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