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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/pfn_t.h>
42#include <linux/memremap.h>
43#include <linux/userfaultfd_k.h>
44#include <linux/balloon_compaction.h>
45#include <linux/mmu_notifier.h>
46#include <linux/page_idle.h>
47#include <linux/page_owner.h>
48#include <linux/sched/mm.h>
49#include <linux/ptrace.h>
50
51#include <asm/tlbflush.h>
52
53#define CREATE_TRACE_POINTS
54#include <trace/events/migrate.h>
55
56#include "internal.h"
57
58/*
59 * migrate_prep() needs to be called before we start compiling a list of pages
60 * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
61 * undesirable, use migrate_prep_local()
62 */
63int migrate_prep(void)
64{
65 /*
66 * Clear the LRU lists so pages can be isolated.
67 * Note that pages may be moved off the LRU after we have
68 * drained them. Those pages will fail to migrate like other
69 * pages that may be busy.
70 */
71 lru_add_drain_all();
72
73 return 0;
74}
75
76/* Do the necessary work of migrate_prep but not if it involves other CPUs */
77int migrate_prep_local(void)
78{
79 lru_add_drain();
80
81 return 0;
82}
83
84int isolate_movable_page(struct page *page, isolate_mode_t mode)
85{
86 struct address_space *mapping;
87
88 /*
89 * Avoid burning cycles with pages that are yet under __free_pages(),
90 * or just got freed under us.
91 *
92 * In case we 'win' a race for a movable page being freed under us and
93 * raise its refcount preventing __free_pages() from doing its job
94 * the put_page() at the end of this block will take care of
95 * release this page, thus avoiding a nasty leakage.
96 */
97 if (unlikely(!get_page_unless_zero(page)))
98 goto out;
99
100 /*
101 * Check PageMovable before holding a PG_lock because page's owner
102 * assumes anybody doesn't touch PG_lock of newly allocated page
103 * so unconditionally grapping the lock ruins page's owner side.
104 */
105 if (unlikely(!__PageMovable(page)))
106 goto out_putpage;
107 /*
108 * As movable pages are not isolated from LRU lists, concurrent
109 * compaction threads can race against page migration functions
110 * as well as race against the releasing a page.
111 *
112 * In order to avoid having an already isolated movable page
113 * being (wrongly) re-isolated while it is under migration,
114 * or to avoid attempting to isolate pages being released,
115 * lets be sure we have the page lock
116 * before proceeding with the movable page isolation steps.
117 */
118 if (unlikely(!trylock_page(page)))
119 goto out_putpage;
120
121 if (!PageMovable(page) || PageIsolated(page))
122 goto out_no_isolated;
123
124 mapping = page_mapping(page);
125 VM_BUG_ON_PAGE(!mapping, page);
126
127 if (!mapping->a_ops->isolate_page(page, mode))
128 goto out_no_isolated;
129
130 /* Driver shouldn't use PG_isolated bit of page->flags */
131 WARN_ON_ONCE(PageIsolated(page));
132 __SetPageIsolated(page);
133 unlock_page(page);
134
135 return 0;
136
137out_no_isolated:
138 unlock_page(page);
139out_putpage:
140 put_page(page);
141out:
142 return -EBUSY;
143}
144
145/* It should be called on page which is PG_movable */
146void putback_movable_page(struct page *page)
147{
148 struct address_space *mapping;
149
150 VM_BUG_ON_PAGE(!PageLocked(page), page);
151 VM_BUG_ON_PAGE(!PageMovable(page), page);
152 VM_BUG_ON_PAGE(!PageIsolated(page), page);
153
154 mapping = page_mapping(page);
155 mapping->a_ops->putback_page(page);
156 __ClearPageIsolated(page);
157}
158
159/*
160 * Put previously isolated pages back onto the appropriate lists
161 * from where they were once taken off for compaction/migration.
162 *
163 * This function shall be used whenever the isolated pageset has been
164 * built from lru, balloon, hugetlbfs page. See isolate_migratepages_range()
165 * and isolate_huge_page().
166 */
167void putback_movable_pages(struct list_head *l)
168{
169 struct page *page;
170 struct page *page2;
171
172 list_for_each_entry_safe(page, page2, l, lru) {
173 if (unlikely(PageHuge(page))) {
174 putback_active_hugepage(page);
175 continue;
176 }
177 list_del(&page->lru);
178 /*
179 * We isolated non-lru movable page so here we can use
180 * __PageMovable because LRU page's mapping cannot have
181 * PAGE_MAPPING_MOVABLE.
182 */
183 if (unlikely(__PageMovable(page))) {
184 VM_BUG_ON_PAGE(!PageIsolated(page), page);
185 lock_page(page);
186 if (PageMovable(page))
187 putback_movable_page(page);
188 else
189 __ClearPageIsolated(page);
190 unlock_page(page);
191 put_page(page);
192 } else {
193 mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
194 page_is_file_cache(page), -hpage_nr_pages(page));
195 putback_lru_page(page);
196 }
197 }
198}
199
200/*
201 * Restore a potential migration pte to a working pte entry
202 */
203static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma,
204 unsigned long addr, void *old)
205{
206 struct page_vma_mapped_walk pvmw = {
207 .page = old,
208 .vma = vma,
209 .address = addr,
210 .flags = PVMW_SYNC | PVMW_MIGRATION,
211 };
212 struct page *new;
213 pte_t pte;
214 swp_entry_t entry;
215
216 VM_BUG_ON_PAGE(PageTail(page), page);
217 while (page_vma_mapped_walk(&pvmw)) {
218 if (PageKsm(page))
219 new = page;
220 else
221 new = page - pvmw.page->index +
222 linear_page_index(vma, pvmw.address);
223
224#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
225 /* PMD-mapped THP migration entry */
226 if (!pvmw.pte) {
227 VM_BUG_ON_PAGE(PageHuge(page) || !PageTransCompound(page), page);
228 remove_migration_pmd(&pvmw, new);
229 continue;
230 }
231#endif
232
233 get_page(new);
234 pte = pte_mkold(mk_pte(new, READ_ONCE(vma->vm_page_prot)));
235 if (pte_swp_soft_dirty(*pvmw.pte))
236 pte = pte_mksoft_dirty(pte);
237
238 /*
239 * Recheck VMA as permissions can change since migration started
240 */
241 entry = pte_to_swp_entry(*pvmw.pte);
242 if (is_write_migration_entry(entry))
243 pte = maybe_mkwrite(pte, vma);
244
245 if (unlikely(is_zone_device_page(new))) {
246 if (is_device_private_page(new)) {
247 entry = make_device_private_entry(new, pte_write(pte));
248 pte = swp_entry_to_pte(entry);
249 } else if (is_device_public_page(new)) {
250 pte = pte_mkdevmap(pte);
251 flush_dcache_page(new);
252 }
253 } else
254 flush_dcache_page(new);
255
256#ifdef CONFIG_HUGETLB_PAGE
257 if (PageHuge(new)) {
258 pte = pte_mkhuge(pte);
259 pte = arch_make_huge_pte(pte, vma, new, 0);
260 set_huge_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
261 if (PageAnon(new))
262 hugepage_add_anon_rmap(new, vma, pvmw.address);
263 else
264 page_dup_rmap(new, true);
265 } else
266#endif
267 {
268 set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
269
270 if (PageAnon(new))
271 page_add_anon_rmap(new, vma, pvmw.address, false);
272 else
273 page_add_file_rmap(new, false);
274 }
275 if (vma->vm_flags & VM_LOCKED && !PageTransCompound(new))
276 mlock_vma_page(new);
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 radix-tree replacement of page migration started, page_count
327 * *must* be zero. And, we don't want to call wait_on_page_locked()
328 * against a page without get_page().
329 * So, we use get_page_unless_zero(), here. Even failed, page fault
330 * will occur again.
331 */
332 if (!get_page_unless_zero(page))
333 goto out;
334 pte_unmap_unlock(ptep, ptl);
335 wait_on_page_locked(page);
336 put_page(page);
337 return;
338out:
339 pte_unmap_unlock(ptep, ptl);
340}
341
342void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
343 unsigned long address)
344{
345 spinlock_t *ptl = pte_lockptr(mm, pmd);
346 pte_t *ptep = pte_offset_map(pmd, address);
347 __migration_entry_wait(mm, ptep, ptl);
348}
349
350void migration_entry_wait_huge(struct vm_area_struct *vma,
351 struct mm_struct *mm, pte_t *pte)
352{
353 spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), mm, pte);
354 __migration_entry_wait(mm, pte, ptl);
355}
356
357#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
358void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)
359{
360 spinlock_t *ptl;
361 struct page *page;
362
363 ptl = pmd_lock(mm, pmd);
364 if (!is_pmd_migration_entry(*pmd))
365 goto unlock;
366 page = migration_entry_to_page(pmd_to_swp_entry(*pmd));
367 if (!get_page_unless_zero(page))
368 goto unlock;
369 spin_unlock(ptl);
370 wait_on_page_locked(page);
371 put_page(page);
372 return;
373unlock:
374 spin_unlock(ptl);
375}
376#endif
377
378#ifdef CONFIG_BLOCK
379/* Returns true if all buffers are successfully locked */
380static bool buffer_migrate_lock_buffers(struct buffer_head *head,
381 enum migrate_mode mode)
382{
383 struct buffer_head *bh = head;
384
385 /* Simple case, sync compaction */
386 if (mode != MIGRATE_ASYNC) {
387 do {
388 get_bh(bh);
389 lock_buffer(bh);
390 bh = bh->b_this_page;
391
392 } while (bh != head);
393
394 return true;
395 }
396
397 /* async case, we cannot block on lock_buffer so use trylock_buffer */
398 do {
399 get_bh(bh);
400 if (!trylock_buffer(bh)) {
401 /*
402 * We failed to lock the buffer and cannot stall in
403 * async migration. Release the taken locks
404 */
405 struct buffer_head *failed_bh = bh;
406 put_bh(failed_bh);
407 bh = head;
408 while (bh != failed_bh) {
409 unlock_buffer(bh);
410 put_bh(bh);
411 bh = bh->b_this_page;
412 }
413 return false;
414 }
415
416 bh = bh->b_this_page;
417 } while (bh != head);
418 return true;
419}
420#else
421static inline bool buffer_migrate_lock_buffers(struct buffer_head *head,
422 enum migrate_mode mode)
423{
424 return true;
425}
426#endif /* CONFIG_BLOCK */
427
428/*
429 * Replace the page in the mapping.
430 *
431 * The number of remaining references must be:
432 * 1 for anonymous pages without a mapping
433 * 2 for pages with a mapping
434 * 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
435 */
436int migrate_page_move_mapping(struct address_space *mapping,
437 struct page *newpage, struct page *page,
438 struct buffer_head *head, enum migrate_mode mode,
439 int extra_count)
440{
441 struct zone *oldzone, *newzone;
442 int dirty;
443 int expected_count = 1 + extra_count;
444 void **pslot;
445
446 /*
447 * Device public or private pages have an extra refcount as they are
448 * ZONE_DEVICE pages.
449 */
450 expected_count += is_device_private_page(page);
451 expected_count += is_device_public_page(page);
452
453 if (!mapping) {
454 /* Anonymous page without mapping */
455 if (page_count(page) != expected_count)
456 return -EAGAIN;
457
458 /* No turning back from here */
459 newpage->index = page->index;
460 newpage->mapping = page->mapping;
461 if (PageSwapBacked(page))
462 __SetPageSwapBacked(newpage);
463
464 return MIGRATEPAGE_SUCCESS;
465 }
466
467 oldzone = page_zone(page);
468 newzone = page_zone(newpage);
469
470 xa_lock_irq(&mapping->i_pages);
471
472 pslot = radix_tree_lookup_slot(&mapping->i_pages,
473 page_index(page));
474
475 expected_count += hpage_nr_pages(page) + page_has_private(page);
476 if (page_count(page) != expected_count ||
477 radix_tree_deref_slot_protected(pslot,
478 &mapping->i_pages.xa_lock) != page) {
479 xa_unlock_irq(&mapping->i_pages);
480 return -EAGAIN;
481 }
482
483 if (!page_ref_freeze(page, expected_count)) {
484 xa_unlock_irq(&mapping->i_pages);
485 return -EAGAIN;
486 }
487
488 /*
489 * In the async migration case of moving a page with buffers, lock the
490 * buffers using trylock before the mapping is moved. If the mapping
491 * was moved, we later failed to lock the buffers and could not move
492 * the mapping back due to an elevated page count, we would have to
493 * block waiting on other references to be dropped.
494 */
495 if (mode == MIGRATE_ASYNC && head &&
496 !buffer_migrate_lock_buffers(head, mode)) {
497 page_ref_unfreeze(page, expected_count);
498 xa_unlock_irq(&mapping->i_pages);
499 return -EAGAIN;
500 }
501
502 /*
503 * Now we know that no one else is looking at the page:
504 * no turning back from here.
505 */
506 newpage->index = page->index;
507 newpage->mapping = page->mapping;
508 page_ref_add(newpage, hpage_nr_pages(page)); /* add cache reference */
509 if (PageSwapBacked(page)) {
510 __SetPageSwapBacked(newpage);
511 if (PageSwapCache(page)) {
512 SetPageSwapCache(newpage);
513 set_page_private(newpage, page_private(page));
514 }
515 } else {
516 VM_BUG_ON_PAGE(PageSwapCache(page), page);
517 }
518
519 /* Move dirty while page refs frozen and newpage not yet exposed */
520 dirty = PageDirty(page);
521 if (dirty) {
522 ClearPageDirty(page);
523 SetPageDirty(newpage);
524 }
525
526 radix_tree_replace_slot(&mapping->i_pages, pslot, newpage);
527 if (PageTransHuge(page)) {
528 int i;
529 int index = page_index(page);
530
531 for (i = 1; i < HPAGE_PMD_NR; i++) {
532 pslot = radix_tree_lookup_slot(&mapping->i_pages,
533 index + i);
534 radix_tree_replace_slot(&mapping->i_pages, pslot,
535 newpage + i);
536 }
537 }
538
539 /*
540 * Drop cache reference from old page by unfreezing
541 * to one less reference.
542 * We know this isn't the last reference.
543 */
544 page_ref_unfreeze(page, expected_count - hpage_nr_pages(page));
545
546 xa_unlock(&mapping->i_pages);
547 /* Leave irq disabled to prevent preemption while updating stats */
548
549 /*
550 * If moved to a different zone then also account
551 * the page for that zone. Other VM counters will be
552 * taken care of when we establish references to the
553 * new page and drop references to the old page.
554 *
555 * Note that anonymous pages are accounted for
556 * via NR_FILE_PAGES and NR_ANON_MAPPED if they
557 * are mapped to swap space.
558 */
559 if (newzone != oldzone) {
560 __dec_node_state(oldzone->zone_pgdat, NR_FILE_PAGES);
561 __inc_node_state(newzone->zone_pgdat, NR_FILE_PAGES);
562 if (PageSwapBacked(page) && !PageSwapCache(page)) {
563 __dec_node_state(oldzone->zone_pgdat, NR_SHMEM);
564 __inc_node_state(newzone->zone_pgdat, NR_SHMEM);
565 }
566 if (dirty && mapping_cap_account_dirty(mapping)) {
567 __dec_node_state(oldzone->zone_pgdat, NR_FILE_DIRTY);
568 __dec_zone_state(oldzone, NR_ZONE_WRITE_PENDING);
569 __inc_node_state(newzone->zone_pgdat, NR_FILE_DIRTY);
570 __inc_zone_state(newzone, NR_ZONE_WRITE_PENDING);
571 }
572 }
573 local_irq_enable();
574
575 return MIGRATEPAGE_SUCCESS;
576}
577EXPORT_SYMBOL(migrate_page_move_mapping);
578
579/*
580 * The expected number of remaining references is the same as that
581 * of migrate_page_move_mapping().
582 */
583int migrate_huge_page_move_mapping(struct address_space *mapping,
584 struct page *newpage, struct page *page)
585{
586 int expected_count;
587 void **pslot;
588
589 xa_lock_irq(&mapping->i_pages);
590
591 pslot = radix_tree_lookup_slot(&mapping->i_pages, page_index(page));
592
593 expected_count = 2 + page_has_private(page);
594 if (page_count(page) != expected_count ||
595 radix_tree_deref_slot_protected(pslot, &mapping->i_pages.xa_lock) != page) {
596 xa_unlock_irq(&mapping->i_pages);
597 return -EAGAIN;
598 }
599
600 if (!page_ref_freeze(page, expected_count)) {
601 xa_unlock_irq(&mapping->i_pages);
602 return -EAGAIN;
603 }
604
605 newpage->index = page->index;
606 newpage->mapping = page->mapping;
607
608 get_page(newpage);
609
610 radix_tree_replace_slot(&mapping->i_pages, pslot, newpage);
611
612 page_ref_unfreeze(page, expected_count - 1);
613
614 xa_unlock_irq(&mapping->i_pages);
615
616 return MIGRATEPAGE_SUCCESS;
617}
618
619/*
620 * Gigantic pages are so large that we do not guarantee that page++ pointer
621 * arithmetic will work across the entire page. We need something more
622 * specialized.
623 */
624static void __copy_gigantic_page(struct page *dst, struct page *src,
625 int nr_pages)
626{
627 int i;
628 struct page *dst_base = dst;
629 struct page *src_base = src;
630
631 for (i = 0; i < nr_pages; ) {
632 cond_resched();
633 copy_highpage(dst, src);
634
635 i++;
636 dst = mem_map_next(dst, dst_base, i);
637 src = mem_map_next(src, src_base, i);
638 }
639}
640
641static void copy_huge_page(struct page *dst, struct page *src)
642{
643 int i;
644 int nr_pages;
645
646 if (PageHuge(src)) {
647 /* hugetlbfs page */
648 struct hstate *h = page_hstate(src);
649 nr_pages = pages_per_huge_page(h);
650
651 if (unlikely(nr_pages > MAX_ORDER_NR_PAGES)) {
652 __copy_gigantic_page(dst, src, nr_pages);
653 return;
654 }
655 } else {
656 /* thp page */
657 BUG_ON(!PageTransHuge(src));
658 nr_pages = hpage_nr_pages(src);
659 }
660
661 for (i = 0; i < nr_pages; i++) {
662 cond_resched();
663 copy_highpage(dst + i, src + i);
664 }
665}
666
667/*
668 * Copy the page to its new location
669 */
670void migrate_page_states(struct page *newpage, struct page *page)
671{
672 int cpupid;
673
674 if (PageError(page))
675 SetPageError(newpage);
676 if (PageReferenced(page))
677 SetPageReferenced(newpage);
678 if (PageUptodate(page))
679 SetPageUptodate(newpage);
680 if (TestClearPageActive(page)) {
681 VM_BUG_ON_PAGE(PageUnevictable(page), page);
682 SetPageActive(newpage);
683 } else if (TestClearPageUnevictable(page))
684 SetPageUnevictable(newpage);
685 if (PageChecked(page))
686 SetPageChecked(newpage);
687 if (PageMappedToDisk(page))
688 SetPageMappedToDisk(newpage);
689
690 /* Move dirty on pages not done by migrate_page_move_mapping() */
691 if (PageDirty(page))
692 SetPageDirty(newpage);
693
694 if (page_is_young(page))
695 set_page_young(newpage);
696 if (page_is_idle(page))
697 set_page_idle(newpage);
698
699 /*
700 * Copy NUMA information to the new page, to prevent over-eager
701 * future migrations of this same page.
702 */
703 cpupid = page_cpupid_xchg_last(page, -1);
704 page_cpupid_xchg_last(newpage, cpupid);
705
706 ksm_migrate_page(newpage, page);
707 /*
708 * Please do not reorder this without considering how mm/ksm.c's
709 * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
710 */
711 if (PageSwapCache(page))
712 ClearPageSwapCache(page);
713 ClearPagePrivate(page);
714 set_page_private(page, 0);
715
716 /*
717 * If any waiters have accumulated on the new page then
718 * wake them up.
719 */
720 if (PageWriteback(newpage))
721 end_page_writeback(newpage);
722
723 copy_page_owner(page, newpage);
724
725 mem_cgroup_migrate(page, newpage);
726}
727EXPORT_SYMBOL(migrate_page_states);
728
729void migrate_page_copy(struct page *newpage, struct page *page)
730{
731 if (PageHuge(page) || PageTransHuge(page))
732 copy_huge_page(newpage, page);
733 else
734 copy_highpage(newpage, page);
735
736 migrate_page_states(newpage, page);
737}
738EXPORT_SYMBOL(migrate_page_copy);
739
740/************************************************************
741 * Migration functions
742 ***********************************************************/
743
744/*
745 * Common logic to directly migrate a single LRU page suitable for
746 * pages that do not use PagePrivate/PagePrivate2.
747 *
748 * Pages are locked upon entry and exit.
749 */
750int migrate_page(struct address_space *mapping,
751 struct page *newpage, struct page *page,
752 enum migrate_mode mode)
753{
754 int rc;
755
756 BUG_ON(PageWriteback(page)); /* Writeback must be complete */
757
758 rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode, 0);
759
760 if (rc != MIGRATEPAGE_SUCCESS)
761 return rc;
762
763 if (mode != MIGRATE_SYNC_NO_COPY)
764 migrate_page_copy(newpage, page);
765 else
766 migrate_page_states(newpage, page);
767 return MIGRATEPAGE_SUCCESS;
768}
769EXPORT_SYMBOL(migrate_page);
770
771#ifdef CONFIG_BLOCK
772/*
773 * Migration function for pages with buffers. This function can only be used
774 * if the underlying filesystem guarantees that no other references to "page"
775 * exist.
776 */
777int buffer_migrate_page(struct address_space *mapping,
778 struct page *newpage, struct page *page, enum migrate_mode mode)
779{
780 struct buffer_head *bh, *head;
781 int rc;
782
783 if (!page_has_buffers(page))
784 return migrate_page(mapping, newpage, page, mode);
785
786 head = page_buffers(page);
787
788 rc = migrate_page_move_mapping(mapping, newpage, page, head, mode, 0);
789
790 if (rc != MIGRATEPAGE_SUCCESS)
791 return rc;
792
793 /*
794 * In the async case, migrate_page_move_mapping locked the buffers
795 * with an IRQ-safe spinlock held. In the sync case, the buffers
796 * need to be locked now
797 */
798 if (mode != MIGRATE_ASYNC)
799 BUG_ON(!buffer_migrate_lock_buffers(head, mode));
800
801 ClearPagePrivate(page);
802 set_page_private(newpage, page_private(page));
803 set_page_private(page, 0);
804 put_page(page);
805 get_page(newpage);
806
807 bh = head;
808 do {
809 set_bh_page(bh, newpage, bh_offset(bh));
810 bh = bh->b_this_page;
811
812 } while (bh != head);
813
814 SetPagePrivate(newpage);
815
816 if (mode != MIGRATE_SYNC_NO_COPY)
817 migrate_page_copy(newpage, page);
818 else
819 migrate_page_states(newpage, page);
820
821 bh = head;
822 do {
823 unlock_buffer(bh);
824 put_bh(bh);
825 bh = bh->b_this_page;
826
827 } while (bh != head);
828
829 return MIGRATEPAGE_SUCCESS;
830}
831EXPORT_SYMBOL(buffer_migrate_page);
832#endif
833
834/*
835 * Writeback a page to clean the dirty state
836 */
837static int writeout(struct address_space *mapping, struct page *page)
838{
839 struct writeback_control wbc = {
840 .sync_mode = WB_SYNC_NONE,
841 .nr_to_write = 1,
842 .range_start = 0,
843 .range_end = LLONG_MAX,
844 .for_reclaim = 1
845 };
846 int rc;
847
848 if (!mapping->a_ops->writepage)
849 /* No write method for the address space */
850 return -EINVAL;
851
852 if (!clear_page_dirty_for_io(page))
853 /* Someone else already triggered a write */
854 return -EAGAIN;
855
856 /*
857 * A dirty page may imply that the underlying filesystem has
858 * the page on some queue. So the page must be clean for
859 * migration. Writeout may mean we loose the lock and the
860 * page state is no longer what we checked for earlier.
861 * At this point we know that the migration attempt cannot
862 * be successful.
863 */
864 remove_migration_ptes(page, page, false);
865
866 rc = mapping->a_ops->writepage(page, &wbc);
867
868 if (rc != AOP_WRITEPAGE_ACTIVATE)
869 /* unlocked. Relock */
870 lock_page(page);
871
872 return (rc < 0) ? -EIO : -EAGAIN;
873}
874
875/*
876 * Default handling if a filesystem does not provide a migration function.
877 */
878static int fallback_migrate_page(struct address_space *mapping,
879 struct page *newpage, struct page *page, enum migrate_mode mode)
880{
881 if (PageDirty(page)) {
882 /* Only writeback pages in full synchronous migration */
883 switch (mode) {
884 case MIGRATE_SYNC:
885 case MIGRATE_SYNC_NO_COPY:
886 break;
887 default:
888 return -EBUSY;
889 }
890 return writeout(mapping, page);
891 }
892
893 /*
894 * Buffers may be managed in a filesystem specific way.
895 * We must have no buffers or drop them.
896 */
897 if (page_has_private(page) &&
898 !try_to_release_page(page, GFP_KERNEL))
899 return -EAGAIN;
900
901 return migrate_page(mapping, newpage, page, mode);
902}
903
904/*
905 * Move a page to a newly allocated page
906 * The page is locked and all ptes have been successfully removed.
907 *
908 * The new page will have replaced the old page if this function
909 * is successful.
910 *
911 * Return value:
912 * < 0 - error code
913 * MIGRATEPAGE_SUCCESS - success
914 */
915static int move_to_new_page(struct page *newpage, struct page *page,
916 enum migrate_mode mode)
917{
918 struct address_space *mapping;
919 int rc = -EAGAIN;
920 bool is_lru = !__PageMovable(page);
921
922 VM_BUG_ON_PAGE(!PageLocked(page), page);
923 VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
924
925 mapping = page_mapping(page);
926
927 if (likely(is_lru)) {
928 if (!mapping)
929 rc = migrate_page(mapping, newpage, page, mode);
930 else if (mapping->a_ops->migratepage)
931 /*
932 * Most pages have a mapping and most filesystems
933 * provide a migratepage callback. Anonymous pages
934 * are part of swap space which also has its own
935 * migratepage callback. This is the most common path
936 * for page migration.
937 */
938 rc = mapping->a_ops->migratepage(mapping, newpage,
939 page, mode);
940 else
941 rc = fallback_migrate_page(mapping, newpage,
942 page, mode);
943 } else {
944 /*
945 * In case of non-lru page, it could be released after
946 * isolation step. In that case, we shouldn't try migration.
947 */
948 VM_BUG_ON_PAGE(!PageIsolated(page), page);
949 if (!PageMovable(page)) {
950 rc = MIGRATEPAGE_SUCCESS;
951 __ClearPageIsolated(page);
952 goto out;
953 }
954
955 rc = mapping->a_ops->migratepage(mapping, newpage,
956 page, mode);
957 WARN_ON_ONCE(rc == MIGRATEPAGE_SUCCESS &&
958 !PageIsolated(page));
959 }
960
961 /*
962 * When successful, old pagecache page->mapping must be cleared before
963 * page is freed; but stats require that PageAnon be left as PageAnon.
964 */
965 if (rc == MIGRATEPAGE_SUCCESS) {
966 if (__PageMovable(page)) {
967 VM_BUG_ON_PAGE(!PageIsolated(page), page);
968
969 /*
970 * We clear PG_movable under page_lock so any compactor
971 * cannot try to migrate this page.
972 */
973 __ClearPageIsolated(page);
974 }
975
976 /*
977 * Anonymous and movable page->mapping will be cleard by
978 * free_pages_prepare so don't reset it here for keeping
979 * the type to work PageAnon, for example.
980 */
981 if (!PageMappingFlags(page))
982 page->mapping = NULL;
983 }
984out:
985 return rc;
986}
987
988static int __unmap_and_move(struct page *page, struct page *newpage,
989 int force, enum migrate_mode mode)
990{
991 int rc = -EAGAIN;
992 int page_was_mapped = 0;
993 struct anon_vma *anon_vma = NULL;
994 bool is_lru = !__PageMovable(page);
995
996 if (!trylock_page(page)) {
997 if (!force || mode == MIGRATE_ASYNC)
998 goto out;
999
1000 /*
1001 * It's not safe for direct compaction to call lock_page.
1002 * For example, during page readahead pages are added locked
1003 * to the LRU. Later, when the IO completes the pages are
1004 * marked uptodate and unlocked. However, the queueing
1005 * could be merging multiple pages for one bio (e.g.
1006 * mpage_readpages). If an allocation happens for the
1007 * second or third page, the process can end up locking
1008 * the same page twice and deadlocking. Rather than
1009 * trying to be clever about what pages can be locked,
1010 * avoid the use of lock_page for direct compaction
1011 * altogether.
1012 */
1013 if (current->flags & PF_MEMALLOC)
1014 goto out;
1015
1016 lock_page(page);
1017 }
1018
1019 if (PageWriteback(page)) {
1020 /*
1021 * Only in the case of a full synchronous migration is it
1022 * necessary to wait for PageWriteback. In the async case,
1023 * the retry loop is too short and in the sync-light case,
1024 * the overhead of stalling is too much
1025 */
1026 switch (mode) {
1027 case MIGRATE_SYNC:
1028 case MIGRATE_SYNC_NO_COPY:
1029 break;
1030 default:
1031 rc = -EBUSY;
1032 goto out_unlock;
1033 }
1034 if (!force)
1035 goto out_unlock;
1036 wait_on_page_writeback(page);
1037 }
1038
1039 /*
1040 * By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
1041 * we cannot notice that anon_vma is freed while we migrates a page.
1042 * This get_anon_vma() delays freeing anon_vma pointer until the end
1043 * of migration. File cache pages are no problem because of page_lock()
1044 * File Caches may use write_page() or lock_page() in migration, then,
1045 * just care Anon page here.
1046 *
1047 * Only page_get_anon_vma() understands the subtleties of
1048 * getting a hold on an anon_vma from outside one of its mms.
1049 * But if we cannot get anon_vma, then we won't need it anyway,
1050 * because that implies that the anon page is no longer mapped
1051 * (and cannot be remapped so long as we hold the page lock).
1052 */
1053 if (PageAnon(page) && !PageKsm(page))
1054 anon_vma = page_get_anon_vma(page);
1055
1056 /*
1057 * Block others from accessing the new page when we get around to
1058 * establishing additional references. We are usually the only one
1059 * holding a reference to newpage at this point. We used to have a BUG
1060 * here if trylock_page(newpage) fails, but would like to allow for
1061 * cases where there might be a race with the previous use of newpage.
1062 * This is much like races on refcount of oldpage: just don't BUG().
1063 */
1064 if (unlikely(!trylock_page(newpage)))
1065 goto out_unlock;
1066
1067 if (unlikely(!is_lru)) {
1068 rc = move_to_new_page(newpage, page, mode);
1069 goto out_unlock_both;
1070 }
1071
1072 /*
1073 * Corner case handling:
1074 * 1. When a new swap-cache page is read into, it is added to the LRU
1075 * and treated as swapcache but it has no rmap yet.
1076 * Calling try_to_unmap() against a page->mapping==NULL page will
1077 * trigger a BUG. So handle it here.
1078 * 2. An orphaned page (see truncate_complete_page) might have
1079 * fs-private metadata. The page can be picked up due to memory
1080 * offlining. Everywhere else except page reclaim, the page is
1081 * invisible to the vm, so the page can not be migrated. So try to
1082 * free the metadata, so the page can be freed.
1083 */
1084 if (!page->mapping) {
1085 VM_BUG_ON_PAGE(PageAnon(page), page);
1086 if (page_has_private(page)) {
1087 try_to_free_buffers(page);
1088 goto out_unlock_both;
1089 }
1090 } else if (page_mapped(page)) {
1091 /* Establish migration ptes */
1092 VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma,
1093 page);
1094 try_to_unmap(page,
1095 TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
1096 page_was_mapped = 1;
1097 }
1098
1099 if (!page_mapped(page))
1100 rc = move_to_new_page(newpage, page, mode);
1101
1102 if (page_was_mapped)
1103 remove_migration_ptes(page,
1104 rc == MIGRATEPAGE_SUCCESS ? newpage : page, false);
1105
1106out_unlock_both:
1107 unlock_page(newpage);
1108out_unlock:
1109 /* Drop an anon_vma reference if we took one */
1110 if (anon_vma)
1111 put_anon_vma(anon_vma);
1112 unlock_page(page);
1113out:
1114 /*
1115 * If migration is successful, decrease refcount of the newpage
1116 * which will not free the page because new page owner increased
1117 * refcounter. As well, if it is LRU page, add the page to LRU
1118 * list in here.
1119 */
1120 if (rc == MIGRATEPAGE_SUCCESS) {
1121 if (unlikely(__PageMovable(newpage)))
1122 put_page(newpage);
1123 else
1124 putback_lru_page(newpage);
1125 }
1126
1127 return rc;
1128}
1129
1130/*
1131 * gcc 4.7 and 4.8 on arm get an ICEs when inlining unmap_and_move(). Work
1132 * around it.
1133 */
1134#if (GCC_VERSION >= 40700 && GCC_VERSION < 40900) && defined(CONFIG_ARM)
1135#define ICE_noinline noinline
1136#else
1137#define ICE_noinline
1138#endif
1139
1140/*
1141 * Obtain the lock on page, remove all ptes and migrate the page
1142 * to the newly allocated page in newpage.
1143 */
1144static ICE_noinline int unmap_and_move(new_page_t get_new_page,
1145 free_page_t put_new_page,
1146 unsigned long private, struct page *page,
1147 int force, enum migrate_mode mode,
1148 enum migrate_reason reason)
1149{
1150 int rc = MIGRATEPAGE_SUCCESS;
1151 struct page *newpage;
1152
1153 if (!thp_migration_supported() && PageTransHuge(page))
1154 return -ENOMEM;
1155
1156 newpage = get_new_page(page, private);
1157 if (!newpage)
1158 return -ENOMEM;
1159
1160 if (page_count(page) == 1) {
1161 /* page was freed from under us. So we are done. */
1162 ClearPageActive(page);
1163 ClearPageUnevictable(page);
1164 if (unlikely(__PageMovable(page))) {
1165 lock_page(page);
1166 if (!PageMovable(page))
1167 __ClearPageIsolated(page);
1168 unlock_page(page);
1169 }
1170 if (put_new_page)
1171 put_new_page(newpage, private);
1172 else
1173 put_page(newpage);
1174 goto out;
1175 }
1176
1177 rc = __unmap_and_move(page, newpage, force, mode);
1178 if (rc == MIGRATEPAGE_SUCCESS)
1179 set_page_owner_migrate_reason(newpage, reason);
1180
1181out:
1182 if (rc != -EAGAIN) {
1183 /*
1184 * A page that has been migrated has all references
1185 * removed and will be freed. A page that has not been
1186 * migrated will have kepts its references and be
1187 * restored.
1188 */
1189 list_del(&page->lru);
1190
1191 /*
1192 * Compaction can migrate also non-LRU pages which are
1193 * not accounted to NR_ISOLATED_*. They can be recognized
1194 * as __PageMovable
1195 */
1196 if (likely(!__PageMovable(page)))
1197 mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
1198 page_is_file_cache(page), -hpage_nr_pages(page));
1199 }
1200
1201 /*
1202 * If migration is successful, releases reference grabbed during
1203 * isolation. Otherwise, restore the page to right list unless
1204 * we want to retry.
1205 */
1206 if (rc == MIGRATEPAGE_SUCCESS) {
1207 put_page(page);
1208 if (reason == MR_MEMORY_FAILURE) {
1209 /*
1210 * Set PG_HWPoison on just freed page
1211 * intentionally. Although it's rather weird,
1212 * it's how HWPoison flag works at the moment.
1213 */
1214 if (!test_set_page_hwpoison(page))
1215 num_poisoned_pages_inc();
1216 }
1217 } else {
1218 if (rc != -EAGAIN) {
1219 if (likely(!__PageMovable(page))) {
1220 putback_lru_page(page);
1221 goto put_new;
1222 }
1223
1224 lock_page(page);
1225 if (PageMovable(page))
1226 putback_movable_page(page);
1227 else
1228 __ClearPageIsolated(page);
1229 unlock_page(page);
1230 put_page(page);
1231 }
1232put_new:
1233 if (put_new_page)
1234 put_new_page(newpage, private);
1235 else
1236 put_page(newpage);
1237 }
1238
1239 return rc;
1240}
1241
1242/*
1243 * Counterpart of unmap_and_move_page() for hugepage migration.
1244 *
1245 * This function doesn't wait the completion of hugepage I/O
1246 * because there is no race between I/O and migration for hugepage.
1247 * Note that currently hugepage I/O occurs only in direct I/O
1248 * where no lock is held and PG_writeback is irrelevant,
1249 * and writeback status of all subpages are counted in the reference
1250 * count of the head page (i.e. if all subpages of a 2MB hugepage are
1251 * under direct I/O, the reference of the head page is 512 and a bit more.)
1252 * This means that when we try to migrate hugepage whose subpages are
1253 * doing direct I/O, some references remain after try_to_unmap() and
1254 * hugepage migration fails without data corruption.
1255 *
1256 * There is also no race when direct I/O is issued on the page under migration,
1257 * because then pte is replaced with migration swap entry and direct I/O code
1258 * will wait in the page fault for migration to complete.
1259 */
1260static int unmap_and_move_huge_page(new_page_t get_new_page,
1261 free_page_t put_new_page, unsigned long private,
1262 struct page *hpage, int force,
1263 enum migrate_mode mode, int reason)
1264{
1265 int rc = -EAGAIN;
1266 int page_was_mapped = 0;
1267 struct page *new_hpage;
1268 struct anon_vma *anon_vma = NULL;
1269
1270 /*
1271 * Movability of hugepages depends on architectures and hugepage size.
1272 * This check is necessary because some callers of hugepage migration
1273 * like soft offline and memory hotremove don't walk through page
1274 * tables or check whether the hugepage is pmd-based or not before
1275 * kicking migration.
1276 */
1277 if (!hugepage_migration_supported(page_hstate(hpage))) {
1278 putback_active_hugepage(hpage);
1279 return -ENOSYS;
1280 }
1281
1282 new_hpage = get_new_page(hpage, private);
1283 if (!new_hpage)
1284 return -ENOMEM;
1285
1286 if (!trylock_page(hpage)) {
1287 if (!force)
1288 goto out;
1289 switch (mode) {
1290 case MIGRATE_SYNC:
1291 case MIGRATE_SYNC_NO_COPY:
1292 break;
1293 default:
1294 goto out;
1295 }
1296 lock_page(hpage);
1297 }
1298
1299 if (PageAnon(hpage))
1300 anon_vma = page_get_anon_vma(hpage);
1301
1302 if (unlikely(!trylock_page(new_hpage)))
1303 goto put_anon;
1304
1305 if (page_mapped(hpage)) {
1306 try_to_unmap(hpage,
1307 TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
1308 page_was_mapped = 1;
1309 }
1310
1311 if (!page_mapped(hpage))
1312 rc = move_to_new_page(new_hpage, hpage, mode);
1313
1314 if (page_was_mapped)
1315 remove_migration_ptes(hpage,
1316 rc == MIGRATEPAGE_SUCCESS ? new_hpage : hpage, false);
1317
1318 unlock_page(new_hpage);
1319
1320put_anon:
1321 if (anon_vma)
1322 put_anon_vma(anon_vma);
1323
1324 if (rc == MIGRATEPAGE_SUCCESS) {
1325 move_hugetlb_state(hpage, new_hpage, reason);
1326 put_new_page = NULL;
1327 }
1328
1329 unlock_page(hpage);
1330out:
1331 if (rc != -EAGAIN)
1332 putback_active_hugepage(hpage);
1333 if (reason == MR_MEMORY_FAILURE && !test_set_page_hwpoison(hpage))
1334 num_poisoned_pages_inc();
1335
1336 /*
1337 * If migration was not successful and there's a freeing callback, use
1338 * it. Otherwise, put_page() will drop the reference grabbed during
1339 * isolation.
1340 */
1341 if (put_new_page)
1342 put_new_page(new_hpage, private);
1343 else
1344 putback_active_hugepage(new_hpage);
1345
1346 return rc;
1347}
1348
1349/*
1350 * migrate_pages - migrate the pages specified in a list, to the free pages
1351 * supplied as the target for the page migration
1352 *
1353 * @from: The list of pages to be migrated.
1354 * @get_new_page: The function used to allocate free pages to be used
1355 * as the target of the page migration.
1356 * @put_new_page: The function used to free target pages if migration
1357 * fails, or NULL if no special handling is necessary.
1358 * @private: Private data to be passed on to get_new_page()
1359 * @mode: The migration mode that specifies the constraints for
1360 * page migration, if any.
1361 * @reason: The reason for page migration.
1362 *
1363 * The function returns after 10 attempts or if no pages are movable any more
1364 * because the list has become empty or no retryable pages exist any more.
1365 * The caller should call putback_movable_pages() to return pages to the LRU
1366 * or free list only if ret != 0.
1367 *
1368 * Returns the number of pages that were not migrated, or an error code.
1369 */
1370int migrate_pages(struct list_head *from, new_page_t get_new_page,
1371 free_page_t put_new_page, unsigned long private,
1372 enum migrate_mode mode, int reason)
1373{
1374 int retry = 1;
1375 int nr_failed = 0;
1376 int nr_succeeded = 0;
1377 int pass = 0;
1378 struct page *page;
1379 struct page *page2;
1380 int swapwrite = current->flags & PF_SWAPWRITE;
1381 int rc;
1382
1383 if (!swapwrite)
1384 current->flags |= PF_SWAPWRITE;
1385
1386 for(pass = 0; pass < 10 && retry; pass++) {
1387 retry = 0;
1388
1389 list_for_each_entry_safe(page, page2, from, lru) {
1390retry:
1391 cond_resched();
1392
1393 if (PageHuge(page))
1394 rc = unmap_and_move_huge_page(get_new_page,
1395 put_new_page, private, page,
1396 pass > 2, mode, reason);
1397 else
1398 rc = unmap_and_move(get_new_page, put_new_page,
1399 private, page, pass > 2, mode,
1400 reason);
1401
1402 switch(rc) {
1403 case -ENOMEM:
1404 /*
1405 * THP migration might be unsupported or the
1406 * allocation could've failed so we should
1407 * retry on the same page with the THP split
1408 * to base pages.
1409 *
1410 * Head page is retried immediately and tail
1411 * pages are added to the tail of the list so
1412 * we encounter them after the rest of the list
1413 * is processed.
1414 */
1415 if (PageTransHuge(page)) {
1416 lock_page(page);
1417 rc = split_huge_page_to_list(page, from);
1418 unlock_page(page);
1419 if (!rc) {
1420 list_safe_reset_next(page, page2, lru);
1421 goto retry;
1422 }
1423 }
1424 nr_failed++;
1425 goto out;
1426 case -EAGAIN:
1427 retry++;
1428 break;
1429 case MIGRATEPAGE_SUCCESS:
1430 nr_succeeded++;
1431 break;
1432 default:
1433 /*
1434 * Permanent failure (-EBUSY, -ENOSYS, etc.):
1435 * unlike -EAGAIN case, the failed page is
1436 * removed from migration page list and not
1437 * retried in the next outer loop.
1438 */
1439 nr_failed++;
1440 break;
1441 }
1442 }
1443 }
1444 nr_failed += retry;
1445 rc = nr_failed;
1446out:
1447 if (nr_succeeded)
1448 count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
1449 if (nr_failed)
1450 count_vm_events(PGMIGRATE_FAIL, nr_failed);
1451 trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason);
1452
1453 if (!swapwrite)
1454 current->flags &= ~PF_SWAPWRITE;
1455
1456 return rc;
1457}
1458
1459#ifdef CONFIG_NUMA
1460
1461static int store_status(int __user *status, int start, int value, int nr)
1462{
1463 while (nr-- > 0) {
1464 if (put_user(value, status + start))
1465 return -EFAULT;
1466 start++;
1467 }
1468
1469 return 0;
1470}
1471
1472static int do_move_pages_to_node(struct mm_struct *mm,
1473 struct list_head *pagelist, int node)
1474{
1475 int err;
1476
1477 if (list_empty(pagelist))
1478 return 0;
1479
1480 err = migrate_pages(pagelist, alloc_new_node_page, NULL, node,
1481 MIGRATE_SYNC, MR_SYSCALL);
1482 if (err)
1483 putback_movable_pages(pagelist);
1484 return err;
1485}
1486
1487/*
1488 * Resolves the given address to a struct page, isolates it from the LRU and
1489 * puts it to the given pagelist.
1490 * Returns -errno if the page cannot be found/isolated or 0 when it has been
1491 * queued or the page doesn't need to be migrated because it is already on
1492 * the target node
1493 */
1494static int add_page_for_migration(struct mm_struct *mm, unsigned long addr,
1495 int node, struct list_head *pagelist, bool migrate_all)
1496{
1497 struct vm_area_struct *vma;
1498 struct page *page;
1499 unsigned int follflags;
1500 int err;
1501
1502 down_read(&mm->mmap_sem);
1503 err = -EFAULT;
1504 vma = find_vma(mm, addr);
1505 if (!vma || addr < vma->vm_start || !vma_migratable(vma))
1506 goto out;
1507
1508 /* FOLL_DUMP to ignore special (like zero) pages */
1509 follflags = FOLL_GET | FOLL_DUMP;
1510 page = follow_page(vma, addr, follflags);
1511
1512 err = PTR_ERR(page);
1513 if (IS_ERR(page))
1514 goto out;
1515
1516 err = -ENOENT;
1517 if (!page)
1518 goto out;
1519
1520 err = 0;
1521 if (page_to_nid(page) == node)
1522 goto out_putpage;
1523
1524 err = -EACCES;
1525 if (page_mapcount(page) > 1 && !migrate_all)
1526 goto out_putpage;
1527
1528 if (PageHuge(page)) {
1529 if (PageHead(page)) {
1530 isolate_huge_page(page, pagelist);
1531 err = 0;
1532 }
1533 } else {
1534 struct page *head;
1535
1536 head = compound_head(page);
1537 err = isolate_lru_page(head);
1538 if (err)
1539 goto out_putpage;
1540
1541 err = 0;
1542 list_add_tail(&head->lru, pagelist);
1543 mod_node_page_state(page_pgdat(head),
1544 NR_ISOLATED_ANON + page_is_file_cache(head),
1545 hpage_nr_pages(head));
1546 }
1547out_putpage:
1548 /*
1549 * Either remove the duplicate refcount from
1550 * isolate_lru_page() or drop the page ref if it was
1551 * not isolated.
1552 */
1553 put_page(page);
1554out:
1555 up_read(&mm->mmap_sem);
1556 return err;
1557}
1558
1559/*
1560 * Migrate an array of page address onto an array of nodes and fill
1561 * the corresponding array of status.
1562 */
1563static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
1564 unsigned long nr_pages,
1565 const void __user * __user *pages,
1566 const int __user *nodes,
1567 int __user *status, int flags)
1568{
1569 int current_node = NUMA_NO_NODE;
1570 LIST_HEAD(pagelist);
1571 int start, i;
1572 int err = 0, err1;
1573
1574 migrate_prep();
1575
1576 for (i = start = 0; i < nr_pages; i++) {
1577 const void __user *p;
1578 unsigned long addr;
1579 int node;
1580
1581 err = -EFAULT;
1582 if (get_user(p, pages + i))
1583 goto out_flush;
1584 if (get_user(node, nodes + i))
1585 goto out_flush;
1586 addr = (unsigned long)p;
1587
1588 err = -ENODEV;
1589 if (node < 0 || node >= MAX_NUMNODES)
1590 goto out_flush;
1591 if (!node_state(node, N_MEMORY))
1592 goto out_flush;
1593
1594 err = -EACCES;
1595 if (!node_isset(node, task_nodes))
1596 goto out_flush;
1597
1598 if (current_node == NUMA_NO_NODE) {
1599 current_node = node;
1600 start = i;
1601 } else if (node != current_node) {
1602 err = do_move_pages_to_node(mm, &pagelist, current_node);
1603 if (err)
1604 goto out;
1605 err = store_status(status, start, current_node, i - start);
1606 if (err)
1607 goto out;
1608 start = i;
1609 current_node = node;
1610 }
1611
1612 /*
1613 * Errors in the page lookup or isolation are not fatal and we simply
1614 * report them via status
1615 */
1616 err = add_page_for_migration(mm, addr, current_node,
1617 &pagelist, flags & MPOL_MF_MOVE_ALL);
1618 if (!err)
1619 continue;
1620
1621 err = store_status(status, i, err, 1);
1622 if (err)
1623 goto out_flush;
1624
1625 err = do_move_pages_to_node(mm, &pagelist, current_node);
1626 if (err)
1627 goto out;
1628 if (i > start) {
1629 err = store_status(status, start, current_node, i - start);
1630 if (err)
1631 goto out;
1632 }
1633 current_node = NUMA_NO_NODE;
1634 }
1635out_flush:
1636 if (list_empty(&pagelist))
1637 return err;
1638
1639 /* Make sure we do not overwrite the existing error */
1640 err1 = do_move_pages_to_node(mm, &pagelist, current_node);
1641 if (!err1)
1642 err1 = store_status(status, start, current_node, i - start);
1643 if (!err)
1644 err = err1;
1645out:
1646 return err;
1647}
1648
1649/*
1650 * Determine the nodes of an array of pages and store it in an array of status.
1651 */
1652static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
1653 const void __user **pages, int *status)
1654{
1655 unsigned long i;
1656
1657 down_read(&mm->mmap_sem);
1658
1659 for (i = 0; i < nr_pages; i++) {
1660 unsigned long addr = (unsigned long)(*pages);
1661 struct vm_area_struct *vma;
1662 struct page *page;
1663 int err = -EFAULT;
1664
1665 vma = find_vma(mm, addr);
1666 if (!vma || addr < vma->vm_start)
1667 goto set_status;
1668
1669 /* FOLL_DUMP to ignore special (like zero) pages */
1670 page = follow_page(vma, addr, FOLL_DUMP);
1671
1672 err = PTR_ERR(page);
1673 if (IS_ERR(page))
1674 goto set_status;
1675
1676 err = page ? page_to_nid(page) : -ENOENT;
1677set_status:
1678 *status = err;
1679
1680 pages++;
1681 status++;
1682 }
1683
1684 up_read(&mm->mmap_sem);
1685}
1686
1687/*
1688 * Determine the nodes of a user array of pages and store it in
1689 * a user array of status.
1690 */
1691static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
1692 const void __user * __user *pages,
1693 int __user *status)
1694{
1695#define DO_PAGES_STAT_CHUNK_NR 16
1696 const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
1697 int chunk_status[DO_PAGES_STAT_CHUNK_NR];
1698
1699 while (nr_pages) {
1700 unsigned long chunk_nr;
1701
1702 chunk_nr = nr_pages;
1703 if (chunk_nr > DO_PAGES_STAT_CHUNK_NR)
1704 chunk_nr = DO_PAGES_STAT_CHUNK_NR;
1705
1706 if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages)))
1707 break;
1708
1709 do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
1710
1711 if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
1712 break;
1713
1714 pages += chunk_nr;
1715 status += chunk_nr;
1716 nr_pages -= chunk_nr;
1717 }
1718 return nr_pages ? -EFAULT : 0;
1719}
1720
1721/*
1722 * Move a list of pages in the address space of the currently executing
1723 * process.
1724 */
1725static int kernel_move_pages(pid_t pid, unsigned long nr_pages,
1726 const void __user * __user *pages,
1727 const int __user *nodes,
1728 int __user *status, int flags)
1729{
1730 struct task_struct *task;
1731 struct mm_struct *mm;
1732 int err;
1733 nodemask_t task_nodes;
1734
1735 /* Check flags */
1736 if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
1737 return -EINVAL;
1738
1739 if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
1740 return -EPERM;
1741
1742 /* Find the mm_struct */
1743 rcu_read_lock();
1744 task = pid ? find_task_by_vpid(pid) : current;
1745 if (!task) {
1746 rcu_read_unlock();
1747 return -ESRCH;
1748 }
1749 get_task_struct(task);
1750
1751 /*
1752 * Check if this process has the right to modify the specified
1753 * process. Use the regular "ptrace_may_access()" checks.
1754 */
1755 if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
1756 rcu_read_unlock();
1757 err = -EPERM;
1758 goto out;
1759 }
1760 rcu_read_unlock();
1761
1762 err = security_task_movememory(task);
1763 if (err)
1764 goto out;
1765
1766 task_nodes = cpuset_mems_allowed(task);
1767 mm = get_task_mm(task);
1768 put_task_struct(task);
1769
1770 if (!mm)
1771 return -EINVAL;
1772
1773 if (nodes)
1774 err = do_pages_move(mm, task_nodes, nr_pages, pages,
1775 nodes, status, flags);
1776 else
1777 err = do_pages_stat(mm, nr_pages, pages, status);
1778
1779 mmput(mm);
1780 return err;
1781
1782out:
1783 put_task_struct(task);
1784 return err;
1785}
1786
1787SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
1788 const void __user * __user *, pages,
1789 const int __user *, nodes,
1790 int __user *, status, int, flags)
1791{
1792 return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags);
1793}
1794
1795#ifdef CONFIG_COMPAT
1796COMPAT_SYSCALL_DEFINE6(move_pages, pid_t, pid, compat_ulong_t, nr_pages,
1797 compat_uptr_t __user *, pages32,
1798 const int __user *, nodes,
1799 int __user *, status,
1800 int, flags)
1801{
1802 const void __user * __user *pages;
1803 int i;
1804
1805 pages = compat_alloc_user_space(nr_pages * sizeof(void *));
1806 for (i = 0; i < nr_pages; i++) {
1807 compat_uptr_t p;
1808
1809 if (get_user(p, pages32 + i) ||
1810 put_user(compat_ptr(p), pages + i))
1811 return -EFAULT;
1812 }
1813 return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags);
1814}
1815#endif /* CONFIG_COMPAT */
1816
1817#ifdef CONFIG_NUMA_BALANCING
1818/*
1819 * Returns true if this is a safe migration target node for misplaced NUMA
1820 * pages. Currently it only checks the watermarks which crude
1821 */
1822static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
1823 unsigned long nr_migrate_pages)
1824{
1825 int z;
1826
1827 for (z = pgdat->nr_zones - 1; z >= 0; z--) {
1828 struct zone *zone = pgdat->node_zones + z;
1829
1830 if (!populated_zone(zone))
1831 continue;
1832
1833 /* Avoid waking kswapd by allocating pages_to_migrate pages. */
1834 if (!zone_watermark_ok(zone, 0,
1835 high_wmark_pages(zone) +
1836 nr_migrate_pages,
1837 0, 0))
1838 continue;
1839 return true;
1840 }
1841 return false;
1842}
1843
1844static struct page *alloc_misplaced_dst_page(struct page *page,
1845 unsigned long data)
1846{
1847 int nid = (int) data;
1848 struct page *newpage;
1849
1850 newpage = __alloc_pages_node(nid,
1851 (GFP_HIGHUSER_MOVABLE |
1852 __GFP_THISNODE | __GFP_NOMEMALLOC |
1853 __GFP_NORETRY | __GFP_NOWARN) &
1854 ~__GFP_RECLAIM, 0);
1855
1856 return newpage;
1857}
1858
1859/*
1860 * page migration rate limiting control.
1861 * Do not migrate more than @pages_to_migrate in a @migrate_interval_millisecs
1862 * window of time. Default here says do not migrate more than 1280M per second.
1863 */
1864static unsigned int migrate_interval_millisecs __read_mostly = 100;
1865static unsigned int ratelimit_pages __read_mostly = 128 << (20 - PAGE_SHIFT);
1866
1867/* Returns true if the node is migrate rate-limited after the update */
1868static bool numamigrate_update_ratelimit(pg_data_t *pgdat,
1869 unsigned long nr_pages)
1870{
1871 /*
1872 * Rate-limit the amount of data that is being migrated to a node.
1873 * Optimal placement is no good if the memory bus is saturated and
1874 * all the time is being spent migrating!
1875 */
1876 if (time_after(jiffies, pgdat->numabalancing_migrate_next_window)) {
1877 spin_lock(&pgdat->numabalancing_migrate_lock);
1878 pgdat->numabalancing_migrate_nr_pages = 0;
1879 pgdat->numabalancing_migrate_next_window = jiffies +
1880 msecs_to_jiffies(migrate_interval_millisecs);
1881 spin_unlock(&pgdat->numabalancing_migrate_lock);
1882 }
1883 if (pgdat->numabalancing_migrate_nr_pages > ratelimit_pages) {
1884 trace_mm_numa_migrate_ratelimit(current, pgdat->node_id,
1885 nr_pages);
1886 return true;
1887 }
1888
1889 /*
1890 * This is an unlocked non-atomic update so errors are possible.
1891 * The consequences are failing to migrate when we potentiall should
1892 * have which is not severe enough to warrant locking. If it is ever
1893 * a problem, it can be converted to a per-cpu counter.
1894 */
1895 pgdat->numabalancing_migrate_nr_pages += nr_pages;
1896 return false;
1897}
1898
1899static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
1900{
1901 int page_lru;
1902
1903 VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page);
1904
1905 /* Avoid migrating to a node that is nearly full */
1906 if (!migrate_balanced_pgdat(pgdat, 1UL << compound_order(page)))
1907 return 0;
1908
1909 if (isolate_lru_page(page))
1910 return 0;
1911
1912 /*
1913 * migrate_misplaced_transhuge_page() skips page migration's usual
1914 * check on page_count(), so we must do it here, now that the page
1915 * has been isolated: a GUP pin, or any other pin, prevents migration.
1916 * The expected page count is 3: 1 for page's mapcount and 1 for the
1917 * caller's pin and 1 for the reference taken by isolate_lru_page().
1918 */
1919 if (PageTransHuge(page) && page_count(page) != 3) {
1920 putback_lru_page(page);
1921 return 0;
1922 }
1923
1924 page_lru = page_is_file_cache(page);
1925 mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_lru,
1926 hpage_nr_pages(page));
1927
1928 /*
1929 * Isolating the page has taken another reference, so the
1930 * caller's reference can be safely dropped without the page
1931 * disappearing underneath us during migration.
1932 */
1933 put_page(page);
1934 return 1;
1935}
1936
1937bool pmd_trans_migrating(pmd_t pmd)
1938{
1939 struct page *page = pmd_page(pmd);
1940 return PageLocked(page);
1941}
1942
1943/*
1944 * Attempt to migrate a misplaced page to the specified destination
1945 * node. Caller is expected to have an elevated reference count on
1946 * the page that will be dropped by this function before returning.
1947 */
1948int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
1949 int node)
1950{
1951 pg_data_t *pgdat = NODE_DATA(node);
1952 int isolated;
1953 int nr_remaining;
1954 LIST_HEAD(migratepages);
1955
1956 /*
1957 * Don't migrate file pages that are mapped in multiple processes
1958 * with execute permissions as they are probably shared libraries.
1959 */
1960 if (page_mapcount(page) != 1 && page_is_file_cache(page) &&
1961 (vma->vm_flags & VM_EXEC))
1962 goto out;
1963
1964 /*
1965 * Also do not migrate dirty pages as not all filesystems can move
1966 * dirty pages in MIGRATE_ASYNC mode which is a waste of cycles.
1967 */
1968 if (page_is_file_cache(page) && PageDirty(page))
1969 goto out;
1970
1971 /*
1972 * Rate-limit the amount of data that is being migrated to a node.
1973 * Optimal placement is no good if the memory bus is saturated and
1974 * all the time is being spent migrating!
1975 */
1976 if (numamigrate_update_ratelimit(pgdat, 1))
1977 goto out;
1978
1979 isolated = numamigrate_isolate_page(pgdat, page);
1980 if (!isolated)
1981 goto out;
1982
1983 list_add(&page->lru, &migratepages);
1984 nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page,
1985 NULL, node, MIGRATE_ASYNC,
1986 MR_NUMA_MISPLACED);
1987 if (nr_remaining) {
1988 if (!list_empty(&migratepages)) {
1989 list_del(&page->lru);
1990 dec_node_page_state(page, NR_ISOLATED_ANON +
1991 page_is_file_cache(page));
1992 putback_lru_page(page);
1993 }
1994 isolated = 0;
1995 } else
1996 count_vm_numa_event(NUMA_PAGE_MIGRATE);
1997 BUG_ON(!list_empty(&migratepages));
1998 return isolated;
1999
2000out:
2001 put_page(page);
2002 return 0;
2003}
2004#endif /* CONFIG_NUMA_BALANCING */
2005
2006#if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
2007/*
2008 * Migrates a THP to a given target node. page must be locked and is unlocked
2009 * before returning.
2010 */
2011int migrate_misplaced_transhuge_page(struct mm_struct *mm,
2012 struct vm_area_struct *vma,
2013 pmd_t *pmd, pmd_t entry,
2014 unsigned long address,
2015 struct page *page, int node)
2016{
2017 spinlock_t *ptl;
2018 pg_data_t *pgdat = NODE_DATA(node);
2019 int isolated = 0;
2020 struct page *new_page = NULL;
2021 int page_lru = page_is_file_cache(page);
2022 unsigned long mmun_start = address & HPAGE_PMD_MASK;
2023 unsigned long mmun_end = mmun_start + HPAGE_PMD_SIZE;
2024
2025 /*
2026 * Rate-limit the amount of data that is being migrated to a node.
2027 * Optimal placement is no good if the memory bus is saturated and
2028 * all the time is being spent migrating!
2029 */
2030 if (numamigrate_update_ratelimit(pgdat, HPAGE_PMD_NR))
2031 goto out_dropref;
2032
2033 new_page = alloc_pages_node(node,
2034 (GFP_TRANSHUGE_LIGHT | __GFP_THISNODE),
2035 HPAGE_PMD_ORDER);
2036 if (!new_page)
2037 goto out_fail;
2038 prep_transhuge_page(new_page);
2039
2040 isolated = numamigrate_isolate_page(pgdat, page);
2041 if (!isolated) {
2042 put_page(new_page);
2043 goto out_fail;
2044 }
2045
2046 /* Prepare a page as a migration target */
2047 __SetPageLocked(new_page);
2048 if (PageSwapBacked(page))
2049 __SetPageSwapBacked(new_page);
2050
2051 /* anon mapping, we can simply copy page->mapping to the new page: */
2052 new_page->mapping = page->mapping;
2053 new_page->index = page->index;
2054 migrate_page_copy(new_page, page);
2055 WARN_ON(PageLRU(new_page));
2056
2057 /* Recheck the target PMD */
2058 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2059 ptl = pmd_lock(mm, pmd);
2060 if (unlikely(!pmd_same(*pmd, entry) || !page_ref_freeze(page, 2))) {
2061 spin_unlock(ptl);
2062 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2063
2064 /* Reverse changes made by migrate_page_copy() */
2065 if (TestClearPageActive(new_page))
2066 SetPageActive(page);
2067 if (TestClearPageUnevictable(new_page))
2068 SetPageUnevictable(page);
2069
2070 unlock_page(new_page);
2071 put_page(new_page); /* Free it */
2072
2073 /* Retake the callers reference and putback on LRU */
2074 get_page(page);
2075 putback_lru_page(page);
2076 mod_node_page_state(page_pgdat(page),
2077 NR_ISOLATED_ANON + page_lru, -HPAGE_PMD_NR);
2078
2079 goto out_unlock;
2080 }
2081
2082 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
2083 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
2084
2085 /*
2086 * Clear the old entry under pagetable lock and establish the new PTE.
2087 * Any parallel GUP will either observe the old page blocking on the
2088 * page lock, block on the page table lock or observe the new page.
2089 * The SetPageUptodate on the new page and page_add_new_anon_rmap
2090 * guarantee the copy is visible before the pagetable update.
2091 */
2092 flush_cache_range(vma, mmun_start, mmun_end);
2093 page_add_anon_rmap(new_page, vma, mmun_start, true);
2094 pmdp_huge_clear_flush_notify(vma, mmun_start, pmd);
2095 set_pmd_at(mm, mmun_start, pmd, entry);
2096 update_mmu_cache_pmd(vma, address, &entry);
2097
2098 page_ref_unfreeze(page, 2);
2099 mlock_migrate_page(new_page, page);
2100 page_remove_rmap(page, true);
2101 set_page_owner_migrate_reason(new_page, MR_NUMA_MISPLACED);
2102
2103 spin_unlock(ptl);
2104 /*
2105 * No need to double call mmu_notifier->invalidate_range() callback as
2106 * the above pmdp_huge_clear_flush_notify() did already call it.
2107 */
2108 mmu_notifier_invalidate_range_only_end(mm, mmun_start, mmun_end);
2109
2110 /* Take an "isolate" reference and put new page on the LRU. */
2111 get_page(new_page);
2112 putback_lru_page(new_page);
2113
2114 unlock_page(new_page);
2115 unlock_page(page);
2116 put_page(page); /* Drop the rmap reference */
2117 put_page(page); /* Drop the LRU isolation reference */
2118
2119 count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR);
2120 count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR);
2121
2122 mod_node_page_state(page_pgdat(page),
2123 NR_ISOLATED_ANON + page_lru,
2124 -HPAGE_PMD_NR);
2125 return isolated;
2126
2127out_fail:
2128 count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
2129out_dropref:
2130 ptl = pmd_lock(mm, pmd);
2131 if (pmd_same(*pmd, entry)) {
2132 entry = pmd_modify(entry, vma->vm_page_prot);
2133 set_pmd_at(mm, mmun_start, pmd, entry);
2134 update_mmu_cache_pmd(vma, address, &entry);
2135 }
2136 spin_unlock(ptl);
2137
2138out_unlock:
2139 unlock_page(page);
2140 put_page(page);
2141 return 0;
2142}
2143#endif /* CONFIG_NUMA_BALANCING */
2144
2145#endif /* CONFIG_NUMA */
2146
2147#if defined(CONFIG_MIGRATE_VMA_HELPER)
2148struct migrate_vma {
2149 struct vm_area_struct *vma;
2150 unsigned long *dst;
2151 unsigned long *src;
2152 unsigned long cpages;
2153 unsigned long npages;
2154 unsigned long start;
2155 unsigned long end;
2156};
2157
2158static int migrate_vma_collect_hole(unsigned long start,
2159 unsigned long end,
2160 struct mm_walk *walk)
2161{
2162 struct migrate_vma *migrate = walk->private;
2163 unsigned long addr;
2164
2165 for (addr = start & PAGE_MASK; addr < end; addr += PAGE_SIZE) {
2166 migrate->src[migrate->npages] = MIGRATE_PFN_MIGRATE;
2167 migrate->dst[migrate->npages] = 0;
2168 migrate->npages++;
2169 migrate->cpages++;
2170 }
2171
2172 return 0;
2173}
2174
2175static int migrate_vma_collect_skip(unsigned long start,
2176 unsigned long end,
2177 struct mm_walk *walk)
2178{
2179 struct migrate_vma *migrate = walk->private;
2180 unsigned long addr;
2181
2182 for (addr = start & PAGE_MASK; addr < end; addr += PAGE_SIZE) {
2183 migrate->dst[migrate->npages] = 0;
2184 migrate->src[migrate->npages++] = 0;
2185 }
2186
2187 return 0;
2188}
2189
2190static int migrate_vma_collect_pmd(pmd_t *pmdp,
2191 unsigned long start,
2192 unsigned long end,
2193 struct mm_walk *walk)
2194{
2195 struct migrate_vma *migrate = walk->private;
2196 struct vm_area_struct *vma = walk->vma;
2197 struct mm_struct *mm = vma->vm_mm;
2198 unsigned long addr = start, unmapped = 0;
2199 spinlock_t *ptl;
2200 pte_t *ptep;
2201
2202again:
2203 if (pmd_none(*pmdp))
2204 return migrate_vma_collect_hole(start, end, walk);
2205
2206 if (pmd_trans_huge(*pmdp)) {
2207 struct page *page;
2208
2209 ptl = pmd_lock(mm, pmdp);
2210 if (unlikely(!pmd_trans_huge(*pmdp))) {
2211 spin_unlock(ptl);
2212 goto again;
2213 }
2214
2215 page = pmd_page(*pmdp);
2216 if (is_huge_zero_page(page)) {
2217 spin_unlock(ptl);
2218 split_huge_pmd(vma, pmdp, addr);
2219 if (pmd_trans_unstable(pmdp))
2220 return migrate_vma_collect_skip(start, end,
2221 walk);
2222 } else {
2223 int ret;
2224
2225 get_page(page);
2226 spin_unlock(ptl);
2227 if (unlikely(!trylock_page(page)))
2228 return migrate_vma_collect_skip(start, end,
2229 walk);
2230 ret = split_huge_page(page);
2231 unlock_page(page);
2232 put_page(page);
2233 if (ret)
2234 return migrate_vma_collect_skip(start, end,
2235 walk);
2236 if (pmd_none(*pmdp))
2237 return migrate_vma_collect_hole(start, end,
2238 walk);
2239 }
2240 }
2241
2242 if (unlikely(pmd_bad(*pmdp)))
2243 return migrate_vma_collect_skip(start, end, walk);
2244
2245 ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
2246 arch_enter_lazy_mmu_mode();
2247
2248 for (; addr < end; addr += PAGE_SIZE, ptep++) {
2249 unsigned long mpfn, pfn;
2250 struct page *page;
2251 swp_entry_t entry;
2252 pte_t pte;
2253
2254 pte = *ptep;
2255 pfn = pte_pfn(pte);
2256
2257 if (pte_none(pte)) {
2258 mpfn = MIGRATE_PFN_MIGRATE;
2259 migrate->cpages++;
2260 pfn = 0;
2261 goto next;
2262 }
2263
2264 if (!pte_present(pte)) {
2265 mpfn = pfn = 0;
2266
2267 /*
2268 * Only care about unaddressable device page special
2269 * page table entry. Other special swap entries are not
2270 * migratable, and we ignore regular swapped page.
2271 */
2272 entry = pte_to_swp_entry(pte);
2273 if (!is_device_private_entry(entry))
2274 goto next;
2275
2276 page = device_private_entry_to_page(entry);
2277 mpfn = migrate_pfn(page_to_pfn(page))|
2278 MIGRATE_PFN_DEVICE | MIGRATE_PFN_MIGRATE;
2279 if (is_write_device_private_entry(entry))
2280 mpfn |= MIGRATE_PFN_WRITE;
2281 } else {
2282 if (is_zero_pfn(pfn)) {
2283 mpfn = MIGRATE_PFN_MIGRATE;
2284 migrate->cpages++;
2285 pfn = 0;
2286 goto next;
2287 }
2288 page = _vm_normal_page(migrate->vma, addr, pte, true);
2289 mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
2290 mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
2291 }
2292
2293 /* FIXME support THP */
2294 if (!page || !page->mapping || PageTransCompound(page)) {
2295 mpfn = pfn = 0;
2296 goto next;
2297 }
2298 pfn = page_to_pfn(page);
2299
2300 /*
2301 * By getting a reference on the page we pin it and that blocks
2302 * any kind of migration. Side effect is that it "freezes" the
2303 * pte.
2304 *
2305 * We drop this reference after isolating the page from the lru
2306 * for non device page (device page are not on the lru and thus
2307 * can't be dropped from it).
2308 */
2309 get_page(page);
2310 migrate->cpages++;
2311
2312 /*
2313 * Optimize for the common case where page is only mapped once
2314 * in one process. If we can lock the page, then we can safely
2315 * set up a special migration page table entry now.
2316 */
2317 if (trylock_page(page)) {
2318 pte_t swp_pte;
2319
2320 mpfn |= MIGRATE_PFN_LOCKED;
2321 ptep_get_and_clear(mm, addr, ptep);
2322
2323 /* Setup special migration page table entry */
2324 entry = make_migration_entry(page, mpfn &
2325 MIGRATE_PFN_WRITE);
2326 swp_pte = swp_entry_to_pte(entry);
2327 if (pte_soft_dirty(pte))
2328 swp_pte = pte_swp_mksoft_dirty(swp_pte);
2329 set_pte_at(mm, addr, ptep, swp_pte);
2330
2331 /*
2332 * This is like regular unmap: we remove the rmap and
2333 * drop page refcount. Page won't be freed, as we took
2334 * a reference just above.
2335 */
2336 page_remove_rmap(page, false);
2337 put_page(page);
2338
2339 if (pte_present(pte))
2340 unmapped++;
2341 }
2342
2343next:
2344 migrate->dst[migrate->npages] = 0;
2345 migrate->src[migrate->npages++] = mpfn;
2346 }
2347 arch_leave_lazy_mmu_mode();
2348 pte_unmap_unlock(ptep - 1, ptl);
2349
2350 /* Only flush the TLB if we actually modified any entries */
2351 if (unmapped)
2352 flush_tlb_range(walk->vma, start, end);
2353
2354 return 0;
2355}
2356
2357/*
2358 * migrate_vma_collect() - collect pages over a range of virtual addresses
2359 * @migrate: migrate struct containing all migration information
2360 *
2361 * This will walk the CPU page table. For each virtual address backed by a
2362 * valid page, it updates the src array and takes a reference on the page, in
2363 * order to pin the page until we lock it and unmap it.
2364 */
2365static void migrate_vma_collect(struct migrate_vma *migrate)
2366{
2367 struct mm_walk mm_walk;
2368
2369 mm_walk.pmd_entry = migrate_vma_collect_pmd;
2370 mm_walk.pte_entry = NULL;
2371 mm_walk.pte_hole = migrate_vma_collect_hole;
2372 mm_walk.hugetlb_entry = NULL;
2373 mm_walk.test_walk = NULL;
2374 mm_walk.vma = migrate->vma;
2375 mm_walk.mm = migrate->vma->vm_mm;
2376 mm_walk.private = migrate;
2377
2378 mmu_notifier_invalidate_range_start(mm_walk.mm,
2379 migrate->start,
2380 migrate->end);
2381 walk_page_range(migrate->start, migrate->end, &mm_walk);
2382 mmu_notifier_invalidate_range_end(mm_walk.mm,
2383 migrate->start,
2384 migrate->end);
2385
2386 migrate->end = migrate->start + (migrate->npages << PAGE_SHIFT);
2387}
2388
2389/*
2390 * migrate_vma_check_page() - check if page is pinned or not
2391 * @page: struct page to check
2392 *
2393 * Pinned pages cannot be migrated. This is the same test as in
2394 * migrate_page_move_mapping(), except that here we allow migration of a
2395 * ZONE_DEVICE page.
2396 */
2397static bool migrate_vma_check_page(struct page *page)
2398{
2399 /*
2400 * One extra ref because caller holds an extra reference, either from
2401 * isolate_lru_page() for a regular page, or migrate_vma_collect() for
2402 * a device page.
2403 */
2404 int extra = 1;
2405
2406 /*
2407 * FIXME support THP (transparent huge page), it is bit more complex to
2408 * check them than regular pages, because they can be mapped with a pmd
2409 * or with a pte (split pte mapping).
2410 */
2411 if (PageCompound(page))
2412 return false;
2413
2414 /* Page from ZONE_DEVICE have one extra reference */
2415 if (is_zone_device_page(page)) {
2416 /*
2417 * Private page can never be pin as they have no valid pte and
2418 * GUP will fail for those. Yet if there is a pending migration
2419 * a thread might try to wait on the pte migration entry and
2420 * will bump the page reference count. Sadly there is no way to
2421 * differentiate a regular pin from migration wait. Hence to
2422 * avoid 2 racing thread trying to migrate back to CPU to enter
2423 * infinite loop (one stoping migration because the other is
2424 * waiting on pte migration entry). We always return true here.
2425 *
2426 * FIXME proper solution is to rework migration_entry_wait() so
2427 * it does not need to take a reference on page.
2428 */
2429 if (is_device_private_page(page))
2430 return true;
2431
2432 /*
2433 * Only allow device public page to be migrated and account for
2434 * the extra reference count imply by ZONE_DEVICE pages.
2435 */
2436 if (!is_device_public_page(page))
2437 return false;
2438 extra++;
2439 }
2440
2441 /* For file back page */
2442 if (page_mapping(page))
2443 extra += 1 + page_has_private(page);
2444
2445 if ((page_count(page) - extra) > page_mapcount(page))
2446 return false;
2447
2448 return true;
2449}
2450
2451/*
2452 * migrate_vma_prepare() - lock pages and isolate them from the lru
2453 * @migrate: migrate struct containing all migration information
2454 *
2455 * This locks pages that have been collected by migrate_vma_collect(). Once each
2456 * page is locked it is isolated from the lru (for non-device pages). Finally,
2457 * the ref taken by migrate_vma_collect() is dropped, as locked pages cannot be
2458 * migrated by concurrent kernel threads.
2459 */
2460static void migrate_vma_prepare(struct migrate_vma *migrate)
2461{
2462 const unsigned long npages = migrate->npages;
2463 const unsigned long start = migrate->start;
2464 unsigned long addr, i, restore = 0;
2465 bool allow_drain = true;
2466
2467 lru_add_drain();
2468
2469 for (i = 0; (i < npages) && migrate->cpages; i++) {
2470 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2471 bool remap = true;
2472
2473 if (!page)
2474 continue;
2475
2476 if (!(migrate->src[i] & MIGRATE_PFN_LOCKED)) {
2477 /*
2478 * Because we are migrating several pages there can be
2479 * a deadlock between 2 concurrent migration where each
2480 * are waiting on each other page lock.
2481 *
2482 * Make migrate_vma() a best effort thing and backoff
2483 * for any page we can not lock right away.
2484 */
2485 if (!trylock_page(page)) {
2486 migrate->src[i] = 0;
2487 migrate->cpages--;
2488 put_page(page);
2489 continue;
2490 }
2491 remap = false;
2492 migrate->src[i] |= MIGRATE_PFN_LOCKED;
2493 }
2494
2495 /* ZONE_DEVICE pages are not on LRU */
2496 if (!is_zone_device_page(page)) {
2497 if (!PageLRU(page) && allow_drain) {
2498 /* Drain CPU's pagevec */
2499 lru_add_drain_all();
2500 allow_drain = false;
2501 }
2502
2503 if (isolate_lru_page(page)) {
2504 if (remap) {
2505 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2506 migrate->cpages--;
2507 restore++;
2508 } else {
2509 migrate->src[i] = 0;
2510 unlock_page(page);
2511 migrate->cpages--;
2512 put_page(page);
2513 }
2514 continue;
2515 }
2516
2517 /* Drop the reference we took in collect */
2518 put_page(page);
2519 }
2520
2521 if (!migrate_vma_check_page(page)) {
2522 if (remap) {
2523 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2524 migrate->cpages--;
2525 restore++;
2526
2527 if (!is_zone_device_page(page)) {
2528 get_page(page);
2529 putback_lru_page(page);
2530 }
2531 } else {
2532 migrate->src[i] = 0;
2533 unlock_page(page);
2534 migrate->cpages--;
2535
2536 if (!is_zone_device_page(page))
2537 putback_lru_page(page);
2538 else
2539 put_page(page);
2540 }
2541 }
2542 }
2543
2544 for (i = 0, addr = start; i < npages && restore; i++, addr += PAGE_SIZE) {
2545 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2546
2547 if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE))
2548 continue;
2549
2550 remove_migration_pte(page, migrate->vma, addr, page);
2551
2552 migrate->src[i] = 0;
2553 unlock_page(page);
2554 put_page(page);
2555 restore--;
2556 }
2557}
2558
2559/*
2560 * migrate_vma_unmap() - replace page mapping with special migration pte entry
2561 * @migrate: migrate struct containing all migration information
2562 *
2563 * Replace page mapping (CPU page table pte) with a special migration pte entry
2564 * and check again if it has been pinned. Pinned pages are restored because we
2565 * cannot migrate them.
2566 *
2567 * This is the last step before we call the device driver callback to allocate
2568 * destination memory and copy contents of original page over to new page.
2569 */
2570static void migrate_vma_unmap(struct migrate_vma *migrate)
2571{
2572 int flags = TTU_MIGRATION | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
2573 const unsigned long npages = migrate->npages;
2574 const unsigned long start = migrate->start;
2575 unsigned long addr, i, restore = 0;
2576
2577 for (i = 0; i < npages; i++) {
2578 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2579
2580 if (!page || !(migrate->src[i] & MIGRATE_PFN_MIGRATE))
2581 continue;
2582
2583 if (page_mapped(page)) {
2584 try_to_unmap(page, flags);
2585 if (page_mapped(page))
2586 goto restore;
2587 }
2588
2589 if (migrate_vma_check_page(page))
2590 continue;
2591
2592restore:
2593 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2594 migrate->cpages--;
2595 restore++;
2596 }
2597
2598 for (addr = start, i = 0; i < npages && restore; addr += PAGE_SIZE, i++) {
2599 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2600
2601 if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE))
2602 continue;
2603
2604 remove_migration_ptes(page, page, false);
2605
2606 migrate->src[i] = 0;
2607 unlock_page(page);
2608 restore--;
2609
2610 if (is_zone_device_page(page))
2611 put_page(page);
2612 else
2613 putback_lru_page(page);
2614 }
2615}
2616
2617static void migrate_vma_insert_page(struct migrate_vma *migrate,
2618 unsigned long addr,
2619 struct page *page,
2620 unsigned long *src,
2621 unsigned long *dst)
2622{
2623 struct vm_area_struct *vma = migrate->vma;
2624 struct mm_struct *mm = vma->vm_mm;
2625 struct mem_cgroup *memcg;
2626 bool flush = false;
2627 spinlock_t *ptl;
2628 pte_t entry;
2629 pgd_t *pgdp;
2630 p4d_t *p4dp;
2631 pud_t *pudp;
2632 pmd_t *pmdp;
2633 pte_t *ptep;
2634
2635 /* Only allow populating anonymous memory */
2636 if (!vma_is_anonymous(vma))
2637 goto abort;
2638
2639 pgdp = pgd_offset(mm, addr);
2640 p4dp = p4d_alloc(mm, pgdp, addr);
2641 if (!p4dp)
2642 goto abort;
2643 pudp = pud_alloc(mm, p4dp, addr);
2644 if (!pudp)
2645 goto abort;
2646 pmdp = pmd_alloc(mm, pudp, addr);
2647 if (!pmdp)
2648 goto abort;
2649
2650 if (pmd_trans_huge(*pmdp) || pmd_devmap(*pmdp))
2651 goto abort;
2652
2653 /*
2654 * Use pte_alloc() instead of pte_alloc_map(). We can't run
2655 * pte_offset_map() on pmds where a huge pmd might be created
2656 * from a different thread.
2657 *
2658 * pte_alloc_map() is safe to use under down_write(mmap_sem) or when
2659 * parallel threads are excluded by other means.
2660 *
2661 * Here we only have down_read(mmap_sem).
2662 */
2663 if (pte_alloc(mm, pmdp, addr))
2664 goto abort;
2665
2666 /* See the comment in pte_alloc_one_map() */
2667 if (unlikely(pmd_trans_unstable(pmdp)))
2668 goto abort;
2669
2670 if (unlikely(anon_vma_prepare(vma)))
2671 goto abort;
2672 if (mem_cgroup_try_charge(page, vma->vm_mm, GFP_KERNEL, &memcg, false))
2673 goto abort;
2674
2675 /*
2676 * The memory barrier inside __SetPageUptodate makes sure that
2677 * preceding stores to the page contents become visible before
2678 * the set_pte_at() write.
2679 */
2680 __SetPageUptodate(page);
2681
2682 if (is_zone_device_page(page)) {
2683 if (is_device_private_page(page)) {
2684 swp_entry_t swp_entry;
2685
2686 swp_entry = make_device_private_entry(page, vma->vm_flags & VM_WRITE);
2687 entry = swp_entry_to_pte(swp_entry);
2688 } else if (is_device_public_page(page)) {
2689 entry = pte_mkold(mk_pte(page, READ_ONCE(vma->vm_page_prot)));
2690 if (vma->vm_flags & VM_WRITE)
2691 entry = pte_mkwrite(pte_mkdirty(entry));
2692 entry = pte_mkdevmap(entry);
2693 }
2694 } else {
2695 entry = mk_pte(page, vma->vm_page_prot);
2696 if (vma->vm_flags & VM_WRITE)
2697 entry = pte_mkwrite(pte_mkdirty(entry));
2698 }
2699
2700 ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
2701
2702 if (pte_present(*ptep)) {
2703 unsigned long pfn = pte_pfn(*ptep);
2704
2705 if (!is_zero_pfn(pfn)) {
2706 pte_unmap_unlock(ptep, ptl);
2707 mem_cgroup_cancel_charge(page, memcg, false);
2708 goto abort;
2709 }
2710 flush = true;
2711 } else if (!pte_none(*ptep)) {
2712 pte_unmap_unlock(ptep, ptl);
2713 mem_cgroup_cancel_charge(page, memcg, false);
2714 goto abort;
2715 }
2716
2717 /*
2718 * Check for usefaultfd but do not deliver the fault. Instead,
2719 * just back off.
2720 */
2721 if (userfaultfd_missing(vma)) {
2722 pte_unmap_unlock(ptep, ptl);
2723 mem_cgroup_cancel_charge(page, memcg, false);
2724 goto abort;
2725 }
2726
2727 inc_mm_counter(mm, MM_ANONPAGES);
2728 page_add_new_anon_rmap(page, vma, addr, false);
2729 mem_cgroup_commit_charge(page, memcg, false, false);
2730 if (!is_zone_device_page(page))
2731 lru_cache_add_active_or_unevictable(page, vma);
2732 get_page(page);
2733
2734 if (flush) {
2735 flush_cache_page(vma, addr, pte_pfn(*ptep));
2736 ptep_clear_flush_notify(vma, addr, ptep);
2737 set_pte_at_notify(mm, addr, ptep, entry);
2738 update_mmu_cache(vma, addr, ptep);
2739 } else {
2740 /* No need to invalidate - it was non-present before */
2741 set_pte_at(mm, addr, ptep, entry);
2742 update_mmu_cache(vma, addr, ptep);
2743 }
2744
2745 pte_unmap_unlock(ptep, ptl);
2746 *src = MIGRATE_PFN_MIGRATE;
2747 return;
2748
2749abort:
2750 *src &= ~MIGRATE_PFN_MIGRATE;
2751}
2752
2753/*
2754 * migrate_vma_pages() - migrate meta-data from src page to dst page
2755 * @migrate: migrate struct containing all migration information
2756 *
2757 * This migrates struct page meta-data from source struct page to destination
2758 * struct page. This effectively finishes the migration from source page to the
2759 * destination page.
2760 */
2761static void migrate_vma_pages(struct migrate_vma *migrate)
2762{
2763 const unsigned long npages = migrate->npages;
2764 const unsigned long start = migrate->start;
2765 struct vm_area_struct *vma = migrate->vma;
2766 struct mm_struct *mm = vma->vm_mm;
2767 unsigned long addr, i, mmu_start;
2768 bool notified = false;
2769
2770 for (i = 0, addr = start; i < npages; addr += PAGE_SIZE, i++) {
2771 struct page *newpage = migrate_pfn_to_page(migrate->dst[i]);
2772 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2773 struct address_space *mapping;
2774 int r;
2775
2776 if (!newpage) {
2777 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2778 continue;
2779 }
2780
2781 if (!page) {
2782 if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE)) {
2783 continue;
2784 }
2785 if (!notified) {
2786 mmu_start = addr;
2787 notified = true;
2788 mmu_notifier_invalidate_range_start(mm,
2789 mmu_start,
2790 migrate->end);
2791 }
2792 migrate_vma_insert_page(migrate, addr, newpage,
2793 &migrate->src[i],
2794 &migrate->dst[i]);
2795 continue;
2796 }
2797
2798 mapping = page_mapping(page);
2799
2800 if (is_zone_device_page(newpage)) {
2801 if (is_device_private_page(newpage)) {
2802 /*
2803 * For now only support private anonymous when
2804 * migrating to un-addressable device memory.
2805 */
2806 if (mapping) {
2807 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2808 continue;
2809 }
2810 } else if (!is_device_public_page(newpage)) {
2811 /*
2812 * Other types of ZONE_DEVICE page are not
2813 * supported.
2814 */
2815 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2816 continue;
2817 }
2818 }
2819
2820 r = migrate_page(mapping, newpage, page, MIGRATE_SYNC_NO_COPY);
2821 if (r != MIGRATEPAGE_SUCCESS)
2822 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2823 }
2824
2825 /*
2826 * No need to double call mmu_notifier->invalidate_range() callback as
2827 * the above ptep_clear_flush_notify() inside migrate_vma_insert_page()
2828 * did already call it.
2829 */
2830 if (notified)
2831 mmu_notifier_invalidate_range_only_end(mm, mmu_start,
2832 migrate->end);
2833}
2834
2835/*
2836 * migrate_vma_finalize() - restore CPU page table entry
2837 * @migrate: migrate struct containing all migration information
2838 *
2839 * This replaces the special migration pte entry with either a mapping to the
2840 * new page if migration was successful for that page, or to the original page
2841 * otherwise.
2842 *
2843 * This also unlocks the pages and puts them back on the lru, or drops the extra
2844 * refcount, for device pages.
2845 */
2846static void migrate_vma_finalize(struct migrate_vma *migrate)
2847{
2848 const unsigned long npages = migrate->npages;
2849 unsigned long i;
2850
2851 for (i = 0; i < npages; i++) {
2852 struct page *newpage = migrate_pfn_to_page(migrate->dst[i]);
2853 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2854
2855 if (!page) {
2856 if (newpage) {
2857 unlock_page(newpage);
2858 put_page(newpage);
2859 }
2860 continue;
2861 }
2862
2863 if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE) || !newpage) {
2864 if (newpage) {
2865 unlock_page(newpage);
2866 put_page(newpage);
2867 }
2868 newpage = page;
2869 }
2870
2871 remove_migration_ptes(page, newpage, false);
2872 unlock_page(page);
2873 migrate->cpages--;
2874
2875 if (is_zone_device_page(page))
2876 put_page(page);
2877 else
2878 putback_lru_page(page);
2879
2880 if (newpage != page) {
2881 unlock_page(newpage);
2882 if (is_zone_device_page(newpage))
2883 put_page(newpage);
2884 else
2885 putback_lru_page(newpage);
2886 }
2887 }
2888}
2889
2890/*
2891 * migrate_vma() - migrate a range of memory inside vma
2892 *
2893 * @ops: migration callback for allocating destination memory and copying
2894 * @vma: virtual memory area containing the range to be migrated
2895 * @start: start address of the range to migrate (inclusive)
2896 * @end: end address of the range to migrate (exclusive)
2897 * @src: array of hmm_pfn_t containing source pfns
2898 * @dst: array of hmm_pfn_t containing destination pfns
2899 * @private: pointer passed back to each of the callback
2900 * Returns: 0 on success, error code otherwise
2901 *
2902 * This function tries to migrate a range of memory virtual address range, using
2903 * callbacks to allocate and copy memory from source to destination. First it
2904 * collects all the pages backing each virtual address in the range, saving this
2905 * inside the src array. Then it locks those pages and unmaps them. Once the pages
2906 * are locked and unmapped, it checks whether each page is pinned or not. Pages
2907 * that aren't pinned have the MIGRATE_PFN_MIGRATE flag set (by this function)
2908 * in the corresponding src array entry. It then restores any pages that are
2909 * pinned, by remapping and unlocking those pages.
2910 *
2911 * At this point it calls the alloc_and_copy() callback. For documentation on
2912 * what is expected from that callback, see struct migrate_vma_ops comments in
2913 * include/linux/migrate.h
2914 *
2915 * After the alloc_and_copy() callback, this function goes over each entry in
2916 * the src array that has the MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag
2917 * set. If the corresponding entry in dst array has MIGRATE_PFN_VALID flag set,
2918 * then the function tries to migrate struct page information from the source
2919 * struct page to the destination struct page. If it fails to migrate the struct
2920 * page information, then it clears the MIGRATE_PFN_MIGRATE flag in the src
2921 * array.
2922 *
2923 * At this point all successfully migrated pages have an entry in the src
2924 * array with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag set and the dst
2925 * array entry with MIGRATE_PFN_VALID flag set.
2926 *
2927 * It then calls the finalize_and_map() callback. See comments for "struct
2928 * migrate_vma_ops", in include/linux/migrate.h for details about
2929 * finalize_and_map() behavior.
2930 *
2931 * After the finalize_and_map() callback, for successfully migrated pages, this
2932 * function updates the CPU page table to point to new pages, otherwise it
2933 * restores the CPU page table to point to the original source pages.
2934 *
2935 * Function returns 0 after the above steps, even if no pages were migrated
2936 * (The function only returns an error if any of the arguments are invalid.)
2937 *
2938 * Both src and dst array must be big enough for (end - start) >> PAGE_SHIFT
2939 * unsigned long entries.
2940 */
2941int migrate_vma(const struct migrate_vma_ops *ops,
2942 struct vm_area_struct *vma,
2943 unsigned long start,
2944 unsigned long end,
2945 unsigned long *src,
2946 unsigned long *dst,
2947 void *private)
2948{
2949 struct migrate_vma migrate;
2950
2951 /* Sanity check the arguments */
2952 start &= PAGE_MASK;
2953 end &= PAGE_MASK;
2954 if (!vma || is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL))
2955 return -EINVAL;
2956 if (start < vma->vm_start || start >= vma->vm_end)
2957 return -EINVAL;
2958 if (end <= vma->vm_start || end > vma->vm_end)
2959 return -EINVAL;
2960 if (!ops || !src || !dst || start >= end)
2961 return -EINVAL;
2962
2963 memset(src, 0, sizeof(*src) * ((end - start) >> PAGE_SHIFT));
2964 migrate.src = src;
2965 migrate.dst = dst;
2966 migrate.start = start;
2967 migrate.npages = 0;
2968 migrate.cpages = 0;
2969 migrate.end = end;
2970 migrate.vma = vma;
2971
2972 /* Collect, and try to unmap source pages */
2973 migrate_vma_collect(&migrate);
2974 if (!migrate.cpages)
2975 return 0;
2976
2977 /* Lock and isolate page */
2978 migrate_vma_prepare(&migrate);
2979 if (!migrate.cpages)
2980 return 0;
2981
2982 /* Unmap pages */
2983 migrate_vma_unmap(&migrate);
2984 if (!migrate.cpages)
2985 return 0;
2986
2987 /*
2988 * At this point pages are locked and unmapped, and thus they have
2989 * stable content and can safely be copied to destination memory that
2990 * is allocated by the callback.
2991 *
2992 * Note that migration can fail in migrate_vma_struct_page() for each
2993 * individual page.
2994 */
2995 ops->alloc_and_copy(vma, src, dst, start, end, private);
2996
2997 /* This does the real migration of struct page */
2998 migrate_vma_pages(&migrate);
2999
3000 ops->finalize_and_map(vma, src, dst, start, end, private);
3001
3002 /* Unlock and remap pages */
3003 migrate_vma_finalize(&migrate);
3004
3005 return 0;
3006}
3007EXPORT_SYMBOL(migrate_vma);
3008#endif /* defined(MIGRATE_VMA_HELPER) */
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/ksm.h>
24#include <linux/rmap.h>
25#include <linux/topology.h>
26#include <linux/cpu.h>
27#include <linux/cpuset.h>
28#include <linux/writeback.h>
29#include <linux/mempolicy.h>
30#include <linux/vmalloc.h>
31#include <linux/security.h>
32#include <linux/backing-dev.h>
33#include <linux/compaction.h>
34#include <linux/syscalls.h>
35#include <linux/compat.h>
36#include <linux/hugetlb.h>
37#include <linux/gfp.h>
38#include <linux/pfn_t.h>
39#include <linux/page_idle.h>
40#include <linux/page_owner.h>
41#include <linux/sched/mm.h>
42#include <linux/ptrace.h>
43#include <linux/memory.h>
44#include <linux/sched/sysctl.h>
45#include <linux/memory-tiers.h>
46#include <linux/pagewalk.h>
47
48#include <asm/tlbflush.h>
49
50#include <trace/events/migrate.h>
51
52#include "internal.h"
53
54bool isolate_movable_page(struct page *page, isolate_mode_t mode)
55{
56 struct folio *folio = folio_get_nontail_page(page);
57 const struct movable_operations *mops;
58
59 /*
60 * Avoid burning cycles with pages that are yet under __free_pages(),
61 * or just got freed under us.
62 *
63 * In case we 'win' a race for a movable page being freed under us and
64 * raise its refcount preventing __free_pages() from doing its job
65 * the put_page() at the end of this block will take care of
66 * release this page, thus avoiding a nasty leakage.
67 */
68 if (!folio)
69 goto out;
70
71 if (unlikely(folio_test_slab(folio)))
72 goto out_putfolio;
73 /* Pairs with smp_wmb() in slab freeing, e.g. SLUB's __free_slab() */
74 smp_rmb();
75 /*
76 * Check movable flag before taking the page lock because
77 * we use non-atomic bitops on newly allocated page flags so
78 * unconditionally grabbing the lock ruins page's owner side.
79 */
80 if (unlikely(!__folio_test_movable(folio)))
81 goto out_putfolio;
82 /* Pairs with smp_wmb() in slab allocation, e.g. SLUB's alloc_slab_page() */
83 smp_rmb();
84 if (unlikely(folio_test_slab(folio)))
85 goto out_putfolio;
86
87 /*
88 * As movable pages are not isolated from LRU lists, concurrent
89 * compaction threads can race against page migration functions
90 * as well as race against the releasing a page.
91 *
92 * In order to avoid having an already isolated movable page
93 * being (wrongly) re-isolated while it is under migration,
94 * or to avoid attempting to isolate pages being released,
95 * lets be sure we have the page lock
96 * before proceeding with the movable page isolation steps.
97 */
98 if (unlikely(!folio_trylock(folio)))
99 goto out_putfolio;
100
101 if (!folio_test_movable(folio) || folio_test_isolated(folio))
102 goto out_no_isolated;
103
104 mops = folio_movable_ops(folio);
105 VM_BUG_ON_FOLIO(!mops, folio);
106
107 if (!mops->isolate_page(&folio->page, mode))
108 goto out_no_isolated;
109
110 /* Driver shouldn't use the isolated flag */
111 WARN_ON_ONCE(folio_test_isolated(folio));
112 folio_set_isolated(folio);
113 folio_unlock(folio);
114
115 return true;
116
117out_no_isolated:
118 folio_unlock(folio);
119out_putfolio:
120 folio_put(folio);
121out:
122 return false;
123}
124
125static void putback_movable_folio(struct folio *folio)
126{
127 const struct movable_operations *mops = folio_movable_ops(folio);
128
129 mops->putback_page(&folio->page);
130 folio_clear_isolated(folio);
131}
132
133/*
134 * Put previously isolated pages back onto the appropriate lists
135 * from where they were once taken off for compaction/migration.
136 *
137 * This function shall be used whenever the isolated pageset has been
138 * built from lru, balloon, hugetlbfs page. See isolate_migratepages_range()
139 * and isolate_hugetlb().
140 */
141void putback_movable_pages(struct list_head *l)
142{
143 struct folio *folio;
144 struct folio *folio2;
145
146 list_for_each_entry_safe(folio, folio2, l, lru) {
147 if (unlikely(folio_test_hugetlb(folio))) {
148 folio_putback_active_hugetlb(folio);
149 continue;
150 }
151 list_del(&folio->lru);
152 /*
153 * We isolated non-lru movable folio so here we can use
154 * __folio_test_movable because LRU folio's mapping cannot
155 * have PAGE_MAPPING_MOVABLE.
156 */
157 if (unlikely(__folio_test_movable(folio))) {
158 VM_BUG_ON_FOLIO(!folio_test_isolated(folio), folio);
159 folio_lock(folio);
160 if (folio_test_movable(folio))
161 putback_movable_folio(folio);
162 else
163 folio_clear_isolated(folio);
164 folio_unlock(folio);
165 folio_put(folio);
166 } else {
167 node_stat_mod_folio(folio, NR_ISOLATED_ANON +
168 folio_is_file_lru(folio), -folio_nr_pages(folio));
169 folio_putback_lru(folio);
170 }
171 }
172}
173
174/* Must be called with an elevated refcount on the non-hugetlb folio */
175bool isolate_folio_to_list(struct folio *folio, struct list_head *list)
176{
177 bool isolated, lru;
178
179 if (folio_test_hugetlb(folio))
180 return isolate_hugetlb(folio, list);
181
182 lru = !__folio_test_movable(folio);
183 if (lru)
184 isolated = folio_isolate_lru(folio);
185 else
186 isolated = isolate_movable_page(&folio->page,
187 ISOLATE_UNEVICTABLE);
188
189 if (!isolated)
190 return false;
191
192 list_add(&folio->lru, list);
193 if (lru)
194 node_stat_add_folio(folio, NR_ISOLATED_ANON +
195 folio_is_file_lru(folio));
196
197 return true;
198}
199
200static bool try_to_map_unused_to_zeropage(struct page_vma_mapped_walk *pvmw,
201 struct folio *folio,
202 unsigned long idx)
203{
204 struct page *page = folio_page(folio, idx);
205 bool contains_data;
206 pte_t newpte;
207 void *addr;
208
209 if (PageCompound(page))
210 return false;
211 VM_BUG_ON_PAGE(!PageAnon(page), page);
212 VM_BUG_ON_PAGE(!PageLocked(page), page);
213 VM_BUG_ON_PAGE(pte_present(*pvmw->pte), page);
214
215 if (folio_test_mlocked(folio) || (pvmw->vma->vm_flags & VM_LOCKED) ||
216 mm_forbids_zeropage(pvmw->vma->vm_mm))
217 return false;
218
219 /*
220 * The pmd entry mapping the old thp was flushed and the pte mapping
221 * this subpage has been non present. If the subpage is only zero-filled
222 * then map it to the shared zeropage.
223 */
224 addr = kmap_local_page(page);
225 contains_data = memchr_inv(addr, 0, PAGE_SIZE);
226 kunmap_local(addr);
227
228 if (contains_data)
229 return false;
230
231 newpte = pte_mkspecial(pfn_pte(my_zero_pfn(pvmw->address),
232 pvmw->vma->vm_page_prot));
233 set_pte_at(pvmw->vma->vm_mm, pvmw->address, pvmw->pte, newpte);
234
235 dec_mm_counter(pvmw->vma->vm_mm, mm_counter(folio));
236 return true;
237}
238
239struct rmap_walk_arg {
240 struct folio *folio;
241 bool map_unused_to_zeropage;
242};
243
244/*
245 * Restore a potential migration pte to a working pte entry
246 */
247static bool remove_migration_pte(struct folio *folio,
248 struct vm_area_struct *vma, unsigned long addr, void *arg)
249{
250 struct rmap_walk_arg *rmap_walk_arg = arg;
251 DEFINE_FOLIO_VMA_WALK(pvmw, rmap_walk_arg->folio, vma, addr, PVMW_SYNC | PVMW_MIGRATION);
252
253 while (page_vma_mapped_walk(&pvmw)) {
254 rmap_t rmap_flags = RMAP_NONE;
255 pte_t old_pte;
256 pte_t pte;
257 swp_entry_t entry;
258 struct page *new;
259 unsigned long idx = 0;
260
261 /* pgoff is invalid for ksm pages, but they are never large */
262 if (folio_test_large(folio) && !folio_test_hugetlb(folio))
263 idx = linear_page_index(vma, pvmw.address) - pvmw.pgoff;
264 new = folio_page(folio, idx);
265
266#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
267 /* PMD-mapped THP migration entry */
268 if (!pvmw.pte) {
269 VM_BUG_ON_FOLIO(folio_test_hugetlb(folio) ||
270 !folio_test_pmd_mappable(folio), folio);
271 remove_migration_pmd(&pvmw, new);
272 continue;
273 }
274#endif
275 if (rmap_walk_arg->map_unused_to_zeropage &&
276 try_to_map_unused_to_zeropage(&pvmw, folio, idx))
277 continue;
278
279 folio_get(folio);
280 pte = mk_pte(new, READ_ONCE(vma->vm_page_prot));
281 old_pte = ptep_get(pvmw.pte);
282
283 entry = pte_to_swp_entry(old_pte);
284 if (!is_migration_entry_young(entry))
285 pte = pte_mkold(pte);
286 if (folio_test_dirty(folio) && is_migration_entry_dirty(entry))
287 pte = pte_mkdirty(pte);
288 if (pte_swp_soft_dirty(old_pte))
289 pte = pte_mksoft_dirty(pte);
290 else
291 pte = pte_clear_soft_dirty(pte);
292
293 if (is_writable_migration_entry(entry))
294 pte = pte_mkwrite(pte, vma);
295 else if (pte_swp_uffd_wp(old_pte))
296 pte = pte_mkuffd_wp(pte);
297
298 if (folio_test_anon(folio) && !is_readable_migration_entry(entry))
299 rmap_flags |= RMAP_EXCLUSIVE;
300
301 if (unlikely(is_device_private_page(new))) {
302 if (pte_write(pte))
303 entry = make_writable_device_private_entry(
304 page_to_pfn(new));
305 else
306 entry = make_readable_device_private_entry(
307 page_to_pfn(new));
308 pte = swp_entry_to_pte(entry);
309 if (pte_swp_soft_dirty(old_pte))
310 pte = pte_swp_mksoft_dirty(pte);
311 if (pte_swp_uffd_wp(old_pte))
312 pte = pte_swp_mkuffd_wp(pte);
313 }
314
315#ifdef CONFIG_HUGETLB_PAGE
316 if (folio_test_hugetlb(folio)) {
317 struct hstate *h = hstate_vma(vma);
318 unsigned int shift = huge_page_shift(h);
319 unsigned long psize = huge_page_size(h);
320
321 pte = arch_make_huge_pte(pte, shift, vma->vm_flags);
322 if (folio_test_anon(folio))
323 hugetlb_add_anon_rmap(folio, vma, pvmw.address,
324 rmap_flags);
325 else
326 hugetlb_add_file_rmap(folio);
327 set_huge_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte,
328 psize);
329 } else
330#endif
331 {
332 if (folio_test_anon(folio))
333 folio_add_anon_rmap_pte(folio, new, vma,
334 pvmw.address, rmap_flags);
335 else
336 folio_add_file_rmap_pte(folio, new, vma);
337 set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
338 }
339 if (vma->vm_flags & VM_LOCKED)
340 mlock_drain_local();
341
342 trace_remove_migration_pte(pvmw.address, pte_val(pte),
343 compound_order(new));
344
345 /* No need to invalidate - it was non-present before */
346 update_mmu_cache(vma, pvmw.address, pvmw.pte);
347 }
348
349 return true;
350}
351
352/*
353 * Get rid of all migration entries and replace them by
354 * references to the indicated page.
355 */
356void remove_migration_ptes(struct folio *src, struct folio *dst, int flags)
357{
358 struct rmap_walk_arg rmap_walk_arg = {
359 .folio = src,
360 .map_unused_to_zeropage = flags & RMP_USE_SHARED_ZEROPAGE,
361 };
362
363 struct rmap_walk_control rwc = {
364 .rmap_one = remove_migration_pte,
365 .arg = &rmap_walk_arg,
366 };
367
368 VM_BUG_ON_FOLIO((flags & RMP_USE_SHARED_ZEROPAGE) && (src != dst), src);
369
370 if (flags & RMP_LOCKED)
371 rmap_walk_locked(dst, &rwc);
372 else
373 rmap_walk(dst, &rwc);
374}
375
376/*
377 * Something used the pte of a page under migration. We need to
378 * get to the page and wait until migration is finished.
379 * When we return from this function the fault will be retried.
380 */
381void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
382 unsigned long address)
383{
384 spinlock_t *ptl;
385 pte_t *ptep;
386 pte_t pte;
387 swp_entry_t entry;
388
389 ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
390 if (!ptep)
391 return;
392
393 pte = ptep_get(ptep);
394 pte_unmap(ptep);
395
396 if (!is_swap_pte(pte))
397 goto out;
398
399 entry = pte_to_swp_entry(pte);
400 if (!is_migration_entry(entry))
401 goto out;
402
403 migration_entry_wait_on_locked(entry, ptl);
404 return;
405out:
406 spin_unlock(ptl);
407}
408
409#ifdef CONFIG_HUGETLB_PAGE
410/*
411 * The vma read lock must be held upon entry. Holding that lock prevents either
412 * the pte or the ptl from being freed.
413 *
414 * This function will release the vma lock before returning.
415 */
416void migration_entry_wait_huge(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep)
417{
418 spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), vma->vm_mm, ptep);
419 pte_t pte;
420
421 hugetlb_vma_assert_locked(vma);
422 spin_lock(ptl);
423 pte = huge_ptep_get(vma->vm_mm, addr, ptep);
424
425 if (unlikely(!is_hugetlb_entry_migration(pte))) {
426 spin_unlock(ptl);
427 hugetlb_vma_unlock_read(vma);
428 } else {
429 /*
430 * If migration entry existed, safe to release vma lock
431 * here because the pgtable page won't be freed without the
432 * pgtable lock released. See comment right above pgtable
433 * lock release in migration_entry_wait_on_locked().
434 */
435 hugetlb_vma_unlock_read(vma);
436 migration_entry_wait_on_locked(pte_to_swp_entry(pte), ptl);
437 }
438}
439#endif
440
441#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
442void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)
443{
444 spinlock_t *ptl;
445
446 ptl = pmd_lock(mm, pmd);
447 if (!is_pmd_migration_entry(*pmd))
448 goto unlock;
449 migration_entry_wait_on_locked(pmd_to_swp_entry(*pmd), ptl);
450 return;
451unlock:
452 spin_unlock(ptl);
453}
454#endif
455
456static int folio_expected_refs(struct address_space *mapping,
457 struct folio *folio)
458{
459 int refs = 1;
460 if (!mapping)
461 return refs;
462
463 refs += folio_nr_pages(folio);
464 if (folio_test_private(folio))
465 refs++;
466
467 return refs;
468}
469
470/*
471 * Replace the folio in the mapping.
472 *
473 * The number of remaining references must be:
474 * 1 for anonymous folios without a mapping
475 * 2 for folios with a mapping
476 * 3 for folios with a mapping and the private flag set.
477 */
478static int __folio_migrate_mapping(struct address_space *mapping,
479 struct folio *newfolio, struct folio *folio, int expected_count)
480{
481 XA_STATE(xas, &mapping->i_pages, folio_index(folio));
482 struct zone *oldzone, *newzone;
483 int dirty;
484 long nr = folio_nr_pages(folio);
485 long entries, i;
486
487 if (!mapping) {
488 /* Take off deferred split queue while frozen and memcg set */
489 if (folio_test_large(folio) &&
490 folio_test_large_rmappable(folio)) {
491 if (!folio_ref_freeze(folio, expected_count))
492 return -EAGAIN;
493 folio_unqueue_deferred_split(folio);
494 folio_ref_unfreeze(folio, expected_count);
495 }
496
497 /* No turning back from here */
498 newfolio->index = folio->index;
499 newfolio->mapping = folio->mapping;
500 if (folio_test_anon(folio) && folio_test_large(folio))
501 mod_mthp_stat(folio_order(folio), MTHP_STAT_NR_ANON, 1);
502 if (folio_test_swapbacked(folio))
503 __folio_set_swapbacked(newfolio);
504
505 return MIGRATEPAGE_SUCCESS;
506 }
507
508 oldzone = folio_zone(folio);
509 newzone = folio_zone(newfolio);
510
511 xas_lock_irq(&xas);
512 if (!folio_ref_freeze(folio, expected_count)) {
513 xas_unlock_irq(&xas);
514 return -EAGAIN;
515 }
516
517 /* Take off deferred split queue while frozen and memcg set */
518 folio_unqueue_deferred_split(folio);
519
520 /*
521 * Now we know that no one else is looking at the folio:
522 * no turning back from here.
523 */
524 newfolio->index = folio->index;
525 newfolio->mapping = folio->mapping;
526 if (folio_test_anon(folio) && folio_test_large(folio))
527 mod_mthp_stat(folio_order(folio), MTHP_STAT_NR_ANON, 1);
528 folio_ref_add(newfolio, nr); /* add cache reference */
529 if (folio_test_swapbacked(folio)) {
530 __folio_set_swapbacked(newfolio);
531 if (folio_test_swapcache(folio)) {
532 folio_set_swapcache(newfolio);
533 newfolio->private = folio_get_private(folio);
534 }
535 entries = nr;
536 } else {
537 VM_BUG_ON_FOLIO(folio_test_swapcache(folio), folio);
538 entries = 1;
539 }
540
541 /* Move dirty while folio refs frozen and newfolio not yet exposed */
542 dirty = folio_test_dirty(folio);
543 if (dirty) {
544 folio_clear_dirty(folio);
545 folio_set_dirty(newfolio);
546 }
547
548 /* Swap cache still stores N entries instead of a high-order entry */
549 for (i = 0; i < entries; i++) {
550 xas_store(&xas, newfolio);
551 xas_next(&xas);
552 }
553
554 /*
555 * Drop cache reference from old folio by unfreezing
556 * to one less reference.
557 * We know this isn't the last reference.
558 */
559 folio_ref_unfreeze(folio, expected_count - nr);
560
561 xas_unlock(&xas);
562 /* Leave irq disabled to prevent preemption while updating stats */
563
564 /*
565 * If moved to a different zone then also account
566 * the folio for that zone. Other VM counters will be
567 * taken care of when we establish references to the
568 * new folio and drop references to the old folio.
569 *
570 * Note that anonymous folios are accounted for
571 * via NR_FILE_PAGES and NR_ANON_MAPPED if they
572 * are mapped to swap space.
573 */
574 if (newzone != oldzone) {
575 struct lruvec *old_lruvec, *new_lruvec;
576 struct mem_cgroup *memcg;
577
578 memcg = folio_memcg(folio);
579 old_lruvec = mem_cgroup_lruvec(memcg, oldzone->zone_pgdat);
580 new_lruvec = mem_cgroup_lruvec(memcg, newzone->zone_pgdat);
581
582 __mod_lruvec_state(old_lruvec, NR_FILE_PAGES, -nr);
583 __mod_lruvec_state(new_lruvec, NR_FILE_PAGES, nr);
584 if (folio_test_swapbacked(folio) && !folio_test_swapcache(folio)) {
585 __mod_lruvec_state(old_lruvec, NR_SHMEM, -nr);
586 __mod_lruvec_state(new_lruvec, NR_SHMEM, nr);
587
588 if (folio_test_pmd_mappable(folio)) {
589 __mod_lruvec_state(old_lruvec, NR_SHMEM_THPS, -nr);
590 __mod_lruvec_state(new_lruvec, NR_SHMEM_THPS, nr);
591 }
592 }
593#ifdef CONFIG_SWAP
594 if (folio_test_swapcache(folio)) {
595 __mod_lruvec_state(old_lruvec, NR_SWAPCACHE, -nr);
596 __mod_lruvec_state(new_lruvec, NR_SWAPCACHE, nr);
597 }
598#endif
599 if (dirty && mapping_can_writeback(mapping)) {
600 __mod_lruvec_state(old_lruvec, NR_FILE_DIRTY, -nr);
601 __mod_zone_page_state(oldzone, NR_ZONE_WRITE_PENDING, -nr);
602 __mod_lruvec_state(new_lruvec, NR_FILE_DIRTY, nr);
603 __mod_zone_page_state(newzone, NR_ZONE_WRITE_PENDING, nr);
604 }
605 }
606 local_irq_enable();
607
608 return MIGRATEPAGE_SUCCESS;
609}
610
611int folio_migrate_mapping(struct address_space *mapping,
612 struct folio *newfolio, struct folio *folio, int extra_count)
613{
614 int expected_count = folio_expected_refs(mapping, folio) + extra_count;
615
616 if (folio_ref_count(folio) != expected_count)
617 return -EAGAIN;
618
619 return __folio_migrate_mapping(mapping, newfolio, folio, expected_count);
620}
621EXPORT_SYMBOL(folio_migrate_mapping);
622
623/*
624 * The expected number of remaining references is the same as that
625 * of folio_migrate_mapping().
626 */
627int migrate_huge_page_move_mapping(struct address_space *mapping,
628 struct folio *dst, struct folio *src)
629{
630 XA_STATE(xas, &mapping->i_pages, folio_index(src));
631 int rc, expected_count = folio_expected_refs(mapping, src);
632
633 if (folio_ref_count(src) != expected_count)
634 return -EAGAIN;
635
636 rc = folio_mc_copy(dst, src);
637 if (unlikely(rc))
638 return rc;
639
640 xas_lock_irq(&xas);
641 if (!folio_ref_freeze(src, expected_count)) {
642 xas_unlock_irq(&xas);
643 return -EAGAIN;
644 }
645
646 dst->index = src->index;
647 dst->mapping = src->mapping;
648
649 folio_ref_add(dst, folio_nr_pages(dst));
650
651 xas_store(&xas, dst);
652
653 folio_ref_unfreeze(src, expected_count - folio_nr_pages(src));
654
655 xas_unlock_irq(&xas);
656
657 return MIGRATEPAGE_SUCCESS;
658}
659
660/*
661 * Copy the flags and some other ancillary information
662 */
663void folio_migrate_flags(struct folio *newfolio, struct folio *folio)
664{
665 int cpupid;
666
667 if (folio_test_referenced(folio))
668 folio_set_referenced(newfolio);
669 if (folio_test_uptodate(folio))
670 folio_mark_uptodate(newfolio);
671 if (folio_test_clear_active(folio)) {
672 VM_BUG_ON_FOLIO(folio_test_unevictable(folio), folio);
673 folio_set_active(newfolio);
674 } else if (folio_test_clear_unevictable(folio))
675 folio_set_unevictable(newfolio);
676 if (folio_test_workingset(folio))
677 folio_set_workingset(newfolio);
678 if (folio_test_checked(folio))
679 folio_set_checked(newfolio);
680 /*
681 * PG_anon_exclusive (-> PG_mappedtodisk) is always migrated via
682 * migration entries. We can still have PG_anon_exclusive set on an
683 * effectively unmapped and unreferenced first sub-pages of an
684 * anonymous THP: we can simply copy it here via PG_mappedtodisk.
685 */
686 if (folio_test_mappedtodisk(folio))
687 folio_set_mappedtodisk(newfolio);
688
689 /* Move dirty on pages not done by folio_migrate_mapping() */
690 if (folio_test_dirty(folio))
691 folio_set_dirty(newfolio);
692
693 if (folio_test_young(folio))
694 folio_set_young(newfolio);
695 if (folio_test_idle(folio))
696 folio_set_idle(newfolio);
697
698 folio_migrate_refs(newfolio, folio);
699 /*
700 * Copy NUMA information to the new page, to prevent over-eager
701 * future migrations of this same page.
702 */
703 cpupid = folio_xchg_last_cpupid(folio, -1);
704 /*
705 * For memory tiering mode, when migrate between slow and fast
706 * memory node, reset cpupid, because that is used to record
707 * page access time in slow memory node.
708 */
709 if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) {
710 bool f_toptier = node_is_toptier(folio_nid(folio));
711 bool t_toptier = node_is_toptier(folio_nid(newfolio));
712
713 if (f_toptier != t_toptier)
714 cpupid = -1;
715 }
716 folio_xchg_last_cpupid(newfolio, cpupid);
717
718 folio_migrate_ksm(newfolio, folio);
719 /*
720 * Please do not reorder this without considering how mm/ksm.c's
721 * ksm_get_folio() depends upon ksm_migrate_page() and the
722 * swapcache flag.
723 */
724 if (folio_test_swapcache(folio))
725 folio_clear_swapcache(folio);
726 folio_clear_private(folio);
727
728 /* page->private contains hugetlb specific flags */
729 if (!folio_test_hugetlb(folio))
730 folio->private = NULL;
731
732 /*
733 * If any waiters have accumulated on the new page then
734 * wake them up.
735 */
736 if (folio_test_writeback(newfolio))
737 folio_end_writeback(newfolio);
738
739 /*
740 * PG_readahead shares the same bit with PG_reclaim. The above
741 * end_page_writeback() may clear PG_readahead mistakenly, so set the
742 * bit after that.
743 */
744 if (folio_test_readahead(folio))
745 folio_set_readahead(newfolio);
746
747 folio_copy_owner(newfolio, folio);
748 pgalloc_tag_swap(newfolio, folio);
749
750 mem_cgroup_migrate(folio, newfolio);
751}
752EXPORT_SYMBOL(folio_migrate_flags);
753
754/************************************************************
755 * Migration functions
756 ***********************************************************/
757
758static int __migrate_folio(struct address_space *mapping, struct folio *dst,
759 struct folio *src, void *src_private,
760 enum migrate_mode mode)
761{
762 int rc, expected_count = folio_expected_refs(mapping, src);
763
764 /* Check whether src does not have extra refs before we do more work */
765 if (folio_ref_count(src) != expected_count)
766 return -EAGAIN;
767
768 rc = folio_mc_copy(dst, src);
769 if (unlikely(rc))
770 return rc;
771
772 rc = __folio_migrate_mapping(mapping, dst, src, expected_count);
773 if (rc != MIGRATEPAGE_SUCCESS)
774 return rc;
775
776 if (src_private)
777 folio_attach_private(dst, folio_detach_private(src));
778
779 folio_migrate_flags(dst, src);
780 return MIGRATEPAGE_SUCCESS;
781}
782
783/**
784 * migrate_folio() - Simple folio migration.
785 * @mapping: The address_space containing the folio.
786 * @dst: The folio to migrate the data to.
787 * @src: The folio containing the current data.
788 * @mode: How to migrate the page.
789 *
790 * Common logic to directly migrate a single LRU folio suitable for
791 * folios that do not have private data.
792 *
793 * Folios are locked upon entry and exit.
794 */
795int migrate_folio(struct address_space *mapping, struct folio *dst,
796 struct folio *src, enum migrate_mode mode)
797{
798 BUG_ON(folio_test_writeback(src)); /* Writeback must be complete */
799 return __migrate_folio(mapping, dst, src, NULL, mode);
800}
801EXPORT_SYMBOL(migrate_folio);
802
803#ifdef CONFIG_BUFFER_HEAD
804/* Returns true if all buffers are successfully locked */
805static bool buffer_migrate_lock_buffers(struct buffer_head *head,
806 enum migrate_mode mode)
807{
808 struct buffer_head *bh = head;
809 struct buffer_head *failed_bh;
810
811 do {
812 if (!trylock_buffer(bh)) {
813 if (mode == MIGRATE_ASYNC)
814 goto unlock;
815 if (mode == MIGRATE_SYNC_LIGHT && !buffer_uptodate(bh))
816 goto unlock;
817 lock_buffer(bh);
818 }
819
820 bh = bh->b_this_page;
821 } while (bh != head);
822
823 return true;
824
825unlock:
826 /* We failed to lock the buffer and cannot stall. */
827 failed_bh = bh;
828 bh = head;
829 while (bh != failed_bh) {
830 unlock_buffer(bh);
831 bh = bh->b_this_page;
832 }
833
834 return false;
835}
836
837static int __buffer_migrate_folio(struct address_space *mapping,
838 struct folio *dst, struct folio *src, enum migrate_mode mode,
839 bool check_refs)
840{
841 struct buffer_head *bh, *head;
842 int rc;
843 int expected_count;
844
845 head = folio_buffers(src);
846 if (!head)
847 return migrate_folio(mapping, dst, src, mode);
848
849 /* Check whether page does not have extra refs before we do more work */
850 expected_count = folio_expected_refs(mapping, src);
851 if (folio_ref_count(src) != expected_count)
852 return -EAGAIN;
853
854 if (!buffer_migrate_lock_buffers(head, mode))
855 return -EAGAIN;
856
857 if (check_refs) {
858 bool busy;
859 bool invalidated = false;
860
861recheck_buffers:
862 busy = false;
863 spin_lock(&mapping->i_private_lock);
864 bh = head;
865 do {
866 if (atomic_read(&bh->b_count)) {
867 busy = true;
868 break;
869 }
870 bh = bh->b_this_page;
871 } while (bh != head);
872 if (busy) {
873 if (invalidated) {
874 rc = -EAGAIN;
875 goto unlock_buffers;
876 }
877 spin_unlock(&mapping->i_private_lock);
878 invalidate_bh_lrus();
879 invalidated = true;
880 goto recheck_buffers;
881 }
882 }
883
884 rc = filemap_migrate_folio(mapping, dst, src, mode);
885 if (rc != MIGRATEPAGE_SUCCESS)
886 goto unlock_buffers;
887
888 bh = head;
889 do {
890 folio_set_bh(bh, dst, bh_offset(bh));
891 bh = bh->b_this_page;
892 } while (bh != head);
893
894unlock_buffers:
895 if (check_refs)
896 spin_unlock(&mapping->i_private_lock);
897 bh = head;
898 do {
899 unlock_buffer(bh);
900 bh = bh->b_this_page;
901 } while (bh != head);
902
903 return rc;
904}
905
906/**
907 * buffer_migrate_folio() - Migration function for folios with buffers.
908 * @mapping: The address space containing @src.
909 * @dst: The folio to migrate to.
910 * @src: The folio to migrate from.
911 * @mode: How to migrate the folio.
912 *
913 * This function can only be used if the underlying filesystem guarantees
914 * that no other references to @src exist. For example attached buffer
915 * heads are accessed only under the folio lock. If your filesystem cannot
916 * provide this guarantee, buffer_migrate_folio_norefs() may be more
917 * appropriate.
918 *
919 * Return: 0 on success or a negative errno on failure.
920 */
921int buffer_migrate_folio(struct address_space *mapping,
922 struct folio *dst, struct folio *src, enum migrate_mode mode)
923{
924 return __buffer_migrate_folio(mapping, dst, src, mode, false);
925}
926EXPORT_SYMBOL(buffer_migrate_folio);
927
928/**
929 * buffer_migrate_folio_norefs() - Migration function for folios with buffers.
930 * @mapping: The address space containing @src.
931 * @dst: The folio to migrate to.
932 * @src: The folio to migrate from.
933 * @mode: How to migrate the folio.
934 *
935 * Like buffer_migrate_folio() except that this variant is more careful
936 * and checks that there are also no buffer head references. This function
937 * is the right one for mappings where buffer heads are directly looked
938 * up and referenced (such as block device mappings).
939 *
940 * Return: 0 on success or a negative errno on failure.
941 */
942int buffer_migrate_folio_norefs(struct address_space *mapping,
943 struct folio *dst, struct folio *src, enum migrate_mode mode)
944{
945 return __buffer_migrate_folio(mapping, dst, src, mode, true);
946}
947EXPORT_SYMBOL_GPL(buffer_migrate_folio_norefs);
948#endif /* CONFIG_BUFFER_HEAD */
949
950int filemap_migrate_folio(struct address_space *mapping,
951 struct folio *dst, struct folio *src, enum migrate_mode mode)
952{
953 return __migrate_folio(mapping, dst, src, folio_get_private(src), mode);
954}
955EXPORT_SYMBOL_GPL(filemap_migrate_folio);
956
957/*
958 * Writeback a folio to clean the dirty state
959 */
960static int writeout(struct address_space *mapping, struct folio *folio)
961{
962 struct writeback_control wbc = {
963 .sync_mode = WB_SYNC_NONE,
964 .nr_to_write = 1,
965 .range_start = 0,
966 .range_end = LLONG_MAX,
967 .for_reclaim = 1
968 };
969 int rc;
970
971 if (!mapping->a_ops->writepage)
972 /* No write method for the address space */
973 return -EINVAL;
974
975 if (!folio_clear_dirty_for_io(folio))
976 /* Someone else already triggered a write */
977 return -EAGAIN;
978
979 /*
980 * A dirty folio may imply that the underlying filesystem has
981 * the folio on some queue. So the folio must be clean for
982 * migration. Writeout may mean we lose the lock and the
983 * folio state is no longer what we checked for earlier.
984 * At this point we know that the migration attempt cannot
985 * be successful.
986 */
987 remove_migration_ptes(folio, folio, 0);
988
989 rc = mapping->a_ops->writepage(&folio->page, &wbc);
990
991 if (rc != AOP_WRITEPAGE_ACTIVATE)
992 /* unlocked. Relock */
993 folio_lock(folio);
994
995 return (rc < 0) ? -EIO : -EAGAIN;
996}
997
998/*
999 * Default handling if a filesystem does not provide a migration function.
1000 */
1001static int fallback_migrate_folio(struct address_space *mapping,
1002 struct folio *dst, struct folio *src, enum migrate_mode mode)
1003{
1004 if (folio_test_dirty(src)) {
1005 /* Only writeback folios in full synchronous migration */
1006 switch (mode) {
1007 case MIGRATE_SYNC:
1008 break;
1009 default:
1010 return -EBUSY;
1011 }
1012 return writeout(mapping, src);
1013 }
1014
1015 /*
1016 * Buffers may be managed in a filesystem specific way.
1017 * We must have no buffers or drop them.
1018 */
1019 if (!filemap_release_folio(src, GFP_KERNEL))
1020 return mode == MIGRATE_SYNC ? -EAGAIN : -EBUSY;
1021
1022 return migrate_folio(mapping, dst, src, mode);
1023}
1024
1025/*
1026 * Move a page to a newly allocated page
1027 * The page is locked and all ptes have been successfully removed.
1028 *
1029 * The new page will have replaced the old page if this function
1030 * is successful.
1031 *
1032 * Return value:
1033 * < 0 - error code
1034 * MIGRATEPAGE_SUCCESS - success
1035 */
1036static int move_to_new_folio(struct folio *dst, struct folio *src,
1037 enum migrate_mode mode)
1038{
1039 int rc = -EAGAIN;
1040 bool is_lru = !__folio_test_movable(src);
1041
1042 VM_BUG_ON_FOLIO(!folio_test_locked(src), src);
1043 VM_BUG_ON_FOLIO(!folio_test_locked(dst), dst);
1044
1045 if (likely(is_lru)) {
1046 struct address_space *mapping = folio_mapping(src);
1047
1048 if (!mapping)
1049 rc = migrate_folio(mapping, dst, src, mode);
1050 else if (mapping_inaccessible(mapping))
1051 rc = -EOPNOTSUPP;
1052 else if (mapping->a_ops->migrate_folio)
1053 /*
1054 * Most folios have a mapping and most filesystems
1055 * provide a migrate_folio callback. Anonymous folios
1056 * are part of swap space which also has its own
1057 * migrate_folio callback. This is the most common path
1058 * for page migration.
1059 */
1060 rc = mapping->a_ops->migrate_folio(mapping, dst, src,
1061 mode);
1062 else
1063 rc = fallback_migrate_folio(mapping, dst, src, mode);
1064 } else {
1065 const struct movable_operations *mops;
1066
1067 /*
1068 * In case of non-lru page, it could be released after
1069 * isolation step. In that case, we shouldn't try migration.
1070 */
1071 VM_BUG_ON_FOLIO(!folio_test_isolated(src), src);
1072 if (!folio_test_movable(src)) {
1073 rc = MIGRATEPAGE_SUCCESS;
1074 folio_clear_isolated(src);
1075 goto out;
1076 }
1077
1078 mops = folio_movable_ops(src);
1079 rc = mops->migrate_page(&dst->page, &src->page, mode);
1080 WARN_ON_ONCE(rc == MIGRATEPAGE_SUCCESS &&
1081 !folio_test_isolated(src));
1082 }
1083
1084 /*
1085 * When successful, old pagecache src->mapping must be cleared before
1086 * src is freed; but stats require that PageAnon be left as PageAnon.
1087 */
1088 if (rc == MIGRATEPAGE_SUCCESS) {
1089 if (__folio_test_movable(src)) {
1090 VM_BUG_ON_FOLIO(!folio_test_isolated(src), src);
1091
1092 /*
1093 * We clear PG_movable under page_lock so any compactor
1094 * cannot try to migrate this page.
1095 */
1096 folio_clear_isolated(src);
1097 }
1098
1099 /*
1100 * Anonymous and movable src->mapping will be cleared by
1101 * free_pages_prepare so don't reset it here for keeping
1102 * the type to work PageAnon, for example.
1103 */
1104 if (!folio_mapping_flags(src))
1105 src->mapping = NULL;
1106
1107 if (likely(!folio_is_zone_device(dst)))
1108 flush_dcache_folio(dst);
1109 }
1110out:
1111 return rc;
1112}
1113
1114/*
1115 * To record some information during migration, we use unused private
1116 * field of struct folio of the newly allocated destination folio.
1117 * This is safe because nobody is using it except us.
1118 */
1119enum {
1120 PAGE_WAS_MAPPED = BIT(0),
1121 PAGE_WAS_MLOCKED = BIT(1),
1122 PAGE_OLD_STATES = PAGE_WAS_MAPPED | PAGE_WAS_MLOCKED,
1123};
1124
1125static void __migrate_folio_record(struct folio *dst,
1126 int old_page_state,
1127 struct anon_vma *anon_vma)
1128{
1129 dst->private = (void *)anon_vma + old_page_state;
1130}
1131
1132static void __migrate_folio_extract(struct folio *dst,
1133 int *old_page_state,
1134 struct anon_vma **anon_vmap)
1135{
1136 unsigned long private = (unsigned long)dst->private;
1137
1138 *anon_vmap = (struct anon_vma *)(private & ~PAGE_OLD_STATES);
1139 *old_page_state = private & PAGE_OLD_STATES;
1140 dst->private = NULL;
1141}
1142
1143/* Restore the source folio to the original state upon failure */
1144static void migrate_folio_undo_src(struct folio *src,
1145 int page_was_mapped,
1146 struct anon_vma *anon_vma,
1147 bool locked,
1148 struct list_head *ret)
1149{
1150 if (page_was_mapped)
1151 remove_migration_ptes(src, src, 0);
1152 /* Drop an anon_vma reference if we took one */
1153 if (anon_vma)
1154 put_anon_vma(anon_vma);
1155 if (locked)
1156 folio_unlock(src);
1157 if (ret)
1158 list_move_tail(&src->lru, ret);
1159}
1160
1161/* Restore the destination folio to the original state upon failure */
1162static void migrate_folio_undo_dst(struct folio *dst, bool locked,
1163 free_folio_t put_new_folio, unsigned long private)
1164{
1165 if (locked)
1166 folio_unlock(dst);
1167 if (put_new_folio)
1168 put_new_folio(dst, private);
1169 else
1170 folio_put(dst);
1171}
1172
1173/* Cleanup src folio upon migration success */
1174static void migrate_folio_done(struct folio *src,
1175 enum migrate_reason reason)
1176{
1177 /*
1178 * Compaction can migrate also non-LRU pages which are
1179 * not accounted to NR_ISOLATED_*. They can be recognized
1180 * as __folio_test_movable
1181 */
1182 if (likely(!__folio_test_movable(src)) && reason != MR_DEMOTION)
1183 mod_node_page_state(folio_pgdat(src), NR_ISOLATED_ANON +
1184 folio_is_file_lru(src), -folio_nr_pages(src));
1185
1186 if (reason != MR_MEMORY_FAILURE)
1187 /* We release the page in page_handle_poison. */
1188 folio_put(src);
1189}
1190
1191/* Obtain the lock on page, remove all ptes. */
1192static int migrate_folio_unmap(new_folio_t get_new_folio,
1193 free_folio_t put_new_folio, unsigned long private,
1194 struct folio *src, struct folio **dstp, enum migrate_mode mode,
1195 enum migrate_reason reason, struct list_head *ret)
1196{
1197 struct folio *dst;
1198 int rc = -EAGAIN;
1199 int old_page_state = 0;
1200 struct anon_vma *anon_vma = NULL;
1201 bool is_lru = data_race(!__folio_test_movable(src));
1202 bool locked = false;
1203 bool dst_locked = false;
1204
1205 if (folio_ref_count(src) == 1) {
1206 /* Folio was freed from under us. So we are done. */
1207 folio_clear_active(src);
1208 folio_clear_unevictable(src);
1209 /* free_pages_prepare() will clear PG_isolated. */
1210 list_del(&src->lru);
1211 migrate_folio_done(src, reason);
1212 return MIGRATEPAGE_SUCCESS;
1213 }
1214
1215 dst = get_new_folio(src, private);
1216 if (!dst)
1217 return -ENOMEM;
1218 *dstp = dst;
1219
1220 dst->private = NULL;
1221
1222 if (!folio_trylock(src)) {
1223 if (mode == MIGRATE_ASYNC)
1224 goto out;
1225
1226 /*
1227 * It's not safe for direct compaction to call lock_page.
1228 * For example, during page readahead pages are added locked
1229 * to the LRU. Later, when the IO completes the pages are
1230 * marked uptodate and unlocked. However, the queueing
1231 * could be merging multiple pages for one bio (e.g.
1232 * mpage_readahead). If an allocation happens for the
1233 * second or third page, the process can end up locking
1234 * the same page twice and deadlocking. Rather than
1235 * trying to be clever about what pages can be locked,
1236 * avoid the use of lock_page for direct compaction
1237 * altogether.
1238 */
1239 if (current->flags & PF_MEMALLOC)
1240 goto out;
1241
1242 /*
1243 * In "light" mode, we can wait for transient locks (eg
1244 * inserting a page into the page table), but it's not
1245 * worth waiting for I/O.
1246 */
1247 if (mode == MIGRATE_SYNC_LIGHT && !folio_test_uptodate(src))
1248 goto out;
1249
1250 folio_lock(src);
1251 }
1252 locked = true;
1253 if (folio_test_mlocked(src))
1254 old_page_state |= PAGE_WAS_MLOCKED;
1255
1256 if (folio_test_writeback(src)) {
1257 /*
1258 * Only in the case of a full synchronous migration is it
1259 * necessary to wait for PageWriteback. In the async case,
1260 * the retry loop is too short and in the sync-light case,
1261 * the overhead of stalling is too much
1262 */
1263 switch (mode) {
1264 case MIGRATE_SYNC:
1265 break;
1266 default:
1267 rc = -EBUSY;
1268 goto out;
1269 }
1270 folio_wait_writeback(src);
1271 }
1272
1273 /*
1274 * By try_to_migrate(), src->mapcount goes down to 0 here. In this case,
1275 * we cannot notice that anon_vma is freed while we migrate a page.
1276 * This get_anon_vma() delays freeing anon_vma pointer until the end
1277 * of migration. File cache pages are no problem because of page_lock()
1278 * File Caches may use write_page() or lock_page() in migration, then,
1279 * just care Anon page here.
1280 *
1281 * Only folio_get_anon_vma() understands the subtleties of
1282 * getting a hold on an anon_vma from outside one of its mms.
1283 * But if we cannot get anon_vma, then we won't need it anyway,
1284 * because that implies that the anon page is no longer mapped
1285 * (and cannot be remapped so long as we hold the page lock).
1286 */
1287 if (folio_test_anon(src) && !folio_test_ksm(src))
1288 anon_vma = folio_get_anon_vma(src);
1289
1290 /*
1291 * Block others from accessing the new page when we get around to
1292 * establishing additional references. We are usually the only one
1293 * holding a reference to dst at this point. We used to have a BUG
1294 * here if folio_trylock(dst) fails, but would like to allow for
1295 * cases where there might be a race with the previous use of dst.
1296 * This is much like races on refcount of oldpage: just don't BUG().
1297 */
1298 if (unlikely(!folio_trylock(dst)))
1299 goto out;
1300 dst_locked = true;
1301
1302 if (unlikely(!is_lru)) {
1303 __migrate_folio_record(dst, old_page_state, anon_vma);
1304 return MIGRATEPAGE_UNMAP;
1305 }
1306
1307 /*
1308 * Corner case handling:
1309 * 1. When a new swap-cache page is read into, it is added to the LRU
1310 * and treated as swapcache but it has no rmap yet.
1311 * Calling try_to_unmap() against a src->mapping==NULL page will
1312 * trigger a BUG. So handle it here.
1313 * 2. An orphaned page (see truncate_cleanup_page) might have
1314 * fs-private metadata. The page can be picked up due to memory
1315 * offlining. Everywhere else except page reclaim, the page is
1316 * invisible to the vm, so the page can not be migrated. So try to
1317 * free the metadata, so the page can be freed.
1318 */
1319 if (!src->mapping) {
1320 if (folio_test_private(src)) {
1321 try_to_free_buffers(src);
1322 goto out;
1323 }
1324 } else if (folio_mapped(src)) {
1325 /* Establish migration ptes */
1326 VM_BUG_ON_FOLIO(folio_test_anon(src) &&
1327 !folio_test_ksm(src) && !anon_vma, src);
1328 try_to_migrate(src, mode == MIGRATE_ASYNC ? TTU_BATCH_FLUSH : 0);
1329 old_page_state |= PAGE_WAS_MAPPED;
1330 }
1331
1332 if (!folio_mapped(src)) {
1333 __migrate_folio_record(dst, old_page_state, anon_vma);
1334 return MIGRATEPAGE_UNMAP;
1335 }
1336
1337out:
1338 /*
1339 * A folio that has not been unmapped will be restored to
1340 * right list unless we want to retry.
1341 */
1342 if (rc == -EAGAIN)
1343 ret = NULL;
1344
1345 migrate_folio_undo_src(src, old_page_state & PAGE_WAS_MAPPED,
1346 anon_vma, locked, ret);
1347 migrate_folio_undo_dst(dst, dst_locked, put_new_folio, private);
1348
1349 return rc;
1350}
1351
1352/* Migrate the folio to the newly allocated folio in dst. */
1353static int migrate_folio_move(free_folio_t put_new_folio, unsigned long private,
1354 struct folio *src, struct folio *dst,
1355 enum migrate_mode mode, enum migrate_reason reason,
1356 struct list_head *ret)
1357{
1358 int rc;
1359 int old_page_state = 0;
1360 struct anon_vma *anon_vma = NULL;
1361 bool is_lru = !__folio_test_movable(src);
1362 struct list_head *prev;
1363
1364 __migrate_folio_extract(dst, &old_page_state, &anon_vma);
1365 prev = dst->lru.prev;
1366 list_del(&dst->lru);
1367
1368 rc = move_to_new_folio(dst, src, mode);
1369 if (rc)
1370 goto out;
1371
1372 if (unlikely(!is_lru))
1373 goto out_unlock_both;
1374
1375 /*
1376 * When successful, push dst to LRU immediately: so that if it
1377 * turns out to be an mlocked page, remove_migration_ptes() will
1378 * automatically build up the correct dst->mlock_count for it.
1379 *
1380 * We would like to do something similar for the old page, when
1381 * unsuccessful, and other cases when a page has been temporarily
1382 * isolated from the unevictable LRU: but this case is the easiest.
1383 */
1384 folio_add_lru(dst);
1385 if (old_page_state & PAGE_WAS_MLOCKED)
1386 lru_add_drain();
1387
1388 if (old_page_state & PAGE_WAS_MAPPED)
1389 remove_migration_ptes(src, dst, 0);
1390
1391out_unlock_both:
1392 folio_unlock(dst);
1393 set_page_owner_migrate_reason(&dst->page, reason);
1394 /*
1395 * If migration is successful, decrease refcount of dst,
1396 * which will not free the page because new page owner increased
1397 * refcounter.
1398 */
1399 folio_put(dst);
1400
1401 /*
1402 * A folio that has been migrated has all references removed
1403 * and will be freed.
1404 */
1405 list_del(&src->lru);
1406 /* Drop an anon_vma reference if we took one */
1407 if (anon_vma)
1408 put_anon_vma(anon_vma);
1409 folio_unlock(src);
1410 migrate_folio_done(src, reason);
1411
1412 return rc;
1413out:
1414 /*
1415 * A folio that has not been migrated will be restored to
1416 * right list unless we want to retry.
1417 */
1418 if (rc == -EAGAIN) {
1419 list_add(&dst->lru, prev);
1420 __migrate_folio_record(dst, old_page_state, anon_vma);
1421 return rc;
1422 }
1423
1424 migrate_folio_undo_src(src, old_page_state & PAGE_WAS_MAPPED,
1425 anon_vma, true, ret);
1426 migrate_folio_undo_dst(dst, true, put_new_folio, private);
1427
1428 return rc;
1429}
1430
1431/*
1432 * Counterpart of unmap_and_move_page() for hugepage migration.
1433 *
1434 * This function doesn't wait the completion of hugepage I/O
1435 * because there is no race between I/O and migration for hugepage.
1436 * Note that currently hugepage I/O occurs only in direct I/O
1437 * where no lock is held and PG_writeback is irrelevant,
1438 * and writeback status of all subpages are counted in the reference
1439 * count of the head page (i.e. if all subpages of a 2MB hugepage are
1440 * under direct I/O, the reference of the head page is 512 and a bit more.)
1441 * This means that when we try to migrate hugepage whose subpages are
1442 * doing direct I/O, some references remain after try_to_unmap() and
1443 * hugepage migration fails without data corruption.
1444 *
1445 * There is also no race when direct I/O is issued on the page under migration,
1446 * because then pte is replaced with migration swap entry and direct I/O code
1447 * will wait in the page fault for migration to complete.
1448 */
1449static int unmap_and_move_huge_page(new_folio_t get_new_folio,
1450 free_folio_t put_new_folio, unsigned long private,
1451 struct folio *src, int force, enum migrate_mode mode,
1452 int reason, struct list_head *ret)
1453{
1454 struct folio *dst;
1455 int rc = -EAGAIN;
1456 int page_was_mapped = 0;
1457 struct anon_vma *anon_vma = NULL;
1458 struct address_space *mapping = NULL;
1459
1460 if (folio_ref_count(src) == 1) {
1461 /* page was freed from under us. So we are done. */
1462 folio_putback_active_hugetlb(src);
1463 return MIGRATEPAGE_SUCCESS;
1464 }
1465
1466 dst = get_new_folio(src, private);
1467 if (!dst)
1468 return -ENOMEM;
1469
1470 if (!folio_trylock(src)) {
1471 if (!force)
1472 goto out;
1473 switch (mode) {
1474 case MIGRATE_SYNC:
1475 break;
1476 default:
1477 goto out;
1478 }
1479 folio_lock(src);
1480 }
1481
1482 /*
1483 * Check for pages which are in the process of being freed. Without
1484 * folio_mapping() set, hugetlbfs specific move page routine will not
1485 * be called and we could leak usage counts for subpools.
1486 */
1487 if (hugetlb_folio_subpool(src) && !folio_mapping(src)) {
1488 rc = -EBUSY;
1489 goto out_unlock;
1490 }
1491
1492 if (folio_test_anon(src))
1493 anon_vma = folio_get_anon_vma(src);
1494
1495 if (unlikely(!folio_trylock(dst)))
1496 goto put_anon;
1497
1498 if (folio_mapped(src)) {
1499 enum ttu_flags ttu = 0;
1500
1501 if (!folio_test_anon(src)) {
1502 /*
1503 * In shared mappings, try_to_unmap could potentially
1504 * call huge_pmd_unshare. Because of this, take
1505 * semaphore in write mode here and set TTU_RMAP_LOCKED
1506 * to let lower levels know we have taken the lock.
1507 */
1508 mapping = hugetlb_folio_mapping_lock_write(src);
1509 if (unlikely(!mapping))
1510 goto unlock_put_anon;
1511
1512 ttu = TTU_RMAP_LOCKED;
1513 }
1514
1515 try_to_migrate(src, ttu);
1516 page_was_mapped = 1;
1517
1518 if (ttu & TTU_RMAP_LOCKED)
1519 i_mmap_unlock_write(mapping);
1520 }
1521
1522 if (!folio_mapped(src))
1523 rc = move_to_new_folio(dst, src, mode);
1524
1525 if (page_was_mapped)
1526 remove_migration_ptes(src,
1527 rc == MIGRATEPAGE_SUCCESS ? dst : src, 0);
1528
1529unlock_put_anon:
1530 folio_unlock(dst);
1531
1532put_anon:
1533 if (anon_vma)
1534 put_anon_vma(anon_vma);
1535
1536 if (rc == MIGRATEPAGE_SUCCESS) {
1537 move_hugetlb_state(src, dst, reason);
1538 put_new_folio = NULL;
1539 }
1540
1541out_unlock:
1542 folio_unlock(src);
1543out:
1544 if (rc == MIGRATEPAGE_SUCCESS)
1545 folio_putback_active_hugetlb(src);
1546 else if (rc != -EAGAIN)
1547 list_move_tail(&src->lru, ret);
1548
1549 /*
1550 * If migration was not successful and there's a freeing callback, use
1551 * it. Otherwise, put_page() will drop the reference grabbed during
1552 * isolation.
1553 */
1554 if (put_new_folio)
1555 put_new_folio(dst, private);
1556 else
1557 folio_putback_active_hugetlb(dst);
1558
1559 return rc;
1560}
1561
1562static inline int try_split_folio(struct folio *folio, struct list_head *split_folios,
1563 enum migrate_mode mode)
1564{
1565 int rc;
1566
1567 if (mode == MIGRATE_ASYNC) {
1568 if (!folio_trylock(folio))
1569 return -EAGAIN;
1570 } else {
1571 folio_lock(folio);
1572 }
1573 rc = split_folio_to_list(folio, split_folios);
1574 folio_unlock(folio);
1575 if (!rc)
1576 list_move_tail(&folio->lru, split_folios);
1577
1578 return rc;
1579}
1580
1581#ifdef CONFIG_TRANSPARENT_HUGEPAGE
1582#define NR_MAX_BATCHED_MIGRATION HPAGE_PMD_NR
1583#else
1584#define NR_MAX_BATCHED_MIGRATION 512
1585#endif
1586#define NR_MAX_MIGRATE_PAGES_RETRY 10
1587#define NR_MAX_MIGRATE_ASYNC_RETRY 3
1588#define NR_MAX_MIGRATE_SYNC_RETRY \
1589 (NR_MAX_MIGRATE_PAGES_RETRY - NR_MAX_MIGRATE_ASYNC_RETRY)
1590
1591struct migrate_pages_stats {
1592 int nr_succeeded; /* Normal and large folios migrated successfully, in
1593 units of base pages */
1594 int nr_failed_pages; /* Normal and large folios failed to be migrated, in
1595 units of base pages. Untried folios aren't counted */
1596 int nr_thp_succeeded; /* THP migrated successfully */
1597 int nr_thp_failed; /* THP failed to be migrated */
1598 int nr_thp_split; /* THP split before migrating */
1599 int nr_split; /* Large folio (include THP) split before migrating */
1600};
1601
1602/*
1603 * Returns the number of hugetlb folios that were not migrated, or an error code
1604 * after NR_MAX_MIGRATE_PAGES_RETRY attempts or if no hugetlb folios are movable
1605 * any more because the list has become empty or no retryable hugetlb folios
1606 * exist any more. It is caller's responsibility to call putback_movable_pages()
1607 * only if ret != 0.
1608 */
1609static int migrate_hugetlbs(struct list_head *from, new_folio_t get_new_folio,
1610 free_folio_t put_new_folio, unsigned long private,
1611 enum migrate_mode mode, int reason,
1612 struct migrate_pages_stats *stats,
1613 struct list_head *ret_folios)
1614{
1615 int retry = 1;
1616 int nr_failed = 0;
1617 int nr_retry_pages = 0;
1618 int pass = 0;
1619 struct folio *folio, *folio2;
1620 int rc, nr_pages;
1621
1622 for (pass = 0; pass < NR_MAX_MIGRATE_PAGES_RETRY && retry; pass++) {
1623 retry = 0;
1624 nr_retry_pages = 0;
1625
1626 list_for_each_entry_safe(folio, folio2, from, lru) {
1627 if (!folio_test_hugetlb(folio))
1628 continue;
1629
1630 nr_pages = folio_nr_pages(folio);
1631
1632 cond_resched();
1633
1634 /*
1635 * Migratability of hugepages depends on architectures and
1636 * their size. This check is necessary because some callers
1637 * of hugepage migration like soft offline and memory
1638 * hotremove don't walk through page tables or check whether
1639 * the hugepage is pmd-based or not before kicking migration.
1640 */
1641 if (!hugepage_migration_supported(folio_hstate(folio))) {
1642 nr_failed++;
1643 stats->nr_failed_pages += nr_pages;
1644 list_move_tail(&folio->lru, ret_folios);
1645 continue;
1646 }
1647
1648 rc = unmap_and_move_huge_page(get_new_folio,
1649 put_new_folio, private,
1650 folio, pass > 2, mode,
1651 reason, ret_folios);
1652 /*
1653 * The rules are:
1654 * Success: hugetlb folio will be put back
1655 * -EAGAIN: stay on the from list
1656 * -ENOMEM: stay on the from list
1657 * Other errno: put on ret_folios list
1658 */
1659 switch(rc) {
1660 case -ENOMEM:
1661 /*
1662 * When memory is low, don't bother to try to migrate
1663 * other folios, just exit.
1664 */
1665 stats->nr_failed_pages += nr_pages + nr_retry_pages;
1666 return -ENOMEM;
1667 case -EAGAIN:
1668 retry++;
1669 nr_retry_pages += nr_pages;
1670 break;
1671 case MIGRATEPAGE_SUCCESS:
1672 stats->nr_succeeded += nr_pages;
1673 break;
1674 default:
1675 /*
1676 * Permanent failure (-EBUSY, etc.):
1677 * unlike -EAGAIN case, the failed folio is
1678 * removed from migration folio list and not
1679 * retried in the next outer loop.
1680 */
1681 nr_failed++;
1682 stats->nr_failed_pages += nr_pages;
1683 break;
1684 }
1685 }
1686 }
1687 /*
1688 * nr_failed is number of hugetlb folios failed to be migrated. After
1689 * NR_MAX_MIGRATE_PAGES_RETRY attempts, give up and count retried hugetlb
1690 * folios as failed.
1691 */
1692 nr_failed += retry;
1693 stats->nr_failed_pages += nr_retry_pages;
1694
1695 return nr_failed;
1696}
1697
1698/*
1699 * migrate_pages_batch() first unmaps folios in the from list as many as
1700 * possible, then move the unmapped folios.
1701 *
1702 * We only batch migration if mode == MIGRATE_ASYNC to avoid to wait a
1703 * lock or bit when we have locked more than one folio. Which may cause
1704 * deadlock (e.g., for loop device). So, if mode != MIGRATE_ASYNC, the
1705 * length of the from list must be <= 1.
1706 */
1707static int migrate_pages_batch(struct list_head *from,
1708 new_folio_t get_new_folio, free_folio_t put_new_folio,
1709 unsigned long private, enum migrate_mode mode, int reason,
1710 struct list_head *ret_folios, struct list_head *split_folios,
1711 struct migrate_pages_stats *stats, int nr_pass)
1712{
1713 int retry = 1;
1714 int thp_retry = 1;
1715 int nr_failed = 0;
1716 int nr_retry_pages = 0;
1717 int pass = 0;
1718 bool is_thp = false;
1719 bool is_large = false;
1720 struct folio *folio, *folio2, *dst = NULL, *dst2;
1721 int rc, rc_saved = 0, nr_pages;
1722 LIST_HEAD(unmap_folios);
1723 LIST_HEAD(dst_folios);
1724 bool nosplit = (reason == MR_NUMA_MISPLACED);
1725
1726 VM_WARN_ON_ONCE(mode != MIGRATE_ASYNC &&
1727 !list_empty(from) && !list_is_singular(from));
1728
1729 for (pass = 0; pass < nr_pass && retry; pass++) {
1730 retry = 0;
1731 thp_retry = 0;
1732 nr_retry_pages = 0;
1733
1734 list_for_each_entry_safe(folio, folio2, from, lru) {
1735 is_large = folio_test_large(folio);
1736 is_thp = folio_test_pmd_mappable(folio);
1737 nr_pages = folio_nr_pages(folio);
1738
1739 cond_resched();
1740
1741 /*
1742 * The rare folio on the deferred split list should
1743 * be split now. It should not count as a failure:
1744 * but increment nr_failed because, without doing so,
1745 * migrate_pages() may report success with (split but
1746 * unmigrated) pages still on its fromlist; whereas it
1747 * always reports success when its fromlist is empty.
1748 * stats->nr_thp_failed should be increased too,
1749 * otherwise stats inconsistency will happen when
1750 * migrate_pages_batch is called via migrate_pages()
1751 * with MIGRATE_SYNC and MIGRATE_ASYNC.
1752 *
1753 * Only check it without removing it from the list.
1754 * Since the folio can be on deferred_split_scan()
1755 * local list and removing it can cause the local list
1756 * corruption. Folio split process below can handle it
1757 * with the help of folio_ref_freeze().
1758 *
1759 * nr_pages > 2 is needed to avoid checking order-1
1760 * page cache folios. They exist, in contrast to
1761 * non-existent order-1 anonymous folios, and do not
1762 * use _deferred_list.
1763 */
1764 if (nr_pages > 2 &&
1765 !list_empty(&folio->_deferred_list) &&
1766 folio_test_partially_mapped(folio)) {
1767 if (!try_split_folio(folio, split_folios, mode)) {
1768 nr_failed++;
1769 stats->nr_thp_failed += is_thp;
1770 stats->nr_thp_split += is_thp;
1771 stats->nr_split++;
1772 continue;
1773 }
1774 }
1775
1776 /*
1777 * Large folio migration might be unsupported or
1778 * the allocation might be failed so we should retry
1779 * on the same folio with the large folio split
1780 * to normal folios.
1781 *
1782 * Split folios are put in split_folios, and
1783 * we will migrate them after the rest of the
1784 * list is processed.
1785 */
1786 if (!thp_migration_supported() && is_thp) {
1787 nr_failed++;
1788 stats->nr_thp_failed++;
1789 if (!try_split_folio(folio, split_folios, mode)) {
1790 stats->nr_thp_split++;
1791 stats->nr_split++;
1792 continue;
1793 }
1794 stats->nr_failed_pages += nr_pages;
1795 list_move_tail(&folio->lru, ret_folios);
1796 continue;
1797 }
1798
1799 rc = migrate_folio_unmap(get_new_folio, put_new_folio,
1800 private, folio, &dst, mode, reason,
1801 ret_folios);
1802 /*
1803 * The rules are:
1804 * Success: folio will be freed
1805 * Unmap: folio will be put on unmap_folios list,
1806 * dst folio put on dst_folios list
1807 * -EAGAIN: stay on the from list
1808 * -ENOMEM: stay on the from list
1809 * Other errno: put on ret_folios list
1810 */
1811 switch(rc) {
1812 case -ENOMEM:
1813 /*
1814 * When memory is low, don't bother to try to migrate
1815 * other folios, move unmapped folios, then exit.
1816 */
1817 nr_failed++;
1818 stats->nr_thp_failed += is_thp;
1819 /* Large folio NUMA faulting doesn't split to retry. */
1820 if (is_large && !nosplit) {
1821 int ret = try_split_folio(folio, split_folios, mode);
1822
1823 if (!ret) {
1824 stats->nr_thp_split += is_thp;
1825 stats->nr_split++;
1826 break;
1827 } else if (reason == MR_LONGTERM_PIN &&
1828 ret == -EAGAIN) {
1829 /*
1830 * Try again to split large folio to
1831 * mitigate the failure of longterm pinning.
1832 */
1833 retry++;
1834 thp_retry += is_thp;
1835 nr_retry_pages += nr_pages;
1836 /* Undo duplicated failure counting. */
1837 nr_failed--;
1838 stats->nr_thp_failed -= is_thp;
1839 break;
1840 }
1841 }
1842
1843 stats->nr_failed_pages += nr_pages + nr_retry_pages;
1844 /* nr_failed isn't updated for not used */
1845 stats->nr_thp_failed += thp_retry;
1846 rc_saved = rc;
1847 if (list_empty(&unmap_folios))
1848 goto out;
1849 else
1850 goto move;
1851 case -EAGAIN:
1852 retry++;
1853 thp_retry += is_thp;
1854 nr_retry_pages += nr_pages;
1855 break;
1856 case MIGRATEPAGE_SUCCESS:
1857 stats->nr_succeeded += nr_pages;
1858 stats->nr_thp_succeeded += is_thp;
1859 break;
1860 case MIGRATEPAGE_UNMAP:
1861 list_move_tail(&folio->lru, &unmap_folios);
1862 list_add_tail(&dst->lru, &dst_folios);
1863 break;
1864 default:
1865 /*
1866 * Permanent failure (-EBUSY, etc.):
1867 * unlike -EAGAIN case, the failed folio is
1868 * removed from migration folio list and not
1869 * retried in the next outer loop.
1870 */
1871 nr_failed++;
1872 stats->nr_thp_failed += is_thp;
1873 stats->nr_failed_pages += nr_pages;
1874 break;
1875 }
1876 }
1877 }
1878 nr_failed += retry;
1879 stats->nr_thp_failed += thp_retry;
1880 stats->nr_failed_pages += nr_retry_pages;
1881move:
1882 /* Flush TLBs for all unmapped folios */
1883 try_to_unmap_flush();
1884
1885 retry = 1;
1886 for (pass = 0; pass < nr_pass && retry; pass++) {
1887 retry = 0;
1888 thp_retry = 0;
1889 nr_retry_pages = 0;
1890
1891 dst = list_first_entry(&dst_folios, struct folio, lru);
1892 dst2 = list_next_entry(dst, lru);
1893 list_for_each_entry_safe(folio, folio2, &unmap_folios, lru) {
1894 is_thp = folio_test_large(folio) && folio_test_pmd_mappable(folio);
1895 nr_pages = folio_nr_pages(folio);
1896
1897 cond_resched();
1898
1899 rc = migrate_folio_move(put_new_folio, private,
1900 folio, dst, mode,
1901 reason, ret_folios);
1902 /*
1903 * The rules are:
1904 * Success: folio will be freed
1905 * -EAGAIN: stay on the unmap_folios list
1906 * Other errno: put on ret_folios list
1907 */
1908 switch(rc) {
1909 case -EAGAIN:
1910 retry++;
1911 thp_retry += is_thp;
1912 nr_retry_pages += nr_pages;
1913 break;
1914 case MIGRATEPAGE_SUCCESS:
1915 stats->nr_succeeded += nr_pages;
1916 stats->nr_thp_succeeded += is_thp;
1917 break;
1918 default:
1919 nr_failed++;
1920 stats->nr_thp_failed += is_thp;
1921 stats->nr_failed_pages += nr_pages;
1922 break;
1923 }
1924 dst = dst2;
1925 dst2 = list_next_entry(dst, lru);
1926 }
1927 }
1928 nr_failed += retry;
1929 stats->nr_thp_failed += thp_retry;
1930 stats->nr_failed_pages += nr_retry_pages;
1931
1932 rc = rc_saved ? : nr_failed;
1933out:
1934 /* Cleanup remaining folios */
1935 dst = list_first_entry(&dst_folios, struct folio, lru);
1936 dst2 = list_next_entry(dst, lru);
1937 list_for_each_entry_safe(folio, folio2, &unmap_folios, lru) {
1938 int old_page_state = 0;
1939 struct anon_vma *anon_vma = NULL;
1940
1941 __migrate_folio_extract(dst, &old_page_state, &anon_vma);
1942 migrate_folio_undo_src(folio, old_page_state & PAGE_WAS_MAPPED,
1943 anon_vma, true, ret_folios);
1944 list_del(&dst->lru);
1945 migrate_folio_undo_dst(dst, true, put_new_folio, private);
1946 dst = dst2;
1947 dst2 = list_next_entry(dst, lru);
1948 }
1949
1950 return rc;
1951}
1952
1953static int migrate_pages_sync(struct list_head *from, new_folio_t get_new_folio,
1954 free_folio_t put_new_folio, unsigned long private,
1955 enum migrate_mode mode, int reason,
1956 struct list_head *ret_folios, struct list_head *split_folios,
1957 struct migrate_pages_stats *stats)
1958{
1959 int rc, nr_failed = 0;
1960 LIST_HEAD(folios);
1961 struct migrate_pages_stats astats;
1962
1963 memset(&astats, 0, sizeof(astats));
1964 /* Try to migrate in batch with MIGRATE_ASYNC mode firstly */
1965 rc = migrate_pages_batch(from, get_new_folio, put_new_folio, private, MIGRATE_ASYNC,
1966 reason, &folios, split_folios, &astats,
1967 NR_MAX_MIGRATE_ASYNC_RETRY);
1968 stats->nr_succeeded += astats.nr_succeeded;
1969 stats->nr_thp_succeeded += astats.nr_thp_succeeded;
1970 stats->nr_thp_split += astats.nr_thp_split;
1971 stats->nr_split += astats.nr_split;
1972 if (rc < 0) {
1973 stats->nr_failed_pages += astats.nr_failed_pages;
1974 stats->nr_thp_failed += astats.nr_thp_failed;
1975 list_splice_tail(&folios, ret_folios);
1976 return rc;
1977 }
1978 stats->nr_thp_failed += astats.nr_thp_split;
1979 /*
1980 * Do not count rc, as pages will be retried below.
1981 * Count nr_split only, since it includes nr_thp_split.
1982 */
1983 nr_failed += astats.nr_split;
1984 /*
1985 * Fall back to migrate all failed folios one by one synchronously. All
1986 * failed folios except split THPs will be retried, so their failure
1987 * isn't counted
1988 */
1989 list_splice_tail_init(&folios, from);
1990 while (!list_empty(from)) {
1991 list_move(from->next, &folios);
1992 rc = migrate_pages_batch(&folios, get_new_folio, put_new_folio,
1993 private, mode, reason, ret_folios,
1994 split_folios, stats, NR_MAX_MIGRATE_SYNC_RETRY);
1995 list_splice_tail_init(&folios, ret_folios);
1996 if (rc < 0)
1997 return rc;
1998 nr_failed += rc;
1999 }
2000
2001 return nr_failed;
2002}
2003
2004/*
2005 * migrate_pages - migrate the folios specified in a list, to the free folios
2006 * supplied as the target for the page migration
2007 *
2008 * @from: The list of folios to be migrated.
2009 * @get_new_folio: The function used to allocate free folios to be used
2010 * as the target of the folio migration.
2011 * @put_new_folio: The function used to free target folios if migration
2012 * fails, or NULL if no special handling is necessary.
2013 * @private: Private data to be passed on to get_new_folio()
2014 * @mode: The migration mode that specifies the constraints for
2015 * folio migration, if any.
2016 * @reason: The reason for folio migration.
2017 * @ret_succeeded: Set to the number of folios migrated successfully if
2018 * the caller passes a non-NULL pointer.
2019 *
2020 * The function returns after NR_MAX_MIGRATE_PAGES_RETRY attempts or if no folios
2021 * are movable any more because the list has become empty or no retryable folios
2022 * exist any more. It is caller's responsibility to call putback_movable_pages()
2023 * only if ret != 0.
2024 *
2025 * Returns the number of {normal folio, large folio, hugetlb} that were not
2026 * migrated, or an error code. The number of large folio splits will be
2027 * considered as the number of non-migrated large folio, no matter how many
2028 * split folios of the large folio are migrated successfully.
2029 */
2030int migrate_pages(struct list_head *from, new_folio_t get_new_folio,
2031 free_folio_t put_new_folio, unsigned long private,
2032 enum migrate_mode mode, int reason, unsigned int *ret_succeeded)
2033{
2034 int rc, rc_gather;
2035 int nr_pages;
2036 struct folio *folio, *folio2;
2037 LIST_HEAD(folios);
2038 LIST_HEAD(ret_folios);
2039 LIST_HEAD(split_folios);
2040 struct migrate_pages_stats stats;
2041
2042 trace_mm_migrate_pages_start(mode, reason);
2043
2044 memset(&stats, 0, sizeof(stats));
2045
2046 rc_gather = migrate_hugetlbs(from, get_new_folio, put_new_folio, private,
2047 mode, reason, &stats, &ret_folios);
2048 if (rc_gather < 0)
2049 goto out;
2050
2051again:
2052 nr_pages = 0;
2053 list_for_each_entry_safe(folio, folio2, from, lru) {
2054 /* Retried hugetlb folios will be kept in list */
2055 if (folio_test_hugetlb(folio)) {
2056 list_move_tail(&folio->lru, &ret_folios);
2057 continue;
2058 }
2059
2060 nr_pages += folio_nr_pages(folio);
2061 if (nr_pages >= NR_MAX_BATCHED_MIGRATION)
2062 break;
2063 }
2064 if (nr_pages >= NR_MAX_BATCHED_MIGRATION)
2065 list_cut_before(&folios, from, &folio2->lru);
2066 else
2067 list_splice_init(from, &folios);
2068 if (mode == MIGRATE_ASYNC)
2069 rc = migrate_pages_batch(&folios, get_new_folio, put_new_folio,
2070 private, mode, reason, &ret_folios,
2071 &split_folios, &stats,
2072 NR_MAX_MIGRATE_PAGES_RETRY);
2073 else
2074 rc = migrate_pages_sync(&folios, get_new_folio, put_new_folio,
2075 private, mode, reason, &ret_folios,
2076 &split_folios, &stats);
2077 list_splice_tail_init(&folios, &ret_folios);
2078 if (rc < 0) {
2079 rc_gather = rc;
2080 list_splice_tail(&split_folios, &ret_folios);
2081 goto out;
2082 }
2083 if (!list_empty(&split_folios)) {
2084 /*
2085 * Failure isn't counted since all split folios of a large folio
2086 * is counted as 1 failure already. And, we only try to migrate
2087 * with minimal effort, force MIGRATE_ASYNC mode and retry once.
2088 */
2089 migrate_pages_batch(&split_folios, get_new_folio,
2090 put_new_folio, private, MIGRATE_ASYNC, reason,
2091 &ret_folios, NULL, &stats, 1);
2092 list_splice_tail_init(&split_folios, &ret_folios);
2093 }
2094 rc_gather += rc;
2095 if (!list_empty(from))
2096 goto again;
2097out:
2098 /*
2099 * Put the permanent failure folio back to migration list, they
2100 * will be put back to the right list by the caller.
2101 */
2102 list_splice(&ret_folios, from);
2103
2104 /*
2105 * Return 0 in case all split folios of fail-to-migrate large folios
2106 * are migrated successfully.
2107 */
2108 if (list_empty(from))
2109 rc_gather = 0;
2110
2111 count_vm_events(PGMIGRATE_SUCCESS, stats.nr_succeeded);
2112 count_vm_events(PGMIGRATE_FAIL, stats.nr_failed_pages);
2113 count_vm_events(THP_MIGRATION_SUCCESS, stats.nr_thp_succeeded);
2114 count_vm_events(THP_MIGRATION_FAIL, stats.nr_thp_failed);
2115 count_vm_events(THP_MIGRATION_SPLIT, stats.nr_thp_split);
2116 trace_mm_migrate_pages(stats.nr_succeeded, stats.nr_failed_pages,
2117 stats.nr_thp_succeeded, stats.nr_thp_failed,
2118 stats.nr_thp_split, stats.nr_split, mode,
2119 reason);
2120
2121 if (ret_succeeded)
2122 *ret_succeeded = stats.nr_succeeded;
2123
2124 return rc_gather;
2125}
2126
2127struct folio *alloc_migration_target(struct folio *src, unsigned long private)
2128{
2129 struct migration_target_control *mtc;
2130 gfp_t gfp_mask;
2131 unsigned int order = 0;
2132 int nid;
2133 int zidx;
2134
2135 mtc = (struct migration_target_control *)private;
2136 gfp_mask = mtc->gfp_mask;
2137 nid = mtc->nid;
2138 if (nid == NUMA_NO_NODE)
2139 nid = folio_nid(src);
2140
2141 if (folio_test_hugetlb(src)) {
2142 struct hstate *h = folio_hstate(src);
2143
2144 gfp_mask = htlb_modify_alloc_mask(h, gfp_mask);
2145 return alloc_hugetlb_folio_nodemask(h, nid,
2146 mtc->nmask, gfp_mask,
2147 htlb_allow_alloc_fallback(mtc->reason));
2148 }
2149
2150 if (folio_test_large(src)) {
2151 /*
2152 * clear __GFP_RECLAIM to make the migration callback
2153 * consistent with regular THP allocations.
2154 */
2155 gfp_mask &= ~__GFP_RECLAIM;
2156 gfp_mask |= GFP_TRANSHUGE;
2157 order = folio_order(src);
2158 }
2159 zidx = zone_idx(folio_zone(src));
2160 if (is_highmem_idx(zidx) || zidx == ZONE_MOVABLE)
2161 gfp_mask |= __GFP_HIGHMEM;
2162
2163 return __folio_alloc(gfp_mask, order, nid, mtc->nmask);
2164}
2165
2166#ifdef CONFIG_NUMA
2167
2168static int store_status(int __user *status, int start, int value, int nr)
2169{
2170 while (nr-- > 0) {
2171 if (put_user(value, status + start))
2172 return -EFAULT;
2173 start++;
2174 }
2175
2176 return 0;
2177}
2178
2179static int do_move_pages_to_node(struct list_head *pagelist, int node)
2180{
2181 int err;
2182 struct migration_target_control mtc = {
2183 .nid = node,
2184 .gfp_mask = GFP_HIGHUSER_MOVABLE | __GFP_THISNODE,
2185 .reason = MR_SYSCALL,
2186 };
2187
2188 err = migrate_pages(pagelist, alloc_migration_target, NULL,
2189 (unsigned long)&mtc, MIGRATE_SYNC, MR_SYSCALL, NULL);
2190 if (err)
2191 putback_movable_pages(pagelist);
2192 return err;
2193}
2194
2195static int __add_folio_for_migration(struct folio *folio, int node,
2196 struct list_head *pagelist, bool migrate_all)
2197{
2198 if (is_zero_folio(folio) || is_huge_zero_folio(folio))
2199 return -EFAULT;
2200
2201 if (folio_is_zone_device(folio))
2202 return -ENOENT;
2203
2204 if (folio_nid(folio) == node)
2205 return 0;
2206
2207 if (folio_likely_mapped_shared(folio) && !migrate_all)
2208 return -EACCES;
2209
2210 if (folio_test_hugetlb(folio)) {
2211 if (isolate_hugetlb(folio, pagelist))
2212 return 1;
2213 } else if (folio_isolate_lru(folio)) {
2214 list_add_tail(&folio->lru, pagelist);
2215 node_stat_mod_folio(folio,
2216 NR_ISOLATED_ANON + folio_is_file_lru(folio),
2217 folio_nr_pages(folio));
2218 return 1;
2219 }
2220 return -EBUSY;
2221}
2222
2223/*
2224 * Resolves the given address to a struct folio, isolates it from the LRU and
2225 * puts it to the given pagelist.
2226 * Returns:
2227 * errno - if the folio cannot be found/isolated
2228 * 0 - when it doesn't have to be migrated because it is already on the
2229 * target node
2230 * 1 - when it has been queued
2231 */
2232static int add_folio_for_migration(struct mm_struct *mm, const void __user *p,
2233 int node, struct list_head *pagelist, bool migrate_all)
2234{
2235 struct vm_area_struct *vma;
2236 struct folio_walk fw;
2237 struct folio *folio;
2238 unsigned long addr;
2239 int err = -EFAULT;
2240
2241 mmap_read_lock(mm);
2242 addr = (unsigned long)untagged_addr_remote(mm, p);
2243
2244 vma = vma_lookup(mm, addr);
2245 if (vma && vma_migratable(vma)) {
2246 folio = folio_walk_start(&fw, vma, addr, FW_ZEROPAGE);
2247 if (folio) {
2248 err = __add_folio_for_migration(folio, node, pagelist,
2249 migrate_all);
2250 folio_walk_end(&fw, vma);
2251 } else {
2252 err = -ENOENT;
2253 }
2254 }
2255 mmap_read_unlock(mm);
2256 return err;
2257}
2258
2259static int move_pages_and_store_status(int node,
2260 struct list_head *pagelist, int __user *status,
2261 int start, int i, unsigned long nr_pages)
2262{
2263 int err;
2264
2265 if (list_empty(pagelist))
2266 return 0;
2267
2268 err = do_move_pages_to_node(pagelist, node);
2269 if (err) {
2270 /*
2271 * Positive err means the number of failed
2272 * pages to migrate. Since we are going to
2273 * abort and return the number of non-migrated
2274 * pages, so need to include the rest of the
2275 * nr_pages that have not been attempted as
2276 * well.
2277 */
2278 if (err > 0)
2279 err += nr_pages - i;
2280 return err;
2281 }
2282 return store_status(status, start, node, i - start);
2283}
2284
2285/*
2286 * Migrate an array of page address onto an array of nodes and fill
2287 * the corresponding array of status.
2288 */
2289static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
2290 unsigned long nr_pages,
2291 const void __user * __user *pages,
2292 const int __user *nodes,
2293 int __user *status, int flags)
2294{
2295 compat_uptr_t __user *compat_pages = (void __user *)pages;
2296 int current_node = NUMA_NO_NODE;
2297 LIST_HEAD(pagelist);
2298 int start, i;
2299 int err = 0, err1;
2300
2301 lru_cache_disable();
2302
2303 for (i = start = 0; i < nr_pages; i++) {
2304 const void __user *p;
2305 int node;
2306
2307 err = -EFAULT;
2308 if (in_compat_syscall()) {
2309 compat_uptr_t cp;
2310
2311 if (get_user(cp, compat_pages + i))
2312 goto out_flush;
2313
2314 p = compat_ptr(cp);
2315 } else {
2316 if (get_user(p, pages + i))
2317 goto out_flush;
2318 }
2319 if (get_user(node, nodes + i))
2320 goto out_flush;
2321
2322 err = -ENODEV;
2323 if (node < 0 || node >= MAX_NUMNODES)
2324 goto out_flush;
2325 if (!node_state(node, N_MEMORY))
2326 goto out_flush;
2327
2328 err = -EACCES;
2329 if (!node_isset(node, task_nodes))
2330 goto out_flush;
2331
2332 if (current_node == NUMA_NO_NODE) {
2333 current_node = node;
2334 start = i;
2335 } else if (node != current_node) {
2336 err = move_pages_and_store_status(current_node,
2337 &pagelist, status, start, i, nr_pages);
2338 if (err)
2339 goto out;
2340 start = i;
2341 current_node = node;
2342 }
2343
2344 /*
2345 * Errors in the page lookup or isolation are not fatal and we simply
2346 * report them via status
2347 */
2348 err = add_folio_for_migration(mm, p, current_node, &pagelist,
2349 flags & MPOL_MF_MOVE_ALL);
2350
2351 if (err > 0) {
2352 /* The page is successfully queued for migration */
2353 continue;
2354 }
2355
2356 /*
2357 * The move_pages() man page does not have an -EEXIST choice, so
2358 * use -EFAULT instead.
2359 */
2360 if (err == -EEXIST)
2361 err = -EFAULT;
2362
2363 /*
2364 * If the page is already on the target node (!err), store the
2365 * node, otherwise, store the err.
2366 */
2367 err = store_status(status, i, err ? : current_node, 1);
2368 if (err)
2369 goto out_flush;
2370
2371 err = move_pages_and_store_status(current_node, &pagelist,
2372 status, start, i, nr_pages);
2373 if (err) {
2374 /* We have accounted for page i */
2375 if (err > 0)
2376 err--;
2377 goto out;
2378 }
2379 current_node = NUMA_NO_NODE;
2380 }
2381out_flush:
2382 /* Make sure we do not overwrite the existing error */
2383 err1 = move_pages_and_store_status(current_node, &pagelist,
2384 status, start, i, nr_pages);
2385 if (err >= 0)
2386 err = err1;
2387out:
2388 lru_cache_enable();
2389 return err;
2390}
2391
2392/*
2393 * Determine the nodes of an array of pages and store it in an array of status.
2394 */
2395static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
2396 const void __user **pages, int *status)
2397{
2398 unsigned long i;
2399
2400 mmap_read_lock(mm);
2401
2402 for (i = 0; i < nr_pages; i++) {
2403 unsigned long addr = (unsigned long)(*pages);
2404 struct vm_area_struct *vma;
2405 struct folio_walk fw;
2406 struct folio *folio;
2407 int err = -EFAULT;
2408
2409 vma = vma_lookup(mm, addr);
2410 if (!vma)
2411 goto set_status;
2412
2413 folio = folio_walk_start(&fw, vma, addr, FW_ZEROPAGE);
2414 if (folio) {
2415 if (is_zero_folio(folio) || is_huge_zero_folio(folio))
2416 err = -EFAULT;
2417 else if (folio_is_zone_device(folio))
2418 err = -ENOENT;
2419 else
2420 err = folio_nid(folio);
2421 folio_walk_end(&fw, vma);
2422 } else {
2423 err = -ENOENT;
2424 }
2425set_status:
2426 *status = err;
2427
2428 pages++;
2429 status++;
2430 }
2431
2432 mmap_read_unlock(mm);
2433}
2434
2435static int get_compat_pages_array(const void __user *chunk_pages[],
2436 const void __user * __user *pages,
2437 unsigned long chunk_nr)
2438{
2439 compat_uptr_t __user *pages32 = (compat_uptr_t __user *)pages;
2440 compat_uptr_t p;
2441 int i;
2442
2443 for (i = 0; i < chunk_nr; i++) {
2444 if (get_user(p, pages32 + i))
2445 return -EFAULT;
2446 chunk_pages[i] = compat_ptr(p);
2447 }
2448
2449 return 0;
2450}
2451
2452/*
2453 * Determine the nodes of a user array of pages and store it in
2454 * a user array of status.
2455 */
2456static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
2457 const void __user * __user *pages,
2458 int __user *status)
2459{
2460#define DO_PAGES_STAT_CHUNK_NR 16UL
2461 const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
2462 int chunk_status[DO_PAGES_STAT_CHUNK_NR];
2463
2464 while (nr_pages) {
2465 unsigned long chunk_nr = min(nr_pages, DO_PAGES_STAT_CHUNK_NR);
2466
2467 if (in_compat_syscall()) {
2468 if (get_compat_pages_array(chunk_pages, pages,
2469 chunk_nr))
2470 break;
2471 } else {
2472 if (copy_from_user(chunk_pages, pages,
2473 chunk_nr * sizeof(*chunk_pages)))
2474 break;
2475 }
2476
2477 do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
2478
2479 if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
2480 break;
2481
2482 pages += chunk_nr;
2483 status += chunk_nr;
2484 nr_pages -= chunk_nr;
2485 }
2486 return nr_pages ? -EFAULT : 0;
2487}
2488
2489static struct mm_struct *find_mm_struct(pid_t pid, nodemask_t *mem_nodes)
2490{
2491 struct task_struct *task;
2492 struct mm_struct *mm;
2493
2494 /*
2495 * There is no need to check if current process has the right to modify
2496 * the specified process when they are same.
2497 */
2498 if (!pid) {
2499 mmget(current->mm);
2500 *mem_nodes = cpuset_mems_allowed(current);
2501 return current->mm;
2502 }
2503
2504 task = find_get_task_by_vpid(pid);
2505 if (!task) {
2506 return ERR_PTR(-ESRCH);
2507 }
2508
2509 /*
2510 * Check if this process has the right to modify the specified
2511 * process. Use the regular "ptrace_may_access()" checks.
2512 */
2513 if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
2514 mm = ERR_PTR(-EPERM);
2515 goto out;
2516 }
2517
2518 mm = ERR_PTR(security_task_movememory(task));
2519 if (IS_ERR(mm))
2520 goto out;
2521 *mem_nodes = cpuset_mems_allowed(task);
2522 mm = get_task_mm(task);
2523out:
2524 put_task_struct(task);
2525 if (!mm)
2526 mm = ERR_PTR(-EINVAL);
2527 return mm;
2528}
2529
2530/*
2531 * Move a list of pages in the address space of the currently executing
2532 * process.
2533 */
2534static int kernel_move_pages(pid_t pid, unsigned long nr_pages,
2535 const void __user * __user *pages,
2536 const int __user *nodes,
2537 int __user *status, int flags)
2538{
2539 struct mm_struct *mm;
2540 int err;
2541 nodemask_t task_nodes;
2542
2543 /* Check flags */
2544 if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
2545 return -EINVAL;
2546
2547 if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
2548 return -EPERM;
2549
2550 mm = find_mm_struct(pid, &task_nodes);
2551 if (IS_ERR(mm))
2552 return PTR_ERR(mm);
2553
2554 if (nodes)
2555 err = do_pages_move(mm, task_nodes, nr_pages, pages,
2556 nodes, status, flags);
2557 else
2558 err = do_pages_stat(mm, nr_pages, pages, status);
2559
2560 mmput(mm);
2561 return err;
2562}
2563
2564SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
2565 const void __user * __user *, pages,
2566 const int __user *, nodes,
2567 int __user *, status, int, flags)
2568{
2569 return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags);
2570}
2571
2572#ifdef CONFIG_NUMA_BALANCING
2573/*
2574 * Returns true if this is a safe migration target node for misplaced NUMA
2575 * pages. Currently it only checks the watermarks which is crude.
2576 */
2577static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
2578 unsigned long nr_migrate_pages)
2579{
2580 int z;
2581
2582 for (z = pgdat->nr_zones - 1; z >= 0; z--) {
2583 struct zone *zone = pgdat->node_zones + z;
2584
2585 if (!managed_zone(zone))
2586 continue;
2587
2588 /* Avoid waking kswapd by allocating pages_to_migrate pages. */
2589 if (!zone_watermark_ok(zone, 0,
2590 high_wmark_pages(zone) +
2591 nr_migrate_pages,
2592 ZONE_MOVABLE, ALLOC_CMA))
2593 continue;
2594 return true;
2595 }
2596 return false;
2597}
2598
2599static struct folio *alloc_misplaced_dst_folio(struct folio *src,
2600 unsigned long data)
2601{
2602 int nid = (int) data;
2603 int order = folio_order(src);
2604 gfp_t gfp = __GFP_THISNODE;
2605
2606 if (order > 0)
2607 gfp |= GFP_TRANSHUGE_LIGHT;
2608 else {
2609 gfp |= GFP_HIGHUSER_MOVABLE | __GFP_NOMEMALLOC | __GFP_NORETRY |
2610 __GFP_NOWARN;
2611 gfp &= ~__GFP_RECLAIM;
2612 }
2613 return __folio_alloc_node(gfp, order, nid);
2614}
2615
2616/*
2617 * Prepare for calling migrate_misplaced_folio() by isolating the folio if
2618 * permitted. Must be called with the PTL still held.
2619 */
2620int migrate_misplaced_folio_prepare(struct folio *folio,
2621 struct vm_area_struct *vma, int node)
2622{
2623 int nr_pages = folio_nr_pages(folio);
2624 pg_data_t *pgdat = NODE_DATA(node);
2625
2626 if (folio_is_file_lru(folio)) {
2627 /*
2628 * Do not migrate file folios that are mapped in multiple
2629 * processes with execute permissions as they are probably
2630 * shared libraries.
2631 *
2632 * See folio_likely_mapped_shared() on possible imprecision
2633 * when we cannot easily detect if a folio is shared.
2634 */
2635 if ((vma->vm_flags & VM_EXEC) &&
2636 folio_likely_mapped_shared(folio))
2637 return -EACCES;
2638
2639 /*
2640 * Do not migrate dirty folios as not all filesystems can move
2641 * dirty folios in MIGRATE_ASYNC mode which is a waste of
2642 * cycles.
2643 */
2644 if (folio_test_dirty(folio))
2645 return -EAGAIN;
2646 }
2647
2648 /* Avoid migrating to a node that is nearly full */
2649 if (!migrate_balanced_pgdat(pgdat, nr_pages)) {
2650 int z;
2651
2652 if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING))
2653 return -EAGAIN;
2654 for (z = pgdat->nr_zones - 1; z >= 0; z--) {
2655 if (managed_zone(pgdat->node_zones + z))
2656 break;
2657 }
2658
2659 /*
2660 * If there are no managed zones, it should not proceed
2661 * further.
2662 */
2663 if (z < 0)
2664 return -EAGAIN;
2665
2666 wakeup_kswapd(pgdat->node_zones + z, 0,
2667 folio_order(folio), ZONE_MOVABLE);
2668 return -EAGAIN;
2669 }
2670
2671 if (!folio_isolate_lru(folio))
2672 return -EAGAIN;
2673
2674 node_stat_mod_folio(folio, NR_ISOLATED_ANON + folio_is_file_lru(folio),
2675 nr_pages);
2676 return 0;
2677}
2678
2679/*
2680 * Attempt to migrate a misplaced folio to the specified destination
2681 * node. Caller is expected to have isolated the folio by calling
2682 * migrate_misplaced_folio_prepare(), which will result in an
2683 * elevated reference count on the folio. This function will un-isolate the
2684 * folio, dereferencing the folio before returning.
2685 */
2686int migrate_misplaced_folio(struct folio *folio, struct vm_area_struct *vma,
2687 int node)
2688{
2689 pg_data_t *pgdat = NODE_DATA(node);
2690 int nr_remaining;
2691 unsigned int nr_succeeded;
2692 LIST_HEAD(migratepages);
2693 struct mem_cgroup *memcg = get_mem_cgroup_from_folio(folio);
2694 struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
2695
2696 list_add(&folio->lru, &migratepages);
2697 nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_folio,
2698 NULL, node, MIGRATE_ASYNC,
2699 MR_NUMA_MISPLACED, &nr_succeeded);
2700 if (nr_remaining && !list_empty(&migratepages))
2701 putback_movable_pages(&migratepages);
2702 if (nr_succeeded) {
2703 count_vm_numa_events(NUMA_PAGE_MIGRATE, nr_succeeded);
2704 count_memcg_events(memcg, NUMA_PAGE_MIGRATE, nr_succeeded);
2705 if ((sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING)
2706 && !node_is_toptier(folio_nid(folio))
2707 && node_is_toptier(node))
2708 mod_lruvec_state(lruvec, PGPROMOTE_SUCCESS, nr_succeeded);
2709 }
2710 mem_cgroup_put(memcg);
2711 BUG_ON(!list_empty(&migratepages));
2712 return nr_remaining ? -EAGAIN : 0;
2713}
2714#endif /* CONFIG_NUMA_BALANCING */
2715#endif /* CONFIG_NUMA */