage, private);
1064 else
1065 put_page(new_hpage);
1066
1067 if (result) {
1068 if (rc)
1069 *result = rc;
1070 else
1071 *result = page_to_nid(new_hpage);
1072 }
1073 return rc;
1074 }
1075
1076 /*
1077 * migrate_pages - migrate the pages specified in a list, to the free pages
1078 * supplied as the target for the page migration
1079 *
1080 * @from: The list of pages to be migrated.
1081 * @get_new_page: The function used to allocate free pages to be used
1082 * as the target of the page migration.
1083 * @put_new_page: The function used to free target pages if migration
1084 * fails, or NULL if no special handling is necessary.
1085 * @private: Private data to be passed on to get_new_page()
1086 * @mode: The migration mode that specifies the constraints for
1087 * page migration, if any.
1088 * @reason: The reason for page migration.
1089 *
1090 * The function returns after 10 attempts or if no pages are movable any more
1091 * because the list has become empty or no retryable pages exist any more.
1092 * The caller should call putback_lru_pages() to return pages to the LRU
1093 * or free list only if ret != 0.
1094 *
1095 * Returns the number of pages that were not migrated, or an error code.
1096 */
1097 int migrate_pages(struct list_head *from, new_page_t get_new_page,
1098 free_page_t put_new_page, unsigned long private,
1099 enum migrate_mode mode, int reason)
1100 {
1101 int retry = 1;
1102 int nr_failed = 0;
1103 int nr_succeeded = 0;
1104 int pass = 0;
1105 struct page *page;
1106 struct page *page2;
1107 int swapwrite = current->flags & PF_SWAPWRITE;
1108 int rc;
1109
1110 if (!swapwrite)
1111 current->flags |= PF_SWAPWRITE;
1112
1113 for(pass = 0; pass < 10 && retry; pass++) {
1114 retry = 0;
1115
1116 list_for_each_entry_safe(page, page2, from, lru) {
1117 cond_resched();
1118
1119 if (PageHuge(page))
1120 rc = unmap_and_move_huge_page(get_new_page,
1121 put_new_page, private, page,
1122 pass > 2, mode);
1123 else
1124 rc = unmap_and_move(get_new_page, put_new_page,
1125 private, page, pass > 2, mode);
1126
1127 switch(rc) {
1128 case -ENOMEM:
1129 goto out;
1130 case -EAGAIN:
1131 retry++;
1132 break;
1133 case MIGRATEPAGE_SUCCESS:
1134 nr_succeeded++;
1135 break;
1136 default:
1137 /*
1138 * Permanent failure (-EBUSY, -ENOSYS, etc.):
1139 * unlike -EAGAIN case, the failed page is
1140 * removed from migration page list and not
1141 * retried in the next outer loop.
1142 */
1143 nr_failed++;
1144 break;
1145 }
1146 }
1147 }
1148 rc = nr_failed + retry;
1149 out:
1150 if (nr_succeeded)
1151 count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
1152 if (nr_failed)
1153 count_vm_events(PGMIGRATE_FAIL, nr_failed);
1154 trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason);
1155
1156 if (!swapwrite)
1157 current->flags &= ~PF_SWAPWRITE;
1158
1159 return rc;
1160 }
1161
1162 #ifdef CONFIG_NUMA
1163 /*
1164 * Move a list of individual pages
1165 */
1166 struct page_to_node {
1167 unsigned long addr;
1168 struct page *page;
1169 int node;
1170 int status;
1171 };
1172
1173 static struct page *new_page_node(struct page *p, unsigned long private,
1174 int **result)
1175 {
1176 struct page_to_node *pm = (struct page_to_node *)private;
1177
1178 while (pm->node != MAX_NUMNODES && pm->page != p)
1179 pm++;
1180
1181 if (pm->node == MAX_NUMNODES)
1182 return NULL;
1183
1184 *result = &pm->status;
1185
1186 if (PageHuge(p))
1187 return alloc_huge_page_node(page_hstate(compound_head(p)),
1188 pm->node);
1189 else
1190 return alloc_pages_exact_node(pm->node,
1191 GFP_HIGHUSER_MOVABLE | __GFP_THISNODE, 0);
1192 }
1193
1194 /*
1195 * Move a set of pages as indicated in the pm array. The addr
1196 * field must be set to the virtual address of the page to be moved
1197 * and the node number must contain a valid target node.
1198 * The pm array ends with node = MAX_NUMNODES.
1199 */
1200 static int do_move_page_to_node_array(struct mm_struct *mm,
1201 struct page_to_node *pm,
1202 int migrate_all)
1203 {
1204 int err;
1205 struct page_to_node *pp;
1206 LIST_HEAD(pagelist);
1207
1208 down_read(&mm->mmap_sem);
1209
1210 /*
1211 * Build a list of pages to migrate
1212 */
1213 for (pp = pm; pp->node != MAX_NUMNODES; pp++) {
1214 struct vm_area_struct *vma;
1215 struct page *page;
1216
1217 err = -EFAULT;
1218 vma = find_vma(mm, pp->addr);
1219 if (!vma || pp->addr < vma->vm_start || !vma_migratable(vma))
1220 goto set_status;
1221
1222 page = follow_page(vma, pp->addr, FOLL_GET|FOLL_SPLIT);
1223
1224 err = PTR_ERR(page);
1225 if (IS_ERR(page))
1226 goto set_status;
1227
1228 err = -ENOENT;
1229 if (!page)
1230 goto set_status;
1231
1232 /* Use PageReserved to check for zero page */
1233 if (PageReserved(page))
1234 goto put_and_set;
1235
1236 pp->page = page;
1237 err = page_to_nid(page);
1238
1239 if (err == pp->node)
1240 /*
1241 * Node already in the right place
1242 */
1243 goto put_and_set;
1244
1245 err = -EACCES;
1246 if (page_mapcount(page) > 1 &&
1247 !migrate_all)
1248 goto put_and_set;
1249
1250 if (PageHuge(page)) {
1251 if (PageHead(page))
1252 isolate_huge_page(page, &pagelist);
1253 goto put_and_set;
1254 }
1255
1256 err = isolate_lru_page(page);
1257 if (!err) {
1258 list_add_tail(&page->lru, &pagelist);
1259 inc_zone_page_state(page, NR_ISOLATED_ANON +
1260 page_is_file_cache(page));
1261 }
1262 put_and_set:
1263 /*
1264 * Either remove the duplicate refcount from
1265 * isolate_lru_page() or drop the page ref if it was
1266 * not isolated.
1267 */
1268 put_page(page);
1269 set_status:
1270 pp->status = err;
1271 }
1272
1273 err = 0;
1274 if (!list_empty(&pagelist)) {
1275 err = migrate_pages(&pagelist, new_page_node, NULL,
1276 (unsigned long)pm, MIGRATE_SYNC, MR_SYSCALL);
1277 if (err)
1278 putback_movable_pages(&pagelist);
1279 }
1280
1281 up_read(&mm->mmap_sem);
1282 return err;
1283 }
1284
1285 /*
1286 * Migrate an array of page address onto an array of nodes and fill
1287 * the corresponding array of status.
1288 */
1289 static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
1290 unsigned long nr_pages,
1291 const void __user * __user *pages,
1292 const int __user *nodes,
1293 int __user *status, int flags)
1294 {
1295 struct page_to_node *pm;
1296 unsigned long chunk_nr_pages;
1297 unsigned long chunk_start;
1298 int err;
1299
1300 err = -ENOMEM;
1301 pm = (struct page_to_node *)__get_free_page(GFP_KERNEL);
1302 if (!pm)
1303 goto out;
1304
1305 migrate_prep();
1306
1307 /*
1308 * Store a chunk of page_to_node array in a page,
1309 * but keep the last one as a marker
1310 */
1311 chunk_nr_pages = (PAGE_SIZE / sizeof(struct page_to_node)) - 1;
1312
1313 for (chunk_start = 0;
1314 chunk_start < nr_pages;
1315 chunk_start += chunk_nr_pages) {
1316 int j;
1317
1318 if (chunk_start + chunk_nr_pages > nr_pages)
1319 chunk_nr_pages = nr_pages - chunk_start;
1320
1321 /* fill the chunk pm with addrs and nodes from user-space */
1322 for (j = 0; j < chunk_nr_pages; j++) {
1323 const void __user *p;
1324 int node;
1325
1326 err = -EFAULT;
1327 if (get_user(p, pages + j + chunk_start))
1328 goto out_pm;
1329 pm[j].addr = (unsigned long) p;
1330
1331 if (get_user(node, nodes + j + chunk_start))
1332 goto out_pm;
1333
1334 err = -ENODEV;
1335 if (node < 0 || node >= MAX_NUMNODES)
1336 goto out_pm;
1337
1338 if (!node_state(node, N_MEMORY))
1339 goto out_pm;
1340
1341 err = -EACCES;
1342 if (!node_isset(node, task_nodes))
1343 goto out_pm;
1344
1345 pm[j].node = node;
1346 }
1347
1348 /* End marker for this chunk */
1349 pm[chunk_nr_pages].node = MAX_NUMNODES;
1350
1351 /* Migrate this chunk */
1352 err = do_move_page_to_node_array(mm, pm,
1353 flags & MPOL_MF_MOVE_ALL);
1354 if (err < 0)
1355 goto out_pm;
1356
1357 /* Return status information */
1358 for (j = 0; j < chunk_nr_pages; j++)
1359 if (put_user(pm[j].status, status + j + chunk_start)) {
1360 err = -EFAULT;
1361 goto out_pm;
1362 }
1363 }
1364 err = 0;
1365
1366 out_pm:
1367 free_page((unsigned long)pm);
1368 out:
1369 return err;
1370 }
1371
1372 /*
1373 * Determine the nodes of an array of pages and store it in an array of status.
1374 */
1375 static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
1376 const void __user **pages, int *status)
1377 {
1378 unsigned long i;
1379
1380 down_read(&mm->mmap_sem);
1381
1382 for (i = 0; i < nr_pages; i++) {
1383 unsigned long addr = (unsigned long)(*pages);
1384 struct vm_area_struct *vma;
1385 struct page *page;
1386 int err = -EFAULT;
1387
1388 vma = find_vma(mm, addr);
1389 if (!vma || addr < vma->vm_start)
1390 goto set_status;
1391
1392 page = follow_page(vma, addr, 0);
1393
1394 err = PTR_ERR(page);
1395 if (IS_ERR(page))
1396 goto set_status;
1397
1398 err = -ENOENT;
1399 /* Use PageReserved to check for zero page */
1400 if (!page || PageReserved(page))
1401 goto set_status;
1402
1403 err = page_to_nid(page);
1404 set_status:
1405 *status = err;
1406
1407 pages++;
1408 status++;
1409 }
1410
1411 up_read(&mm->mmap_sem);
1412 }
1413
1414 /*
1415 * Determine the nodes of a user array of pages and store it in
1416 * a user array of status.
1417 */
1418 static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
1419 const void __user * __user *pages,
1420 int __user *status)
1421 {
1422 #define DO_PAGES_STAT_CHUNK_NR 16
1423 const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
1424 int chunk_status[DO_PAGES_STAT_CHUNK_NR];
1425
1426 while (nr_pages) {
1427 unsigned long chunk_nr;
1428
1429 chunk_nr = nr_pages;
1430 if (chunk_nr > DO_PAGES_STAT_CHUNK_NR)
1431 chunk_nr = DO_PAGES_STAT_CHUNK_NR;
1432
1433 if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages)))
1434 break;
1435
1436 do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
1437
1438 if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
1439 break;
1440
1441 pages += chunk_nr;
1442 status += chunk_nr;
1443 nr_pages -= chunk_nr;
1444 }
1445 return nr_pages ? -EFAULT : 0;
1446 }
1447
1448 /*
1449 * Move a list of pages in the address space of the currently executing
1450 * process.
1451 */
1452 SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
1453 const void __user * __user *, pages,
1454 const int __user *, nodes,
1455 int __user *, status, int, flags)
1456 {
1457 const struct cred *cred = current_cred(), *tcred;
1458 struct task_struct *task;
1459 struct mm_struct *mm;
1460 int err;
1461 nodemask_t task_nodes;
1462
1463 /* Check flags */
1464 if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
1465 return -EINVAL;
1466
1467 if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
1468 return -EPERM;
1469
1470 /* Find the mm_struct */
1471 rcu_read_lock();
1472 task = pid ? find_task_by_vpid(pid) : current;
1473 if (!task) {
1474 rcu_read_unlock();
1475 return -ESRCH;
1476 }
1477 get_task_struct(task);
1478
1479 /*
1480 * Check if this process has the right to modify the specified
1481 * process. The right exists if the process has administrative
1482 * capabilities, superuser privileges or the same
1483 * userid as the target process.
1484 */
1485 tcred = __task_cred(task);
1486 if (!uid_eq(cred->euid, tcred->suid) && !uid_eq(cred->euid, tcred->uid) &&
1487 !uid_eq(cred->uid, tcred->suid) && !uid_eq(cred->uid, tcred->uid) &&
1488 !capable(CAP_SYS_NICE)) {
1489 rcu_read_unlock();
1490 err = -EPERM;
1491 goto out;
1492 }
1493 rcu_read_unlock();
1494
1495 err = security_task_movememory(task);
1496 if (err)
1497 goto out;
1498
1499 task_nodes = cpuset_mems_allowed(task);
1500 mm = get_task_mm(task);
1501 put_task_struct(task);
1502
1503 if (!mm)
1504 return -EINVAL;
1505
1506 if (nodes)
1507 err = do_pages_move(mm, task_nodes, nr_pages, pages,
1508 nodes, status, flags);
1509 else
1510 err = do_pages_stat(mm, nr_pages, pages, status);
1511
1512 mmput(mm);
1513 return err;
1514
1515 out:
1516 put_task_struct(task);
1517 return err;
1518 }
1519
1520 #ifdef CONFIG_NUMA_BALANCING
1521 /*
1522 * Returns true if this is a safe migration target node for misplaced NUMA
1523 * pages. Currently it only checks the watermarks which crude
1524 */
1525 static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
1526 unsigned long nr_migrate_pages)
1527 {
1528 int z;
1529 for (z = pgdat->nr_zones - 1; z >= 0; z--) {
1530 struct zone *zone = pgdat->node_zones + z;
1531
1532 if (!populated_zone(zone))
1533 continue;
1534
1535 if (!zone_reclaimable(zone))
1536 continue;
1537
1538 /* Avoid waking kswapd by allocating pages_to_migrate pages. */
1539 if (!zone_watermark_ok(zone, 0,
1540 high_wmark_pages(zone) +
1541 nr_migrate_pages,
1542 0, 0))
1543 continue;
1544 return true;
1545 }
1546 return false;
1547 }
1548
1549 static struct page *alloc_misplaced_dst_page(struct page *page,
1550 unsigned long data,
1551 int **result)
1552 {
1553 int nid = (int) data;
1554 struct page *newpage;
1555
1556 newpage = alloc_pages_exact_node(nid,
1557 (GFP_HIGHUSER_MOVABLE |
1558 __GFP_THISNODE | __GFP_NOMEMALLOC |
1559 __GFP_NORETRY | __GFP_NOWARN) &
1560 ~GFP_IOFS, 0);
1561
1562 return newpage;
1563 }
1564
1565 /*
1566 * page migration rate limiting control.
1567 * Do not migrate more than @pages_to_migrate in a @migrate_interval_millisecs
1568 * window of time. Default here says do not migrate more than 1280M per second.
1569 */
1570 static unsigned int migrate_interval_millisecs __read_mostly = 100;
1571 static unsigned int ratelimit_pages __read_mostly = 128 << (20 - PAGE_SHIFT);
1572
1573 /* Returns true if the node is migrate rate-limited after the update */
1574 static bool numamigrate_update_ratelimit(pg_data_t *pgdat,
1575 unsigned long nr_pages)
1576 {
1577 /*
1578 * Rate-limit the amount of data that is being migrated to a node.
1579 * Optimal placement is no good if the memory bus is saturated and
1580 * all the time is being spent migrating!
1581 */
1582 if (time_after(jiffies, pgdat->numabalancing_migrate_next_window)) {
1583 spin_lock(&pgdat->numabalancing_migrate_lock);
1584 pgdat->numabalancing_migrate_nr_pages = 0;
1585 pgdat->numabalancing_migrate_next_window = jiffies +
1586 msecs_to_jiffies(migrate_interval_millisecs);
1587 spin_unlock(&pgdat->numabalancing_migrate_lock);
1588 }
1589 if (pgdat->numabalancing_migrate_nr_pages > ratelimit_pages) {
1590 trace_mm_numa_migrate_ratelimit(current, pgdat->node_id,
1591 nr_pages);
1592 return true;
1593 }
1594
1595 /*
1596 * This is an unlocked non-atomic update so errors are possible.
1597 * The consequences are failing to migrate when we potentiall should
1598 * have which is not severe enough to warrant locking. If it is ever
1599 * a problem, it can be converted to a per-cpu counter.
1600 */
1601 pgdat->numabalancing_migrate_nr_pages += nr_pages;
1602 return false;
1603 }
1604
1605 static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
1606 {
1607 int page_lru;
1608
1609 VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page);
1610
1611 /* Avoid migrating to a node that is nearly full */
1612 if (!migrate_balanced_pgdat(pgdat, 1UL << compound_order(page)))
1613 return 0;
1614
1615 if (isolate_lru_page(page))
1616 return 0;
1617
1618 /*
1619 * migrate_misplaced_transhuge_page() skips page migration's usual
1620 * check on page_count(), so we must do it here, now that the page
1621 * has been isolated: a GUP pin, or any other pin, prevents migration.
1622 * The expected page count is 3: 1 for page's mapcount and 1 for the
1623 * caller's pin and 1 for the reference taken by isolate_lru_page().
1624 */
1625 if (PageTransHuge(page) && page_count(page) != 3) {
1626 putback_lru_page(page);
1627 return 0;
1628 }
1629
1630 page_lru = page_is_file_cache(page);
1631 mod_zone_page_state(page_zone(page), NR_ISOLATED_ANON + page_lru,
1632 hpage_nr_pages(page));
1633
1634 /*
1635 * Isolating the page has taken another reference, so the
1636 * caller's reference can be safely dropped without the page
1637 * disappearing underneath us during migration.
1638 */
1639 put_page(page);
1640 return 1;
1641 }
1642
1643 bool pmd_trans_migrating(pmd_t pmd)
1644 {
1645 struct page *page = pmd_page(pmd);
1646 return PageLocked(page);
1647 }
1648
1649 /*
1650 * Attempt to migrate a misplaced page to the specified destination
1651 * node. Caller is expected to have an elevated reference count on
1652 * the page that will be dropped by this function before returning.
1653 */
1654 int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
1655 int node)
1656 {
1657 pg_data_t *pgdat = NODE_DATA(node);
1658 int isolated;
1659 int nr_remaining;
1660 LIST_HEAD(migratepages);
1661
1662 /*
1663 * Don't migrate file pages that are mapped in multiple processes
1664 * with execute permissions as they are probably shared libraries.
1665 */
1666 if (page_mapcount(page) != 1 && page_is_file_cache(page) &&
1667 (vma->vm_flags & VM_EXEC))
1668 goto out;
1669
1670 /*
1671 * Rate-limit the amount of data that is being migrated to a node.
1672 * Optimal placement is no good if the memory bus is saturated and
1673 * all the time is being spent migrating!
1674 */
1675 if (numamigrate_update_ratelimit(pgdat, 1))
1676 goto out;
1677
1678 isolated = numamigrate_isolate_page(pgdat, page);
1679 if (!isolated)
1680 goto out;
1681
1682 list_add(&page->lru, &migratepages);
1683 nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page,
1684 NULL, node, MIGRATE_ASYNC,
1685 MR_NUMA_MISPLACED);
1686 if (nr_remaining) {
1687 if (!list_empty(&migratepages)) {
1688 list_del(&page->lru);
1689 dec_zone_page_state(page, NR_ISOLATED_ANON +
1690 page_is_file_cache(page));
1691 putback_lru_page(page);
1692 }
1693 isolated = 0;
1694 } else
1695 count_vm_numa_event(NUMA_PAGE_MIGRATE);
1696 BUG_ON(!list_empty(&migratepages));
1697 return isolated;
1698
1699 out:
1700 put_page(page);
1701 return 0;
1702 }
1703 #endif /* CONFIG_NUMA_BALANCING */
1704
1705 #if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
1706 /*
1707 * Migrates a THP to a given target node. page must be locked and is unlocked
1708 * before returning.
1709 */
1710 int migrate_misplaced_transhuge_page(struct mm_struct *mm,
1711 struct vm_area_struct *vma,
1712 pmd_t *pmd, pmd_t entry,
1713 unsigned long address,
1714 struct page *page, int node)
1715 {
1716 spinlock_t *ptl;
1717 pg_data_t *pgdat = NODE_DATA(node);
1718 int isolated = 0;
1719 struct page *new_page = NULL;
1720 int page_lru = page_is_file_cache(page);
1721 unsigned long mmun_start = address & HPAGE_PMD_MASK;
1722 unsigned long mmun_end = mmun_start + HPAGE_PMD_SIZE;
1723 pmd_t orig_entry;
1724
1725 /*
1726 * Rate-limit the amount of data that is being migrated to a node.
1727 * Optimal placement is no good if the memory bus is saturated and
1728 * all the time is being spent migrating!
1729 */
1730 if (numamigrate_update_ratelimit(pgdat, HPAGE_PMD_NR))
1731 goto out_dropref;
1732
1733 new_page = alloc_pages_node(node,
1734 (GFP_TRANSHUGE | __GFP_THISNODE) & ~__GFP_WAIT,
1735 HPAGE_PMD_ORDER);
1736 if (!new_page)
1737 goto out_fail;
1738
1739 isolated = numamigrate_isolate_page(pgdat, page);
1740 if (!isolated) {
1741 put_page(new_page);
1742 goto out_fail;
1743 }
1744
1745 if (mm_tlb_flush_pending(mm))
1746 flush_tlb_range(vma, mmun_start, mmun_end);
1747
1748 /* Prepare a page as a migration target */
1749 __set_page_locked(new_page);
1750 SetPageSwapBacked(new_page);
1751
1752 /* anon mapping, we can simply copy page->mapping to the new page: */
1753 new_page->mapping = page->mapping;
1754 new_page->index = page->index;
1755 migrate_page_copy(new_page, page);
1756 WARN_ON(PageLRU(new_page));
1757
1758 /* Recheck the target PMD */
1759 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1760 ptl = pmd_lock(mm, pmd);
1761 if (unlikely(!pmd_same(*pmd, entry) || page_count(page) != 2)) {
1762 fail_putback:
1763 spin_unlock(ptl);
1764 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1765
1766 /* Reverse changes made by migrate_page_copy() */
1767 if (TestClearPageActive(new_page))
1768 SetPageActive(page);
1769 if (TestClearPageUnevictable(new_page))
1770 SetPageUnevictable(page);
1771 mlock_migrate_page(page, new_page);
1772
1773 unlock_page(new_page);
1774 put_page(new_page); /* Free it */
1775
1776 /* Retake the callers reference and putback on LRU */
1777 get_page(page);
1778 putback_lru_page(page);
1779 mod_zone_page_state(page_zone(page),
1780 NR_ISOLATED_ANON + page_lru, -HPAGE_PMD_NR);
1781
1782 goto out_unlock;
1783 }
1784
1785 orig_entry = *pmd;
1786 entry = mk_pmd(new_page, vma->vm_page_prot);
1787 entry = pmd_mkhuge(entry);
1788 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1789
1790 /*
1791 * Clear the old entry under pagetable lock and establish the new PTE.
1792 * Any parallel GUP will either observe the old page blocking on the
1793 * page lock, block on the page table lock or observe the new page.
1794 * The SetPageUptodate on the new page and page_add_new_anon_rmap
1795 * guarantee the copy is visible before the pagetable update.
1796 */
1797 flush_cache_range(vma, mmun_start, mmun_end);
1798 page_add_anon_rmap(new_page, vma, mmun_start);
1799 pmdp_clear_flush_notify(vma, mmun_start, pmd);
1800 set_pmd_at(mm, mmun_start, pmd, entry);
1801 flush_tlb_range(vma, mmun_start, mmun_end);
1802 update_mmu_cache_pmd(vma, address, &entry);
1803
1804 if (page_count(page) != 2) {
1805 set_pmd_at(mm, mmun_start, pmd, orig_entry);
1806 flush_tlb_range(vma, mmun_start, mmun_end);
1807 mmu_notifier_invalidate_range(mm, mmun_start, mmun_end);
1808 update_mmu_cache_pmd(vma, address, &entry);
1809 page_remove_rmap(new_page);
1810 goto fail_putback;
1811 }
1812
1813 mem_cgroup_migrate(page, new_page, false);
1814
1815 page_remove_rmap(page);
1816
1817 spin_unlock(ptl);
1818 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1819
1820 /* Take an "isolate" reference and put new page on the LRU. */
1821 get_page(new_page);
1822 putback_lru_page(new_page);
1823
1824 unlock_page(new_page);
1825 unlock_page(page);
1826 put_page(page); /* Drop the rmap reference */
1827 put_page(page); /* Drop the LRU isolation reference */
1828
1829 count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR);
1830 count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR);
1831
1832 mod_zone_page_state(page_zone(page),
1833 NR_ISOLATED_ANON + page_lru,
1834 -HPAGE_PMD_NR);
1835 return isolated;
1836
1837 out_fail:
1838 count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
1839 out_dropref:
1840 ptl = pmd_lock(mm, pmd);
1841 if (pmd_same(*pmd, entry)) {
1842 entry = pmd_modify(entry, vma->vm_page_prot);
1843 set_pmd_at(mm, mmun_start, pmd, entry);
1844 update_mmu_cache_pmd(vma, address, &entry);
1845 }
1846 spin_unlock(ptl);
1847
1848 out_unlock:
1849 unlock_page(page);
1850 put_page(page);
1851 return 0;
1852 }
1853 #endif /* CONFIG_NUMA_BALANCING */
1854
1855 #endif /* CONFIG_NUMA */