~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

TOMOYO Linux Cross Reference
Linux/mm/migrate.c

Version: ~ [ linux-5.13-rc1 ] ~ [ linux-5.12.2 ] ~ [ linux-5.11.19 ] ~ [ linux-5.10.35 ] ~ [ linux-5.9.16 ] ~ [ linux-5.8.18 ] ~ [ linux-5.7.19 ] ~ [ linux-5.6.19 ] ~ [ linux-5.5.19 ] ~ [ linux-5.4.117 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.190 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.232 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.268 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.268 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.18.140 ] ~ [ linux-3.16.85 ] ~ [ linux-3.14.79 ] ~ [ linux-3.12.74 ] ~ [ linux-3.10.108 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

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

~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

kernel.org | git.kernel.org | LWN.net | Project Home | Wiki (Japanese) | Wiki (English) | SVN repository | Mail admin

Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.

osdn.jp