Loading...
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Memory Migration functionality - linux/mm/migrate.c
4 *
5 * Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter
6 *
7 * Page migration was first developed in the context of the memory hotplug
8 * project. The main authors of the migration code are:
9 *
10 * IWAMOTO Toshihiro <iwamoto@valinux.co.jp>
11 * Hirokazu Takahashi <taka@valinux.co.jp>
12 * Dave Hansen <haveblue@us.ibm.com>
13 * Christoph Lameter
14 */
15
16#include <linux/migrate.h>
17#include <linux/export.h>
18#include <linux/swap.h>
19#include <linux/swapops.h>
20#include <linux/pagemap.h>
21#include <linux/buffer_head.h>
22#include <linux/mm_inline.h>
23#include <linux/nsproxy.h>
24#include <linux/pagevec.h>
25#include <linux/ksm.h>
26#include <linux/rmap.h>
27#include <linux/topology.h>
28#include <linux/cpu.h>
29#include <linux/cpuset.h>
30#include <linux/writeback.h>
31#include <linux/mempolicy.h>
32#include <linux/vmalloc.h>
33#include <linux/security.h>
34#include <linux/backing-dev.h>
35#include <linux/compaction.h>
36#include <linux/syscalls.h>
37#include <linux/compat.h>
38#include <linux/hugetlb.h>
39#include <linux/hugetlb_cgroup.h>
40#include <linux/gfp.h>
41#include <linux/pagewalk.h>
42#include <linux/pfn_t.h>
43#include <linux/memremap.h>
44#include <linux/userfaultfd_k.h>
45#include <linux/balloon_compaction.h>
46#include <linux/mmu_notifier.h>
47#include <linux/page_idle.h>
48#include <linux/page_owner.h>
49#include <linux/sched/mm.h>
50#include <linux/ptrace.h>
51
52#include <asm/tlbflush.h>
53
54#define CREATE_TRACE_POINTS
55#include <trace/events/migrate.h>
56
57#include "internal.h"
58
59/*
60 * migrate_prep() needs to be called before we start compiling a list of pages
61 * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
62 * undesirable, use migrate_prep_local()
63 */
64int migrate_prep(void)
65{
66 /*
67 * Clear the LRU lists so pages can be isolated.
68 * Note that pages may be moved off the LRU after we have
69 * drained them. Those pages will fail to migrate like other
70 * pages that may be busy.
71 */
72 lru_add_drain_all();
73
74 return 0;
75}
76
77/* Do the necessary work of migrate_prep but not if it involves other CPUs */
78int migrate_prep_local(void)
79{
80 lru_add_drain();
81
82 return 0;
83}
84
85int isolate_movable_page(struct page *page, isolate_mode_t mode)
86{
87 struct address_space *mapping;
88
89 /*
90 * Avoid burning cycles with pages that are yet under __free_pages(),
91 * or just got freed under us.
92 *
93 * In case we 'win' a race for a movable page being freed under us and
94 * raise its refcount preventing __free_pages() from doing its job
95 * the put_page() at the end of this block will take care of
96 * release this page, thus avoiding a nasty leakage.
97 */
98 if (unlikely(!get_page_unless_zero(page)))
99 goto out;
100
101 /*
102 * Check PageMovable before holding a PG_lock because page's owner
103 * assumes anybody doesn't touch PG_lock of newly allocated page
104 * so unconditionally grabbing the lock ruins page's owner side.
105 */
106 if (unlikely(!__PageMovable(page)))
107 goto out_putpage;
108 /*
109 * As movable pages are not isolated from LRU lists, concurrent
110 * compaction threads can race against page migration functions
111 * as well as race against the releasing a page.
112 *
113 * In order to avoid having an already isolated movable page
114 * being (wrongly) re-isolated while it is under migration,
115 * or to avoid attempting to isolate pages being released,
116 * lets be sure we have the page lock
117 * before proceeding with the movable page isolation steps.
118 */
119 if (unlikely(!trylock_page(page)))
120 goto out_putpage;
121
122 if (!PageMovable(page) || PageIsolated(page))
123 goto out_no_isolated;
124
125 mapping = page_mapping(page);
126 VM_BUG_ON_PAGE(!mapping, page);
127
128 if (!mapping->a_ops->isolate_page(page, mode))
129 goto out_no_isolated;
130
131 /* Driver shouldn't use PG_isolated bit of page->flags */
132 WARN_ON_ONCE(PageIsolated(page));
133 __SetPageIsolated(page);
134 unlock_page(page);
135
136 return 0;
137
138out_no_isolated:
139 unlock_page(page);
140out_putpage:
141 put_page(page);
142out:
143 return -EBUSY;
144}
145
146/* It should be called on page which is PG_movable */
147void putback_movable_page(struct page *page)
148{
149 struct address_space *mapping;
150
151 VM_BUG_ON_PAGE(!PageLocked(page), page);
152 VM_BUG_ON_PAGE(!PageMovable(page), page);
153 VM_BUG_ON_PAGE(!PageIsolated(page), page);
154
155 mapping = page_mapping(page);
156 mapping->a_ops->putback_page(page);
157 __ClearPageIsolated(page);
158}
159
160/*
161 * Put previously isolated pages back onto the appropriate lists
162 * from where they were once taken off for compaction/migration.
163 *
164 * This function shall be used whenever the isolated pageset has been
165 * built from lru, balloon, hugetlbfs page. See isolate_migratepages_range()
166 * and isolate_huge_page().
167 */
168void putback_movable_pages(struct list_head *l)
169{
170 struct page *page;
171 struct page *page2;
172
173 list_for_each_entry_safe(page, page2, l, lru) {
174 if (unlikely(PageHuge(page))) {
175 putback_active_hugepage(page);
176 continue;
177 }
178 list_del(&page->lru);
179 /*
180 * We isolated non-lru movable page so here we can use
181 * __PageMovable because LRU page's mapping cannot have
182 * PAGE_MAPPING_MOVABLE.
183 */
184 if (unlikely(__PageMovable(page))) {
185 VM_BUG_ON_PAGE(!PageIsolated(page), page);
186 lock_page(page);
187 if (PageMovable(page))
188 putback_movable_page(page);
189 else
190 __ClearPageIsolated(page);
191 unlock_page(page);
192 put_page(page);
193 } else {
194 mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
195 page_is_file_cache(page), -hpage_nr_pages(page));
196 putback_lru_page(page);
197 }
198 }
199}
200
201/*
202 * Restore a potential migration pte to a working pte entry
203 */
204static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma,
205 unsigned long addr, void *old)
206{
207 struct page_vma_mapped_walk pvmw = {
208 .page = old,
209 .vma = vma,
210 .address = addr,
211 .flags = PVMW_SYNC | PVMW_MIGRATION,
212 };
213 struct page *new;
214 pte_t pte;
215 swp_entry_t entry;
216
217 VM_BUG_ON_PAGE(PageTail(page), page);
218 while (page_vma_mapped_walk(&pvmw)) {
219 if (PageKsm(page))
220 new = page;
221 else
222 new = page - pvmw.page->index +
223 linear_page_index(vma, pvmw.address);
224
225#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
226 /* PMD-mapped THP migration entry */
227 if (!pvmw.pte) {
228 VM_BUG_ON_PAGE(PageHuge(page) || !PageTransCompound(page), page);
229 remove_migration_pmd(&pvmw, new);
230 continue;
231 }
232#endif
233
234 get_page(new);
235 pte = pte_mkold(mk_pte(new, READ_ONCE(vma->vm_page_prot)));
236 if (pte_swp_soft_dirty(*pvmw.pte))
237 pte = pte_mksoft_dirty(pte);
238
239 /*
240 * Recheck VMA as permissions can change since migration started
241 */
242 entry = pte_to_swp_entry(*pvmw.pte);
243 if (is_write_migration_entry(entry))
244 pte = maybe_mkwrite(pte, vma);
245
246 if (unlikely(is_zone_device_page(new))) {
247 if (is_device_private_page(new)) {
248 entry = make_device_private_entry(new, pte_write(pte));
249 pte = swp_entry_to_pte(entry);
250 }
251 }
252
253#ifdef CONFIG_HUGETLB_PAGE
254 if (PageHuge(new)) {
255 pte = pte_mkhuge(pte);
256 pte = arch_make_huge_pte(pte, vma, new, 0);
257 set_huge_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
258 if (PageAnon(new))
259 hugepage_add_anon_rmap(new, vma, pvmw.address);
260 else
261 page_dup_rmap(new, true);
262 } else
263#endif
264 {
265 set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
266
267 if (PageAnon(new))
268 page_add_anon_rmap(new, vma, pvmw.address, false);
269 else
270 page_add_file_rmap(new, false);
271 }
272 if (vma->vm_flags & VM_LOCKED && !PageTransCompound(new))
273 mlock_vma_page(new);
274
275 if (PageTransHuge(page) && PageMlocked(page))
276 clear_page_mlock(page);
277
278 /* No need to invalidate - it was non-present before */
279 update_mmu_cache(vma, pvmw.address, pvmw.pte);
280 }
281
282 return true;
283}
284
285/*
286 * Get rid of all migration entries and replace them by
287 * references to the indicated page.
288 */
289void remove_migration_ptes(struct page *old, struct page *new, bool locked)
290{
291 struct rmap_walk_control rwc = {
292 .rmap_one = remove_migration_pte,
293 .arg = old,
294 };
295
296 if (locked)
297 rmap_walk_locked(new, &rwc);
298 else
299 rmap_walk(new, &rwc);
300}
301
302/*
303 * Something used the pte of a page under migration. We need to
304 * get to the page and wait until migration is finished.
305 * When we return from this function the fault will be retried.
306 */
307void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
308 spinlock_t *ptl)
309{
310 pte_t pte;
311 swp_entry_t entry;
312 struct page *page;
313
314 spin_lock(ptl);
315 pte = *ptep;
316 if (!is_swap_pte(pte))
317 goto out;
318
319 entry = pte_to_swp_entry(pte);
320 if (!is_migration_entry(entry))
321 goto out;
322
323 page = migration_entry_to_page(entry);
324
325 /*
326 * Once page cache replacement of page migration started, page_count
327 * is zero; but we must not call put_and_wait_on_page_locked() without
328 * a ref. Use get_page_unless_zero(), and just fault again if it fails.
329 */
330 if (!get_page_unless_zero(page))
331 goto out;
332 pte_unmap_unlock(ptep, ptl);
333 put_and_wait_on_page_locked(page);
334 return;
335out:
336 pte_unmap_unlock(ptep, ptl);
337}
338
339void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
340 unsigned long address)
341{
342 spinlock_t *ptl = pte_lockptr(mm, pmd);
343 pte_t *ptep = pte_offset_map(pmd, address);
344 __migration_entry_wait(mm, ptep, ptl);
345}
346
347void migration_entry_wait_huge(struct vm_area_struct *vma,
348 struct mm_struct *mm, pte_t *pte)
349{
350 spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), mm, pte);
351 __migration_entry_wait(mm, pte, ptl);
352}
353
354#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
355void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)
356{
357 spinlock_t *ptl;
358 struct page *page;
359
360 ptl = pmd_lock(mm, pmd);
361 if (!is_pmd_migration_entry(*pmd))
362 goto unlock;
363 page = migration_entry_to_page(pmd_to_swp_entry(*pmd));
364 if (!get_page_unless_zero(page))
365 goto unlock;
366 spin_unlock(ptl);
367 put_and_wait_on_page_locked(page);
368 return;
369unlock:
370 spin_unlock(ptl);
371}
372#endif
373
374static int expected_page_refs(struct address_space *mapping, struct page *page)
375{
376 int expected_count = 1;
377
378 /*
379 * Device public or private pages have an extra refcount as they are
380 * ZONE_DEVICE pages.
381 */
382 expected_count += is_device_private_page(page);
383 if (mapping)
384 expected_count += hpage_nr_pages(page) + page_has_private(page);
385
386 return expected_count;
387}
388
389/*
390 * Replace the page in the mapping.
391 *
392 * The number of remaining references must be:
393 * 1 for anonymous pages without a mapping
394 * 2 for pages with a mapping
395 * 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
396 */
397int migrate_page_move_mapping(struct address_space *mapping,
398 struct page *newpage, struct page *page, int extra_count)
399{
400 XA_STATE(xas, &mapping->i_pages, page_index(page));
401 struct zone *oldzone, *newzone;
402 int dirty;
403 int expected_count = expected_page_refs(mapping, page) + extra_count;
404
405 if (!mapping) {
406 /* Anonymous page without mapping */
407 if (page_count(page) != expected_count)
408 return -EAGAIN;
409
410 /* No turning back from here */
411 newpage->index = page->index;
412 newpage->mapping = page->mapping;
413 if (PageSwapBacked(page))
414 __SetPageSwapBacked(newpage);
415
416 return MIGRATEPAGE_SUCCESS;
417 }
418
419 oldzone = page_zone(page);
420 newzone = page_zone(newpage);
421
422 xas_lock_irq(&xas);
423 if (page_count(page) != expected_count || xas_load(&xas) != page) {
424 xas_unlock_irq(&xas);
425 return -EAGAIN;
426 }
427
428 if (!page_ref_freeze(page, expected_count)) {
429 xas_unlock_irq(&xas);
430 return -EAGAIN;
431 }
432
433 /*
434 * Now we know that no one else is looking at the page:
435 * no turning back from here.
436 */
437 newpage->index = page->index;
438 newpage->mapping = page->mapping;
439 page_ref_add(newpage, hpage_nr_pages(page)); /* add cache reference */
440 if (PageSwapBacked(page)) {
441 __SetPageSwapBacked(newpage);
442 if (PageSwapCache(page)) {
443 SetPageSwapCache(newpage);
444 set_page_private(newpage, page_private(page));
445 }
446 } else {
447 VM_BUG_ON_PAGE(PageSwapCache(page), page);
448 }
449
450 /* Move dirty while page refs frozen and newpage not yet exposed */
451 dirty = PageDirty(page);
452 if (dirty) {
453 ClearPageDirty(page);
454 SetPageDirty(newpage);
455 }
456
457 xas_store(&xas, newpage);
458 if (PageTransHuge(page)) {
459 int i;
460
461 for (i = 1; i < HPAGE_PMD_NR; i++) {
462 xas_next(&xas);
463 xas_store(&xas, newpage);
464 }
465 }
466
467 /*
468 * Drop cache reference from old page by unfreezing
469 * to one less reference.
470 * We know this isn't the last reference.
471 */
472 page_ref_unfreeze(page, expected_count - hpage_nr_pages(page));
473
474 xas_unlock(&xas);
475 /* Leave irq disabled to prevent preemption while updating stats */
476
477 /*
478 * If moved to a different zone then also account
479 * the page for that zone. Other VM counters will be
480 * taken care of when we establish references to the
481 * new page and drop references to the old page.
482 *
483 * Note that anonymous pages are accounted for
484 * via NR_FILE_PAGES and NR_ANON_MAPPED if they
485 * are mapped to swap space.
486 */
487 if (newzone != oldzone) {
488 __dec_node_state(oldzone->zone_pgdat, NR_FILE_PAGES);
489 __inc_node_state(newzone->zone_pgdat, NR_FILE_PAGES);
490 if (PageSwapBacked(page) && !PageSwapCache(page)) {
491 __dec_node_state(oldzone->zone_pgdat, NR_SHMEM);
492 __inc_node_state(newzone->zone_pgdat, NR_SHMEM);
493 }
494 if (dirty && mapping_cap_account_dirty(mapping)) {
495 __dec_node_state(oldzone->zone_pgdat, NR_FILE_DIRTY);
496 __dec_zone_state(oldzone, NR_ZONE_WRITE_PENDING);
497 __inc_node_state(newzone->zone_pgdat, NR_FILE_DIRTY);
498 __inc_zone_state(newzone, NR_ZONE_WRITE_PENDING);
499 }
500 }
501 local_irq_enable();
502
503 return MIGRATEPAGE_SUCCESS;
504}
505EXPORT_SYMBOL(migrate_page_move_mapping);
506
507/*
508 * The expected number of remaining references is the same as that
509 * of migrate_page_move_mapping().
510 */
511int migrate_huge_page_move_mapping(struct address_space *mapping,
512 struct page *newpage, struct page *page)
513{
514 XA_STATE(xas, &mapping->i_pages, page_index(page));
515 int expected_count;
516
517 xas_lock_irq(&xas);
518 expected_count = 2 + page_has_private(page);
519 if (page_count(page) != expected_count || xas_load(&xas) != page) {
520 xas_unlock_irq(&xas);
521 return -EAGAIN;
522 }
523
524 if (!page_ref_freeze(page, expected_count)) {
525 xas_unlock_irq(&xas);
526 return -EAGAIN;
527 }
528
529 newpage->index = page->index;
530 newpage->mapping = page->mapping;
531
532 get_page(newpage);
533
534 xas_store(&xas, newpage);
535
536 page_ref_unfreeze(page, expected_count - 1);
537
538 xas_unlock_irq(&xas);
539
540 return MIGRATEPAGE_SUCCESS;
541}
542
543/*
544 * Gigantic pages are so large that we do not guarantee that page++ pointer
545 * arithmetic will work across the entire page. We need something more
546 * specialized.
547 */
548static void __copy_gigantic_page(struct page *dst, struct page *src,
549 int nr_pages)
550{
551 int i;
552 struct page *dst_base = dst;
553 struct page *src_base = src;
554
555 for (i = 0; i < nr_pages; ) {
556 cond_resched();
557 copy_highpage(dst, src);
558
559 i++;
560 dst = mem_map_next(dst, dst_base, i);
561 src = mem_map_next(src, src_base, i);
562 }
563}
564
565static void copy_huge_page(struct page *dst, struct page *src)
566{
567 int i;
568 int nr_pages;
569
570 if (PageHuge(src)) {
571 /* hugetlbfs page */
572 struct hstate *h = page_hstate(src);
573 nr_pages = pages_per_huge_page(h);
574
575 if (unlikely(nr_pages > MAX_ORDER_NR_PAGES)) {
576 __copy_gigantic_page(dst, src, nr_pages);
577 return;
578 }
579 } else {
580 /* thp page */
581 BUG_ON(!PageTransHuge(src));
582 nr_pages = hpage_nr_pages(src);
583 }
584
585 for (i = 0; i < nr_pages; i++) {
586 cond_resched();
587 copy_highpage(dst + i, src + i);
588 }
589}
590
591/*
592 * Copy the page to its new location
593 */
594void migrate_page_states(struct page *newpage, struct page *page)
595{
596 int cpupid;
597
598 if (PageError(page))
599 SetPageError(newpage);
600 if (PageReferenced(page))
601 SetPageReferenced(newpage);
602 if (PageUptodate(page))
603 SetPageUptodate(newpage);
604 if (TestClearPageActive(page)) {
605 VM_BUG_ON_PAGE(PageUnevictable(page), page);
606 SetPageActive(newpage);
607 } else if (TestClearPageUnevictable(page))
608 SetPageUnevictable(newpage);
609 if (PageWorkingset(page))
610 SetPageWorkingset(newpage);
611 if (PageChecked(page))
612 SetPageChecked(newpage);
613 if (PageMappedToDisk(page))
614 SetPageMappedToDisk(newpage);
615
616 /* Move dirty on pages not done by migrate_page_move_mapping() */
617 if (PageDirty(page))
618 SetPageDirty(newpage);
619
620 if (page_is_young(page))
621 set_page_young(newpage);
622 if (page_is_idle(page))
623 set_page_idle(newpage);
624
625 /*
626 * Copy NUMA information to the new page, to prevent over-eager
627 * future migrations of this same page.
628 */
629 cpupid = page_cpupid_xchg_last(page, -1);
630 page_cpupid_xchg_last(newpage, cpupid);
631
632 ksm_migrate_page(newpage, page);
633 /*
634 * Please do not reorder this without considering how mm/ksm.c's
635 * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
636 */
637 if (PageSwapCache(page))
638 ClearPageSwapCache(page);
639 ClearPagePrivate(page);
640 set_page_private(page, 0);
641
642 /*
643 * If any waiters have accumulated on the new page then
644 * wake them up.
645 */
646 if (PageWriteback(newpage))
647 end_page_writeback(newpage);
648
649 copy_page_owner(page, newpage);
650
651 mem_cgroup_migrate(page, newpage);
652}
653EXPORT_SYMBOL(migrate_page_states);
654
655void migrate_page_copy(struct page *newpage, struct page *page)
656{
657 if (PageHuge(page) || PageTransHuge(page))
658 copy_huge_page(newpage, page);
659 else
660 copy_highpage(newpage, page);
661
662 migrate_page_states(newpage, page);
663}
664EXPORT_SYMBOL(migrate_page_copy);
665
666/************************************************************
667 * Migration functions
668 ***********************************************************/
669
670/*
671 * Common logic to directly migrate a single LRU page suitable for
672 * pages that do not use PagePrivate/PagePrivate2.
673 *
674 * Pages are locked upon entry and exit.
675 */
676int migrate_page(struct address_space *mapping,
677 struct page *newpage, struct page *page,
678 enum migrate_mode mode)
679{
680 int rc;
681
682 BUG_ON(PageWriteback(page)); /* Writeback must be complete */
683
684 rc = migrate_page_move_mapping(mapping, newpage, page, 0);
685
686 if (rc != MIGRATEPAGE_SUCCESS)
687 return rc;
688
689 if (mode != MIGRATE_SYNC_NO_COPY)
690 migrate_page_copy(newpage, page);
691 else
692 migrate_page_states(newpage, page);
693 return MIGRATEPAGE_SUCCESS;
694}
695EXPORT_SYMBOL(migrate_page);
696
697#ifdef CONFIG_BLOCK
698/* Returns true if all buffers are successfully locked */
699static bool buffer_migrate_lock_buffers(struct buffer_head *head,
700 enum migrate_mode mode)
701{
702 struct buffer_head *bh = head;
703
704 /* Simple case, sync compaction */
705 if (mode != MIGRATE_ASYNC) {
706 do {
707 lock_buffer(bh);
708 bh = bh->b_this_page;
709
710 } while (bh != head);
711
712 return true;
713 }
714
715 /* async case, we cannot block on lock_buffer so use trylock_buffer */
716 do {
717 if (!trylock_buffer(bh)) {
718 /*
719 * We failed to lock the buffer and cannot stall in
720 * async migration. Release the taken locks
721 */
722 struct buffer_head *failed_bh = bh;
723 bh = head;
724 while (bh != failed_bh) {
725 unlock_buffer(bh);
726 bh = bh->b_this_page;
727 }
728 return false;
729 }
730
731 bh = bh->b_this_page;
732 } while (bh != head);
733 return true;
734}
735
736static int __buffer_migrate_page(struct address_space *mapping,
737 struct page *newpage, struct page *page, enum migrate_mode mode,
738 bool check_refs)
739{
740 struct buffer_head *bh, *head;
741 int rc;
742 int expected_count;
743
744 if (!page_has_buffers(page))
745 return migrate_page(mapping, newpage, page, mode);
746
747 /* Check whether page does not have extra refs before we do more work */
748 expected_count = expected_page_refs(mapping, page);
749 if (page_count(page) != expected_count)
750 return -EAGAIN;
751
752 head = page_buffers(page);
753 if (!buffer_migrate_lock_buffers(head, mode))
754 return -EAGAIN;
755
756 if (check_refs) {
757 bool busy;
758 bool invalidated = false;
759
760recheck_buffers:
761 busy = false;
762 spin_lock(&mapping->private_lock);
763 bh = head;
764 do {
765 if (atomic_read(&bh->b_count)) {
766 busy = true;
767 break;
768 }
769 bh = bh->b_this_page;
770 } while (bh != head);
771 if (busy) {
772 if (invalidated) {
773 rc = -EAGAIN;
774 goto unlock_buffers;
775 }
776 spin_unlock(&mapping->private_lock);
777 invalidate_bh_lrus();
778 invalidated = true;
779 goto recheck_buffers;
780 }
781 }
782
783 rc = migrate_page_move_mapping(mapping, newpage, page, 0);
784 if (rc != MIGRATEPAGE_SUCCESS)
785 goto unlock_buffers;
786
787 ClearPagePrivate(page);
788 set_page_private(newpage, page_private(page));
789 set_page_private(page, 0);
790 put_page(page);
791 get_page(newpage);
792
793 bh = head;
794 do {
795 set_bh_page(bh, newpage, bh_offset(bh));
796 bh = bh->b_this_page;
797
798 } while (bh != head);
799
800 SetPagePrivate(newpage);
801
802 if (mode != MIGRATE_SYNC_NO_COPY)
803 migrate_page_copy(newpage, page);
804 else
805 migrate_page_states(newpage, page);
806
807 rc = MIGRATEPAGE_SUCCESS;
808unlock_buffers:
809 if (check_refs)
810 spin_unlock(&mapping->private_lock);
811 bh = head;
812 do {
813 unlock_buffer(bh);
814 bh = bh->b_this_page;
815
816 } while (bh != head);
817
818 return rc;
819}
820
821/*
822 * Migration function for pages with buffers. This function can only be used
823 * if the underlying filesystem guarantees that no other references to "page"
824 * exist. For example attached buffer heads are accessed only under page lock.
825 */
826int buffer_migrate_page(struct address_space *mapping,
827 struct page *newpage, struct page *page, enum migrate_mode mode)
828{
829 return __buffer_migrate_page(mapping, newpage, page, mode, false);
830}
831EXPORT_SYMBOL(buffer_migrate_page);
832
833/*
834 * Same as above except that this variant is more careful and checks that there
835 * are also no buffer head references. This function is the right one for
836 * mappings where buffer heads are directly looked up and referenced (such as
837 * block device mappings).
838 */
839int buffer_migrate_page_norefs(struct address_space *mapping,
840 struct page *newpage, struct page *page, enum migrate_mode mode)
841{
842 return __buffer_migrate_page(mapping, newpage, page, mode, true);
843}
844#endif
845
846/*
847 * Writeback a page to clean the dirty state
848 */
849static int writeout(struct address_space *mapping, struct page *page)
850{
851 struct writeback_control wbc = {
852 .sync_mode = WB_SYNC_NONE,
853 .nr_to_write = 1,
854 .range_start = 0,
855 .range_end = LLONG_MAX,
856 .for_reclaim = 1
857 };
858 int rc;
859
860 if (!mapping->a_ops->writepage)
861 /* No write method for the address space */
862 return -EINVAL;
863
864 if (!clear_page_dirty_for_io(page))
865 /* Someone else already triggered a write */
866 return -EAGAIN;
867
868 /*
869 * A dirty page may imply that the underlying filesystem has
870 * the page on some queue. So the page must be clean for
871 * migration. Writeout may mean we loose the lock and the
872 * page state is no longer what we checked for earlier.
873 * At this point we know that the migration attempt cannot
874 * be successful.
875 */
876 remove_migration_ptes(page, page, false);
877
878 rc = mapping->a_ops->writepage(page, &wbc);
879
880 if (rc != AOP_WRITEPAGE_ACTIVATE)
881 /* unlocked. Relock */
882 lock_page(page);
883
884 return (rc < 0) ? -EIO : -EAGAIN;
885}
886
887/*
888 * Default handling if a filesystem does not provide a migration function.
889 */
890static int fallback_migrate_page(struct address_space *mapping,
891 struct page *newpage, struct page *page, enum migrate_mode mode)
892{
893 if (PageDirty(page)) {
894 /* Only writeback pages in full synchronous migration */
895 switch (mode) {
896 case MIGRATE_SYNC:
897 case MIGRATE_SYNC_NO_COPY:
898 break;
899 default:
900 return -EBUSY;
901 }
902 return writeout(mapping, page);
903 }
904
905 /*
906 * Buffers may be managed in a filesystem specific way.
907 * We must have no buffers or drop them.
908 */
909 if (page_has_private(page) &&
910 !try_to_release_page(page, GFP_KERNEL))
911 return mode == MIGRATE_SYNC ? -EAGAIN : -EBUSY;
912
913 return migrate_page(mapping, newpage, page, mode);
914}
915
916/*
917 * Move a page to a newly allocated page
918 * The page is locked and all ptes have been successfully removed.
919 *
920 * The new page will have replaced the old page if this function
921 * is successful.
922 *
923 * Return value:
924 * < 0 - error code
925 * MIGRATEPAGE_SUCCESS - success
926 */
927static int move_to_new_page(struct page *newpage, struct page *page,
928 enum migrate_mode mode)
929{
930 struct address_space *mapping;
931 int rc = -EAGAIN;
932 bool is_lru = !__PageMovable(page);
933
934 VM_BUG_ON_PAGE(!PageLocked(page), page);
935 VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
936
937 mapping = page_mapping(page);
938
939 if (likely(is_lru)) {
940 if (!mapping)
941 rc = migrate_page(mapping, newpage, page, mode);
942 else if (mapping->a_ops->migratepage)
943 /*
944 * Most pages have a mapping and most filesystems
945 * provide a migratepage callback. Anonymous pages
946 * are part of swap space which also has its own
947 * migratepage callback. This is the most common path
948 * for page migration.
949 */
950 rc = mapping->a_ops->migratepage(mapping, newpage,
951 page, mode);
952 else
953 rc = fallback_migrate_page(mapping, newpage,
954 page, mode);
955 } else {
956 /*
957 * In case of non-lru page, it could be released after
958 * isolation step. In that case, we shouldn't try migration.
959 */
960 VM_BUG_ON_PAGE(!PageIsolated(page), page);
961 if (!PageMovable(page)) {
962 rc = MIGRATEPAGE_SUCCESS;
963 __ClearPageIsolated(page);
964 goto out;
965 }
966
967 rc = mapping->a_ops->migratepage(mapping, newpage,
968 page, mode);
969 WARN_ON_ONCE(rc == MIGRATEPAGE_SUCCESS &&
970 !PageIsolated(page));
971 }
972
973 /*
974 * When successful, old pagecache page->mapping must be cleared before
975 * page is freed; but stats require that PageAnon be left as PageAnon.
976 */
977 if (rc == MIGRATEPAGE_SUCCESS) {
978 if (__PageMovable(page)) {
979 VM_BUG_ON_PAGE(!PageIsolated(page), page);
980
981 /*
982 * We clear PG_movable under page_lock so any compactor
983 * cannot try to migrate this page.
984 */
985 __ClearPageIsolated(page);
986 }
987
988 /*
989 * Anonymous and movable page->mapping will be cleard by
990 * free_pages_prepare so don't reset it here for keeping
991 * the type to work PageAnon, for example.
992 */
993 if (!PageMappingFlags(page))
994 page->mapping = NULL;
995
996 if (likely(!is_zone_device_page(newpage)))
997 flush_dcache_page(newpage);
998
999 }
1000out:
1001 return rc;
1002}
1003
1004static int __unmap_and_move(struct page *page, struct page *newpage,
1005 int force, enum migrate_mode mode)
1006{
1007 int rc = -EAGAIN;
1008 int page_was_mapped = 0;
1009 struct anon_vma *anon_vma = NULL;
1010 bool is_lru = !__PageMovable(page);
1011
1012 if (!trylock_page(page)) {
1013 if (!force || mode == MIGRATE_ASYNC)
1014 goto out;
1015
1016 /*
1017 * It's not safe for direct compaction to call lock_page.
1018 * For example, during page readahead pages are added locked
1019 * to the LRU. Later, when the IO completes the pages are
1020 * marked uptodate and unlocked. However, the queueing
1021 * could be merging multiple pages for one bio (e.g.
1022 * mpage_readpages). If an allocation happens for the
1023 * second or third page, the process can end up locking
1024 * the same page twice and deadlocking. Rather than
1025 * trying to be clever about what pages can be locked,
1026 * avoid the use of lock_page for direct compaction
1027 * altogether.
1028 */
1029 if (current->flags & PF_MEMALLOC)
1030 goto out;
1031
1032 lock_page(page);
1033 }
1034
1035 if (PageWriteback(page)) {
1036 /*
1037 * Only in the case of a full synchronous migration is it
1038 * necessary to wait for PageWriteback. In the async case,
1039 * the retry loop is too short and in the sync-light case,
1040 * the overhead of stalling is too much
1041 */
1042 switch (mode) {
1043 case MIGRATE_SYNC:
1044 case MIGRATE_SYNC_NO_COPY:
1045 break;
1046 default:
1047 rc = -EBUSY;
1048 goto out_unlock;
1049 }
1050 if (!force)
1051 goto out_unlock;
1052 wait_on_page_writeback(page);
1053 }
1054
1055 /*
1056 * By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
1057 * we cannot notice that anon_vma is freed while we migrates a page.
1058 * This get_anon_vma() delays freeing anon_vma pointer until the end
1059 * of migration. File cache pages are no problem because of page_lock()
1060 * File Caches may use write_page() or lock_page() in migration, then,
1061 * just care Anon page here.
1062 *
1063 * Only page_get_anon_vma() understands the subtleties of
1064 * getting a hold on an anon_vma from outside one of its mms.
1065 * But if we cannot get anon_vma, then we won't need it anyway,
1066 * because that implies that the anon page is no longer mapped
1067 * (and cannot be remapped so long as we hold the page lock).
1068 */
1069 if (PageAnon(page) && !PageKsm(page))
1070 anon_vma = page_get_anon_vma(page);
1071
1072 /*
1073 * Block others from accessing the new page when we get around to
1074 * establishing additional references. We are usually the only one
1075 * holding a reference to newpage at this point. We used to have a BUG
1076 * here if trylock_page(newpage) fails, but would like to allow for
1077 * cases where there might be a race with the previous use of newpage.
1078 * This is much like races on refcount of oldpage: just don't BUG().
1079 */
1080 if (unlikely(!trylock_page(newpage)))
1081 goto out_unlock;
1082
1083 if (unlikely(!is_lru)) {
1084 rc = move_to_new_page(newpage, page, mode);
1085 goto out_unlock_both;
1086 }
1087
1088 /*
1089 * Corner case handling:
1090 * 1. When a new swap-cache page is read into, it is added to the LRU
1091 * and treated as swapcache but it has no rmap yet.
1092 * Calling try_to_unmap() against a page->mapping==NULL page will
1093 * trigger a BUG. So handle it here.
1094 * 2. An orphaned page (see truncate_complete_page) might have
1095 * fs-private metadata. The page can be picked up due to memory
1096 * offlining. Everywhere else except page reclaim, the page is
1097 * invisible to the vm, so the page can not be migrated. So try to
1098 * free the metadata, so the page can be freed.
1099 */
1100 if (!page->mapping) {
1101 VM_BUG_ON_PAGE(PageAnon(page), page);
1102 if (page_has_private(page)) {
1103 try_to_free_buffers(page);
1104 goto out_unlock_both;
1105 }
1106 } else if (page_mapped(page)) {
1107 /* Establish migration ptes */
1108 VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma,
1109 page);
1110 try_to_unmap(page,
1111 TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
1112 page_was_mapped = 1;
1113 }
1114
1115 if (!page_mapped(page))
1116 rc = move_to_new_page(newpage, page, mode);
1117
1118 if (page_was_mapped)
1119 remove_migration_ptes(page,
1120 rc == MIGRATEPAGE_SUCCESS ? newpage : page, false);
1121
1122out_unlock_both:
1123 unlock_page(newpage);
1124out_unlock:
1125 /* Drop an anon_vma reference if we took one */
1126 if (anon_vma)
1127 put_anon_vma(anon_vma);
1128 unlock_page(page);
1129out:
1130 /*
1131 * If migration is successful, decrease refcount of the newpage
1132 * which will not free the page because new page owner increased
1133 * refcounter. As well, if it is LRU page, add the page to LRU
1134 * list in here. Use the old state of the isolated source page to
1135 * determine if we migrated a LRU page. newpage was already unlocked
1136 * and possibly modified by its owner - don't rely on the page
1137 * state.
1138 */
1139 if (rc == MIGRATEPAGE_SUCCESS) {
1140 if (unlikely(!is_lru))
1141 put_page(newpage);
1142 else
1143 putback_lru_page(newpage);
1144 }
1145
1146 return rc;
1147}
1148
1149/*
1150 * gcc 4.7 and 4.8 on arm get an ICEs when inlining unmap_and_move(). Work
1151 * around it.
1152 */
1153#if defined(CONFIG_ARM) && \
1154 defined(GCC_VERSION) && GCC_VERSION < 40900 && GCC_VERSION >= 40700
1155#define ICE_noinline noinline
1156#else
1157#define ICE_noinline
1158#endif
1159
1160/*
1161 * Obtain the lock on page, remove all ptes and migrate the page
1162 * to the newly allocated page in newpage.
1163 */
1164static ICE_noinline int unmap_and_move(new_page_t get_new_page,
1165 free_page_t put_new_page,
1166 unsigned long private, struct page *page,
1167 int force, enum migrate_mode mode,
1168 enum migrate_reason reason)
1169{
1170 int rc = MIGRATEPAGE_SUCCESS;
1171 struct page *newpage;
1172
1173 if (!thp_migration_supported() && PageTransHuge(page))
1174 return -ENOMEM;
1175
1176 newpage = get_new_page(page, private);
1177 if (!newpage)
1178 return -ENOMEM;
1179
1180 if (page_count(page) == 1) {
1181 /* page was freed from under us. So we are done. */
1182 ClearPageActive(page);
1183 ClearPageUnevictable(page);
1184 if (unlikely(__PageMovable(page))) {
1185 lock_page(page);
1186 if (!PageMovable(page))
1187 __ClearPageIsolated(page);
1188 unlock_page(page);
1189 }
1190 if (put_new_page)
1191 put_new_page(newpage, private);
1192 else
1193 put_page(newpage);
1194 goto out;
1195 }
1196
1197 rc = __unmap_and_move(page, newpage, force, mode);
1198 if (rc == MIGRATEPAGE_SUCCESS)
1199 set_page_owner_migrate_reason(newpage, reason);
1200
1201out:
1202 if (rc != -EAGAIN) {
1203 /*
1204 * A page that has been migrated has all references
1205 * removed and will be freed. A page that has not been
1206 * migrated will have kepts its references and be
1207 * restored.
1208 */
1209 list_del(&page->lru);
1210
1211 /*
1212 * Compaction can migrate also non-LRU pages which are
1213 * not accounted to NR_ISOLATED_*. They can be recognized
1214 * as __PageMovable
1215 */
1216 if (likely(!__PageMovable(page)))
1217 mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
1218 page_is_file_cache(page), -hpage_nr_pages(page));
1219 }
1220
1221 /*
1222 * If migration is successful, releases reference grabbed during
1223 * isolation. Otherwise, restore the page to right list unless
1224 * we want to retry.
1225 */
1226 if (rc == MIGRATEPAGE_SUCCESS) {
1227 put_page(page);
1228 if (reason == MR_MEMORY_FAILURE) {
1229 /*
1230 * Set PG_HWPoison on just freed page
1231 * intentionally. Although it's rather weird,
1232 * it's how HWPoison flag works at the moment.
1233 */
1234 if (set_hwpoison_free_buddy_page(page))
1235 num_poisoned_pages_inc();
1236 }
1237 } else {
1238 if (rc != -EAGAIN) {
1239 if (likely(!__PageMovable(page))) {
1240 putback_lru_page(page);
1241 goto put_new;
1242 }
1243
1244 lock_page(page);
1245 if (PageMovable(page))
1246 putback_movable_page(page);
1247 else
1248 __ClearPageIsolated(page);
1249 unlock_page(page);
1250 put_page(page);
1251 }
1252put_new:
1253 if (put_new_page)
1254 put_new_page(newpage, private);
1255 else
1256 put_page(newpage);
1257 }
1258
1259 return rc;
1260}
1261
1262/*
1263 * Counterpart of unmap_and_move_page() for hugepage migration.
1264 *
1265 * This function doesn't wait the completion of hugepage I/O
1266 * because there is no race between I/O and migration for hugepage.
1267 * Note that currently hugepage I/O occurs only in direct I/O
1268 * where no lock is held and PG_writeback is irrelevant,
1269 * and writeback status of all subpages are counted in the reference
1270 * count of the head page (i.e. if all subpages of a 2MB hugepage are
1271 * under direct I/O, the reference of the head page is 512 and a bit more.)
1272 * This means that when we try to migrate hugepage whose subpages are
1273 * doing direct I/O, some references remain after try_to_unmap() and
1274 * hugepage migration fails without data corruption.
1275 *
1276 * There is also no race when direct I/O is issued on the page under migration,
1277 * because then pte is replaced with migration swap entry and direct I/O code
1278 * will wait in the page fault for migration to complete.
1279 */
1280static int unmap_and_move_huge_page(new_page_t get_new_page,
1281 free_page_t put_new_page, unsigned long private,
1282 struct page *hpage, int force,
1283 enum migrate_mode mode, int reason)
1284{
1285 int rc = -EAGAIN;
1286 int page_was_mapped = 0;
1287 struct page *new_hpage;
1288 struct anon_vma *anon_vma = NULL;
1289
1290 /*
1291 * Migratability of hugepages depends on architectures and their size.
1292 * This check is necessary because some callers of hugepage migration
1293 * like soft offline and memory hotremove don't walk through page
1294 * tables or check whether the hugepage is pmd-based or not before
1295 * kicking migration.
1296 */
1297 if (!hugepage_migration_supported(page_hstate(hpage))) {
1298 putback_active_hugepage(hpage);
1299 return -ENOSYS;
1300 }
1301
1302 new_hpage = get_new_page(hpage, private);
1303 if (!new_hpage)
1304 return -ENOMEM;
1305
1306 if (!trylock_page(hpage)) {
1307 if (!force)
1308 goto out;
1309 switch (mode) {
1310 case MIGRATE_SYNC:
1311 case MIGRATE_SYNC_NO_COPY:
1312 break;
1313 default:
1314 goto out;
1315 }
1316 lock_page(hpage);
1317 }
1318
1319 /*
1320 * Check for pages which are in the process of being freed. Without
1321 * page_mapping() set, hugetlbfs specific move page routine will not
1322 * be called and we could leak usage counts for subpools.
1323 */
1324 if (page_private(hpage) && !page_mapping(hpage)) {
1325 rc = -EBUSY;
1326 goto out_unlock;
1327 }
1328
1329 if (PageAnon(hpage))
1330 anon_vma = page_get_anon_vma(hpage);
1331
1332 if (unlikely(!trylock_page(new_hpage)))
1333 goto put_anon;
1334
1335 if (page_mapped(hpage)) {
1336 try_to_unmap(hpage,
1337 TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
1338 page_was_mapped = 1;
1339 }
1340
1341 if (!page_mapped(hpage))
1342 rc = move_to_new_page(new_hpage, hpage, mode);
1343
1344 if (page_was_mapped)
1345 remove_migration_ptes(hpage,
1346 rc == MIGRATEPAGE_SUCCESS ? new_hpage : hpage, false);
1347
1348 unlock_page(new_hpage);
1349
1350put_anon:
1351 if (anon_vma)
1352 put_anon_vma(anon_vma);
1353
1354 if (rc == MIGRATEPAGE_SUCCESS) {
1355 move_hugetlb_state(hpage, new_hpage, reason);
1356 put_new_page = NULL;
1357 }
1358
1359out_unlock:
1360 unlock_page(hpage);
1361out:
1362 if (rc != -EAGAIN)
1363 putback_active_hugepage(hpage);
1364
1365 /*
1366 * If migration was not successful and there's a freeing callback, use
1367 * it. Otherwise, put_page() will drop the reference grabbed during
1368 * isolation.
1369 */
1370 if (put_new_page)
1371 put_new_page(new_hpage, private);
1372 else
1373 putback_active_hugepage(new_hpage);
1374
1375 return rc;
1376}
1377
1378/*
1379 * migrate_pages - migrate the pages specified in a list, to the free pages
1380 * supplied as the target for the page migration
1381 *
1382 * @from: The list of pages to be migrated.
1383 * @get_new_page: The function used to allocate free pages to be used
1384 * as the target of the page migration.
1385 * @put_new_page: The function used to free target pages if migration
1386 * fails, or NULL if no special handling is necessary.
1387 * @private: Private data to be passed on to get_new_page()
1388 * @mode: The migration mode that specifies the constraints for
1389 * page migration, if any.
1390 * @reason: The reason for page migration.
1391 *
1392 * The function returns after 10 attempts or if no pages are movable any more
1393 * because the list has become empty or no retryable pages exist any more.
1394 * The caller should call putback_movable_pages() to return pages to the LRU
1395 * or free list only if ret != 0.
1396 *
1397 * Returns the number of pages that were not migrated, or an error code.
1398 */
1399int migrate_pages(struct list_head *from, new_page_t get_new_page,
1400 free_page_t put_new_page, unsigned long private,
1401 enum migrate_mode mode, int reason)
1402{
1403 int retry = 1;
1404 int nr_failed = 0;
1405 int nr_succeeded = 0;
1406 int pass = 0;
1407 struct page *page;
1408 struct page *page2;
1409 int swapwrite = current->flags & PF_SWAPWRITE;
1410 int rc;
1411
1412 if (!swapwrite)
1413 current->flags |= PF_SWAPWRITE;
1414
1415 for(pass = 0; pass < 10 && retry; pass++) {
1416 retry = 0;
1417
1418 list_for_each_entry_safe(page, page2, from, lru) {
1419retry:
1420 cond_resched();
1421
1422 if (PageHuge(page))
1423 rc = unmap_and_move_huge_page(get_new_page,
1424 put_new_page, private, page,
1425 pass > 2, mode, reason);
1426 else
1427 rc = unmap_and_move(get_new_page, put_new_page,
1428 private, page, pass > 2, mode,
1429 reason);
1430
1431 switch(rc) {
1432 case -ENOMEM:
1433 /*
1434 * THP migration might be unsupported or the
1435 * allocation could've failed so we should
1436 * retry on the same page with the THP split
1437 * to base pages.
1438 *
1439 * Head page is retried immediately and tail
1440 * pages are added to the tail of the list so
1441 * we encounter them after the rest of the list
1442 * is processed.
1443 */
1444 if (PageTransHuge(page) && !PageHuge(page)) {
1445 lock_page(page);
1446 rc = split_huge_page_to_list(page, from);
1447 unlock_page(page);
1448 if (!rc) {
1449 list_safe_reset_next(page, page2, lru);
1450 goto retry;
1451 }
1452 }
1453 nr_failed++;
1454 goto out;
1455 case -EAGAIN:
1456 retry++;
1457 break;
1458 case MIGRATEPAGE_SUCCESS:
1459 nr_succeeded++;
1460 break;
1461 default:
1462 /*
1463 * Permanent failure (-EBUSY, -ENOSYS, etc.):
1464 * unlike -EAGAIN case, the failed page is
1465 * removed from migration page list and not
1466 * retried in the next outer loop.
1467 */
1468 nr_failed++;
1469 break;
1470 }
1471 }
1472 }
1473 nr_failed += retry;
1474 rc = nr_failed;
1475out:
1476 if (nr_succeeded)
1477 count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
1478 if (nr_failed)
1479 count_vm_events(PGMIGRATE_FAIL, nr_failed);
1480 trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason);
1481
1482 if (!swapwrite)
1483 current->flags &= ~PF_SWAPWRITE;
1484
1485 return rc;
1486}
1487
1488#ifdef CONFIG_NUMA
1489
1490static int store_status(int __user *status, int start, int value, int nr)
1491{
1492 while (nr-- > 0) {
1493 if (put_user(value, status + start))
1494 return -EFAULT;
1495 start++;
1496 }
1497
1498 return 0;
1499}
1500
1501static int do_move_pages_to_node(struct mm_struct *mm,
1502 struct list_head *pagelist, int node)
1503{
1504 int err;
1505
1506 if (list_empty(pagelist))
1507 return 0;
1508
1509 err = migrate_pages(pagelist, alloc_new_node_page, NULL, node,
1510 MIGRATE_SYNC, MR_SYSCALL);
1511 if (err)
1512 putback_movable_pages(pagelist);
1513 return err;
1514}
1515
1516/*
1517 * Resolves the given address to a struct page, isolates it from the LRU and
1518 * puts it to the given pagelist.
1519 * Returns -errno if the page cannot be found/isolated or 0 when it has been
1520 * queued or the page doesn't need to be migrated because it is already on
1521 * the target node
1522 */
1523static int add_page_for_migration(struct mm_struct *mm, unsigned long addr,
1524 int node, struct list_head *pagelist, bool migrate_all)
1525{
1526 struct vm_area_struct *vma;
1527 struct page *page;
1528 unsigned int follflags;
1529 int err;
1530
1531 down_read(&mm->mmap_sem);
1532 err = -EFAULT;
1533 vma = find_vma(mm, addr);
1534 if (!vma || addr < vma->vm_start || !vma_migratable(vma))
1535 goto out;
1536
1537 /* FOLL_DUMP to ignore special (like zero) pages */
1538 follflags = FOLL_GET | FOLL_DUMP;
1539 page = follow_page(vma, addr, follflags);
1540
1541 err = PTR_ERR(page);
1542 if (IS_ERR(page))
1543 goto out;
1544
1545 err = -ENOENT;
1546 if (!page)
1547 goto out;
1548
1549 err = 0;
1550 if (page_to_nid(page) == node)
1551 goto out_putpage;
1552
1553 err = -EACCES;
1554 if (page_mapcount(page) > 1 && !migrate_all)
1555 goto out_putpage;
1556
1557 if (PageHuge(page)) {
1558 if (PageHead(page)) {
1559 isolate_huge_page(page, pagelist);
1560 err = 0;
1561 }
1562 } else {
1563 struct page *head;
1564
1565 head = compound_head(page);
1566 err = isolate_lru_page(head);
1567 if (err)
1568 goto out_putpage;
1569
1570 err = 0;
1571 list_add_tail(&head->lru, pagelist);
1572 mod_node_page_state(page_pgdat(head),
1573 NR_ISOLATED_ANON + page_is_file_cache(head),
1574 hpage_nr_pages(head));
1575 }
1576out_putpage:
1577 /*
1578 * Either remove the duplicate refcount from
1579 * isolate_lru_page() or drop the page ref if it was
1580 * not isolated.
1581 */
1582 put_page(page);
1583out:
1584 up_read(&mm->mmap_sem);
1585 return err;
1586}
1587
1588/*
1589 * Migrate an array of page address onto an array of nodes and fill
1590 * the corresponding array of status.
1591 */
1592static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
1593 unsigned long nr_pages,
1594 const void __user * __user *pages,
1595 const int __user *nodes,
1596 int __user *status, int flags)
1597{
1598 int current_node = NUMA_NO_NODE;
1599 LIST_HEAD(pagelist);
1600 int start, i;
1601 int err = 0, err1;
1602
1603 migrate_prep();
1604
1605 for (i = start = 0; i < nr_pages; i++) {
1606 const void __user *p;
1607 unsigned long addr;
1608 int node;
1609
1610 err = -EFAULT;
1611 if (get_user(p, pages + i))
1612 goto out_flush;
1613 if (get_user(node, nodes + i))
1614 goto out_flush;
1615 addr = (unsigned long)untagged_addr(p);
1616
1617 err = -ENODEV;
1618 if (node < 0 || node >= MAX_NUMNODES)
1619 goto out_flush;
1620 if (!node_state(node, N_MEMORY))
1621 goto out_flush;
1622
1623 err = -EACCES;
1624 if (!node_isset(node, task_nodes))
1625 goto out_flush;
1626
1627 if (current_node == NUMA_NO_NODE) {
1628 current_node = node;
1629 start = i;
1630 } else if (node != current_node) {
1631 err = do_move_pages_to_node(mm, &pagelist, current_node);
1632 if (err)
1633 goto out;
1634 err = store_status(status, start, current_node, i - start);
1635 if (err)
1636 goto out;
1637 start = i;
1638 current_node = node;
1639 }
1640
1641 /*
1642 * Errors in the page lookup or isolation are not fatal and we simply
1643 * report them via status
1644 */
1645 err = add_page_for_migration(mm, addr, current_node,
1646 &pagelist, flags & MPOL_MF_MOVE_ALL);
1647 if (!err)
1648 continue;
1649
1650 err = store_status(status, i, err, 1);
1651 if (err)
1652 goto out_flush;
1653
1654 err = do_move_pages_to_node(mm, &pagelist, current_node);
1655 if (err)
1656 goto out;
1657 if (i > start) {
1658 err = store_status(status, start, current_node, i - start);
1659 if (err)
1660 goto out;
1661 }
1662 current_node = NUMA_NO_NODE;
1663 }
1664out_flush:
1665 if (list_empty(&pagelist))
1666 return err;
1667
1668 /* Make sure we do not overwrite the existing error */
1669 err1 = do_move_pages_to_node(mm, &pagelist, current_node);
1670 if (!err1)
1671 err1 = store_status(status, start, current_node, i - start);
1672 if (!err)
1673 err = err1;
1674out:
1675 return err;
1676}
1677
1678/*
1679 * Determine the nodes of an array of pages and store it in an array of status.
1680 */
1681static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
1682 const void __user **pages, int *status)
1683{
1684 unsigned long i;
1685
1686 down_read(&mm->mmap_sem);
1687
1688 for (i = 0; i < nr_pages; i++) {
1689 unsigned long addr = (unsigned long)(*pages);
1690 struct vm_area_struct *vma;
1691 struct page *page;
1692 int err = -EFAULT;
1693
1694 vma = find_vma(mm, addr);
1695 if (!vma || addr < vma->vm_start)
1696 goto set_status;
1697
1698 /* FOLL_DUMP to ignore special (like zero) pages */
1699 page = follow_page(vma, addr, FOLL_DUMP);
1700
1701 err = PTR_ERR(page);
1702 if (IS_ERR(page))
1703 goto set_status;
1704
1705 err = page ? page_to_nid(page) : -ENOENT;
1706set_status:
1707 *status = err;
1708
1709 pages++;
1710 status++;
1711 }
1712
1713 up_read(&mm->mmap_sem);
1714}
1715
1716/*
1717 * Determine the nodes of a user array of pages and store it in
1718 * a user array of status.
1719 */
1720static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
1721 const void __user * __user *pages,
1722 int __user *status)
1723{
1724#define DO_PAGES_STAT_CHUNK_NR 16
1725 const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
1726 int chunk_status[DO_PAGES_STAT_CHUNK_NR];
1727
1728 while (nr_pages) {
1729 unsigned long chunk_nr;
1730
1731 chunk_nr = nr_pages;
1732 if (chunk_nr > DO_PAGES_STAT_CHUNK_NR)
1733 chunk_nr = DO_PAGES_STAT_CHUNK_NR;
1734
1735 if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages)))
1736 break;
1737
1738 do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
1739
1740 if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
1741 break;
1742
1743 pages += chunk_nr;
1744 status += chunk_nr;
1745 nr_pages -= chunk_nr;
1746 }
1747 return nr_pages ? -EFAULT : 0;
1748}
1749
1750/*
1751 * Move a list of pages in the address space of the currently executing
1752 * process.
1753 */
1754static int kernel_move_pages(pid_t pid, unsigned long nr_pages,
1755 const void __user * __user *pages,
1756 const int __user *nodes,
1757 int __user *status, int flags)
1758{
1759 struct task_struct *task;
1760 struct mm_struct *mm;
1761 int err;
1762 nodemask_t task_nodes;
1763
1764 /* Check flags */
1765 if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
1766 return -EINVAL;
1767
1768 if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
1769 return -EPERM;
1770
1771 /* Find the mm_struct */
1772 rcu_read_lock();
1773 task = pid ? find_task_by_vpid(pid) : current;
1774 if (!task) {
1775 rcu_read_unlock();
1776 return -ESRCH;
1777 }
1778 get_task_struct(task);
1779
1780 /*
1781 * Check if this process has the right to modify the specified
1782 * process. Use the regular "ptrace_may_access()" checks.
1783 */
1784 if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
1785 rcu_read_unlock();
1786 err = -EPERM;
1787 goto out;
1788 }
1789 rcu_read_unlock();
1790
1791 err = security_task_movememory(task);
1792 if (err)
1793 goto out;
1794
1795 task_nodes = cpuset_mems_allowed(task);
1796 mm = get_task_mm(task);
1797 put_task_struct(task);
1798
1799 if (!mm)
1800 return -EINVAL;
1801
1802 if (nodes)
1803 err = do_pages_move(mm, task_nodes, nr_pages, pages,
1804 nodes, status, flags);
1805 else
1806 err = do_pages_stat(mm, nr_pages, pages, status);
1807
1808 mmput(mm);
1809 return err;
1810
1811out:
1812 put_task_struct(task);
1813 return err;
1814}
1815
1816SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
1817 const void __user * __user *, pages,
1818 const int __user *, nodes,
1819 int __user *, status, int, flags)
1820{
1821 return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags);
1822}
1823
1824#ifdef CONFIG_COMPAT
1825COMPAT_SYSCALL_DEFINE6(move_pages, pid_t, pid, compat_ulong_t, nr_pages,
1826 compat_uptr_t __user *, pages32,
1827 const int __user *, nodes,
1828 int __user *, status,
1829 int, flags)
1830{
1831 const void __user * __user *pages;
1832 int i;
1833
1834 pages = compat_alloc_user_space(nr_pages * sizeof(void *));
1835 for (i = 0; i < nr_pages; i++) {
1836 compat_uptr_t p;
1837
1838 if (get_user(p, pages32 + i) ||
1839 put_user(compat_ptr(p), pages + i))
1840 return -EFAULT;
1841 }
1842 return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags);
1843}
1844#endif /* CONFIG_COMPAT */
1845
1846#ifdef CONFIG_NUMA_BALANCING
1847/*
1848 * Returns true if this is a safe migration target node for misplaced NUMA
1849 * pages. Currently it only checks the watermarks which crude
1850 */
1851static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
1852 unsigned long nr_migrate_pages)
1853{
1854 int z;
1855
1856 for (z = pgdat->nr_zones - 1; z >= 0; z--) {
1857 struct zone *zone = pgdat->node_zones + z;
1858
1859 if (!populated_zone(zone))
1860 continue;
1861
1862 /* Avoid waking kswapd by allocating pages_to_migrate pages. */
1863 if (!zone_watermark_ok(zone, 0,
1864 high_wmark_pages(zone) +
1865 nr_migrate_pages,
1866 0, 0))
1867 continue;
1868 return true;
1869 }
1870 return false;
1871}
1872
1873static struct page *alloc_misplaced_dst_page(struct page *page,
1874 unsigned long data)
1875{
1876 int nid = (int) data;
1877 struct page *newpage;
1878
1879 newpage = __alloc_pages_node(nid,
1880 (GFP_HIGHUSER_MOVABLE |
1881 __GFP_THISNODE | __GFP_NOMEMALLOC |
1882 __GFP_NORETRY | __GFP_NOWARN) &
1883 ~__GFP_RECLAIM, 0);
1884
1885 return newpage;
1886}
1887
1888static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
1889{
1890 int page_lru;
1891
1892 VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page);
1893
1894 /* Avoid migrating to a node that is nearly full */
1895 if (!migrate_balanced_pgdat(pgdat, compound_nr(page)))
1896 return 0;
1897
1898 if (isolate_lru_page(page))
1899 return 0;
1900
1901 /*
1902 * migrate_misplaced_transhuge_page() skips page migration's usual
1903 * check on page_count(), so we must do it here, now that the page
1904 * has been isolated: a GUP pin, or any other pin, prevents migration.
1905 * The expected page count is 3: 1 for page's mapcount and 1 for the
1906 * caller's pin and 1 for the reference taken by isolate_lru_page().
1907 */
1908 if (PageTransHuge(page) && page_count(page) != 3) {
1909 putback_lru_page(page);
1910 return 0;
1911 }
1912
1913 page_lru = page_is_file_cache(page);
1914 mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_lru,
1915 hpage_nr_pages(page));
1916
1917 /*
1918 * Isolating the page has taken another reference, so the
1919 * caller's reference can be safely dropped without the page
1920 * disappearing underneath us during migration.
1921 */
1922 put_page(page);
1923 return 1;
1924}
1925
1926bool pmd_trans_migrating(pmd_t pmd)
1927{
1928 struct page *page = pmd_page(pmd);
1929 return PageLocked(page);
1930}
1931
1932/*
1933 * Attempt to migrate a misplaced page to the specified destination
1934 * node. Caller is expected to have an elevated reference count on
1935 * the page that will be dropped by this function before returning.
1936 */
1937int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
1938 int node)
1939{
1940 pg_data_t *pgdat = NODE_DATA(node);
1941 int isolated;
1942 int nr_remaining;
1943 LIST_HEAD(migratepages);
1944
1945 /*
1946 * Don't migrate file pages that are mapped in multiple processes
1947 * with execute permissions as they are probably shared libraries.
1948 */
1949 if (page_mapcount(page) != 1 && page_is_file_cache(page) &&
1950 (vma->vm_flags & VM_EXEC))
1951 goto out;
1952
1953 /*
1954 * Also do not migrate dirty pages as not all filesystems can move
1955 * dirty pages in MIGRATE_ASYNC mode which is a waste of cycles.
1956 */
1957 if (page_is_file_cache(page) && PageDirty(page))
1958 goto out;
1959
1960 isolated = numamigrate_isolate_page(pgdat, page);
1961 if (!isolated)
1962 goto out;
1963
1964 list_add(&page->lru, &migratepages);
1965 nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page,
1966 NULL, node, MIGRATE_ASYNC,
1967 MR_NUMA_MISPLACED);
1968 if (nr_remaining) {
1969 if (!list_empty(&migratepages)) {
1970 list_del(&page->lru);
1971 dec_node_page_state(page, NR_ISOLATED_ANON +
1972 page_is_file_cache(page));
1973 putback_lru_page(page);
1974 }
1975 isolated = 0;
1976 } else
1977 count_vm_numa_event(NUMA_PAGE_MIGRATE);
1978 BUG_ON(!list_empty(&migratepages));
1979 return isolated;
1980
1981out:
1982 put_page(page);
1983 return 0;
1984}
1985#endif /* CONFIG_NUMA_BALANCING */
1986
1987#if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
1988/*
1989 * Migrates a THP to a given target node. page must be locked and is unlocked
1990 * before returning.
1991 */
1992int migrate_misplaced_transhuge_page(struct mm_struct *mm,
1993 struct vm_area_struct *vma,
1994 pmd_t *pmd, pmd_t entry,
1995 unsigned long address,
1996 struct page *page, int node)
1997{
1998 spinlock_t *ptl;
1999 pg_data_t *pgdat = NODE_DATA(node);
2000 int isolated = 0;
2001 struct page *new_page = NULL;
2002 int page_lru = page_is_file_cache(page);
2003 unsigned long start = address & HPAGE_PMD_MASK;
2004
2005 new_page = alloc_pages_node(node,
2006 (GFP_TRANSHUGE_LIGHT | __GFP_THISNODE),
2007 HPAGE_PMD_ORDER);
2008 if (!new_page)
2009 goto out_fail;
2010 prep_transhuge_page(new_page);
2011
2012 isolated = numamigrate_isolate_page(pgdat, page);
2013 if (!isolated) {
2014 put_page(new_page);
2015 goto out_fail;
2016 }
2017
2018 /* Prepare a page as a migration target */
2019 __SetPageLocked(new_page);
2020 if (PageSwapBacked(page))
2021 __SetPageSwapBacked(new_page);
2022
2023 /* anon mapping, we can simply copy page->mapping to the new page: */
2024 new_page->mapping = page->mapping;
2025 new_page->index = page->index;
2026 /* flush the cache before copying using the kernel virtual address */
2027 flush_cache_range(vma, start, start + HPAGE_PMD_SIZE);
2028 migrate_page_copy(new_page, page);
2029 WARN_ON(PageLRU(new_page));
2030
2031 /* Recheck the target PMD */
2032 ptl = pmd_lock(mm, pmd);
2033 if (unlikely(!pmd_same(*pmd, entry) || !page_ref_freeze(page, 2))) {
2034 spin_unlock(ptl);
2035
2036 /* Reverse changes made by migrate_page_copy() */
2037 if (TestClearPageActive(new_page))
2038 SetPageActive(page);
2039 if (TestClearPageUnevictable(new_page))
2040 SetPageUnevictable(page);
2041
2042 unlock_page(new_page);
2043 put_page(new_page); /* Free it */
2044
2045 /* Retake the callers reference and putback on LRU */
2046 get_page(page);
2047 putback_lru_page(page);
2048 mod_node_page_state(page_pgdat(page),
2049 NR_ISOLATED_ANON + page_lru, -HPAGE_PMD_NR);
2050
2051 goto out_unlock;
2052 }
2053
2054 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
2055 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
2056
2057 /*
2058 * Overwrite the old entry under pagetable lock and establish
2059 * the new PTE. Any parallel GUP will either observe the old
2060 * page blocking on the page lock, block on the page table
2061 * lock or observe the new page. The SetPageUptodate on the
2062 * new page and page_add_new_anon_rmap guarantee the copy is
2063 * visible before the pagetable update.
2064 */
2065 page_add_anon_rmap(new_page, vma, start, true);
2066 /*
2067 * At this point the pmd is numa/protnone (i.e. non present) and the TLB
2068 * has already been flushed globally. So no TLB can be currently
2069 * caching this non present pmd mapping. There's no need to clear the
2070 * pmd before doing set_pmd_at(), nor to flush the TLB after
2071 * set_pmd_at(). Clearing the pmd here would introduce a race
2072 * condition against MADV_DONTNEED, because MADV_DONTNEED only holds the
2073 * mmap_sem for reading. If the pmd is set to NULL at any given time,
2074 * MADV_DONTNEED won't wait on the pmd lock and it'll skip clearing this
2075 * pmd.
2076 */
2077 set_pmd_at(mm, start, pmd, entry);
2078 update_mmu_cache_pmd(vma, address, &entry);
2079
2080 page_ref_unfreeze(page, 2);
2081 mlock_migrate_page(new_page, page);
2082 page_remove_rmap(page, true);
2083 set_page_owner_migrate_reason(new_page, MR_NUMA_MISPLACED);
2084
2085 spin_unlock(ptl);
2086
2087 /* Take an "isolate" reference and put new page on the LRU. */
2088 get_page(new_page);
2089 putback_lru_page(new_page);
2090
2091 unlock_page(new_page);
2092 unlock_page(page);
2093 put_page(page); /* Drop the rmap reference */
2094 put_page(page); /* Drop the LRU isolation reference */
2095
2096 count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR);
2097 count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR);
2098
2099 mod_node_page_state(page_pgdat(page),
2100 NR_ISOLATED_ANON + page_lru,
2101 -HPAGE_PMD_NR);
2102 return isolated;
2103
2104out_fail:
2105 count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
2106 ptl = pmd_lock(mm, pmd);
2107 if (pmd_same(*pmd, entry)) {
2108 entry = pmd_modify(entry, vma->vm_page_prot);
2109 set_pmd_at(mm, start, pmd, entry);
2110 update_mmu_cache_pmd(vma, address, &entry);
2111 }
2112 spin_unlock(ptl);
2113
2114out_unlock:
2115 unlock_page(page);
2116 put_page(page);
2117 return 0;
2118}
2119#endif /* CONFIG_NUMA_BALANCING */
2120
2121#endif /* CONFIG_NUMA */
2122
2123#ifdef CONFIG_DEVICE_PRIVATE
2124static int migrate_vma_collect_hole(unsigned long start,
2125 unsigned long end,
2126 struct mm_walk *walk)
2127{
2128 struct migrate_vma *migrate = walk->private;
2129 unsigned long addr;
2130
2131 for (addr = start & PAGE_MASK; addr < end; addr += PAGE_SIZE) {
2132 migrate->src[migrate->npages] = MIGRATE_PFN_MIGRATE;
2133 migrate->dst[migrate->npages] = 0;
2134 migrate->npages++;
2135 migrate->cpages++;
2136 }
2137
2138 return 0;
2139}
2140
2141static int migrate_vma_collect_skip(unsigned long start,
2142 unsigned long end,
2143 struct mm_walk *walk)
2144{
2145 struct migrate_vma *migrate = walk->private;
2146 unsigned long addr;
2147
2148 for (addr = start & PAGE_MASK; addr < end; addr += PAGE_SIZE) {
2149 migrate->dst[migrate->npages] = 0;
2150 migrate->src[migrate->npages++] = 0;
2151 }
2152
2153 return 0;
2154}
2155
2156static int migrate_vma_collect_pmd(pmd_t *pmdp,
2157 unsigned long start,
2158 unsigned long end,
2159 struct mm_walk *walk)
2160{
2161 struct migrate_vma *migrate = walk->private;
2162 struct vm_area_struct *vma = walk->vma;
2163 struct mm_struct *mm = vma->vm_mm;
2164 unsigned long addr = start, unmapped = 0;
2165 spinlock_t *ptl;
2166 pte_t *ptep;
2167
2168again:
2169 if (pmd_none(*pmdp))
2170 return migrate_vma_collect_hole(start, end, walk);
2171
2172 if (pmd_trans_huge(*pmdp)) {
2173 struct page *page;
2174
2175 ptl = pmd_lock(mm, pmdp);
2176 if (unlikely(!pmd_trans_huge(*pmdp))) {
2177 spin_unlock(ptl);
2178 goto again;
2179 }
2180
2181 page = pmd_page(*pmdp);
2182 if (is_huge_zero_page(page)) {
2183 spin_unlock(ptl);
2184 split_huge_pmd(vma, pmdp, addr);
2185 if (pmd_trans_unstable(pmdp))
2186 return migrate_vma_collect_skip(start, end,
2187 walk);
2188 } else {
2189 int ret;
2190
2191 get_page(page);
2192 spin_unlock(ptl);
2193 if (unlikely(!trylock_page(page)))
2194 return migrate_vma_collect_skip(start, end,
2195 walk);
2196 ret = split_huge_page(page);
2197 unlock_page(page);
2198 put_page(page);
2199 if (ret)
2200 return migrate_vma_collect_skip(start, end,
2201 walk);
2202 if (pmd_none(*pmdp))
2203 return migrate_vma_collect_hole(start, end,
2204 walk);
2205 }
2206 }
2207
2208 if (unlikely(pmd_bad(*pmdp)))
2209 return migrate_vma_collect_skip(start, end, walk);
2210
2211 ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
2212 arch_enter_lazy_mmu_mode();
2213
2214 for (; addr < end; addr += PAGE_SIZE, ptep++) {
2215 unsigned long mpfn, pfn;
2216 struct page *page;
2217 swp_entry_t entry;
2218 pte_t pte;
2219
2220 pte = *ptep;
2221
2222 if (pte_none(pte)) {
2223 mpfn = MIGRATE_PFN_MIGRATE;
2224 migrate->cpages++;
2225 goto next;
2226 }
2227
2228 if (!pte_present(pte)) {
2229 mpfn = 0;
2230
2231 /*
2232 * Only care about unaddressable device page special
2233 * page table entry. Other special swap entries are not
2234 * migratable, and we ignore regular swapped page.
2235 */
2236 entry = pte_to_swp_entry(pte);
2237 if (!is_device_private_entry(entry))
2238 goto next;
2239
2240 page = device_private_entry_to_page(entry);
2241 mpfn = migrate_pfn(page_to_pfn(page)) |
2242 MIGRATE_PFN_MIGRATE;
2243 if (is_write_device_private_entry(entry))
2244 mpfn |= MIGRATE_PFN_WRITE;
2245 } else {
2246 pfn = pte_pfn(pte);
2247 if (is_zero_pfn(pfn)) {
2248 mpfn = MIGRATE_PFN_MIGRATE;
2249 migrate->cpages++;
2250 goto next;
2251 }
2252 page = vm_normal_page(migrate->vma, addr, pte);
2253 mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
2254 mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
2255 }
2256
2257 /* FIXME support THP */
2258 if (!page || !page->mapping || PageTransCompound(page)) {
2259 mpfn = 0;
2260 goto next;
2261 }
2262
2263 /*
2264 * By getting a reference on the page we pin it and that blocks
2265 * any kind of migration. Side effect is that it "freezes" the
2266 * pte.
2267 *
2268 * We drop this reference after isolating the page from the lru
2269 * for non device page (device page are not on the lru and thus
2270 * can't be dropped from it).
2271 */
2272 get_page(page);
2273 migrate->cpages++;
2274
2275 /*
2276 * Optimize for the common case where page is only mapped once
2277 * in one process. If we can lock the page, then we can safely
2278 * set up a special migration page table entry now.
2279 */
2280 if (trylock_page(page)) {
2281 pte_t swp_pte;
2282
2283 mpfn |= MIGRATE_PFN_LOCKED;
2284 ptep_get_and_clear(mm, addr, ptep);
2285
2286 /* Setup special migration page table entry */
2287 entry = make_migration_entry(page, mpfn &
2288 MIGRATE_PFN_WRITE);
2289 swp_pte = swp_entry_to_pte(entry);
2290 if (pte_soft_dirty(pte))
2291 swp_pte = pte_swp_mksoft_dirty(swp_pte);
2292 set_pte_at(mm, addr, ptep, swp_pte);
2293
2294 /*
2295 * This is like regular unmap: we remove the rmap and
2296 * drop page refcount. Page won't be freed, as we took
2297 * a reference just above.
2298 */
2299 page_remove_rmap(page, false);
2300 put_page(page);
2301
2302 if (pte_present(pte))
2303 unmapped++;
2304 }
2305
2306next:
2307 migrate->dst[migrate->npages] = 0;
2308 migrate->src[migrate->npages++] = mpfn;
2309 }
2310 arch_leave_lazy_mmu_mode();
2311 pte_unmap_unlock(ptep - 1, ptl);
2312
2313 /* Only flush the TLB if we actually modified any entries */
2314 if (unmapped)
2315 flush_tlb_range(walk->vma, start, end);
2316
2317 return 0;
2318}
2319
2320static const struct mm_walk_ops migrate_vma_walk_ops = {
2321 .pmd_entry = migrate_vma_collect_pmd,
2322 .pte_hole = migrate_vma_collect_hole,
2323};
2324
2325/*
2326 * migrate_vma_collect() - collect pages over a range of virtual addresses
2327 * @migrate: migrate struct containing all migration information
2328 *
2329 * This will walk the CPU page table. For each virtual address backed by a
2330 * valid page, it updates the src array and takes a reference on the page, in
2331 * order to pin the page until we lock it and unmap it.
2332 */
2333static void migrate_vma_collect(struct migrate_vma *migrate)
2334{
2335 struct mmu_notifier_range range;
2336
2337 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL,
2338 migrate->vma->vm_mm, migrate->start, migrate->end);
2339 mmu_notifier_invalidate_range_start(&range);
2340
2341 walk_page_range(migrate->vma->vm_mm, migrate->start, migrate->end,
2342 &migrate_vma_walk_ops, migrate);
2343
2344 mmu_notifier_invalidate_range_end(&range);
2345 migrate->end = migrate->start + (migrate->npages << PAGE_SHIFT);
2346}
2347
2348/*
2349 * migrate_vma_check_page() - check if page is pinned or not
2350 * @page: struct page to check
2351 *
2352 * Pinned pages cannot be migrated. This is the same test as in
2353 * migrate_page_move_mapping(), except that here we allow migration of a
2354 * ZONE_DEVICE page.
2355 */
2356static bool migrate_vma_check_page(struct page *page)
2357{
2358 /*
2359 * One extra ref because caller holds an extra reference, either from
2360 * isolate_lru_page() for a regular page, or migrate_vma_collect() for
2361 * a device page.
2362 */
2363 int extra = 1;
2364
2365 /*
2366 * FIXME support THP (transparent huge page), it is bit more complex to
2367 * check them than regular pages, because they can be mapped with a pmd
2368 * or with a pte (split pte mapping).
2369 */
2370 if (PageCompound(page))
2371 return false;
2372
2373 /* Page from ZONE_DEVICE have one extra reference */
2374 if (is_zone_device_page(page)) {
2375 /*
2376 * Private page can never be pin as they have no valid pte and
2377 * GUP will fail for those. Yet if there is a pending migration
2378 * a thread might try to wait on the pte migration entry and
2379 * will bump the page reference count. Sadly there is no way to
2380 * differentiate a regular pin from migration wait. Hence to
2381 * avoid 2 racing thread trying to migrate back to CPU to enter
2382 * infinite loop (one stoping migration because the other is
2383 * waiting on pte migration entry). We always return true here.
2384 *
2385 * FIXME proper solution is to rework migration_entry_wait() so
2386 * it does not need to take a reference on page.
2387 */
2388 return is_device_private_page(page);
2389 }
2390
2391 /* For file back page */
2392 if (page_mapping(page))
2393 extra += 1 + page_has_private(page);
2394
2395 if ((page_count(page) - extra) > page_mapcount(page))
2396 return false;
2397
2398 return true;
2399}
2400
2401/*
2402 * migrate_vma_prepare() - lock pages and isolate them from the lru
2403 * @migrate: migrate struct containing all migration information
2404 *
2405 * This locks pages that have been collected by migrate_vma_collect(). Once each
2406 * page is locked it is isolated from the lru (for non-device pages). Finally,
2407 * the ref taken by migrate_vma_collect() is dropped, as locked pages cannot be
2408 * migrated by concurrent kernel threads.
2409 */
2410static void migrate_vma_prepare(struct migrate_vma *migrate)
2411{
2412 const unsigned long npages = migrate->npages;
2413 const unsigned long start = migrate->start;
2414 unsigned long addr, i, restore = 0;
2415 bool allow_drain = true;
2416
2417 lru_add_drain();
2418
2419 for (i = 0; (i < npages) && migrate->cpages; i++) {
2420 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2421 bool remap = true;
2422
2423 if (!page)
2424 continue;
2425
2426 if (!(migrate->src[i] & MIGRATE_PFN_LOCKED)) {
2427 /*
2428 * Because we are migrating several pages there can be
2429 * a deadlock between 2 concurrent migration where each
2430 * are waiting on each other page lock.
2431 *
2432 * Make migrate_vma() a best effort thing and backoff
2433 * for any page we can not lock right away.
2434 */
2435 if (!trylock_page(page)) {
2436 migrate->src[i] = 0;
2437 migrate->cpages--;
2438 put_page(page);
2439 continue;
2440 }
2441 remap = false;
2442 migrate->src[i] |= MIGRATE_PFN_LOCKED;
2443 }
2444
2445 /* ZONE_DEVICE pages are not on LRU */
2446 if (!is_zone_device_page(page)) {
2447 if (!PageLRU(page) && allow_drain) {
2448 /* Drain CPU's pagevec */
2449 lru_add_drain_all();
2450 allow_drain = false;
2451 }
2452
2453 if (isolate_lru_page(page)) {
2454 if (remap) {
2455 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2456 migrate->cpages--;
2457 restore++;
2458 } else {
2459 migrate->src[i] = 0;
2460 unlock_page(page);
2461 migrate->cpages--;
2462 put_page(page);
2463 }
2464 continue;
2465 }
2466
2467 /* Drop the reference we took in collect */
2468 put_page(page);
2469 }
2470
2471 if (!migrate_vma_check_page(page)) {
2472 if (remap) {
2473 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2474 migrate->cpages--;
2475 restore++;
2476
2477 if (!is_zone_device_page(page)) {
2478 get_page(page);
2479 putback_lru_page(page);
2480 }
2481 } else {
2482 migrate->src[i] = 0;
2483 unlock_page(page);
2484 migrate->cpages--;
2485
2486 if (!is_zone_device_page(page))
2487 putback_lru_page(page);
2488 else
2489 put_page(page);
2490 }
2491 }
2492 }
2493
2494 for (i = 0, addr = start; i < npages && restore; i++, addr += PAGE_SIZE) {
2495 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2496
2497 if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE))
2498 continue;
2499
2500 remove_migration_pte(page, migrate->vma, addr, page);
2501
2502 migrate->src[i] = 0;
2503 unlock_page(page);
2504 put_page(page);
2505 restore--;
2506 }
2507}
2508
2509/*
2510 * migrate_vma_unmap() - replace page mapping with special migration pte entry
2511 * @migrate: migrate struct containing all migration information
2512 *
2513 * Replace page mapping (CPU page table pte) with a special migration pte entry
2514 * and check again if it has been pinned. Pinned pages are restored because we
2515 * cannot migrate them.
2516 *
2517 * This is the last step before we call the device driver callback to allocate
2518 * destination memory and copy contents of original page over to new page.
2519 */
2520static void migrate_vma_unmap(struct migrate_vma *migrate)
2521{
2522 int flags = TTU_MIGRATION | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
2523 const unsigned long npages = migrate->npages;
2524 const unsigned long start = migrate->start;
2525 unsigned long addr, i, restore = 0;
2526
2527 for (i = 0; i < npages; i++) {
2528 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2529
2530 if (!page || !(migrate->src[i] & MIGRATE_PFN_MIGRATE))
2531 continue;
2532
2533 if (page_mapped(page)) {
2534 try_to_unmap(page, flags);
2535 if (page_mapped(page))
2536 goto restore;
2537 }
2538
2539 if (migrate_vma_check_page(page))
2540 continue;
2541
2542restore:
2543 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2544 migrate->cpages--;
2545 restore++;
2546 }
2547
2548 for (addr = start, i = 0; i < npages && restore; addr += PAGE_SIZE, i++) {
2549 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2550
2551 if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE))
2552 continue;
2553
2554 remove_migration_ptes(page, page, false);
2555
2556 migrate->src[i] = 0;
2557 unlock_page(page);
2558 restore--;
2559
2560 if (is_zone_device_page(page))
2561 put_page(page);
2562 else
2563 putback_lru_page(page);
2564 }
2565}
2566
2567/**
2568 * migrate_vma_setup() - prepare to migrate a range of memory
2569 * @args: contains the vma, start, and and pfns arrays for the migration
2570 *
2571 * Returns: negative errno on failures, 0 when 0 or more pages were migrated
2572 * without an error.
2573 *
2574 * Prepare to migrate a range of memory virtual address range by collecting all
2575 * the pages backing each virtual address in the range, saving them inside the
2576 * src array. Then lock those pages and unmap them. Once the pages are locked
2577 * and unmapped, check whether each page is pinned or not. Pages that aren't
2578 * pinned have the MIGRATE_PFN_MIGRATE flag set (by this function) in the
2579 * corresponding src array entry. Then restores any pages that are pinned, by
2580 * remapping and unlocking those pages.
2581 *
2582 * The caller should then allocate destination memory and copy source memory to
2583 * it for all those entries (ie with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE
2584 * flag set). Once these are allocated and copied, the caller must update each
2585 * corresponding entry in the dst array with the pfn value of the destination
2586 * page and with the MIGRATE_PFN_VALID and MIGRATE_PFN_LOCKED flags set
2587 * (destination pages must have their struct pages locked, via lock_page()).
2588 *
2589 * Note that the caller does not have to migrate all the pages that are marked
2590 * with MIGRATE_PFN_MIGRATE flag in src array unless this is a migration from
2591 * device memory to system memory. If the caller cannot migrate a device page
2592 * back to system memory, then it must return VM_FAULT_SIGBUS, which has severe
2593 * consequences for the userspace process, so it must be avoided if at all
2594 * possible.
2595 *
2596 * For empty entries inside CPU page table (pte_none() or pmd_none() is true) we
2597 * do set MIGRATE_PFN_MIGRATE flag inside the corresponding source array thus
2598 * allowing the caller to allocate device memory for those unback virtual
2599 * address. For this the caller simply has to allocate device memory and
2600 * properly set the destination entry like for regular migration. Note that
2601 * this can still fails and thus inside the device driver must check if the
2602 * migration was successful for those entries after calling migrate_vma_pages()
2603 * just like for regular migration.
2604 *
2605 * After that, the callers must call migrate_vma_pages() to go over each entry
2606 * in the src array that has the MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag
2607 * set. If the corresponding entry in dst array has MIGRATE_PFN_VALID flag set,
2608 * then migrate_vma_pages() to migrate struct page information from the source
2609 * struct page to the destination struct page. If it fails to migrate the
2610 * struct page information, then it clears the MIGRATE_PFN_MIGRATE flag in the
2611 * src array.
2612 *
2613 * At this point all successfully migrated pages have an entry in the src
2614 * array with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag set and the dst
2615 * array entry with MIGRATE_PFN_VALID flag set.
2616 *
2617 * Once migrate_vma_pages() returns the caller may inspect which pages were
2618 * successfully migrated, and which were not. Successfully migrated pages will
2619 * have the MIGRATE_PFN_MIGRATE flag set for their src array entry.
2620 *
2621 * It is safe to update device page table after migrate_vma_pages() because
2622 * both destination and source page are still locked, and the mmap_sem is held
2623 * in read mode (hence no one can unmap the range being migrated).
2624 *
2625 * Once the caller is done cleaning up things and updating its page table (if it
2626 * chose to do so, this is not an obligation) it finally calls
2627 * migrate_vma_finalize() to update the CPU page table to point to new pages
2628 * for successfully migrated pages or otherwise restore the CPU page table to
2629 * point to the original source pages.
2630 */
2631int migrate_vma_setup(struct migrate_vma *args)
2632{
2633 long nr_pages = (args->end - args->start) >> PAGE_SHIFT;
2634
2635 args->start &= PAGE_MASK;
2636 args->end &= PAGE_MASK;
2637 if (!args->vma || is_vm_hugetlb_page(args->vma) ||
2638 (args->vma->vm_flags & VM_SPECIAL) || vma_is_dax(args->vma))
2639 return -EINVAL;
2640 if (nr_pages <= 0)
2641 return -EINVAL;
2642 if (args->start < args->vma->vm_start ||
2643 args->start >= args->vma->vm_end)
2644 return -EINVAL;
2645 if (args->end <= args->vma->vm_start || args->end > args->vma->vm_end)
2646 return -EINVAL;
2647 if (!args->src || !args->dst)
2648 return -EINVAL;
2649
2650 memset(args->src, 0, sizeof(*args->src) * nr_pages);
2651 args->cpages = 0;
2652 args->npages = 0;
2653
2654 migrate_vma_collect(args);
2655
2656 if (args->cpages)
2657 migrate_vma_prepare(args);
2658 if (args->cpages)
2659 migrate_vma_unmap(args);
2660
2661 /*
2662 * At this point pages are locked and unmapped, and thus they have
2663 * stable content and can safely be copied to destination memory that
2664 * is allocated by the drivers.
2665 */
2666 return 0;
2667
2668}
2669EXPORT_SYMBOL(migrate_vma_setup);
2670
2671static void migrate_vma_insert_page(struct migrate_vma *migrate,
2672 unsigned long addr,
2673 struct page *page,
2674 unsigned long *src,
2675 unsigned long *dst)
2676{
2677 struct vm_area_struct *vma = migrate->vma;
2678 struct mm_struct *mm = vma->vm_mm;
2679 struct mem_cgroup *memcg;
2680 bool flush = false;
2681 spinlock_t *ptl;
2682 pte_t entry;
2683 pgd_t *pgdp;
2684 p4d_t *p4dp;
2685 pud_t *pudp;
2686 pmd_t *pmdp;
2687 pte_t *ptep;
2688
2689 /* Only allow populating anonymous memory */
2690 if (!vma_is_anonymous(vma))
2691 goto abort;
2692
2693 pgdp = pgd_offset(mm, addr);
2694 p4dp = p4d_alloc(mm, pgdp, addr);
2695 if (!p4dp)
2696 goto abort;
2697 pudp = pud_alloc(mm, p4dp, addr);
2698 if (!pudp)
2699 goto abort;
2700 pmdp = pmd_alloc(mm, pudp, addr);
2701 if (!pmdp)
2702 goto abort;
2703
2704 if (pmd_trans_huge(*pmdp) || pmd_devmap(*pmdp))
2705 goto abort;
2706
2707 /*
2708 * Use pte_alloc() instead of pte_alloc_map(). We can't run
2709 * pte_offset_map() on pmds where a huge pmd might be created
2710 * from a different thread.
2711 *
2712 * pte_alloc_map() is safe to use under down_write(mmap_sem) or when
2713 * parallel threads are excluded by other means.
2714 *
2715 * Here we only have down_read(mmap_sem).
2716 */
2717 if (pte_alloc(mm, pmdp))
2718 goto abort;
2719
2720 /* See the comment in pte_alloc_one_map() */
2721 if (unlikely(pmd_trans_unstable(pmdp)))
2722 goto abort;
2723
2724 if (unlikely(anon_vma_prepare(vma)))
2725 goto abort;
2726 if (mem_cgroup_try_charge(page, vma->vm_mm, GFP_KERNEL, &memcg, false))
2727 goto abort;
2728
2729 /*
2730 * The memory barrier inside __SetPageUptodate makes sure that
2731 * preceding stores to the page contents become visible before
2732 * the set_pte_at() write.
2733 */
2734 __SetPageUptodate(page);
2735
2736 if (is_zone_device_page(page)) {
2737 if (is_device_private_page(page)) {
2738 swp_entry_t swp_entry;
2739
2740 swp_entry = make_device_private_entry(page, vma->vm_flags & VM_WRITE);
2741 entry = swp_entry_to_pte(swp_entry);
2742 }
2743 } else {
2744 entry = mk_pte(page, vma->vm_page_prot);
2745 if (vma->vm_flags & VM_WRITE)
2746 entry = pte_mkwrite(pte_mkdirty(entry));
2747 }
2748
2749 ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
2750
2751 if (pte_present(*ptep)) {
2752 unsigned long pfn = pte_pfn(*ptep);
2753
2754 if (!is_zero_pfn(pfn)) {
2755 pte_unmap_unlock(ptep, ptl);
2756 mem_cgroup_cancel_charge(page, memcg, false);
2757 goto abort;
2758 }
2759 flush = true;
2760 } else if (!pte_none(*ptep)) {
2761 pte_unmap_unlock(ptep, ptl);
2762 mem_cgroup_cancel_charge(page, memcg, false);
2763 goto abort;
2764 }
2765
2766 /*
2767 * Check for usefaultfd but do not deliver the fault. Instead,
2768 * just back off.
2769 */
2770 if (userfaultfd_missing(vma)) {
2771 pte_unmap_unlock(ptep, ptl);
2772 mem_cgroup_cancel_charge(page, memcg, false);
2773 goto abort;
2774 }
2775
2776 inc_mm_counter(mm, MM_ANONPAGES);
2777 page_add_new_anon_rmap(page, vma, addr, false);
2778 mem_cgroup_commit_charge(page, memcg, false, false);
2779 if (!is_zone_device_page(page))
2780 lru_cache_add_active_or_unevictable(page, vma);
2781 get_page(page);
2782
2783 if (flush) {
2784 flush_cache_page(vma, addr, pte_pfn(*ptep));
2785 ptep_clear_flush_notify(vma, addr, ptep);
2786 set_pte_at_notify(mm, addr, ptep, entry);
2787 update_mmu_cache(vma, addr, ptep);
2788 } else {
2789 /* No need to invalidate - it was non-present before */
2790 set_pte_at(mm, addr, ptep, entry);
2791 update_mmu_cache(vma, addr, ptep);
2792 }
2793
2794 pte_unmap_unlock(ptep, ptl);
2795 *src = MIGRATE_PFN_MIGRATE;
2796 return;
2797
2798abort:
2799 *src &= ~MIGRATE_PFN_MIGRATE;
2800}
2801
2802/**
2803 * migrate_vma_pages() - migrate meta-data from src page to dst page
2804 * @migrate: migrate struct containing all migration information
2805 *
2806 * This migrates struct page meta-data from source struct page to destination
2807 * struct page. This effectively finishes the migration from source page to the
2808 * destination page.
2809 */
2810void migrate_vma_pages(struct migrate_vma *migrate)
2811{
2812 const unsigned long npages = migrate->npages;
2813 const unsigned long start = migrate->start;
2814 struct mmu_notifier_range range;
2815 unsigned long addr, i;
2816 bool notified = false;
2817
2818 for (i = 0, addr = start; i < npages; addr += PAGE_SIZE, i++) {
2819 struct page *newpage = migrate_pfn_to_page(migrate->dst[i]);
2820 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2821 struct address_space *mapping;
2822 int r;
2823
2824 if (!newpage) {
2825 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2826 continue;
2827 }
2828
2829 if (!page) {
2830 if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE)) {
2831 continue;
2832 }
2833 if (!notified) {
2834 notified = true;
2835
2836 mmu_notifier_range_init(&range,
2837 MMU_NOTIFY_CLEAR, 0,
2838 NULL,
2839 migrate->vma->vm_mm,
2840 addr, migrate->end);
2841 mmu_notifier_invalidate_range_start(&range);
2842 }
2843 migrate_vma_insert_page(migrate, addr, newpage,
2844 &migrate->src[i],
2845 &migrate->dst[i]);
2846 continue;
2847 }
2848
2849 mapping = page_mapping(page);
2850
2851 if (is_zone_device_page(newpage)) {
2852 if (is_device_private_page(newpage)) {
2853 /*
2854 * For now only support private anonymous when
2855 * migrating to un-addressable device memory.
2856 */
2857 if (mapping) {
2858 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2859 continue;
2860 }
2861 } else {
2862 /*
2863 * Other types of ZONE_DEVICE page are not
2864 * supported.
2865 */
2866 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2867 continue;
2868 }
2869 }
2870
2871 r = migrate_page(mapping, newpage, page, MIGRATE_SYNC_NO_COPY);
2872 if (r != MIGRATEPAGE_SUCCESS)
2873 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2874 }
2875
2876 /*
2877 * No need to double call mmu_notifier->invalidate_range() callback as
2878 * the above ptep_clear_flush_notify() inside migrate_vma_insert_page()
2879 * did already call it.
2880 */
2881 if (notified)
2882 mmu_notifier_invalidate_range_only_end(&range);
2883}
2884EXPORT_SYMBOL(migrate_vma_pages);
2885
2886/**
2887 * migrate_vma_finalize() - restore CPU page table entry
2888 * @migrate: migrate struct containing all migration information
2889 *
2890 * This replaces the special migration pte entry with either a mapping to the
2891 * new page if migration was successful for that page, or to the original page
2892 * otherwise.
2893 *
2894 * This also unlocks the pages and puts them back on the lru, or drops the extra
2895 * refcount, for device pages.
2896 */
2897void migrate_vma_finalize(struct migrate_vma *migrate)
2898{
2899 const unsigned long npages = migrate->npages;
2900 unsigned long i;
2901
2902 for (i = 0; i < npages; i++) {
2903 struct page *newpage = migrate_pfn_to_page(migrate->dst[i]);
2904 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2905
2906 if (!page) {
2907 if (newpage) {
2908 unlock_page(newpage);
2909 put_page(newpage);
2910 }
2911 continue;
2912 }
2913
2914 if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE) || !newpage) {
2915 if (newpage) {
2916 unlock_page(newpage);
2917 put_page(newpage);
2918 }
2919 newpage = page;
2920 }
2921
2922 remove_migration_ptes(page, newpage, false);
2923 unlock_page(page);
2924 migrate->cpages--;
2925
2926 if (is_zone_device_page(page))
2927 put_page(page);
2928 else
2929 putback_lru_page(page);
2930
2931 if (newpage != page) {
2932 unlock_page(newpage);
2933 if (is_zone_device_page(newpage))
2934 put_page(newpage);
2935 else
2936 putback_lru_page(newpage);
2937 }
2938 }
2939}
2940EXPORT_SYMBOL(migrate_vma_finalize);
2941#endif /* CONFIG_DEVICE_PRIVATE */
1/*
2 * Memory Migration functionality - linux/mm/migrate.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/backing-dev.h>
34#include <linux/compaction.h>
35#include <linux/syscalls.h>
36#include <linux/hugetlb.h>
37#include <linux/hugetlb_cgroup.h>
38#include <linux/gfp.h>
39#include <linux/balloon_compaction.h>
40#include <linux/mmu_notifier.h>
41#include <linux/page_idle.h>
42#include <linux/page_owner.h>
43
44#include <asm/tlbflush.h>
45
46#define CREATE_TRACE_POINTS
47#include <trace/events/migrate.h>
48
49#include "internal.h"
50
51/*
52 * migrate_prep() needs to be called before we start compiling a list of pages
53 * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
54 * undesirable, use migrate_prep_local()
55 */
56int migrate_prep(void)
57{
58 /*
59 * Clear the LRU lists so pages can be isolated.
60 * Note that pages may be moved off the LRU after we have
61 * drained them. Those pages will fail to migrate like other
62 * pages that may be busy.
63 */
64 lru_add_drain_all();
65
66 return 0;
67}
68
69/* Do the necessary work of migrate_prep but not if it involves other CPUs */
70int migrate_prep_local(void)
71{
72 lru_add_drain();
73
74 return 0;
75}
76
77bool isolate_movable_page(struct page *page, isolate_mode_t mode)
78{
79 struct address_space *mapping;
80
81 /*
82 * Avoid burning cycles with pages that are yet under __free_pages(),
83 * or just got freed under us.
84 *
85 * In case we 'win' a race for a movable page being freed under us and
86 * raise its refcount preventing __free_pages() from doing its job
87 * the put_page() at the end of this block will take care of
88 * release this page, thus avoiding a nasty leakage.
89 */
90 if (unlikely(!get_page_unless_zero(page)))
91 goto out;
92
93 /*
94 * Check PageMovable before holding a PG_lock because page's owner
95 * assumes anybody doesn't touch PG_lock of newly allocated page
96 * so unconditionally grapping the lock ruins page's owner side.
97 */
98 if (unlikely(!__PageMovable(page)))
99 goto out_putpage;
100 /*
101 * As movable pages are not isolated from LRU lists, concurrent
102 * compaction threads can race against page migration functions
103 * as well as race against the releasing a page.
104 *
105 * In order to avoid having an already isolated movable page
106 * being (wrongly) re-isolated while it is under migration,
107 * or to avoid attempting to isolate pages being released,
108 * lets be sure we have the page lock
109 * before proceeding with the movable page isolation steps.
110 */
111 if (unlikely(!trylock_page(page)))
112 goto out_putpage;
113
114 if (!PageMovable(page) || PageIsolated(page))
115 goto out_no_isolated;
116
117 mapping = page_mapping(page);
118 VM_BUG_ON_PAGE(!mapping, page);
119
120 if (!mapping->a_ops->isolate_page(page, mode))
121 goto out_no_isolated;
122
123 /* Driver shouldn't use PG_isolated bit of page->flags */
124 WARN_ON_ONCE(PageIsolated(page));
125 __SetPageIsolated(page);
126 unlock_page(page);
127
128 return true;
129
130out_no_isolated:
131 unlock_page(page);
132out_putpage:
133 put_page(page);
134out:
135 return false;
136}
137
138/* It should be called on page which is PG_movable */
139void putback_movable_page(struct page *page)
140{
141 struct address_space *mapping;
142
143 VM_BUG_ON_PAGE(!PageLocked(page), page);
144 VM_BUG_ON_PAGE(!PageMovable(page), page);
145 VM_BUG_ON_PAGE(!PageIsolated(page), page);
146
147 mapping = page_mapping(page);
148 mapping->a_ops->putback_page(page);
149 __ClearPageIsolated(page);
150}
151
152/*
153 * Put previously isolated pages back onto the appropriate lists
154 * from where they were once taken off for compaction/migration.
155 *
156 * This function shall be used whenever the isolated pageset has been
157 * built from lru, balloon, hugetlbfs page. See isolate_migratepages_range()
158 * and isolate_huge_page().
159 */
160void putback_movable_pages(struct list_head *l)
161{
162 struct page *page;
163 struct page *page2;
164
165 list_for_each_entry_safe(page, page2, l, lru) {
166 if (unlikely(PageHuge(page))) {
167 putback_active_hugepage(page);
168 continue;
169 }
170 list_del(&page->lru);
171 /*
172 * We isolated non-lru movable page so here we can use
173 * __PageMovable because LRU page's mapping cannot have
174 * PAGE_MAPPING_MOVABLE.
175 */
176 if (unlikely(__PageMovable(page))) {
177 VM_BUG_ON_PAGE(!PageIsolated(page), page);
178 lock_page(page);
179 if (PageMovable(page))
180 putback_movable_page(page);
181 else
182 __ClearPageIsolated(page);
183 unlock_page(page);
184 put_page(page);
185 } else {
186 putback_lru_page(page);
187 dec_node_page_state(page, NR_ISOLATED_ANON +
188 page_is_file_cache(page));
189 }
190 }
191}
192
193/*
194 * Restore a potential migration pte to a working pte entry
195 */
196static int remove_migration_pte(struct page *new, struct vm_area_struct *vma,
197 unsigned long addr, void *old)
198{
199 struct mm_struct *mm = vma->vm_mm;
200 swp_entry_t entry;
201 pmd_t *pmd;
202 pte_t *ptep, pte;
203 spinlock_t *ptl;
204
205 if (unlikely(PageHuge(new))) {
206 ptep = huge_pte_offset(mm, addr);
207 if (!ptep)
208 goto out;
209 ptl = huge_pte_lockptr(hstate_vma(vma), mm, ptep);
210 } else {
211 pmd = mm_find_pmd(mm, addr);
212 if (!pmd)
213 goto out;
214
215 ptep = pte_offset_map(pmd, addr);
216
217 /*
218 * Peek to check is_swap_pte() before taking ptlock? No, we
219 * can race mremap's move_ptes(), which skips anon_vma lock.
220 */
221
222 ptl = pte_lockptr(mm, pmd);
223 }
224
225 spin_lock(ptl);
226 pte = *ptep;
227 if (!is_swap_pte(pte))
228 goto unlock;
229
230 entry = pte_to_swp_entry(pte);
231
232 if (!is_migration_entry(entry) ||
233 migration_entry_to_page(entry) != old)
234 goto unlock;
235
236 get_page(new);
237 pte = pte_mkold(mk_pte(new, READ_ONCE(vma->vm_page_prot)));
238 if (pte_swp_soft_dirty(*ptep))
239 pte = pte_mksoft_dirty(pte);
240
241 /* Recheck VMA as permissions can change since migration started */
242 if (is_write_migration_entry(entry))
243 pte = maybe_mkwrite(pte, vma);
244
245#ifdef CONFIG_HUGETLB_PAGE
246 if (PageHuge(new)) {
247 pte = pte_mkhuge(pte);
248 pte = arch_make_huge_pte(pte, vma, new, 0);
249 }
250#endif
251 flush_dcache_page(new);
252 set_pte_at(mm, addr, ptep, pte);
253
254 if (PageHuge(new)) {
255 if (PageAnon(new))
256 hugepage_add_anon_rmap(new, vma, addr);
257 else
258 page_dup_rmap(new, true);
259 } else if (PageAnon(new))
260 page_add_anon_rmap(new, vma, addr, false);
261 else
262 page_add_file_rmap(new, false);
263
264 if (vma->vm_flags & VM_LOCKED && !PageTransCompound(new))
265 mlock_vma_page(new);
266
267 /* No need to invalidate - it was non-present before */
268 update_mmu_cache(vma, addr, ptep);
269unlock:
270 pte_unmap_unlock(ptep, ptl);
271out:
272 return SWAP_AGAIN;
273}
274
275/*
276 * Get rid of all migration entries and replace them by
277 * references to the indicated page.
278 */
279void remove_migration_ptes(struct page *old, struct page *new, bool locked)
280{
281 struct rmap_walk_control rwc = {
282 .rmap_one = remove_migration_pte,
283 .arg = old,
284 };
285
286 if (locked)
287 rmap_walk_locked(new, &rwc);
288 else
289 rmap_walk(new, &rwc);
290}
291
292/*
293 * Something used the pte of a page under migration. We need to
294 * get to the page and wait until migration is finished.
295 * When we return from this function the fault will be retried.
296 */
297void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
298 spinlock_t *ptl)
299{
300 pte_t pte;
301 swp_entry_t entry;
302 struct page *page;
303
304 spin_lock(ptl);
305 pte = *ptep;
306 if (!is_swap_pte(pte))
307 goto out;
308
309 entry = pte_to_swp_entry(pte);
310 if (!is_migration_entry(entry))
311 goto out;
312
313 page = migration_entry_to_page(entry);
314
315 /*
316 * Once radix-tree replacement of page migration started, page_count
317 * *must* be zero. And, we don't want to call wait_on_page_locked()
318 * against a page without get_page().
319 * So, we use get_page_unless_zero(), here. Even failed, page fault
320 * will occur again.
321 */
322 if (!get_page_unless_zero(page))
323 goto out;
324 pte_unmap_unlock(ptep, ptl);
325 wait_on_page_locked(page);
326 put_page(page);
327 return;
328out:
329 pte_unmap_unlock(ptep, ptl);
330}
331
332void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
333 unsigned long address)
334{
335 spinlock_t *ptl = pte_lockptr(mm, pmd);
336 pte_t *ptep = pte_offset_map(pmd, address);
337 __migration_entry_wait(mm, ptep, ptl);
338}
339
340void migration_entry_wait_huge(struct vm_area_struct *vma,
341 struct mm_struct *mm, pte_t *pte)
342{
343 spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), mm, pte);
344 __migration_entry_wait(mm, pte, ptl);
345}
346
347#ifdef CONFIG_BLOCK
348/* Returns true if all buffers are successfully locked */
349static bool buffer_migrate_lock_buffers(struct buffer_head *head,
350 enum migrate_mode mode)
351{
352 struct buffer_head *bh = head;
353
354 /* Simple case, sync compaction */
355 if (mode != MIGRATE_ASYNC) {
356 do {
357 get_bh(bh);
358 lock_buffer(bh);
359 bh = bh->b_this_page;
360
361 } while (bh != head);
362
363 return true;
364 }
365
366 /* async case, we cannot block on lock_buffer so use trylock_buffer */
367 do {
368 get_bh(bh);
369 if (!trylock_buffer(bh)) {
370 /*
371 * We failed to lock the buffer and cannot stall in
372 * async migration. Release the taken locks
373 */
374 struct buffer_head *failed_bh = bh;
375 put_bh(failed_bh);
376 bh = head;
377 while (bh != failed_bh) {
378 unlock_buffer(bh);
379 put_bh(bh);
380 bh = bh->b_this_page;
381 }
382 return false;
383 }
384
385 bh = bh->b_this_page;
386 } while (bh != head);
387 return true;
388}
389#else
390static inline bool buffer_migrate_lock_buffers(struct buffer_head *head,
391 enum migrate_mode mode)
392{
393 return true;
394}
395#endif /* CONFIG_BLOCK */
396
397/*
398 * Replace the page in the mapping.
399 *
400 * The number of remaining references must be:
401 * 1 for anonymous pages without a mapping
402 * 2 for pages with a mapping
403 * 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
404 */
405int migrate_page_move_mapping(struct address_space *mapping,
406 struct page *newpage, struct page *page,
407 struct buffer_head *head, enum migrate_mode mode,
408 int extra_count)
409{
410 struct zone *oldzone, *newzone;
411 int dirty;
412 int expected_count = 1 + extra_count;
413 void **pslot;
414
415 if (!mapping) {
416 /* Anonymous page without mapping */
417 if (page_count(page) != expected_count)
418 return -EAGAIN;
419
420 /* No turning back from here */
421 newpage->index = page->index;
422 newpage->mapping = page->mapping;
423 if (PageSwapBacked(page))
424 __SetPageSwapBacked(newpage);
425
426 return MIGRATEPAGE_SUCCESS;
427 }
428
429 oldzone = page_zone(page);
430 newzone = page_zone(newpage);
431
432 spin_lock_irq(&mapping->tree_lock);
433
434 pslot = radix_tree_lookup_slot(&mapping->page_tree,
435 page_index(page));
436
437 expected_count += 1 + page_has_private(page);
438 if (page_count(page) != expected_count ||
439 radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {
440 spin_unlock_irq(&mapping->tree_lock);
441 return -EAGAIN;
442 }
443
444 if (!page_ref_freeze(page, expected_count)) {
445 spin_unlock_irq(&mapping->tree_lock);
446 return -EAGAIN;
447 }
448
449 /*
450 * In the async migration case of moving a page with buffers, lock the
451 * buffers using trylock before the mapping is moved. If the mapping
452 * was moved, we later failed to lock the buffers and could not move
453 * the mapping back due to an elevated page count, we would have to
454 * block waiting on other references to be dropped.
455 */
456 if (mode == MIGRATE_ASYNC && head &&
457 !buffer_migrate_lock_buffers(head, mode)) {
458 page_ref_unfreeze(page, expected_count);
459 spin_unlock_irq(&mapping->tree_lock);
460 return -EAGAIN;
461 }
462
463 /*
464 * Now we know that no one else is looking at the page:
465 * no turning back from here.
466 */
467 newpage->index = page->index;
468 newpage->mapping = page->mapping;
469 get_page(newpage); /* add cache reference */
470 if (PageSwapBacked(page)) {
471 __SetPageSwapBacked(newpage);
472 if (PageSwapCache(page)) {
473 SetPageSwapCache(newpage);
474 set_page_private(newpage, page_private(page));
475 }
476 } else {
477 VM_BUG_ON_PAGE(PageSwapCache(page), page);
478 }
479
480 /* Move dirty while page refs frozen and newpage not yet exposed */
481 dirty = PageDirty(page);
482 if (dirty) {
483 ClearPageDirty(page);
484 SetPageDirty(newpage);
485 }
486
487 radix_tree_replace_slot(&mapping->page_tree, pslot, newpage);
488
489 /*
490 * Drop cache reference from old page by unfreezing
491 * to one less reference.
492 * We know this isn't the last reference.
493 */
494 page_ref_unfreeze(page, expected_count - 1);
495
496 spin_unlock(&mapping->tree_lock);
497 /* Leave irq disabled to prevent preemption while updating stats */
498
499 /*
500 * If moved to a different zone then also account
501 * the page for that zone. Other VM counters will be
502 * taken care of when we establish references to the
503 * new page and drop references to the old page.
504 *
505 * Note that anonymous pages are accounted for
506 * via NR_FILE_PAGES and NR_ANON_MAPPED if they
507 * are mapped to swap space.
508 */
509 if (newzone != oldzone) {
510 __dec_node_state(oldzone->zone_pgdat, NR_FILE_PAGES);
511 __inc_node_state(newzone->zone_pgdat, NR_FILE_PAGES);
512 if (PageSwapBacked(page) && !PageSwapCache(page)) {
513 __dec_node_state(oldzone->zone_pgdat, NR_SHMEM);
514 __inc_node_state(newzone->zone_pgdat, NR_SHMEM);
515 }
516 if (dirty && mapping_cap_account_dirty(mapping)) {
517 __dec_node_state(oldzone->zone_pgdat, NR_FILE_DIRTY);
518 __dec_zone_state(oldzone, NR_ZONE_WRITE_PENDING);
519 __inc_node_state(newzone->zone_pgdat, NR_FILE_DIRTY);
520 __inc_zone_state(newzone, NR_ZONE_WRITE_PENDING);
521 }
522 }
523 local_irq_enable();
524
525 return MIGRATEPAGE_SUCCESS;
526}
527EXPORT_SYMBOL(migrate_page_move_mapping);
528
529/*
530 * The expected number of remaining references is the same as that
531 * of migrate_page_move_mapping().
532 */
533int migrate_huge_page_move_mapping(struct address_space *mapping,
534 struct page *newpage, struct page *page)
535{
536 int expected_count;
537 void **pslot;
538
539 spin_lock_irq(&mapping->tree_lock);
540
541 pslot = radix_tree_lookup_slot(&mapping->page_tree,
542 page_index(page));
543
544 expected_count = 2 + page_has_private(page);
545 if (page_count(page) != expected_count ||
546 radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {
547 spin_unlock_irq(&mapping->tree_lock);
548 return -EAGAIN;
549 }
550
551 if (!page_ref_freeze(page, expected_count)) {
552 spin_unlock_irq(&mapping->tree_lock);
553 return -EAGAIN;
554 }
555
556 newpage->index = page->index;
557 newpage->mapping = page->mapping;
558
559 get_page(newpage);
560
561 radix_tree_replace_slot(&mapping->page_tree, pslot, newpage);
562
563 page_ref_unfreeze(page, expected_count - 1);
564
565 spin_unlock_irq(&mapping->tree_lock);
566
567 return MIGRATEPAGE_SUCCESS;
568}
569
570/*
571 * Gigantic pages are so large that we do not guarantee that page++ pointer
572 * arithmetic will work across the entire page. We need something more
573 * specialized.
574 */
575static void __copy_gigantic_page(struct page *dst, struct page *src,
576 int nr_pages)
577{
578 int i;
579 struct page *dst_base = dst;
580 struct page *src_base = src;
581
582 for (i = 0; i < nr_pages; ) {
583 cond_resched();
584 copy_highpage(dst, src);
585
586 i++;
587 dst = mem_map_next(dst, dst_base, i);
588 src = mem_map_next(src, src_base, i);
589 }
590}
591
592static void copy_huge_page(struct page *dst, struct page *src)
593{
594 int i;
595 int nr_pages;
596
597 if (PageHuge(src)) {
598 /* hugetlbfs page */
599 struct hstate *h = page_hstate(src);
600 nr_pages = pages_per_huge_page(h);
601
602 if (unlikely(nr_pages > MAX_ORDER_NR_PAGES)) {
603 __copy_gigantic_page(dst, src, nr_pages);
604 return;
605 }
606 } else {
607 /* thp page */
608 BUG_ON(!PageTransHuge(src));
609 nr_pages = hpage_nr_pages(src);
610 }
611
612 for (i = 0; i < nr_pages; i++) {
613 cond_resched();
614 copy_highpage(dst + i, src + i);
615 }
616}
617
618/*
619 * Copy the page to its new location
620 */
621void migrate_page_copy(struct page *newpage, struct page *page)
622{
623 int cpupid;
624
625 if (PageHuge(page) || PageTransHuge(page))
626 copy_huge_page(newpage, page);
627 else
628 copy_highpage(newpage, page);
629
630 if (PageError(page))
631 SetPageError(newpage);
632 if (PageReferenced(page))
633 SetPageReferenced(newpage);
634 if (PageUptodate(page))
635 SetPageUptodate(newpage);
636 if (TestClearPageActive(page)) {
637 VM_BUG_ON_PAGE(PageUnevictable(page), page);
638 SetPageActive(newpage);
639 } else if (TestClearPageUnevictable(page))
640 SetPageUnevictable(newpage);
641 if (PageChecked(page))
642 SetPageChecked(newpage);
643 if (PageMappedToDisk(page))
644 SetPageMappedToDisk(newpage);
645
646 /* Move dirty on pages not done by migrate_page_move_mapping() */
647 if (PageDirty(page))
648 SetPageDirty(newpage);
649
650 if (page_is_young(page))
651 set_page_young(newpage);
652 if (page_is_idle(page))
653 set_page_idle(newpage);
654
655 /*
656 * Copy NUMA information to the new page, to prevent over-eager
657 * future migrations of this same page.
658 */
659 cpupid = page_cpupid_xchg_last(page, -1);
660 page_cpupid_xchg_last(newpage, cpupid);
661
662 ksm_migrate_page(newpage, page);
663 /*
664 * Please do not reorder this without considering how mm/ksm.c's
665 * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
666 */
667 if (PageSwapCache(page))
668 ClearPageSwapCache(page);
669 ClearPagePrivate(page);
670 set_page_private(page, 0);
671
672 /*
673 * If any waiters have accumulated on the new page then
674 * wake them up.
675 */
676 if (PageWriteback(newpage))
677 end_page_writeback(newpage);
678
679 copy_page_owner(page, newpage);
680
681 mem_cgroup_migrate(page, newpage);
682}
683EXPORT_SYMBOL(migrate_page_copy);
684
685/************************************************************
686 * Migration functions
687 ***********************************************************/
688
689/*
690 * Common logic to directly migrate a single LRU page suitable for
691 * pages that do not use PagePrivate/PagePrivate2.
692 *
693 * Pages are locked upon entry and exit.
694 */
695int migrate_page(struct address_space *mapping,
696 struct page *newpage, struct page *page,
697 enum migrate_mode mode)
698{
699 int rc;
700
701 BUG_ON(PageWriteback(page)); /* Writeback must be complete */
702
703 rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode, 0);
704
705 if (rc != MIGRATEPAGE_SUCCESS)
706 return rc;
707
708 migrate_page_copy(newpage, page);
709 return MIGRATEPAGE_SUCCESS;
710}
711EXPORT_SYMBOL(migrate_page);
712
713#ifdef CONFIG_BLOCK
714/*
715 * Migration function for pages with buffers. This function can only be used
716 * if the underlying filesystem guarantees that no other references to "page"
717 * exist.
718 */
719int buffer_migrate_page(struct address_space *mapping,
720 struct page *newpage, struct page *page, enum migrate_mode mode)
721{
722 struct buffer_head *bh, *head;
723 int rc;
724
725 if (!page_has_buffers(page))
726 return migrate_page(mapping, newpage, page, mode);
727
728 head = page_buffers(page);
729
730 rc = migrate_page_move_mapping(mapping, newpage, page, head, mode, 0);
731
732 if (rc != MIGRATEPAGE_SUCCESS)
733 return rc;
734
735 /*
736 * In the async case, migrate_page_move_mapping locked the buffers
737 * with an IRQ-safe spinlock held. In the sync case, the buffers
738 * need to be locked now
739 */
740 if (mode != MIGRATE_ASYNC)
741 BUG_ON(!buffer_migrate_lock_buffers(head, mode));
742
743 ClearPagePrivate(page);
744 set_page_private(newpage, page_private(page));
745 set_page_private(page, 0);
746 put_page(page);
747 get_page(newpage);
748
749 bh = head;
750 do {
751 set_bh_page(bh, newpage, bh_offset(bh));
752 bh = bh->b_this_page;
753
754 } while (bh != head);
755
756 SetPagePrivate(newpage);
757
758 migrate_page_copy(newpage, page);
759
760 bh = head;
761 do {
762 unlock_buffer(bh);
763 put_bh(bh);
764 bh = bh->b_this_page;
765
766 } while (bh != head);
767
768 return MIGRATEPAGE_SUCCESS;
769}
770EXPORT_SYMBOL(buffer_migrate_page);
771#endif
772
773/*
774 * Writeback a page to clean the dirty state
775 */
776static int writeout(struct address_space *mapping, struct page *page)
777{
778 struct writeback_control wbc = {
779 .sync_mode = WB_SYNC_NONE,
780 .nr_to_write = 1,
781 .range_start = 0,
782 .range_end = LLONG_MAX,
783 .for_reclaim = 1
784 };
785 int rc;
786
787 if (!mapping->a_ops->writepage)
788 /* No write method for the address space */
789 return -EINVAL;
790
791 if (!clear_page_dirty_for_io(page))
792 /* Someone else already triggered a write */
793 return -EAGAIN;
794
795 /*
796 * A dirty page may imply that the underlying filesystem has
797 * the page on some queue. So the page must be clean for
798 * migration. Writeout may mean we loose the lock and the
799 * page state is no longer what we checked for earlier.
800 * At this point we know that the migration attempt cannot
801 * be successful.
802 */
803 remove_migration_ptes(page, page, false);
804
805 rc = mapping->a_ops->writepage(page, &wbc);
806
807 if (rc != AOP_WRITEPAGE_ACTIVATE)
808 /* unlocked. Relock */
809 lock_page(page);
810
811 return (rc < 0) ? -EIO : -EAGAIN;
812}
813
814/*
815 * Default handling if a filesystem does not provide a migration function.
816 */
817static int fallback_migrate_page(struct address_space *mapping,
818 struct page *newpage, struct page *page, enum migrate_mode mode)
819{
820 if (PageDirty(page)) {
821 /* Only writeback pages in full synchronous migration */
822 if (mode != MIGRATE_SYNC)
823 return -EBUSY;
824 return writeout(mapping, page);
825 }
826
827 /*
828 * Buffers may be managed in a filesystem specific way.
829 * We must have no buffers or drop them.
830 */
831 if (page_has_private(page) &&
832 !try_to_release_page(page, GFP_KERNEL))
833 return -EAGAIN;
834
835 return migrate_page(mapping, newpage, page, mode);
836}
837
838/*
839 * Move a page to a newly allocated page
840 * The page is locked and all ptes have been successfully removed.
841 *
842 * The new page will have replaced the old page if this function
843 * is successful.
844 *
845 * Return value:
846 * < 0 - error code
847 * MIGRATEPAGE_SUCCESS - success
848 */
849static int move_to_new_page(struct page *newpage, struct page *page,
850 enum migrate_mode mode)
851{
852 struct address_space *mapping;
853 int rc = -EAGAIN;
854 bool is_lru = !__PageMovable(page);
855
856 VM_BUG_ON_PAGE(!PageLocked(page), page);
857 VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
858
859 mapping = page_mapping(page);
860
861 if (likely(is_lru)) {
862 if (!mapping)
863 rc = migrate_page(mapping, newpage, page, mode);
864 else if (mapping->a_ops->migratepage)
865 /*
866 * Most pages have a mapping and most filesystems
867 * provide a migratepage callback. Anonymous pages
868 * are part of swap space which also has its own
869 * migratepage callback. This is the most common path
870 * for page migration.
871 */
872 rc = mapping->a_ops->migratepage(mapping, newpage,
873 page, mode);
874 else
875 rc = fallback_migrate_page(mapping, newpage,
876 page, mode);
877 } else {
878 /*
879 * In case of non-lru page, it could be released after
880 * isolation step. In that case, we shouldn't try migration.
881 */
882 VM_BUG_ON_PAGE(!PageIsolated(page), page);
883 if (!PageMovable(page)) {
884 rc = MIGRATEPAGE_SUCCESS;
885 __ClearPageIsolated(page);
886 goto out;
887 }
888
889 rc = mapping->a_ops->migratepage(mapping, newpage,
890 page, mode);
891 WARN_ON_ONCE(rc == MIGRATEPAGE_SUCCESS &&
892 !PageIsolated(page));
893 }
894
895 /*
896 * When successful, old pagecache page->mapping must be cleared before
897 * page is freed; but stats require that PageAnon be left as PageAnon.
898 */
899 if (rc == MIGRATEPAGE_SUCCESS) {
900 if (__PageMovable(page)) {
901 VM_BUG_ON_PAGE(!PageIsolated(page), page);
902
903 /*
904 * We clear PG_movable under page_lock so any compactor
905 * cannot try to migrate this page.
906 */
907 __ClearPageIsolated(page);
908 }
909
910 /*
911 * Anonymous and movable page->mapping will be cleard by
912 * free_pages_prepare so don't reset it here for keeping
913 * the type to work PageAnon, for example.
914 */
915 if (!PageMappingFlags(page))
916 page->mapping = NULL;
917 }
918out:
919 return rc;
920}
921
922static int __unmap_and_move(struct page *page, struct page *newpage,
923 int force, enum migrate_mode mode)
924{
925 int rc = -EAGAIN;
926 int page_was_mapped = 0;
927 struct anon_vma *anon_vma = NULL;
928 bool is_lru = !__PageMovable(page);
929
930 if (!trylock_page(page)) {
931 if (!force || mode == MIGRATE_ASYNC)
932 goto out;
933
934 /*
935 * It's not safe for direct compaction to call lock_page.
936 * For example, during page readahead pages are added locked
937 * to the LRU. Later, when the IO completes the pages are
938 * marked uptodate and unlocked. However, the queueing
939 * could be merging multiple pages for one bio (e.g.
940 * mpage_readpages). If an allocation happens for the
941 * second or third page, the process can end up locking
942 * the same page twice and deadlocking. Rather than
943 * trying to be clever about what pages can be locked,
944 * avoid the use of lock_page for direct compaction
945 * altogether.
946 */
947 if (current->flags & PF_MEMALLOC)
948 goto out;
949
950 lock_page(page);
951 }
952
953 if (PageWriteback(page)) {
954 /*
955 * Only in the case of a full synchronous migration is it
956 * necessary to wait for PageWriteback. In the async case,
957 * the retry loop is too short and in the sync-light case,
958 * the overhead of stalling is too much
959 */
960 if (mode != MIGRATE_SYNC) {
961 rc = -EBUSY;
962 goto out_unlock;
963 }
964 if (!force)
965 goto out_unlock;
966 wait_on_page_writeback(page);
967 }
968
969 /*
970 * By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
971 * we cannot notice that anon_vma is freed while we migrates a page.
972 * This get_anon_vma() delays freeing anon_vma pointer until the end
973 * of migration. File cache pages are no problem because of page_lock()
974 * File Caches may use write_page() or lock_page() in migration, then,
975 * just care Anon page here.
976 *
977 * Only page_get_anon_vma() understands the subtleties of
978 * getting a hold on an anon_vma from outside one of its mms.
979 * But if we cannot get anon_vma, then we won't need it anyway,
980 * because that implies that the anon page is no longer mapped
981 * (and cannot be remapped so long as we hold the page lock).
982 */
983 if (PageAnon(page) && !PageKsm(page))
984 anon_vma = page_get_anon_vma(page);
985
986 /*
987 * Block others from accessing the new page when we get around to
988 * establishing additional references. We are usually the only one
989 * holding a reference to newpage at this point. We used to have a BUG
990 * here if trylock_page(newpage) fails, but would like to allow for
991 * cases where there might be a race with the previous use of newpage.
992 * This is much like races on refcount of oldpage: just don't BUG().
993 */
994 if (unlikely(!trylock_page(newpage)))
995 goto out_unlock;
996
997 if (unlikely(!is_lru)) {
998 rc = move_to_new_page(newpage, page, mode);
999 goto out_unlock_both;
1000 }
1001
1002 /*
1003 * Corner case handling:
1004 * 1. When a new swap-cache page is read into, it is added to the LRU
1005 * and treated as swapcache but it has no rmap yet.
1006 * Calling try_to_unmap() against a page->mapping==NULL page will
1007 * trigger a BUG. So handle it here.
1008 * 2. An orphaned page (see truncate_complete_page) might have
1009 * fs-private metadata. The page can be picked up due to memory
1010 * offlining. Everywhere else except page reclaim, the page is
1011 * invisible to the vm, so the page can not be migrated. So try to
1012 * free the metadata, so the page can be freed.
1013 */
1014 if (!page->mapping) {
1015 VM_BUG_ON_PAGE(PageAnon(page), page);
1016 if (page_has_private(page)) {
1017 try_to_free_buffers(page);
1018 goto out_unlock_both;
1019 }
1020 } else if (page_mapped(page)) {
1021 /* Establish migration ptes */
1022 VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma,
1023 page);
1024 try_to_unmap(page,
1025 TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
1026 page_was_mapped = 1;
1027 }
1028
1029 if (!page_mapped(page))
1030 rc = move_to_new_page(newpage, page, mode);
1031
1032 if (page_was_mapped)
1033 remove_migration_ptes(page,
1034 rc == MIGRATEPAGE_SUCCESS ? newpage : page, false);
1035
1036out_unlock_both:
1037 unlock_page(newpage);
1038out_unlock:
1039 /* Drop an anon_vma reference if we took one */
1040 if (anon_vma)
1041 put_anon_vma(anon_vma);
1042 unlock_page(page);
1043out:
1044 /*
1045 * If migration is successful, decrease refcount of the newpage
1046 * which will not free the page because new page owner increased
1047 * refcounter. As well, if it is LRU page, add the page to LRU
1048 * list in here.
1049 */
1050 if (rc == MIGRATEPAGE_SUCCESS) {
1051 if (unlikely(__PageMovable(newpage)))
1052 put_page(newpage);
1053 else
1054 putback_lru_page(newpage);
1055 }
1056
1057 return rc;
1058}
1059
1060/*
1061 * gcc 4.7 and 4.8 on arm get an ICEs when inlining unmap_and_move(). Work
1062 * around it.
1063 */
1064#if (GCC_VERSION >= 40700 && GCC_VERSION < 40900) && defined(CONFIG_ARM)
1065#define ICE_noinline noinline
1066#else
1067#define ICE_noinline
1068#endif
1069
1070/*
1071 * Obtain the lock on page, remove all ptes and migrate the page
1072 * to the newly allocated page in newpage.
1073 */
1074static ICE_noinline int unmap_and_move(new_page_t get_new_page,
1075 free_page_t put_new_page,
1076 unsigned long private, struct page *page,
1077 int force, enum migrate_mode mode,
1078 enum migrate_reason reason)
1079{
1080 int rc = MIGRATEPAGE_SUCCESS;
1081 int *result = NULL;
1082 struct page *newpage;
1083
1084 newpage = get_new_page(page, private, &result);
1085 if (!newpage)
1086 return -ENOMEM;
1087
1088 if (page_count(page) == 1) {
1089 /* page was freed from under us. So we are done. */
1090 ClearPageActive(page);
1091 ClearPageUnevictable(page);
1092 if (unlikely(__PageMovable(page))) {
1093 lock_page(page);
1094 if (!PageMovable(page))
1095 __ClearPageIsolated(page);
1096 unlock_page(page);
1097 }
1098 if (put_new_page)
1099 put_new_page(newpage, private);
1100 else
1101 put_page(newpage);
1102 goto out;
1103 }
1104
1105 if (unlikely(PageTransHuge(page))) {
1106 lock_page(page);
1107 rc = split_huge_page(page);
1108 unlock_page(page);
1109 if (rc)
1110 goto out;
1111 }
1112
1113 rc = __unmap_and_move(page, newpage, force, mode);
1114 if (rc == MIGRATEPAGE_SUCCESS)
1115 set_page_owner_migrate_reason(newpage, reason);
1116
1117out:
1118 if (rc != -EAGAIN) {
1119 /*
1120 * A page that has been migrated has all references
1121 * removed and will be freed. A page that has not been
1122 * migrated will have kepts its references and be
1123 * restored.
1124 */
1125 list_del(&page->lru);
1126
1127 /*
1128 * Compaction can migrate also non-LRU pages which are
1129 * not accounted to NR_ISOLATED_*. They can be recognized
1130 * as __PageMovable
1131 */
1132 if (likely(!__PageMovable(page)))
1133 dec_node_page_state(page, NR_ISOLATED_ANON +
1134 page_is_file_cache(page));
1135 }
1136
1137 /*
1138 * If migration is successful, releases reference grabbed during
1139 * isolation. Otherwise, restore the page to right list unless
1140 * we want to retry.
1141 */
1142 if (rc == MIGRATEPAGE_SUCCESS) {
1143 put_page(page);
1144 if (reason == MR_MEMORY_FAILURE) {
1145 /*
1146 * Set PG_HWPoison on just freed page
1147 * intentionally. Although it's rather weird,
1148 * it's how HWPoison flag works at the moment.
1149 */
1150 if (!test_set_page_hwpoison(page))
1151 num_poisoned_pages_inc();
1152 }
1153 } else {
1154 if (rc != -EAGAIN) {
1155 if (likely(!__PageMovable(page))) {
1156 putback_lru_page(page);
1157 goto put_new;
1158 }
1159
1160 lock_page(page);
1161 if (PageMovable(page))
1162 putback_movable_page(page);
1163 else
1164 __ClearPageIsolated(page);
1165 unlock_page(page);
1166 put_page(page);
1167 }
1168put_new:
1169 if (put_new_page)
1170 put_new_page(newpage, private);
1171 else
1172 put_page(newpage);
1173 }
1174
1175 if (result) {
1176 if (rc)
1177 *result = rc;
1178 else
1179 *result = page_to_nid(newpage);
1180 }
1181 return rc;
1182}
1183
1184/*
1185 * Counterpart of unmap_and_move_page() for hugepage migration.
1186 *
1187 * This function doesn't wait the completion of hugepage I/O
1188 * because there is no race between I/O and migration for hugepage.
1189 * Note that currently hugepage I/O occurs only in direct I/O
1190 * where no lock is held and PG_writeback is irrelevant,
1191 * and writeback status of all subpages are counted in the reference
1192 * count of the head page (i.e. if all subpages of a 2MB hugepage are
1193 * under direct I/O, the reference of the head page is 512 and a bit more.)
1194 * This means that when we try to migrate hugepage whose subpages are
1195 * doing direct I/O, some references remain after try_to_unmap() and
1196 * hugepage migration fails without data corruption.
1197 *
1198 * There is also no race when direct I/O is issued on the page under migration,
1199 * because then pte is replaced with migration swap entry and direct I/O code
1200 * will wait in the page fault for migration to complete.
1201 */
1202static int unmap_and_move_huge_page(new_page_t get_new_page,
1203 free_page_t put_new_page, unsigned long private,
1204 struct page *hpage, int force,
1205 enum migrate_mode mode, int reason)
1206{
1207 int rc = -EAGAIN;
1208 int *result = NULL;
1209 int page_was_mapped = 0;
1210 struct page *new_hpage;
1211 struct anon_vma *anon_vma = NULL;
1212
1213 /*
1214 * Movability of hugepages depends on architectures and hugepage size.
1215 * This check is necessary because some callers of hugepage migration
1216 * like soft offline and memory hotremove don't walk through page
1217 * tables or check whether the hugepage is pmd-based or not before
1218 * kicking migration.
1219 */
1220 if (!hugepage_migration_supported(page_hstate(hpage))) {
1221 putback_active_hugepage(hpage);
1222 return -ENOSYS;
1223 }
1224
1225 new_hpage = get_new_page(hpage, private, &result);
1226 if (!new_hpage)
1227 return -ENOMEM;
1228
1229 if (!trylock_page(hpage)) {
1230 if (!force || mode != MIGRATE_SYNC)
1231 goto out;
1232 lock_page(hpage);
1233 }
1234
1235 if (PageAnon(hpage))
1236 anon_vma = page_get_anon_vma(hpage);
1237
1238 if (unlikely(!trylock_page(new_hpage)))
1239 goto put_anon;
1240
1241 if (page_mapped(hpage)) {
1242 try_to_unmap(hpage,
1243 TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
1244 page_was_mapped = 1;
1245 }
1246
1247 if (!page_mapped(hpage))
1248 rc = move_to_new_page(new_hpage, hpage, mode);
1249
1250 if (page_was_mapped)
1251 remove_migration_ptes(hpage,
1252 rc == MIGRATEPAGE_SUCCESS ? new_hpage : hpage, false);
1253
1254 unlock_page(new_hpage);
1255
1256put_anon:
1257 if (anon_vma)
1258 put_anon_vma(anon_vma);
1259
1260 if (rc == MIGRATEPAGE_SUCCESS) {
1261 hugetlb_cgroup_migrate(hpage, new_hpage);
1262 put_new_page = NULL;
1263 set_page_owner_migrate_reason(new_hpage, reason);
1264 }
1265
1266 unlock_page(hpage);
1267out:
1268 if (rc != -EAGAIN)
1269 putback_active_hugepage(hpage);
1270
1271 /*
1272 * If migration was not successful and there's a freeing callback, use
1273 * it. Otherwise, put_page() will drop the reference grabbed during
1274 * isolation.
1275 */
1276 if (put_new_page)
1277 put_new_page(new_hpage, private);
1278 else
1279 putback_active_hugepage(new_hpage);
1280
1281 if (result) {
1282 if (rc)
1283 *result = rc;
1284 else
1285 *result = page_to_nid(new_hpage);
1286 }
1287 return rc;
1288}
1289
1290/*
1291 * migrate_pages - migrate the pages specified in a list, to the free pages
1292 * supplied as the target for the page migration
1293 *
1294 * @from: The list of pages to be migrated.
1295 * @get_new_page: The function used to allocate free pages to be used
1296 * as the target of the page migration.
1297 * @put_new_page: The function used to free target pages if migration
1298 * fails, or NULL if no special handling is necessary.
1299 * @private: Private data to be passed on to get_new_page()
1300 * @mode: The migration mode that specifies the constraints for
1301 * page migration, if any.
1302 * @reason: The reason for page migration.
1303 *
1304 * The function returns after 10 attempts or if no pages are movable any more
1305 * because the list has become empty or no retryable pages exist any more.
1306 * The caller should call putback_movable_pages() to return pages to the LRU
1307 * or free list only if ret != 0.
1308 *
1309 * Returns the number of pages that were not migrated, or an error code.
1310 */
1311int migrate_pages(struct list_head *from, new_page_t get_new_page,
1312 free_page_t put_new_page, unsigned long private,
1313 enum migrate_mode mode, int reason)
1314{
1315 int retry = 1;
1316 int nr_failed = 0;
1317 int nr_succeeded = 0;
1318 int pass = 0;
1319 struct page *page;
1320 struct page *page2;
1321 int swapwrite = current->flags & PF_SWAPWRITE;
1322 int rc;
1323
1324 if (!swapwrite)
1325 current->flags |= PF_SWAPWRITE;
1326
1327 for(pass = 0; pass < 10 && retry; pass++) {
1328 retry = 0;
1329
1330 list_for_each_entry_safe(page, page2, from, lru) {
1331 cond_resched();
1332
1333 if (PageHuge(page))
1334 rc = unmap_and_move_huge_page(get_new_page,
1335 put_new_page, private, page,
1336 pass > 2, mode, reason);
1337 else
1338 rc = unmap_and_move(get_new_page, put_new_page,
1339 private, page, pass > 2, mode,
1340 reason);
1341
1342 switch(rc) {
1343 case -ENOMEM:
1344 nr_failed++;
1345 goto out;
1346 case -EAGAIN:
1347 retry++;
1348 break;
1349 case MIGRATEPAGE_SUCCESS:
1350 nr_succeeded++;
1351 break;
1352 default:
1353 /*
1354 * Permanent failure (-EBUSY, -ENOSYS, etc.):
1355 * unlike -EAGAIN case, the failed page is
1356 * removed from migration page list and not
1357 * retried in the next outer loop.
1358 */
1359 nr_failed++;
1360 break;
1361 }
1362 }
1363 }
1364 nr_failed += retry;
1365 rc = nr_failed;
1366out:
1367 if (nr_succeeded)
1368 count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
1369 if (nr_failed)
1370 count_vm_events(PGMIGRATE_FAIL, nr_failed);
1371 trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason);
1372
1373 if (!swapwrite)
1374 current->flags &= ~PF_SWAPWRITE;
1375
1376 return rc;
1377}
1378
1379#ifdef CONFIG_NUMA
1380/*
1381 * Move a list of individual pages
1382 */
1383struct page_to_node {
1384 unsigned long addr;
1385 struct page *page;
1386 int node;
1387 int status;
1388};
1389
1390static struct page *new_page_node(struct page *p, unsigned long private,
1391 int **result)
1392{
1393 struct page_to_node *pm = (struct page_to_node *)private;
1394
1395 while (pm->node != MAX_NUMNODES && pm->page != p)
1396 pm++;
1397
1398 if (pm->node == MAX_NUMNODES)
1399 return NULL;
1400
1401 *result = &pm->status;
1402
1403 if (PageHuge(p))
1404 return alloc_huge_page_node(page_hstate(compound_head(p)),
1405 pm->node);
1406 else
1407 return __alloc_pages_node(pm->node,
1408 GFP_HIGHUSER_MOVABLE | __GFP_THISNODE, 0);
1409}
1410
1411/*
1412 * Move a set of pages as indicated in the pm array. The addr
1413 * field must be set to the virtual address of the page to be moved
1414 * and the node number must contain a valid target node.
1415 * The pm array ends with node = MAX_NUMNODES.
1416 */
1417static int do_move_page_to_node_array(struct mm_struct *mm,
1418 struct page_to_node *pm,
1419 int migrate_all)
1420{
1421 int err;
1422 struct page_to_node *pp;
1423 LIST_HEAD(pagelist);
1424
1425 down_read(&mm->mmap_sem);
1426
1427 /*
1428 * Build a list of pages to migrate
1429 */
1430 for (pp = pm; pp->node != MAX_NUMNODES; pp++) {
1431 struct vm_area_struct *vma;
1432 struct page *page;
1433
1434 err = -EFAULT;
1435 vma = find_vma(mm, pp->addr);
1436 if (!vma || pp->addr < vma->vm_start || !vma_migratable(vma))
1437 goto set_status;
1438
1439 /* FOLL_DUMP to ignore special (like zero) pages */
1440 page = follow_page(vma, pp->addr,
1441 FOLL_GET | FOLL_SPLIT | FOLL_DUMP);
1442
1443 err = PTR_ERR(page);
1444 if (IS_ERR(page))
1445 goto set_status;
1446
1447 err = -ENOENT;
1448 if (!page)
1449 goto set_status;
1450
1451 pp->page = page;
1452 err = page_to_nid(page);
1453
1454 if (err == pp->node)
1455 /*
1456 * Node already in the right place
1457 */
1458 goto put_and_set;
1459
1460 err = -EACCES;
1461 if (page_mapcount(page) > 1 &&
1462 !migrate_all)
1463 goto put_and_set;
1464
1465 if (PageHuge(page)) {
1466 if (PageHead(page))
1467 isolate_huge_page(page, &pagelist);
1468 goto put_and_set;
1469 }
1470
1471 err = isolate_lru_page(page);
1472 if (!err) {
1473 list_add_tail(&page->lru, &pagelist);
1474 inc_node_page_state(page, NR_ISOLATED_ANON +
1475 page_is_file_cache(page));
1476 }
1477put_and_set:
1478 /*
1479 * Either remove the duplicate refcount from
1480 * isolate_lru_page() or drop the page ref if it was
1481 * not isolated.
1482 */
1483 put_page(page);
1484set_status:
1485 pp->status = err;
1486 }
1487
1488 err = 0;
1489 if (!list_empty(&pagelist)) {
1490 err = migrate_pages(&pagelist, new_page_node, NULL,
1491 (unsigned long)pm, MIGRATE_SYNC, MR_SYSCALL);
1492 if (err)
1493 putback_movable_pages(&pagelist);
1494 }
1495
1496 up_read(&mm->mmap_sem);
1497 return err;
1498}
1499
1500/*
1501 * Migrate an array of page address onto an array of nodes and fill
1502 * the corresponding array of status.
1503 */
1504static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
1505 unsigned long nr_pages,
1506 const void __user * __user *pages,
1507 const int __user *nodes,
1508 int __user *status, int flags)
1509{
1510 struct page_to_node *pm;
1511 unsigned long chunk_nr_pages;
1512 unsigned long chunk_start;
1513 int err;
1514
1515 err = -ENOMEM;
1516 pm = (struct page_to_node *)__get_free_page(GFP_KERNEL);
1517 if (!pm)
1518 goto out;
1519
1520 migrate_prep();
1521
1522 /*
1523 * Store a chunk of page_to_node array in a page,
1524 * but keep the last one as a marker
1525 */
1526 chunk_nr_pages = (PAGE_SIZE / sizeof(struct page_to_node)) - 1;
1527
1528 for (chunk_start = 0;
1529 chunk_start < nr_pages;
1530 chunk_start += chunk_nr_pages) {
1531 int j;
1532
1533 if (chunk_start + chunk_nr_pages > nr_pages)
1534 chunk_nr_pages = nr_pages - chunk_start;
1535
1536 /* fill the chunk pm with addrs and nodes from user-space */
1537 for (j = 0; j < chunk_nr_pages; j++) {
1538 const void __user *p;
1539 int node;
1540
1541 err = -EFAULT;
1542 if (get_user(p, pages + j + chunk_start))
1543 goto out_pm;
1544 pm[j].addr = (unsigned long) p;
1545
1546 if (get_user(node, nodes + j + chunk_start))
1547 goto out_pm;
1548
1549 err = -ENODEV;
1550 if (node < 0 || node >= MAX_NUMNODES)
1551 goto out_pm;
1552
1553 if (!node_state(node, N_MEMORY))
1554 goto out_pm;
1555
1556 err = -EACCES;
1557 if (!node_isset(node, task_nodes))
1558 goto out_pm;
1559
1560 pm[j].node = node;
1561 }
1562
1563 /* End marker for this chunk */
1564 pm[chunk_nr_pages].node = MAX_NUMNODES;
1565
1566 /* Migrate this chunk */
1567 err = do_move_page_to_node_array(mm, pm,
1568 flags & MPOL_MF_MOVE_ALL);
1569 if (err < 0)
1570 goto out_pm;
1571
1572 /* Return status information */
1573 for (j = 0; j < chunk_nr_pages; j++)
1574 if (put_user(pm[j].status, status + j + chunk_start)) {
1575 err = -EFAULT;
1576 goto out_pm;
1577 }
1578 }
1579 err = 0;
1580
1581out_pm:
1582 free_page((unsigned long)pm);
1583out:
1584 return err;
1585}
1586
1587/*
1588 * Determine the nodes of an array of pages and store it in an array of status.
1589 */
1590static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
1591 const void __user **pages, int *status)
1592{
1593 unsigned long i;
1594
1595 down_read(&mm->mmap_sem);
1596
1597 for (i = 0; i < nr_pages; i++) {
1598 unsigned long addr = (unsigned long)(*pages);
1599 struct vm_area_struct *vma;
1600 struct page *page;
1601 int err = -EFAULT;
1602
1603 vma = find_vma(mm, addr);
1604 if (!vma || addr < vma->vm_start)
1605 goto set_status;
1606
1607 /* FOLL_DUMP to ignore special (like zero) pages */
1608 page = follow_page(vma, addr, FOLL_DUMP);
1609
1610 err = PTR_ERR(page);
1611 if (IS_ERR(page))
1612 goto set_status;
1613
1614 err = page ? page_to_nid(page) : -ENOENT;
1615set_status:
1616 *status = err;
1617
1618 pages++;
1619 status++;
1620 }
1621
1622 up_read(&mm->mmap_sem);
1623}
1624
1625/*
1626 * Determine the nodes of a user array of pages and store it in
1627 * a user array of status.
1628 */
1629static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
1630 const void __user * __user *pages,
1631 int __user *status)
1632{
1633#define DO_PAGES_STAT_CHUNK_NR 16
1634 const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
1635 int chunk_status[DO_PAGES_STAT_CHUNK_NR];
1636
1637 while (nr_pages) {
1638 unsigned long chunk_nr;
1639
1640 chunk_nr = nr_pages;
1641 if (chunk_nr > DO_PAGES_STAT_CHUNK_NR)
1642 chunk_nr = DO_PAGES_STAT_CHUNK_NR;
1643
1644 if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages)))
1645 break;
1646
1647 do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
1648
1649 if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
1650 break;
1651
1652 pages += chunk_nr;
1653 status += chunk_nr;
1654 nr_pages -= chunk_nr;
1655 }
1656 return nr_pages ? -EFAULT : 0;
1657}
1658
1659/*
1660 * Move a list of pages in the address space of the currently executing
1661 * process.
1662 */
1663SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
1664 const void __user * __user *, pages,
1665 const int __user *, nodes,
1666 int __user *, status, int, flags)
1667{
1668 const struct cred *cred = current_cred(), *tcred;
1669 struct task_struct *task;
1670 struct mm_struct *mm;
1671 int err;
1672 nodemask_t task_nodes;
1673
1674 /* Check flags */
1675 if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
1676 return -EINVAL;
1677
1678 if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
1679 return -EPERM;
1680
1681 /* Find the mm_struct */
1682 rcu_read_lock();
1683 task = pid ? find_task_by_vpid(pid) : current;
1684 if (!task) {
1685 rcu_read_unlock();
1686 return -ESRCH;
1687 }
1688 get_task_struct(task);
1689
1690 /*
1691 * Check if this process has the right to modify the specified
1692 * process. The right exists if the process has administrative
1693 * capabilities, superuser privileges or the same
1694 * userid as the target process.
1695 */
1696 tcred = __task_cred(task);
1697 if (!uid_eq(cred->euid, tcred->suid) && !uid_eq(cred->euid, tcred->uid) &&
1698 !uid_eq(cred->uid, tcred->suid) && !uid_eq(cred->uid, tcred->uid) &&
1699 !capable(CAP_SYS_NICE)) {
1700 rcu_read_unlock();
1701 err = -EPERM;
1702 goto out;
1703 }
1704 rcu_read_unlock();
1705
1706 err = security_task_movememory(task);
1707 if (err)
1708 goto out;
1709
1710 task_nodes = cpuset_mems_allowed(task);
1711 mm = get_task_mm(task);
1712 put_task_struct(task);
1713
1714 if (!mm)
1715 return -EINVAL;
1716
1717 if (nodes)
1718 err = do_pages_move(mm, task_nodes, nr_pages, pages,
1719 nodes, status, flags);
1720 else
1721 err = do_pages_stat(mm, nr_pages, pages, status);
1722
1723 mmput(mm);
1724 return err;
1725
1726out:
1727 put_task_struct(task);
1728 return err;
1729}
1730
1731#ifdef CONFIG_NUMA_BALANCING
1732/*
1733 * Returns true if this is a safe migration target node for misplaced NUMA
1734 * pages. Currently it only checks the watermarks which crude
1735 */
1736static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
1737 unsigned long nr_migrate_pages)
1738{
1739 int z;
1740
1741 if (!pgdat_reclaimable(pgdat))
1742 return false;
1743
1744 for (z = pgdat->nr_zones - 1; z >= 0; z--) {
1745 struct zone *zone = pgdat->node_zones + z;
1746
1747 if (!populated_zone(zone))
1748 continue;
1749
1750 /* Avoid waking kswapd by allocating pages_to_migrate pages. */
1751 if (!zone_watermark_ok(zone, 0,
1752 high_wmark_pages(zone) +
1753 nr_migrate_pages,
1754 0, 0))
1755 continue;
1756 return true;
1757 }
1758 return false;
1759}
1760
1761static struct page *alloc_misplaced_dst_page(struct page *page,
1762 unsigned long data,
1763 int **result)
1764{
1765 int nid = (int) data;
1766 struct page *newpage;
1767
1768 newpage = __alloc_pages_node(nid,
1769 (GFP_HIGHUSER_MOVABLE |
1770 __GFP_THISNODE | __GFP_NOMEMALLOC |
1771 __GFP_NORETRY | __GFP_NOWARN) &
1772 ~__GFP_RECLAIM, 0);
1773
1774 return newpage;
1775}
1776
1777/*
1778 * page migration rate limiting control.
1779 * Do not migrate more than @pages_to_migrate in a @migrate_interval_millisecs
1780 * window of time. Default here says do not migrate more than 1280M per second.
1781 */
1782static unsigned int migrate_interval_millisecs __read_mostly = 100;
1783static unsigned int ratelimit_pages __read_mostly = 128 << (20 - PAGE_SHIFT);
1784
1785/* Returns true if the node is migrate rate-limited after the update */
1786static bool numamigrate_update_ratelimit(pg_data_t *pgdat,
1787 unsigned long nr_pages)
1788{
1789 /*
1790 * Rate-limit the amount of data that is being migrated to a node.
1791 * Optimal placement is no good if the memory bus is saturated and
1792 * all the time is being spent migrating!
1793 */
1794 if (time_after(jiffies, pgdat->numabalancing_migrate_next_window)) {
1795 spin_lock(&pgdat->numabalancing_migrate_lock);
1796 pgdat->numabalancing_migrate_nr_pages = 0;
1797 pgdat->numabalancing_migrate_next_window = jiffies +
1798 msecs_to_jiffies(migrate_interval_millisecs);
1799 spin_unlock(&pgdat->numabalancing_migrate_lock);
1800 }
1801 if (pgdat->numabalancing_migrate_nr_pages > ratelimit_pages) {
1802 trace_mm_numa_migrate_ratelimit(current, pgdat->node_id,
1803 nr_pages);
1804 return true;
1805 }
1806
1807 /*
1808 * This is an unlocked non-atomic update so errors are possible.
1809 * The consequences are failing to migrate when we potentiall should
1810 * have which is not severe enough to warrant locking. If it is ever
1811 * a problem, it can be converted to a per-cpu counter.
1812 */
1813 pgdat->numabalancing_migrate_nr_pages += nr_pages;
1814 return false;
1815}
1816
1817static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
1818{
1819 int page_lru;
1820
1821 VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page);
1822
1823 /* Avoid migrating to a node that is nearly full */
1824 if (!migrate_balanced_pgdat(pgdat, 1UL << compound_order(page)))
1825 return 0;
1826
1827 if (isolate_lru_page(page))
1828 return 0;
1829
1830 /*
1831 * migrate_misplaced_transhuge_page() skips page migration's usual
1832 * check on page_count(), so we must do it here, now that the page
1833 * has been isolated: a GUP pin, or any other pin, prevents migration.
1834 * The expected page count is 3: 1 for page's mapcount and 1 for the
1835 * caller's pin and 1 for the reference taken by isolate_lru_page().
1836 */
1837 if (PageTransHuge(page) && page_count(page) != 3) {
1838 putback_lru_page(page);
1839 return 0;
1840 }
1841
1842 page_lru = page_is_file_cache(page);
1843 mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_lru,
1844 hpage_nr_pages(page));
1845
1846 /*
1847 * Isolating the page has taken another reference, so the
1848 * caller's reference can be safely dropped without the page
1849 * disappearing underneath us during migration.
1850 */
1851 put_page(page);
1852 return 1;
1853}
1854
1855bool pmd_trans_migrating(pmd_t pmd)
1856{
1857 struct page *page = pmd_page(pmd);
1858 return PageLocked(page);
1859}
1860
1861/*
1862 * Attempt to migrate a misplaced page to the specified destination
1863 * node. Caller is expected to have an elevated reference count on
1864 * the page that will be dropped by this function before returning.
1865 */
1866int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
1867 int node)
1868{
1869 pg_data_t *pgdat = NODE_DATA(node);
1870 int isolated;
1871 int nr_remaining;
1872 LIST_HEAD(migratepages);
1873
1874 /*
1875 * Don't migrate file pages that are mapped in multiple processes
1876 * with execute permissions as they are probably shared libraries.
1877 */
1878 if (page_mapcount(page) != 1 && page_is_file_cache(page) &&
1879 (vma->vm_flags & VM_EXEC))
1880 goto out;
1881
1882 /*
1883 * Rate-limit the amount of data that is being migrated to a node.
1884 * Optimal placement is no good if the memory bus is saturated and
1885 * all the time is being spent migrating!
1886 */
1887 if (numamigrate_update_ratelimit(pgdat, 1))
1888 goto out;
1889
1890 isolated = numamigrate_isolate_page(pgdat, page);
1891 if (!isolated)
1892 goto out;
1893
1894 list_add(&page->lru, &migratepages);
1895 nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page,
1896 NULL, node, MIGRATE_ASYNC,
1897 MR_NUMA_MISPLACED);
1898 if (nr_remaining) {
1899 if (!list_empty(&migratepages)) {
1900 list_del(&page->lru);
1901 dec_node_page_state(page, NR_ISOLATED_ANON +
1902 page_is_file_cache(page));
1903 putback_lru_page(page);
1904 }
1905 isolated = 0;
1906 } else
1907 count_vm_numa_event(NUMA_PAGE_MIGRATE);
1908 BUG_ON(!list_empty(&migratepages));
1909 return isolated;
1910
1911out:
1912 put_page(page);
1913 return 0;
1914}
1915#endif /* CONFIG_NUMA_BALANCING */
1916
1917#if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
1918/*
1919 * Migrates a THP to a given target node. page must be locked and is unlocked
1920 * before returning.
1921 */
1922int migrate_misplaced_transhuge_page(struct mm_struct *mm,
1923 struct vm_area_struct *vma,
1924 pmd_t *pmd, pmd_t entry,
1925 unsigned long address,
1926 struct page *page, int node)
1927{
1928 spinlock_t *ptl;
1929 pg_data_t *pgdat = NODE_DATA(node);
1930 int isolated = 0;
1931 struct page *new_page = NULL;
1932 int page_lru = page_is_file_cache(page);
1933 unsigned long mmun_start = address & HPAGE_PMD_MASK;
1934 unsigned long mmun_end = mmun_start + HPAGE_PMD_SIZE;
1935 pmd_t orig_entry;
1936
1937 /*
1938 * Rate-limit the amount of data that is being migrated to a node.
1939 * Optimal placement is no good if the memory bus is saturated and
1940 * all the time is being spent migrating!
1941 */
1942 if (numamigrate_update_ratelimit(pgdat, HPAGE_PMD_NR))
1943 goto out_dropref;
1944
1945 new_page = alloc_pages_node(node,
1946 (GFP_TRANSHUGE_LIGHT | __GFP_THISNODE),
1947 HPAGE_PMD_ORDER);
1948 if (!new_page)
1949 goto out_fail;
1950 prep_transhuge_page(new_page);
1951
1952 isolated = numamigrate_isolate_page(pgdat, page);
1953 if (!isolated) {
1954 put_page(new_page);
1955 goto out_fail;
1956 }
1957 /*
1958 * We are not sure a pending tlb flush here is for a huge page
1959 * mapping or not. Hence use the tlb range variant
1960 */
1961 if (mm_tlb_flush_pending(mm))
1962 flush_tlb_range(vma, mmun_start, mmun_end);
1963
1964 /* Prepare a page as a migration target */
1965 __SetPageLocked(new_page);
1966 __SetPageSwapBacked(new_page);
1967
1968 /* anon mapping, we can simply copy page->mapping to the new page: */
1969 new_page->mapping = page->mapping;
1970 new_page->index = page->index;
1971 migrate_page_copy(new_page, page);
1972 WARN_ON(PageLRU(new_page));
1973
1974 /* Recheck the target PMD */
1975 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1976 ptl = pmd_lock(mm, pmd);
1977 if (unlikely(!pmd_same(*pmd, entry) || page_count(page) != 2)) {
1978fail_putback:
1979 spin_unlock(ptl);
1980 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1981
1982 /* Reverse changes made by migrate_page_copy() */
1983 if (TestClearPageActive(new_page))
1984 SetPageActive(page);
1985 if (TestClearPageUnevictable(new_page))
1986 SetPageUnevictable(page);
1987
1988 unlock_page(new_page);
1989 put_page(new_page); /* Free it */
1990
1991 /* Retake the callers reference and putback on LRU */
1992 get_page(page);
1993 putback_lru_page(page);
1994 mod_node_page_state(page_pgdat(page),
1995 NR_ISOLATED_ANON + page_lru, -HPAGE_PMD_NR);
1996
1997 goto out_unlock;
1998 }
1999
2000 orig_entry = *pmd;
2001 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
2002 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
2003
2004 /*
2005 * Clear the old entry under pagetable lock and establish the new PTE.
2006 * Any parallel GUP will either observe the old page blocking on the
2007 * page lock, block on the page table lock or observe the new page.
2008 * The SetPageUptodate on the new page and page_add_new_anon_rmap
2009 * guarantee the copy is visible before the pagetable update.
2010 */
2011 flush_cache_range(vma, mmun_start, mmun_end);
2012 page_add_anon_rmap(new_page, vma, mmun_start, true);
2013 pmdp_huge_clear_flush_notify(vma, mmun_start, pmd);
2014 set_pmd_at(mm, mmun_start, pmd, entry);
2015 update_mmu_cache_pmd(vma, address, &entry);
2016
2017 if (page_count(page) != 2) {
2018 set_pmd_at(mm, mmun_start, pmd, orig_entry);
2019 flush_pmd_tlb_range(vma, mmun_start, mmun_end);
2020 mmu_notifier_invalidate_range(mm, mmun_start, mmun_end);
2021 update_mmu_cache_pmd(vma, address, &entry);
2022 page_remove_rmap(new_page, true);
2023 goto fail_putback;
2024 }
2025
2026 mlock_migrate_page(new_page, page);
2027 page_remove_rmap(page, true);
2028 set_page_owner_migrate_reason(new_page, MR_NUMA_MISPLACED);
2029
2030 spin_unlock(ptl);
2031 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2032
2033 /* Take an "isolate" reference and put new page on the LRU. */
2034 get_page(new_page);
2035 putback_lru_page(new_page);
2036
2037 unlock_page(new_page);
2038 unlock_page(page);
2039 put_page(page); /* Drop the rmap reference */
2040 put_page(page); /* Drop the LRU isolation reference */
2041
2042 count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR);
2043 count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR);
2044
2045 mod_node_page_state(page_pgdat(page),
2046 NR_ISOLATED_ANON + page_lru,
2047 -HPAGE_PMD_NR);
2048 return isolated;
2049
2050out_fail:
2051 count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
2052out_dropref:
2053 ptl = pmd_lock(mm, pmd);
2054 if (pmd_same(*pmd, entry)) {
2055 entry = pmd_modify(entry, vma->vm_page_prot);
2056 set_pmd_at(mm, mmun_start, pmd, entry);
2057 update_mmu_cache_pmd(vma, address, &entry);
2058 }
2059 spin_unlock(ptl);
2060
2061out_unlock:
2062 unlock_page(page);
2063 put_page(page);
2064 return 0;
2065}
2066#endif /* CONFIG_NUMA_BALANCING */
2067
2068#endif /* CONFIG_NUMA */