Version:  2.0.40 2.2.26 2.4.37 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10

Linux/mm/migrate.c

  1 /*
  2  * Memory Migration functionality - linux/mm/migrate.c
  3  *
  4  * Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter
  5  *
  6  * Page migration was first developed in the context of the memory hotplug
  7  * project. The main authors of the migration code are:
  8  *
  9  * IWAMOTO Toshihiro <iwamoto@valinux.co.jp>
 10  * Hirokazu Takahashi <taka@valinux.co.jp>
 11  * Dave Hansen <haveblue@us.ibm.com>
 12  * Christoph Lameter
 13  */
 14 
 15 #include <linux/migrate.h>
 16 #include <linux/export.h>
 17 #include <linux/swap.h>
 18 #include <linux/swapops.h>
 19 #include <linux/pagemap.h>
 20 #include <linux/buffer_head.h>
 21 #include <linux/mm_inline.h>
 22 #include <linux/nsproxy.h>
 23 #include <linux/pagevec.h>
 24 #include <linux/ksm.h>
 25 #include <linux/rmap.h>
 26 #include <linux/topology.h>
 27 #include <linux/cpu.h>
 28 #include <linux/cpuset.h>
 29 #include <linux/writeback.h>
 30 #include <linux/mempolicy.h>
 31 #include <linux/vmalloc.h>
 32 #include <linux/security.h>
 33 #include <linux/backing-dev.h>
 34 #include <linux/compaction.h>
 35 #include <linux/syscalls.h>
 36 #include <linux/hugetlb.h>
 37 #include <linux/hugetlb_cgroup.h>
 38 #include <linux/gfp.h>
 39 #include <linux/balloon_compaction.h>
 40 #include <linux/mmu_notifier.h>
 41 #include <linux/page_idle.h>
 42 #include <linux/page_owner.h>
 43 
 44 #include <asm/tlbflush.h>
 45 
 46 #define CREATE_TRACE_POINTS
 47 #include <trace/events/migrate.h>
 48 
 49 #include "internal.h"
 50 
 51 /*
 52  * migrate_prep() needs to be called before we start compiling a list of pages
 53  * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
 54  * undesirable, use migrate_prep_local()
 55  */
 56 int migrate_prep(void)
 57 {
 58         /*
 59          * Clear the LRU lists so pages can be isolated.
 60          * Note that pages may be moved off the LRU after we have
 61          * drained them. Those pages will fail to migrate like other
 62          * pages that may be busy.
 63          */
 64         lru_add_drain_all();
 65 
 66         return 0;
 67 }
 68 
 69 /* Do the necessary work of migrate_prep but not if it involves other CPUs */
 70 int migrate_prep_local(void)
 71 {
 72         lru_add_drain();
 73 
 74         return 0;
 75 }
 76 
 77 bool isolate_movable_page(struct page *page, isolate_mode_t mode)
 78 {
 79         struct address_space *mapping;
 80 
 81         /*
 82          * Avoid burning cycles with pages that are yet under __free_pages(),
 83          * or just got freed under us.
 84          *
 85          * In case we 'win' a race for a movable page being freed under us and
 86          * raise its refcount preventing __free_pages() from doing its job
 87          * the put_page() at the end of this block will take care of
 88          * release this page, thus avoiding a nasty leakage.
 89          */
 90         if (unlikely(!get_page_unless_zero(page)))
 91                 goto out;
 92 
 93         /*
 94          * Check PageMovable before holding a PG_lock because page's owner
 95          * assumes anybody doesn't touch PG_lock of newly allocated page
 96          * so unconditionally grapping the lock ruins page's owner side.
 97          */
 98         if (unlikely(!__PageMovable(page)))
 99                 goto out_putpage;
100         /*
101          * As movable pages are not isolated from LRU lists, concurrent
102          * compaction threads can race against page migration functions
103          * as well as race against the releasing a page.
104          *
105          * In order to avoid having an already isolated movable page
106          * being (wrongly) re-isolated while it is under migration,
107          * or to avoid attempting to isolate pages being released,
108          * lets be sure we have the page lock
109          * before proceeding with the movable page isolation steps.
110          */
111         if (unlikely(!trylock_page(page)))
112                 goto out_putpage;
113 
114         if (!PageMovable(page) || PageIsolated(page))
115                 goto out_no_isolated;
116 
117         mapping = page_mapping(page);
118         VM_BUG_ON_PAGE(!mapping, page);
119 
120         if (!mapping->a_ops->isolate_page(page, mode))
121                 goto out_no_isolated;
122 
123         /* Driver shouldn't use PG_isolated bit of page->flags */
124         WARN_ON_ONCE(PageIsolated(page));
125         __SetPageIsolated(page);
126         unlock_page(page);
127 
128         return true;
129 
130 out_no_isolated:
131         unlock_page(page);
132 out_putpage:
133         put_page(page);
134 out:
135         return false;
136 }
137 
138 /* It should be called on page which is PG_movable */
139 void putback_movable_page(struct page *page)
140 {
141         struct address_space *mapping;
142 
143         VM_BUG_ON_PAGE(!PageLocked(page), page);
144         VM_BUG_ON_PAGE(!PageMovable(page), page);
145         VM_BUG_ON_PAGE(!PageIsolated(page), page);
146 
147         mapping = page_mapping(page);
148         mapping->a_ops->putback_page(page);
149         __ClearPageIsolated(page);
150 }
151 
152 /*
153  * Put previously isolated pages back onto the appropriate lists
154  * from where they were once taken off for compaction/migration.
155  *
156  * This function shall be used whenever the isolated pageset has been
157  * built from lru, balloon, hugetlbfs page. See isolate_migratepages_range()
158  * and isolate_huge_page().
159  */
160 void putback_movable_pages(struct list_head *l)
161 {
162         struct page *page;
163         struct page *page2;
164 
165         list_for_each_entry_safe(page, page2, l, lru) {
166                 if (unlikely(PageHuge(page))) {
167                         putback_active_hugepage(page);
168                         continue;
169                 }
170                 list_del(&page->lru);
171                 /*
172                  * We isolated non-lru movable page so here we can use
173                  * __PageMovable because LRU page's mapping cannot have
174                  * PAGE_MAPPING_MOVABLE.
175                  */
176                 if (unlikely(__PageMovable(page))) {
177                         VM_BUG_ON_PAGE(!PageIsolated(page), page);
178                         lock_page(page);
179                         if (PageMovable(page))
180                                 putback_movable_page(page);
181                         else
182                                 __ClearPageIsolated(page);
183                         unlock_page(page);
184                         put_page(page);
185                 } else {
186                         putback_lru_page(page);
187                         dec_node_page_state(page, NR_ISOLATED_ANON +
188                                         page_is_file_cache(page));
189                 }
190         }
191 }
192 
193 /*
194  * Restore a potential migration pte to a working pte entry
195  */
196 static int remove_migration_pte(struct page *new, struct vm_area_struct *vma,
197                                  unsigned long addr, void *old)
198 {
199         struct mm_struct *mm = vma->vm_mm;
200         swp_entry_t entry;
201         pmd_t *pmd;
202         pte_t *ptep, pte;
203         spinlock_t *ptl;
204 
205         if (unlikely(PageHuge(new))) {
206                 ptep = huge_pte_offset(mm, addr);
207                 if (!ptep)
208                         goto out;
209                 ptl = huge_pte_lockptr(hstate_vma(vma), mm, ptep);
210         } else {
211                 pmd = mm_find_pmd(mm, addr);
212                 if (!pmd)
213                         goto out;
214 
215                 ptep = pte_offset_map(pmd, addr);
216 
217                 /*
218                  * Peek to check is_swap_pte() before taking ptlock?  No, we
219                  * can race mremap's move_ptes(), which skips anon_vma lock.
220                  */
221 
222                 ptl = pte_lockptr(mm, pmd);
223         }
224 
225         spin_lock(ptl);
226         pte = *ptep;
227         if (!is_swap_pte(pte))
228                 goto unlock;
229 
230         entry = pte_to_swp_entry(pte);
231 
232         if (!is_migration_entry(entry) ||
233             migration_entry_to_page(entry) != old)
234                 goto unlock;
235 
236         get_page(new);
237         pte = pte_mkold(mk_pte(new, READ_ONCE(vma->vm_page_prot)));
238         if (pte_swp_soft_dirty(*ptep))
239                 pte = pte_mksoft_dirty(pte);
240 
241         /* Recheck VMA as permissions can change since migration started  */
242         if (is_write_migration_entry(entry))
243                 pte = maybe_mkwrite(pte, vma);
244 
245 #ifdef CONFIG_HUGETLB_PAGE
246         if (PageHuge(new)) {
247                 pte = pte_mkhuge(pte);
248                 pte = arch_make_huge_pte(pte, vma, new, 0);
249         }
250 #endif
251         flush_dcache_page(new);
252         set_pte_at(mm, addr, ptep, pte);
253 
254         if (PageHuge(new)) {
255                 if (PageAnon(new))
256                         hugepage_add_anon_rmap(new, vma, addr);
257                 else
258                         page_dup_rmap(new, true);
259         } else if (PageAnon(new))
260                 page_add_anon_rmap(new, vma, addr, false);
261         else
262                 page_add_file_rmap(new, false);
263 
264         if (vma->vm_flags & VM_LOCKED && !PageTransCompound(new))
265                 mlock_vma_page(new);
266 
267         /* No need to invalidate - it was non-present before */
268         update_mmu_cache(vma, addr, ptep);
269 unlock:
270         pte_unmap_unlock(ptep, ptl);
271 out:
272         return SWAP_AGAIN;
273 }
274 
275 /*
276  * Get rid of all migration entries and replace them by
277  * references to the indicated page.
278  */
279 void remove_migration_ptes(struct page *old, struct page *new, bool locked)
280 {
281         struct rmap_walk_control rwc = {
282                 .rmap_one = remove_migration_pte,
283                 .arg = old,
284         };
285 
286         if (locked)
287                 rmap_walk_locked(new, &rwc);
288         else
289                 rmap_walk(new, &rwc);
290 }
291 
292 /*
293  * Something used the pte of a page under migration. We need to
294  * get to the page and wait until migration is finished.
295  * When we return from this function the fault will be retried.
296  */
297 void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
298                                 spinlock_t *ptl)
299 {
300         pte_t pte;
301         swp_entry_t entry;
302         struct page *page;
303 
304         spin_lock(ptl);
305         pte = *ptep;
306         if (!is_swap_pte(pte))
307                 goto out;
308 
309         entry = pte_to_swp_entry(pte);
310         if (!is_migration_entry(entry))
311                 goto out;
312 
313         page = migration_entry_to_page(entry);
314 
315         /*
316          * Once radix-tree replacement of page migration started, page_count
317          * *must* be zero. And, we don't want to call wait_on_page_locked()
318          * against a page without get_page().
319          * So, we use get_page_unless_zero(), here. Even failed, page fault
320          * will occur again.
321          */
322         if (!get_page_unless_zero(page))
323                 goto out;
324         pte_unmap_unlock(ptep, ptl);
325         wait_on_page_locked(page);
326         put_page(page);
327         return;
328 out:
329         pte_unmap_unlock(ptep, ptl);
330 }
331 
332 void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
333                                 unsigned long address)
334 {
335         spinlock_t *ptl = pte_lockptr(mm, pmd);
336         pte_t *ptep = pte_offset_map(pmd, address);
337         __migration_entry_wait(mm, ptep, ptl);
338 }
339 
340 void migration_entry_wait_huge(struct vm_area_struct *vma,
341                 struct mm_struct *mm, pte_t *pte)
342 {
343         spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), mm, pte);
344         __migration_entry_wait(mm, pte, ptl);
345 }
346 
347 #ifdef CONFIG_BLOCK
348 /* Returns true if all buffers are successfully locked */
349 static bool buffer_migrate_lock_buffers(struct buffer_head *head,
350                                                         enum migrate_mode mode)
351 {
352         struct buffer_head *bh = head;
353 
354         /* Simple case, sync compaction */
355         if (mode != MIGRATE_ASYNC) {
356                 do {
357                         get_bh(bh);
358                         lock_buffer(bh);
359                         bh = bh->b_this_page;
360 
361                 } while (bh != head);
362 
363                 return true;
364         }
365 
366         /* async case, we cannot block on lock_buffer so use trylock_buffer */
367         do {
368                 get_bh(bh);
369                 if (!trylock_buffer(bh)) {
370                         /*
371                          * We failed to lock the buffer and cannot stall in
372                          * async migration. Release the taken locks
373                          */
374                         struct buffer_head *failed_bh = bh;
375                         put_bh(failed_bh);
376                         bh = head;
377                         while (bh != failed_bh) {
378                                 unlock_buffer(bh);
379                                 put_bh(bh);
380                                 bh = bh->b_this_page;
381                         }
382                         return false;
383                 }
384 
385                 bh = bh->b_this_page;
386         } while (bh != head);
387         return true;
388 }
389 #else
390 static inline bool buffer_migrate_lock_buffers(struct buffer_head *head,
391                                                         enum migrate_mode mode)
392 {
393         return true;
394 }
395 #endif /* CONFIG_BLOCK */
396 
397 /*
398  * Replace the page in the mapping.
399  *
400  * The number of remaining references must be:
401  * 1 for anonymous pages without a mapping
402  * 2 for pages with a mapping
403  * 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
404  */
405 int migrate_page_move_mapping(struct address_space *mapping,
406                 struct page *newpage, struct page *page,
407                 struct buffer_head *head, enum migrate_mode mode,
408                 int extra_count)
409 {
410         struct zone *oldzone, *newzone;
411         int dirty;
412         int expected_count = 1 + extra_count;
413         void **pslot;
414 
415         if (!mapping) {
416                 /* Anonymous page without mapping */
417                 if (page_count(page) != expected_count)
418                         return -EAGAIN;
419 
420                 /* No turning back from here */
421                 newpage->index = page->index;
422                 newpage->mapping = page->mapping;
423                 if (PageSwapBacked(page))
424                         __SetPageSwapBacked(newpage);
425 
426                 return MIGRATEPAGE_SUCCESS;
427         }
428 
429         oldzone = page_zone(page);
430         newzone = page_zone(newpage);
431 
432         spin_lock_irq(&mapping->tree_lock);
433 
434         pslot = radix_tree_lookup_slot(&mapping->page_tree,
435                                         page_index(page));
436 
437         expected_count += 1 + page_has_private(page);
438         if (page_count(page) != expected_count ||
439                 radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {
440                 spin_unlock_irq(&mapping->tree_lock);
441                 return -EAGAIN;
442         }
443 
444         if (!page_ref_freeze(page, expected_count)) {
445                 spin_unlock_irq(&mapping->tree_lock);
446                 return -EAGAIN;
447         }
448 
449         /*
450          * In the async migration case of moving a page with buffers, lock the
451          * buffers using trylock before the mapping is moved. If the mapping
452          * was moved, we later failed to lock the buffers and could not move
453          * the mapping back due to an elevated page count, we would have to
454          * block waiting on other references to be dropped.
455          */
456         if (mode == MIGRATE_ASYNC && head &&
457                         !buffer_migrate_lock_buffers(head, mode)) {
458                 page_ref_unfreeze(page, expected_count);
459                 spin_unlock_irq(&mapping->tree_lock);
460                 return -EAGAIN;
461         }
462 
463         /*
464          * Now we know that no one else is looking at the page:
465          * no turning back from here.
466          */
467         newpage->index = page->index;
468         newpage->mapping = page->mapping;
469         get_page(newpage);      /* add cache reference */
470         if (PageSwapBacked(page)) {
471                 __SetPageSwapBacked(newpage);
472                 if (PageSwapCache(page)) {
473                         SetPageSwapCache(newpage);
474                         set_page_private(newpage, page_private(page));
475                 }
476         } else {
477                 VM_BUG_ON_PAGE(PageSwapCache(page), page);
478         }
479 
480         /* Move dirty while page refs frozen and newpage not yet exposed */
481         dirty = PageDirty(page);
482         if (dirty) {
483                 ClearPageDirty(page);
484                 SetPageDirty(newpage);
485         }
486 
487         radix_tree_replace_slot(&mapping->page_tree, pslot, newpage);
488 
489         /*
490          * Drop cache reference from old page by unfreezing
491          * to one less reference.
492          * We know this isn't the last reference.
493          */
494         page_ref_unfreeze(page, expected_count - 1);
495 
496         spin_unlock(&mapping->tree_lock);
497         /* Leave irq disabled to prevent preemption while updating stats */
498 
499         /*
500          * If moved to a different zone then also account
501          * the page for that zone. Other VM counters will be
502          * taken care of when we establish references to the
503          * new page and drop references to the old page.
504          *
505          * Note that anonymous pages are accounted for
506          * via NR_FILE_PAGES and NR_ANON_MAPPED if they
507          * are mapped to swap space.
508          */
509         if (newzone != oldzone) {
510                 __dec_node_state(oldzone->zone_pgdat, NR_FILE_PAGES);
511                 __inc_node_state(newzone->zone_pgdat, NR_FILE_PAGES);
512                 if (PageSwapBacked(page) && !PageSwapCache(page)) {
513                         __dec_node_state(oldzone->zone_pgdat, NR_SHMEM);
514                         __inc_node_state(newzone->zone_pgdat, NR_SHMEM);
515                 }
516                 if (dirty && mapping_cap_account_dirty(mapping)) {
517                         __dec_node_state(oldzone->zone_pgdat, NR_FILE_DIRTY);
518                         __dec_zone_state(oldzone, NR_ZONE_WRITE_PENDING);
519                         __inc_node_state(newzone->zone_pgdat, NR_FILE_DIRTY);
520                         __inc_zone_state(newzone, NR_ZONE_WRITE_PENDING);
521                 }
522         }
523         local_irq_enable();
524 
525         return MIGRATEPAGE_SUCCESS;
526 }
527 EXPORT_SYMBOL(migrate_page_move_mapping);
528 
529 /*
530  * The expected number of remaining references is the same as that
531  * of migrate_page_move_mapping().
532  */
533 int migrate_huge_page_move_mapping(struct address_space *mapping,
534                                    struct page *newpage, struct page *page)
535 {
536         int expected_count;
537         void **pslot;
538 
539         spin_lock_irq(&mapping->tree_lock);
540 
541         pslot = radix_tree_lookup_slot(&mapping->page_tree,
542                                         page_index(page));
543 
544         expected_count = 2 + page_has_private(page);
545         if (page_count(page) != expected_count ||
546                 radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {
547                 spin_unlock_irq(&mapping->tree_lock);
548                 return -EAGAIN;
549         }
550 
551         if (!page_ref_freeze(page, expected_count)) {
552                 spin_unlock_irq(&mapping->tree_lock);
553                 return -EAGAIN;
554         }
555 
556         newpage->index = page->index;
557         newpage->mapping = page->mapping;
558 
559         get_page(newpage);
560 
561         radix_tree_replace_slot(&mapping->page_tree, pslot, newpage);
562 
563         page_ref_unfreeze(page, expected_count - 1);
564 
565         spin_unlock_irq(&mapping->tree_lock);
566 
567         return MIGRATEPAGE_SUCCESS;
568 }
569 
570 /*
571  * Gigantic pages are so large that we do not guarantee that page++ pointer
572  * arithmetic will work across the entire page.  We need something more
573  * specialized.
574  */
575 static void __copy_gigantic_page(struct page *dst, struct page *src,
576                                 int nr_pages)
577 {
578         int i;
579         struct page *dst_base = dst;
580         struct page *src_base = src;
581 
582         for (i = 0; i < nr_pages; ) {
583                 cond_resched();
584                 copy_highpage(dst, src);
585 
586                 i++;
587                 dst = mem_map_next(dst, dst_base, i);
588                 src = mem_map_next(src, src_base, i);
589         }
590 }
591 
592 static void copy_huge_page(struct page *dst, struct page *src)
593 {
594         int i;
595         int nr_pages;
596 
597         if (PageHuge(src)) {
598                 /* hugetlbfs page */
599                 struct hstate *h = page_hstate(src);
600                 nr_pages = pages_per_huge_page(h);
601 
602                 if (unlikely(nr_pages > MAX_ORDER_NR_PAGES)) {
603                         __copy_gigantic_page(dst, src, nr_pages);
604                         return;
605                 }
606         } else {
607                 /* thp page */
608                 BUG_ON(!PageTransHuge(src));
609                 nr_pages = hpage_nr_pages(src);
610         }
611 
612         for (i = 0; i < nr_pages; i++) {
613                 cond_resched();
614                 copy_highpage(dst + i, src + i);
615         }
616 }
617 
618 /*
619  * Copy the page to its new location
620  */
621 void migrate_page_copy(struct page *newpage, struct page *page)
622 {
623         int cpupid;
624 
625         if (PageHuge(page) || PageTransHuge(page))
626                 copy_huge_page(newpage, page);
627         else
628                 copy_highpage(newpage, page);
629 
630         if (PageError(page))
631                 SetPageError(newpage);
632         if (PageReferenced(page))
633                 SetPageReferenced(newpage);
634         if (PageUptodate(page))
635                 SetPageUptodate(newpage);
636         if (TestClearPageActive(page)) {
637                 VM_BUG_ON_PAGE(PageUnevictable(page), page);
638                 SetPageActive(newpage);
639         } else if (TestClearPageUnevictable(page))
640                 SetPageUnevictable(newpage);
641         if (PageChecked(page))
642                 SetPageChecked(newpage);
643         if (PageMappedToDisk(page))
644                 SetPageMappedToDisk(newpage);
645 
646         /* Move dirty on pages not done by migrate_page_move_mapping() */
647         if (PageDirty(page))
648                 SetPageDirty(newpage);
649 
650         if (page_is_young(page))
651                 set_page_young(newpage);
652         if (page_is_idle(page))
653                 set_page_idle(newpage);
654 
655         /*
656          * Copy NUMA information to the new page, to prevent over-eager
657          * future migrations of this same page.
658          */
659         cpupid = page_cpupid_xchg_last(page, -1);
660         page_cpupid_xchg_last(newpage, cpupid);
661 
662         ksm_migrate_page(newpage, page);
663         /*
664          * Please do not reorder this without considering how mm/ksm.c's
665          * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
666          */
667         if (PageSwapCache(page))
668                 ClearPageSwapCache(page);
669         ClearPagePrivate(page);
670         set_page_private(page, 0);
671 
672         /*
673          * If any waiters have accumulated on the new page then
674          * wake them up.
675          */
676         if (PageWriteback(newpage))
677                 end_page_writeback(newpage);
678 
679         copy_page_owner(page, newpage);
680 
681         mem_cgroup_migrate(page, newpage);
682 }
683 EXPORT_SYMBOL(migrate_page_copy);
684 
685 /************************************************************
686  *                    Migration functions
687  ***********************************************************/
688 
689 /*
690  * Common logic to directly migrate a single LRU page suitable for
691  * pages that do not use PagePrivate/PagePrivate2.
692  *
693  * Pages are locked upon entry and exit.
694  */
695 int migrate_page(struct address_space *mapping,
696                 struct page *newpage, struct page *page,
697                 enum migrate_mode mode)
698 {
699         int rc;
700 
701         BUG_ON(PageWriteback(page));    /* Writeback must be complete */
702 
703         rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode, 0);
704 
705         if (rc != MIGRATEPAGE_SUCCESS)
706                 return rc;
707 
708         migrate_page_copy(newpage, page);
709         return MIGRATEPAGE_SUCCESS;
710 }
711 EXPORT_SYMBOL(migrate_page);
712 
713 #ifdef CONFIG_BLOCK
714 /*
715  * Migration function for pages with buffers. This function can only be used
716  * if the underlying filesystem guarantees that no other references to "page"
717  * exist.
718  */
719 int buffer_migrate_page(struct address_space *mapping,
720                 struct page *newpage, struct page *page, enum migrate_mode mode)
721 {
722         struct buffer_head *bh, *head;
723         int rc;
724 
725         if (!page_has_buffers(page))
726                 return migrate_page(mapping, newpage, page, mode);
727 
728         head = page_buffers(page);
729 
730         rc = migrate_page_move_mapping(mapping, newpage, page, head, mode, 0);
731 
732         if (rc != MIGRATEPAGE_SUCCESS)
733                 return rc;
734 
735         /*
736          * In the async case, migrate_page_move_mapping locked the buffers
737          * with an IRQ-safe spinlock held. In the sync case, the buffers
738          * need to be locked now
739          */
740         if (mode != MIGRATE_ASYNC)
741                 BUG_ON(!buffer_migrate_lock_buffers(head, mode));
742 
743         ClearPagePrivate(page);
744         set_page_private(newpage, page_private(page));
745         set_page_private(page, 0);
746         put_page(page);
747         get_page(newpage);
748 
749         bh = head;
750         do {
751                 set_bh_page(bh, newpage, bh_offset(bh));
752                 bh = bh->b_this_page;
753 
754         } while (bh != head);
755 
756         SetPagePrivate(newpage);
757 
758         migrate_page_copy(newpage, page);
759 
760         bh = head;
761         do {
762                 unlock_buffer(bh);
763                 put_bh(bh);
764                 bh = bh->b_this_page;
765 
766         } while (bh != head);
767 
768         return MIGRATEPAGE_SUCCESS;
769 }
770 EXPORT_SYMBOL(buffer_migrate_page);
771 #endif
772 
773 /*
774  * Writeback a page to clean the dirty state
775  */
776 static int writeout(struct address_space *mapping, struct page *page)
777 {
778         struct writeback_control wbc = {
779                 .sync_mode = WB_SYNC_NONE,
780                 .nr_to_write = 1,
781                 .range_start = 0,
782                 .range_end = LLONG_MAX,
783                 .for_reclaim = 1
784         };
785         int rc;
786 
787         if (!mapping->a_ops->writepage)
788                 /* No write method for the address space */
789                 return -EINVAL;
790 
791         if (!clear_page_dirty_for_io(page))
792                 /* Someone else already triggered a write */
793                 return -EAGAIN;
794 
795         /*
796          * A dirty page may imply that the underlying filesystem has
797          * the page on some queue. So the page must be clean for
798          * migration. Writeout may mean we loose the lock and the
799          * page state is no longer what we checked for earlier.
800          * At this point we know that the migration attempt cannot
801          * be successful.
802          */
803         remove_migration_ptes(page, page, false);
804 
805         rc = mapping->a_ops->writepage(page, &wbc);
806 
807         if (rc != AOP_WRITEPAGE_ACTIVATE)
808                 /* unlocked. Relock */
809                 lock_page(page);
810 
811         return (rc < 0) ? -EIO : -EAGAIN;
812 }
813 
814 /*
815  * Default handling if a filesystem does not provide a migration function.
816  */
817 static int fallback_migrate_page(struct address_space *mapping,
818         struct page *newpage, struct page *page, enum migrate_mode mode)
819 {
820         if (PageDirty(page)) {
821                 /* Only writeback pages in full synchronous migration */
822                 if (mode != MIGRATE_SYNC)
823                         return -EBUSY;
824                 return writeout(mapping, page);
825         }
826 
827         /*
828          * Buffers may be managed in a filesystem specific way.
829          * We must have no buffers or drop them.
830          */
831         if (page_has_private(page) &&
832             !try_to_release_page(page, GFP_KERNEL))
833                 return -EAGAIN;
834 
835         return migrate_page(mapping, newpage, page, mode);
836 }
837 
838 /*
839  * Move a page to a newly allocated page
840  * The page is locked and all ptes have been successfully removed.
841  *
842  * The new page will have replaced the old page if this function
843  * is successful.
844  *
845  * Return value:
846  *   < 0 - error code
847  *  MIGRATEPAGE_SUCCESS - success
848  */
849 static int move_to_new_page(struct page *newpage, struct page *page,
850                                 enum migrate_mode mode)
851 {
852         struct address_space *mapping;
853         int rc = -EAGAIN;
854         bool is_lru = !__PageMovable(page);
855 
856         VM_BUG_ON_PAGE(!PageLocked(page), page);
857         VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
858 
859         mapping = page_mapping(page);
860 
861         if (likely(is_lru)) {
862                 if (!mapping)
863                         rc = migrate_page(mapping, newpage, page, mode);
864                 else if (mapping->a_ops->migratepage)
865                         /*
866                          * Most pages have a mapping and most filesystems
867                          * provide a migratepage callback. Anonymous pages
868                          * are part of swap space which also has its own
869                          * migratepage callback. This is the most common path
870                          * for page migration.
871                          */
872                         rc = mapping->a_ops->migratepage(mapping, newpage,
873                                                         page, mode);
874                 else
875                         rc = fallback_migrate_page(mapping, newpage,
876                                                         page, mode);
877         } else {
878                 /*
879                  * In case of non-lru page, it could be released after
880                  * isolation step. In that case, we shouldn't try migration.
881                  */
882                 VM_BUG_ON_PAGE(!PageIsolated(page), page);
883                 if (!PageMovable(page)) {
884                         rc = MIGRATEPAGE_SUCCESS;
885                         __ClearPageIsolated(page);
886                         goto out;
887                 }
888 
889                 rc = mapping->a_ops->migratepage(mapping, newpage,
890                                                 page, mode);
891                 WARN_ON_ONCE(rc == MIGRATEPAGE_SUCCESS &&
892                         !PageIsolated(page));
893         }
894 
895         /*
896          * When successful, old pagecache page->mapping must be cleared before
897          * page is freed; but stats require that PageAnon be left as PageAnon.
898          */
899         if (rc == MIGRATEPAGE_SUCCESS) {
900                 if (__PageMovable(page)) {
901                         VM_BUG_ON_PAGE(!PageIsolated(page), page);
902 
903                         /*
904                          * We clear PG_movable under page_lock so any compactor
905                          * cannot try to migrate this page.
906                          */
907                         __ClearPageIsolated(page);
908                 }
909 
910                 /*
911                  * Anonymous and movable page->mapping will be cleard by
912                  * free_pages_prepare so don't reset it here for keeping
913                  * the type to work PageAnon, for example.
914                  */
915                 if (!PageMappingFlags(page))
916                         page->mapping = NULL;
917         }
918 out:
919         return rc;
920 }
921 
922 static int __unmap_and_move(struct page *page, struct page *newpage,
923                                 int force, enum migrate_mode mode)
924 {
925         int rc = -EAGAIN;
926         int page_was_mapped = 0;
927         struct anon_vma *anon_vma = NULL;
928         bool is_lru = !__PageMovable(page);
929 
930         if (!trylock_page(page)) {
931                 if (!force || mode == MIGRATE_ASYNC)
932                         goto out;
933 
934                 /*
935                  * It's not safe for direct compaction to call lock_page.
936                  * For example, during page readahead pages are added locked
937                  * to the LRU. Later, when the IO completes the pages are
938                  * marked uptodate and unlocked. However, the queueing
939                  * could be merging multiple pages for one bio (e.g.
940                  * mpage_readpages). If an allocation happens for the
941                  * second or third page, the process can end up locking
942                  * the same page twice and deadlocking. Rather than
943                  * trying to be clever about what pages can be locked,
944                  * avoid the use of lock_page for direct compaction
945                  * altogether.
946                  */
947                 if (current->flags & PF_MEMALLOC)
948                         goto out;
949 
950                 lock_page(page);
951         }
952 
953         if (PageWriteback(page)) {
954                 /*
955                  * Only in the case of a full synchronous migration is it
956                  * necessary to wait for PageWriteback. In the async case,
957                  * the retry loop is too short and in the sync-light case,
958                  * the overhead of stalling is too much
959                  */
960                 if (mode != MIGRATE_SYNC) {
961                         rc = -EBUSY;
962                         goto out_unlock;
963                 }
964                 if (!force)
965                         goto out_unlock;
966                 wait_on_page_writeback(page);
967         }
968 
969         /*
970          * By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
971          * we cannot notice that anon_vma is freed while we migrates a page.
972          * This get_anon_vma() delays freeing anon_vma pointer until the end
973          * of migration. File cache pages are no problem because of page_lock()
974          * File Caches may use write_page() or lock_page() in migration, then,
975          * just care Anon page here.
976          *
977          * Only page_get_anon_vma() understands the subtleties of
978          * getting a hold on an anon_vma from outside one of its mms.
979          * But if we cannot get anon_vma, then we won't need it anyway,
980          * because that implies that the anon page is no longer mapped
981          * (and cannot be remapped so long as we hold the page lock).
982          */
983         if (PageAnon(page) && !PageKsm(page))
984                 anon_vma = page_get_anon_vma(page);
985 
986         /*
987          * Block others from accessing the new page when we get around to
988          * establishing additional references. We are usually the only one
989          * holding a reference to newpage at this point. We used to have a BUG
990          * here if trylock_page(newpage) fails, but would like to allow for
991          * cases where there might be a race with the previous use of newpage.
992          * This is much like races on refcount of oldpage: just don't BUG().
993          */
994         if (unlikely(!trylock_page(newpage)))
995                 goto out_unlock;
996 
997         if (unlikely(!is_lru)) {
998                 rc = move_to_new_page(newpage, page, mode);
999                 goto out_unlock_both;
1000         }
1001 
1002         /*
1003          * Corner case handling:
1004          * 1. When a new swap-cache page is read into, it is added to the LRU
1005          * and treated as swapcache but it has no rmap yet.
1006          * Calling try_to_unmap() against a page->mapping==NULL page will
1007          * trigger a BUG.  So handle it here.
1008          * 2. An orphaned page (see truncate_complete_page) might have
1009          * fs-private metadata. The page can be picked up due to memory
1010          * offlining.  Everywhere else except page reclaim, the page is
1011          * invisible to the vm, so the page can not be migrated.  So try to
1012          * free the metadata, so the page can be freed.
1013          */
1014         if (!page->mapping) {
1015                 VM_BUG_ON_PAGE(PageAnon(page), page);
1016                 if (page_has_private(page)) {
1017                         try_to_free_buffers(page);
1018                         goto out_unlock_both;
1019                 }
1020         } else if (page_mapped(page)) {
1021                 /* Establish migration ptes */
1022                 VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma,
1023                                 page);
1024                 try_to_unmap(page,
1025                         TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
1026                 page_was_mapped = 1;
1027         }
1028 
1029         if (!page_mapped(page))
1030                 rc = move_to_new_page(newpage, page, mode);
1031 
1032         if (page_was_mapped)
1033                 remove_migration_ptes(page,
1034                         rc == MIGRATEPAGE_SUCCESS ? newpage : page, false);
1035 
1036 out_unlock_both:
1037         unlock_page(newpage);
1038 out_unlock:
1039         /* Drop an anon_vma reference if we took one */
1040         if (anon_vma)
1041                 put_anon_vma(anon_vma);
1042         unlock_page(page);
1043 out:
1044         /*
1045          * If migration is successful, decrease refcount of the newpage
1046          * which will not free the page because new page owner increased
1047          * refcounter. As well, if it is LRU page, add the page to LRU
1048          * list in here.
1049          */
1050         if (rc == MIGRATEPAGE_SUCCESS) {
1051                 if (unlikely(__PageMovable(newpage)))
1052                         put_page(newpage);
1053                 else
1054                         putback_lru_page(newpage);
1055         }
1056 
1057         return rc;
1058 }
1059 
1060 /*
1061  * gcc 4.7 and 4.8 on arm get an ICEs when inlining unmap_and_move().  Work
1062  * around it.
1063  */
1064 #if (GCC_VERSION >= 40700 && GCC_VERSION < 40900) && defined(CONFIG_ARM)
1065 #define ICE_noinline noinline
1066 #else
1067 #define ICE_noinline
1068 #endif
1069 
1070 /*
1071  * Obtain the lock on page, remove all ptes and migrate the page
1072  * to the newly allocated page in newpage.
1073  */
1074 static ICE_noinline int unmap_and_move(new_page_t get_new_page,
1075                                    free_page_t put_new_page,
1076                                    unsigned long private, struct page *page,
1077                                    int force, enum migrate_mode mode,
1078                                    enum migrate_reason reason)
1079 {
1080         int rc = MIGRATEPAGE_SUCCESS;
1081         int *result = NULL;
1082         struct page *newpage;
1083 
1084         newpage = get_new_page(page, private, &result);
1085         if (!newpage)
1086                 return -ENOMEM;
1087 
1088         if (page_count(page) == 1) {
1089                 /* page was freed from under us. So we are done. */
1090                 ClearPageActive(page);
1091                 ClearPageUnevictable(page);
1092                 if (unlikely(__PageMovable(page))) {
1093                         lock_page(page);
1094                         if (!PageMovable(page))
1095                                 __ClearPageIsolated(page);
1096                         unlock_page(page);
1097                 }
1098                 if (put_new_page)
1099                         put_new_page(newpage, private);
1100                 else
1101                         put_page(newpage);
1102                 goto out;
1103         }
1104 
1105         if (unlikely(PageTransHuge(page))) {
1106                 lock_page(page);
1107                 rc = split_huge_page(page);
1108                 unlock_page(page);
1109                 if (rc)
1110                         goto out;
1111         }
1112 
1113         rc = __unmap_and_move(page, newpage, force, mode);
1114         if (rc == MIGRATEPAGE_SUCCESS)
1115                 set_page_owner_migrate_reason(newpage, reason);
1116 
1117 out:
1118         if (rc != -EAGAIN) {
1119                 /*
1120                  * A page that has been migrated has all references
1121                  * removed and will be freed. A page that has not been
1122                  * migrated will have kepts its references and be
1123                  * restored.
1124                  */
1125                 list_del(&page->lru);
1126 
1127                 /*
1128                  * Compaction can migrate also non-LRU pages which are
1129                  * not accounted to NR_ISOLATED_*. They can be recognized
1130                  * as __PageMovable
1131                  */
1132                 if (likely(!__PageMovable(page)))
1133                         dec_node_page_state(page, NR_ISOLATED_ANON +
1134                                         page_is_file_cache(page));
1135         }
1136 
1137         /*
1138          * If migration is successful, releases reference grabbed during
1139          * isolation. Otherwise, restore the page to right list unless
1140          * we want to retry.
1141          */
1142         if (rc == MIGRATEPAGE_SUCCESS) {
1143                 put_page(page);
1144                 if (reason == MR_MEMORY_FAILURE) {
1145                         /*
1146                          * Set PG_HWPoison on just freed page
1147                          * intentionally. Although it's rather weird,
1148                          * it's how HWPoison flag works at the moment.
1149                          */
1150                         if (!test_set_page_hwpoison(page))
1151                                 num_poisoned_pages_inc();
1152                 }
1153         } else {
1154                 if (rc != -EAGAIN) {
1155                         if (likely(!__PageMovable(page))) {
1156                                 putback_lru_page(page);
1157                                 goto put_new;
1158                         }
1159 
1160                         lock_page(page);
1161                         if (PageMovable(page))
1162                                 putback_movable_page(page);
1163                         else
1164                                 __ClearPageIsolated(page);
1165                         unlock_page(page);
1166                         put_page(page);
1167                 }
1168 put_new:
1169                 if (put_new_page)
1170                         put_new_page(newpage, private);
1171                 else
1172                         put_page(newpage);
1173         }
1174 
1175         if (result) {
1176                 if (rc)
1177                         *result = rc;
1178                 else
1179                         *result = page_to_nid(newpage);
1180         }
1181         return rc;
1182 }
1183 
1184 /*
1185  * Counterpart of unmap_and_move_page() for hugepage migration.
1186  *
1187  * This function doesn't wait the completion of hugepage I/O
1188  * because there is no race between I/O and migration for hugepage.
1189  * Note that currently hugepage I/O occurs only in direct I/O
1190  * where no lock is held and PG_writeback is irrelevant,
1191  * and writeback status of all subpages are counted in the reference
1192  * count of the head page (i.e. if all subpages of a 2MB hugepage are
1193  * under direct I/O, the reference of the head page is 512 and a bit more.)
1194  * This means that when we try to migrate hugepage whose subpages are
1195  * doing direct I/O, some references remain after try_to_unmap() and
1196  * hugepage migration fails without data corruption.
1197  *
1198  * There is also no race when direct I/O is issued on the page under migration,
1199  * because then pte is replaced with migration swap entry and direct I/O code
1200  * will wait in the page fault for migration to complete.
1201  */
1202 static int unmap_and_move_huge_page(new_page_t get_new_page,
1203                                 free_page_t put_new_page, unsigned long private,
1204                                 struct page *hpage, int force,
1205                                 enum migrate_mode mode, int reason)
1206 {
1207         int rc = -EAGAIN;
1208         int *result = NULL;
1209         int page_was_mapped = 0;
1210         struct page *new_hpage;
1211         struct anon_vma *anon_vma = NULL;
1212 
1213         /*
1214          * Movability of hugepages depends on architectures and hugepage size.
1215          * This check is necessary because some callers of hugepage migration
1216          * like soft offline and memory hotremove don't walk through page
1217          * tables or check whether the hugepage is pmd-based or not before
1218          * kicking migration.
1219          */
1220         if (!hugepage_migration_supported(page_hstate(hpage))) {
1221                 putback_active_hugepage(hpage);
1222                 return -ENOSYS;
1223         }
1224 
1225         new_hpage = get_new_page(hpage, private, &result);
1226         if (!new_hpage)
1227                 return -ENOMEM;
1228 
1229         if (!trylock_page(hpage)) {
1230                 if (!force || mode != MIGRATE_SYNC)
1231                         goto out;
1232                 lock_page(hpage);
1233         }
1234 
1235         if (PageAnon(hpage))
1236                 anon_vma = page_get_anon_vma(hpage);
1237 
1238         if (unlikely(!trylock_page(new_hpage)))
1239                 goto put_anon;
1240 
1241         if (page_mapped(hpage)) {
1242                 try_to_unmap(hpage,
1243                         TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
1244                 page_was_mapped = 1;
1245         }
1246 
1247         if (!page_mapped(hpage))
1248                 rc = move_to_new_page(new_hpage, hpage, mode);
1249 
1250         if (page_was_mapped)
1251                 remove_migration_ptes(hpage,
1252                         rc == MIGRATEPAGE_SUCCESS ? new_hpage : hpage, false);
1253 
1254         unlock_page(new_hpage);
1255 
1256 put_anon:
1257         if (anon_vma)
1258                 put_anon_vma(anon_vma);
1259 
1260         if (rc == MIGRATEPAGE_SUCCESS) {
1261                 hugetlb_cgroup_migrate(hpage, new_hpage);
1262                 put_new_page = NULL;
1263                 set_page_owner_migrate_reason(new_hpage, reason);
1264         }
1265 
1266         unlock_page(hpage);
1267 out:
1268         if (rc != -EAGAIN)
1269                 putback_active_hugepage(hpage);
1270 
1271         /*
1272          * If migration was not successful and there's a freeing callback, use
1273          * it.  Otherwise, put_page() will drop the reference grabbed during
1274          * isolation.
1275          */
1276         if (put_new_page)
1277                 put_new_page(new_hpage, private);
1278         else
1279                 putback_active_hugepage(new_hpage);
1280 
1281         if (result) {
1282                 if (rc)
1283                         *result = rc;
1284                 else
1285                         *result = page_to_nid(new_hpage);
1286         }
1287         return rc;
1288 }
1289 
1290 /*
1291  * migrate_pages - migrate the pages specified in a list, to the free pages
1292  *                 supplied as the target for the page migration
1293  *
1294  * @from:               The list of pages to be migrated.
1295  * @get_new_page:       The function used to allocate free pages to be used
1296  *                      as the target of the page migration.
1297  * @put_new_page:       The function used to free target pages if migration
1298  *                      fails, or NULL if no special handling is necessary.
1299  * @private:            Private data to be passed on to get_new_page()
1300  * @mode:               The migration mode that specifies the constraints for
1301  *                      page migration, if any.
1302  * @reason:             The reason for page migration.
1303  *
1304  * The function returns after 10 attempts or if no pages are movable any more
1305  * because the list has become empty or no retryable pages exist any more.
1306  * The caller should call putback_movable_pages() to return pages to the LRU
1307  * or free list only if ret != 0.
1308  *
1309  * Returns the number of pages that were not migrated, or an error code.
1310  */
1311 int migrate_pages(struct list_head *from, new_page_t get_new_page,
1312                 free_page_t put_new_page, unsigned long private,
1313                 enum migrate_mode mode, int reason)
1314 {
1315         int retry = 1;
1316         int nr_failed = 0;
1317         int nr_succeeded = 0;
1318         int pass = 0;
1319         struct page *page;
1320         struct page *page2;
1321         int swapwrite = current->flags & PF_SWAPWRITE;
1322         int rc;
1323 
1324         if (!swapwrite)
1325                 current->flags |= PF_SWAPWRITE;
1326 
1327         for(pass = 0; pass < 10 && retry; pass++) {
1328                 retry = 0;
1329 
1330                 list_for_each_entry_safe(page, page2, from, lru) {
1331                         cond_resched();
1332 
1333                         if (PageHuge(page))
1334                                 rc = unmap_and_move_huge_page(get_new_page,
1335                                                 put_new_page, private, page,
1336                                                 pass > 2, mode, reason);
1337                         else
1338                                 rc = unmap_and_move(get_new_page, put_new_page,
1339                                                 private, page, pass > 2, mode,
1340                                                 reason);
1341 
1342                         switch(rc) {
1343                         case -ENOMEM:
1344                                 nr_failed++;
1345                                 goto out;
1346                         case -EAGAIN:
1347                                 retry++;
1348                                 break;
1349                         case MIGRATEPAGE_SUCCESS:
1350                                 nr_succeeded++;
1351                                 break;
1352                         default:
1353                                 /*
1354                                  * Permanent failure (-EBUSY, -ENOSYS, etc.):
1355                                  * unlike -EAGAIN case, the failed page is
1356                                  * removed from migration page list and not
1357                                  * retried in the next outer loop.
1358                                  */
1359                                 nr_failed++;
1360                                 break;
1361                         }
1362                 }
1363         }
1364         nr_failed += retry;
1365         rc = nr_failed;
1366 out:
1367         if (nr_succeeded)
1368                 count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
1369         if (nr_failed)
1370                 count_vm_events(PGMIGRATE_FAIL, nr_failed);
1371         trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason);
1372 
1373         if (!swapwrite)
1374                 current->flags &= ~PF_SWAPWRITE;
1375 
1376         return rc;
1377 }
1378 
1379 #ifdef CONFIG_NUMA
1380 /*
1381  * Move a list of individual pages
1382  */
1383 struct page_to_node {
1384         unsigned long addr;
1385         struct page *page;
1386         int node;
1387         int status;
1388 };
1389 
1390 static struct page *new_page_node(struct page *p, unsigned long private,
1391                 int **result)
1392 {
1393         struct page_to_node *pm = (struct page_to_node *)private;
1394 
1395         while (pm->node != MAX_NUMNODES && pm->page != p)
1396                 pm++;
1397 
1398         if (pm->node == MAX_NUMNODES)
1399                 return NULL;
1400 
1401         *result = &pm->status;
1402 
1403         if (PageHuge(p))
1404                 return alloc_huge_page_node(page_hstate(compound_head(p)),
1405                                         pm->node);
1406         else
1407                 return __alloc_pages_node(pm->node,
1408                                 GFP_HIGHUSER_MOVABLE | __GFP_THISNODE, 0);
1409 }
1410 
1411 /*
1412  * Move a set of pages as indicated in the pm array. The addr
1413  * field must be set to the virtual address of the page to be moved
1414  * and the node number must contain a valid target node.
1415  * The pm array ends with node = MAX_NUMNODES.
1416  */
1417 static int do_move_page_to_node_array(struct mm_struct *mm,
1418                                       struct page_to_node *pm,
1419                                       int migrate_all)
1420 {
1421         int err;
1422         struct page_to_node *pp;
1423         LIST_HEAD(pagelist);
1424 
1425         down_read(&mm->mmap_sem);
1426 
1427         /*
1428          * Build a list of pages to migrate
1429          */
1430         for (pp = pm; pp->node != MAX_NUMNODES; pp++) {
1431                 struct vm_area_struct *vma;
1432                 struct page *page;
1433 
1434                 err = -EFAULT;
1435                 vma = find_vma(mm, pp->addr);
1436                 if (!vma || pp->addr < vma->vm_start || !vma_migratable(vma))
1437                         goto set_status;
1438 
1439                 /* FOLL_DUMP to ignore special (like zero) pages */
1440                 page = follow_page(vma, pp->addr,
1441                                 FOLL_GET | FOLL_SPLIT | FOLL_DUMP);
1442 
1443                 err = PTR_ERR(page);
1444                 if (IS_ERR(page))
1445                         goto set_status;
1446 
1447                 err = -ENOENT;
1448                 if (!page)
1449                         goto set_status;
1450 
1451                 pp->page = page;
1452                 err = page_to_nid(page);
1453 
1454                 if (err == pp->node)
1455                         /*
1456                          * Node already in the right place
1457                          */
1458                         goto put_and_set;
1459 
1460                 err = -EACCES;
1461                 if (page_mapcount(page) > 1 &&
1462                                 !migrate_all)
1463                         goto put_and_set;
1464 
1465                 if (PageHuge(page)) {
1466                         if (PageHead(page))
1467                                 isolate_huge_page(page, &pagelist);
1468                         goto put_and_set;
1469                 }
1470 
1471                 err = isolate_lru_page(page);
1472                 if (!err) {
1473                         list_add_tail(&page->lru, &pagelist);
1474                         inc_node_page_state(page, NR_ISOLATED_ANON +
1475                                             page_is_file_cache(page));
1476                 }
1477 put_and_set:
1478                 /*
1479                  * Either remove the duplicate refcount from
1480                  * isolate_lru_page() or drop the page ref if it was
1481                  * not isolated.
1482                  */
1483                 put_page(page);
1484 set_status:
1485                 pp->status = err;
1486         }
1487 
1488         err = 0;
1489         if (!list_empty(&pagelist)) {
1490                 err = migrate_pages(&pagelist, new_page_node, NULL,
1491                                 (unsigned long)pm, MIGRATE_SYNC, MR_SYSCALL);
1492                 if (err)
1493                         putback_movable_pages(&pagelist);
1494         }
1495 
1496         up_read(&mm->mmap_sem);
1497         return err;
1498 }
1499 
1500 /*
1501  * Migrate an array of page address onto an array of nodes and fill
1502  * the corresponding array of status.
1503  */
1504 static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
1505                          unsigned long nr_pages,
1506                          const void __user * __user *pages,
1507                          const int __user *nodes,
1508                          int __user *status, int flags)
1509 {
1510         struct page_to_node *pm;
1511         unsigned long chunk_nr_pages;
1512         unsigned long chunk_start;
1513         int err;
1514 
1515         err = -ENOMEM;
1516         pm = (struct page_to_node *)__get_free_page(GFP_KERNEL);
1517         if (!pm)
1518                 goto out;
1519 
1520         migrate_prep();
1521 
1522         /*
1523          * Store a chunk of page_to_node array in a page,
1524          * but keep the last one as a marker
1525          */
1526         chunk_nr_pages = (PAGE_SIZE / sizeof(struct page_to_node)) - 1;
1527 
1528         for (chunk_start = 0;
1529              chunk_start < nr_pages;
1530              chunk_start += chunk_nr_pages) {
1531                 int j;
1532 
1533                 if (chunk_start + chunk_nr_pages > nr_pages)
1534                         chunk_nr_pages = nr_pages - chunk_start;
1535 
1536                 /* fill the chunk pm with addrs and nodes from user-space */
1537                 for (j = 0; j < chunk_nr_pages; j++) {
1538                         const void __user *p;
1539                         int node;
1540 
1541                         err = -EFAULT;
1542                         if (get_user(p, pages + j + chunk_start))
1543                                 goto out_pm;
1544                         pm[j].addr = (unsigned long) p;
1545 
1546                         if (get_user(node, nodes + j + chunk_start))
1547                                 goto out_pm;
1548 
1549                         err = -ENODEV;
1550                         if (node < 0 || node >= MAX_NUMNODES)
1551                                 goto out_pm;
1552 
1553                         if (!node_state(node, N_MEMORY))
1554                                 goto out_pm;
1555 
1556                         err = -EACCES;
1557                         if (!node_isset(node, task_nodes))
1558                                 goto out_pm;
1559 
1560                         pm[j].node = node;
1561                 }
1562 
1563                 /* End marker for this chunk */
1564                 pm[chunk_nr_pages].node = MAX_NUMNODES;
1565 
1566                 /* Migrate this chunk */
1567                 err = do_move_page_to_node_array(mm, pm,
1568                                                  flags & MPOL_MF_MOVE_ALL);
1569                 if (err < 0)
1570                         goto out_pm;
1571 
1572                 /* Return status information */
1573                 for (j = 0; j < chunk_nr_pages; j++)
1574                         if (put_user(pm[j].status, status + j + chunk_start)) {
1575                                 err = -EFAULT;
1576                                 goto out_pm;
1577                         }
1578         }
1579         err = 0;
1580 
1581 out_pm:
1582         free_page((unsigned long)pm);
1583 out:
1584         return err;
1585 }
1586 
1587 /*
1588  * Determine the nodes of an array of pages and store it in an array of status.
1589  */
1590 static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
1591                                 const void __user **pages, int *status)
1592 {
1593         unsigned long i;
1594 
1595         down_read(&mm->mmap_sem);
1596 
1597         for (i = 0; i < nr_pages; i++) {
1598                 unsigned long addr = (unsigned long)(*pages);
1599                 struct vm_area_struct *vma;
1600                 struct page *page;
1601                 int err = -EFAULT;
1602 
1603                 vma = find_vma(mm, addr);
1604                 if (!vma || addr < vma->vm_start)
1605                         goto set_status;
1606 
1607                 /* FOLL_DUMP to ignore special (like zero) pages */
1608                 page = follow_page(vma, addr, FOLL_DUMP);
1609 
1610                 err = PTR_ERR(page);
1611                 if (IS_ERR(page))
1612                         goto set_status;
1613 
1614                 err = page ? page_to_nid(page) : -ENOENT;
1615 set_status:
1616                 *status = err;
1617 
1618                 pages++;
1619                 status++;
1620         }
1621 
1622         up_read(&mm->mmap_sem);
1623 }
1624 
1625 /*
1626  * Determine the nodes of a user array of pages and store it in
1627  * a user array of status.
1628  */
1629 static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
1630                          const void __user * __user *pages,
1631                          int __user *status)
1632 {
1633 #define DO_PAGES_STAT_CHUNK_NR 16
1634         const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
1635         int chunk_status[DO_PAGES_STAT_CHUNK_NR];
1636 
1637         while (nr_pages) {
1638                 unsigned long chunk_nr;
1639 
1640                 chunk_nr = nr_pages;
1641                 if (chunk_nr > DO_PAGES_STAT_CHUNK_NR)
1642                         chunk_nr = DO_PAGES_STAT_CHUNK_NR;
1643 
1644                 if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages)))
1645                         break;
1646 
1647                 do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
1648 
1649                 if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
1650                         break;
1651 
1652                 pages += chunk_nr;
1653                 status += chunk_nr;
1654                 nr_pages -= chunk_nr;
1655         }
1656         return nr_pages ? -EFAULT : 0;
1657 }
1658 
1659 /*
1660  * Move a list of pages in the address space of the currently executing
1661  * process.
1662  */
1663 SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
1664                 const void __user * __user *, pages,
1665                 const int __user *, nodes,
1666                 int __user *, status, int, flags)
1667 {
1668         const struct cred *cred = current_cred(), *tcred;
1669         struct task_struct *task;
1670         struct mm_struct *mm;
1671         int err;
1672         nodemask_t task_nodes;
1673 
1674         /* Check flags */
1675         if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
1676                 return -EINVAL;
1677 
1678         if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
1679                 return -EPERM;
1680 
1681         /* Find the mm_struct */
1682         rcu_read_lock();
1683         task = pid ? find_task_by_vpid(pid) : current;
1684         if (!task) {
1685                 rcu_read_unlock();
1686                 return -ESRCH;
1687         }
1688         get_task_struct(task);
1689 
1690         /*
1691          * Check if this process has the right to modify the specified
1692          * process. The right exists if the process has administrative
1693          * capabilities, superuser privileges or the same
1694          * userid as the target process.
1695          */
1696         tcred = __task_cred(task);
1697         if (!uid_eq(cred->euid, tcred->suid) && !uid_eq(cred->euid, tcred->uid) &&
1698             !uid_eq(cred->uid,  tcred->suid) && !uid_eq(cred->uid,  tcred->uid) &&
1699             !capable(CAP_SYS_NICE)) {
1700                 rcu_read_unlock();
1701                 err = -EPERM;
1702                 goto out;
1703         }
1704         rcu_read_unlock();
1705 
1706         err = security_task_movememory(task);
1707         if (err)
1708                 goto out;
1709 
1710         task_nodes = cpuset_mems_allowed(task);
1711         mm = get_task_mm(task);
1712         put_task_struct(task);
1713 
1714         if (!mm)
1715                 return -EINVAL;
1716 
1717         if (nodes)
1718                 err = do_pages_move(mm, task_nodes, nr_pages, pages,
1719                                     nodes, status, flags);
1720         else
1721                 err = do_pages_stat(mm, nr_pages, pages, status);
1722 
1723         mmput(mm);
1724         return err;
1725 
1726 out:
1727         put_task_struct(task);
1728         return err;
1729 }
1730 
1731 #ifdef CONFIG_NUMA_BALANCING
1732 /*
1733  * Returns true if this is a safe migration target node for misplaced NUMA
1734  * pages. Currently it only checks the watermarks which crude
1735  */
1736 static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
1737                                    unsigned long nr_migrate_pages)
1738 {
1739         int z;
1740 
1741         if (!pgdat_reclaimable(pgdat))
1742                 return false;
1743 
1744         for (z = pgdat->nr_zones - 1; z >= 0; z--) {
1745                 struct zone *zone = pgdat->node_zones + z;
1746 
1747                 if (!populated_zone(zone))
1748                         continue;
1749 
1750                 /* Avoid waking kswapd by allocating pages_to_migrate pages. */
1751                 if (!zone_watermark_ok(zone, 0,
1752                                        high_wmark_pages(zone) +
1753                                        nr_migrate_pages,
1754                                        0, 0))
1755                         continue;
1756                 return true;
1757         }
1758         return false;
1759 }
1760 
1761 static struct page *alloc_misplaced_dst_page(struct page *page,
1762                                            unsigned long data,
1763                                            int **result)
1764 {
1765         int nid = (int) data;
1766         struct page *newpage;
1767 
1768         newpage = __alloc_pages_node(nid,
1769                                          (GFP_HIGHUSER_MOVABLE |
1770                                           __GFP_THISNODE | __GFP_NOMEMALLOC |
1771                                           __GFP_NORETRY | __GFP_NOWARN) &
1772                                          ~__GFP_RECLAIM, 0);
1773 
1774         return newpage;
1775 }
1776 
1777 /*
1778  * page migration rate limiting control.
1779  * Do not migrate more than @pages_to_migrate in a @migrate_interval_millisecs
1780  * window of time. Default here says do not migrate more than 1280M per second.
1781  */
1782 static unsigned int migrate_interval_millisecs __read_mostly = 100;
1783 static unsigned int ratelimit_pages __read_mostly = 128 << (20 - PAGE_SHIFT);
1784 
1785 /* Returns true if the node is migrate rate-limited after the update */
1786 static bool numamigrate_update_ratelimit(pg_data_t *pgdat,
1787                                         unsigned long nr_pages)
1788 {
1789         /*
1790          * Rate-limit the amount of data that is being migrated to a node.
1791          * Optimal placement is no good if the memory bus is saturated and
1792          * all the time is being spent migrating!
1793          */
1794         if (time_after(jiffies, pgdat->numabalancing_migrate_next_window)) {
1795                 spin_lock(&pgdat->numabalancing_migrate_lock);
1796                 pgdat->numabalancing_migrate_nr_pages = 0;
1797                 pgdat->numabalancing_migrate_next_window = jiffies +
1798                         msecs_to_jiffies(migrate_interval_millisecs);
1799                 spin_unlock(&pgdat->numabalancing_migrate_lock);
1800         }
1801         if (pgdat->numabalancing_migrate_nr_pages > ratelimit_pages) {
1802                 trace_mm_numa_migrate_ratelimit(current, pgdat->node_id,
1803                                                                 nr_pages);
1804                 return true;
1805         }
1806 
1807         /*
1808          * This is an unlocked non-atomic update so errors are possible.
1809          * The consequences are failing to migrate when we potentiall should
1810          * have which is not severe enough to warrant locking. If it is ever
1811          * a problem, it can be converted to a per-cpu counter.
1812          */
1813         pgdat->numabalancing_migrate_nr_pages += nr_pages;
1814         return false;
1815 }
1816 
1817 static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
1818 {
1819         int page_lru;
1820 
1821         VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page);
1822 
1823         /* Avoid migrating to a node that is nearly full */
1824         if (!migrate_balanced_pgdat(pgdat, 1UL << compound_order(page)))
1825                 return 0;
1826 
1827         if (isolate_lru_page(page))
1828                 return 0;
1829 
1830         /*
1831          * migrate_misplaced_transhuge_page() skips page migration's usual
1832          * check on page_count(), so we must do it here, now that the page
1833          * has been isolated: a GUP pin, or any other pin, prevents migration.
1834          * The expected page count is 3: 1 for page's mapcount and 1 for the
1835          * caller's pin and 1 for the reference taken by isolate_lru_page().
1836          */
1837         if (PageTransHuge(page) && page_count(page) != 3) {
1838                 putback_lru_page(page);
1839                 return 0;
1840         }
1841 
1842         page_lru = page_is_file_cache(page);
1843         mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_lru,
1844                                 hpage_nr_pages(page));
1845 
1846         /*
1847          * Isolating the page has taken another reference, so the
1848          * caller's reference can be safely dropped without the page
1849          * disappearing underneath us during migration.
1850          */
1851         put_page(page);
1852         return 1;
1853 }
1854 
1855 bool pmd_trans_migrating(pmd_t pmd)
1856 {
1857         struct page *page = pmd_page(pmd);
1858         return PageLocked(page);
1859 }
1860 
1861 /*
1862  * Attempt to migrate a misplaced page to the specified destination
1863  * node. Caller is expected to have an elevated reference count on
1864  * the page that will be dropped by this function before returning.
1865  */
1866 int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
1867                            int node)
1868 {
1869         pg_data_t *pgdat = NODE_DATA(node);
1870         int isolated;
1871         int nr_remaining;
1872         LIST_HEAD(migratepages);
1873 
1874         /*
1875          * Don't migrate file pages that are mapped in multiple processes
1876          * with execute permissions as they are probably shared libraries.
1877          */
1878         if (page_mapcount(page) != 1 && page_is_file_cache(page) &&
1879             (vma->vm_flags & VM_EXEC))
1880                 goto out;
1881 
1882         /*
1883          * Rate-limit the amount of data that is being migrated to a node.
1884          * Optimal placement is no good if the memory bus is saturated and
1885          * all the time is being spent migrating!
1886          */
1887         if (numamigrate_update_ratelimit(pgdat, 1))
1888                 goto out;
1889 
1890         isolated = numamigrate_isolate_page(pgdat, page);
1891         if (!isolated)
1892                 goto out;
1893 
1894         list_add(&page->lru, &migratepages);
1895         nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page,
1896                                      NULL, node, MIGRATE_ASYNC,
1897                                      MR_NUMA_MISPLACED);
1898         if (nr_remaining) {
1899                 if (!list_empty(&migratepages)) {
1900                         list_del(&page->lru);
1901                         dec_node_page_state(page, NR_ISOLATED_ANON +
1902                                         page_is_file_cache(page));
1903                         putback_lru_page(page);
1904                 }
1905                 isolated = 0;
1906         } else
1907                 count_vm_numa_event(NUMA_PAGE_MIGRATE);
1908         BUG_ON(!list_empty(&migratepages));
1909         return isolated;
1910 
1911 out:
1912         put_page(page);
1913         return 0;
1914 }
1915 #endif /* CONFIG_NUMA_BALANCING */
1916 
1917 #if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
1918 /*
1919  * Migrates a THP to a given target node. page must be locked and is unlocked
1920  * before returning.
1921  */
1922 int migrate_misplaced_transhuge_page(struct mm_struct *mm,
1923                                 struct vm_area_struct *vma,
1924                                 pmd_t *pmd, pmd_t entry,
1925                                 unsigned long address,
1926                                 struct page *page, int node)
1927 {
1928         spinlock_t *ptl;
1929         pg_data_t *pgdat = NODE_DATA(node);
1930         int isolated = 0;
1931         struct page *new_page = NULL;
1932         int page_lru = page_is_file_cache(page);
1933         unsigned long mmun_start = address & HPAGE_PMD_MASK;
1934         unsigned long mmun_end = mmun_start + HPAGE_PMD_SIZE;
1935         pmd_t orig_entry;
1936 
1937         /*
1938          * Rate-limit the amount of data that is being migrated to a node.
1939          * Optimal placement is no good if the memory bus is saturated and
1940          * all the time is being spent migrating!
1941          */
1942         if (numamigrate_update_ratelimit(pgdat, HPAGE_PMD_NR))
1943                 goto out_dropref;
1944 
1945         new_page = alloc_pages_node(node,
1946                 (GFP_TRANSHUGE_LIGHT | __GFP_THISNODE),
1947                 HPAGE_PMD_ORDER);
1948         if (!new_page)
1949                 goto out_fail;
1950         prep_transhuge_page(new_page);
1951 
1952         isolated = numamigrate_isolate_page(pgdat, page);
1953         if (!isolated) {
1954                 put_page(new_page);
1955                 goto out_fail;
1956         }
1957         /*
1958          * We are not sure a pending tlb flush here is for a huge page
1959          * mapping or not. Hence use the tlb range variant
1960          */
1961         if (mm_tlb_flush_pending(mm))
1962                 flush_tlb_range(vma, mmun_start, mmun_end);
1963 
1964         /* Prepare a page as a migration target */
1965         __SetPageLocked(new_page);
1966         __SetPageSwapBacked(new_page);
1967 
1968         /* anon mapping, we can simply copy page->mapping to the new page: */
1969         new_page->mapping = page->mapping;
1970         new_page->index = page->index;
1971         migrate_page_copy(new_page, page);
1972         WARN_ON(PageLRU(new_page));
1973 
1974         /* Recheck the target PMD */
1975         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1976         ptl = pmd_lock(mm, pmd);
1977         if (unlikely(!pmd_same(*pmd, entry) || page_count(page) != 2)) {
1978 fail_putback:
1979                 spin_unlock(ptl);
1980                 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1981 
1982                 /* Reverse changes made by migrate_page_copy() */
1983                 if (TestClearPageActive(new_page))
1984                         SetPageActive(page);
1985                 if (TestClearPageUnevictable(new_page))
1986                         SetPageUnevictable(page);
1987 
1988                 unlock_page(new_page);
1989                 put_page(new_page);             /* Free it */
1990 
1991                 /* Retake the callers reference and putback on LRU */
1992                 get_page(page);
1993                 putback_lru_page(page);
1994                 mod_node_page_state(page_pgdat(page),
1995                          NR_ISOLATED_ANON + page_lru, -HPAGE_PMD_NR);
1996 
1997                 goto out_unlock;
1998         }
1999 
2000         orig_entry = *pmd;
2001         entry = mk_huge_pmd(new_page, vma->vm_page_prot);
2002         entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
2003 
2004         /*
2005          * Clear the old entry under pagetable lock and establish the new PTE.
2006          * Any parallel GUP will either observe the old page blocking on the
2007          * page lock, block on the page table lock or observe the new page.
2008          * The SetPageUptodate on the new page and page_add_new_anon_rmap
2009          * guarantee the copy is visible before the pagetable update.
2010          */
2011         flush_cache_range(vma, mmun_start, mmun_end);
2012         page_add_anon_rmap(new_page, vma, mmun_start, true);
2013         pmdp_huge_clear_flush_notify(vma, mmun_start, pmd);
2014         set_pmd_at(mm, mmun_start, pmd, entry);
2015         update_mmu_cache_pmd(vma, address, &entry);
2016 
2017         if (page_count(page) != 2) {
2018                 set_pmd_at(mm, mmun_start, pmd, orig_entry);
2019                 flush_pmd_tlb_range(vma, mmun_start, mmun_end);
2020                 mmu_notifier_invalidate_range(mm, mmun_start, mmun_end);
2021                 update_mmu_cache_pmd(vma, address, &entry);
2022                 page_remove_rmap(new_page, true);
2023                 goto fail_putback;
2024         }
2025 
2026         mlock_migrate_page(new_page, page);
2027         page_remove_rmap(page, true);
2028         set_page_owner_migrate_reason(new_page, MR_NUMA_MISPLACED);
2029 
2030         spin_unlock(ptl);
2031         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2032 
2033         /* Take an "isolate" reference and put new page on the LRU. */
2034         get_page(new_page);
2035         putback_lru_page(new_page);
2036 
2037         unlock_page(new_page);
2038         unlock_page(page);
2039         put_page(page);                 /* Drop the rmap reference */
2040         put_page(page);                 /* Drop the LRU isolation reference */
2041 
2042         count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR);
2043         count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR);
2044 
2045         mod_node_page_state(page_pgdat(page),
2046                         NR_ISOLATED_ANON + page_lru,
2047                         -HPAGE_PMD_NR);
2048         return isolated;
2049 
2050 out_fail:
2051         count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
2052 out_dropref:
2053         ptl = pmd_lock(mm, pmd);
2054         if (pmd_same(*pmd, entry)) {
2055                 entry = pmd_modify(entry, vma->vm_page_prot);
2056                 set_pmd_at(mm, mmun_start, pmd, entry);
2057                 update_mmu_cache_pmd(vma, address, &entry);
2058         }
2059         spin_unlock(ptl);
2060 
2061 out_unlock:
2062         unlock_page(page);
2063         put_page(page);
2064         return 0;
2065 }
2066 #endif /* CONFIG_NUMA_BALANCING */
2067 
2068 #endif /* CONFIG_NUMA */
2069 

This page was automatically generated by LXR 0.3.1 (source).  •  Linux is a registered trademark of Linus Torvalds  •  Contact us