summaryrefslogtreecommitdiff
path: root/mm/migrate_device.c
blob: 5052093d0262d708eb9b573154d1038d07a462eb (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
// SPDX-License-Identifier: GPL-2.0
/*
 * Device Memory Migration functionality.
 *
 * Originally written by Jérôme Glisse.
 */
#include <linux/export.h>
#include <linux/memremap.h>
#include <linux/migrate.h>
#include <linux/mm_inline.h>
#include <linux/mmu_notifier.h>
#include <linux/oom.h>
#include <linux/pagewalk.h>
#include <linux/rmap.h>
#include <linux/swapops.h>
#include <asm/tlbflush.h>
#include "internal.h"

static int migrate_vma_collect_skip(unsigned long start,
				    unsigned long end,
				    struct mm_walk *walk)
{
	struct migrate_vma *migrate = walk->private;
	unsigned long addr;

	for (addr = start; addr < end; addr += PAGE_SIZE) {
		migrate->dst[migrate->npages] = 0;
		migrate->src[migrate->npages++] = 0;
	}

	return 0;
}

static int migrate_vma_collect_hole(unsigned long start,
				    unsigned long end,
				    __always_unused int depth,
				    struct mm_walk *walk)
{
	struct migrate_vma *migrate = walk->private;
	unsigned long addr;

	/* Only allow populating anonymous memory. */
	if (!vma_is_anonymous(walk->vma))
		return migrate_vma_collect_skip(start, end, walk);

	for (addr = start; addr < end; addr += PAGE_SIZE) {
		migrate->src[migrate->npages] = MIGRATE_PFN_MIGRATE;
		migrate->dst[migrate->npages] = 0;
		migrate->npages++;
		migrate->cpages++;
	}

	return 0;
}

static int migrate_vma_collect_pmd(pmd_t *pmdp,
				   unsigned long start,
				   unsigned long end,
				   struct mm_walk *walk)
{
	struct migrate_vma *migrate = walk->private;
	struct vm_area_struct *vma = walk->vma;
	struct mm_struct *mm = vma->vm_mm;
	unsigned long addr = start, unmapped = 0;
	spinlock_t *ptl;
	pte_t *ptep;

again:
	if (pmd_none(*pmdp))
		return migrate_vma_collect_hole(start, end, -1, walk);

	if (pmd_trans_huge(*pmdp)) {
		struct page *page;

		ptl = pmd_lock(mm, pmdp);
		if (unlikely(!pmd_trans_huge(*pmdp))) {
			spin_unlock(ptl);
			goto again;
		}

		page = pmd_page(*pmdp);
		if (is_huge_zero_page(page)) {
			spin_unlock(ptl);
			split_huge_pmd(vma, pmdp, addr);
			if (pmd_trans_unstable(pmdp))
				return migrate_vma_collect_skip(start, end,
								walk);
		} else {
			int ret;

			get_page(page);
			spin_unlock(ptl);
			if (unlikely(!trylock_page(page)))
				return migrate_vma_collect_skip(start, end,
								walk);
			ret = split_huge_page(page);
			unlock_page(page);
			put_page(page);
			if (ret)
				return migrate_vma_collect_skip(start, end,
								walk);
			if (pmd_none(*pmdp))
				return migrate_vma_collect_hole(start, end, -1,
								walk);
		}
	}

	if (unlikely(pmd_bad(*pmdp)))
		return migrate_vma_collect_skip(start, end, walk);

	ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
	arch_enter_lazy_mmu_mode();

	for (; addr < end; addr += PAGE_SIZE, ptep++) {
		unsigned long mpfn = 0, pfn;
		struct page *page;
		swp_entry_t entry;
		pte_t pte;

		pte = *ptep;

		if (pte_none(pte)) {
			if (vma_is_anonymous(vma)) {
				mpfn = MIGRATE_PFN_MIGRATE;
				migrate->cpages++;
			}
			goto next;
		}

		if (!pte_present(pte)) {
			/*
			 * Only care about unaddressable device page special
			 * page table entry. Other special swap entries are not
			 * migratable, and we ignore regular swapped page.
			 */
			entry = pte_to_swp_entry(pte);
			if (!is_device_private_entry(entry))
				goto next;

			page = pfn_swap_entry_to_page(entry);
			if (!(migrate->flags &
				MIGRATE_VMA_SELECT_DEVICE_PRIVATE) ||
			    page->pgmap->owner != migrate->pgmap_owner)
				goto next;

			mpfn = migrate_pfn(page_to_pfn(page)) |
					MIGRATE_PFN_MIGRATE;
			if (is_writable_device_private_entry(entry))
				mpfn |= MIGRATE_PFN_WRITE;
		} else {
			if (!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM))
				goto next;
			pfn = pte_pfn(pte);
			if (is_zero_pfn(pfn)) {
				mpfn = MIGRATE_PFN_MIGRATE;
				migrate->cpages++;
				goto next;
			}
			page = vm_normal_page(migrate->vma, addr, pte);
			mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
			mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
		}

		/* FIXME support THP */
		if (!page || !page->mapping || PageTransCompound(page)) {
			mpfn = 0;
			goto next;
		}

		/*
		 * By getting a reference on the page we pin it and that blocks
		 * any kind of migration. Side effect is that it "freezes" the
		 * pte.
		 *
		 * We drop this reference after isolating the page from the lru
		 * for non device page (device page are not on the lru and thus
		 * can't be dropped from it).
		 */
		get_page(page);

		/*
		 * Optimize for the common case where page is only mapped once
		 * in one process. If we can lock the page, then we can safely
		 * set up a special migration page table entry now.
		 */
		if (trylock_page(page)) {
			bool anon_exclusive;
			pte_t swp_pte;

			anon_exclusive = PageAnon(page) && PageAnonExclusive(page);
			if (anon_exclusive) {
				flush_cache_page(vma, addr, pte_pfn(*ptep));
				ptep_clear_flush(vma, addr, ptep);

				if (page_try_share_anon_rmap(page)) {
					set_pte_at(mm, addr, ptep, pte);
					unlock_page(page);
					put_page(page);
					mpfn = 0;
					goto next;
				}
			} else {
				ptep_get_and_clear(mm, addr, ptep);
			}

			migrate->cpages++;

			/* Setup special migration page table entry */
			if (mpfn & MIGRATE_PFN_WRITE)
				entry = make_writable_migration_entry(
							page_to_pfn(page));
			else if (anon_exclusive)
				entry = make_readable_exclusive_migration_entry(
							page_to_pfn(page));
			else
				entry = make_readable_migration_entry(
							page_to_pfn(page));
			swp_pte = swp_entry_to_pte(entry);
			if (pte_present(pte)) {
				if (pte_soft_dirty(pte))
					swp_pte = pte_swp_mksoft_dirty(swp_pte);
				if (pte_uffd_wp(pte))
					swp_pte = pte_swp_mkuffd_wp(swp_pte);
			} else {
				if (pte_swp_soft_dirty(pte))
					swp_pte = pte_swp_mksoft_dirty(swp_pte);
				if (pte_swp_uffd_wp(pte))
					swp_pte = pte_swp_mkuffd_wp(swp_pte);
			}
			set_pte_at(mm, addr, ptep, swp_pte);

			/*
			 * This is like regular unmap: we remove the rmap and
			 * drop page refcount. Page won't be freed, as we took
			 * a reference just above.
			 */
			page_remove_rmap(page, vma, false);
			put_page(page);

			if (pte_present(pte))
				unmapped++;
		} else {
			put_page(page);
			mpfn = 0;
		}

next:
		migrate->dst[migrate->npages] = 0;
		migrate->src[migrate->npages++] = mpfn;
	}
	arch_leave_lazy_mmu_mode();
	pte_unmap_unlock(ptep - 1, ptl);

	/* Only flush the TLB if we actually modified any entries */
	if (unmapped)
		flush_tlb_range(walk->vma, start, end);

	return 0;
}

static const struct mm_walk_ops migrate_vma_walk_ops = {
	.pmd_entry		= migrate_vma_collect_pmd,
	.pte_hole		= migrate_vma_collect_hole,
};

/*
 * migrate_vma_collect() - collect pages over a range of virtual addresses
 * @migrate: migrate struct containing all migration information
 *
 * This will walk the CPU page table. For each virtual address backed by a
 * valid page, it updates the src array and takes a reference on the page, in
 * order to pin the page until we lock it and unmap it.
 */
static void migrate_vma_collect(struct migrate_vma *migrate)
{
	struct mmu_notifier_range range;

	/*
	 * Note that the pgmap_owner is passed to the mmu notifier callback so
	 * that the registered device driver can skip invalidating device
	 * private page mappings that won't be migrated.
	 */
	mmu_notifier_range_init_owner(&range, MMU_NOTIFY_MIGRATE, 0,
		migrate->vma, migrate->vma->vm_mm, migrate->start, migrate->end,
		migrate->pgmap_owner);
	mmu_notifier_invalidate_range_start(&range);

	walk_page_range(migrate->vma->vm_mm, migrate->start, migrate->end,
			&migrate_vma_walk_ops, migrate);

	mmu_notifier_invalidate_range_end(&range);
	migrate->end = migrate->start + (migrate->npages << PAGE_SHIFT);
}

/*
 * migrate_vma_check_page() - check if page is pinned or not
 * @page: struct page to check
 *
 * Pinned pages cannot be migrated. This is the same test as in
 * folio_migrate_mapping(), except that here we allow migration of a
 * ZONE_DEVICE page.
 */
static bool migrate_vma_check_page(struct page *page)
{
	/*
	 * One extra ref because caller holds an extra reference, either from
	 * isolate_lru_page() for a regular page, or migrate_vma_collect() for
	 * a device page.
	 */
	int extra = 1;

	/*
	 * FIXME support THP (transparent huge page), it is bit more complex to
	 * check them than regular pages, because they can be mapped with a pmd
	 * or with a pte (split pte mapping).
	 */
	if (PageCompound(page))
		return false;

	/* Page from ZONE_DEVICE have one extra reference */
	if (is_zone_device_page(page))
		extra++;

	/* For file back page */
	if (page_mapping(page))
		extra += 1 + page_has_private(page);

	if ((page_count(page) - extra) > page_mapcount(page))
		return false;

	return true;
}

/*
 * migrate_vma_unmap() - replace page mapping with special migration pte entry
 * @migrate: migrate struct containing all migration information
 *
 * Isolate pages from the LRU and replace mappings (CPU page table pte) with a
 * special migration pte entry and check if it has been pinned. Pinned pages are
 * restored because we cannot migrate them.
 *
 * This is the last step before we call the device driver callback to allocate
 * destination memory and copy contents of original page over to new page.
 */
static void migrate_vma_unmap(struct migrate_vma *migrate)
{
	const unsigned long npages = migrate->npages;
	unsigned long i, restore = 0;
	bool allow_drain = true;

	lru_add_drain();

	for (i = 0; i < npages; i++) {
		struct page *page = migrate_pfn_to_page(migrate->src[i]);
		struct folio *folio;

		if (!page)
			continue;

		/* ZONE_DEVICE pages are not on LRU */
		if (!is_zone_device_page(page)) {
			if (!PageLRU(page) && allow_drain) {
				/* Drain CPU's pagevec */
				lru_add_drain_all();
				allow_drain = false;
			}

			if (isolate_lru_page(page)) {
				migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
				migrate->cpages--;
				restore++;
				continue;
			}

			/* Drop the reference we took in collect */
			put_page(page);
		}

		folio = page_folio(page);
		if (folio_mapped(folio))
			try_to_migrate(folio, 0);

		if (page_mapped(page) || !migrate_vma_check_page(page)) {
			if (!is_zone_device_page(page)) {
				get_page(page);
				putback_lru_page(page);
			}

			migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
			migrate->cpages--;
			restore++;
			continue;
		}
	}

	for (i = 0; i < npages && restore; i++) {
		struct page *page = migrate_pfn_to_page(migrate->src[i]);
		struct folio *folio;

		if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE))
			continue;

		folio = page_folio(page);
		remove_migration_ptes(folio, folio, false);

		migrate->src[i] = 0;
		folio_unlock(folio);
		folio_put(folio);
		restore--;
	}
}

/**
 * migrate_vma_setup() - prepare to migrate a range of memory
 * @args: contains the vma, start, and pfns arrays for the migration
 *
 * Returns: negative errno on failures, 0 when 0 or more pages were migrated
 * without an error.
 *
 * Prepare to migrate a range of memory virtual address range by collecting all
 * the pages backing each virtual address in the range, saving them inside the
 * src array.  Then lock those pages and unmap them. Once the pages are locked
 * and unmapped, check whether each page is pinned or not.  Pages that aren't
 * pinned have the MIGRATE_PFN_MIGRATE flag set (by this function) in the
 * corresponding src array entry.  Then restores any pages that are pinned, by
 * remapping and unlocking those pages.
 *
 * The caller should then allocate destination memory and copy source memory to
 * it for all those entries (ie with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE
 * flag set).  Once these are allocated and copied, the caller must update each
 * corresponding entry in the dst array with the pfn value of the destination
 * page and with MIGRATE_PFN_VALID. Destination pages must be locked via
 * lock_page().
 *
 * Note that the caller does not have to migrate all the pages that are marked
 * with MIGRATE_PFN_MIGRATE flag in src array unless this is a migration from
 * device memory to system memory.  If the caller cannot migrate a device page
 * back to system memory, then it must return VM_FAULT_SIGBUS, which has severe
 * consequences for the userspace process, so it must be avoided if at all
 * possible.
 *
 * For empty entries inside CPU page table (pte_none() or pmd_none() is true) we
 * do set MIGRATE_PFN_MIGRATE flag inside the corresponding source array thus
 * allowing the caller to allocate device memory for those unbacked virtual
 * addresses.  For this the caller simply has to allocate device memory and
 * properly set the destination entry like for regular migration.  Note that
 * this can still fail, and thus inside the device driver you must check if the
 * migration was successful for those entries after calling migrate_vma_pages(),
 * just like for regular migration.
 *
 * After that, the callers must call migrate_vma_pages() to go over each entry
 * in the src array that has the MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag
 * set. If the corresponding entry in dst array has MIGRATE_PFN_VALID flag set,
 * then migrate_vma_pages() to migrate struct page information from the source
 * struct page to the destination struct page.  If it fails to migrate the
 * struct page information, then it clears the MIGRATE_PFN_MIGRATE flag in the
 * src array.
 *
 * At this point all successfully migrated pages have an entry in the src
 * array with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag set and the dst
 * array entry with MIGRATE_PFN_VALID flag set.
 *
 * Once migrate_vma_pages() returns the caller may inspect which pages were
 * successfully migrated, and which were not.  Successfully migrated pages will
 * have the MIGRATE_PFN_MIGRATE flag set for their src array entry.
 *
 * It is safe to update device page table after migrate_vma_pages() because
 * both destination and source page are still locked, and the mmap_lock is held
 * in read mode (hence no one can unmap the range being migrated).
 *
 * Once the caller is done cleaning up things and updating its page table (if it
 * chose to do so, this is not an obligation) it finally calls
 * migrate_vma_finalize() to update the CPU page table to point to new pages
 * for successfully migrated pages or otherwise restore the CPU page table to
 * point to the original source pages.
 */
int migrate_vma_setup(struct migrate_vma *args)
{
	long nr_pages = (args->end - args->start) >> PAGE_SHIFT;

	args->start &= PAGE_MASK;
	args->end &= PAGE_MASK;
	if (!args->vma || is_vm_hugetlb_page(args->vma) ||
	    (args->vma->vm_flags & VM_SPECIAL) || vma_is_dax(args->vma))
		return -EINVAL;
	if (nr_pages <= 0)
		return -EINVAL;
	if (args->start < args->vma->vm_start ||
	    args->start >= args->vma->vm_end)
		return -EINVAL;
	if (args->end <= args->vma->vm_start || args->end > args->vma->vm_end)
		return -EINVAL;
	if (!args->src || !args->dst)
		return -EINVAL;

	memset(args->src, 0, sizeof(*args->src) * nr_pages);
	args->cpages = 0;
	args->npages = 0;

	migrate_vma_collect(args);

	if (args->cpages)
		migrate_vma_unmap(args);

	/*
	 * At this point pages are locked and unmapped, and thus they have
	 * stable content and can safely be copied to destination memory that
	 * is allocated by the drivers.
	 */
	return 0;

}
EXPORT_SYMBOL(migrate_vma_setup);

/*
 * This code closely matches the code in:
 *   __handle_mm_fault()
 *     handle_pte_fault()
 *       do_anonymous_page()
 * to map in an anonymous zero page but the struct page will be a ZONE_DEVICE
 * private page.
 */
static void migrate_vma_insert_page(struct migrate_vma *migrate,
				    unsigned long addr,
				    struct page *page,
				    unsigned long *src)
{
	struct vm_area_struct *vma = migrate->vma;
	struct mm_struct *mm = vma->vm_mm;
	bool flush = false;
	spinlock_t *ptl;
	pte_t entry;
	pgd_t *pgdp;
	p4d_t *p4dp;
	pud_t *pudp;
	pmd_t *pmdp;
	pte_t *ptep;

	/* Only allow populating anonymous memory */
	if (!vma_is_anonymous(vma))
		goto abort;

	pgdp = pgd_offset(mm, addr);
	p4dp = p4d_alloc(mm, pgdp, addr);
	if (!p4dp)
		goto abort;
	pudp = pud_alloc(mm, p4dp, addr);
	if (!pudp)
		goto abort;
	pmdp = pmd_alloc(mm, pudp, addr);
	if (!pmdp)
		goto abort;

	if (pmd_trans_huge(*pmdp) || pmd_devmap(*pmdp))
		goto abort;

	/*
	 * Use pte_alloc() instead of pte_alloc_map().  We can't run
	 * pte_offset_map() on pmds where a huge pmd might be created
	 * from a different thread.
	 *
	 * pte_alloc_map() is safe to use under mmap_write_lock(mm) or when
	 * parallel threads are excluded by other means.
	 *
	 * Here we only have mmap_read_lock(mm).
	 */
	if (pte_alloc(mm, pmdp))
		goto abort;

	/* See the comment in pte_alloc_one_map() */
	if (unlikely(pmd_trans_unstable(pmdp)))
		goto abort;

	if (unlikely(anon_vma_prepare(vma)))
		goto abort;
	if (mem_cgroup_charge(page_folio(page), vma->vm_mm, GFP_KERNEL))
		goto abort;

	/*
	 * The memory barrier inside __SetPageUptodate makes sure that
	 * preceding stores to the page contents become visible before
	 * the set_pte_at() write.
	 */
	__SetPageUptodate(page);

	if (is_device_private_page(page)) {
		swp_entry_t swp_entry;

		if (vma->vm_flags & VM_WRITE)
			swp_entry = make_writable_device_private_entry(
						page_to_pfn(page));
		else
			swp_entry = make_readable_device_private_entry(
						page_to_pfn(page));
		entry = swp_entry_to_pte(swp_entry);
	} else {
		/*
		 * For now we only support migrating to un-addressable device
		 * memory.
		 */
		if (is_zone_device_page(page)) {
			pr_warn_once("Unsupported ZONE_DEVICE page type.\n");
			goto abort;
		}
		entry = mk_pte(page, vma->vm_page_prot);
		if (vma->vm_flags & VM_WRITE)
			entry = pte_mkwrite(pte_mkdirty(entry));
	}

	ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);

	if (check_stable_address_space(mm))
		goto unlock_abort;

	if (pte_present(*ptep)) {
		unsigned long pfn = pte_pfn(*ptep);

		if (!is_zero_pfn(pfn))
			goto unlock_abort;
		flush = true;
	} else if (!pte_none(*ptep))
		goto unlock_abort;

	/*
	 * Check for userfaultfd but do not deliver the fault. Instead,
	 * just back off.
	 */
	if (userfaultfd_missing(vma))
		goto unlock_abort;

	inc_mm_counter(mm, MM_ANONPAGES);
	page_add_new_anon_rmap(page, vma, addr);
	if (!is_zone_device_page(page))
		lru_cache_add_inactive_or_unevictable(page, vma);
	get_page(page);

	if (flush) {
		flush_cache_page(vma, addr, pte_pfn(*ptep));
		ptep_clear_flush_notify(vma, addr, ptep);
		set_pte_at_notify(mm, addr, ptep, entry);
		update_mmu_cache(vma, addr, ptep);
	} else {
		/* No need to invalidate - it was non-present before */
		set_pte_at(mm, addr, ptep, entry);
		update_mmu_cache(vma, addr, ptep);
	}

	pte_unmap_unlock(ptep, ptl);
	*src = MIGRATE_PFN_MIGRATE;
	return;

unlock_abort:
	pte_unmap_unlock(ptep, ptl);
abort:
	*src &= ~MIGRATE_PFN_MIGRATE;
}

/**
 * migrate_vma_pages() - migrate meta-data from src page to dst page
 * @migrate: migrate struct containing all migration information
 *
 * This migrates struct page meta-data from source struct page to destination
 * struct page. This effectively finishes the migration from source page to the
 * destination page.
 */
void migrate_vma_pages(struct migrate_vma *migrate)
{
	const unsigned long npages = migrate->npages;
	const unsigned long start = migrate->start;
	struct mmu_notifier_range range;
	unsigned long addr, i;
	bool notified = false;

	for (i = 0, addr = start; i < npages; addr += PAGE_SIZE, i++) {
		struct page *newpage = migrate_pfn_to_page(migrate->dst[i]);
		struct page *page = migrate_pfn_to_page(migrate->src[i]);
		struct address_space *mapping;
		int r;

		if (!newpage) {
			migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
			continue;
		}

		if (!page) {
			if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE))
				continue;
			if (!notified) {
				notified = true;

				mmu_notifier_range_init_owner(&range,
					MMU_NOTIFY_MIGRATE, 0, migrate->vma,
					migrate->vma->vm_mm, addr, migrate->end,
					migrate->pgmap_owner);
				mmu_notifier_invalidate_range_start(&range);
			}
			migrate_vma_insert_page(migrate, addr, newpage,
						&migrate->src[i]);
			continue;
		}

		mapping = page_mapping(page);

		if (is_device_private_page(newpage)) {
			/*
			 * For now only support private anonymous when migrating
			 * to un-addressable device memory.
			 */
			if (mapping) {
				migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
				continue;
			}
		} else if (is_zone_device_page(newpage)) {
			/*
			 * Other types of ZONE_DEVICE page are not supported.
			 */
			migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
			continue;
		}

		r = migrate_page(mapping, newpage, page, MIGRATE_SYNC_NO_COPY);
		if (r != MIGRATEPAGE_SUCCESS)
			migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
	}

	/*
	 * No need to double call mmu_notifier->invalidate_range() callback as
	 * the above ptep_clear_flush_notify() inside migrate_vma_insert_page()
	 * did already call it.
	 */
	if (notified)
		mmu_notifier_invalidate_range_only_end(&range);
}
EXPORT_SYMBOL(migrate_vma_pages);

/**
 * migrate_vma_finalize() - restore CPU page table entry
 * @migrate: migrate struct containing all migration information
 *
 * This replaces the special migration pte entry with either a mapping to the
 * new page if migration was successful for that page, or to the original page
 * otherwise.
 *
 * This also unlocks the pages and puts them back on the lru, or drops the extra
 * refcount, for device pages.
 */
void migrate_vma_finalize(struct migrate_vma *migrate)
{
	const unsigned long npages = migrate->npages;
	unsigned long i;

	for (i = 0; i < npages; i++) {
		struct folio *dst, *src;
		struct page *newpage = migrate_pfn_to_page(migrate->dst[i]);
		struct page *page = migrate_pfn_to_page(migrate->src[i]);

		if (!page) {
			if (newpage) {
				unlock_page(newpage);
				put_page(newpage);
			}
			continue;
		}

		if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE) || !newpage) {
			if (newpage) {
				unlock_page(newpage);
				put_page(newpage);
			}
			newpage = page;
		}

		src = page_folio(page);
		dst = page_folio(newpage);
		remove_migration_ptes(src, dst, false);
		folio_unlock(src);

		if (is_zone_device_page(page))
			put_page(page);
		else
			putback_lru_page(page);

		if (newpage != page) {
			unlock_page(newpage);
			if (is_zone_device_page(newpage))
				put_page(newpage);
			else
				putback_lru_page(newpage);
		}
	}
}
EXPORT_SYMBOL(migrate_vma_finalize);