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