1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Memory Migration functionality - linux/mm/migrate.c
4 *
5 * Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter
6 *
7 * Page migration was first developed in the context of the memory hotplug
8 * project. The main authors of the migration code are:
9 *
10 * IWAMOTO Toshihiro <iwamoto@valinux.co.jp>
11 * Hirokazu Takahashi <taka@valinux.co.jp>
12 * Dave Hansen <haveblue@us.ibm.com>
13 * Christoph Lameter
14 */
15
16 #include <linux/migrate.h>
17 #include <linux/export.h>
18 #include <linux/swap.h>
19 #include <linux/swapops.h>
20 #include <linux/pagemap.h>
21 #include <linux/buffer_head.h>
22 #include <linux/mm_inline.h>
23 #include <linux/nsproxy.h>
24 #include <linux/pagevec.h>
25 #include <linux/ksm.h>
26 #include <linux/rmap.h>
27 #include <linux/topology.h>
28 #include <linux/cpu.h>
29 #include <linux/cpuset.h>
30 #include <linux/writeback.h>
31 #include <linux/mempolicy.h>
32 #include <linux/vmalloc.h>
33 #include <linux/security.h>
34 #include <linux/backing-dev.h>
35 #include <linux/compaction.h>
36 #include <linux/syscalls.h>
37 #include <linux/compat.h>
38 #include <linux/hugetlb.h>
39 #include <linux/hugetlb_cgroup.h>
40 #include <linux/gfp.h>
41 #include <linux/pagewalk.h>
42 #include <linux/pfn_t.h>
43 #include <linux/memremap.h>
44 #include <linux/userfaultfd_k.h>
45 #include <linux/balloon_compaction.h>
46 #include <linux/mmu_notifier.h>
47 #include <linux/page_idle.h>
48 #include <linux/page_owner.h>
49 #include <linux/sched/mm.h>
50 #include <linux/ptrace.h>
51
52 #include <asm/tlbflush.h>
53
54 #define CREATE_TRACE_POINTS
55 #include <trace/events/migrate.h>
56
57 #include "internal.h"
58
59 /*
60 * migrate_prep() needs to be called before we start compiling a list of pages
61 * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
62 * undesirable, use migrate_prep_local()
63 */
64 int migrate_prep(void)
65 {
66 /*
67 * Clear the LRU lists so pages can be isolated.
68 * Note that pages may be moved off the LRU after we have
69 * drained them. Those pages will fail to migrate like other
70 * pages that may be busy.
71 */
72 lru_add_drain_all();
73
74 return 0;
75 }
76
77 /* Do the necessary work of migrate_prep but not if it involves other CPUs */
78 int migrate_prep_local(void)
79 {
80 lru_add_drain();
81
82 return 0;
83 }
84
85 int isolate_movable_page(struct page *page, isolate_mode_t mode)
86 {
87 struct address_space *mapping;
88
89 /*
90 * Avoid burning cycles with pages that are yet under __free_pages(),
91 * or just got freed under us.
92 *
93 * In case we 'win' a race for a movable page being freed under us and
94 * raise its refcount preventing __free_pages() from doing its job
95 * the put_page() at the end of this block will take care of
96 * release this page, thus avoiding a nasty leakage.
97 */
98 if (unlikely(!get_page_unless_zero(page)))
99 goto out;
100
101 /*
102 * Check PageMovable before holding a PG_lock because page's owner
103 * assumes anybody doesn't touch PG_lock of newly allocated page
104 * so unconditionally grabbing the lock ruins page's owner side.
105 */
106 if (unlikely(!__PageMovable(page)))
107 goto out_putpage;
108 /*
109 * As movable pages are not isolated from LRU lists, concurrent
110 * compaction threads can race against page migration functions
111 * as well as race against the releasing a page.
112 *
113 * In order to avoid having an already isolated movable page
114 * being (wrongly) re-isolated while it is under migration,
115 * or to avoid attempting to isolate pages being released,
116 * lets be sure we have the page lock
117 * before proceeding with the movable page isolation steps.
118 */
119 if (unlikely(!trylock_page(page)))
120 goto out_putpage;
121
122 if (!PageMovable(page) || PageIsolated(page))
123 goto out_no_isolated;
124
125 mapping = page_mapping(page);
126 VM_BUG_ON_PAGE(!mapping, page);
127
128 if (!mapping->a_ops->isolate_page(page, mode))
129 goto out_no_isolated;
130
131 /* Driver shouldn't use PG_isolated bit of page->flags */
132 WARN_ON_ONCE(PageIsolated(page));
133 __SetPageIsolated(page);
134 unlock_page(page);
135
136 return 0;
137
138 out_no_isolated:
139 unlock_page(page);
140 out_putpage:
141 put_page(page);
142 out:
143 return -EBUSY;
144 }
145
146 /* It should be called on page which is PG_movable */
147 void putback_movable_page(struct page *page)
148 {
149 struct address_space *mapping;
150
151 VM_BUG_ON_PAGE(!PageLocked(page), page);
152 VM_BUG_ON_PAGE(!PageMovable(page), page);
153 VM_BUG_ON_PAGE(!PageIsolated(page), page);
154
155 mapping = page_mapping(page);
156 mapping->a_ops->putback_page(page);
157 __ClearPageIsolated(page);
158 }
159
160 /*
161 * Put previously isolated pages back onto the appropriate lists
162 * from where they were once taken off for compaction/migration.
163 *
164 * This function shall be used whenever the isolated pageset has been
165 * built from lru, balloon, hugetlbfs page. See isolate_migratepages_range()
166 * and isolate_huge_page().
167 */
168 void putback_movable_pages(struct list_head *l)
169 {
170 struct page *page;
171 struct page *page2;
172
173 list_for_each_entry_safe(page, page2, l, lru) {
174 if (unlikely(PageHuge(page))) {
175 putback_active_hugepage(page);
176 continue;
177 }
178 list_del(&page->lru);
179 /*
180 * We isolated non-lru movable page so here we can use
181 * __PageMovable because LRU page's mapping cannot have
182 * PAGE_MAPPING_MOVABLE.
183 */
184 if (unlikely(__PageMovable(page))) {
185 VM_BUG_ON_PAGE(!PageIsolated(page), page);
186 lock_page(page);
187 if (PageMovable(page))
188 putback_movable_page(page);
189 else
190 __ClearPageIsolated(page);
191 unlock_page(page);
192 put_page(page);
193 } else {
194 mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
195 page_is_file_cache(page), -hpage_nr_pages(page));
196 putback_lru_page(page);
197 }
198 }
199 }
200
201 /*
202 * Restore a potential migration pte to a working pte entry
203 */
204 static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma,
205 unsigned long addr, void *old)
206 {
207 struct page_vma_mapped_walk pvmw = {
208 .page = old,
209 .vma = vma,
210 .address = addr,
211 .flags = PVMW_SYNC | PVMW_MIGRATION,
212 };
213 struct page *new;
214 pte_t pte;
215 swp_entry_t entry;
216
217 VM_BUG_ON_PAGE(PageTail(page), page);
218 while (page_vma_mapped_walk(&pvmw)) {
219 if (PageKsm(page))
220 new = page;
221 else
222 new = page - pvmw.page->index +
223 linear_page_index(vma, pvmw.address);
224
225 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
226 /* PMD-mapped THP migration entry */
227 if (!pvmw.pte) {
228 VM_BUG_ON_PAGE(PageHuge(page) || !PageTransCompound(page), page);
229 remove_migration_pmd(&pvmw, new);
230 continue;
231 }
232 #endif
233
234 get_page(new);
235 pte = pte_mkold(mk_pte(new, READ_ONCE(vma->vm_page_prot)));
236 if (pte_swp_soft_dirty(*pvmw.pte))
237 pte = pte_mksoft_dirty(pte);
238
239 /*
240 * Recheck VMA as permissions can change since migration started
241 */
242 entry = pte_to_swp_entry(*pvmw.pte);
243 if (is_write_migration_entry(entry))
244 pte = maybe_mkwrite(pte, vma);
245
246 if (unlikely(is_zone_device_page(new))) {
247 if (is_device_private_page(new)) {
248 entry = make_device_private_entry(new, pte_write(pte));
249 pte = swp_entry_to_pte(entry);
250 }
251 }
252
253 #ifdef CONFIG_HUGETLB_PAGE
254 if (PageHuge(new)) {
255 pte = pte_mkhuge(pte);
256 pte = arch_make_huge_pte(pte, vma, new, 0);
257 set_huge_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
258 if (PageAnon(new))
259 hugepage_add_anon_rmap(new, vma, pvmw.address);
260 else
261 page_dup_rmap(new, true);
262 } else
263 #endif
264 {
265 set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
266
267 if (PageAnon(new))
268 page_add_anon_rmap(new, vma, pvmw.address, false);
269 else
270 page_add_file_rmap(new, false);
271 }
272 if (vma->vm_flags & VM_LOCKED && !PageTransCompound(new))
273 mlock_vma_page(new);
274
275 if (PageTransHuge(page) && PageMlocked(page))
276 clear_page_mlock(page);
277
278 /* No need to invalidate - it was non-present before */
279 update_mmu_cache(vma, pvmw.address, pvmw.pte);
280 }
281
282 return true;
283 }
284
285 /*
286 * Get rid of all migration entries and replace them by
287 * references to the indicated page.
288 */
289 void 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 */
307 void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
308 spinlock_t *ptl)
309 {
310 pte_t pte;
311 swp_entry_t entry;
312 struct page *page;
313
314 spin_lock(ptl);
315 pte = *ptep;
316 if (!is_swap_pte(pte))
317 goto out;
318
319 entry = pte_to_swp_entry(pte);
320 if (!is_migration_entry(entry))
321 goto out;
322
323 page = migration_entry_to_page(entry);
324
325 /*
326 * Once page cache replacement of page migration started, page_count
327 * is zero; but we must not call put_and_wait_on_page_locked() without
328 * a ref. Use get_page_unless_zero(), and just fault again if it fails.
329 */
330 if (!get_page_unless_zero(page))
331 goto out;
332 pte_unmap_unlock(ptep, ptl);
333 put_and_wait_on_page_locked(page);
334 return;
335 out:
336 pte_unmap_unlock(ptep, ptl);
337 }
338
339 void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
340 unsigned long address)
341 {
342 spinlock_t *ptl = pte_lockptr(mm, pmd);
343 pte_t *ptep = pte_offset_map(pmd, address);
344 __migration_entry_wait(mm, ptep, ptl);
345 }
346
347 void migration_entry_wait_huge(struct vm_area_struct *vma,
348 struct mm_struct *mm, pte_t *pte)
349 {
350 spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), mm, pte);
351 __migration_entry_wait(mm, pte, ptl);
352 }
353
354 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
355 void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)
356 {
357 spinlock_t *ptl;
358 struct page *page;
359
360 ptl = pmd_lock(mm, pmd);
361 if (!is_pmd_migration_entry(*pmd))
362 goto unlock;
363 page = migration_entry_to_page(pmd_to_swp_entry(*pmd));
364 if (!get_page_unless_zero(page))
365 goto unlock;
366 spin_unlock(ptl);
367 put_and_wait_on_page_locked(page);
368 return;
369 unlock:
370 spin_unlock(ptl);
371 }
372 #endif
373
374 static int expected_page_refs(struct address_space *mapping, struct page *page)
375 {
376 int expected_count = 1;
377
378 /*
379 * Device public or private pages have an extra refcount as they are
380 * ZONE_DEVICE pages.
381 */
382 expected_count += is_device_private_page(page);
383 if (mapping)
384 expected_count += hpage_nr_pages(page) + page_has_private(page);
385
386 return expected_count;
387 }
388
389 /*
390 * Replace the page in the mapping.
391 *
392 * The number of remaining references must be:
393 * 1 for anonymous pages without a mapping
394 * 2 for pages with a mapping
395 * 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
396 */
397 int migrate_page_move_mapping(struct address_space *mapping,
398 struct page *newpage, struct page *page, int extra_count)
399 {
400 XA_STATE(xas, &mapping->i_pages, page_index(page));
401 struct zone *oldzone, *newzone;
402 int dirty;
403 int expected_count = expected_page_refs(mapping, page) + extra_count;
404
405 if (!mapping) {
406 /* Anonymous page without mapping */
407 if (page_count(page) != expected_count)
408 return -EAGAIN;
409
410 /* No turning back from here */
411 newpage->index = page->index;
412 newpage->mapping = page->mapping;
413 if (PageSwapBacked(page))
414 __SetPageSwapBacked(newpage);
415
416 return MIGRATEPAGE_SUCCESS;
417 }
418
419 oldzone = page_zone(page);
420 newzone = page_zone(newpage);
421
422 xas_lock_irq(&xas);
423 if (page_count(page) != expected_count || xas_load(&xas) != page) {
424 xas_unlock_irq(&xas);
425 return -EAGAIN;
426 }
427
428 if (!page_ref_freeze(page, expected_count)) {
429 xas_unlock_irq(&xas);
430 return -EAGAIN;
431 }
432
433 /*
434 * Now we know that no one else is looking at the page:
435 * no turning back from here.
436 */
437 newpage->index = page->index;
438 newpage->mapping = page->mapping;
439 page_ref_add(newpage, hpage_nr_pages(page)); /* add cache reference */
440 if (PageSwapBacked(page)) {
441 __SetPageSwapBacked(newpage);
442 if (PageSwapCache(page)) {
443 SetPageSwapCache(newpage);
444 set_page_private(newpage, page_private(page));
445 }
446 } else {
447 VM_BUG_ON_PAGE(PageSwapCache(page), page);
448 }
449
450 /* Move dirty while page refs frozen and newpage not yet exposed */
451 dirty = PageDirty(page);
452 if (dirty) {
453 ClearPageDirty(page);
454 SetPageDirty(newpage);
455 }
456
457 xas_store(&xas, newpage);
458 if (PageTransHuge(page)) {
459 int i;
460
461 for (i = 1; i < HPAGE_PMD_NR; i++) {
462 xas_next(&xas);
463 xas_store(&xas, newpage);
464 }
465 }
466
467 /*
468 * Drop cache reference from old page by unfreezing
469 * to one less reference.
470 * We know this isn't the last reference.
471 */
472 page_ref_unfreeze(page, expected_count - hpage_nr_pages(page));
473
474 xas_unlock(&xas);
475 /* Leave irq disabled to prevent preemption while updating stats */
476
477 /*
478 * If moved to a different zone then also account
479 * the page for that zone. Other VM counters will be
480 * taken care of when we establish references to the
481 * new page and drop references to the old page.
482 *
483 * Note that anonymous pages are accounted for
484 * via NR_FILE_PAGES and NR_ANON_MAPPED if they
485 * are mapped to swap space.
486 */
487 if (newzone != oldzone) {
488 __dec_node_state(oldzone->zone_pgdat, NR_FILE_PAGES);
489 __inc_node_state(newzone->zone_pgdat, NR_FILE_PAGES);
490 if (PageSwapBacked(page) && !PageSwapCache(page)) {
491 __dec_node_state(oldzone->zone_pgdat, NR_SHMEM);
492 __inc_node_state(newzone->zone_pgdat, NR_SHMEM);
493 }
494 if (dirty && mapping_cap_account_dirty(mapping)) {
495 __dec_node_state(oldzone->zone_pgdat, NR_FILE_DIRTY);
496 __dec_zone_state(oldzone, NR_ZONE_WRITE_PENDING);
497 __inc_node_state(newzone->zone_pgdat, NR_FILE_DIRTY);
498 __inc_zone_state(newzone, NR_ZONE_WRITE_PENDING);
499 }
500 }
501 local_irq_enable();
502
503 return MIGRATEPAGE_SUCCESS;
504 }
505 EXPORT_SYMBOL(migrate_page_move_mapping);
506
507 /*
508 * The expected number of remaining references is the same as that
509 * of migrate_page_move_mapping().
510 */
511 int migrate_huge_page_move_mapping(struct address_space *mapping,
512 struct page *newpage, struct page *page)
513 {
514 XA_STATE(xas, &mapping->i_pages, page_index(page));
515 int expected_count;
516
517 xas_lock_irq(&xas);
518 expected_count = 2 + page_has_private(page);
519 if (page_count(page) != expected_count || xas_load(&xas) != page) {
520 xas_unlock_irq(&xas);
521 return -EAGAIN;
522 }
523
524 if (!page_ref_freeze(page, expected_count)) {
525 xas_unlock_irq(&xas);
526 return -EAGAIN;
527 }
528
529 newpage->index = page->index;
530 newpage->mapping = page->mapping;
531
532 get_page(newpage);
533
534 xas_store(&xas, newpage);
535
536 page_ref_unfreeze(page, expected_count - 1);
537
538 xas_unlock_irq(&xas);
539
540 return MIGRATEPAGE_SUCCESS;
541 }
542
543 /*
544 * Gigantic pages are so large that we do not guarantee that page++ pointer
545 * arithmetic will work across the entire page. We need something more
546 * specialized.
547 */
548 static void __copy_gigantic_page(struct page *dst, struct page *src,
549 int nr_pages)
550 {
551 int i;
552 struct page *dst_base = dst;
553 struct page *src_base = src;
554
555 for (i = 0; i < nr_pages; ) {
556 cond_resched();
557 copy_highpage(dst, src);
558
559 i++;
560 dst = mem_map_next(dst, dst_base, i);
561 src = mem_map_next(src, src_base, i);
562 }
563 }
564
565 static void copy_huge_page(struct page *dst, struct page *src)
566 {
567 int i;
568 int nr_pages;
569
570 if (PageHuge(src)) {
571 /* hugetlbfs page */
572 struct hstate *h = page_hstate(src);
573 nr_pages = pages_per_huge_page(h);
574
575 if (unlikely(nr_pages > MAX_ORDER_NR_PAGES)) {
576 __copy_gigantic_page(dst, src, nr_pages);
577 return;
578 }
579 } else {
580 /* thp page */
581 BUG_ON(!PageTransHuge(src));
582 nr_pages = hpage_nr_pages(src);
583 }
584
585 for (i = 0; i < nr_pages; i++) {
586 cond_resched();
587 copy_highpage(dst + i, src + i);
588 }
589 }
590
591 /*
592 * Copy the page to its new location
593 */
594 void migrate_page_states(struct page *newpage, struct page *page)
595 {
596 int cpupid;
597
598 if (PageError(page))
599 SetPageError(newpage);
600 if (PageReferenced(page))
601 SetPageReferenced(newpage);
602 if (PageUptodate(page))
603 SetPageUptodate(newpage);
604 if (TestClearPageActive(page)) {
605 VM_BUG_ON_PAGE(PageUnevictable(page), page);
606 SetPageActive(newpage);
607 } else if (TestClearPageUnevictable(page))
608 SetPageUnevictable(newpage);
609 if (PageWorkingset(page))
610 SetPageWorkingset(newpage);
611 if (PageChecked(page))
612 SetPageChecked(newpage);
613 if (PageMappedToDisk(page))
614 SetPageMappedToDisk(newpage);
615
616 /* Move dirty on pages not done by migrate_page_move_mapping() */
617 if (PageDirty(page))
618 SetPageDirty(newpage);
619
620 if (page_is_young(page))
621 set_page_young(newpage);
622 if (page_is_idle(page))
623 set_page_idle(newpage);
624
625 /*
626 * Copy NUMA information to the new page, to prevent over-eager
627 * future migrations of this same page.
628 */
629 cpupid = page_cpupid_xchg_last(page, -1);
630 page_cpupid_xchg_last(newpage, cpupid);
631
632 ksm_migrate_page(newpage, page);
633 /*
634 * Please do not reorder this without considering how mm/ksm.c's
635 * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
636 */
637 if (PageSwapCache(page))
638 ClearPageSwapCache(page);
639 ClearPagePrivate(page);
640 set_page_private(page, 0);
641
642 /*
643 * If any waiters have accumulated on the new page then
644 * wake them up.
645 */
646 if (PageWriteback(newpage))
647 end_page_writeback(newpage);
648
649 copy_page_owner(page, newpage);
650
651 mem_cgroup_migrate(page, newpage);
652 }
653 EXPORT_SYMBOL(migrate_page_states);
654
655 void migrate_page_copy(struct page *newpage, struct page *page)
656 {
657 if (PageHuge(page) || PageTransHuge(page))
658 copy_huge_page(newpage, page);
659 else
660 copy_highpage(newpage, page);
661
662 migrate_page_states(newpage, page);
663 }
664 EXPORT_SYMBOL(migrate_page_copy);
665
666 /************************************************************
667 * Migration functions
668 ***********************************************************/
669
670 /*
671 * Common logic to directly migrate a single LRU page suitable for
672 * pages that do not use PagePrivate/PagePrivate2.
673 *
674 * Pages are locked upon entry and exit.
675 */
676 int migrate_page(struct address_space *mapping,
677 struct page *newpage, struct page *page,
678 enum migrate_mode mode)
679 {
680 int rc;
681
682 BUG_ON(PageWriteback(page)); /* Writeback must be complete */
683
684 rc = migrate_page_move_mapping(mapping, newpage, page, 0);
685
686 if (rc != MIGRATEPAGE_SUCCESS)
687 return rc;
688
689 if (mode != MIGRATE_SYNC_NO_COPY)
690 migrate_page_copy(newpage, page);
691 else
692 migrate_page_states(newpage, page);
693 return MIGRATEPAGE_SUCCESS;
694 }
695 EXPORT_SYMBOL(migrate_page);
696
697 #ifdef CONFIG_BLOCK
698 /* Returns true if all buffers are successfully locked */
699 static bool buffer_migrate_lock_buffers(struct buffer_head *head,
700 enum migrate_mode mode)
701 {
702 struct buffer_head *bh = head;
703
704 /* Simple case, sync compaction */
705 if (mode != MIGRATE_ASYNC) {
706 do {
707 lock_buffer(bh);
708 bh = bh->b_this_page;
709
710 } while (bh != head);
711
712 return true;
713 }
714
715 /* async case, we cannot block on lock_buffer so use trylock_buffer */
716 do {
717 if (!trylock_buffer(bh)) {
718 /*
719 * We failed to lock the buffer and cannot stall in
720 * async migration. Release the taken locks
721 */
722 struct buffer_head *failed_bh = bh;
723 bh = head;
724 while (bh != failed_bh) {
725 unlock_buffer(bh);
726 bh = bh->b_this_page;
727 }
728 return false;
729 }
730
731 bh = bh->b_this_page;
732 } while (bh != head);
733 return true;
734 }
735
736 static int __buffer_migrate_page(struct address_space *mapping,
737 struct page *newpage, struct page *page, enum migrate_mode mode,
738 bool check_refs)
739 {
740 struct buffer_head *bh, *head;
741 int rc;
742 int expected_count;
743
744 if (!page_has_buffers(page))
745 return migrate_page(mapping, newpage, page, mode);
746
747 /* Check whether page does not have extra refs before we do more work */
748 expected_count = expected_page_refs(mapping, page);
749 if (page_count(page) != expected_count)
750 return -EAGAIN;
751
752 head = page_buffers(page);
753 if (!buffer_migrate_lock_buffers(head, mode))
754 return -EAGAIN;
755
756 if (check_refs) {
757 bool busy;
758 bool invalidated = false;
759
760 recheck_buffers:
761 busy = false;
762 spin_lock(&mapping->private_lock);
763 bh = head;
764 do {
765 if (atomic_read(&bh->b_count)) {
766 busy = true;
767 break;
768 }
769 bh = bh->b_this_page;
770 } while (bh != head);
771 if (busy) {
772 if (invalidated) {
773 rc = -EAGAIN;
774 goto unlock_buffers;
775 }
776 spin_unlock(&mapping->private_lock);
777 invalidate_bh_lrus();
778 invalidated = true;
779 goto recheck_buffers;
780 }
781 }
782
783 rc = migrate_page_move_mapping(mapping, newpage, page, 0);
784 if (rc != MIGRATEPAGE_SUCCESS)
785 goto unlock_buffers;
786
787 ClearPagePrivate(page);
788 set_page_private(newpage, page_private(page));
789 set_page_private(page, 0);
790 put_page(page);
791 get_page(newpage);
792
793 bh = head;
794 do {
795 set_bh_page(bh, newpage, bh_offset(bh));
796 bh = bh->b_this_page;
797
798 } while (bh != head);
799
800 SetPagePrivate(newpage);
801
802 if (mode != MIGRATE_SYNC_NO_COPY)
803 migrate_page_copy(newpage, page);
804 else
805 migrate_page_states(newpage, page);
806
807 rc = MIGRATEPAGE_SUCCESS;
808 unlock_buffers:
809 if (check_refs)
810 spin_unlock(&mapping->private_lock);
811 bh = head;
812 do {
813 unlock_buffer(bh);
814 bh = bh->b_this_page;
815
816 } while (bh != head);
817
818 return rc;
819 }
820
821 /*
822 * Migration function for pages with buffers. This function can only be used
823 * if the underlying filesystem guarantees that no other references to "page"
824 * exist. For example attached buffer heads are accessed only under page lock.
825 */
826 int buffer_migrate_page(struct address_space *mapping,
827 struct page *newpage, struct page *page, enum migrate_mode mode)
828 {
829 return __buffer_migrate_page(mapping, newpage, page, mode, false);
830 }
831 EXPORT_SYMBOL(buffer_migrate_page);
832
833 /*
834 * Same as above except that this variant is more careful and checks that there
835 * are also no buffer head references. This function is the right one for
836 * mappings where buffer heads are directly looked up and referenced (such as
837 * block device mappings).
838 */
839 int buffer_migrate_page_norefs(struct address_space *mapping,
840 struct page *newpage, struct page *page, enum migrate_mode mode)
841 {
842 return __buffer_migrate_page(mapping, newpage, page, mode, true);
843 }
844 #endif
845
846 /*
847 * Writeback a page to clean the dirty state
848 */
849 static int writeout(struct address_space *mapping, struct page *page)
850 {
851 struct writeback_control wbc = {
852 .sync_mode = WB_SYNC_NONE,
853 .nr_to_write = 1,
854 .range_start = 0,
855 .range_end = LLONG_MAX,
856 .for_reclaim = 1
857 };
858 int rc;
859
860 if (!mapping->a_ops->writepage)
861 /* No write method for the address space */
862 return -EINVAL;
863
864 if (!clear_page_dirty_for_io(page))
865 /* Someone else already triggered a write */
866 return -EAGAIN;
867
868 /*
869 * A dirty page may imply that the underlying filesystem has
870 * the page on some queue. So the page must be clean for
871 * migration. Writeout may mean we loose the lock and the
872 * page state is no longer what we checked for earlier.
873 * At this point we know that the migration attempt cannot
874 * be successful.
875 */
876 remove_migration_ptes(page, page, false);
877
878 rc = mapping->a_ops->writepage(page, &wbc);
879
880 if (rc != AOP_WRITEPAGE_ACTIVATE)
881 /* unlocked. Relock */
882 lock_page(page);
883
884 return (rc < 0) ? -EIO : -EAGAIN;
885 }
886
887 /*
888 * Default handling if a filesystem does not provide a migration function.
889 */
890 static int fallback_migrate_page(struct address_space *mapping,
891 struct page *newpage, struct page *page, enum migrate_mode mode)
892 {
893 if (PageDirty(page)) {
894 /* Only writeback pages in full synchronous migration */
895 switch (mode) {
896 case MIGRATE_SYNC:
897 case MIGRATE_SYNC_NO_COPY:
898 break;
899 default:
900 return -EBUSY;
901 }
902 return writeout(mapping, page);
903 }
904
905 /*
906 * Buffers may be managed in a filesystem specific way.
907 * We must have no buffers or drop them.
908 */
909 if (page_has_private(page) &&
910 !try_to_release_page(page, GFP_KERNEL))
911 return mode == MIGRATE_SYNC ? -EAGAIN : -EBUSY;
912
913 return migrate_page(mapping, newpage, page, mode);
914 }
915
916 /*
917 * Move a page to a newly allocated page
918 * The page is locked and all ptes have been successfully removed.
919 *
920 * The new page will have replaced the old page if this function
921 * is successful.
922 *
923 * Return value:
924 * < 0 - error code
925 * MIGRATEPAGE_SUCCESS - success
926 */
927 static int move_to_new_page(struct page *newpage, struct page *page,
928 enum migrate_mode mode)
929 {
930 struct address_space *mapping;
931 int rc = -EAGAIN;
932 bool is_lru = !__PageMovable(page);
933
934 VM_BUG_ON_PAGE(!PageLocked(page), page);
935 VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
936
937 mapping = page_mapping(page);
938
939 if (likely(is_lru)) {
940 if (!mapping)
941 rc = migrate_page(mapping, newpage, page, mode);
942 else if (mapping->a_ops->migratepage)
943 /*
944 * Most pages have a mapping and most filesystems
945 * provide a migratepage callback. Anonymous pages
946 * are part of swap space which also has its own
947 * migratepage callback. This is the most common path
948 * for page migration.
949 */
950 rc = mapping->a_ops->migratepage(mapping, newpage,
951 page, mode);
952 else
953 rc = fallback_migrate_page(mapping, newpage,
954 page, mode);
955 } else {
956 /*
957 * In case of non-lru page, it could be released after
958 * isolation step. In that case, we shouldn't try migration.
959 */
960 VM_BUG_ON_PAGE(!PageIsolated(page), page);
961 if (!PageMovable(page)) {
962 rc = MIGRATEPAGE_SUCCESS;
963 __ClearPageIsolated(page);
964 goto out;
965 }
966
967 rc = mapping->a_ops->migratepage(mapping, newpage,
968 page, mode);
969 WARN_ON_ONCE(rc == MIGRATEPAGE_SUCCESS &&
970 !PageIsolated(page));
971 }
972
973 /*
974 * When successful, old pagecache page->mapping must be cleared before
975 * page is freed; but stats require that PageAnon be left as PageAnon.
976 */
977 if (rc == MIGRATEPAGE_SUCCESS) {
978 if (__PageMovable(page)) {
979 VM_BUG_ON_PAGE(!PageIsolated(page), page);
980
981 /*
982 * We clear PG_movable under page_lock so any compactor
983 * cannot try to migrate this page.
984 */
985 __ClearPageIsolated(page);
986 }
987
988 /*
989 * Anonymous and movable page->mapping will be cleard by
990 * free_pages_prepare so don't reset it here for keeping
991 * the type to work PageAnon, for example.
992 */
993 if (!PageMappingFlags(page))
994 page->mapping = NULL;
995
996 if (likely(!is_zone_device_page(newpage)))
997 flush_dcache_page(newpage);
998
999 }
1000 out:
1001 return rc;
1002 }
1003
1004 static int __unmap_and_move(struct page *page, struct page *newpage,
1005 int force, enum migrate_mode mode)
1006 {
1007 int rc = -EAGAIN;
1008 int page_was_mapped = 0;
1009 struct anon_vma *anon_vma = NULL;
1010 bool is_lru = !__PageMovable(page);
1011
1012 if (!trylock_page(page)) {
1013 if (!force || mode == MIGRATE_ASYNC)
1014 goto out;
1015
1016 /*
1017 * It's not safe for direct compaction to call lock_page.
1018 * For example, during page readahead pages are added locked
1019 * to the LRU. Later, when the IO completes the pages are
1020 * marked uptodate and unlocked. However, the queueing
1021 * could be merging multiple pages for one bio (e.g.
1022 * mpage_readpages). If an allocation happens for the
1023 * second or third page, the process can end up locking
1024 * the same page twice and deadlocking. Rather than
1025 * trying to be clever about what pages can be locked,
1026 * avoid the use of lock_page for direct compaction
1027 * altogether.
1028 */
1029 if (current->flags & PF_MEMALLOC)
1030 goto out;
1031
1032 lock_page(page);
1033 }
1034
1035 if (PageWriteback(page)) {
1036 /*
1037 * Only in the case of a full synchronous migration is it
1038 * necessary to wait for PageWriteback. In the async case,
1039 * the retry loop is too short and in the sync-light case,
1040 * the overhead of stalling is too much
1041 */
1042 switch (mode) {
1043 case MIGRATE_SYNC:
1044 case MIGRATE_SYNC_NO_COPY:
1045 break;
1046 default:
1047 rc = -EBUSY;
1048 goto out_unlock;
1049 }
1050 if (!force)
1051 goto out_unlock;
1052 wait_on_page_writeback(page);
1053 }
1054
1055 /*
1056 * By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
1057 * we cannot notice that anon_vma is freed while we migrates a page.
1058 * This get_anon_vma() delays freeing anon_vma pointer until the end
1059 * of migration. File cache pages are no problem because of page_lock()
1060 * File Caches may use write_page() or lock_page() in migration, then,
1061 * just care Anon page here.
1062 *
1063 * Only page_get_anon_vma() understands the subtleties of
1064 * getting a hold on an anon_vma from outside one of its mms.
1065 * But if we cannot get anon_vma, then we won't need it anyway,
1066 * because that implies that the anon page is no longer mapped
1067 * (and cannot be remapped so long as we hold the page lock).
1068 */
1069 if (PageAnon(page) && !PageKsm(page))
1070 anon_vma = page_get_anon_vma(page);
1071
1072 /*
1073 * Block others from accessing the new page when we get around to
1074 * establishing additional references. We are usually the only one
1075 * holding a reference to newpage at this point. We used to have a BUG
1076 * here if trylock_page(newpage) fails, but would like to allow for
1077 * cases where there might be a race with the previous use of newpage.
1078 * This is much like races on refcount of oldpage: just don't BUG().
1079 */
1080 if (unlikely(!trylock_page(newpage)))
1081 goto out_unlock;
1082
1083 if (unlikely(!is_lru)) {
1084 rc = move_to_new_page(newpage, page, mode);
1085 goto out_unlock_both;
1086 }
1087
1088 /*
1089 * Corner case handling:
1090 * 1. When a new swap-cache page is read into, it is added to the LRU
1091 * and treated as swapcache but it has no rmap yet.
1092 * Calling try_to_unmap() against a page->mapping==NULL page will
1093 * trigger a BUG. So handle it here.
1094 * 2. An orphaned page (see truncate_complete_page) might have
1095 * fs-private metadata. The page can be picked up due to memory
1096 * offlining. Everywhere else except page reclaim, the page is
1097 * invisible to the vm, so the page can not be migrated. So try to
1098 * free the metadata, so the page can be freed.
1099 */
1100 if (!page->mapping) {
1101 VM_BUG_ON_PAGE(PageAnon(page), page);
1102 if (page_has_private(page)) {
1103 try_to_free_buffers(page);
1104 goto out_unlock_both;
1105 }
1106 } else if (page_mapped(page)) {
1107 /* Establish migration ptes */
1108 VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma,
1109 page);
1110 try_to_unmap(page,
1111 TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
1112 page_was_mapped = 1;
1113 }
1114
1115 if (!page_mapped(page))
1116 rc = move_to_new_page(newpage, page, mode);
1117
1118 if (page_was_mapped)
1119 remove_migration_ptes(page,
1120 rc == MIGRATEPAGE_SUCCESS ? newpage : page, false);
1121
1122 out_unlock_both:
1123 unlock_page(newpage);
1124 out_unlock:
1125 /* Drop an anon_vma reference if we took one */
1126 if (anon_vma)
1127 put_anon_vma(anon_vma);
1128 unlock_page(page);
1129 out:
1130 /*
1131 * If migration is successful, decrease refcount of the newpage
1132 * which will not free the page because new page owner increased
1133 * refcounter. As well, if it is LRU page, add the page to LRU
1134 * list in here. Use the old state of the isolated source page to
1135 * determine if we migrated a LRU page. newpage was already unlocked
1136 * and possibly modified by its owner - don't rely on the page
1137 * state.
1138 */
1139 if (rc == MIGRATEPAGE_SUCCESS) {
1140 if (unlikely(!is_lru))
1141 put_page(newpage);
1142 else
1143 putback_lru_page(newpage);
1144 }
1145
1146 return rc;
1147 }
1148
1149 /*
1150 * gcc 4.7 and 4.8 on arm get an ICEs when inlining unmap_and_move(). Work
1151 * around it.
1152 */
1153 #if defined(CONFIG_ARM) && \
1154 defined(GCC_VERSION) && GCC_VERSION < 40900 && GCC_VERSION >= 40700
1155 #define ICE_noinline noinline
1156 #else
1157 #define ICE_noinline
1158 #endif
1159
1160 /*
1161 * Obtain the lock on page, remove all ptes and migrate the page
1162 * to the newly allocated page in newpage.
1163 */
1164 static ICE_noinline int unmap_and_move(new_page_t get_new_page,
1165 free_page_t put_new_page,
1166 unsigned long private, struct page *page,
1167 int force, enum migrate_mode mode,
1168 enum migrate_reason reason)
1169 {
1170 int rc = MIGRATEPAGE_SUCCESS;
1171 struct page *newpage;
1172
1173 if (!thp_migration_supported() && PageTransHuge(page))
1174 return -ENOMEM;
1175
1176 newpage = get_new_page(page, private);
1177 if (!newpage)
1178 return -ENOMEM;
1179
1180 if (page_count(page) == 1) {
1181 /* page was freed from under us. So we are done. */
1182 ClearPageActive(page);
1183 ClearPageUnevictable(page);
1184 if (unlikely(__PageMovable(page))) {
1185 lock_page(page);
1186 if (!PageMovable(page))
1187 __ClearPageIsolated(page);
1188 unlock_page(page);
1189 }
1190 if (put_new_page)
1191 put_new_page(newpage, private);
1192 else
1193 put_page(newpage);
1194 goto out;
1195 }
1196
1197 rc = __unmap_and_move(page, newpage, force, mode);
1198 if (rc == MIGRATEPAGE_SUCCESS)
1199 set_page_owner_migrate_reason(newpage, reason);
1200
1201 out:
1202 if (rc != -EAGAIN) {
1203 /*
1204 * A page that has been migrated has all references
1205 * removed and will be freed. A page that has not been
1206 * migrated will have kepts its references and be
1207 * restored.
1208 */
1209 list_del(&page->lru);
1210
1211 /*
1212 * Compaction can migrate also non-LRU pages which are
1213 * not accounted to NR_ISOLATED_*. They can be recognized
1214 * as __PageMovable
1215 */
1216 if (likely(!__PageMovable(page)))
1217 mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
1218 page_is_file_cache(page), -hpage_nr_pages(page));
1219 }
1220
1221 /*
1222 * If migration is successful, releases reference grabbed during
1223 * isolation. Otherwise, restore the page to right list unless
1224 * we want to retry.
1225 */
1226 if (rc == MIGRATEPAGE_SUCCESS) {
1227 put_page(page);
1228 if (reason == MR_MEMORY_FAILURE) {
1229 /*
1230 * Set PG_HWPoison on just freed page
1231 * intentionally. Although it's rather weird,
1232 * it's how HWPoison flag works at the moment.
1233 */
1234 if (set_hwpoison_free_buddy_page(page))
1235 num_poisoned_pages_inc();
1236 }
1237 } else {
1238 if (rc != -EAGAIN) {
1239 if (likely(!__PageMovable(page))) {
1240 putback_lru_page(page);
1241 goto put_new;
1242 }
1243
1244 lock_page(page);
1245 if (PageMovable(page))
1246 putback_movable_page(page);
1247 else
1248 __ClearPageIsolated(page);
1249 unlock_page(page);
1250 put_page(page);
1251 }
1252 put_new:
1253 if (put_new_page)
1254 put_new_page(newpage, private);
1255 else
1256 put_page(newpage);
1257 }
1258
1259 return rc;
1260 }
1261
1262 /*
1263 * Counterpart of unmap_and_move_page() for hugepage migration.
1264 *
1265 * This function doesn't wait the completion of hugepage I/O
1266 * because there is no race between I/O and migration for hugepage.
1267 * Note that currently hugepage I/O occurs only in direct I/O
1268 * where no lock is held and PG_writeback is irrelevant,
1269 * and writeback status of all subpages are counted in the reference
1270 * count of the head page (i.e. if all subpages of a 2MB hugepage are
1271 * under direct I/O, the reference of the head page is 512 and a bit more.)
1272 * This means that when we try to migrate hugepage whose subpages are
1273 * doing direct I/O, some references remain after try_to_unmap() and
1274 * hugepage migration fails without data corruption.
1275 *
1276 * There is also no race when direct I/O is issued on the page under migration,
1277 * because then pte is replaced with migration swap entry and direct I/O code
1278 * will wait in the page fault for migration to complete.
1279 */
1280 static int unmap_and_move_huge_page(new_page_t get_new_page,
1281 free_page_t put_new_page, unsigned long private,
1282 struct page *hpage, int force,
1283 enum migrate_mode mode, int reason)
1284 {
1285 int rc = -EAGAIN;
1286 int page_was_mapped = 0;
1287 struct page *new_hpage;
1288 struct anon_vma *anon_vma = NULL;
1289
1290 /*
1291 * Migratability of hugepages depends on architectures and their size.
1292 * This check is necessary because some callers of hugepage migration
1293 * like soft offline and memory hotremove don't walk through page
1294 * tables or check whether the hugepage is pmd-based or not before
1295 * kicking migration.
1296 */
1297 if (!hugepage_migration_supported(page_hstate(hpage))) {
1298 putback_active_hugepage(hpage);
1299 return -ENOSYS;
1300 }
1301
1302 new_hpage = get_new_page(hpage, private);
1303 if (!new_hpage)
1304 return -ENOMEM;
1305
1306 if (!trylock_page(hpage)) {
1307 if (!force)
1308 goto out;
1309 switch (mode) {
1310 case MIGRATE_SYNC:
1311 case MIGRATE_SYNC_NO_COPY:
1312 break;
1313 default:
1314 goto out;
1315 }
1316 lock_page(hpage);
1317 }
1318
1319 /*
1320 * Check for pages which are in the process of being freed. Without
1321 * page_mapping() set, hugetlbfs specific move page routine will not
1322 * be called and we could leak usage counts for subpools.
1323 */
1324 if (page_private(hpage) && !page_mapping(hpage)) {
1325 rc = -EBUSY;
1326 goto out_unlock;
1327 }
1328
1329 if (PageAnon(hpage))
1330 anon_vma = page_get_anon_vma(hpage);
1331
1332 if (unlikely(!trylock_page(new_hpage)))
1333 goto put_anon;
1334
1335 if (page_mapped(hpage)) {
1336 try_to_unmap(hpage,
1337 TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
1338 page_was_mapped = 1;
1339 }
1340
1341 if (!page_mapped(hpage))
1342 rc = move_to_new_page(new_hpage, hpage, mode);
1343
1344 if (page_was_mapped)
1345 remove_migration_ptes(hpage,
1346 rc == MIGRATEPAGE_SUCCESS ? new_hpage : hpage, false);
1347
1348 unlock_page(new_hpage);
1349
1350 put_anon:
1351 if (anon_vma)
1352 put_anon_vma(anon_vma);
1353
1354 if (rc == MIGRATEPAGE_SUCCESS) {
1355 move_hugetlb_state(hpage, new_hpage, reason);
1356 put_new_page = NULL;
1357 }
1358
1359 out_unlock:
1360 unlock_page(hpage);
1361 out:
1362 if (rc != -EAGAIN)
1363 putback_active_hugepage(hpage);
1364
1365 /*
1366 * If migration was not successful and there's a freeing callback, use
1367 * it. Otherwise, put_page() will drop the reference grabbed during
1368 * isolation.
1369 */
1370 if (put_new_page)
1371 put_new_page(new_hpage, private);
1372 else
1373 putback_active_hugepage(new_hpage);
1374
1375 return rc;
1376 }
1377
1378 /*
1379 * migrate_pages - migrate the pages specified in a list, to the free pages
1380 * supplied as the target for the page migration
1381 *
1382 * @from: The list of pages to be migrated.
1383 * @get_new_page: The function used to allocate free pages to be used
1384 * as the target of the page migration.
1385 * @put_new_page: The function used to free target pages if migration
1386 * fails, or NULL if no special handling is necessary.
1387 * @private: Private data to be passed on to get_new_page()
1388 * @mode: The migration mode that specifies the constraints for
1389 * page migration, if any.
1390 * @reason: The reason for page migration.
1391 *
1392 * The function returns after 10 attempts or if no pages are movable any more
1393 * because the list has become empty or no retryable pages exist any more.
1394 * The caller should call putback_movable_pages() to return pages to the LRU
1395 * or free list only if ret != 0.
1396 *
1397 * Returns the number of pages that were not migrated, or an error code.
1398 */
1399 int migrate_pages(struct list_head *from, new_page_t get_new_page,
1400 free_page_t put_new_page, unsigned long private,
1401 enum migrate_mode mode, int reason)
1402 {
1403 int retry = 1;
1404 int nr_failed = 0;
1405 int nr_succeeded = 0;
1406 int pass = 0;
1407 struct page *page;
1408 struct page *page2;
1409 int swapwrite = current->flags & PF_SWAPWRITE;
1410 int rc;
1411
1412 if (!swapwrite)
1413 current->flags |= PF_SWAPWRITE;
1414
1415 for(pass = 0; pass < 10 && retry; pass++) {
1416 retry = 0;
1417
1418 list_for_each_entry_safe(page, page2, from, lru) {
1419 retry:
1420 cond_resched();
1421
1422 if (PageHuge(page))
1423 rc = unmap_and_move_huge_page(get_new_page,
1424 put_new_page, private, page,
1425 pass > 2, mode, reason);
1426 else
1427 rc = unmap_and_move(get_new_page, put_new_page,
1428 private, page, pass > 2, mode,
1429 reason);
1430
1431 switch(rc) {
1432 case -ENOMEM:
1433 /*
1434 * THP migration might be unsupported or the
1435 * allocation could've failed so we should
1436 * retry on the same page with the THP split
1437 * to base pages.
1438 *
1439 * Head page is retried immediately and tail
1440 * pages are added to the tail of the list so
1441 * we encounter them after the rest of the list
1442 * is processed.
1443 */
1444 if (PageTransHuge(page) && !PageHuge(page)) {
1445 lock_page(page);
1446 rc = split_huge_page_to_list(page, from);
1447 unlock_page(page);
1448 if (!rc) {
1449 list_safe_reset_next(page, page2, lru);
1450 goto retry;
1451 }
1452 }
1453 nr_failed++;
1454 goto out;
1455 case -EAGAIN:
1456 retry++;
1457 break;
1458 case MIGRATEPAGE_SUCCESS:
1459 nr_succeeded++;
1460 break;
1461 default:
1462 /*
1463 * Permanent failure (-EBUSY, -ENOSYS, etc.):
1464 * unlike -EAGAIN case, the failed page is
1465 * removed from migration page list and not
1466 * retried in the next outer loop.
1467 */
1468 nr_failed++;
1469 break;
1470 }
1471 }
1472 }
1473 nr_failed += retry;
1474 rc = nr_failed;
1475 out:
1476 if (nr_succeeded)
1477 count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
1478 if (nr_failed)
1479 count_vm_events(PGMIGRATE_FAIL, nr_failed);
1480 trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason);
1481
1482 if (!swapwrite)
1483 current->flags &= ~PF_SWAPWRITE;
1484
1485 return rc;
1486 }
1487
1488 #ifdef CONFIG_NUMA
1489
1490 static int store_status(int __user *status, int start, int value, int nr)
1491 {
1492 while (nr-- > 0) {
1493 if (put_user(value, status + start))
1494 return -EFAULT;
1495 start++;
1496 }
1497
1498 return 0;
1499 }
1500
1501 static int do_move_pages_to_node(struct mm_struct *mm,
1502 struct list_head *pagelist, int node)
1503 {
1504 int err;
1505
1506 if (list_empty(pagelist))
1507 return 0;
1508
1509 err = migrate_pages(pagelist, alloc_new_node_page, NULL, node,
1510 MIGRATE_SYNC, MR_SYSCALL);
1511 if (err)
1512 putback_movable_pages(pagelist);
1513 return err;
1514 }
1515
1516 /*
1517 * Resolves the given address to a struct page, isolates it from the LRU and
1518 * puts it to the given pagelist.
1519 * Returns:
1520 * errno - if the page cannot be found/isolated
1521 * 0 - when it doesn't have to be migrated because it is already on the
1522 * target node
1523 * 1 - when it has been queued
1524 */
1525 static int add_page_for_migration(struct mm_struct *mm, unsigned long addr,
1526 int node, struct list_head *pagelist, bool migrate_all)
1527 {
1528 struct vm_area_struct *vma;
1529 struct page *page;
1530 unsigned int follflags;
1531 int err;
1532
1533 down_read(&mm->mmap_sem);
1534 err = -EFAULT;
1535 vma = find_vma(mm, addr);
1536 if (!vma || addr < vma->vm_start || !vma_migratable(vma))
1537 goto out;
1538
1539 /* FOLL_DUMP to ignore special (like zero) pages */
1540 follflags = FOLL_GET | FOLL_DUMP;
1541 page = follow_page(vma, addr, follflags);
1542
1543 err = PTR_ERR(page);
1544 if (IS_ERR(page))
1545 goto out;
1546
1547 err = -ENOENT;
1548 if (!page)
1549 goto out;
1550
1551 err = 0;
1552 if (page_to_nid(page) == node)
1553 goto out_putpage;
1554
1555 err = -EACCES;
1556 if (page_mapcount(page) > 1 && !migrate_all)
1557 goto out_putpage;
1558
1559 if (PageHuge(page)) {
1560 if (PageHead(page)) {
1561 isolate_huge_page(page, pagelist);
1562 err = 1;
1563 }
1564 } else {
1565 struct page *head;
1566
1567 head = compound_head(page);
1568 err = isolate_lru_page(head);
1569 if (err)
1570 goto out_putpage;
1571
1572 err = 1;
1573 list_add_tail(&head->lru, pagelist);
1574 mod_node_page_state(page_pgdat(head),
1575 NR_ISOLATED_ANON + page_is_file_cache(head),
1576 hpage_nr_pages(head));
1577 }
1578 out_putpage:
1579 /*
1580 * Either remove the duplicate refcount from
1581 * isolate_lru_page() or drop the page ref if it was
1582 * not isolated.
1583 */
1584 put_page(page);
1585 out:
1586 up_read(&mm->mmap_sem);
1587 return err;
1588 }
1589
1590 /*
1591 * Migrate an array of page address onto an array of nodes and fill
1592 * the corresponding array of status.
1593 */
1594 static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
1595 unsigned long nr_pages,
1596 const void __user * __user *pages,
1597 const int __user *nodes,
1598 int __user *status, int flags)
1599 {
1600 int current_node = NUMA_NO_NODE;
1601 LIST_HEAD(pagelist);
1602 int start, i;
1603 int err = 0, err1;
1604
1605 migrate_prep();
1606
1607 for (i = start = 0; i < nr_pages; i++) {
1608 const void __user *p;
1609 unsigned long addr;
1610 int node;
1611
1612 err = -EFAULT;
1613 if (get_user(p, pages + i))
1614 goto out_flush;
1615 if (get_user(node, nodes + i))
1616 goto out_flush;
1617 addr = (unsigned long)untagged_addr(p);
1618
1619 err = -ENODEV;
1620 if (node < 0 || node >= MAX_NUMNODES)
1621 goto out_flush;
1622 if (!node_state(node, N_MEMORY))
1623 goto out_flush;
1624
1625 err = -EACCES;
1626 if (!node_isset(node, task_nodes))
1627 goto out_flush;
1628
1629 if (current_node == NUMA_NO_NODE) {
1630 current_node = node;
1631 start = i;
1632 } else if (node != current_node) {
1633 err = do_move_pages_to_node(mm, &pagelist, current_node);
1634 if (err) {
1635 /*
1636 * Positive err means the number of failed
1637 * pages to migrate. Since we are going to
1638 * abort and return the number of non-migrated
1639 * pages, so need to incude the rest of the
1640 * nr_pages that have not been attempted as
1641 * well.
1642 */
1643 if (err > 0)
1644 err += nr_pages - i - 1;
1645 goto out;
1646 }
1647 err = store_status(status, start, current_node, i - start);
1648 if (err)
1649 goto out;
1650 start = i;
1651 current_node = node;
1652 }
1653
1654 /*
1655 * Errors in the page lookup or isolation are not fatal and we simply
1656 * report them via status
1657 */
1658 err = add_page_for_migration(mm, addr, current_node,
1659 &pagelist, flags & MPOL_MF_MOVE_ALL);
1660
1661 if (!err) {
1662 /* The page is already on the target node */
1663 err = store_status(status, i, current_node, 1);
1664 if (err)
1665 goto out_flush;
1666 continue;
1667 } else if (err > 0) {
1668 /* The page is successfully queued for migration */
1669 continue;
1670 }
1671
1672 err = store_status(status, i, err, 1);
1673 if (err)
1674 goto out_flush;
1675
1676 err = do_move_pages_to_node(mm, &pagelist, current_node);
1677 if (err) {
1678 if (err > 0)
1679 err += nr_pages - i - 1;
1680 goto out;
1681 }
1682 if (i > start) {
1683 err = store_status(status, start, current_node, i - start);
1684 if (err)
1685 goto out;
1686 }
1687 current_node = NUMA_NO_NODE;
1688 }
1689 out_flush:
1690 if (list_empty(&pagelist))
1691 return err;
1692
1693 /* Make sure we do not overwrite the existing error */
1694 err1 = do_move_pages_to_node(mm, &pagelist, current_node);
1695 /*
1696 * Don't have to report non-attempted pages here since:
1697 * - If the above loop is done gracefully all pages have been
1698 * attempted.
1699 * - If the above loop is aborted it means a fatal error
1700 * happened, should return ret.
1701 */
1702 if (!err1)
1703 err1 = store_status(status, start, current_node, i - start);
1704 if (err >= 0)
1705 err = err1;
1706 out:
1707 return err;
1708 }
1709
1710 /*
1711 * Determine the nodes of an array of pages and store it in an array of status.
1712 */
1713 static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
1714 const void __user **pages, int *status)
1715 {
1716 unsigned long i;
1717
1718 down_read(&mm->mmap_sem);
1719
1720 for (i = 0; i < nr_pages; i++) {
1721 unsigned long addr = (unsigned long)(*pages);
1722 struct vm_area_struct *vma;
1723 struct page *page;
1724 int err = -EFAULT;
1725
1726 vma = find_vma(mm, addr);
1727 if (!vma || addr < vma->vm_start)
1728 goto set_status;
1729
1730 /* FOLL_DUMP to ignore special (like zero) pages */
1731 page = follow_page(vma, addr, FOLL_DUMP);
1732
1733 err = PTR_ERR(page);
1734 if (IS_ERR(page))
1735 goto set_status;
1736
1737 err = page ? page_to_nid(page) : -ENOENT;
1738 set_status:
1739 *status = err;
1740
1741 pages++;
1742 status++;
1743 }
1744
1745 up_read(&mm->mmap_sem);
1746 }
1747
1748 /*
1749 * Determine the nodes of a user array of pages and store it in
1750 * a user array of status.
1751 */
1752 static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
1753 const void __user * __user *pages,
1754 int __user *status)
1755 {
1756 #define DO_PAGES_STAT_CHUNK_NR 16
1757 const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
1758 int chunk_status[DO_PAGES_STAT_CHUNK_NR];
1759
1760 while (nr_pages) {
1761 unsigned long chunk_nr;
1762
1763 chunk_nr = nr_pages;
1764 if (chunk_nr > DO_PAGES_STAT_CHUNK_NR)
1765 chunk_nr = DO_PAGES_STAT_CHUNK_NR;
1766
1767 if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages)))
1768 break;
1769
1770 do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
1771
1772 if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
1773 break;
1774
1775 pages += chunk_nr;
1776 status += chunk_nr;
1777 nr_pages -= chunk_nr;
1778 }
1779 return nr_pages ? -EFAULT : 0;
1780 }
1781
1782 /*
1783 * Move a list of pages in the address space of the currently executing
1784 * process.
1785 */
1786 static int kernel_move_pages(pid_t pid, unsigned long nr_pages,
1787 const void __user * __user *pages,
1788 const int __user *nodes,
1789 int __user *status, int flags)
1790 {
1791 struct task_struct *task;
1792 struct mm_struct *mm;
1793 int err;
1794 nodemask_t task_nodes;
1795
1796 /* Check flags */
1797 if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
1798 return -EINVAL;
1799
1800 if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
1801 return -EPERM;
1802
1803 /* Find the mm_struct */
1804 rcu_read_lock();
1805 task = pid ? find_task_by_vpid(pid) : current;
1806 if (!task) {
1807 rcu_read_unlock();
1808 return -ESRCH;
1809 }
1810 get_task_struct(task);
1811
1812 /*
1813 * Check if this process has the right to modify the specified
1814 * process. Use the regular "ptrace_may_access()" checks.
1815 */
1816 if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
1817 rcu_read_unlock();
1818 err = -EPERM;
1819 goto out;
1820 }
1821 rcu_read_unlock();
1822
1823 err = security_task_movememory(task);
1824 if (err)
1825 goto out;
1826
1827 task_nodes = cpuset_mems_allowed(task);
1828 mm = get_task_mm(task);
1829 put_task_struct(task);
1830
1831 if (!mm)
1832 return -EINVAL;
1833
1834 if (nodes)
1835 err = do_pages_move(mm, task_nodes, nr_pages, pages,
1836 nodes, status, flags);
1837 else
1838 err = do_pages_stat(mm, nr_pages, pages, status);
1839
1840 mmput(mm);
1841 return err;
1842
1843 out:
1844 put_task_struct(task);
1845 return err;
1846 }
1847
1848 SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
1849 const void __user * __user *, pages,
1850 const int __user *, nodes,
1851 int __user *, status, int, flags)
1852 {
1853 return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags);
1854 }
1855
1856 #ifdef CONFIG_COMPAT
1857 COMPAT_SYSCALL_DEFINE6(move_pages, pid_t, pid, compat_ulong_t, nr_pages,
1858 compat_uptr_t __user *, pages32,
1859 const int __user *, nodes,
1860 int __user *, status,
1861 int, flags)
1862 {
1863 const void __user * __user *pages;
1864 int i;
1865
1866 pages = compat_alloc_user_space(nr_pages * sizeof(void *));
1867 for (i = 0; i < nr_pages; i++) {
1868 compat_uptr_t p;
1869
1870 if (get_user(p, pages32 + i) ||
1871 put_user(compat_ptr(p), pages + i))
1872 return -EFAULT;
1873 }
1874 return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags);
1875 }
1876 #endif /* CONFIG_COMPAT */
1877
1878 #ifdef CONFIG_NUMA_BALANCING
1879 /*
1880 * Returns true if this is a safe migration target node for misplaced NUMA
1881 * pages. Currently it only checks the watermarks which crude
1882 */
1883 static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
1884 unsigned long nr_migrate_pages)
1885 {
1886 int z;
1887
1888 for (z = pgdat->nr_zones - 1; z >= 0; z--) {
1889 struct zone *zone = pgdat->node_zones + z;
1890
1891 if (!populated_zone(zone))
1892 continue;
1893
1894 /* Avoid waking kswapd by allocating pages_to_migrate pages. */
1895 if (!zone_watermark_ok(zone, 0,
1896 high_wmark_pages(zone) +
1897 nr_migrate_pages,
1898 0, 0))
1899 continue;
1900 return true;
1901 }
1902 return false;
1903 }
1904
1905 static struct page *alloc_misplaced_dst_page(struct page *page,
1906 unsigned long data)
1907 {
1908 int nid = (int) data;
1909 struct page *newpage;
1910
1911 newpage = __alloc_pages_node(nid,
1912 (GFP_HIGHUSER_MOVABLE |
1913 __GFP_THISNODE | __GFP_NOMEMALLOC |
1914 __GFP_NORETRY | __GFP_NOWARN) &
1915 ~__GFP_RECLAIM, 0);
1916
1917 return newpage;
1918 }
1919
1920 static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
1921 {
1922 int page_lru;
1923
1924 VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page);
1925
1926 /* Avoid migrating to a node that is nearly full */
1927 if (!migrate_balanced_pgdat(pgdat, compound_nr(page)))
1928 return 0;
1929
1930 if (isolate_lru_page(page))
1931 return 0;
1932
1933 /*
1934 * migrate_misplaced_transhuge_page() skips page migration's usual
1935 * check on page_count(), so we must do it here, now that the page
1936 * has been isolated: a GUP pin, or any other pin, prevents migration.
1937 * The expected page count is 3: 1 for page's mapcount and 1 for the
1938 * caller's pin and 1 for the reference taken by isolate_lru_page().
1939 */
1940 if (PageTransHuge(page) && page_count(page) != 3) {
1941 putback_lru_page(page);
1942 return 0;
1943 }
1944
1945 page_lru = page_is_file_cache(page);
1946 mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_lru,
1947 hpage_nr_pages(page));
1948
1949 /*
1950 * Isolating the page has taken another reference, so the
1951 * caller's reference can be safely dropped without the page
1952 * disappearing underneath us during migration.
1953 */
1954 put_page(page);
1955 return 1;
1956 }
1957
1958 bool pmd_trans_migrating(pmd_t pmd)
1959 {
1960 struct page *page = pmd_page(pmd);
1961 return PageLocked(page);
1962 }
1963
1964 /*
1965 * Attempt to migrate a misplaced page to the specified destination
1966 * node. Caller is expected to have an elevated reference count on
1967 * the page that will be dropped by this function before returning.
1968 */
1969 int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
1970 int node)
1971 {
1972 pg_data_t *pgdat = NODE_DATA(node);
1973 int isolated;
1974 int nr_remaining;
1975 LIST_HEAD(migratepages);
1976
1977 /*
1978 * Don't migrate file pages that are mapped in multiple processes
1979 * with execute permissions as they are probably shared libraries.
1980 */
1981 if (page_mapcount(page) != 1 && page_is_file_cache(page) &&
1982 (vma->vm_flags & VM_EXEC))
1983 goto out;
1984
1985 /*
1986 * Also do not migrate dirty pages as not all filesystems can move
1987 * dirty pages in MIGRATE_ASYNC mode which is a waste of cycles.
1988 */
1989 if (page_is_file_cache(page) && PageDirty(page))
1990 goto out;
1991
1992 isolated = numamigrate_isolate_page(pgdat, page);
1993 if (!isolated)
1994 goto out;
1995
1996 list_add(&page->lru, &migratepages);
1997 nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page,
1998 NULL, node, MIGRATE_ASYNC,
1999 MR_NUMA_MISPLACED);
2000 if (nr_remaining) {
2001 if (!list_empty(&migratepages)) {
2002 list_del(&page->lru);
2003 dec_node_page_state(page, NR_ISOLATED_ANON +
2004 page_is_file_cache(page));
2005 putback_lru_page(page);
2006 }
2007 isolated = 0;
2008 } else
2009 count_vm_numa_event(NUMA_PAGE_MIGRATE);
2010 BUG_ON(!list_empty(&migratepages));
2011 return isolated;
2012
2013 out:
2014 put_page(page);
2015 return 0;
2016 }
2017 #endif /* CONFIG_NUMA_BALANCING */
2018
2019 #if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
2020 /*
2021 * Migrates a THP to a given target node. page must be locked and is unlocked
2022 * before returning.
2023 */
2024 int migrate_misplaced_transhuge_page(struct mm_struct *mm,
2025 struct vm_area_struct *vma,
2026 pmd_t *pmd, pmd_t entry,
2027 unsigned long address,
2028 struct page *page, int node)
2029 {
2030 spinlock_t *ptl;
2031 pg_data_t *pgdat = NODE_DATA(node);
2032 int isolated = 0;
2033 struct page *new_page = NULL;
2034 int page_lru = page_is_file_cache(page);
2035 unsigned long start = address & HPAGE_PMD_MASK;
2036
2037 new_page = alloc_pages_node(node,
2038 (GFP_TRANSHUGE_LIGHT | __GFP_THISNODE),
2039 HPAGE_PMD_ORDER);
2040 if (!new_page)
2041 goto out_fail;
2042 prep_transhuge_page(new_page);
2043
2044 isolated = numamigrate_isolate_page(pgdat, page);
2045 if (!isolated) {
2046 put_page(new_page);
2047 goto out_fail;
2048 }
2049
2050 /* Prepare a page as a migration target */
2051 __SetPageLocked(new_page);
2052 if (PageSwapBacked(page))
2053 __SetPageSwapBacked(new_page);
2054
2055 /* anon mapping, we can simply copy page->mapping to the new page: */
2056 new_page->mapping = page->mapping;
2057 new_page->index = page->index;
2058 /* flush the cache before copying using the kernel virtual address */
2059 flush_cache_range(vma, start, start + HPAGE_PMD_SIZE);
2060 migrate_page_copy(new_page, page);
2061 WARN_ON(PageLRU(new_page));
2062
2063 /* Recheck the target PMD */
2064 ptl = pmd_lock(mm, pmd);
2065 if (unlikely(!pmd_same(*pmd, entry) || !page_ref_freeze(page, 2))) {
2066 spin_unlock(ptl);
2067
2068 /* Reverse changes made by migrate_page_copy() */
2069 if (TestClearPageActive(new_page))
2070 SetPageActive(page);
2071 if (TestClearPageUnevictable(new_page))
2072 SetPageUnevictable(page);
2073
2074 unlock_page(new_page);
2075 put_page(new_page); /* Free it */
2076
2077 /* Retake the callers reference and putback on LRU */
2078 get_page(page);
2079 putback_lru_page(page);
2080 mod_node_page_state(page_pgdat(page),
2081 NR_ISOLATED_ANON + page_lru, -HPAGE_PMD_NR);
2082
2083 goto out_unlock;
2084 }
2085
2086 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
2087 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
2088
2089 /*
2090 * Overwrite the old entry under pagetable lock and establish
2091 * the new PTE. Any parallel GUP will either observe the old
2092 * page blocking on the page lock, block on the page table
2093 * lock or observe the new page. The SetPageUptodate on the
2094 * new page and page_add_new_anon_rmap guarantee the copy is
2095 * visible before the pagetable update.
2096 */
2097 page_add_anon_rmap(new_page, vma, start, true);
2098 /*
2099 * At this point the pmd is numa/protnone (i.e. non present) and the TLB
2100 * has already been flushed globally. So no TLB can be currently
2101 * caching this non present pmd mapping. There's no need to clear the
2102 * pmd before doing set_pmd_at(), nor to flush the TLB after
2103 * set_pmd_at(). Clearing the pmd here would introduce a race
2104 * condition against MADV_DONTNEED, because MADV_DONTNEED only holds the
2105 * mmap_sem for reading. If the pmd is set to NULL at any given time,
2106 * MADV_DONTNEED won't wait on the pmd lock and it'll skip clearing this
2107 * pmd.
2108 */
2109 set_pmd_at(mm, start, pmd, entry);
2110 update_mmu_cache_pmd(vma, address, &entry);
2111
2112 page_ref_unfreeze(page, 2);
2113 mlock_migrate_page(new_page, page);
2114 page_remove_rmap(page, true);
2115 set_page_owner_migrate_reason(new_page, MR_NUMA_MISPLACED);
2116
2117 spin_unlock(ptl);
2118
2119 /* Take an "isolate" reference and put new page on the LRU. */
2120 get_page(new_page);
2121 putback_lru_page(new_page);
2122
2123 unlock_page(new_page);
2124 unlock_page(page);
2125 put_page(page); /* Drop the rmap reference */
2126 put_page(page); /* Drop the LRU isolation reference */
2127
2128 count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR);
2129 count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR);
2130
2131 mod_node_page_state(page_pgdat(page),
2132 NR_ISOLATED_ANON + page_lru,
2133 -HPAGE_PMD_NR);
2134 return isolated;
2135
2136 out_fail:
2137 count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
2138 ptl = pmd_lock(mm, pmd);
2139 if (pmd_same(*pmd, entry)) {
2140 entry = pmd_modify(entry, vma->vm_page_prot);
2141 set_pmd_at(mm, start, pmd, entry);
2142 update_mmu_cache_pmd(vma, address, &entry);
2143 }
2144 spin_unlock(ptl);
2145
2146 out_unlock:
2147 unlock_page(page);
2148 put_page(page);
2149 return 0;
2150 }
2151 #endif /* CONFIG_NUMA_BALANCING */
2152
2153 #endif /* CONFIG_NUMA */
2154
2155 #ifdef CONFIG_DEVICE_PRIVATE
2156 static int migrate_vma_collect_hole(unsigned long start,
2157 unsigned long end,
2158 struct mm_walk *walk)
2159 {
2160 struct migrate_vma *migrate = walk->private;
2161 unsigned long addr;
2162
2163 for (addr = start & PAGE_MASK; addr < end; addr += PAGE_SIZE) {
2164 migrate->src[migrate->npages] = MIGRATE_PFN_MIGRATE;
2165 migrate->dst[migrate->npages] = 0;
2166 migrate->npages++;
2167 migrate->cpages++;
2168 }
2169
2170 return 0;
2171 }
2172
2173 static int migrate_vma_collect_skip(unsigned long start,
2174 unsigned long end,
2175 struct mm_walk *walk)
2176 {
2177 struct migrate_vma *migrate = walk->private;
2178 unsigned long addr;
2179
2180 for (addr = start & PAGE_MASK; addr < end; addr += PAGE_SIZE) {
2181 migrate->dst[migrate->npages] = 0;
2182 migrate->src[migrate->npages++] = 0;
2183 }
2184
2185 return 0;
2186 }
2187
2188 static int migrate_vma_collect_pmd(pmd_t *pmdp,
2189 unsigned long start,
2190 unsigned long end,
2191 struct mm_walk *walk)
2192 {
2193 struct migrate_vma *migrate = walk->private;
2194 struct vm_area_struct *vma = walk->vma;
2195 struct mm_struct *mm = vma->vm_mm;
2196 unsigned long addr = start, unmapped = 0;
2197 spinlock_t *ptl;
2198 pte_t *ptep;
2199
2200 again:
2201 if (pmd_none(*pmdp))
2202 return migrate_vma_collect_hole(start, end, walk);
2203
2204 if (pmd_trans_huge(*pmdp)) {
2205 struct page *page;
2206
2207 ptl = pmd_lock(mm, pmdp);
2208 if (unlikely(!pmd_trans_huge(*pmdp))) {
2209 spin_unlock(ptl);
2210 goto again;
2211 }
2212
2213 page = pmd_page(*pmdp);
2214 if (is_huge_zero_page(page)) {
2215 spin_unlock(ptl);
2216 split_huge_pmd(vma, pmdp, addr);
2217 if (pmd_trans_unstable(pmdp))
2218 return migrate_vma_collect_skip(start, end,
2219 walk);
2220 } else {
2221 int ret;
2222
2223 get_page(page);
2224 spin_unlock(ptl);
2225 if (unlikely(!trylock_page(page)))
2226 return migrate_vma_collect_skip(start, end,
2227 walk);
2228 ret = split_huge_page(page);
2229 unlock_page(page);
2230 put_page(page);
2231 if (ret)
2232 return migrate_vma_collect_skip(start, end,
2233 walk);
2234 if (pmd_none(*pmdp))
2235 return migrate_vma_collect_hole(start, end,
2236 walk);
2237 }
2238 }
2239
2240 if (unlikely(pmd_bad(*pmdp)))
2241 return migrate_vma_collect_skip(start, end, walk);
2242
2243 ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
2244 arch_enter_lazy_mmu_mode();
2245
2246 for (; addr < end; addr += PAGE_SIZE, ptep++) {
2247 unsigned long mpfn, pfn;
2248 struct page *page;
2249 swp_entry_t entry;
2250 pte_t pte;
2251
2252 pte = *ptep;
2253
2254 if (pte_none(pte)) {
2255 mpfn = MIGRATE_PFN_MIGRATE;
2256 migrate->cpages++;
2257 goto next;
2258 }
2259
2260 if (!pte_present(pte)) {
2261 mpfn = 0;
2262
2263 /*
2264 * Only care about unaddressable device page special
2265 * page table entry. Other special swap entries are not
2266 * migratable, and we ignore regular swapped page.
2267 */
2268 entry = pte_to_swp_entry(pte);
2269 if (!is_device_private_entry(entry))
2270 goto next;
2271
2272 page = device_private_entry_to_page(entry);
2273 mpfn = migrate_pfn(page_to_pfn(page)) |
2274 MIGRATE_PFN_MIGRATE;
2275 if (is_write_device_private_entry(entry))
2276 mpfn |= MIGRATE_PFN_WRITE;
2277 } else {
2278 pfn = pte_pfn(pte);
2279 if (is_zero_pfn(pfn)) {
2280 mpfn = MIGRATE_PFN_MIGRATE;
2281 migrate->cpages++;
2282 goto next;
2283 }
2284 page = vm_normal_page(migrate->vma, addr, pte);
2285 mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
2286 mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
2287 }
2288
2289 /* FIXME support THP */
2290 if (!page || !page->mapping || PageTransCompound(page)) {
2291 mpfn = 0;
2292 goto next;
2293 }
2294
2295 /*
2296 * By getting a reference on the page we pin it and that blocks
2297 * any kind of migration. Side effect is that it "freezes" the
2298 * pte.
2299 *
2300 * We drop this reference after isolating the page from the lru
2301 * for non device page (device page are not on the lru and thus
2302 * can't be dropped from it).
2303 */
2304 get_page(page);
2305 migrate->cpages++;
2306
2307 /*
2308 * Optimize for the common case where page is only mapped once
2309 * in one process. If we can lock the page, then we can safely
2310 * set up a special migration page table entry now.
2311 */
2312 if (trylock_page(page)) {
2313 pte_t swp_pte;
2314
2315 mpfn |= MIGRATE_PFN_LOCKED;
2316 ptep_get_and_clear(mm, addr, ptep);
2317
2318 /* Setup special migration page table entry */
2319 entry = make_migration_entry(page, mpfn &
2320 MIGRATE_PFN_WRITE);
2321 swp_pte = swp_entry_to_pte(entry);
2322 if (pte_soft_dirty(pte))
2323 swp_pte = pte_swp_mksoft_dirty(swp_pte);
2324 set_pte_at(mm, addr, ptep, swp_pte);
2325
2326 /*
2327 * This is like regular unmap: we remove the rmap and
2328 * drop page refcount. Page won't be freed, as we took
2329 * a reference just above.
2330 */
2331 page_remove_rmap(page, false);
2332 put_page(page);
2333
2334 if (pte_present(pte))
2335 unmapped++;
2336 }
2337
2338 next:
2339 migrate->dst[migrate->npages] = 0;
2340 migrate->src[migrate->npages++] = mpfn;
2341 }
2342 arch_leave_lazy_mmu_mode();
2343 pte_unmap_unlock(ptep - 1, ptl);
2344
2345 /* Only flush the TLB if we actually modified any entries */
2346 if (unmapped)
2347 flush_tlb_range(walk->vma, start, end);
2348
2349 return 0;
2350 }
2351
2352 static const struct mm_walk_ops migrate_vma_walk_ops = {
2353 .pmd_entry = migrate_vma_collect_pmd,
2354 .pte_hole = migrate_vma_collect_hole,
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 */
2365 static void migrate_vma_collect(struct migrate_vma *migrate)
2366 {
2367 struct mmu_notifier_range range;
2368
2369 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL,
2370 migrate->vma->vm_mm, migrate->start, migrate->end);
2371 mmu_notifier_invalidate_range_start(&range);
2372
2373 walk_page_range(migrate->vma->vm_mm, migrate->start, migrate->end,
2374 &migrate_vma_walk_ops, migrate);
2375
2376 mmu_notifier_invalidate_range_end(&range);
2377 migrate->end = migrate->start + (migrate->npages << PAGE_SHIFT);
2378 }
2379
2380 /*
2381 * migrate_vma_check_page() - check if page is pinned or not
2382 * @page: struct page to check
2383 *
2384 * Pinned pages cannot be migrated. This is the same test as in
2385 * migrate_page_move_mapping(), except that here we allow migration of a
2386 * ZONE_DEVICE page.
2387 */
2388 static bool migrate_vma_check_page(struct page *page)
2389 {
2390 /*
2391 * One extra ref because caller holds an extra reference, either from
2392 * isolate_lru_page() for a regular page, or migrate_vma_collect() for
2393 * a device page.
2394 */
2395 int extra = 1;
2396
2397 /*
2398 * FIXME support THP (transparent huge page), it is bit more complex to
2399 * check them than regular pages, because they can be mapped with a pmd
2400 * or with a pte (split pte mapping).
2401 */
2402 if (PageCompound(page))
2403 return false;
2404
2405 /* Page from ZONE_DEVICE have one extra reference */
2406 if (is_zone_device_page(page)) {
2407 /*
2408 * Private page can never be pin as they have no valid pte and
2409 * GUP will fail for those. Yet if there is a pending migration
2410 * a thread might try to wait on the pte migration entry and
2411 * will bump the page reference count. Sadly there is no way to
2412 * differentiate a regular pin from migration wait. Hence to
2413 * avoid 2 racing thread trying to migrate back to CPU to enter
2414 * infinite loop (one stoping migration because the other is
2415 * waiting on pte migration entry). We always return true here.
2416 *
2417 * FIXME proper solution is to rework migration_entry_wait() so
2418 * it does not need to take a reference on page.
2419 */
2420 return is_device_private_page(page);
2421 }
2422
2423 /* For file back page */
2424 if (page_mapping(page))
2425 extra += 1 + page_has_private(page);
2426
2427 if ((page_count(page) - extra) > page_mapcount(page))
2428 return false;
2429
2430 return true;
2431 }
2432
2433 /*
2434 * migrate_vma_prepare() - lock pages and isolate them from the lru
2435 * @migrate: migrate struct containing all migration information
2436 *
2437 * This locks pages that have been collected by migrate_vma_collect(). Once each
2438 * page is locked it is isolated from the lru (for non-device pages). Finally,
2439 * the ref taken by migrate_vma_collect() is dropped, as locked pages cannot be
2440 * migrated by concurrent kernel threads.
2441 */
2442 static void migrate_vma_prepare(struct migrate_vma *migrate)
2443 {
2444 const unsigned long npages = migrate->npages;
2445 const unsigned long start = migrate->start;
2446 unsigned long addr, i, restore = 0;
2447 bool allow_drain = true;
2448
2449 lru_add_drain();
2450
2451 for (i = 0; (i < npages) && migrate->cpages; i++) {
2452 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2453 bool remap = true;
2454
2455 if (!page)
2456 continue;
2457
2458 if (!(migrate->src[i] & MIGRATE_PFN_LOCKED)) {
2459 /*
2460 * Because we are migrating several pages there can be
2461 * a deadlock between 2 concurrent migration where each
2462 * are waiting on each other page lock.
2463 *
2464 * Make migrate_vma() a best effort thing and backoff
2465 * for any page we can not lock right away.
2466 */
2467 if (!trylock_page(page)) {
2468 migrate->src[i] = 0;
2469 migrate->cpages--;
2470 put_page(page);
2471 continue;
2472 }
2473 remap = false;
2474 migrate->src[i] |= MIGRATE_PFN_LOCKED;
2475 }
2476
2477 /* ZONE_DEVICE pages are not on LRU */
2478 if (!is_zone_device_page(page)) {
2479 if (!PageLRU(page) && allow_drain) {
2480 /* Drain CPU's pagevec */
2481 lru_add_drain_all();
2482 allow_drain = false;
2483 }
2484
2485 if (isolate_lru_page(page)) {
2486 if (remap) {
2487 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2488 migrate->cpages--;
2489 restore++;
2490 } else {
2491 migrate->src[i] = 0;
2492 unlock_page(page);
2493 migrate->cpages--;
2494 put_page(page);
2495 }
2496 continue;
2497 }
2498
2499 /* Drop the reference we took in collect */
2500 put_page(page);
2501 }
2502
2503 if (!migrate_vma_check_page(page)) {
2504 if (remap) {
2505 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2506 migrate->cpages--;
2507 restore++;
2508
2509 if (!is_zone_device_page(page)) {
2510 get_page(page);
2511 putback_lru_page(page);
2512 }
2513 } else {
2514 migrate->src[i] = 0;
2515 unlock_page(page);
2516 migrate->cpages--;
2517
2518 if (!is_zone_device_page(page))
2519 putback_lru_page(page);
2520 else
2521 put_page(page);
2522 }
2523 }
2524 }
2525
2526 for (i = 0, addr = start; i < npages && restore; i++, addr += PAGE_SIZE) {
2527 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2528
2529 if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE))
2530 continue;
2531
2532 remove_migration_pte(page, migrate->vma, addr, page);
2533
2534 migrate->src[i] = 0;
2535 unlock_page(page);
2536 put_page(page);
2537 restore--;
2538 }
2539 }
2540
2541 /*
2542 * migrate_vma_unmap() - replace page mapping with special migration pte entry
2543 * @migrate: migrate struct containing all migration information
2544 *
2545 * Replace page mapping (CPU page table pte) with a special migration pte entry
2546 * and check again if it has been pinned. Pinned pages are restored because we
2547 * cannot migrate them.
2548 *
2549 * This is the last step before we call the device driver callback to allocate
2550 * destination memory and copy contents of original page over to new page.
2551 */
2552 static void migrate_vma_unmap(struct migrate_vma *migrate)
2553 {
2554 int flags = TTU_MIGRATION | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
2555 const unsigned long npages = migrate->npages;
2556 const unsigned long start = migrate->start;
2557 unsigned long addr, i, restore = 0;
2558
2559 for (i = 0; i < npages; i++) {
2560 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2561
2562 if (!page || !(migrate->src[i] & MIGRATE_PFN_MIGRATE))
2563 continue;
2564
2565 if (page_mapped(page)) {
2566 try_to_unmap(page, flags);
2567 if (page_mapped(page))
2568 goto restore;
2569 }
2570
2571 if (migrate_vma_check_page(page))
2572 continue;
2573
2574 restore:
2575 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2576 migrate->cpages--;
2577 restore++;
2578 }
2579
2580 for (addr = start, i = 0; i < npages && restore; addr += PAGE_SIZE, i++) {
2581 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2582
2583 if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE))
2584 continue;
2585
2586 remove_migration_ptes(page, page, false);
2587
2588 migrate->src[i] = 0;
2589 unlock_page(page);
2590 restore--;
2591
2592 if (is_zone_device_page(page))
2593 put_page(page);
2594 else
2595 putback_lru_page(page);
2596 }
2597 }
2598
2599 /**
2600 * migrate_vma_setup() - prepare to migrate a range of memory
2601 * @args: contains the vma, start, and and pfns arrays for the migration
2602 *
2603 * Returns: negative errno on failures, 0 when 0 or more pages were migrated
2604 * without an error.
2605 *
2606 * Prepare to migrate a range of memory virtual address range by collecting all
2607 * the pages backing each virtual address in the range, saving them inside the
2608 * src array. Then lock those pages and unmap them. Once the pages are locked
2609 * and unmapped, check whether each page is pinned or not. Pages that aren't
2610 * pinned have the MIGRATE_PFN_MIGRATE flag set (by this function) in the
2611 * corresponding src array entry. Then restores any pages that are pinned, by
2612 * remapping and unlocking those pages.
2613 *
2614 * The caller should then allocate destination memory and copy source memory to
2615 * it for all those entries (ie with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE
2616 * flag set). Once these are allocated and copied, the caller must update each
2617 * corresponding entry in the dst array with the pfn value of the destination
2618 * page and with the MIGRATE_PFN_VALID and MIGRATE_PFN_LOCKED flags set
2619 * (destination pages must have their struct pages locked, via lock_page()).
2620 *
2621 * Note that the caller does not have to migrate all the pages that are marked
2622 * with MIGRATE_PFN_MIGRATE flag in src array unless this is a migration from
2623 * device memory to system memory. If the caller cannot migrate a device page
2624 * back to system memory, then it must return VM_FAULT_SIGBUS, which has severe
2625 * consequences for the userspace process, so it must be avoided if at all
2626 * possible.
2627 *
2628 * For empty entries inside CPU page table (pte_none() or pmd_none() is true) we
2629 * do set MIGRATE_PFN_MIGRATE flag inside the corresponding source array thus
2630 * allowing the caller to allocate device memory for those unback virtual
2631 * address. For this the caller simply has to allocate device memory and
2632 * properly set the destination entry like for regular migration. Note that
2633 * this can still fails and thus inside the device driver must check if the
2634 * migration was successful for those entries after calling migrate_vma_pages()
2635 * just like for regular migration.
2636 *
2637 * After that, the callers must call migrate_vma_pages() to go over each entry
2638 * in the src array that has the MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag
2639 * set. If the corresponding entry in dst array has MIGRATE_PFN_VALID flag set,
2640 * then migrate_vma_pages() to migrate struct page information from the source
2641 * struct page to the destination struct page. If it fails to migrate the
2642 * struct page information, then it clears the MIGRATE_PFN_MIGRATE flag in the
2643 * src array.
2644 *
2645 * At this point all successfully migrated pages have an entry in the src
2646 * array with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag set and the dst
2647 * array entry with MIGRATE_PFN_VALID flag set.
2648 *
2649 * Once migrate_vma_pages() returns the caller may inspect which pages were
2650 * successfully migrated, and which were not. Successfully migrated pages will
2651 * have the MIGRATE_PFN_MIGRATE flag set for their src array entry.
2652 *
2653 * It is safe to update device page table after migrate_vma_pages() because
2654 * both destination and source page are still locked, and the mmap_sem is held
2655 * in read mode (hence no one can unmap the range being migrated).
2656 *
2657 * Once the caller is done cleaning up things and updating its page table (if it
2658 * chose to do so, this is not an obligation) it finally calls
2659 * migrate_vma_finalize() to update the CPU page table to point to new pages
2660 * for successfully migrated pages or otherwise restore the CPU page table to
2661 * point to the original source pages.
2662 */
2663 int migrate_vma_setup(struct migrate_vma *args)
2664 {
2665 long nr_pages = (args->end - args->start) >> PAGE_SHIFT;
2666
2667 args->start &= PAGE_MASK;
2668 args->end &= PAGE_MASK;
2669 if (!args->vma || is_vm_hugetlb_page(args->vma) ||
2670 (args->vma->vm_flags & VM_SPECIAL) || vma_is_dax(args->vma))
2671 return -EINVAL;
2672 if (nr_pages <= 0)
2673 return -EINVAL;
2674 if (args->start < args->vma->vm_start ||
2675 args->start >= args->vma->vm_end)
2676 return -EINVAL;
2677 if (args->end <= args->vma->vm_start || args->end > args->vma->vm_end)
2678 return -EINVAL;
2679 if (!args->src || !args->dst)
2680 return -EINVAL;
2681
2682 memset(args->src, 0, sizeof(*args->src) * nr_pages);
2683 args->cpages = 0;
2684 args->npages = 0;
2685
2686 migrate_vma_collect(args);
2687
2688 if (args->cpages)
2689 migrate_vma_prepare(args);
2690 if (args->cpages)
2691 migrate_vma_unmap(args);
2692
2693 /*
2694 * At this point pages are locked and unmapped, and thus they have
2695 * stable content and can safely be copied to destination memory that
2696 * is allocated by the drivers.
2697 */
2698 return 0;
2699
2700 }
2701 EXPORT_SYMBOL(migrate_vma_setup);
2702
2703 static void migrate_vma_insert_page(struct migrate_vma *migrate,
2704 unsigned long addr,
2705 struct page *page,
2706 unsigned long *src,
2707 unsigned long *dst)
2708 {
2709 struct vm_area_struct *vma = migrate->vma;
2710 struct mm_struct *mm = vma->vm_mm;
2711 struct mem_cgroup *memcg;
2712 bool flush = false;
2713 spinlock_t *ptl;
2714 pte_t entry;
2715 pgd_t *pgdp;
2716 p4d_t *p4dp;
2717 pud_t *pudp;
2718 pmd_t *pmdp;
2719 pte_t *ptep;
2720
2721 /* Only allow populating anonymous memory */
2722 if (!vma_is_anonymous(vma))
2723 goto abort;
2724
2725 pgdp = pgd_offset(mm, addr);
2726 p4dp = p4d_alloc(mm, pgdp, addr);
2727 if (!p4dp)
2728 goto abort;
2729 pudp = pud_alloc(mm, p4dp, addr);
2730 if (!pudp)
2731 goto abort;
2732 pmdp = pmd_alloc(mm, pudp, addr);
2733 if (!pmdp)
2734 goto abort;
2735
2736 if (pmd_trans_huge(*pmdp) || pmd_devmap(*pmdp))
2737 goto abort;
2738
2739 /*
2740 * Use pte_alloc() instead of pte_alloc_map(). We can't run
2741 * pte_offset_map() on pmds where a huge pmd might be created
2742 * from a different thread.
2743 *
2744 * pte_alloc_map() is safe to use under down_write(mmap_sem) or when
2745 * parallel threads are excluded by other means.
2746 *
2747 * Here we only have down_read(mmap_sem).
2748 */
2749 if (pte_alloc(mm, pmdp))
2750 goto abort;
2751
2752 /* See the comment in pte_alloc_one_map() */
2753 if (unlikely(pmd_trans_unstable(pmdp)))
2754 goto abort;
2755
2756 if (unlikely(anon_vma_prepare(vma)))
2757 goto abort;
2758 if (mem_cgroup_try_charge(page, vma->vm_mm, GFP_KERNEL, &memcg, false))
2759 goto abort;
2760
2761 /*
2762 * The memory barrier inside __SetPageUptodate makes sure that
2763 * preceding stores to the page contents become visible before
2764 * the set_pte_at() write.
2765 */
2766 __SetPageUptodate(page);
2767
2768 if (is_zone_device_page(page)) {
2769 if (is_device_private_page(page)) {
2770 swp_entry_t swp_entry;
2771
2772 swp_entry = make_device_private_entry(page, vma->vm_flags & VM_WRITE);
2773 entry = swp_entry_to_pte(swp_entry);
2774 }
2775 } else {
2776 entry = mk_pte(page, vma->vm_page_prot);
2777 if (vma->vm_flags & VM_WRITE)
2778 entry = pte_mkwrite(pte_mkdirty(entry));
2779 }
2780
2781 ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
2782
2783 if (pte_present(*ptep)) {
2784 unsigned long pfn = pte_pfn(*ptep);
2785
2786 if (!is_zero_pfn(pfn)) {
2787 pte_unmap_unlock(ptep, ptl);
2788 mem_cgroup_cancel_charge(page, memcg, false);
2789 goto abort;
2790 }
2791 flush = true;
2792 } else if (!pte_none(*ptep)) {
2793 pte_unmap_unlock(ptep, ptl);
2794 mem_cgroup_cancel_charge(page, memcg, false);
2795 goto abort;
2796 }
2797
2798 /*
2799 * Check for usefaultfd but do not deliver the fault. Instead,
2800 * just back off.
2801 */
2802 if (userfaultfd_missing(vma)) {
2803 pte_unmap_unlock(ptep, ptl);
2804 mem_cgroup_cancel_charge(page, memcg, false);
2805 goto abort;
2806 }
2807
2808 inc_mm_counter(mm, MM_ANONPAGES);
2809 page_add_new_anon_rmap(page, vma, addr, false);
2810 mem_cgroup_commit_charge(page, memcg, false, false);
2811 if (!is_zone_device_page(page))
2812 lru_cache_add_active_or_unevictable(page, vma);
2813 get_page(page);
2814
2815 if (flush) {
2816 flush_cache_page(vma, addr, pte_pfn(*ptep));
2817 ptep_clear_flush_notify(vma, addr, ptep);
2818 set_pte_at_notify(mm, addr, ptep, entry);
2819 update_mmu_cache(vma, addr, ptep);
2820 } else {
2821 /* No need to invalidate - it was non-present before */
2822 set_pte_at(mm, addr, ptep, entry);
2823 update_mmu_cache(vma, addr, ptep);
2824 }
2825
2826 pte_unmap_unlock(ptep, ptl);
2827 *src = MIGRATE_PFN_MIGRATE;
2828 return;
2829
2830 abort:
2831 *src &= ~MIGRATE_PFN_MIGRATE;
2832 }
2833
2834 /**
2835 * migrate_vma_pages() - migrate meta-data from src page to dst page
2836 * @migrate: migrate struct containing all migration information
2837 *
2838 * This migrates struct page meta-data from source struct page to destination
2839 * struct page. This effectively finishes the migration from source page to the
2840 * destination page.
2841 */
2842 void migrate_vma_pages(struct migrate_vma *migrate)
2843 {
2844 const unsigned long npages = migrate->npages;
2845 const unsigned long start = migrate->start;
2846 struct mmu_notifier_range range;
2847 unsigned long addr, i;
2848 bool notified = false;
2849
2850 for (i = 0, addr = start; i < npages; addr += PAGE_SIZE, i++) {
2851 struct page *newpage = migrate_pfn_to_page(migrate->dst[i]);
2852 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2853 struct address_space *mapping;
2854 int r;
2855
2856 if (!newpage) {
2857 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2858 continue;
2859 }
2860
2861 if (!page) {
2862 if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE)) {
2863 continue;
2864 }
2865 if (!notified) {
2866 notified = true;
2867
2868 mmu_notifier_range_init(&range,
2869 MMU_NOTIFY_CLEAR, 0,
2870 NULL,
2871 migrate->vma->vm_mm,
2872 addr, migrate->end);
2873 mmu_notifier_invalidate_range_start(&range);
2874 }
2875 migrate_vma_insert_page(migrate, addr, newpage,
2876 &migrate->src[i],
2877 &migrate->dst[i]);
2878 continue;
2879 }
2880
2881 mapping = page_mapping(page);
2882
2883 if (is_zone_device_page(newpage)) {
2884 if (is_device_private_page(newpage)) {
2885 /*
2886 * For now only support private anonymous when
2887 * migrating to un-addressable device memory.
2888 */
2889 if (mapping) {
2890 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2891 continue;
2892 }
2893 } else {
2894 /*
2895 * Other types of ZONE_DEVICE page are not
2896 * supported.
2897 */
2898 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2899 continue;
2900 }
2901 }
2902
2903 r = migrate_page(mapping, newpage, page, MIGRATE_SYNC_NO_COPY);
2904 if (r != MIGRATEPAGE_SUCCESS)
2905 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2906 }
2907
2908 /*
2909 * No need to double call mmu_notifier->invalidate_range() callback as
2910 * the above ptep_clear_flush_notify() inside migrate_vma_insert_page()
2911 * did already call it.
2912 */
2913 if (notified)
2914 mmu_notifier_invalidate_range_only_end(&range);
2915 }
2916 EXPORT_SYMBOL(migrate_vma_pages);
2917
2918 /**
2919 * migrate_vma_finalize() - restore CPU page table entry
2920 * @migrate: migrate struct containing all migration information
2921 *
2922 * This replaces the special migration pte entry with either a mapping to the
2923 * new page if migration was successful for that page, or to the original page
2924 * otherwise.
2925 *
2926 * This also unlocks the pages and puts them back on the lru, or drops the extra
2927 * refcount, for device pages.
2928 */
2929 void migrate_vma_finalize(struct migrate_vma *migrate)
2930 {
2931 const unsigned long npages = migrate->npages;
2932 unsigned long i;
2933
2934 for (i = 0; i < npages; i++) {
2935 struct page *newpage = migrate_pfn_to_page(migrate->dst[i]);
2936 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2937
2938 if (!page) {
2939 if (newpage) {
2940 unlock_page(newpage);
2941 put_page(newpage);
2942 }
2943 continue;
2944 }
2945
2946 if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE) || !newpage) {
2947 if (newpage) {
2948 unlock_page(newpage);
2949 put_page(newpage);
2950 }
2951 newpage = page;
2952 }
2953
2954 remove_migration_ptes(page, newpage, false);
2955 unlock_page(page);
2956 migrate->cpages--;
2957
2958 if (is_zone_device_page(page))
2959 put_page(page);
2960 else
2961 putback_lru_page(page);
2962
2963 if (newpage != page) {
2964 unlock_page(newpage);
2965 if (is_zone_device_page(newpage))
2966 put_page(newpage);
2967 else
2968 putback_lru_page(newpage);
2969 }
2970 }
2971 }
2972 EXPORT_SYMBOL(migrate_vma_finalize);
2973 #endif /* CONFIG_DEVICE_PRIVATE */