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1 | /* | |
2 | * Memory Migration functionality - linux/mm/migration.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/module.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/memcontrol.h> | |
34 | #include <linux/syscalls.h> | |
35 | #include <linux/gfp.h> | |
36 | ||
37 | #include "internal.h" | |
38 | ||
39 | #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) | |
40 | ||
41 | /* | |
42 | * migrate_prep() needs to be called before we start compiling a list of pages | |
43 | * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is | |
44 | * undesirable, use migrate_prep_local() | |
45 | */ | |
46 | int migrate_prep(void) | |
47 | { | |
48 | /* | |
49 | * Clear the LRU lists so pages can be isolated. | |
50 | * Note that pages may be moved off the LRU after we have | |
51 | * drained them. Those pages will fail to migrate like other | |
52 | * pages that may be busy. | |
53 | */ | |
54 | lru_add_drain_all(); | |
55 | ||
56 | return 0; | |
57 | } | |
58 | ||
59 | /* Do the necessary work of migrate_prep but not if it involves other CPUs */ | |
60 | int migrate_prep_local(void) | |
61 | { | |
62 | lru_add_drain(); | |
63 | ||
64 | return 0; | |
65 | } | |
66 | ||
67 | /* | |
68 | * Add isolated pages on the list back to the LRU under page lock | |
69 | * to avoid leaking evictable pages back onto unevictable list. | |
70 | */ | |
71 | void putback_lru_pages(struct list_head *l) | |
72 | { | |
73 | struct page *page; | |
74 | struct page *page2; | |
75 | ||
76 | list_for_each_entry_safe(page, page2, l, lru) { | |
77 | list_del(&page->lru); | |
78 | dec_zone_page_state(page, NR_ISOLATED_ANON + | |
79 | page_is_file_cache(page)); | |
80 | putback_lru_page(page); | |
81 | } | |
82 | } | |
83 | ||
84 | /* | |
85 | * Restore a potential migration pte to a working pte entry | |
86 | */ | |
87 | static int remove_migration_pte(struct page *new, struct vm_area_struct *vma, | |
88 | unsigned long addr, void *old) | |
89 | { | |
90 | struct mm_struct *mm = vma->vm_mm; | |
91 | swp_entry_t entry; | |
92 | pgd_t *pgd; | |
93 | pud_t *pud; | |
94 | pmd_t *pmd; | |
95 | pte_t *ptep, pte; | |
96 | spinlock_t *ptl; | |
97 | ||
98 | pgd = pgd_offset(mm, addr); | |
99 | if (!pgd_present(*pgd)) | |
100 | goto out; | |
101 | ||
102 | pud = pud_offset(pgd, addr); | |
103 | if (!pud_present(*pud)) | |
104 | goto out; | |
105 | ||
106 | pmd = pmd_offset(pud, addr); | |
107 | if (!pmd_present(*pmd)) | |
108 | goto out; | |
109 | ||
110 | ptep = pte_offset_map(pmd, addr); | |
111 | ||
112 | if (!is_swap_pte(*ptep)) { | |
113 | pte_unmap(ptep); | |
114 | goto out; | |
115 | } | |
116 | ||
117 | ptl = pte_lockptr(mm, pmd); | |
118 | spin_lock(ptl); | |
119 | pte = *ptep; | |
120 | if (!is_swap_pte(pte)) | |
121 | goto unlock; | |
122 | ||
123 | entry = pte_to_swp_entry(pte); | |
124 | ||
125 | if (!is_migration_entry(entry) || | |
126 | migration_entry_to_page(entry) != old) | |
127 | goto unlock; | |
128 | ||
129 | get_page(new); | |
130 | pte = pte_mkold(mk_pte(new, vma->vm_page_prot)); | |
131 | if (is_write_migration_entry(entry)) | |
132 | pte = pte_mkwrite(pte); | |
133 | flush_cache_page(vma, addr, pte_pfn(pte)); | |
134 | set_pte_at(mm, addr, ptep, pte); | |
135 | ||
136 | if (PageAnon(new)) | |
137 | page_add_anon_rmap(new, vma, addr); | |
138 | else | |
139 | page_add_file_rmap(new); | |
140 | ||
141 | /* No need to invalidate - it was non-present before */ | |
142 | update_mmu_cache(vma, addr, ptep); | |
143 | unlock: | |
144 | pte_unmap_unlock(ptep, ptl); | |
145 | out: | |
146 | return SWAP_AGAIN; | |
147 | } | |
148 | ||
149 | /* | |
150 | * Get rid of all migration entries and replace them by | |
151 | * references to the indicated page. | |
152 | */ | |
153 | static void remove_migration_ptes(struct page *old, struct page *new) | |
154 | { | |
155 | rmap_walk(new, remove_migration_pte, old); | |
156 | } | |
157 | ||
158 | /* | |
159 | * Something used the pte of a page under migration. We need to | |
160 | * get to the page and wait until migration is finished. | |
161 | * When we return from this function the fault will be retried. | |
162 | * | |
163 | * This function is called from do_swap_page(). | |
164 | */ | |
165 | void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, | |
166 | unsigned long address) | |
167 | { | |
168 | pte_t *ptep, pte; | |
169 | spinlock_t *ptl; | |
170 | swp_entry_t entry; | |
171 | struct page *page; | |
172 | ||
173 | ptep = pte_offset_map_lock(mm, pmd, address, &ptl); | |
174 | pte = *ptep; | |
175 | if (!is_swap_pte(pte)) | |
176 | goto out; | |
177 | ||
178 | entry = pte_to_swp_entry(pte); | |
179 | if (!is_migration_entry(entry)) | |
180 | goto out; | |
181 | ||
182 | page = migration_entry_to_page(entry); | |
183 | ||
184 | /* | |
185 | * Once radix-tree replacement of page migration started, page_count | |
186 | * *must* be zero. And, we don't want to call wait_on_page_locked() | |
187 | * against a page without get_page(). | |
188 | * So, we use get_page_unless_zero(), here. Even failed, page fault | |
189 | * will occur again. | |
190 | */ | |
191 | if (!get_page_unless_zero(page)) | |
192 | goto out; | |
193 | pte_unmap_unlock(ptep, ptl); | |
194 | wait_on_page_locked(page); | |
195 | put_page(page); | |
196 | return; | |
197 | out: | |
198 | pte_unmap_unlock(ptep, ptl); | |
199 | } | |
200 | ||
201 | /* | |
202 | * Replace the page in the mapping. | |
203 | * | |
204 | * The number of remaining references must be: | |
205 | * 1 for anonymous pages without a mapping | |
206 | * 2 for pages with a mapping | |
207 | * 3 for pages with a mapping and PagePrivate/PagePrivate2 set. | |
208 | */ | |
209 | static int migrate_page_move_mapping(struct address_space *mapping, | |
210 | struct page *newpage, struct page *page) | |
211 | { | |
212 | int expected_count; | |
213 | void **pslot; | |
214 | ||
215 | if (!mapping) { | |
216 | /* Anonymous page without mapping */ | |
217 | if (page_count(page) != 1) | |
218 | return -EAGAIN; | |
219 | return 0; | |
220 | } | |
221 | ||
222 | spin_lock_irq(&mapping->tree_lock); | |
223 | ||
224 | pslot = radix_tree_lookup_slot(&mapping->page_tree, | |
225 | page_index(page)); | |
226 | ||
227 | expected_count = 2 + page_has_private(page); | |
228 | if (page_count(page) != expected_count || | |
229 | (struct page *)radix_tree_deref_slot(pslot) != page) { | |
230 | spin_unlock_irq(&mapping->tree_lock); | |
231 | return -EAGAIN; | |
232 | } | |
233 | ||
234 | if (!page_freeze_refs(page, expected_count)) { | |
235 | spin_unlock_irq(&mapping->tree_lock); | |
236 | return -EAGAIN; | |
237 | } | |
238 | ||
239 | /* | |
240 | * Now we know that no one else is looking at the page. | |
241 | */ | |
242 | get_page(newpage); /* add cache reference */ | |
243 | if (PageSwapCache(page)) { | |
244 | SetPageSwapCache(newpage); | |
245 | set_page_private(newpage, page_private(page)); | |
246 | } | |
247 | ||
248 | radix_tree_replace_slot(pslot, newpage); | |
249 | ||
250 | page_unfreeze_refs(page, expected_count); | |
251 | /* | |
252 | * Drop cache reference from old page. | |
253 | * We know this isn't the last reference. | |
254 | */ | |
255 | __put_page(page); | |
256 | ||
257 | /* | |
258 | * If moved to a different zone then also account | |
259 | * the page for that zone. Other VM counters will be | |
260 | * taken care of when we establish references to the | |
261 | * new page and drop references to the old page. | |
262 | * | |
263 | * Note that anonymous pages are accounted for | |
264 | * via NR_FILE_PAGES and NR_ANON_PAGES if they | |
265 | * are mapped to swap space. | |
266 | */ | |
267 | __dec_zone_page_state(page, NR_FILE_PAGES); | |
268 | __inc_zone_page_state(newpage, NR_FILE_PAGES); | |
269 | if (PageSwapBacked(page)) { | |
270 | __dec_zone_page_state(page, NR_SHMEM); | |
271 | __inc_zone_page_state(newpage, NR_SHMEM); | |
272 | } | |
273 | spin_unlock_irq(&mapping->tree_lock); | |
274 | ||
275 | return 0; | |
276 | } | |
277 | ||
278 | /* | |
279 | * Copy the page to its new location | |
280 | */ | |
281 | static void migrate_page_copy(struct page *newpage, struct page *page) | |
282 | { | |
283 | copy_highpage(newpage, page); | |
284 | ||
285 | if (PageError(page)) | |
286 | SetPageError(newpage); | |
287 | if (PageReferenced(page)) | |
288 | SetPageReferenced(newpage); | |
289 | if (PageUptodate(page)) | |
290 | SetPageUptodate(newpage); | |
291 | if (TestClearPageActive(page)) { | |
292 | VM_BUG_ON(PageUnevictable(page)); | |
293 | SetPageActive(newpage); | |
294 | } else if (TestClearPageUnevictable(page)) | |
295 | SetPageUnevictable(newpage); | |
296 | if (PageChecked(page)) | |
297 | SetPageChecked(newpage); | |
298 | if (PageMappedToDisk(page)) | |
299 | SetPageMappedToDisk(newpage); | |
300 | ||
301 | if (PageDirty(page)) { | |
302 | clear_page_dirty_for_io(page); | |
303 | /* | |
304 | * Want to mark the page and the radix tree as dirty, and | |
305 | * redo the accounting that clear_page_dirty_for_io undid, | |
306 | * but we can't use set_page_dirty because that function | |
307 | * is actually a signal that all of the page has become dirty. | |
308 | * Wheras only part of our page may be dirty. | |
309 | */ | |
310 | __set_page_dirty_nobuffers(newpage); | |
311 | } | |
312 | ||
313 | mlock_migrate_page(newpage, page); | |
314 | ksm_migrate_page(newpage, page); | |
315 | ||
316 | ClearPageSwapCache(page); | |
317 | ClearPagePrivate(page); | |
318 | set_page_private(page, 0); | |
319 | page->mapping = NULL; | |
320 | ||
321 | /* | |
322 | * If any waiters have accumulated on the new page then | |
323 | * wake them up. | |
324 | */ | |
325 | if (PageWriteback(newpage)) | |
326 | end_page_writeback(newpage); | |
327 | } | |
328 | ||
329 | /************************************************************ | |
330 | * Migration functions | |
331 | ***********************************************************/ | |
332 | ||
333 | /* Always fail migration. Used for mappings that are not movable */ | |
334 | int fail_migrate_page(struct address_space *mapping, | |
335 | struct page *newpage, struct page *page) | |
336 | { | |
337 | return -EIO; | |
338 | } | |
339 | EXPORT_SYMBOL(fail_migrate_page); | |
340 | ||
341 | /* | |
342 | * Common logic to directly migrate a single page suitable for | |
343 | * pages that do not use PagePrivate/PagePrivate2. | |
344 | * | |
345 | * Pages are locked upon entry and exit. | |
346 | */ | |
347 | int migrate_page(struct address_space *mapping, | |
348 | struct page *newpage, struct page *page) | |
349 | { | |
350 | int rc; | |
351 | ||
352 | BUG_ON(PageWriteback(page)); /* Writeback must be complete */ | |
353 | ||
354 | rc = migrate_page_move_mapping(mapping, newpage, page); | |
355 | ||
356 | if (rc) | |
357 | return rc; | |
358 | ||
359 | migrate_page_copy(newpage, page); | |
360 | return 0; | |
361 | } | |
362 | EXPORT_SYMBOL(migrate_page); | |
363 | ||
364 | #ifdef CONFIG_BLOCK | |
365 | /* | |
366 | * Migration function for pages with buffers. This function can only be used | |
367 | * if the underlying filesystem guarantees that no other references to "page" | |
368 | * exist. | |
369 | */ | |
370 | int buffer_migrate_page(struct address_space *mapping, | |
371 | struct page *newpage, struct page *page) | |
372 | { | |
373 | struct buffer_head *bh, *head; | |
374 | int rc; | |
375 | ||
376 | if (!page_has_buffers(page)) | |
377 | return migrate_page(mapping, newpage, page); | |
378 | ||
379 | head = page_buffers(page); | |
380 | ||
381 | rc = migrate_page_move_mapping(mapping, newpage, page); | |
382 | ||
383 | if (rc) | |
384 | return rc; | |
385 | ||
386 | bh = head; | |
387 | do { | |
388 | get_bh(bh); | |
389 | lock_buffer(bh); | |
390 | bh = bh->b_this_page; | |
391 | ||
392 | } while (bh != head); | |
393 | ||
394 | ClearPagePrivate(page); | |
395 | set_page_private(newpage, page_private(page)); | |
396 | set_page_private(page, 0); | |
397 | put_page(page); | |
398 | get_page(newpage); | |
399 | ||
400 | bh = head; | |
401 | do { | |
402 | set_bh_page(bh, newpage, bh_offset(bh)); | |
403 | bh = bh->b_this_page; | |
404 | ||
405 | } while (bh != head); | |
406 | ||
407 | SetPagePrivate(newpage); | |
408 | ||
409 | migrate_page_copy(newpage, page); | |
410 | ||
411 | bh = head; | |
412 | do { | |
413 | unlock_buffer(bh); | |
414 | put_bh(bh); | |
415 | bh = bh->b_this_page; | |
416 | ||
417 | } while (bh != head); | |
418 | ||
419 | return 0; | |
420 | } | |
421 | EXPORT_SYMBOL(buffer_migrate_page); | |
422 | #endif | |
423 | ||
424 | /* | |
425 | * Writeback a page to clean the dirty state | |
426 | */ | |
427 | static int writeout(struct address_space *mapping, struct page *page) | |
428 | { | |
429 | struct writeback_control wbc = { | |
430 | .sync_mode = WB_SYNC_NONE, | |
431 | .nr_to_write = 1, | |
432 | .range_start = 0, | |
433 | .range_end = LLONG_MAX, | |
434 | .nonblocking = 1, | |
435 | .for_reclaim = 1 | |
436 | }; | |
437 | int rc; | |
438 | ||
439 | if (!mapping->a_ops->writepage) | |
440 | /* No write method for the address space */ | |
441 | return -EINVAL; | |
442 | ||
443 | if (!clear_page_dirty_for_io(page)) | |
444 | /* Someone else already triggered a write */ | |
445 | return -EAGAIN; | |
446 | ||
447 | /* | |
448 | * A dirty page may imply that the underlying filesystem has | |
449 | * the page on some queue. So the page must be clean for | |
450 | * migration. Writeout may mean we loose the lock and the | |
451 | * page state is no longer what we checked for earlier. | |
452 | * At this point we know that the migration attempt cannot | |
453 | * be successful. | |
454 | */ | |
455 | remove_migration_ptes(page, page); | |
456 | ||
457 | rc = mapping->a_ops->writepage(page, &wbc); | |
458 | ||
459 | if (rc != AOP_WRITEPAGE_ACTIVATE) | |
460 | /* unlocked. Relock */ | |
461 | lock_page(page); | |
462 | ||
463 | return (rc < 0) ? -EIO : -EAGAIN; | |
464 | } | |
465 | ||
466 | /* | |
467 | * Default handling if a filesystem does not provide a migration function. | |
468 | */ | |
469 | static int fallback_migrate_page(struct address_space *mapping, | |
470 | struct page *newpage, struct page *page) | |
471 | { | |
472 | if (PageDirty(page)) | |
473 | return writeout(mapping, page); | |
474 | ||
475 | /* | |
476 | * Buffers may be managed in a filesystem specific way. | |
477 | * We must have no buffers or drop them. | |
478 | */ | |
479 | if (page_has_private(page) && | |
480 | !try_to_release_page(page, GFP_KERNEL)) | |
481 | return -EAGAIN; | |
482 | ||
483 | return migrate_page(mapping, newpage, page); | |
484 | } | |
485 | ||
486 | /* | |
487 | * Move a page to a newly allocated page | |
488 | * The page is locked and all ptes have been successfully removed. | |
489 | * | |
490 | * The new page will have replaced the old page if this function | |
491 | * is successful. | |
492 | * | |
493 | * Return value: | |
494 | * < 0 - error code | |
495 | * == 0 - success | |
496 | */ | |
497 | static int move_to_new_page(struct page *newpage, struct page *page, | |
498 | int remap_swapcache) | |
499 | { | |
500 | struct address_space *mapping; | |
501 | int rc; | |
502 | ||
503 | /* | |
504 | * Block others from accessing the page when we get around to | |
505 | * establishing additional references. We are the only one | |
506 | * holding a reference to the new page at this point. | |
507 | */ | |
508 | if (!trylock_page(newpage)) | |
509 | BUG(); | |
510 | ||
511 | /* Prepare mapping for the new page.*/ | |
512 | newpage->index = page->index; | |
513 | newpage->mapping = page->mapping; | |
514 | if (PageSwapBacked(page)) | |
515 | SetPageSwapBacked(newpage); | |
516 | ||
517 | mapping = page_mapping(page); | |
518 | if (!mapping) | |
519 | rc = migrate_page(mapping, newpage, page); | |
520 | else if (mapping->a_ops->migratepage) | |
521 | /* | |
522 | * Most pages have a mapping and most filesystems | |
523 | * should provide a migration function. Anonymous | |
524 | * pages are part of swap space which also has its | |
525 | * own migration function. This is the most common | |
526 | * path for page migration. | |
527 | */ | |
528 | rc = mapping->a_ops->migratepage(mapping, | |
529 | newpage, page); | |
530 | else | |
531 | rc = fallback_migrate_page(mapping, newpage, page); | |
532 | ||
533 | if (rc) { | |
534 | newpage->mapping = NULL; | |
535 | } else { | |
536 | if (remap_swapcache) | |
537 | remove_migration_ptes(page, newpage); | |
538 | } | |
539 | ||
540 | unlock_page(newpage); | |
541 | ||
542 | return rc; | |
543 | } | |
544 | ||
545 | /* | |
546 | * Obtain the lock on page, remove all ptes and migrate the page | |
547 | * to the newly allocated page in newpage. | |
548 | */ | |
549 | static int unmap_and_move(new_page_t get_new_page, unsigned long private, | |
550 | struct page *page, int force, int offlining) | |
551 | { | |
552 | int rc = 0; | |
553 | int *result = NULL; | |
554 | struct page *newpage = get_new_page(page, private, &result); | |
555 | int remap_swapcache = 1; | |
556 | int rcu_locked = 0; | |
557 | int charge = 0; | |
558 | struct mem_cgroup *mem = NULL; | |
559 | struct anon_vma *anon_vma = NULL; | |
560 | ||
561 | if (!newpage) | |
562 | return -ENOMEM; | |
563 | ||
564 | if (page_count(page) == 1) { | |
565 | /* page was freed from under us. So we are done. */ | |
566 | goto move_newpage; | |
567 | } | |
568 | ||
569 | /* prepare cgroup just returns 0 or -ENOMEM */ | |
570 | rc = -EAGAIN; | |
571 | ||
572 | if (!trylock_page(page)) { | |
573 | if (!force) | |
574 | goto move_newpage; | |
575 | lock_page(page); | |
576 | } | |
577 | ||
578 | /* | |
579 | * Only memory hotplug's offline_pages() caller has locked out KSM, | |
580 | * and can safely migrate a KSM page. The other cases have skipped | |
581 | * PageKsm along with PageReserved - but it is only now when we have | |
582 | * the page lock that we can be certain it will not go KSM beneath us | |
583 | * (KSM will not upgrade a page from PageAnon to PageKsm when it sees | |
584 | * its pagecount raised, but only here do we take the page lock which | |
585 | * serializes that). | |
586 | */ | |
587 | if (PageKsm(page) && !offlining) { | |
588 | rc = -EBUSY; | |
589 | goto unlock; | |
590 | } | |
591 | ||
592 | /* charge against new page */ | |
593 | charge = mem_cgroup_prepare_migration(page, &mem); | |
594 | if (charge == -ENOMEM) { | |
595 | rc = -ENOMEM; | |
596 | goto unlock; | |
597 | } | |
598 | BUG_ON(charge); | |
599 | ||
600 | if (PageWriteback(page)) { | |
601 | if (!force) | |
602 | goto uncharge; | |
603 | wait_on_page_writeback(page); | |
604 | } | |
605 | /* | |
606 | * By try_to_unmap(), page->mapcount goes down to 0 here. In this case, | |
607 | * we cannot notice that anon_vma is freed while we migrates a page. | |
608 | * This rcu_read_lock() delays freeing anon_vma pointer until the end | |
609 | * of migration. File cache pages are no problem because of page_lock() | |
610 | * File Caches may use write_page() or lock_page() in migration, then, | |
611 | * just care Anon page here. | |
612 | */ | |
613 | if (PageAnon(page)) { | |
614 | rcu_read_lock(); | |
615 | rcu_locked = 1; | |
616 | ||
617 | /* Determine how to safely use anon_vma */ | |
618 | if (!page_mapped(page)) { | |
619 | if (!PageSwapCache(page)) | |
620 | goto rcu_unlock; | |
621 | ||
622 | /* | |
623 | * We cannot be sure that the anon_vma of an unmapped | |
624 | * swapcache page is safe to use because we don't | |
625 | * know in advance if the VMA that this page belonged | |
626 | * to still exists. If the VMA and others sharing the | |
627 | * data have been freed, then the anon_vma could | |
628 | * already be invalid. | |
629 | * | |
630 | * To avoid this possibility, swapcache pages get | |
631 | * migrated but are not remapped when migration | |
632 | * completes | |
633 | */ | |
634 | remap_swapcache = 0; | |
635 | } else { | |
636 | /* | |
637 | * Take a reference count on the anon_vma if the | |
638 | * page is mapped so that it is guaranteed to | |
639 | * exist when the page is remapped later | |
640 | */ | |
641 | anon_vma = page_anon_vma(page); | |
642 | atomic_inc(&anon_vma->external_refcount); | |
643 | } | |
644 | } | |
645 | ||
646 | /* | |
647 | * Corner case handling: | |
648 | * 1. When a new swap-cache page is read into, it is added to the LRU | |
649 | * and treated as swapcache but it has no rmap yet. | |
650 | * Calling try_to_unmap() against a page->mapping==NULL page will | |
651 | * trigger a BUG. So handle it here. | |
652 | * 2. An orphaned page (see truncate_complete_page) might have | |
653 | * fs-private metadata. The page can be picked up due to memory | |
654 | * offlining. Everywhere else except page reclaim, the page is | |
655 | * invisible to the vm, so the page can not be migrated. So try to | |
656 | * free the metadata, so the page can be freed. | |
657 | */ | |
658 | if (!page->mapping) { | |
659 | if (!PageAnon(page) && page_has_private(page)) { | |
660 | /* | |
661 | * Go direct to try_to_free_buffers() here because | |
662 | * a) that's what try_to_release_page() would do anyway | |
663 | * b) we may be under rcu_read_lock() here, so we can't | |
664 | * use GFP_KERNEL which is what try_to_release_page() | |
665 | * needs to be effective. | |
666 | */ | |
667 | try_to_free_buffers(page); | |
668 | goto rcu_unlock; | |
669 | } | |
670 | goto skip_unmap; | |
671 | } | |
672 | ||
673 | /* Establish migration ptes or remove ptes */ | |
674 | try_to_unmap(page, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS); | |
675 | ||
676 | skip_unmap: | |
677 | if (!page_mapped(page)) | |
678 | rc = move_to_new_page(newpage, page, remap_swapcache); | |
679 | ||
680 | if (rc && remap_swapcache) | |
681 | remove_migration_ptes(page, page); | |
682 | rcu_unlock: | |
683 | ||
684 | /* Drop an anon_vma reference if we took one */ | |
685 | if (anon_vma && atomic_dec_and_lock(&anon_vma->external_refcount, &anon_vma->lock)) { | |
686 | int empty = list_empty(&anon_vma->head); | |
687 | spin_unlock(&anon_vma->lock); | |
688 | if (empty) | |
689 | anon_vma_free(anon_vma); | |
690 | } | |
691 | ||
692 | if (rcu_locked) | |
693 | rcu_read_unlock(); | |
694 | uncharge: | |
695 | if (!charge) | |
696 | mem_cgroup_end_migration(mem, page, newpage); | |
697 | unlock: | |
698 | unlock_page(page); | |
699 | ||
700 | if (rc != -EAGAIN) { | |
701 | /* | |
702 | * A page that has been migrated has all references | |
703 | * removed and will be freed. A page that has not been | |
704 | * migrated will have kepts its references and be | |
705 | * restored. | |
706 | */ | |
707 | list_del(&page->lru); | |
708 | dec_zone_page_state(page, NR_ISOLATED_ANON + | |
709 | page_is_file_cache(page)); | |
710 | putback_lru_page(page); | |
711 | } | |
712 | ||
713 | move_newpage: | |
714 | ||
715 | /* | |
716 | * Move the new page to the LRU. If migration was not successful | |
717 | * then this will free the page. | |
718 | */ | |
719 | putback_lru_page(newpage); | |
720 | ||
721 | if (result) { | |
722 | if (rc) | |
723 | *result = rc; | |
724 | else | |
725 | *result = page_to_nid(newpage); | |
726 | } | |
727 | return rc; | |
728 | } | |
729 | ||
730 | /* | |
731 | * migrate_pages | |
732 | * | |
733 | * The function takes one list of pages to migrate and a function | |
734 | * that determines from the page to be migrated and the private data | |
735 | * the target of the move and allocates the page. | |
736 | * | |
737 | * The function returns after 10 attempts or if no pages | |
738 | * are movable anymore because to has become empty | |
739 | * or no retryable pages exist anymore. All pages will be | |
740 | * returned to the LRU or freed. | |
741 | * | |
742 | * Return: Number of pages not migrated or error code. | |
743 | */ | |
744 | int migrate_pages(struct list_head *from, | |
745 | new_page_t get_new_page, unsigned long private, int offlining) | |
746 | { | |
747 | int retry = 1; | |
748 | int nr_failed = 0; | |
749 | int pass = 0; | |
750 | struct page *page; | |
751 | struct page *page2; | |
752 | int swapwrite = current->flags & PF_SWAPWRITE; | |
753 | int rc; | |
754 | ||
755 | if (!swapwrite) | |
756 | current->flags |= PF_SWAPWRITE; | |
757 | ||
758 | for(pass = 0; pass < 10 && retry; pass++) { | |
759 | retry = 0; | |
760 | ||
761 | list_for_each_entry_safe(page, page2, from, lru) { | |
762 | cond_resched(); | |
763 | ||
764 | rc = unmap_and_move(get_new_page, private, | |
765 | page, pass > 2, offlining); | |
766 | ||
767 | switch(rc) { | |
768 | case -ENOMEM: | |
769 | goto out; | |
770 | case -EAGAIN: | |
771 | retry++; | |
772 | break; | |
773 | case 0: | |
774 | break; | |
775 | default: | |
776 | /* Permanent failure */ | |
777 | nr_failed++; | |
778 | break; | |
779 | } | |
780 | } | |
781 | } | |
782 | rc = 0; | |
783 | out: | |
784 | if (!swapwrite) | |
785 | current->flags &= ~PF_SWAPWRITE; | |
786 | ||
787 | putback_lru_pages(from); | |
788 | ||
789 | if (rc) | |
790 | return rc; | |
791 | ||
792 | return nr_failed + retry; | |
793 | } | |
794 | ||
795 | #ifdef CONFIG_NUMA | |
796 | /* | |
797 | * Move a list of individual pages | |
798 | */ | |
799 | struct page_to_node { | |
800 | unsigned long addr; | |
801 | struct page *page; | |
802 | int node; | |
803 | int status; | |
804 | }; | |
805 | ||
806 | static struct page *new_page_node(struct page *p, unsigned long private, | |
807 | int **result) | |
808 | { | |
809 | struct page_to_node *pm = (struct page_to_node *)private; | |
810 | ||
811 | while (pm->node != MAX_NUMNODES && pm->page != p) | |
812 | pm++; | |
813 | ||
814 | if (pm->node == MAX_NUMNODES) | |
815 | return NULL; | |
816 | ||
817 | *result = &pm->status; | |
818 | ||
819 | return alloc_pages_exact_node(pm->node, | |
820 | GFP_HIGHUSER_MOVABLE | GFP_THISNODE, 0); | |
821 | } | |
822 | ||
823 | /* | |
824 | * Move a set of pages as indicated in the pm array. The addr | |
825 | * field must be set to the virtual address of the page to be moved | |
826 | * and the node number must contain a valid target node. | |
827 | * The pm array ends with node = MAX_NUMNODES. | |
828 | */ | |
829 | static int do_move_page_to_node_array(struct mm_struct *mm, | |
830 | struct page_to_node *pm, | |
831 | int migrate_all) | |
832 | { | |
833 | int err; | |
834 | struct page_to_node *pp; | |
835 | LIST_HEAD(pagelist); | |
836 | ||
837 | down_read(&mm->mmap_sem); | |
838 | ||
839 | /* | |
840 | * Build a list of pages to migrate | |
841 | */ | |
842 | for (pp = pm; pp->node != MAX_NUMNODES; pp++) { | |
843 | struct vm_area_struct *vma; | |
844 | struct page *page; | |
845 | ||
846 | err = -EFAULT; | |
847 | vma = find_vma(mm, pp->addr); | |
848 | if (!vma || !vma_migratable(vma)) | |
849 | goto set_status; | |
850 | ||
851 | page = follow_page(vma, pp->addr, FOLL_GET); | |
852 | ||
853 | err = PTR_ERR(page); | |
854 | if (IS_ERR(page)) | |
855 | goto set_status; | |
856 | ||
857 | err = -ENOENT; | |
858 | if (!page) | |
859 | goto set_status; | |
860 | ||
861 | /* Use PageReserved to check for zero page */ | |
862 | if (PageReserved(page) || PageKsm(page)) | |
863 | goto put_and_set; | |
864 | ||
865 | pp->page = page; | |
866 | err = page_to_nid(page); | |
867 | ||
868 | if (err == pp->node) | |
869 | /* | |
870 | * Node already in the right place | |
871 | */ | |
872 | goto put_and_set; | |
873 | ||
874 | err = -EACCES; | |
875 | if (page_mapcount(page) > 1 && | |
876 | !migrate_all) | |
877 | goto put_and_set; | |
878 | ||
879 | err = isolate_lru_page(page); | |
880 | if (!err) { | |
881 | list_add_tail(&page->lru, &pagelist); | |
882 | inc_zone_page_state(page, NR_ISOLATED_ANON + | |
883 | page_is_file_cache(page)); | |
884 | } | |
885 | put_and_set: | |
886 | /* | |
887 | * Either remove the duplicate refcount from | |
888 | * isolate_lru_page() or drop the page ref if it was | |
889 | * not isolated. | |
890 | */ | |
891 | put_page(page); | |
892 | set_status: | |
893 | pp->status = err; | |
894 | } | |
895 | ||
896 | err = 0; | |
897 | if (!list_empty(&pagelist)) | |
898 | err = migrate_pages(&pagelist, new_page_node, | |
899 | (unsigned long)pm, 0); | |
900 | ||
901 | up_read(&mm->mmap_sem); | |
902 | return err; | |
903 | } | |
904 | ||
905 | /* | |
906 | * Migrate an array of page address onto an array of nodes and fill | |
907 | * the corresponding array of status. | |
908 | */ | |
909 | static int do_pages_move(struct mm_struct *mm, struct task_struct *task, | |
910 | unsigned long nr_pages, | |
911 | const void __user * __user *pages, | |
912 | const int __user *nodes, | |
913 | int __user *status, int flags) | |
914 | { | |
915 | struct page_to_node *pm; | |
916 | nodemask_t task_nodes; | |
917 | unsigned long chunk_nr_pages; | |
918 | unsigned long chunk_start; | |
919 | int err; | |
920 | ||
921 | task_nodes = cpuset_mems_allowed(task); | |
922 | ||
923 | err = -ENOMEM; | |
924 | pm = (struct page_to_node *)__get_free_page(GFP_KERNEL); | |
925 | if (!pm) | |
926 | goto out; | |
927 | ||
928 | migrate_prep(); | |
929 | ||
930 | /* | |
931 | * Store a chunk of page_to_node array in a page, | |
932 | * but keep the last one as a marker | |
933 | */ | |
934 | chunk_nr_pages = (PAGE_SIZE / sizeof(struct page_to_node)) - 1; | |
935 | ||
936 | for (chunk_start = 0; | |
937 | chunk_start < nr_pages; | |
938 | chunk_start += chunk_nr_pages) { | |
939 | int j; | |
940 | ||
941 | if (chunk_start + chunk_nr_pages > nr_pages) | |
942 | chunk_nr_pages = nr_pages - chunk_start; | |
943 | ||
944 | /* fill the chunk pm with addrs and nodes from user-space */ | |
945 | for (j = 0; j < chunk_nr_pages; j++) { | |
946 | const void __user *p; | |
947 | int node; | |
948 | ||
949 | err = -EFAULT; | |
950 | if (get_user(p, pages + j + chunk_start)) | |
951 | goto out_pm; | |
952 | pm[j].addr = (unsigned long) p; | |
953 | ||
954 | if (get_user(node, nodes + j + chunk_start)) | |
955 | goto out_pm; | |
956 | ||
957 | err = -ENODEV; | |
958 | if (node < 0 || node >= MAX_NUMNODES) | |
959 | goto out_pm; | |
960 | ||
961 | if (!node_state(node, N_HIGH_MEMORY)) | |
962 | goto out_pm; | |
963 | ||
964 | err = -EACCES; | |
965 | if (!node_isset(node, task_nodes)) | |
966 | goto out_pm; | |
967 | ||
968 | pm[j].node = node; | |
969 | } | |
970 | ||
971 | /* End marker for this chunk */ | |
972 | pm[chunk_nr_pages].node = MAX_NUMNODES; | |
973 | ||
974 | /* Migrate this chunk */ | |
975 | err = do_move_page_to_node_array(mm, pm, | |
976 | flags & MPOL_MF_MOVE_ALL); | |
977 | if (err < 0) | |
978 | goto out_pm; | |
979 | ||
980 | /* Return status information */ | |
981 | for (j = 0; j < chunk_nr_pages; j++) | |
982 | if (put_user(pm[j].status, status + j + chunk_start)) { | |
983 | err = -EFAULT; | |
984 | goto out_pm; | |
985 | } | |
986 | } | |
987 | err = 0; | |
988 | ||
989 | out_pm: | |
990 | free_page((unsigned long)pm); | |
991 | out: | |
992 | return err; | |
993 | } | |
994 | ||
995 | /* | |
996 | * Determine the nodes of an array of pages and store it in an array of status. | |
997 | */ | |
998 | static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages, | |
999 | const void __user **pages, int *status) | |
1000 | { | |
1001 | unsigned long i; | |
1002 | ||
1003 | down_read(&mm->mmap_sem); | |
1004 | ||
1005 | for (i = 0; i < nr_pages; i++) { | |
1006 | unsigned long addr = (unsigned long)(*pages); | |
1007 | struct vm_area_struct *vma; | |
1008 | struct page *page; | |
1009 | int err = -EFAULT; | |
1010 | ||
1011 | vma = find_vma(mm, addr); | |
1012 | if (!vma) | |
1013 | goto set_status; | |
1014 | ||
1015 | page = follow_page(vma, addr, 0); | |
1016 | ||
1017 | err = PTR_ERR(page); | |
1018 | if (IS_ERR(page)) | |
1019 | goto set_status; | |
1020 | ||
1021 | err = -ENOENT; | |
1022 | /* Use PageReserved to check for zero page */ | |
1023 | if (!page || PageReserved(page) || PageKsm(page)) | |
1024 | goto set_status; | |
1025 | ||
1026 | err = page_to_nid(page); | |
1027 | set_status: | |
1028 | *status = err; | |
1029 | ||
1030 | pages++; | |
1031 | status++; | |
1032 | } | |
1033 | ||
1034 | up_read(&mm->mmap_sem); | |
1035 | } | |
1036 | ||
1037 | /* | |
1038 | * Determine the nodes of a user array of pages and store it in | |
1039 | * a user array of status. | |
1040 | */ | |
1041 | static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages, | |
1042 | const void __user * __user *pages, | |
1043 | int __user *status) | |
1044 | { | |
1045 | #define DO_PAGES_STAT_CHUNK_NR 16 | |
1046 | const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR]; | |
1047 | int chunk_status[DO_PAGES_STAT_CHUNK_NR]; | |
1048 | ||
1049 | while (nr_pages) { | |
1050 | unsigned long chunk_nr; | |
1051 | ||
1052 | chunk_nr = nr_pages; | |
1053 | if (chunk_nr > DO_PAGES_STAT_CHUNK_NR) | |
1054 | chunk_nr = DO_PAGES_STAT_CHUNK_NR; | |
1055 | ||
1056 | if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages))) | |
1057 | break; | |
1058 | ||
1059 | do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status); | |
1060 | ||
1061 | if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status))) | |
1062 | break; | |
1063 | ||
1064 | pages += chunk_nr; | |
1065 | status += chunk_nr; | |
1066 | nr_pages -= chunk_nr; | |
1067 | } | |
1068 | return nr_pages ? -EFAULT : 0; | |
1069 | } | |
1070 | ||
1071 | /* | |
1072 | * Move a list of pages in the address space of the currently executing | |
1073 | * process. | |
1074 | */ | |
1075 | SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages, | |
1076 | const void __user * __user *, pages, | |
1077 | const int __user *, nodes, | |
1078 | int __user *, status, int, flags) | |
1079 | { | |
1080 | const struct cred *cred = current_cred(), *tcred; | |
1081 | struct task_struct *task; | |
1082 | struct mm_struct *mm; | |
1083 | int err; | |
1084 | ||
1085 | /* Check flags */ | |
1086 | if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL)) | |
1087 | return -EINVAL; | |
1088 | ||
1089 | if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE)) | |
1090 | return -EPERM; | |
1091 | ||
1092 | /* Find the mm_struct */ | |
1093 | read_lock(&tasklist_lock); | |
1094 | task = pid ? find_task_by_vpid(pid) : current; | |
1095 | if (!task) { | |
1096 | read_unlock(&tasklist_lock); | |
1097 | return -ESRCH; | |
1098 | } | |
1099 | mm = get_task_mm(task); | |
1100 | read_unlock(&tasklist_lock); | |
1101 | ||
1102 | if (!mm) | |
1103 | return -EINVAL; | |
1104 | ||
1105 | /* | |
1106 | * Check if this process has the right to modify the specified | |
1107 | * process. The right exists if the process has administrative | |
1108 | * capabilities, superuser privileges or the same | |
1109 | * userid as the target process. | |
1110 | */ | |
1111 | rcu_read_lock(); | |
1112 | tcred = __task_cred(task); | |
1113 | if (cred->euid != tcred->suid && cred->euid != tcred->uid && | |
1114 | cred->uid != tcred->suid && cred->uid != tcred->uid && | |
1115 | !capable(CAP_SYS_NICE)) { | |
1116 | rcu_read_unlock(); | |
1117 | err = -EPERM; | |
1118 | goto out; | |
1119 | } | |
1120 | rcu_read_unlock(); | |
1121 | ||
1122 | err = security_task_movememory(task); | |
1123 | if (err) | |
1124 | goto out; | |
1125 | ||
1126 | if (nodes) { | |
1127 | err = do_pages_move(mm, task, nr_pages, pages, nodes, status, | |
1128 | flags); | |
1129 | } else { | |
1130 | err = do_pages_stat(mm, nr_pages, pages, status); | |
1131 | } | |
1132 | ||
1133 | out: | |
1134 | mmput(mm); | |
1135 | return err; | |
1136 | } | |
1137 | ||
1138 | /* | |
1139 | * Call migration functions in the vma_ops that may prepare | |
1140 | * memory in a vm for migration. migration functions may perform | |
1141 | * the migration for vmas that do not have an underlying page struct. | |
1142 | */ | |
1143 | int migrate_vmas(struct mm_struct *mm, const nodemask_t *to, | |
1144 | const nodemask_t *from, unsigned long flags) | |
1145 | { | |
1146 | struct vm_area_struct *vma; | |
1147 | int err = 0; | |
1148 | ||
1149 | for (vma = mm->mmap; vma && !err; vma = vma->vm_next) { | |
1150 | if (vma->vm_ops && vma->vm_ops->migrate) { | |
1151 | err = vma->vm_ops->migrate(vma, to, from, flags); | |
1152 | if (err) | |
1153 | break; | |
1154 | } | |
1155 | } | |
1156 | return err; | |
1157 | } | |
1158 | #endif |