mm/page_alloc.c: move ifdefery out of free_area_init_core
[platform/kernel/linux-rpi.git] / mm / migrate.c
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Memory Migration functionality - linux/mm/migrate.c
4  *
5  * Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter
6  *
7  * Page migration was first developed in the context of the memory hotplug
8  * project. The main authors of the migration code are:
9  *
10  * IWAMOTO Toshihiro <iwamoto@valinux.co.jp>
11  * Hirokazu Takahashi <taka@valinux.co.jp>
12  * Dave Hansen <haveblue@us.ibm.com>
13  * Christoph Lameter
14  */
15
16 #include <linux/migrate.h>
17 #include <linux/export.h>
18 #include <linux/swap.h>
19 #include <linux/swapops.h>
20 #include <linux/pagemap.h>
21 #include <linux/buffer_head.h>
22 #include <linux/mm_inline.h>
23 #include <linux/nsproxy.h>
24 #include <linux/pagevec.h>
25 #include <linux/ksm.h>
26 #include <linux/rmap.h>
27 #include <linux/topology.h>
28 #include <linux/cpu.h>
29 #include <linux/cpuset.h>
30 #include <linux/writeback.h>
31 #include <linux/mempolicy.h>
32 #include <linux/vmalloc.h>
33 #include <linux/security.h>
34 #include <linux/backing-dev.h>
35 #include <linux/compaction.h>
36 #include <linux/syscalls.h>
37 #include <linux/compat.h>
38 #include <linux/hugetlb.h>
39 #include <linux/hugetlb_cgroup.h>
40 #include <linux/gfp.h>
41 #include <linux/pfn_t.h>
42 #include <linux/memremap.h>
43 #include <linux/userfaultfd_k.h>
44 #include <linux/balloon_compaction.h>
45 #include <linux/mmu_notifier.h>
46 #include <linux/page_idle.h>
47 #include <linux/page_owner.h>
48 #include <linux/sched/mm.h>
49 #include <linux/ptrace.h>
50
51 #include <asm/tlbflush.h>
52
53 #define CREATE_TRACE_POINTS
54 #include <trace/events/migrate.h>
55
56 #include "internal.h"
57
58 /*
59  * migrate_prep() needs to be called before we start compiling a list of pages
60  * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
61  * undesirable, use migrate_prep_local()
62  */
63 int migrate_prep(void)
64 {
65         /*
66          * Clear the LRU lists so pages can be isolated.
67          * Note that pages may be moved off the LRU after we have
68          * drained them. Those pages will fail to migrate like other
69          * pages that may be busy.
70          */
71         lru_add_drain_all();
72
73         return 0;
74 }
75
76 /* Do the necessary work of migrate_prep but not if it involves other CPUs */
77 int migrate_prep_local(void)
78 {
79         lru_add_drain();
80
81         return 0;
82 }
83
84 int isolate_movable_page(struct page *page, isolate_mode_t mode)
85 {
86         struct address_space *mapping;
87
88         /*
89          * Avoid burning cycles with pages that are yet under __free_pages(),
90          * or just got freed under us.
91          *
92          * In case we 'win' a race for a movable page being freed under us and
93          * raise its refcount preventing __free_pages() from doing its job
94          * the put_page() at the end of this block will take care of
95          * release this page, thus avoiding a nasty leakage.
96          */
97         if (unlikely(!get_page_unless_zero(page)))
98                 goto out;
99
100         /*
101          * Check PageMovable before holding a PG_lock because page's owner
102          * assumes anybody doesn't touch PG_lock of newly allocated page
103          * so unconditionally grapping the lock ruins page's owner side.
104          */
105         if (unlikely(!__PageMovable(page)))
106                 goto out_putpage;
107         /*
108          * As movable pages are not isolated from LRU lists, concurrent
109          * compaction threads can race against page migration functions
110          * as well as race against the releasing a page.
111          *
112          * In order to avoid having an already isolated movable page
113          * being (wrongly) re-isolated while it is under migration,
114          * or to avoid attempting to isolate pages being released,
115          * lets be sure we have the page lock
116          * before proceeding with the movable page isolation steps.
117          */
118         if (unlikely(!trylock_page(page)))
119                 goto out_putpage;
120
121         if (!PageMovable(page) || PageIsolated(page))
122                 goto out_no_isolated;
123
124         mapping = page_mapping(page);
125         VM_BUG_ON_PAGE(!mapping, page);
126
127         if (!mapping->a_ops->isolate_page(page, mode))
128                 goto out_no_isolated;
129
130         /* Driver shouldn't use PG_isolated bit of page->flags */
131         WARN_ON_ONCE(PageIsolated(page));
132         __SetPageIsolated(page);
133         unlock_page(page);
134
135         return 0;
136
137 out_no_isolated:
138         unlock_page(page);
139 out_putpage:
140         put_page(page);
141 out:
142         return -EBUSY;
143 }
144
145 /* It should be called on page which is PG_movable */
146 void putback_movable_page(struct page *page)
147 {
148         struct address_space *mapping;
149
150         VM_BUG_ON_PAGE(!PageLocked(page), page);
151         VM_BUG_ON_PAGE(!PageMovable(page), page);
152         VM_BUG_ON_PAGE(!PageIsolated(page), page);
153
154         mapping = page_mapping(page);
155         mapping->a_ops->putback_page(page);
156         __ClearPageIsolated(page);
157 }
158
159 /*
160  * Put previously isolated pages back onto the appropriate lists
161  * from where they were once taken off for compaction/migration.
162  *
163  * This function shall be used whenever the isolated pageset has been
164  * built from lru, balloon, hugetlbfs page. See isolate_migratepages_range()
165  * and isolate_huge_page().
166  */
167 void putback_movable_pages(struct list_head *l)
168 {
169         struct page *page;
170         struct page *page2;
171
172         list_for_each_entry_safe(page, page2, l, lru) {
173                 if (unlikely(PageHuge(page))) {
174                         putback_active_hugepage(page);
175                         continue;
176                 }
177                 list_del(&page->lru);
178                 /*
179                  * We isolated non-lru movable page so here we can use
180                  * __PageMovable because LRU page's mapping cannot have
181                  * PAGE_MAPPING_MOVABLE.
182                  */
183                 if (unlikely(__PageMovable(page))) {
184                         VM_BUG_ON_PAGE(!PageIsolated(page), page);
185                         lock_page(page);
186                         if (PageMovable(page))
187                                 putback_movable_page(page);
188                         else
189                                 __ClearPageIsolated(page);
190                         unlock_page(page);
191                         put_page(page);
192                 } else {
193                         mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
194                                         page_is_file_cache(page), -hpage_nr_pages(page));
195                         putback_lru_page(page);
196                 }
197         }
198 }
199
200 /*
201  * Restore a potential migration pte to a working pte entry
202  */
203 static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma,
204                                  unsigned long addr, void *old)
205 {
206         struct page_vma_mapped_walk pvmw = {
207                 .page = old,
208                 .vma = vma,
209                 .address = addr,
210                 .flags = PVMW_SYNC | PVMW_MIGRATION,
211         };
212         struct page *new;
213         pte_t pte;
214         swp_entry_t entry;
215
216         VM_BUG_ON_PAGE(PageTail(page), page);
217         while (page_vma_mapped_walk(&pvmw)) {
218                 if (PageKsm(page))
219                         new = page;
220                 else
221                         new = page - pvmw.page->index +
222                                 linear_page_index(vma, pvmw.address);
223
224 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
225                 /* PMD-mapped THP migration entry */
226                 if (!pvmw.pte) {
227                         VM_BUG_ON_PAGE(PageHuge(page) || !PageTransCompound(page), page);
228                         remove_migration_pmd(&pvmw, new);
229                         continue;
230                 }
231 #endif
232
233                 get_page(new);
234                 pte = pte_mkold(mk_pte(new, READ_ONCE(vma->vm_page_prot)));
235                 if (pte_swp_soft_dirty(*pvmw.pte))
236                         pte = pte_mksoft_dirty(pte);
237
238                 /*
239                  * Recheck VMA as permissions can change since migration started
240                  */
241                 entry = pte_to_swp_entry(*pvmw.pte);
242                 if (is_write_migration_entry(entry))
243                         pte = maybe_mkwrite(pte, vma);
244
245                 if (unlikely(is_zone_device_page(new))) {
246                         if (is_device_private_page(new)) {
247                                 entry = make_device_private_entry(new, pte_write(pte));
248                                 pte = swp_entry_to_pte(entry);
249                         } else if (is_device_public_page(new)) {
250                                 pte = pte_mkdevmap(pte);
251                                 flush_dcache_page(new);
252                         }
253                 } else
254                         flush_dcache_page(new);
255
256 #ifdef CONFIG_HUGETLB_PAGE
257                 if (PageHuge(new)) {
258                         pte = pte_mkhuge(pte);
259                         pte = arch_make_huge_pte(pte, vma, new, 0);
260                         set_huge_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
261                         if (PageAnon(new))
262                                 hugepage_add_anon_rmap(new, vma, pvmw.address);
263                         else
264                                 page_dup_rmap(new, true);
265                 } else
266 #endif
267                 {
268                         set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
269
270                         if (PageAnon(new))
271                                 page_add_anon_rmap(new, vma, pvmw.address, false);
272                         else
273                                 page_add_file_rmap(new, false);
274                 }
275                 if (vma->vm_flags & VM_LOCKED && !PageTransCompound(new))
276                         mlock_vma_page(new);
277
278                 /* No need to invalidate - it was non-present before */
279                 update_mmu_cache(vma, pvmw.address, pvmw.pte);
280         }
281
282         return true;
283 }
284
285 /*
286  * Get rid of all migration entries and replace them by
287  * references to the indicated page.
288  */
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 radix-tree replacement of page migration started, page_count
327          * *must* be zero. And, we don't want to call wait_on_page_locked()
328          * against a page without get_page().
329          * So, we use get_page_unless_zero(), here. Even failed, page fault
330          * will occur again.
331          */
332         if (!get_page_unless_zero(page))
333                 goto out;
334         pte_unmap_unlock(ptep, ptl);
335         wait_on_page_locked(page);
336         put_page(page);
337         return;
338 out:
339         pte_unmap_unlock(ptep, ptl);
340 }
341
342 void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
343                                 unsigned long address)
344 {
345         spinlock_t *ptl = pte_lockptr(mm, pmd);
346         pte_t *ptep = pte_offset_map(pmd, address);
347         __migration_entry_wait(mm, ptep, ptl);
348 }
349
350 void migration_entry_wait_huge(struct vm_area_struct *vma,
351                 struct mm_struct *mm, pte_t *pte)
352 {
353         spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), mm, pte);
354         __migration_entry_wait(mm, pte, ptl);
355 }
356
357 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
358 void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)
359 {
360         spinlock_t *ptl;
361         struct page *page;
362
363         ptl = pmd_lock(mm, pmd);
364         if (!is_pmd_migration_entry(*pmd))
365                 goto unlock;
366         page = migration_entry_to_page(pmd_to_swp_entry(*pmd));
367         if (!get_page_unless_zero(page))
368                 goto unlock;
369         spin_unlock(ptl);
370         wait_on_page_locked(page);
371         put_page(page);
372         return;
373 unlock:
374         spin_unlock(ptl);
375 }
376 #endif
377
378 #ifdef CONFIG_BLOCK
379 /* Returns true if all buffers are successfully locked */
380 static bool buffer_migrate_lock_buffers(struct buffer_head *head,
381                                                         enum migrate_mode mode)
382 {
383         struct buffer_head *bh = head;
384
385         /* Simple case, sync compaction */
386         if (mode != MIGRATE_ASYNC) {
387                 do {
388                         get_bh(bh);
389                         lock_buffer(bh);
390                         bh = bh->b_this_page;
391
392                 } while (bh != head);
393
394                 return true;
395         }
396
397         /* async case, we cannot block on lock_buffer so use trylock_buffer */
398         do {
399                 get_bh(bh);
400                 if (!trylock_buffer(bh)) {
401                         /*
402                          * We failed to lock the buffer and cannot stall in
403                          * async migration. Release the taken locks
404                          */
405                         struct buffer_head *failed_bh = bh;
406                         put_bh(failed_bh);
407                         bh = head;
408                         while (bh != failed_bh) {
409                                 unlock_buffer(bh);
410                                 put_bh(bh);
411                                 bh = bh->b_this_page;
412                         }
413                         return false;
414                 }
415
416                 bh = bh->b_this_page;
417         } while (bh != head);
418         return true;
419 }
420 #else
421 static inline bool buffer_migrate_lock_buffers(struct buffer_head *head,
422                                                         enum migrate_mode mode)
423 {
424         return true;
425 }
426 #endif /* CONFIG_BLOCK */
427
428 /*
429  * Replace the page in the mapping.
430  *
431  * The number of remaining references must be:
432  * 1 for anonymous pages without a mapping
433  * 2 for pages with a mapping
434  * 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
435  */
436 int migrate_page_move_mapping(struct address_space *mapping,
437                 struct page *newpage, struct page *page,
438                 struct buffer_head *head, enum migrate_mode mode,
439                 int extra_count)
440 {
441         struct zone *oldzone, *newzone;
442         int dirty;
443         int expected_count = 1 + extra_count;
444         void **pslot;
445
446         /*
447          * Device public or private pages have an extra refcount as they are
448          * ZONE_DEVICE pages.
449          */
450         expected_count += is_device_private_page(page);
451         expected_count += is_device_public_page(page);
452
453         if (!mapping) {
454                 /* Anonymous page without mapping */
455                 if (page_count(page) != expected_count)
456                         return -EAGAIN;
457
458                 /* No turning back from here */
459                 newpage->index = page->index;
460                 newpage->mapping = page->mapping;
461                 if (PageSwapBacked(page))
462                         __SetPageSwapBacked(newpage);
463
464                 return MIGRATEPAGE_SUCCESS;
465         }
466
467         oldzone = page_zone(page);
468         newzone = page_zone(newpage);
469
470         xa_lock_irq(&mapping->i_pages);
471
472         pslot = radix_tree_lookup_slot(&mapping->i_pages,
473                                         page_index(page));
474
475         expected_count += hpage_nr_pages(page) + page_has_private(page);
476         if (page_count(page) != expected_count ||
477                 radix_tree_deref_slot_protected(pslot,
478                                         &mapping->i_pages.xa_lock) != page) {
479                 xa_unlock_irq(&mapping->i_pages);
480                 return -EAGAIN;
481         }
482
483         if (!page_ref_freeze(page, expected_count)) {
484                 xa_unlock_irq(&mapping->i_pages);
485                 return -EAGAIN;
486         }
487
488         /*
489          * In the async migration case of moving a page with buffers, lock the
490          * buffers using trylock before the mapping is moved. If the mapping
491          * was moved, we later failed to lock the buffers and could not move
492          * the mapping back due to an elevated page count, we would have to
493          * block waiting on other references to be dropped.
494          */
495         if (mode == MIGRATE_ASYNC && head &&
496                         !buffer_migrate_lock_buffers(head, mode)) {
497                 page_ref_unfreeze(page, expected_count);
498                 xa_unlock_irq(&mapping->i_pages);
499                 return -EAGAIN;
500         }
501
502         /*
503          * Now we know that no one else is looking at the page:
504          * no turning back from here.
505          */
506         newpage->index = page->index;
507         newpage->mapping = page->mapping;
508         page_ref_add(newpage, hpage_nr_pages(page)); /* add cache reference */
509         if (PageSwapBacked(page)) {
510                 __SetPageSwapBacked(newpage);
511                 if (PageSwapCache(page)) {
512                         SetPageSwapCache(newpage);
513                         set_page_private(newpage, page_private(page));
514                 }
515         } else {
516                 VM_BUG_ON_PAGE(PageSwapCache(page), page);
517         }
518
519         /* Move dirty while page refs frozen and newpage not yet exposed */
520         dirty = PageDirty(page);
521         if (dirty) {
522                 ClearPageDirty(page);
523                 SetPageDirty(newpage);
524         }
525
526         radix_tree_replace_slot(&mapping->i_pages, pslot, newpage);
527         if (PageTransHuge(page)) {
528                 int i;
529                 int index = page_index(page);
530
531                 for (i = 1; i < HPAGE_PMD_NR; i++) {
532                         pslot = radix_tree_lookup_slot(&mapping->i_pages,
533                                                        index + i);
534                         radix_tree_replace_slot(&mapping->i_pages, pslot,
535                                                 newpage + i);
536                 }
537         }
538
539         /*
540          * Drop cache reference from old page by unfreezing
541          * to one less reference.
542          * We know this isn't the last reference.
543          */
544         page_ref_unfreeze(page, expected_count - hpage_nr_pages(page));
545
546         xa_unlock(&mapping->i_pages);
547         /* Leave irq disabled to prevent preemption while updating stats */
548
549         /*
550          * If moved to a different zone then also account
551          * the page for that zone. Other VM counters will be
552          * taken care of when we establish references to the
553          * new page and drop references to the old page.
554          *
555          * Note that anonymous pages are accounted for
556          * via NR_FILE_PAGES and NR_ANON_MAPPED if they
557          * are mapped to swap space.
558          */
559         if (newzone != oldzone) {
560                 __dec_node_state(oldzone->zone_pgdat, NR_FILE_PAGES);
561                 __inc_node_state(newzone->zone_pgdat, NR_FILE_PAGES);
562                 if (PageSwapBacked(page) && !PageSwapCache(page)) {
563                         __dec_node_state(oldzone->zone_pgdat, NR_SHMEM);
564                         __inc_node_state(newzone->zone_pgdat, NR_SHMEM);
565                 }
566                 if (dirty && mapping_cap_account_dirty(mapping)) {
567                         __dec_node_state(oldzone->zone_pgdat, NR_FILE_DIRTY);
568                         __dec_zone_state(oldzone, NR_ZONE_WRITE_PENDING);
569                         __inc_node_state(newzone->zone_pgdat, NR_FILE_DIRTY);
570                         __inc_zone_state(newzone, NR_ZONE_WRITE_PENDING);
571                 }
572         }
573         local_irq_enable();
574
575         return MIGRATEPAGE_SUCCESS;
576 }
577 EXPORT_SYMBOL(migrate_page_move_mapping);
578
579 /*
580  * The expected number of remaining references is the same as that
581  * of migrate_page_move_mapping().
582  */
583 int migrate_huge_page_move_mapping(struct address_space *mapping,
584                                    struct page *newpage, struct page *page)
585 {
586         int expected_count;
587         void **pslot;
588
589         xa_lock_irq(&mapping->i_pages);
590
591         pslot = radix_tree_lookup_slot(&mapping->i_pages, page_index(page));
592
593         expected_count = 2 + page_has_private(page);
594         if (page_count(page) != expected_count ||
595                 radix_tree_deref_slot_protected(pslot, &mapping->i_pages.xa_lock) != page) {
596                 xa_unlock_irq(&mapping->i_pages);
597                 return -EAGAIN;
598         }
599
600         if (!page_ref_freeze(page, expected_count)) {
601                 xa_unlock_irq(&mapping->i_pages);
602                 return -EAGAIN;
603         }
604
605         newpage->index = page->index;
606         newpage->mapping = page->mapping;
607
608         get_page(newpage);
609
610         radix_tree_replace_slot(&mapping->i_pages, pslot, newpage);
611
612         page_ref_unfreeze(page, expected_count - 1);
613
614         xa_unlock_irq(&mapping->i_pages);
615
616         return MIGRATEPAGE_SUCCESS;
617 }
618
619 /*
620  * Gigantic pages are so large that we do not guarantee that page++ pointer
621  * arithmetic will work across the entire page.  We need something more
622  * specialized.
623  */
624 static void __copy_gigantic_page(struct page *dst, struct page *src,
625                                 int nr_pages)
626 {
627         int i;
628         struct page *dst_base = dst;
629         struct page *src_base = src;
630
631         for (i = 0; i < nr_pages; ) {
632                 cond_resched();
633                 copy_highpage(dst, src);
634
635                 i++;
636                 dst = mem_map_next(dst, dst_base, i);
637                 src = mem_map_next(src, src_base, i);
638         }
639 }
640
641 static void copy_huge_page(struct page *dst, struct page *src)
642 {
643         int i;
644         int nr_pages;
645
646         if (PageHuge(src)) {
647                 /* hugetlbfs page */
648                 struct hstate *h = page_hstate(src);
649                 nr_pages = pages_per_huge_page(h);
650
651                 if (unlikely(nr_pages > MAX_ORDER_NR_PAGES)) {
652                         __copy_gigantic_page(dst, src, nr_pages);
653                         return;
654                 }
655         } else {
656                 /* thp page */
657                 BUG_ON(!PageTransHuge(src));
658                 nr_pages = hpage_nr_pages(src);
659         }
660
661         for (i = 0; i < nr_pages; i++) {
662                 cond_resched();
663                 copy_highpage(dst + i, src + i);
664         }
665 }
666
667 /*
668  * Copy the page to its new location
669  */
670 void migrate_page_states(struct page *newpage, struct page *page)
671 {
672         int cpupid;
673
674         if (PageError(page))
675                 SetPageError(newpage);
676         if (PageReferenced(page))
677                 SetPageReferenced(newpage);
678         if (PageUptodate(page))
679                 SetPageUptodate(newpage);
680         if (TestClearPageActive(page)) {
681                 VM_BUG_ON_PAGE(PageUnevictable(page), page);
682                 SetPageActive(newpage);
683         } else if (TestClearPageUnevictable(page))
684                 SetPageUnevictable(newpage);
685         if (PageChecked(page))
686                 SetPageChecked(newpage);
687         if (PageMappedToDisk(page))
688                 SetPageMappedToDisk(newpage);
689
690         /* Move dirty on pages not done by migrate_page_move_mapping() */
691         if (PageDirty(page))
692                 SetPageDirty(newpage);
693
694         if (page_is_young(page))
695                 set_page_young(newpage);
696         if (page_is_idle(page))
697                 set_page_idle(newpage);
698
699         /*
700          * Copy NUMA information to the new page, to prevent over-eager
701          * future migrations of this same page.
702          */
703         cpupid = page_cpupid_xchg_last(page, -1);
704         page_cpupid_xchg_last(newpage, cpupid);
705
706         ksm_migrate_page(newpage, page);
707         /*
708          * Please do not reorder this without considering how mm/ksm.c's
709          * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
710          */
711         if (PageSwapCache(page))
712                 ClearPageSwapCache(page);
713         ClearPagePrivate(page);
714         set_page_private(page, 0);
715
716         /*
717          * If any waiters have accumulated on the new page then
718          * wake them up.
719          */
720         if (PageWriteback(newpage))
721                 end_page_writeback(newpage);
722
723         copy_page_owner(page, newpage);
724
725         mem_cgroup_migrate(page, newpage);
726 }
727 EXPORT_SYMBOL(migrate_page_states);
728
729 void migrate_page_copy(struct page *newpage, struct page *page)
730 {
731         if (PageHuge(page) || PageTransHuge(page))
732                 copy_huge_page(newpage, page);
733         else
734                 copy_highpage(newpage, page);
735
736         migrate_page_states(newpage, page);
737 }
738 EXPORT_SYMBOL(migrate_page_copy);
739
740 /************************************************************
741  *                    Migration functions
742  ***********************************************************/
743
744 /*
745  * Common logic to directly migrate a single LRU page suitable for
746  * pages that do not use PagePrivate/PagePrivate2.
747  *
748  * Pages are locked upon entry and exit.
749  */
750 int migrate_page(struct address_space *mapping,
751                 struct page *newpage, struct page *page,
752                 enum migrate_mode mode)
753 {
754         int rc;
755
756         BUG_ON(PageWriteback(page));    /* Writeback must be complete */
757
758         rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode, 0);
759
760         if (rc != MIGRATEPAGE_SUCCESS)
761                 return rc;
762
763         if (mode != MIGRATE_SYNC_NO_COPY)
764                 migrate_page_copy(newpage, page);
765         else
766                 migrate_page_states(newpage, page);
767         return MIGRATEPAGE_SUCCESS;
768 }
769 EXPORT_SYMBOL(migrate_page);
770
771 #ifdef CONFIG_BLOCK
772 /*
773  * Migration function for pages with buffers. This function can only be used
774  * if the underlying filesystem guarantees that no other references to "page"
775  * exist.
776  */
777 int buffer_migrate_page(struct address_space *mapping,
778                 struct page *newpage, struct page *page, enum migrate_mode mode)
779 {
780         struct buffer_head *bh, *head;
781         int rc;
782
783         if (!page_has_buffers(page))
784                 return migrate_page(mapping, newpage, page, mode);
785
786         head = page_buffers(page);
787
788         rc = migrate_page_move_mapping(mapping, newpage, page, head, mode, 0);
789
790         if (rc != MIGRATEPAGE_SUCCESS)
791                 return rc;
792
793         /*
794          * In the async case, migrate_page_move_mapping locked the buffers
795          * with an IRQ-safe spinlock held. In the sync case, the buffers
796          * need to be locked now
797          */
798         if (mode != MIGRATE_ASYNC)
799                 BUG_ON(!buffer_migrate_lock_buffers(head, mode));
800
801         ClearPagePrivate(page);
802         set_page_private(newpage, page_private(page));
803         set_page_private(page, 0);
804         put_page(page);
805         get_page(newpage);
806
807         bh = head;
808         do {
809                 set_bh_page(bh, newpage, bh_offset(bh));
810                 bh = bh->b_this_page;
811
812         } while (bh != head);
813
814         SetPagePrivate(newpage);
815
816         if (mode != MIGRATE_SYNC_NO_COPY)
817                 migrate_page_copy(newpage, page);
818         else
819                 migrate_page_states(newpage, page);
820
821         bh = head;
822         do {
823                 unlock_buffer(bh);
824                 put_bh(bh);
825                 bh = bh->b_this_page;
826
827         } while (bh != head);
828
829         return MIGRATEPAGE_SUCCESS;
830 }
831 EXPORT_SYMBOL(buffer_migrate_page);
832 #endif
833
834 /*
835  * Writeback a page to clean the dirty state
836  */
837 static int writeout(struct address_space *mapping, struct page *page)
838 {
839         struct writeback_control wbc = {
840                 .sync_mode = WB_SYNC_NONE,
841                 .nr_to_write = 1,
842                 .range_start = 0,
843                 .range_end = LLONG_MAX,
844                 .for_reclaim = 1
845         };
846         int rc;
847
848         if (!mapping->a_ops->writepage)
849                 /* No write method for the address space */
850                 return -EINVAL;
851
852         if (!clear_page_dirty_for_io(page))
853                 /* Someone else already triggered a write */
854                 return -EAGAIN;
855
856         /*
857          * A dirty page may imply that the underlying filesystem has
858          * the page on some queue. So the page must be clean for
859          * migration. Writeout may mean we loose the lock and the
860          * page state is no longer what we checked for earlier.
861          * At this point we know that the migration attempt cannot
862          * be successful.
863          */
864         remove_migration_ptes(page, page, false);
865
866         rc = mapping->a_ops->writepage(page, &wbc);
867
868         if (rc != AOP_WRITEPAGE_ACTIVATE)
869                 /* unlocked. Relock */
870                 lock_page(page);
871
872         return (rc < 0) ? -EIO : -EAGAIN;
873 }
874
875 /*
876  * Default handling if a filesystem does not provide a migration function.
877  */
878 static int fallback_migrate_page(struct address_space *mapping,
879         struct page *newpage, struct page *page, enum migrate_mode mode)
880 {
881         if (PageDirty(page)) {
882                 /* Only writeback pages in full synchronous migration */
883                 switch (mode) {
884                 case MIGRATE_SYNC:
885                 case MIGRATE_SYNC_NO_COPY:
886                         break;
887                 default:
888                         return -EBUSY;
889                 }
890                 return writeout(mapping, page);
891         }
892
893         /*
894          * Buffers may be managed in a filesystem specific way.
895          * We must have no buffers or drop them.
896          */
897         if (page_has_private(page) &&
898             !try_to_release_page(page, GFP_KERNEL))
899                 return -EAGAIN;
900
901         return migrate_page(mapping, newpage, page, mode);
902 }
903
904 /*
905  * Move a page to a newly allocated page
906  * The page is locked and all ptes have been successfully removed.
907  *
908  * The new page will have replaced the old page if this function
909  * is successful.
910  *
911  * Return value:
912  *   < 0 - error code
913  *  MIGRATEPAGE_SUCCESS - success
914  */
915 static int move_to_new_page(struct page *newpage, struct page *page,
916                                 enum migrate_mode mode)
917 {
918         struct address_space *mapping;
919         int rc = -EAGAIN;
920         bool is_lru = !__PageMovable(page);
921
922         VM_BUG_ON_PAGE(!PageLocked(page), page);
923         VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
924
925         mapping = page_mapping(page);
926
927         if (likely(is_lru)) {
928                 if (!mapping)
929                         rc = migrate_page(mapping, newpage, page, mode);
930                 else if (mapping->a_ops->migratepage)
931                         /*
932                          * Most pages have a mapping and most filesystems
933                          * provide a migratepage callback. Anonymous pages
934                          * are part of swap space which also has its own
935                          * migratepage callback. This is the most common path
936                          * for page migration.
937                          */
938                         rc = mapping->a_ops->migratepage(mapping, newpage,
939                                                         page, mode);
940                 else
941                         rc = fallback_migrate_page(mapping, newpage,
942                                                         page, mode);
943         } else {
944                 /*
945                  * In case of non-lru page, it could be released after
946                  * isolation step. In that case, we shouldn't try migration.
947                  */
948                 VM_BUG_ON_PAGE(!PageIsolated(page), page);
949                 if (!PageMovable(page)) {
950                         rc = MIGRATEPAGE_SUCCESS;
951                         __ClearPageIsolated(page);
952                         goto out;
953                 }
954
955                 rc = mapping->a_ops->migratepage(mapping, newpage,
956                                                 page, mode);
957                 WARN_ON_ONCE(rc == MIGRATEPAGE_SUCCESS &&
958                         !PageIsolated(page));
959         }
960
961         /*
962          * When successful, old pagecache page->mapping must be cleared before
963          * page is freed; but stats require that PageAnon be left as PageAnon.
964          */
965         if (rc == MIGRATEPAGE_SUCCESS) {
966                 if (__PageMovable(page)) {
967                         VM_BUG_ON_PAGE(!PageIsolated(page), page);
968
969                         /*
970                          * We clear PG_movable under page_lock so any compactor
971                          * cannot try to migrate this page.
972                          */
973                         __ClearPageIsolated(page);
974                 }
975
976                 /*
977                  * Anonymous and movable page->mapping will be cleard by
978                  * free_pages_prepare so don't reset it here for keeping
979                  * the type to work PageAnon, for example.
980                  */
981                 if (!PageMappingFlags(page))
982                         page->mapping = NULL;
983         }
984 out:
985         return rc;
986 }
987
988 static int __unmap_and_move(struct page *page, struct page *newpage,
989                                 int force, enum migrate_mode mode)
990 {
991         int rc = -EAGAIN;
992         int page_was_mapped = 0;
993         struct anon_vma *anon_vma = NULL;
994         bool is_lru = !__PageMovable(page);
995
996         if (!trylock_page(page)) {
997                 if (!force || mode == MIGRATE_ASYNC)
998                         goto out;
999
1000                 /*
1001                  * It's not safe for direct compaction to call lock_page.
1002                  * For example, during page readahead pages are added locked
1003                  * to the LRU. Later, when the IO completes the pages are
1004                  * marked uptodate and unlocked. However, the queueing
1005                  * could be merging multiple pages for one bio (e.g.
1006                  * mpage_readpages). If an allocation happens for the
1007                  * second or third page, the process can end up locking
1008                  * the same page twice and deadlocking. Rather than
1009                  * trying to be clever about what pages can be locked,
1010                  * avoid the use of lock_page for direct compaction
1011                  * altogether.
1012                  */
1013                 if (current->flags & PF_MEMALLOC)
1014                         goto out;
1015
1016                 lock_page(page);
1017         }
1018
1019         if (PageWriteback(page)) {
1020                 /*
1021                  * Only in the case of a full synchronous migration is it
1022                  * necessary to wait for PageWriteback. In the async case,
1023                  * the retry loop is too short and in the sync-light case,
1024                  * the overhead of stalling is too much
1025                  */
1026                 switch (mode) {
1027                 case MIGRATE_SYNC:
1028                 case MIGRATE_SYNC_NO_COPY:
1029                         break;
1030                 default:
1031                         rc = -EBUSY;
1032                         goto out_unlock;
1033                 }
1034                 if (!force)
1035                         goto out_unlock;
1036                 wait_on_page_writeback(page);
1037         }
1038
1039         /*
1040          * By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
1041          * we cannot notice that anon_vma is freed while we migrates a page.
1042          * This get_anon_vma() delays freeing anon_vma pointer until the end
1043          * of migration. File cache pages are no problem because of page_lock()
1044          * File Caches may use write_page() or lock_page() in migration, then,
1045          * just care Anon page here.
1046          *
1047          * Only page_get_anon_vma() understands the subtleties of
1048          * getting a hold on an anon_vma from outside one of its mms.
1049          * But if we cannot get anon_vma, then we won't need it anyway,
1050          * because that implies that the anon page is no longer mapped
1051          * (and cannot be remapped so long as we hold the page lock).
1052          */
1053         if (PageAnon(page) && !PageKsm(page))
1054                 anon_vma = page_get_anon_vma(page);
1055
1056         /*
1057          * Block others from accessing the new page when we get around to
1058          * establishing additional references. We are usually the only one
1059          * holding a reference to newpage at this point. We used to have a BUG
1060          * here if trylock_page(newpage) fails, but would like to allow for
1061          * cases where there might be a race with the previous use of newpage.
1062          * This is much like races on refcount of oldpage: just don't BUG().
1063          */
1064         if (unlikely(!trylock_page(newpage)))
1065                 goto out_unlock;
1066
1067         if (unlikely(!is_lru)) {
1068                 rc = move_to_new_page(newpage, page, mode);
1069                 goto out_unlock_both;
1070         }
1071
1072         /*
1073          * Corner case handling:
1074          * 1. When a new swap-cache page is read into, it is added to the LRU
1075          * and treated as swapcache but it has no rmap yet.
1076          * Calling try_to_unmap() against a page->mapping==NULL page will
1077          * trigger a BUG.  So handle it here.
1078          * 2. An orphaned page (see truncate_complete_page) might have
1079          * fs-private metadata. The page can be picked up due to memory
1080          * offlining.  Everywhere else except page reclaim, the page is
1081          * invisible to the vm, so the page can not be migrated.  So try to
1082          * free the metadata, so the page can be freed.
1083          */
1084         if (!page->mapping) {
1085                 VM_BUG_ON_PAGE(PageAnon(page), page);
1086                 if (page_has_private(page)) {
1087                         try_to_free_buffers(page);
1088                         goto out_unlock_both;
1089                 }
1090         } else if (page_mapped(page)) {
1091                 /* Establish migration ptes */
1092                 VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma,
1093                                 page);
1094                 try_to_unmap(page,
1095                         TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
1096                 page_was_mapped = 1;
1097         }
1098
1099         if (!page_mapped(page))
1100                 rc = move_to_new_page(newpage, page, mode);
1101
1102         if (page_was_mapped)
1103                 remove_migration_ptes(page,
1104                         rc == MIGRATEPAGE_SUCCESS ? newpage : page, false);
1105
1106 out_unlock_both:
1107         unlock_page(newpage);
1108 out_unlock:
1109         /* Drop an anon_vma reference if we took one */
1110         if (anon_vma)
1111                 put_anon_vma(anon_vma);
1112         unlock_page(page);
1113 out:
1114         /*
1115          * If migration is successful, decrease refcount of the newpage
1116          * which will not free the page because new page owner increased
1117          * refcounter. As well, if it is LRU page, add the page to LRU
1118          * list in here.
1119          */
1120         if (rc == MIGRATEPAGE_SUCCESS) {
1121                 if (unlikely(__PageMovable(newpage)))
1122                         put_page(newpage);
1123                 else
1124                         putback_lru_page(newpage);
1125         }
1126
1127         return rc;
1128 }
1129
1130 /*
1131  * gcc 4.7 and 4.8 on arm get an ICEs when inlining unmap_and_move().  Work
1132  * around it.
1133  */
1134 #if (GCC_VERSION >= 40700 && GCC_VERSION < 40900) && defined(CONFIG_ARM)
1135 #define ICE_noinline noinline
1136 #else
1137 #define ICE_noinline
1138 #endif
1139
1140 /*
1141  * Obtain the lock on page, remove all ptes and migrate the page
1142  * to the newly allocated page in newpage.
1143  */
1144 static ICE_noinline int unmap_and_move(new_page_t get_new_page,
1145                                    free_page_t put_new_page,
1146                                    unsigned long private, struct page *page,
1147                                    int force, enum migrate_mode mode,
1148                                    enum migrate_reason reason)
1149 {
1150         int rc = MIGRATEPAGE_SUCCESS;
1151         struct page *newpage;
1152
1153         if (!thp_migration_supported() && PageTransHuge(page))
1154                 return -ENOMEM;
1155
1156         newpage = get_new_page(page, private);
1157         if (!newpage)
1158                 return -ENOMEM;
1159
1160         if (page_count(page) == 1) {
1161                 /* page was freed from under us. So we are done. */
1162                 ClearPageActive(page);
1163                 ClearPageUnevictable(page);
1164                 if (unlikely(__PageMovable(page))) {
1165                         lock_page(page);
1166                         if (!PageMovable(page))
1167                                 __ClearPageIsolated(page);
1168                         unlock_page(page);
1169                 }
1170                 if (put_new_page)
1171                         put_new_page(newpage, private);
1172                 else
1173                         put_page(newpage);
1174                 goto out;
1175         }
1176
1177         rc = __unmap_and_move(page, newpage, force, mode);
1178         if (rc == MIGRATEPAGE_SUCCESS)
1179                 set_page_owner_migrate_reason(newpage, reason);
1180
1181 out:
1182         if (rc != -EAGAIN) {
1183                 /*
1184                  * A page that has been migrated has all references
1185                  * removed and will be freed. A page that has not been
1186                  * migrated will have kepts its references and be
1187                  * restored.
1188                  */
1189                 list_del(&page->lru);
1190
1191                 /*
1192                  * Compaction can migrate also non-LRU pages which are
1193                  * not accounted to NR_ISOLATED_*. They can be recognized
1194                  * as __PageMovable
1195                  */
1196                 if (likely(!__PageMovable(page)))
1197                         mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
1198                                         page_is_file_cache(page), -hpage_nr_pages(page));
1199         }
1200
1201         /*
1202          * If migration is successful, releases reference grabbed during
1203          * isolation. Otherwise, restore the page to right list unless
1204          * we want to retry.
1205          */
1206         if (rc == MIGRATEPAGE_SUCCESS) {
1207                 put_page(page);
1208                 if (reason == MR_MEMORY_FAILURE) {
1209                         /*
1210                          * Set PG_HWPoison on just freed page
1211                          * intentionally. Although it's rather weird,
1212                          * it's how HWPoison flag works at the moment.
1213                          */
1214                         if (!test_set_page_hwpoison(page))
1215                                 num_poisoned_pages_inc();
1216                 }
1217         } else {
1218                 if (rc != -EAGAIN) {
1219                         if (likely(!__PageMovable(page))) {
1220                                 putback_lru_page(page);
1221                                 goto put_new;
1222                         }
1223
1224                         lock_page(page);
1225                         if (PageMovable(page))
1226                                 putback_movable_page(page);
1227                         else
1228                                 __ClearPageIsolated(page);
1229                         unlock_page(page);
1230                         put_page(page);
1231                 }
1232 put_new:
1233                 if (put_new_page)
1234                         put_new_page(newpage, private);
1235                 else
1236                         put_page(newpage);
1237         }
1238
1239         return rc;
1240 }
1241
1242 /*
1243  * Counterpart of unmap_and_move_page() for hugepage migration.
1244  *
1245  * This function doesn't wait the completion of hugepage I/O
1246  * because there is no race between I/O and migration for hugepage.
1247  * Note that currently hugepage I/O occurs only in direct I/O
1248  * where no lock is held and PG_writeback is irrelevant,
1249  * and writeback status of all subpages are counted in the reference
1250  * count of the head page (i.e. if all subpages of a 2MB hugepage are
1251  * under direct I/O, the reference of the head page is 512 and a bit more.)
1252  * This means that when we try to migrate hugepage whose subpages are
1253  * doing direct I/O, some references remain after try_to_unmap() and
1254  * hugepage migration fails without data corruption.
1255  *
1256  * There is also no race when direct I/O is issued on the page under migration,
1257  * because then pte is replaced with migration swap entry and direct I/O code
1258  * will wait in the page fault for migration to complete.
1259  */
1260 static int unmap_and_move_huge_page(new_page_t get_new_page,
1261                                 free_page_t put_new_page, unsigned long private,
1262                                 struct page *hpage, int force,
1263                                 enum migrate_mode mode, int reason)
1264 {
1265         int rc = -EAGAIN;
1266         int page_was_mapped = 0;
1267         struct page *new_hpage;
1268         struct anon_vma *anon_vma = NULL;
1269
1270         /*
1271          * Movability of hugepages depends on architectures and hugepage size.
1272          * This check is necessary because some callers of hugepage migration
1273          * like soft offline and memory hotremove don't walk through page
1274          * tables or check whether the hugepage is pmd-based or not before
1275          * kicking migration.
1276          */
1277         if (!hugepage_migration_supported(page_hstate(hpage))) {
1278                 putback_active_hugepage(hpage);
1279                 return -ENOSYS;
1280         }
1281
1282         new_hpage = get_new_page(hpage, private);
1283         if (!new_hpage)
1284                 return -ENOMEM;
1285
1286         if (!trylock_page(hpage)) {
1287                 if (!force)
1288                         goto out;
1289                 switch (mode) {
1290                 case MIGRATE_SYNC:
1291                 case MIGRATE_SYNC_NO_COPY:
1292                         break;
1293                 default:
1294                         goto out;
1295                 }
1296                 lock_page(hpage);
1297         }
1298
1299         if (PageAnon(hpage))
1300                 anon_vma = page_get_anon_vma(hpage);
1301
1302         if (unlikely(!trylock_page(new_hpage)))
1303                 goto put_anon;
1304
1305         if (page_mapped(hpage)) {
1306                 try_to_unmap(hpage,
1307                         TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
1308                 page_was_mapped = 1;
1309         }
1310
1311         if (!page_mapped(hpage))
1312                 rc = move_to_new_page(new_hpage, hpage, mode);
1313
1314         if (page_was_mapped)
1315                 remove_migration_ptes(hpage,
1316                         rc == MIGRATEPAGE_SUCCESS ? new_hpage : hpage, false);
1317
1318         unlock_page(new_hpage);
1319
1320 put_anon:
1321         if (anon_vma)
1322                 put_anon_vma(anon_vma);
1323
1324         if (rc == MIGRATEPAGE_SUCCESS) {
1325                 move_hugetlb_state(hpage, new_hpage, reason);
1326                 put_new_page = NULL;
1327         }
1328
1329         unlock_page(hpage);
1330 out:
1331         if (rc != -EAGAIN)
1332                 putback_active_hugepage(hpage);
1333         if (reason == MR_MEMORY_FAILURE && !test_set_page_hwpoison(hpage))
1334                 num_poisoned_pages_inc();
1335
1336         /*
1337          * If migration was not successful and there's a freeing callback, use
1338          * it.  Otherwise, put_page() will drop the reference grabbed during
1339          * isolation.
1340          */
1341         if (put_new_page)
1342                 put_new_page(new_hpage, private);
1343         else
1344                 putback_active_hugepage(new_hpage);
1345
1346         return rc;
1347 }
1348
1349 /*
1350  * migrate_pages - migrate the pages specified in a list, to the free pages
1351  *                 supplied as the target for the page migration
1352  *
1353  * @from:               The list of pages to be migrated.
1354  * @get_new_page:       The function used to allocate free pages to be used
1355  *                      as the target of the page migration.
1356  * @put_new_page:       The function used to free target pages if migration
1357  *                      fails, or NULL if no special handling is necessary.
1358  * @private:            Private data to be passed on to get_new_page()
1359  * @mode:               The migration mode that specifies the constraints for
1360  *                      page migration, if any.
1361  * @reason:             The reason for page migration.
1362  *
1363  * The function returns after 10 attempts or if no pages are movable any more
1364  * because the list has become empty or no retryable pages exist any more.
1365  * The caller should call putback_movable_pages() to return pages to the LRU
1366  * or free list only if ret != 0.
1367  *
1368  * Returns the number of pages that were not migrated, or an error code.
1369  */
1370 int migrate_pages(struct list_head *from, new_page_t get_new_page,
1371                 free_page_t put_new_page, unsigned long private,
1372                 enum migrate_mode mode, int reason)
1373 {
1374         int retry = 1;
1375         int nr_failed = 0;
1376         int nr_succeeded = 0;
1377         int pass = 0;
1378         struct page *page;
1379         struct page *page2;
1380         int swapwrite = current->flags & PF_SWAPWRITE;
1381         int rc;
1382
1383         if (!swapwrite)
1384                 current->flags |= PF_SWAPWRITE;
1385
1386         for(pass = 0; pass < 10 && retry; pass++) {
1387                 retry = 0;
1388
1389                 list_for_each_entry_safe(page, page2, from, lru) {
1390 retry:
1391                         cond_resched();
1392
1393                         if (PageHuge(page))
1394                                 rc = unmap_and_move_huge_page(get_new_page,
1395                                                 put_new_page, private, page,
1396                                                 pass > 2, mode, reason);
1397                         else
1398                                 rc = unmap_and_move(get_new_page, put_new_page,
1399                                                 private, page, pass > 2, mode,
1400                                                 reason);
1401
1402                         switch(rc) {
1403                         case -ENOMEM:
1404                                 /*
1405                                  * THP migration might be unsupported or the
1406                                  * allocation could've failed so we should
1407                                  * retry on the same page with the THP split
1408                                  * to base pages.
1409                                  *
1410                                  * Head page is retried immediately and tail
1411                                  * pages are added to the tail of the list so
1412                                  * we encounter them after the rest of the list
1413                                  * is processed.
1414                                  */
1415                                 if (PageTransHuge(page)) {
1416                                         lock_page(page);
1417                                         rc = split_huge_page_to_list(page, from);
1418                                         unlock_page(page);
1419                                         if (!rc) {
1420                                                 list_safe_reset_next(page, page2, lru);
1421                                                 goto retry;
1422                                         }
1423                                 }
1424                                 nr_failed++;
1425                                 goto out;
1426                         case -EAGAIN:
1427                                 retry++;
1428                                 break;
1429                         case MIGRATEPAGE_SUCCESS:
1430                                 nr_succeeded++;
1431                                 break;
1432                         default:
1433                                 /*
1434                                  * Permanent failure (-EBUSY, -ENOSYS, etc.):
1435                                  * unlike -EAGAIN case, the failed page is
1436                                  * removed from migration page list and not
1437                                  * retried in the next outer loop.
1438                                  */
1439                                 nr_failed++;
1440                                 break;
1441                         }
1442                 }
1443         }
1444         nr_failed += retry;
1445         rc = nr_failed;
1446 out:
1447         if (nr_succeeded)
1448                 count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
1449         if (nr_failed)
1450                 count_vm_events(PGMIGRATE_FAIL, nr_failed);
1451         trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason);
1452
1453         if (!swapwrite)
1454                 current->flags &= ~PF_SWAPWRITE;
1455
1456         return rc;
1457 }
1458
1459 #ifdef CONFIG_NUMA
1460
1461 static int store_status(int __user *status, int start, int value, int nr)
1462 {
1463         while (nr-- > 0) {
1464                 if (put_user(value, status + start))
1465                         return -EFAULT;
1466                 start++;
1467         }
1468
1469         return 0;
1470 }
1471
1472 static int do_move_pages_to_node(struct mm_struct *mm,
1473                 struct list_head *pagelist, int node)
1474 {
1475         int err;
1476
1477         if (list_empty(pagelist))
1478                 return 0;
1479
1480         err = migrate_pages(pagelist, alloc_new_node_page, NULL, node,
1481                         MIGRATE_SYNC, MR_SYSCALL);
1482         if (err)
1483                 putback_movable_pages(pagelist);
1484         return err;
1485 }
1486
1487 /*
1488  * Resolves the given address to a struct page, isolates it from the LRU and
1489  * puts it to the given pagelist.
1490  * Returns -errno if the page cannot be found/isolated or 0 when it has been
1491  * queued or the page doesn't need to be migrated because it is already on
1492  * the target node
1493  */
1494 static int add_page_for_migration(struct mm_struct *mm, unsigned long addr,
1495                 int node, struct list_head *pagelist, bool migrate_all)
1496 {
1497         struct vm_area_struct *vma;
1498         struct page *page;
1499         unsigned int follflags;
1500         int err;
1501
1502         down_read(&mm->mmap_sem);
1503         err = -EFAULT;
1504         vma = find_vma(mm, addr);
1505         if (!vma || addr < vma->vm_start || !vma_migratable(vma))
1506                 goto out;
1507
1508         /* FOLL_DUMP to ignore special (like zero) pages */
1509         follflags = FOLL_GET | FOLL_DUMP;
1510         page = follow_page(vma, addr, follflags);
1511
1512         err = PTR_ERR(page);
1513         if (IS_ERR(page))
1514                 goto out;
1515
1516         err = -ENOENT;
1517         if (!page)
1518                 goto out;
1519
1520         err = 0;
1521         if (page_to_nid(page) == node)
1522                 goto out_putpage;
1523
1524         err = -EACCES;
1525         if (page_mapcount(page) > 1 && !migrate_all)
1526                 goto out_putpage;
1527
1528         if (PageHuge(page)) {
1529                 if (PageHead(page)) {
1530                         isolate_huge_page(page, pagelist);
1531                         err = 0;
1532                 }
1533         } else {
1534                 struct page *head;
1535
1536                 head = compound_head(page);
1537                 err = isolate_lru_page(head);
1538                 if (err)
1539                         goto out_putpage;
1540
1541                 err = 0;
1542                 list_add_tail(&head->lru, pagelist);
1543                 mod_node_page_state(page_pgdat(head),
1544                         NR_ISOLATED_ANON + page_is_file_cache(head),
1545                         hpage_nr_pages(head));
1546         }
1547 out_putpage:
1548         /*
1549          * Either remove the duplicate refcount from
1550          * isolate_lru_page() or drop the page ref if it was
1551          * not isolated.
1552          */
1553         put_page(page);
1554 out:
1555         up_read(&mm->mmap_sem);
1556         return err;
1557 }
1558
1559 /*
1560  * Migrate an array of page address onto an array of nodes and fill
1561  * the corresponding array of status.
1562  */
1563 static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
1564                          unsigned long nr_pages,
1565                          const void __user * __user *pages,
1566                          const int __user *nodes,
1567                          int __user *status, int flags)
1568 {
1569         int current_node = NUMA_NO_NODE;
1570         LIST_HEAD(pagelist);
1571         int start, i;
1572         int err = 0, err1;
1573
1574         migrate_prep();
1575
1576         for (i = start = 0; i < nr_pages; i++) {
1577                 const void __user *p;
1578                 unsigned long addr;
1579                 int node;
1580
1581                 err = -EFAULT;
1582                 if (get_user(p, pages + i))
1583                         goto out_flush;
1584                 if (get_user(node, nodes + i))
1585                         goto out_flush;
1586                 addr = (unsigned long)p;
1587
1588                 err = -ENODEV;
1589                 if (node < 0 || node >= MAX_NUMNODES)
1590                         goto out_flush;
1591                 if (!node_state(node, N_MEMORY))
1592                         goto out_flush;
1593
1594                 err = -EACCES;
1595                 if (!node_isset(node, task_nodes))
1596                         goto out_flush;
1597
1598                 if (current_node == NUMA_NO_NODE) {
1599                         current_node = node;
1600                         start = i;
1601                 } else if (node != current_node) {
1602                         err = do_move_pages_to_node(mm, &pagelist, current_node);
1603                         if (err)
1604                                 goto out;
1605                         err = store_status(status, start, current_node, i - start);
1606                         if (err)
1607                                 goto out;
1608                         start = i;
1609                         current_node = node;
1610                 }
1611
1612                 /*
1613                  * Errors in the page lookup or isolation are not fatal and we simply
1614                  * report them via status
1615                  */
1616                 err = add_page_for_migration(mm, addr, current_node,
1617                                 &pagelist, flags & MPOL_MF_MOVE_ALL);
1618                 if (!err)
1619                         continue;
1620
1621                 err = store_status(status, i, err, 1);
1622                 if (err)
1623                         goto out_flush;
1624
1625                 err = do_move_pages_to_node(mm, &pagelist, current_node);
1626                 if (err)
1627                         goto out;
1628                 if (i > start) {
1629                         err = store_status(status, start, current_node, i - start);
1630                         if (err)
1631                                 goto out;
1632                 }
1633                 current_node = NUMA_NO_NODE;
1634         }
1635 out_flush:
1636         if (list_empty(&pagelist))
1637                 return err;
1638
1639         /* Make sure we do not overwrite the existing error */
1640         err1 = do_move_pages_to_node(mm, &pagelist, current_node);
1641         if (!err1)
1642                 err1 = store_status(status, start, current_node, i - start);
1643         if (!err)
1644                 err = err1;
1645 out:
1646         return err;
1647 }
1648
1649 /*
1650  * Determine the nodes of an array of pages and store it in an array of status.
1651  */
1652 static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
1653                                 const void __user **pages, int *status)
1654 {
1655         unsigned long i;
1656
1657         down_read(&mm->mmap_sem);
1658
1659         for (i = 0; i < nr_pages; i++) {
1660                 unsigned long addr = (unsigned long)(*pages);
1661                 struct vm_area_struct *vma;
1662                 struct page *page;
1663                 int err = -EFAULT;
1664
1665                 vma = find_vma(mm, addr);
1666                 if (!vma || addr < vma->vm_start)
1667                         goto set_status;
1668
1669                 /* FOLL_DUMP to ignore special (like zero) pages */
1670                 page = follow_page(vma, addr, FOLL_DUMP);
1671
1672                 err = PTR_ERR(page);
1673                 if (IS_ERR(page))
1674                         goto set_status;
1675
1676                 err = page ? page_to_nid(page) : -ENOENT;
1677 set_status:
1678                 *status = err;
1679
1680                 pages++;
1681                 status++;
1682         }
1683
1684         up_read(&mm->mmap_sem);
1685 }
1686
1687 /*
1688  * Determine the nodes of a user array of pages and store it in
1689  * a user array of status.
1690  */
1691 static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
1692                          const void __user * __user *pages,
1693                          int __user *status)
1694 {
1695 #define DO_PAGES_STAT_CHUNK_NR 16
1696         const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
1697         int chunk_status[DO_PAGES_STAT_CHUNK_NR];
1698
1699         while (nr_pages) {
1700                 unsigned long chunk_nr;
1701
1702                 chunk_nr = nr_pages;
1703                 if (chunk_nr > DO_PAGES_STAT_CHUNK_NR)
1704                         chunk_nr = DO_PAGES_STAT_CHUNK_NR;
1705
1706                 if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages)))
1707                         break;
1708
1709                 do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
1710
1711                 if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
1712                         break;
1713
1714                 pages += chunk_nr;
1715                 status += chunk_nr;
1716                 nr_pages -= chunk_nr;
1717         }
1718         return nr_pages ? -EFAULT : 0;
1719 }
1720
1721 /*
1722  * Move a list of pages in the address space of the currently executing
1723  * process.
1724  */
1725 static int kernel_move_pages(pid_t pid, unsigned long nr_pages,
1726                              const void __user * __user *pages,
1727                              const int __user *nodes,
1728                              int __user *status, int flags)
1729 {
1730         struct task_struct *task;
1731         struct mm_struct *mm;
1732         int err;
1733         nodemask_t task_nodes;
1734
1735         /* Check flags */
1736         if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
1737                 return -EINVAL;
1738
1739         if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
1740                 return -EPERM;
1741
1742         /* Find the mm_struct */
1743         rcu_read_lock();
1744         task = pid ? find_task_by_vpid(pid) : current;
1745         if (!task) {
1746                 rcu_read_unlock();
1747                 return -ESRCH;
1748         }
1749         get_task_struct(task);
1750
1751         /*
1752          * Check if this process has the right to modify the specified
1753          * process. Use the regular "ptrace_may_access()" checks.
1754          */
1755         if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
1756                 rcu_read_unlock();
1757                 err = -EPERM;
1758                 goto out;
1759         }
1760         rcu_read_unlock();
1761
1762         err = security_task_movememory(task);
1763         if (err)
1764                 goto out;
1765
1766         task_nodes = cpuset_mems_allowed(task);
1767         mm = get_task_mm(task);
1768         put_task_struct(task);
1769
1770         if (!mm)
1771                 return -EINVAL;
1772
1773         if (nodes)
1774                 err = do_pages_move(mm, task_nodes, nr_pages, pages,
1775                                     nodes, status, flags);
1776         else
1777                 err = do_pages_stat(mm, nr_pages, pages, status);
1778
1779         mmput(mm);
1780         return err;
1781
1782 out:
1783         put_task_struct(task);
1784         return err;
1785 }
1786
1787 SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
1788                 const void __user * __user *, pages,
1789                 const int __user *, nodes,
1790                 int __user *, status, int, flags)
1791 {
1792         return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags);
1793 }
1794
1795 #ifdef CONFIG_COMPAT
1796 COMPAT_SYSCALL_DEFINE6(move_pages, pid_t, pid, compat_ulong_t, nr_pages,
1797                        compat_uptr_t __user *, pages32,
1798                        const int __user *, nodes,
1799                        int __user *, status,
1800                        int, flags)
1801 {
1802         const void __user * __user *pages;
1803         int i;
1804
1805         pages = compat_alloc_user_space(nr_pages * sizeof(void *));
1806         for (i = 0; i < nr_pages; i++) {
1807                 compat_uptr_t p;
1808
1809                 if (get_user(p, pages32 + i) ||
1810                         put_user(compat_ptr(p), pages + i))
1811                         return -EFAULT;
1812         }
1813         return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags);
1814 }
1815 #endif /* CONFIG_COMPAT */
1816
1817 #ifdef CONFIG_NUMA_BALANCING
1818 /*
1819  * Returns true if this is a safe migration target node for misplaced NUMA
1820  * pages. Currently it only checks the watermarks which crude
1821  */
1822 static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
1823                                    unsigned long nr_migrate_pages)
1824 {
1825         int z;
1826
1827         for (z = pgdat->nr_zones - 1; z >= 0; z--) {
1828                 struct zone *zone = pgdat->node_zones + z;
1829
1830                 if (!populated_zone(zone))
1831                         continue;
1832
1833                 /* Avoid waking kswapd by allocating pages_to_migrate pages. */
1834                 if (!zone_watermark_ok(zone, 0,
1835                                        high_wmark_pages(zone) +
1836                                        nr_migrate_pages,
1837                                        0, 0))
1838                         continue;
1839                 return true;
1840         }
1841         return false;
1842 }
1843
1844 static struct page *alloc_misplaced_dst_page(struct page *page,
1845                                            unsigned long data)
1846 {
1847         int nid = (int) data;
1848         struct page *newpage;
1849
1850         newpage = __alloc_pages_node(nid,
1851                                          (GFP_HIGHUSER_MOVABLE |
1852                                           __GFP_THISNODE | __GFP_NOMEMALLOC |
1853                                           __GFP_NORETRY | __GFP_NOWARN) &
1854                                          ~__GFP_RECLAIM, 0);
1855
1856         return newpage;
1857 }
1858
1859 /*
1860  * page migration rate limiting control.
1861  * Do not migrate more than @pages_to_migrate in a @migrate_interval_millisecs
1862  * window of time. Default here says do not migrate more than 1280M per second.
1863  */
1864 static unsigned int migrate_interval_millisecs __read_mostly = 100;
1865 static unsigned int ratelimit_pages __read_mostly = 128 << (20 - PAGE_SHIFT);
1866
1867 /* Returns true if the node is migrate rate-limited after the update */
1868 static bool numamigrate_update_ratelimit(pg_data_t *pgdat,
1869                                         unsigned long nr_pages)
1870 {
1871         /*
1872          * Rate-limit the amount of data that is being migrated to a node.
1873          * Optimal placement is no good if the memory bus is saturated and
1874          * all the time is being spent migrating!
1875          */
1876         if (time_after(jiffies, pgdat->numabalancing_migrate_next_window)) {
1877                 spin_lock(&pgdat->numabalancing_migrate_lock);
1878                 pgdat->numabalancing_migrate_nr_pages = 0;
1879                 pgdat->numabalancing_migrate_next_window = jiffies +
1880                         msecs_to_jiffies(migrate_interval_millisecs);
1881                 spin_unlock(&pgdat->numabalancing_migrate_lock);
1882         }
1883         if (pgdat->numabalancing_migrate_nr_pages > ratelimit_pages) {
1884                 trace_mm_numa_migrate_ratelimit(current, pgdat->node_id,
1885                                                                 nr_pages);
1886                 return true;
1887         }
1888
1889         /*
1890          * This is an unlocked non-atomic update so errors are possible.
1891          * The consequences are failing to migrate when we potentiall should
1892          * have which is not severe enough to warrant locking. If it is ever
1893          * a problem, it can be converted to a per-cpu counter.
1894          */
1895         pgdat->numabalancing_migrate_nr_pages += nr_pages;
1896         return false;
1897 }
1898
1899 static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
1900 {
1901         int page_lru;
1902
1903         VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page);
1904
1905         /* Avoid migrating to a node that is nearly full */
1906         if (!migrate_balanced_pgdat(pgdat, 1UL << compound_order(page)))
1907                 return 0;
1908
1909         if (isolate_lru_page(page))
1910                 return 0;
1911
1912         /*
1913          * migrate_misplaced_transhuge_page() skips page migration's usual
1914          * check on page_count(), so we must do it here, now that the page
1915          * has been isolated: a GUP pin, or any other pin, prevents migration.
1916          * The expected page count is 3: 1 for page's mapcount and 1 for the
1917          * caller's pin and 1 for the reference taken by isolate_lru_page().
1918          */
1919         if (PageTransHuge(page) && page_count(page) != 3) {
1920                 putback_lru_page(page);
1921                 return 0;
1922         }
1923
1924         page_lru = page_is_file_cache(page);
1925         mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_lru,
1926                                 hpage_nr_pages(page));
1927
1928         /*
1929          * Isolating the page has taken another reference, so the
1930          * caller's reference can be safely dropped without the page
1931          * disappearing underneath us during migration.
1932          */
1933         put_page(page);
1934         return 1;
1935 }
1936
1937 bool pmd_trans_migrating(pmd_t pmd)
1938 {
1939         struct page *page = pmd_page(pmd);
1940         return PageLocked(page);
1941 }
1942
1943 /*
1944  * Attempt to migrate a misplaced page to the specified destination
1945  * node. Caller is expected to have an elevated reference count on
1946  * the page that will be dropped by this function before returning.
1947  */
1948 int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
1949                            int node)
1950 {
1951         pg_data_t *pgdat = NODE_DATA(node);
1952         int isolated;
1953         int nr_remaining;
1954         LIST_HEAD(migratepages);
1955
1956         /*
1957          * Don't migrate file pages that are mapped in multiple processes
1958          * with execute permissions as they are probably shared libraries.
1959          */
1960         if (page_mapcount(page) != 1 && page_is_file_cache(page) &&
1961             (vma->vm_flags & VM_EXEC))
1962                 goto out;
1963
1964         /*
1965          * Also do not migrate dirty pages as not all filesystems can move
1966          * dirty pages in MIGRATE_ASYNC mode which is a waste of cycles.
1967          */
1968         if (page_is_file_cache(page) && PageDirty(page))
1969                 goto out;
1970
1971         /*
1972          * Rate-limit the amount of data that is being migrated to a node.
1973          * Optimal placement is no good if the memory bus is saturated and
1974          * all the time is being spent migrating!
1975          */
1976         if (numamigrate_update_ratelimit(pgdat, 1))
1977                 goto out;
1978
1979         isolated = numamigrate_isolate_page(pgdat, page);
1980         if (!isolated)
1981                 goto out;
1982
1983         list_add(&page->lru, &migratepages);
1984         nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page,
1985                                      NULL, node, MIGRATE_ASYNC,
1986                                      MR_NUMA_MISPLACED);
1987         if (nr_remaining) {
1988                 if (!list_empty(&migratepages)) {
1989                         list_del(&page->lru);
1990                         dec_node_page_state(page, NR_ISOLATED_ANON +
1991                                         page_is_file_cache(page));
1992                         putback_lru_page(page);
1993                 }
1994                 isolated = 0;
1995         } else
1996                 count_vm_numa_event(NUMA_PAGE_MIGRATE);
1997         BUG_ON(!list_empty(&migratepages));
1998         return isolated;
1999
2000 out:
2001         put_page(page);
2002         return 0;
2003 }
2004 #endif /* CONFIG_NUMA_BALANCING */
2005
2006 #if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
2007 /*
2008  * Migrates a THP to a given target node. page must be locked and is unlocked
2009  * before returning.
2010  */
2011 int migrate_misplaced_transhuge_page(struct mm_struct *mm,
2012                                 struct vm_area_struct *vma,
2013                                 pmd_t *pmd, pmd_t entry,
2014                                 unsigned long address,
2015                                 struct page *page, int node)
2016 {
2017         spinlock_t *ptl;
2018         pg_data_t *pgdat = NODE_DATA(node);
2019         int isolated = 0;
2020         struct page *new_page = NULL;
2021         int page_lru = page_is_file_cache(page);
2022         unsigned long mmun_start = address & HPAGE_PMD_MASK;
2023         unsigned long mmun_end = mmun_start + HPAGE_PMD_SIZE;
2024
2025         /*
2026          * Rate-limit the amount of data that is being migrated to a node.
2027          * Optimal placement is no good if the memory bus is saturated and
2028          * all the time is being spent migrating!
2029          */
2030         if (numamigrate_update_ratelimit(pgdat, HPAGE_PMD_NR))
2031                 goto out_dropref;
2032
2033         new_page = alloc_pages_node(node,
2034                 (GFP_TRANSHUGE_LIGHT | __GFP_THISNODE),
2035                 HPAGE_PMD_ORDER);
2036         if (!new_page)
2037                 goto out_fail;
2038         prep_transhuge_page(new_page);
2039
2040         isolated = numamigrate_isolate_page(pgdat, page);
2041         if (!isolated) {
2042                 put_page(new_page);
2043                 goto out_fail;
2044         }
2045
2046         /* Prepare a page as a migration target */
2047         __SetPageLocked(new_page);
2048         if (PageSwapBacked(page))
2049                 __SetPageSwapBacked(new_page);
2050
2051         /* anon mapping, we can simply copy page->mapping to the new page: */
2052         new_page->mapping = page->mapping;
2053         new_page->index = page->index;
2054         migrate_page_copy(new_page, page);
2055         WARN_ON(PageLRU(new_page));
2056
2057         /* Recheck the target PMD */
2058         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2059         ptl = pmd_lock(mm, pmd);
2060         if (unlikely(!pmd_same(*pmd, entry) || !page_ref_freeze(page, 2))) {
2061                 spin_unlock(ptl);
2062                 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2063
2064                 /* Reverse changes made by migrate_page_copy() */
2065                 if (TestClearPageActive(new_page))
2066                         SetPageActive(page);
2067                 if (TestClearPageUnevictable(new_page))
2068                         SetPageUnevictable(page);
2069
2070                 unlock_page(new_page);
2071                 put_page(new_page);             /* Free it */
2072
2073                 /* Retake the callers reference and putback on LRU */
2074                 get_page(page);
2075                 putback_lru_page(page);
2076                 mod_node_page_state(page_pgdat(page),
2077                          NR_ISOLATED_ANON + page_lru, -HPAGE_PMD_NR);
2078
2079                 goto out_unlock;
2080         }
2081
2082         entry = mk_huge_pmd(new_page, vma->vm_page_prot);
2083         entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
2084
2085         /*
2086          * Clear the old entry under pagetable lock and establish the new PTE.
2087          * Any parallel GUP will either observe the old page blocking on the
2088          * page lock, block on the page table lock or observe the new page.
2089          * The SetPageUptodate on the new page and page_add_new_anon_rmap
2090          * guarantee the copy is visible before the pagetable update.
2091          */
2092         flush_cache_range(vma, mmun_start, mmun_end);
2093         page_add_anon_rmap(new_page, vma, mmun_start, true);
2094         pmdp_huge_clear_flush_notify(vma, mmun_start, pmd);
2095         set_pmd_at(mm, mmun_start, pmd, entry);
2096         update_mmu_cache_pmd(vma, address, &entry);
2097
2098         page_ref_unfreeze(page, 2);
2099         mlock_migrate_page(new_page, page);
2100         page_remove_rmap(page, true);
2101         set_page_owner_migrate_reason(new_page, MR_NUMA_MISPLACED);
2102
2103         spin_unlock(ptl);
2104         /*
2105          * No need to double call mmu_notifier->invalidate_range() callback as
2106          * the above pmdp_huge_clear_flush_notify() did already call it.
2107          */
2108         mmu_notifier_invalidate_range_only_end(mm, mmun_start, mmun_end);
2109
2110         /* Take an "isolate" reference and put new page on the LRU. */
2111         get_page(new_page);
2112         putback_lru_page(new_page);
2113
2114         unlock_page(new_page);
2115         unlock_page(page);
2116         put_page(page);                 /* Drop the rmap reference */
2117         put_page(page);                 /* Drop the LRU isolation reference */
2118
2119         count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR);
2120         count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR);
2121
2122         mod_node_page_state(page_pgdat(page),
2123                         NR_ISOLATED_ANON + page_lru,
2124                         -HPAGE_PMD_NR);
2125         return isolated;
2126
2127 out_fail:
2128         count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
2129 out_dropref:
2130         ptl = pmd_lock(mm, pmd);
2131         if (pmd_same(*pmd, entry)) {
2132                 entry = pmd_modify(entry, vma->vm_page_prot);
2133                 set_pmd_at(mm, mmun_start, pmd, entry);
2134                 update_mmu_cache_pmd(vma, address, &entry);
2135         }
2136         spin_unlock(ptl);
2137
2138 out_unlock:
2139         unlock_page(page);
2140         put_page(page);
2141         return 0;
2142 }
2143 #endif /* CONFIG_NUMA_BALANCING */
2144
2145 #endif /* CONFIG_NUMA */
2146
2147 #if defined(CONFIG_MIGRATE_VMA_HELPER)
2148 struct migrate_vma {
2149         struct vm_area_struct   *vma;
2150         unsigned long           *dst;
2151         unsigned long           *src;
2152         unsigned long           cpages;
2153         unsigned long           npages;
2154         unsigned long           start;
2155         unsigned long           end;
2156 };
2157
2158 static int migrate_vma_collect_hole(unsigned long start,
2159                                     unsigned long end,
2160                                     struct mm_walk *walk)
2161 {
2162         struct migrate_vma *migrate = walk->private;
2163         unsigned long addr;
2164
2165         for (addr = start & PAGE_MASK; addr < end; addr += PAGE_SIZE) {
2166                 migrate->src[migrate->npages] = MIGRATE_PFN_MIGRATE;
2167                 migrate->dst[migrate->npages] = 0;
2168                 migrate->npages++;
2169                 migrate->cpages++;
2170         }
2171
2172         return 0;
2173 }
2174
2175 static int migrate_vma_collect_skip(unsigned long start,
2176                                     unsigned long end,
2177                                     struct mm_walk *walk)
2178 {
2179         struct migrate_vma *migrate = walk->private;
2180         unsigned long addr;
2181
2182         for (addr = start & PAGE_MASK; addr < end; addr += PAGE_SIZE) {
2183                 migrate->dst[migrate->npages] = 0;
2184                 migrate->src[migrate->npages++] = 0;
2185         }
2186
2187         return 0;
2188 }
2189
2190 static int migrate_vma_collect_pmd(pmd_t *pmdp,
2191                                    unsigned long start,
2192                                    unsigned long end,
2193                                    struct mm_walk *walk)
2194 {
2195         struct migrate_vma *migrate = walk->private;
2196         struct vm_area_struct *vma = walk->vma;
2197         struct mm_struct *mm = vma->vm_mm;
2198         unsigned long addr = start, unmapped = 0;
2199         spinlock_t *ptl;
2200         pte_t *ptep;
2201
2202 again:
2203         if (pmd_none(*pmdp))
2204                 return migrate_vma_collect_hole(start, end, walk);
2205
2206         if (pmd_trans_huge(*pmdp)) {
2207                 struct page *page;
2208
2209                 ptl = pmd_lock(mm, pmdp);
2210                 if (unlikely(!pmd_trans_huge(*pmdp))) {
2211                         spin_unlock(ptl);
2212                         goto again;
2213                 }
2214
2215                 page = pmd_page(*pmdp);
2216                 if (is_huge_zero_page(page)) {
2217                         spin_unlock(ptl);
2218                         split_huge_pmd(vma, pmdp, addr);
2219                         if (pmd_trans_unstable(pmdp))
2220                                 return migrate_vma_collect_skip(start, end,
2221                                                                 walk);
2222                 } else {
2223                         int ret;
2224
2225                         get_page(page);
2226                         spin_unlock(ptl);
2227                         if (unlikely(!trylock_page(page)))
2228                                 return migrate_vma_collect_skip(start, end,
2229                                                                 walk);
2230                         ret = split_huge_page(page);
2231                         unlock_page(page);
2232                         put_page(page);
2233                         if (ret)
2234                                 return migrate_vma_collect_skip(start, end,
2235                                                                 walk);
2236                         if (pmd_none(*pmdp))
2237                                 return migrate_vma_collect_hole(start, end,
2238                                                                 walk);
2239                 }
2240         }
2241
2242         if (unlikely(pmd_bad(*pmdp)))
2243                 return migrate_vma_collect_skip(start, end, walk);
2244
2245         ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
2246         arch_enter_lazy_mmu_mode();
2247
2248         for (; addr < end; addr += PAGE_SIZE, ptep++) {
2249                 unsigned long mpfn, pfn;
2250                 struct page *page;
2251                 swp_entry_t entry;
2252                 pte_t pte;
2253
2254                 pte = *ptep;
2255                 pfn = pte_pfn(pte);
2256
2257                 if (pte_none(pte)) {
2258                         mpfn = MIGRATE_PFN_MIGRATE;
2259                         migrate->cpages++;
2260                         pfn = 0;
2261                         goto next;
2262                 }
2263
2264                 if (!pte_present(pte)) {
2265                         mpfn = pfn = 0;
2266
2267                         /*
2268                          * Only care about unaddressable device page special
2269                          * page table entry. Other special swap entries are not
2270                          * migratable, and we ignore regular swapped page.
2271                          */
2272                         entry = pte_to_swp_entry(pte);
2273                         if (!is_device_private_entry(entry))
2274                                 goto next;
2275
2276                         page = device_private_entry_to_page(entry);
2277                         mpfn = migrate_pfn(page_to_pfn(page))|
2278                                 MIGRATE_PFN_DEVICE | MIGRATE_PFN_MIGRATE;
2279                         if (is_write_device_private_entry(entry))
2280                                 mpfn |= MIGRATE_PFN_WRITE;
2281                 } else {
2282                         if (is_zero_pfn(pfn)) {
2283                                 mpfn = MIGRATE_PFN_MIGRATE;
2284                                 migrate->cpages++;
2285                                 pfn = 0;
2286                                 goto next;
2287                         }
2288                         page = _vm_normal_page(migrate->vma, addr, pte, true);
2289                         mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
2290                         mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
2291                 }
2292
2293                 /* FIXME support THP */
2294                 if (!page || !page->mapping || PageTransCompound(page)) {
2295                         mpfn = pfn = 0;
2296                         goto next;
2297                 }
2298                 pfn = page_to_pfn(page);
2299
2300                 /*
2301                  * By getting a reference on the page we pin it and that blocks
2302                  * any kind of migration. Side effect is that it "freezes" the
2303                  * pte.
2304                  *
2305                  * We drop this reference after isolating the page from the lru
2306                  * for non device page (device page are not on the lru and thus
2307                  * can't be dropped from it).
2308                  */
2309                 get_page(page);
2310                 migrate->cpages++;
2311
2312                 /*
2313                  * Optimize for the common case where page is only mapped once
2314                  * in one process. If we can lock the page, then we can safely
2315                  * set up a special migration page table entry now.
2316                  */
2317                 if (trylock_page(page)) {
2318                         pte_t swp_pte;
2319
2320                         mpfn |= MIGRATE_PFN_LOCKED;
2321                         ptep_get_and_clear(mm, addr, ptep);
2322
2323                         /* Setup special migration page table entry */
2324                         entry = make_migration_entry(page, mpfn &
2325                                                      MIGRATE_PFN_WRITE);
2326                         swp_pte = swp_entry_to_pte(entry);
2327                         if (pte_soft_dirty(pte))
2328                                 swp_pte = pte_swp_mksoft_dirty(swp_pte);
2329                         set_pte_at(mm, addr, ptep, swp_pte);
2330
2331                         /*
2332                          * This is like regular unmap: we remove the rmap and
2333                          * drop page refcount. Page won't be freed, as we took
2334                          * a reference just above.
2335                          */
2336                         page_remove_rmap(page, false);
2337                         put_page(page);
2338
2339                         if (pte_present(pte))
2340                                 unmapped++;
2341                 }
2342
2343 next:
2344                 migrate->dst[migrate->npages] = 0;
2345                 migrate->src[migrate->npages++] = mpfn;
2346         }
2347         arch_leave_lazy_mmu_mode();
2348         pte_unmap_unlock(ptep - 1, ptl);
2349
2350         /* Only flush the TLB if we actually modified any entries */
2351         if (unmapped)
2352                 flush_tlb_range(walk->vma, start, end);
2353
2354         return 0;
2355 }
2356
2357 /*
2358  * migrate_vma_collect() - collect pages over a range of virtual addresses
2359  * @migrate: migrate struct containing all migration information
2360  *
2361  * This will walk the CPU page table. For each virtual address backed by a
2362  * valid page, it updates the src array and takes a reference on the page, in
2363  * order to pin the page until we lock it and unmap it.
2364  */
2365 static void migrate_vma_collect(struct migrate_vma *migrate)
2366 {
2367         struct mm_walk mm_walk;
2368
2369         mm_walk.pmd_entry = migrate_vma_collect_pmd;
2370         mm_walk.pte_entry = NULL;
2371         mm_walk.pte_hole = migrate_vma_collect_hole;
2372         mm_walk.hugetlb_entry = NULL;
2373         mm_walk.test_walk = NULL;
2374         mm_walk.vma = migrate->vma;
2375         mm_walk.mm = migrate->vma->vm_mm;
2376         mm_walk.private = migrate;
2377
2378         mmu_notifier_invalidate_range_start(mm_walk.mm,
2379                                             migrate->start,
2380                                             migrate->end);
2381         walk_page_range(migrate->start, migrate->end, &mm_walk);
2382         mmu_notifier_invalidate_range_end(mm_walk.mm,
2383                                           migrate->start,
2384                                           migrate->end);
2385
2386         migrate->end = migrate->start + (migrate->npages << PAGE_SHIFT);
2387 }
2388
2389 /*
2390  * migrate_vma_check_page() - check if page is pinned or not
2391  * @page: struct page to check
2392  *
2393  * Pinned pages cannot be migrated. This is the same test as in
2394  * migrate_page_move_mapping(), except that here we allow migration of a
2395  * ZONE_DEVICE page.
2396  */
2397 static bool migrate_vma_check_page(struct page *page)
2398 {
2399         /*
2400          * One extra ref because caller holds an extra reference, either from
2401          * isolate_lru_page() for a regular page, or migrate_vma_collect() for
2402          * a device page.
2403          */
2404         int extra = 1;
2405
2406         /*
2407          * FIXME support THP (transparent huge page), it is bit more complex to
2408          * check them than regular pages, because they can be mapped with a pmd
2409          * or with a pte (split pte mapping).
2410          */
2411         if (PageCompound(page))
2412                 return false;
2413
2414         /* Page from ZONE_DEVICE have one extra reference */
2415         if (is_zone_device_page(page)) {
2416                 /*
2417                  * Private page can never be pin as they have no valid pte and
2418                  * GUP will fail for those. Yet if there is a pending migration
2419                  * a thread might try to wait on the pte migration entry and
2420                  * will bump the page reference count. Sadly there is no way to
2421                  * differentiate a regular pin from migration wait. Hence to
2422                  * avoid 2 racing thread trying to migrate back to CPU to enter
2423                  * infinite loop (one stoping migration because the other is
2424                  * waiting on pte migration entry). We always return true here.
2425                  *
2426                  * FIXME proper solution is to rework migration_entry_wait() so
2427                  * it does not need to take a reference on page.
2428                  */
2429                 if (is_device_private_page(page))
2430                         return true;
2431
2432                 /*
2433                  * Only allow device public page to be migrated and account for
2434                  * the extra reference count imply by ZONE_DEVICE pages.
2435                  */
2436                 if (!is_device_public_page(page))
2437                         return false;
2438                 extra++;
2439         }
2440
2441         /* For file back page */
2442         if (page_mapping(page))
2443                 extra += 1 + page_has_private(page);
2444
2445         if ((page_count(page) - extra) > page_mapcount(page))
2446                 return false;
2447
2448         return true;
2449 }
2450
2451 /*
2452  * migrate_vma_prepare() - lock pages and isolate them from the lru
2453  * @migrate: migrate struct containing all migration information
2454  *
2455  * This locks pages that have been collected by migrate_vma_collect(). Once each
2456  * page is locked it is isolated from the lru (for non-device pages). Finally,
2457  * the ref taken by migrate_vma_collect() is dropped, as locked pages cannot be
2458  * migrated by concurrent kernel threads.
2459  */
2460 static void migrate_vma_prepare(struct migrate_vma *migrate)
2461 {
2462         const unsigned long npages = migrate->npages;
2463         const unsigned long start = migrate->start;
2464         unsigned long addr, i, restore = 0;
2465         bool allow_drain = true;
2466
2467         lru_add_drain();
2468
2469         for (i = 0; (i < npages) && migrate->cpages; i++) {
2470                 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2471                 bool remap = true;
2472
2473                 if (!page)
2474                         continue;
2475
2476                 if (!(migrate->src[i] & MIGRATE_PFN_LOCKED)) {
2477                         /*
2478                          * Because we are migrating several pages there can be
2479                          * a deadlock between 2 concurrent migration where each
2480                          * are waiting on each other page lock.
2481                          *
2482                          * Make migrate_vma() a best effort thing and backoff
2483                          * for any page we can not lock right away.
2484                          */
2485                         if (!trylock_page(page)) {
2486                                 migrate->src[i] = 0;
2487                                 migrate->cpages--;
2488                                 put_page(page);
2489                                 continue;
2490                         }
2491                         remap = false;
2492                         migrate->src[i] |= MIGRATE_PFN_LOCKED;
2493                 }
2494
2495                 /* ZONE_DEVICE pages are not on LRU */
2496                 if (!is_zone_device_page(page)) {
2497                         if (!PageLRU(page) && allow_drain) {
2498                                 /* Drain CPU's pagevec */
2499                                 lru_add_drain_all();
2500                                 allow_drain = false;
2501                         }
2502
2503                         if (isolate_lru_page(page)) {
2504                                 if (remap) {
2505                                         migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2506                                         migrate->cpages--;
2507                                         restore++;
2508                                 } else {
2509                                         migrate->src[i] = 0;
2510                                         unlock_page(page);
2511                                         migrate->cpages--;
2512                                         put_page(page);
2513                                 }
2514                                 continue;
2515                         }
2516
2517                         /* Drop the reference we took in collect */
2518                         put_page(page);
2519                 }
2520
2521                 if (!migrate_vma_check_page(page)) {
2522                         if (remap) {
2523                                 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2524                                 migrate->cpages--;
2525                                 restore++;
2526
2527                                 if (!is_zone_device_page(page)) {
2528                                         get_page(page);
2529                                         putback_lru_page(page);
2530                                 }
2531                         } else {
2532                                 migrate->src[i] = 0;
2533                                 unlock_page(page);
2534                                 migrate->cpages--;
2535
2536                                 if (!is_zone_device_page(page))
2537                                         putback_lru_page(page);
2538                                 else
2539                                         put_page(page);
2540                         }
2541                 }
2542         }
2543
2544         for (i = 0, addr = start; i < npages && restore; i++, addr += PAGE_SIZE) {
2545                 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2546
2547                 if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE))
2548                         continue;
2549
2550                 remove_migration_pte(page, migrate->vma, addr, page);
2551
2552                 migrate->src[i] = 0;
2553                 unlock_page(page);
2554                 put_page(page);
2555                 restore--;
2556         }
2557 }
2558
2559 /*
2560  * migrate_vma_unmap() - replace page mapping with special migration pte entry
2561  * @migrate: migrate struct containing all migration information
2562  *
2563  * Replace page mapping (CPU page table pte) with a special migration pte entry
2564  * and check again if it has been pinned. Pinned pages are restored because we
2565  * cannot migrate them.
2566  *
2567  * This is the last step before we call the device driver callback to allocate
2568  * destination memory and copy contents of original page over to new page.
2569  */
2570 static void migrate_vma_unmap(struct migrate_vma *migrate)
2571 {
2572         int flags = TTU_MIGRATION | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
2573         const unsigned long npages = migrate->npages;
2574         const unsigned long start = migrate->start;
2575         unsigned long addr, i, restore = 0;
2576
2577         for (i = 0; i < npages; i++) {
2578                 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2579
2580                 if (!page || !(migrate->src[i] & MIGRATE_PFN_MIGRATE))
2581                         continue;
2582
2583                 if (page_mapped(page)) {
2584                         try_to_unmap(page, flags);
2585                         if (page_mapped(page))
2586                                 goto restore;
2587                 }
2588
2589                 if (migrate_vma_check_page(page))
2590                         continue;
2591
2592 restore:
2593                 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2594                 migrate->cpages--;
2595                 restore++;
2596         }
2597
2598         for (addr = start, i = 0; i < npages && restore; addr += PAGE_SIZE, i++) {
2599                 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2600
2601                 if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE))
2602                         continue;
2603
2604                 remove_migration_ptes(page, page, false);
2605
2606                 migrate->src[i] = 0;
2607                 unlock_page(page);
2608                 restore--;
2609
2610                 if (is_zone_device_page(page))
2611                         put_page(page);
2612                 else
2613                         putback_lru_page(page);
2614         }
2615 }
2616
2617 static void migrate_vma_insert_page(struct migrate_vma *migrate,
2618                                     unsigned long addr,
2619                                     struct page *page,
2620                                     unsigned long *src,
2621                                     unsigned long *dst)
2622 {
2623         struct vm_area_struct *vma = migrate->vma;
2624         struct mm_struct *mm = vma->vm_mm;
2625         struct mem_cgroup *memcg;
2626         bool flush = false;
2627         spinlock_t *ptl;
2628         pte_t entry;
2629         pgd_t *pgdp;
2630         p4d_t *p4dp;
2631         pud_t *pudp;
2632         pmd_t *pmdp;
2633         pte_t *ptep;
2634
2635         /* Only allow populating anonymous memory */
2636         if (!vma_is_anonymous(vma))
2637                 goto abort;
2638
2639         pgdp = pgd_offset(mm, addr);
2640         p4dp = p4d_alloc(mm, pgdp, addr);
2641         if (!p4dp)
2642                 goto abort;
2643         pudp = pud_alloc(mm, p4dp, addr);
2644         if (!pudp)
2645                 goto abort;
2646         pmdp = pmd_alloc(mm, pudp, addr);
2647         if (!pmdp)
2648                 goto abort;
2649
2650         if (pmd_trans_huge(*pmdp) || pmd_devmap(*pmdp))
2651                 goto abort;
2652
2653         /*
2654          * Use pte_alloc() instead of pte_alloc_map().  We can't run
2655          * pte_offset_map() on pmds where a huge pmd might be created
2656          * from a different thread.
2657          *
2658          * pte_alloc_map() is safe to use under down_write(mmap_sem) or when
2659          * parallel threads are excluded by other means.
2660          *
2661          * Here we only have down_read(mmap_sem).
2662          */
2663         if (pte_alloc(mm, pmdp, addr))
2664                 goto abort;
2665
2666         /* See the comment in pte_alloc_one_map() */
2667         if (unlikely(pmd_trans_unstable(pmdp)))
2668                 goto abort;
2669
2670         if (unlikely(anon_vma_prepare(vma)))
2671                 goto abort;
2672         if (mem_cgroup_try_charge(page, vma->vm_mm, GFP_KERNEL, &memcg, false))
2673                 goto abort;
2674
2675         /*
2676          * The memory barrier inside __SetPageUptodate makes sure that
2677          * preceding stores to the page contents become visible before
2678          * the set_pte_at() write.
2679          */
2680         __SetPageUptodate(page);
2681
2682         if (is_zone_device_page(page)) {
2683                 if (is_device_private_page(page)) {
2684                         swp_entry_t swp_entry;
2685
2686                         swp_entry = make_device_private_entry(page, vma->vm_flags & VM_WRITE);
2687                         entry = swp_entry_to_pte(swp_entry);
2688                 } else if (is_device_public_page(page)) {
2689                         entry = pte_mkold(mk_pte(page, READ_ONCE(vma->vm_page_prot)));
2690                         if (vma->vm_flags & VM_WRITE)
2691                                 entry = pte_mkwrite(pte_mkdirty(entry));
2692                         entry = pte_mkdevmap(entry);
2693                 }
2694         } else {
2695                 entry = mk_pte(page, vma->vm_page_prot);
2696                 if (vma->vm_flags & VM_WRITE)
2697                         entry = pte_mkwrite(pte_mkdirty(entry));
2698         }
2699
2700         ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
2701
2702         if (pte_present(*ptep)) {
2703                 unsigned long pfn = pte_pfn(*ptep);
2704
2705                 if (!is_zero_pfn(pfn)) {
2706                         pte_unmap_unlock(ptep, ptl);
2707                         mem_cgroup_cancel_charge(page, memcg, false);
2708                         goto abort;
2709                 }
2710                 flush = true;
2711         } else if (!pte_none(*ptep)) {
2712                 pte_unmap_unlock(ptep, ptl);
2713                 mem_cgroup_cancel_charge(page, memcg, false);
2714                 goto abort;
2715         }
2716
2717         /*
2718          * Check for usefaultfd but do not deliver the fault. Instead,
2719          * just back off.
2720          */
2721         if (userfaultfd_missing(vma)) {
2722                 pte_unmap_unlock(ptep, ptl);
2723                 mem_cgroup_cancel_charge(page, memcg, false);
2724                 goto abort;
2725         }
2726
2727         inc_mm_counter(mm, MM_ANONPAGES);
2728         page_add_new_anon_rmap(page, vma, addr, false);
2729         mem_cgroup_commit_charge(page, memcg, false, false);
2730         if (!is_zone_device_page(page))
2731                 lru_cache_add_active_or_unevictable(page, vma);
2732         get_page(page);
2733
2734         if (flush) {
2735                 flush_cache_page(vma, addr, pte_pfn(*ptep));
2736                 ptep_clear_flush_notify(vma, addr, ptep);
2737                 set_pte_at_notify(mm, addr, ptep, entry);
2738                 update_mmu_cache(vma, addr, ptep);
2739         } else {
2740                 /* No need to invalidate - it was non-present before */
2741                 set_pte_at(mm, addr, ptep, entry);
2742                 update_mmu_cache(vma, addr, ptep);
2743         }
2744
2745         pte_unmap_unlock(ptep, ptl);
2746         *src = MIGRATE_PFN_MIGRATE;
2747         return;
2748
2749 abort:
2750         *src &= ~MIGRATE_PFN_MIGRATE;
2751 }
2752
2753 /*
2754  * migrate_vma_pages() - migrate meta-data from src page to dst page
2755  * @migrate: migrate struct containing all migration information
2756  *
2757  * This migrates struct page meta-data from source struct page to destination
2758  * struct page. This effectively finishes the migration from source page to the
2759  * destination page.
2760  */
2761 static void migrate_vma_pages(struct migrate_vma *migrate)
2762 {
2763         const unsigned long npages = migrate->npages;
2764         const unsigned long start = migrate->start;
2765         struct vm_area_struct *vma = migrate->vma;
2766         struct mm_struct *mm = vma->vm_mm;
2767         unsigned long addr, i, mmu_start;
2768         bool notified = false;
2769
2770         for (i = 0, addr = start; i < npages; addr += PAGE_SIZE, i++) {
2771                 struct page *newpage = migrate_pfn_to_page(migrate->dst[i]);
2772                 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2773                 struct address_space *mapping;
2774                 int r;
2775
2776                 if (!newpage) {
2777                         migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2778                         continue;
2779                 }
2780
2781                 if (!page) {
2782                         if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE)) {
2783                                 continue;
2784                         }
2785                         if (!notified) {
2786                                 mmu_start = addr;
2787                                 notified = true;
2788                                 mmu_notifier_invalidate_range_start(mm,
2789                                                                 mmu_start,
2790                                                                 migrate->end);
2791                         }
2792                         migrate_vma_insert_page(migrate, addr, newpage,
2793                                                 &migrate->src[i],
2794                                                 &migrate->dst[i]);
2795                         continue;
2796                 }
2797
2798                 mapping = page_mapping(page);
2799
2800                 if (is_zone_device_page(newpage)) {
2801                         if (is_device_private_page(newpage)) {
2802                                 /*
2803                                  * For now only support private anonymous when
2804                                  * migrating to un-addressable device memory.
2805                                  */
2806                                 if (mapping) {
2807                                         migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2808                                         continue;
2809                                 }
2810                         } else if (!is_device_public_page(newpage)) {
2811                                 /*
2812                                  * Other types of ZONE_DEVICE page are not
2813                                  * supported.
2814                                  */
2815                                 migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2816                                 continue;
2817                         }
2818                 }
2819
2820                 r = migrate_page(mapping, newpage, page, MIGRATE_SYNC_NO_COPY);
2821                 if (r != MIGRATEPAGE_SUCCESS)
2822                         migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
2823         }
2824
2825         /*
2826          * No need to double call mmu_notifier->invalidate_range() callback as
2827          * the above ptep_clear_flush_notify() inside migrate_vma_insert_page()
2828          * did already call it.
2829          */
2830         if (notified)
2831                 mmu_notifier_invalidate_range_only_end(mm, mmu_start,
2832                                                        migrate->end);
2833 }
2834
2835 /*
2836  * migrate_vma_finalize() - restore CPU page table entry
2837  * @migrate: migrate struct containing all migration information
2838  *
2839  * This replaces the special migration pte entry with either a mapping to the
2840  * new page if migration was successful for that page, or to the original page
2841  * otherwise.
2842  *
2843  * This also unlocks the pages and puts them back on the lru, or drops the extra
2844  * refcount, for device pages.
2845  */
2846 static void migrate_vma_finalize(struct migrate_vma *migrate)
2847 {
2848         const unsigned long npages = migrate->npages;
2849         unsigned long i;
2850
2851         for (i = 0; i < npages; i++) {
2852                 struct page *newpage = migrate_pfn_to_page(migrate->dst[i]);
2853                 struct page *page = migrate_pfn_to_page(migrate->src[i]);
2854
2855                 if (!page) {
2856                         if (newpage) {
2857                                 unlock_page(newpage);
2858                                 put_page(newpage);
2859                         }
2860                         continue;
2861                 }
2862
2863                 if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE) || !newpage) {
2864                         if (newpage) {
2865                                 unlock_page(newpage);
2866                                 put_page(newpage);
2867                         }
2868                         newpage = page;
2869                 }
2870
2871                 remove_migration_ptes(page, newpage, false);
2872                 unlock_page(page);
2873                 migrate->cpages--;
2874
2875                 if (is_zone_device_page(page))
2876                         put_page(page);
2877                 else
2878                         putback_lru_page(page);
2879
2880                 if (newpage != page) {
2881                         unlock_page(newpage);
2882                         if (is_zone_device_page(newpage))
2883                                 put_page(newpage);
2884                         else
2885                                 putback_lru_page(newpage);
2886                 }
2887         }
2888 }
2889
2890 /*
2891  * migrate_vma() - migrate a range of memory inside vma
2892  *
2893  * @ops: migration callback for allocating destination memory and copying
2894  * @vma: virtual memory area containing the range to be migrated
2895  * @start: start address of the range to migrate (inclusive)
2896  * @end: end address of the range to migrate (exclusive)
2897  * @src: array of hmm_pfn_t containing source pfns
2898  * @dst: array of hmm_pfn_t containing destination pfns
2899  * @private: pointer passed back to each of the callback
2900  * Returns: 0 on success, error code otherwise
2901  *
2902  * This function tries to migrate a range of memory virtual address range, using
2903  * callbacks to allocate and copy memory from source to destination. First it
2904  * collects all the pages backing each virtual address in the range, saving this
2905  * inside the src array. Then it locks those pages and unmaps them. Once the pages
2906  * are locked and unmapped, it checks whether each page is pinned or not. Pages
2907  * that aren't pinned have the MIGRATE_PFN_MIGRATE flag set (by this function)
2908  * in the corresponding src array entry. It then restores any pages that are
2909  * pinned, by remapping and unlocking those pages.
2910  *
2911  * At this point it calls the alloc_and_copy() callback. For documentation on
2912  * what is expected from that callback, see struct migrate_vma_ops comments in
2913  * include/linux/migrate.h
2914  *
2915  * After the alloc_and_copy() callback, this function goes over each entry in
2916  * the src array that has the MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag
2917  * set. If the corresponding entry in dst array has MIGRATE_PFN_VALID flag set,
2918  * then the function tries to migrate struct page information from the source
2919  * struct page to the destination struct page. If it fails to migrate the struct
2920  * page information, then it clears the MIGRATE_PFN_MIGRATE flag in the src
2921  * array.
2922  *
2923  * At this point all successfully migrated pages have an entry in the src
2924  * array with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag set and the dst
2925  * array entry with MIGRATE_PFN_VALID flag set.
2926  *
2927  * It then calls the finalize_and_map() callback. See comments for "struct
2928  * migrate_vma_ops", in include/linux/migrate.h for details about
2929  * finalize_and_map() behavior.
2930  *
2931  * After the finalize_and_map() callback, for successfully migrated pages, this
2932  * function updates the CPU page table to point to new pages, otherwise it
2933  * restores the CPU page table to point to the original source pages.
2934  *
2935  * Function returns 0 after the above steps, even if no pages were migrated
2936  * (The function only returns an error if any of the arguments are invalid.)
2937  *
2938  * Both src and dst array must be big enough for (end - start) >> PAGE_SHIFT
2939  * unsigned long entries.
2940  */
2941 int migrate_vma(const struct migrate_vma_ops *ops,
2942                 struct vm_area_struct *vma,
2943                 unsigned long start,
2944                 unsigned long end,
2945                 unsigned long *src,
2946                 unsigned long *dst,
2947                 void *private)
2948 {
2949         struct migrate_vma migrate;
2950
2951         /* Sanity check the arguments */
2952         start &= PAGE_MASK;
2953         end &= PAGE_MASK;
2954         if (!vma || is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL) ||
2955                         vma_is_dax(vma))
2956                 return -EINVAL;
2957         if (start < vma->vm_start || start >= vma->vm_end)
2958                 return -EINVAL;
2959         if (end <= vma->vm_start || end > vma->vm_end)
2960                 return -EINVAL;
2961         if (!ops || !src || !dst || start >= end)
2962                 return -EINVAL;
2963
2964         memset(src, 0, sizeof(*src) * ((end - start) >> PAGE_SHIFT));
2965         migrate.src = src;
2966         migrate.dst = dst;
2967         migrate.start = start;
2968         migrate.npages = 0;
2969         migrate.cpages = 0;
2970         migrate.end = end;
2971         migrate.vma = vma;
2972
2973         /* Collect, and try to unmap source pages */
2974         migrate_vma_collect(&migrate);
2975         if (!migrate.cpages)
2976                 return 0;
2977
2978         /* Lock and isolate page */
2979         migrate_vma_prepare(&migrate);
2980         if (!migrate.cpages)
2981                 return 0;
2982
2983         /* Unmap pages */
2984         migrate_vma_unmap(&migrate);
2985         if (!migrate.cpages)
2986                 return 0;
2987
2988         /*
2989          * At this point pages are locked and unmapped, and thus they have
2990          * stable content and can safely be copied to destination memory that
2991          * is allocated by the callback.
2992          *
2993          * Note that migration can fail in migrate_vma_struct_page() for each
2994          * individual page.
2995          */
2996         ops->alloc_and_copy(vma, src, dst, start, end, private);
2997
2998         /* This does the real migration of struct page */
2999         migrate_vma_pages(&migrate);
3000
3001         ops->finalize_and_map(vma, src, dst, start, end, private);
3002
3003         /* Unlock and remap pages */
3004         migrate_vma_finalize(&migrate);
3005
3006         return 0;
3007 }
3008 EXPORT_SYMBOL(migrate_vma);
3009 #endif /* defined(MIGRATE_VMA_HELPER) */