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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 | dec_zone_page_state(page, NR_ISOLATED_ANON + | |
71 | page_is_file_cache(page)); | |
72 | putback_lru_page(page); | |
73 | count++; | |
74 | } | |
75 | return count; | |
76 | } | |
77 | ||
78 | /* | |
79 | * Restore a potential migration pte to a working pte entry | |
80 | */ | |
81 | static void remove_migration_pte(struct vm_area_struct *vma, | |
82 | struct page *old, struct page *new) | |
83 | { | |
84 | struct mm_struct *mm = vma->vm_mm; | |
85 | swp_entry_t entry; | |
86 | pgd_t *pgd; | |
87 | pud_t *pud; | |
88 | pmd_t *pmd; | |
89 | pte_t *ptep, pte; | |
90 | spinlock_t *ptl; | |
91 | unsigned long addr = page_address_in_vma(new, vma); | |
92 | ||
93 | if (addr == -EFAULT) | |
94 | return; | |
95 | ||
96 | pgd = pgd_offset(mm, addr); | |
97 | if (!pgd_present(*pgd)) | |
98 | return; | |
99 | ||
100 | pud = pud_offset(pgd, addr); | |
101 | if (!pud_present(*pud)) | |
102 | return; | |
103 | ||
104 | pmd = pmd_offset(pud, addr); | |
105 | if (!pmd_present(*pmd)) | |
106 | return; | |
107 | ||
108 | ptep = pte_offset_map(pmd, addr); | |
109 | ||
110 | if (!is_swap_pte(*ptep)) { | |
111 | pte_unmap(ptep); | |
112 | return; | |
113 | } | |
114 | ||
115 | ptl = pte_lockptr(mm, pmd); | |
116 | spin_lock(ptl); | |
117 | pte = *ptep; | |
118 | if (!is_swap_pte(pte)) | |
119 | goto out; | |
120 | ||
121 | entry = pte_to_swp_entry(pte); | |
122 | ||
123 | if (!is_migration_entry(entry) || migration_entry_to_page(entry) != old) | |
124 | goto out; | |
125 | ||
126 | get_page(new); | |
127 | pte = pte_mkold(mk_pte(new, vma->vm_page_prot)); | |
128 | if (is_write_migration_entry(entry)) | |
129 | pte = pte_mkwrite(pte); | |
130 | flush_cache_page(vma, addr, pte_pfn(pte)); | |
131 | set_pte_at(mm, addr, ptep, pte); | |
132 | ||
133 | if (PageAnon(new)) | |
134 | page_add_anon_rmap(new, vma, addr); | |
135 | else | |
136 | page_add_file_rmap(new); | |
137 | ||
138 | /* No need to invalidate - it was non-present before */ | |
139 | update_mmu_cache(vma, addr, pte); | |
140 | ||
141 | out: | |
142 | pte_unmap_unlock(ptep, ptl); | |
143 | } | |
144 | ||
145 | /* | |
146 | * Note that remove_file_migration_ptes will only work on regular mappings, | |
147 | * Nonlinear mappings do not use migration entries. | |
148 | */ | |
149 | static void remove_file_migration_ptes(struct page *old, struct page *new) | |
150 | { | |
151 | struct vm_area_struct *vma; | |
152 | struct address_space *mapping = new->mapping; | |
153 | struct prio_tree_iter iter; | |
154 | pgoff_t pgoff = new->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); | |
155 | ||
156 | if (!mapping) | |
157 | return; | |
158 | ||
159 | spin_lock(&mapping->i_mmap_lock); | |
160 | ||
161 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) | |
162 | remove_migration_pte(vma, old, new); | |
163 | ||
164 | spin_unlock(&mapping->i_mmap_lock); | |
165 | } | |
166 | ||
167 | /* | |
168 | * Must hold mmap_sem lock on at least one of the vmas containing | |
169 | * the page so that the anon_vma cannot vanish. | |
170 | */ | |
171 | static void remove_anon_migration_ptes(struct page *old, struct page *new) | |
172 | { | |
173 | struct anon_vma *anon_vma; | |
174 | struct vm_area_struct *vma; | |
175 | unsigned long mapping; | |
176 | ||
177 | mapping = (unsigned long)new->mapping; | |
178 | ||
179 | if (!mapping || (mapping & PAGE_MAPPING_ANON) == 0) | |
180 | return; | |
181 | ||
182 | /* | |
183 | * We hold the mmap_sem lock. So no need to call page_lock_anon_vma. | |
184 | */ | |
185 | anon_vma = (struct anon_vma *) (mapping - PAGE_MAPPING_ANON); | |
186 | spin_lock(&anon_vma->lock); | |
187 | ||
188 | list_for_each_entry(vma, &anon_vma->head, anon_vma_node) | |
189 | remove_migration_pte(vma, old, new); | |
190 | ||
191 | spin_unlock(&anon_vma->lock); | |
192 | } | |
193 | ||
194 | /* | |
195 | * Get rid of all migration entries and replace them by | |
196 | * references to the indicated page. | |
197 | */ | |
198 | static void remove_migration_ptes(struct page *old, struct page *new) | |
199 | { | |
200 | if (PageAnon(new)) | |
201 | remove_anon_migration_ptes(old, new); | |
202 | else | |
203 | remove_file_migration_ptes(old, new); | |
204 | } | |
205 | ||
206 | /* | |
207 | * Something used the pte of a page under migration. We need to | |
208 | * get to the page and wait until migration is finished. | |
209 | * When we return from this function the fault will be retried. | |
210 | * | |
211 | * This function is called from do_swap_page(). | |
212 | */ | |
213 | void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, | |
214 | unsigned long address) | |
215 | { | |
216 | pte_t *ptep, pte; | |
217 | spinlock_t *ptl; | |
218 | swp_entry_t entry; | |
219 | struct page *page; | |
220 | ||
221 | ptep = pte_offset_map_lock(mm, pmd, address, &ptl); | |
222 | pte = *ptep; | |
223 | if (!is_swap_pte(pte)) | |
224 | goto out; | |
225 | ||
226 | entry = pte_to_swp_entry(pte); | |
227 | if (!is_migration_entry(entry)) | |
228 | goto out; | |
229 | ||
230 | page = migration_entry_to_page(entry); | |
231 | ||
232 | /* | |
233 | * Once radix-tree replacement of page migration started, page_count | |
234 | * *must* be zero. And, we don't want to call wait_on_page_locked() | |
235 | * against a page without get_page(). | |
236 | * So, we use get_page_unless_zero(), here. Even failed, page fault | |
237 | * will occur again. | |
238 | */ | |
239 | if (!get_page_unless_zero(page)) | |
240 | goto out; | |
241 | pte_unmap_unlock(ptep, ptl); | |
242 | wait_on_page_locked(page); | |
243 | put_page(page); | |
244 | return; | |
245 | out: | |
246 | pte_unmap_unlock(ptep, ptl); | |
247 | } | |
248 | ||
249 | /* | |
250 | * Replace the page in the mapping. | |
251 | * | |
252 | * The number of remaining references must be: | |
253 | * 1 for anonymous pages without a mapping | |
254 | * 2 for pages with a mapping | |
255 | * 3 for pages with a mapping and PagePrivate/PagePrivate2 set. | |
256 | */ | |
257 | static int migrate_page_move_mapping(struct address_space *mapping, | |
258 | struct page *newpage, struct page *page) | |
259 | { | |
260 | int expected_count; | |
261 | void **pslot; | |
262 | ||
263 | if (!mapping) { | |
264 | /* Anonymous page without mapping */ | |
265 | if (page_count(page) != 1) | |
266 | return -EAGAIN; | |
267 | return 0; | |
268 | } | |
269 | ||
270 | spin_lock_irq(&mapping->tree_lock); | |
271 | ||
272 | pslot = radix_tree_lookup_slot(&mapping->page_tree, | |
273 | page_index(page)); | |
274 | ||
275 | expected_count = 2 + page_has_private(page); | |
276 | if (page_count(page) != expected_count || | |
277 | (struct page *)radix_tree_deref_slot(pslot) != page) { | |
278 | spin_unlock_irq(&mapping->tree_lock); | |
279 | return -EAGAIN; | |
280 | } | |
281 | ||
282 | if (!page_freeze_refs(page, expected_count)) { | |
283 | spin_unlock_irq(&mapping->tree_lock); | |
284 | return -EAGAIN; | |
285 | } | |
286 | ||
287 | /* | |
288 | * Now we know that no one else is looking at the page. | |
289 | */ | |
290 | get_page(newpage); /* add cache reference */ | |
291 | if (PageSwapCache(page)) { | |
292 | SetPageSwapCache(newpage); | |
293 | set_page_private(newpage, page_private(page)); | |
294 | } | |
295 | ||
296 | radix_tree_replace_slot(pslot, newpage); | |
297 | ||
298 | page_unfreeze_refs(page, expected_count); | |
299 | /* | |
300 | * Drop cache reference from old page. | |
301 | * We know this isn't the last reference. | |
302 | */ | |
303 | __put_page(page); | |
304 | ||
305 | /* | |
306 | * If moved to a different zone then also account | |
307 | * the page for that zone. Other VM counters will be | |
308 | * taken care of when we establish references to the | |
309 | * new page and drop references to the old page. | |
310 | * | |
311 | * Note that anonymous pages are accounted for | |
312 | * via NR_FILE_PAGES and NR_ANON_PAGES if they | |
313 | * are mapped to swap space. | |
314 | */ | |
315 | __dec_zone_page_state(page, NR_FILE_PAGES); | |
316 | __inc_zone_page_state(newpage, NR_FILE_PAGES); | |
317 | if (PageSwapBacked(page)) { | |
318 | __dec_zone_page_state(page, NR_SHMEM); | |
319 | __inc_zone_page_state(newpage, NR_SHMEM); | |
320 | } | |
321 | spin_unlock_irq(&mapping->tree_lock); | |
322 | ||
323 | return 0; | |
324 | } | |
325 | ||
326 | /* | |
327 | * Copy the page to its new location | |
328 | */ | |
329 | static void migrate_page_copy(struct page *newpage, struct page *page) | |
330 | { | |
331 | int anon; | |
332 | ||
333 | copy_highpage(newpage, page); | |
334 | ||
335 | if (PageError(page)) | |
336 | SetPageError(newpage); | |
337 | if (PageReferenced(page)) | |
338 | SetPageReferenced(newpage); | |
339 | if (PageUptodate(page)) | |
340 | SetPageUptodate(newpage); | |
341 | if (TestClearPageActive(page)) { | |
342 | VM_BUG_ON(PageUnevictable(page)); | |
343 | SetPageActive(newpage); | |
344 | } else | |
345 | unevictable_migrate_page(newpage, page); | |
346 | if (PageChecked(page)) | |
347 | SetPageChecked(newpage); | |
348 | if (PageMappedToDisk(page)) | |
349 | SetPageMappedToDisk(newpage); | |
350 | ||
351 | if (PageDirty(page)) { | |
352 | clear_page_dirty_for_io(page); | |
353 | /* | |
354 | * Want to mark the page and the radix tree as dirty, and | |
355 | * redo the accounting that clear_page_dirty_for_io undid, | |
356 | * but we can't use set_page_dirty because that function | |
357 | * is actually a signal that all of the page has become dirty. | |
358 | * Wheras only part of our page may be dirty. | |
359 | */ | |
360 | __set_page_dirty_nobuffers(newpage); | |
361 | } | |
362 | ||
363 | mlock_migrate_page(newpage, page); | |
364 | ||
365 | ClearPageSwapCache(page); | |
366 | ClearPagePrivate(page); | |
367 | set_page_private(page, 0); | |
368 | /* page->mapping contains a flag for PageAnon() */ | |
369 | anon = PageAnon(page); | |
370 | page->mapping = NULL; | |
371 | ||
372 | /* | |
373 | * If any waiters have accumulated on the new page then | |
374 | * wake them up. | |
375 | */ | |
376 | if (PageWriteback(newpage)) | |
377 | end_page_writeback(newpage); | |
378 | } | |
379 | ||
380 | /************************************************************ | |
381 | * Migration functions | |
382 | ***********************************************************/ | |
383 | ||
384 | /* Always fail migration. Used for mappings that are not movable */ | |
385 | int fail_migrate_page(struct address_space *mapping, | |
386 | struct page *newpage, struct page *page) | |
387 | { | |
388 | return -EIO; | |
389 | } | |
390 | EXPORT_SYMBOL(fail_migrate_page); | |
391 | ||
392 | /* | |
393 | * Common logic to directly migrate a single page suitable for | |
394 | * pages that do not use PagePrivate/PagePrivate2. | |
395 | * | |
396 | * Pages are locked upon entry and exit. | |
397 | */ | |
398 | int migrate_page(struct address_space *mapping, | |
399 | struct page *newpage, struct page *page) | |
400 | { | |
401 | int rc; | |
402 | ||
403 | BUG_ON(PageWriteback(page)); /* Writeback must be complete */ | |
404 | ||
405 | rc = migrate_page_move_mapping(mapping, newpage, page); | |
406 | ||
407 | if (rc) | |
408 | return rc; | |
409 | ||
410 | migrate_page_copy(newpage, page); | |
411 | return 0; | |
412 | } | |
413 | EXPORT_SYMBOL(migrate_page); | |
414 | ||
415 | #ifdef CONFIG_BLOCK | |
416 | /* | |
417 | * Migration function for pages with buffers. This function can only be used | |
418 | * if the underlying filesystem guarantees that no other references to "page" | |
419 | * exist. | |
420 | */ | |
421 | int buffer_migrate_page(struct address_space *mapping, | |
422 | struct page *newpage, struct page *page) | |
423 | { | |
424 | struct buffer_head *bh, *head; | |
425 | int rc; | |
426 | ||
427 | if (!page_has_buffers(page)) | |
428 | return migrate_page(mapping, newpage, page); | |
429 | ||
430 | head = page_buffers(page); | |
431 | ||
432 | rc = migrate_page_move_mapping(mapping, newpage, page); | |
433 | ||
434 | if (rc) | |
435 | return rc; | |
436 | ||
437 | bh = head; | |
438 | do { | |
439 | get_bh(bh); | |
440 | lock_buffer(bh); | |
441 | bh = bh->b_this_page; | |
442 | ||
443 | } while (bh != head); | |
444 | ||
445 | ClearPagePrivate(page); | |
446 | set_page_private(newpage, page_private(page)); | |
447 | set_page_private(page, 0); | |
448 | put_page(page); | |
449 | get_page(newpage); | |
450 | ||
451 | bh = head; | |
452 | do { | |
453 | set_bh_page(bh, newpage, bh_offset(bh)); | |
454 | bh = bh->b_this_page; | |
455 | ||
456 | } while (bh != head); | |
457 | ||
458 | SetPagePrivate(newpage); | |
459 | ||
460 | migrate_page_copy(newpage, page); | |
461 | ||
462 | bh = head; | |
463 | do { | |
464 | unlock_buffer(bh); | |
465 | put_bh(bh); | |
466 | bh = bh->b_this_page; | |
467 | ||
468 | } while (bh != head); | |
469 | ||
470 | return 0; | |
471 | } | |
472 | EXPORT_SYMBOL(buffer_migrate_page); | |
473 | #endif | |
474 | ||
475 | /* | |
476 | * Writeback a page to clean the dirty state | |
477 | */ | |
478 | static int writeout(struct address_space *mapping, struct page *page) | |
479 | { | |
480 | struct writeback_control wbc = { | |
481 | .sync_mode = WB_SYNC_NONE, | |
482 | .nr_to_write = 1, | |
483 | .range_start = 0, | |
484 | .range_end = LLONG_MAX, | |
485 | .nonblocking = 1, | |
486 | .for_reclaim = 1 | |
487 | }; | |
488 | int rc; | |
489 | ||
490 | if (!mapping->a_ops->writepage) | |
491 | /* No write method for the address space */ | |
492 | return -EINVAL; | |
493 | ||
494 | if (!clear_page_dirty_for_io(page)) | |
495 | /* Someone else already triggered a write */ | |
496 | return -EAGAIN; | |
497 | ||
498 | /* | |
499 | * A dirty page may imply that the underlying filesystem has | |
500 | * the page on some queue. So the page must be clean for | |
501 | * migration. Writeout may mean we loose the lock and the | |
502 | * page state is no longer what we checked for earlier. | |
503 | * At this point we know that the migration attempt cannot | |
504 | * be successful. | |
505 | */ | |
506 | remove_migration_ptes(page, page); | |
507 | ||
508 | rc = mapping->a_ops->writepage(page, &wbc); | |
509 | ||
510 | if (rc != AOP_WRITEPAGE_ACTIVATE) | |
511 | /* unlocked. Relock */ | |
512 | lock_page(page); | |
513 | ||
514 | return (rc < 0) ? -EIO : -EAGAIN; | |
515 | } | |
516 | ||
517 | /* | |
518 | * Default handling if a filesystem does not provide a migration function. | |
519 | */ | |
520 | static int fallback_migrate_page(struct address_space *mapping, | |
521 | struct page *newpage, struct page *page) | |
522 | { | |
523 | if (PageDirty(page)) | |
524 | return writeout(mapping, page); | |
525 | ||
526 | /* | |
527 | * Buffers may be managed in a filesystem specific way. | |
528 | * We must have no buffers or drop them. | |
529 | */ | |
530 | if (page_has_private(page) && | |
531 | !try_to_release_page(page, GFP_KERNEL)) | |
532 | return -EAGAIN; | |
533 | ||
534 | return migrate_page(mapping, newpage, page); | |
535 | } | |
536 | ||
537 | /* | |
538 | * Move a page to a newly allocated page | |
539 | * The page is locked and all ptes have been successfully removed. | |
540 | * | |
541 | * The new page will have replaced the old page if this function | |
542 | * is successful. | |
543 | * | |
544 | * Return value: | |
545 | * < 0 - error code | |
546 | * == 0 - success | |
547 | */ | |
548 | static int move_to_new_page(struct page *newpage, struct page *page) | |
549 | { | |
550 | struct address_space *mapping; | |
551 | int rc; | |
552 | ||
553 | /* | |
554 | * Block others from accessing the page when we get around to | |
555 | * establishing additional references. We are the only one | |
556 | * holding a reference to the new page at this point. | |
557 | */ | |
558 | if (!trylock_page(newpage)) | |
559 | BUG(); | |
560 | ||
561 | /* Prepare mapping for the new page.*/ | |
562 | newpage->index = page->index; | |
563 | newpage->mapping = page->mapping; | |
564 | if (PageSwapBacked(page)) | |
565 | SetPageSwapBacked(newpage); | |
566 | ||
567 | mapping = page_mapping(page); | |
568 | if (!mapping) | |
569 | rc = migrate_page(mapping, newpage, page); | |
570 | else if (mapping->a_ops->migratepage) | |
571 | /* | |
572 | * Most pages have a mapping and most filesystems | |
573 | * should provide a migration function. Anonymous | |
574 | * pages are part of swap space which also has its | |
575 | * own migration function. This is the most common | |
576 | * path for page migration. | |
577 | */ | |
578 | rc = mapping->a_ops->migratepage(mapping, | |
579 | newpage, page); | |
580 | else | |
581 | rc = fallback_migrate_page(mapping, newpage, page); | |
582 | ||
583 | if (!rc) { | |
584 | remove_migration_ptes(page, newpage); | |
585 | } else | |
586 | newpage->mapping = NULL; | |
587 | ||
588 | unlock_page(newpage); | |
589 | ||
590 | return rc; | |
591 | } | |
592 | ||
593 | /* | |
594 | * Obtain the lock on page, remove all ptes and migrate the page | |
595 | * to the newly allocated page in newpage. | |
596 | */ | |
597 | static int unmap_and_move(new_page_t get_new_page, unsigned long private, | |
598 | struct page *page, int force) | |
599 | { | |
600 | int rc = 0; | |
601 | int *result = NULL; | |
602 | struct page *newpage = get_new_page(page, private, &result); | |
603 | int rcu_locked = 0; | |
604 | int charge = 0; | |
605 | struct mem_cgroup *mem; | |
606 | ||
607 | if (!newpage) | |
608 | return -ENOMEM; | |
609 | ||
610 | if (page_count(page) == 1) { | |
611 | /* page was freed from under us. So we are done. */ | |
612 | goto move_newpage; | |
613 | } | |
614 | ||
615 | /* prepare cgroup just returns 0 or -ENOMEM */ | |
616 | rc = -EAGAIN; | |
617 | ||
618 | if (!trylock_page(page)) { | |
619 | if (!force) | |
620 | goto move_newpage; | |
621 | lock_page(page); | |
622 | } | |
623 | ||
624 | /* charge against new page */ | |
625 | charge = mem_cgroup_prepare_migration(page, &mem); | |
626 | if (charge == -ENOMEM) { | |
627 | rc = -ENOMEM; | |
628 | goto unlock; | |
629 | } | |
630 | BUG_ON(charge); | |
631 | ||
632 | if (PageWriteback(page)) { | |
633 | if (!force) | |
634 | goto uncharge; | |
635 | wait_on_page_writeback(page); | |
636 | } | |
637 | /* | |
638 | * By try_to_unmap(), page->mapcount goes down to 0 here. In this case, | |
639 | * we cannot notice that anon_vma is freed while we migrates a page. | |
640 | * This rcu_read_lock() delays freeing anon_vma pointer until the end | |
641 | * of migration. File cache pages are no problem because of page_lock() | |
642 | * File Caches may use write_page() or lock_page() in migration, then, | |
643 | * just care Anon page here. | |
644 | */ | |
645 | if (PageAnon(page)) { | |
646 | rcu_read_lock(); | |
647 | rcu_locked = 1; | |
648 | } | |
649 | ||
650 | /* | |
651 | * Corner case handling: | |
652 | * 1. When a new swap-cache page is read into, it is added to the LRU | |
653 | * and treated as swapcache but it has no rmap yet. | |
654 | * Calling try_to_unmap() against a page->mapping==NULL page will | |
655 | * trigger a BUG. So handle it here. | |
656 | * 2. An orphaned page (see truncate_complete_page) might have | |
657 | * fs-private metadata. The page can be picked up due to memory | |
658 | * offlining. Everywhere else except page reclaim, the page is | |
659 | * invisible to the vm, so the page can not be migrated. So try to | |
660 | * free the metadata, so the page can be freed. | |
661 | */ | |
662 | if (!page->mapping) { | |
663 | if (!PageAnon(page) && page_has_private(page)) { | |
664 | /* | |
665 | * Go direct to try_to_free_buffers() here because | |
666 | * a) that's what try_to_release_page() would do anyway | |
667 | * b) we may be under rcu_read_lock() here, so we can't | |
668 | * use GFP_KERNEL which is what try_to_release_page() | |
669 | * needs to be effective. | |
670 | */ | |
671 | try_to_free_buffers(page); | |
672 | goto rcu_unlock; | |
673 | } | |
674 | goto skip_unmap; | |
675 | } | |
676 | ||
677 | /* Establish migration ptes or remove ptes */ | |
678 | try_to_unmap(page, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS); | |
679 | ||
680 | skip_unmap: | |
681 | if (!page_mapped(page)) | |
682 | rc = move_to_new_page(newpage, page); | |
683 | ||
684 | if (rc) | |
685 | remove_migration_ptes(page, page); | |
686 | rcu_unlock: | |
687 | if (rcu_locked) | |
688 | rcu_read_unlock(); | |
689 | uncharge: | |
690 | if (!charge) | |
691 | mem_cgroup_end_migration(mem, page, newpage); | |
692 | unlock: | |
693 | unlock_page(page); | |
694 | ||
695 | if (rc != -EAGAIN) { | |
696 | /* | |
697 | * A page that has been migrated has all references | |
698 | * removed and will be freed. A page that has not been | |
699 | * migrated will have kepts its references and be | |
700 | * restored. | |
701 | */ | |
702 | list_del(&page->lru); | |
703 | dec_zone_page_state(page, NR_ISOLATED_ANON + | |
704 | page_is_file_cache(page)); | |
705 | putback_lru_page(page); | |
706 | } | |
707 | ||
708 | move_newpage: | |
709 | ||
710 | /* | |
711 | * Move the new page to the LRU. If migration was not successful | |
712 | * then this will free the page. | |
713 | */ | |
714 | putback_lru_page(newpage); | |
715 | ||
716 | if (result) { | |
717 | if (rc) | |
718 | *result = rc; | |
719 | else | |
720 | *result = page_to_nid(newpage); | |
721 | } | |
722 | return rc; | |
723 | } | |
724 | ||
725 | /* | |
726 | * migrate_pages | |
727 | * | |
728 | * The function takes one list of pages to migrate and a function | |
729 | * that determines from the page to be migrated and the private data | |
730 | * the target of the move and allocates the page. | |
731 | * | |
732 | * The function returns after 10 attempts or if no pages | |
733 | * are movable anymore because to has become empty | |
734 | * or no retryable pages exist anymore. All pages will be | |
735 | * returned to the LRU or freed. | |
736 | * | |
737 | * Return: Number of pages not migrated or error code. | |
738 | */ | |
739 | int migrate_pages(struct list_head *from, | |
740 | new_page_t get_new_page, unsigned long private) | |
741 | { | |
742 | int retry = 1; | |
743 | int nr_failed = 0; | |
744 | int pass = 0; | |
745 | struct page *page; | |
746 | struct page *page2; | |
747 | int swapwrite = current->flags & PF_SWAPWRITE; | |
748 | int rc; | |
749 | unsigned long flags; | |
750 | ||
751 | local_irq_save(flags); | |
752 | list_for_each_entry(page, from, lru) | |
753 | __inc_zone_page_state(page, NR_ISOLATED_ANON + | |
754 | page_is_file_cache(page)); | |
755 | local_irq_restore(flags); | |
756 | ||
757 | if (!swapwrite) | |
758 | current->flags |= PF_SWAPWRITE; | |
759 | ||
760 | for(pass = 0; pass < 10 && retry; pass++) { | |
761 | retry = 0; | |
762 | ||
763 | list_for_each_entry_safe(page, page2, from, lru) { | |
764 | cond_resched(); | |
765 | ||
766 | rc = unmap_and_move(get_new_page, private, | |
767 | page, pass > 2); | |
768 | ||
769 | switch(rc) { | |
770 | case -ENOMEM: | |
771 | goto out; | |
772 | case -EAGAIN: | |
773 | retry++; | |
774 | break; | |
775 | case 0: | |
776 | break; | |
777 | default: | |
778 | /* Permanent failure */ | |
779 | nr_failed++; | |
780 | break; | |
781 | } | |
782 | } | |
783 | } | |
784 | rc = 0; | |
785 | out: | |
786 | if (!swapwrite) | |
787 | current->flags &= ~PF_SWAPWRITE; | |
788 | ||
789 | putback_lru_pages(from); | |
790 | ||
791 | if (rc) | |
792 | return rc; | |
793 | ||
794 | return nr_failed + retry; | |
795 | } | |
796 | ||
797 | #ifdef CONFIG_NUMA | |
798 | /* | |
799 | * Move a list of individual pages | |
800 | */ | |
801 | struct page_to_node { | |
802 | unsigned long addr; | |
803 | struct page *page; | |
804 | int node; | |
805 | int status; | |
806 | }; | |
807 | ||
808 | static struct page *new_page_node(struct page *p, unsigned long private, | |
809 | int **result) | |
810 | { | |
811 | struct page_to_node *pm = (struct page_to_node *)private; | |
812 | ||
813 | while (pm->node != MAX_NUMNODES && pm->page != p) | |
814 | pm++; | |
815 | ||
816 | if (pm->node == MAX_NUMNODES) | |
817 | return NULL; | |
818 | ||
819 | *result = &pm->status; | |
820 | ||
821 | return alloc_pages_exact_node(pm->node, | |
822 | GFP_HIGHUSER_MOVABLE | GFP_THISNODE, 0); | |
823 | } | |
824 | ||
825 | /* | |
826 | * Move a set of pages as indicated in the pm array. The addr | |
827 | * field must be set to the virtual address of the page to be moved | |
828 | * and the node number must contain a valid target node. | |
829 | * The pm array ends with node = MAX_NUMNODES. | |
830 | */ | |
831 | static int do_move_page_to_node_array(struct mm_struct *mm, | |
832 | struct page_to_node *pm, | |
833 | int migrate_all) | |
834 | { | |
835 | int err; | |
836 | struct page_to_node *pp; | |
837 | LIST_HEAD(pagelist); | |
838 | ||
839 | down_read(&mm->mmap_sem); | |
840 | ||
841 | /* | |
842 | * Build a list of pages to migrate | |
843 | */ | |
844 | for (pp = pm; pp->node != MAX_NUMNODES; pp++) { | |
845 | struct vm_area_struct *vma; | |
846 | struct page *page; | |
847 | ||
848 | err = -EFAULT; | |
849 | vma = find_vma(mm, pp->addr); | |
850 | if (!vma || !vma_migratable(vma)) | |
851 | goto set_status; | |
852 | ||
853 | page = follow_page(vma, pp->addr, FOLL_GET); | |
854 | ||
855 | err = PTR_ERR(page); | |
856 | if (IS_ERR(page)) | |
857 | goto set_status; | |
858 | ||
859 | err = -ENOENT; | |
860 | if (!page) | |
861 | goto set_status; | |
862 | ||
863 | if (PageReserved(page)) /* Check for zero page */ | |
864 | goto put_and_set; | |
865 | ||
866 | pp->page = page; | |
867 | err = page_to_nid(page); | |
868 | ||
869 | if (err == pp->node) | |
870 | /* | |
871 | * Node already in the right place | |
872 | */ | |
873 | goto put_and_set; | |
874 | ||
875 | err = -EACCES; | |
876 | if (page_mapcount(page) > 1 && | |
877 | !migrate_all) | |
878 | goto put_and_set; | |
879 | ||
880 | err = isolate_lru_page(page); | |
881 | if (!err) | |
882 | list_add_tail(&page->lru, &pagelist); | |
883 | put_and_set: | |
884 | /* | |
885 | * Either remove the duplicate refcount from | |
886 | * isolate_lru_page() or drop the page ref if it was | |
887 | * not isolated. | |
888 | */ | |
889 | put_page(page); | |
890 | set_status: | |
891 | pp->status = err; | |
892 | } | |
893 | ||
894 | err = 0; | |
895 | if (!list_empty(&pagelist)) | |
896 | err = migrate_pages(&pagelist, new_page_node, | |
897 | (unsigned long)pm); | |
898 | ||
899 | up_read(&mm->mmap_sem); | |
900 | return err; | |
901 | } | |
902 | ||
903 | /* | |
904 | * Migrate an array of page address onto an array of nodes and fill | |
905 | * the corresponding array of status. | |
906 | */ | |
907 | static int do_pages_move(struct mm_struct *mm, struct task_struct *task, | |
908 | unsigned long nr_pages, | |
909 | const void __user * __user *pages, | |
910 | const int __user *nodes, | |
911 | int __user *status, int flags) | |
912 | { | |
913 | struct page_to_node *pm; | |
914 | nodemask_t task_nodes; | |
915 | unsigned long chunk_nr_pages; | |
916 | unsigned long chunk_start; | |
917 | int err; | |
918 | ||
919 | task_nodes = cpuset_mems_allowed(task); | |
920 | ||
921 | err = -ENOMEM; | |
922 | pm = (struct page_to_node *)__get_free_page(GFP_KERNEL); | |
923 | if (!pm) | |
924 | goto out; | |
925 | ||
926 | migrate_prep(); | |
927 | ||
928 | /* | |
929 | * Store a chunk of page_to_node array in a page, | |
930 | * but keep the last one as a marker | |
931 | */ | |
932 | chunk_nr_pages = (PAGE_SIZE / sizeof(struct page_to_node)) - 1; | |
933 | ||
934 | for (chunk_start = 0; | |
935 | chunk_start < nr_pages; | |
936 | chunk_start += chunk_nr_pages) { | |
937 | int j; | |
938 | ||
939 | if (chunk_start + chunk_nr_pages > nr_pages) | |
940 | chunk_nr_pages = nr_pages - chunk_start; | |
941 | ||
942 | /* fill the chunk pm with addrs and nodes from user-space */ | |
943 | for (j = 0; j < chunk_nr_pages; j++) { | |
944 | const void __user *p; | |
945 | int node; | |
946 | ||
947 | err = -EFAULT; | |
948 | if (get_user(p, pages + j + chunk_start)) | |
949 | goto out_pm; | |
950 | pm[j].addr = (unsigned long) p; | |
951 | ||
952 | if (get_user(node, nodes + j + chunk_start)) | |
953 | goto out_pm; | |
954 | ||
955 | err = -ENODEV; | |
956 | if (!node_state(node, N_HIGH_MEMORY)) | |
957 | goto out_pm; | |
958 | ||
959 | err = -EACCES; | |
960 | if (!node_isset(node, task_nodes)) | |
961 | goto out_pm; | |
962 | ||
963 | pm[j].node = node; | |
964 | } | |
965 | ||
966 | /* End marker for this chunk */ | |
967 | pm[chunk_nr_pages].node = MAX_NUMNODES; | |
968 | ||
969 | /* Migrate this chunk */ | |
970 | err = do_move_page_to_node_array(mm, pm, | |
971 | flags & MPOL_MF_MOVE_ALL); | |
972 | if (err < 0) | |
973 | goto out_pm; | |
974 | ||
975 | /* Return status information */ | |
976 | for (j = 0; j < chunk_nr_pages; j++) | |
977 | if (put_user(pm[j].status, status + j + chunk_start)) { | |
978 | err = -EFAULT; | |
979 | goto out_pm; | |
980 | } | |
981 | } | |
982 | err = 0; | |
983 | ||
984 | out_pm: | |
985 | free_page((unsigned long)pm); | |
986 | out: | |
987 | return err; | |
988 | } | |
989 | ||
990 | /* | |
991 | * Determine the nodes of an array of pages and store it in an array of status. | |
992 | */ | |
993 | static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages, | |
994 | const void __user **pages, int *status) | |
995 | { | |
996 | unsigned long i; | |
997 | ||
998 | down_read(&mm->mmap_sem); | |
999 | ||
1000 | for (i = 0; i < nr_pages; i++) { | |
1001 | unsigned long addr = (unsigned long)(*pages); | |
1002 | struct vm_area_struct *vma; | |
1003 | struct page *page; | |
1004 | int err = -EFAULT; | |
1005 | ||
1006 | vma = find_vma(mm, addr); | |
1007 | if (!vma) | |
1008 | goto set_status; | |
1009 | ||
1010 | page = follow_page(vma, addr, 0); | |
1011 | ||
1012 | err = PTR_ERR(page); | |
1013 | if (IS_ERR(page)) | |
1014 | goto set_status; | |
1015 | ||
1016 | err = -ENOENT; | |
1017 | /* Use PageReserved to check for zero page */ | |
1018 | if (!page || PageReserved(page)) | |
1019 | goto set_status; | |
1020 | ||
1021 | err = page_to_nid(page); | |
1022 | set_status: | |
1023 | *status = err; | |
1024 | ||
1025 | pages++; | |
1026 | status++; | |
1027 | } | |
1028 | ||
1029 | up_read(&mm->mmap_sem); | |
1030 | } | |
1031 | ||
1032 | /* | |
1033 | * Determine the nodes of a user array of pages and store it in | |
1034 | * a user array of status. | |
1035 | */ | |
1036 | static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages, | |
1037 | const void __user * __user *pages, | |
1038 | int __user *status) | |
1039 | { | |
1040 | #define DO_PAGES_STAT_CHUNK_NR 16 | |
1041 | const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR]; | |
1042 | int chunk_status[DO_PAGES_STAT_CHUNK_NR]; | |
1043 | unsigned long i, chunk_nr = DO_PAGES_STAT_CHUNK_NR; | |
1044 | int err; | |
1045 | ||
1046 | for (i = 0; i < nr_pages; i += chunk_nr) { | |
1047 | if (chunk_nr + i > nr_pages) | |
1048 | chunk_nr = nr_pages - i; | |
1049 | ||
1050 | err = copy_from_user(chunk_pages, &pages[i], | |
1051 | chunk_nr * sizeof(*chunk_pages)); | |
1052 | if (err) { | |
1053 | err = -EFAULT; | |
1054 | goto out; | |
1055 | } | |
1056 | ||
1057 | do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status); | |
1058 | ||
1059 | err = copy_to_user(&status[i], chunk_status, | |
1060 | chunk_nr * sizeof(*chunk_status)); | |
1061 | if (err) { | |
1062 | err = -EFAULT; | |
1063 | goto out; | |
1064 | } | |
1065 | } | |
1066 | err = 0; | |
1067 | ||
1068 | out: | |
1069 | return err; | |
1070 | } | |
1071 | ||
1072 | /* | |
1073 | * Move a list of pages in the address space of the currently executing | |
1074 | * process. | |
1075 | */ | |
1076 | SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages, | |
1077 | const void __user * __user *, pages, | |
1078 | const int __user *, nodes, | |
1079 | int __user *, status, int, flags) | |
1080 | { | |
1081 | const struct cred *cred = current_cred(), *tcred; | |
1082 | struct task_struct *task; | |
1083 | struct mm_struct *mm; | |
1084 | int err; | |
1085 | ||
1086 | /* Check flags */ | |
1087 | if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL)) | |
1088 | return -EINVAL; | |
1089 | ||
1090 | if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE)) | |
1091 | return -EPERM; | |
1092 | ||
1093 | /* Find the mm_struct */ | |
1094 | read_lock(&tasklist_lock); | |
1095 | task = pid ? find_task_by_vpid(pid) : current; | |
1096 | if (!task) { | |
1097 | read_unlock(&tasklist_lock); | |
1098 | return -ESRCH; | |
1099 | } | |
1100 | mm = get_task_mm(task); | |
1101 | read_unlock(&tasklist_lock); | |
1102 | ||
1103 | if (!mm) | |
1104 | return -EINVAL; | |
1105 | ||
1106 | /* | |
1107 | * Check if this process has the right to modify the specified | |
1108 | * process. The right exists if the process has administrative | |
1109 | * capabilities, superuser privileges or the same | |
1110 | * userid as the target process. | |
1111 | */ | |
1112 | rcu_read_lock(); | |
1113 | tcred = __task_cred(task); | |
1114 | if (cred->euid != tcred->suid && cred->euid != tcred->uid && | |
1115 | cred->uid != tcred->suid && cred->uid != tcred->uid && | |
1116 | !capable(CAP_SYS_NICE)) { | |
1117 | rcu_read_unlock(); | |
1118 | err = -EPERM; | |
1119 | goto out; | |
1120 | } | |
1121 | rcu_read_unlock(); | |
1122 | ||
1123 | err = security_task_movememory(task); | |
1124 | if (err) | |
1125 | goto out; | |
1126 | ||
1127 | if (nodes) { | |
1128 | err = do_pages_move(mm, task, nr_pages, pages, nodes, status, | |
1129 | flags); | |
1130 | } else { | |
1131 | err = do_pages_stat(mm, nr_pages, pages, status); | |
1132 | } | |
1133 | ||
1134 | out: | |
1135 | mmput(mm); | |
1136 | return err; | |
1137 | } | |
1138 | ||
1139 | /* | |
1140 | * Call migration functions in the vma_ops that may prepare | |
1141 | * memory in a vm for migration. migration functions may perform | |
1142 | * the migration for vmas that do not have an underlying page struct. | |
1143 | */ | |
1144 | int migrate_vmas(struct mm_struct *mm, const nodemask_t *to, | |
1145 | const nodemask_t *from, unsigned long flags) | |
1146 | { | |
1147 | struct vm_area_struct *vma; | |
1148 | int err = 0; | |
1149 | ||
1150 | for (vma = mm->mmap; vma && !err; vma = vma->vm_next) { | |
1151 | if (vma->vm_ops && vma->vm_ops->migrate) { | |
1152 | err = vma->vm_ops->migrate(vma, to, from, flags); | |
1153 | if (err) | |
1154 | break; | |
1155 | } | |
1156 | } | |
1157 | return err; | |
1158 | } | |
1159 | #endif |