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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 <clameter@sgi.com> | |
13 | */ | |
14 | ||
15 | #include <linux/migrate.h> | |
16 | #include <linux/module.h> | |
17 | #include <linux/swap.h> | |
18 | #include <linux/pagemap.h> | |
19 | #include <linux/buffer_head.h> /* for try_to_release_page(), | |
20 | buffer_heads_over_limit */ | |
21 | #include <linux/mm_inline.h> | |
22 | #include <linux/pagevec.h> | |
23 | #include <linux/rmap.h> | |
24 | #include <linux/topology.h> | |
25 | #include <linux/cpu.h> | |
26 | #include <linux/cpuset.h> | |
27 | #include <linux/swapops.h> | |
28 | ||
29 | #include "internal.h" | |
30 | ||
31 | #include "internal.h" | |
32 | ||
33 | /* The maximum number of pages to take off the LRU for migration */ | |
34 | #define MIGRATE_CHUNK_SIZE 256 | |
35 | ||
36 | #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) | |
37 | ||
38 | /* | |
39 | * Isolate one page from the LRU lists. If successful put it onto | |
40 | * the indicated list with elevated page count. | |
41 | * | |
42 | * Result: | |
43 | * -EBUSY: page not on LRU list | |
44 | * 0: page removed from LRU list and added to the specified list. | |
45 | */ | |
46 | int isolate_lru_page(struct page *page, struct list_head *pagelist) | |
47 | { | |
48 | int ret = -EBUSY; | |
49 | ||
50 | if (PageLRU(page)) { | |
51 | struct zone *zone = page_zone(page); | |
52 | ||
53 | spin_lock_irq(&zone->lru_lock); | |
54 | if (PageLRU(page)) { | |
55 | ret = 0; | |
56 | get_page(page); | |
57 | ClearPageLRU(page); | |
58 | if (PageActive(page)) | |
59 | del_page_from_active_list(zone, page); | |
60 | else | |
61 | del_page_from_inactive_list(zone, page); | |
62 | list_add_tail(&page->lru, pagelist); | |
63 | } | |
64 | spin_unlock_irq(&zone->lru_lock); | |
65 | } | |
66 | return ret; | |
67 | } | |
68 | ||
69 | /* | |
70 | * migrate_prep() needs to be called after we have compiled the list of pages | |
71 | * to be migrated using isolate_lru_page() but before we begin a series of calls | |
72 | * to migrate_pages(). | |
73 | */ | |
74 | int migrate_prep(void) | |
75 | { | |
76 | /* Must have swap device for migration */ | |
77 | if (nr_swap_pages <= 0) | |
78 | return -ENODEV; | |
79 | ||
80 | /* | |
81 | * Clear the LRU lists so pages can be isolated. | |
82 | * Note that pages may be moved off the LRU after we have | |
83 | * drained them. Those pages will fail to migrate like other | |
84 | * pages that may be busy. | |
85 | */ | |
86 | lru_add_drain_all(); | |
87 | ||
88 | return 0; | |
89 | } | |
90 | ||
91 | static inline void move_to_lru(struct page *page) | |
92 | { | |
93 | list_del(&page->lru); | |
94 | if (PageActive(page)) { | |
95 | /* | |
96 | * lru_cache_add_active checks that | |
97 | * the PG_active bit is off. | |
98 | */ | |
99 | ClearPageActive(page); | |
100 | lru_cache_add_active(page); | |
101 | } else { | |
102 | lru_cache_add(page); | |
103 | } | |
104 | put_page(page); | |
105 | } | |
106 | ||
107 | /* | |
108 | * Add isolated pages on the list back to the LRU. | |
109 | * | |
110 | * returns the number of pages put back. | |
111 | */ | |
112 | int putback_lru_pages(struct list_head *l) | |
113 | { | |
114 | struct page *page; | |
115 | struct page *page2; | |
116 | int count = 0; | |
117 | ||
118 | list_for_each_entry_safe(page, page2, l, lru) { | |
119 | move_to_lru(page); | |
120 | count++; | |
121 | } | |
122 | return count; | |
123 | } | |
124 | ||
125 | /* | |
126 | * Non migratable page | |
127 | */ | |
128 | int fail_migrate_page(struct page *newpage, struct page *page) | |
129 | { | |
130 | return -EIO; | |
131 | } | |
132 | EXPORT_SYMBOL(fail_migrate_page); | |
133 | ||
134 | /* | |
135 | * swapout a single page | |
136 | * page is locked upon entry, unlocked on exit | |
137 | */ | |
138 | static int swap_page(struct page *page) | |
139 | { | |
140 | struct address_space *mapping = page_mapping(page); | |
141 | ||
142 | if (page_mapped(page) && mapping) | |
143 | if (try_to_unmap(page, 1) != SWAP_SUCCESS) | |
144 | goto unlock_retry; | |
145 | ||
146 | if (PageDirty(page)) { | |
147 | /* Page is dirty, try to write it out here */ | |
148 | switch(pageout(page, mapping)) { | |
149 | case PAGE_KEEP: | |
150 | case PAGE_ACTIVATE: | |
151 | goto unlock_retry; | |
152 | ||
153 | case PAGE_SUCCESS: | |
154 | goto retry; | |
155 | ||
156 | case PAGE_CLEAN: | |
157 | ; /* try to free the page below */ | |
158 | } | |
159 | } | |
160 | ||
161 | if (PagePrivate(page)) { | |
162 | if (!try_to_release_page(page, GFP_KERNEL) || | |
163 | (!mapping && page_count(page) == 1)) | |
164 | goto unlock_retry; | |
165 | } | |
166 | ||
167 | if (remove_mapping(mapping, page)) { | |
168 | /* Success */ | |
169 | unlock_page(page); | |
170 | return 0; | |
171 | } | |
172 | ||
173 | unlock_retry: | |
174 | unlock_page(page); | |
175 | ||
176 | retry: | |
177 | return -EAGAIN; | |
178 | } | |
179 | EXPORT_SYMBOL(swap_page); | |
180 | ||
181 | /* | |
182 | * Remove references for a page and establish the new page with the correct | |
183 | * basic settings to be able to stop accesses to the page. | |
184 | */ | |
185 | int migrate_page_remove_references(struct page *newpage, | |
186 | struct page *page, int nr_refs) | |
187 | { | |
188 | struct address_space *mapping = page_mapping(page); | |
189 | struct page **radix_pointer; | |
190 | ||
191 | /* | |
192 | * Avoid doing any of the following work if the page count | |
193 | * indicates that the page is in use or truncate has removed | |
194 | * the page. | |
195 | */ | |
196 | if (!mapping || page_mapcount(page) + nr_refs != page_count(page)) | |
197 | return -EAGAIN; | |
198 | ||
199 | /* | |
200 | * Establish swap ptes for anonymous pages or destroy pte | |
201 | * maps for files. | |
202 | * | |
203 | * In order to reestablish file backed mappings the fault handlers | |
204 | * will take the radix tree_lock which may then be used to stop | |
205 | * processses from accessing this page until the new page is ready. | |
206 | * | |
207 | * A process accessing via a swap pte (an anonymous page) will take a | |
208 | * page_lock on the old page which will block the process until the | |
209 | * migration attempt is complete. At that time the PageSwapCache bit | |
210 | * will be examined. If the page was migrated then the PageSwapCache | |
211 | * bit will be clear and the operation to retrieve the page will be | |
212 | * retried which will find the new page in the radix tree. Then a new | |
213 | * direct mapping may be generated based on the radix tree contents. | |
214 | * | |
215 | * If the page was not migrated then the PageSwapCache bit | |
216 | * is still set and the operation may continue. | |
217 | */ | |
218 | if (try_to_unmap(page, 1) == SWAP_FAIL) | |
219 | /* A vma has VM_LOCKED set -> permanent failure */ | |
220 | return -EPERM; | |
221 | ||
222 | /* | |
223 | * Give up if we were unable to remove all mappings. | |
224 | */ | |
225 | if (page_mapcount(page)) | |
226 | return -EAGAIN; | |
227 | ||
228 | write_lock_irq(&mapping->tree_lock); | |
229 | ||
230 | radix_pointer = (struct page **)radix_tree_lookup_slot( | |
231 | &mapping->page_tree, | |
232 | page_index(page)); | |
233 | ||
234 | if (!page_mapping(page) || page_count(page) != nr_refs || | |
235 | *radix_pointer != page) { | |
236 | write_unlock_irq(&mapping->tree_lock); | |
237 | return 1; | |
238 | } | |
239 | ||
240 | /* | |
241 | * Now we know that no one else is looking at the page. | |
242 | * | |
243 | * Certain minimal information about a page must be available | |
244 | * in order for other subsystems to properly handle the page if they | |
245 | * find it through the radix tree update before we are finished | |
246 | * copying the page. | |
247 | */ | |
248 | get_page(newpage); | |
249 | newpage->index = page->index; | |
250 | newpage->mapping = page->mapping; | |
251 | if (PageSwapCache(page)) { | |
252 | SetPageSwapCache(newpage); | |
253 | set_page_private(newpage, page_private(page)); | |
254 | } | |
255 | ||
256 | *radix_pointer = newpage; | |
257 | __put_page(page); | |
258 | write_unlock_irq(&mapping->tree_lock); | |
259 | ||
260 | return 0; | |
261 | } | |
262 | EXPORT_SYMBOL(migrate_page_remove_references); | |
263 | ||
264 | /* | |
265 | * Copy the page to its new location | |
266 | */ | |
267 | void migrate_page_copy(struct page *newpage, struct page *page) | |
268 | { | |
269 | copy_highpage(newpage, page); | |
270 | ||
271 | if (PageError(page)) | |
272 | SetPageError(newpage); | |
273 | if (PageReferenced(page)) | |
274 | SetPageReferenced(newpage); | |
275 | if (PageUptodate(page)) | |
276 | SetPageUptodate(newpage); | |
277 | if (PageActive(page)) | |
278 | SetPageActive(newpage); | |
279 | if (PageChecked(page)) | |
280 | SetPageChecked(newpage); | |
281 | if (PageMappedToDisk(page)) | |
282 | SetPageMappedToDisk(newpage); | |
283 | ||
284 | if (PageDirty(page)) { | |
285 | clear_page_dirty_for_io(page); | |
286 | set_page_dirty(newpage); | |
287 | } | |
288 | ||
289 | ClearPageSwapCache(page); | |
290 | ClearPageActive(page); | |
291 | ClearPagePrivate(page); | |
292 | set_page_private(page, 0); | |
293 | page->mapping = NULL; | |
294 | ||
295 | /* | |
296 | * If any waiters have accumulated on the new page then | |
297 | * wake them up. | |
298 | */ | |
299 | if (PageWriteback(newpage)) | |
300 | end_page_writeback(newpage); | |
301 | } | |
302 | EXPORT_SYMBOL(migrate_page_copy); | |
303 | ||
304 | /* | |
305 | * Common logic to directly migrate a single page suitable for | |
306 | * pages that do not use PagePrivate. | |
307 | * | |
308 | * Pages are locked upon entry and exit. | |
309 | */ | |
310 | int migrate_page(struct page *newpage, struct page *page) | |
311 | { | |
312 | int rc; | |
313 | ||
314 | BUG_ON(PageWriteback(page)); /* Writeback must be complete */ | |
315 | ||
316 | rc = migrate_page_remove_references(newpage, page, 2); | |
317 | ||
318 | if (rc) | |
319 | return rc; | |
320 | ||
321 | migrate_page_copy(newpage, page); | |
322 | ||
323 | /* | |
324 | * Remove auxiliary swap entries and replace | |
325 | * them with real ptes. | |
326 | * | |
327 | * Note that a real pte entry will allow processes that are not | |
328 | * waiting on the page lock to use the new page via the page tables | |
329 | * before the new page is unlocked. | |
330 | */ | |
331 | remove_from_swap(newpage); | |
332 | return 0; | |
333 | } | |
334 | EXPORT_SYMBOL(migrate_page); | |
335 | ||
336 | /* | |
337 | * migrate_pages | |
338 | * | |
339 | * Two lists are passed to this function. The first list | |
340 | * contains the pages isolated from the LRU to be migrated. | |
341 | * The second list contains new pages that the pages isolated | |
342 | * can be moved to. If the second list is NULL then all | |
343 | * pages are swapped out. | |
344 | * | |
345 | * The function returns after 10 attempts or if no pages | |
346 | * are movable anymore because to has become empty | |
347 | * or no retryable pages exist anymore. | |
348 | * | |
349 | * Return: Number of pages not migrated when "to" ran empty. | |
350 | */ | |
351 | int migrate_pages(struct list_head *from, struct list_head *to, | |
352 | struct list_head *moved, struct list_head *failed) | |
353 | { | |
354 | int retry; | |
355 | int nr_failed = 0; | |
356 | int pass = 0; | |
357 | struct page *page; | |
358 | struct page *page2; | |
359 | int swapwrite = current->flags & PF_SWAPWRITE; | |
360 | int rc; | |
361 | ||
362 | if (!swapwrite) | |
363 | current->flags |= PF_SWAPWRITE; | |
364 | ||
365 | redo: | |
366 | retry = 0; | |
367 | ||
368 | list_for_each_entry_safe(page, page2, from, lru) { | |
369 | struct page *newpage = NULL; | |
370 | struct address_space *mapping; | |
371 | ||
372 | cond_resched(); | |
373 | ||
374 | rc = 0; | |
375 | if (page_count(page) == 1) | |
376 | /* page was freed from under us. So we are done. */ | |
377 | goto next; | |
378 | ||
379 | if (to && list_empty(to)) | |
380 | break; | |
381 | ||
382 | /* | |
383 | * Skip locked pages during the first two passes to give the | |
384 | * functions holding the lock time to release the page. Later we | |
385 | * use lock_page() to have a higher chance of acquiring the | |
386 | * lock. | |
387 | */ | |
388 | rc = -EAGAIN; | |
389 | if (pass > 2) | |
390 | lock_page(page); | |
391 | else | |
392 | if (TestSetPageLocked(page)) | |
393 | goto next; | |
394 | ||
395 | /* | |
396 | * Only wait on writeback if we have already done a pass where | |
397 | * we we may have triggered writeouts for lots of pages. | |
398 | */ | |
399 | if (pass > 0) { | |
400 | wait_on_page_writeback(page); | |
401 | } else { | |
402 | if (PageWriteback(page)) | |
403 | goto unlock_page; | |
404 | } | |
405 | ||
406 | /* | |
407 | * Anonymous pages must have swap cache references otherwise | |
408 | * the information contained in the page maps cannot be | |
409 | * preserved. | |
410 | */ | |
411 | if (PageAnon(page) && !PageSwapCache(page)) { | |
412 | if (!add_to_swap(page, GFP_KERNEL)) { | |
413 | rc = -ENOMEM; | |
414 | goto unlock_page; | |
415 | } | |
416 | } | |
417 | ||
418 | if (!to) { | |
419 | rc = swap_page(page); | |
420 | goto next; | |
421 | } | |
422 | ||
423 | newpage = lru_to_page(to); | |
424 | lock_page(newpage); | |
425 | ||
426 | /* | |
427 | * Pages are properly locked and writeback is complete. | |
428 | * Try to migrate the page. | |
429 | */ | |
430 | mapping = page_mapping(page); | |
431 | if (!mapping) | |
432 | goto unlock_both; | |
433 | ||
434 | if (mapping->a_ops->migratepage) { | |
435 | /* | |
436 | * Most pages have a mapping and most filesystems | |
437 | * should provide a migration function. Anonymous | |
438 | * pages are part of swap space which also has its | |
439 | * own migration function. This is the most common | |
440 | * path for page migration. | |
441 | */ | |
442 | rc = mapping->a_ops->migratepage(newpage, page); | |
443 | goto unlock_both; | |
444 | } | |
445 | ||
446 | /* | |
447 | * Default handling if a filesystem does not provide | |
448 | * a migration function. We can only migrate clean | |
449 | * pages so try to write out any dirty pages first. | |
450 | */ | |
451 | if (PageDirty(page)) { | |
452 | switch (pageout(page, mapping)) { | |
453 | case PAGE_KEEP: | |
454 | case PAGE_ACTIVATE: | |
455 | goto unlock_both; | |
456 | ||
457 | case PAGE_SUCCESS: | |
458 | unlock_page(newpage); | |
459 | goto next; | |
460 | ||
461 | case PAGE_CLEAN: | |
462 | ; /* try to migrate the page below */ | |
463 | } | |
464 | } | |
465 | ||
466 | /* | |
467 | * Buffers are managed in a filesystem specific way. | |
468 | * We must have no buffers or drop them. | |
469 | */ | |
470 | if (!page_has_buffers(page) || | |
471 | try_to_release_page(page, GFP_KERNEL)) { | |
472 | rc = migrate_page(newpage, page); | |
473 | goto unlock_both; | |
474 | } | |
475 | ||
476 | /* | |
477 | * On early passes with mapped pages simply | |
478 | * retry. There may be a lock held for some | |
479 | * buffers that may go away. Later | |
480 | * swap them out. | |
481 | */ | |
482 | if (pass > 4) { | |
483 | /* | |
484 | * Persistently unable to drop buffers..... As a | |
485 | * measure of last resort we fall back to | |
486 | * swap_page(). | |
487 | */ | |
488 | unlock_page(newpage); | |
489 | newpage = NULL; | |
490 | rc = swap_page(page); | |
491 | goto next; | |
492 | } | |
493 | ||
494 | unlock_both: | |
495 | unlock_page(newpage); | |
496 | ||
497 | unlock_page: | |
498 | unlock_page(page); | |
499 | ||
500 | next: | |
501 | if (rc == -EAGAIN) { | |
502 | retry++; | |
503 | } else if (rc) { | |
504 | /* Permanent failure */ | |
505 | list_move(&page->lru, failed); | |
506 | nr_failed++; | |
507 | } else { | |
508 | if (newpage) { | |
509 | /* Successful migration. Return page to LRU */ | |
510 | move_to_lru(newpage); | |
511 | } | |
512 | list_move(&page->lru, moved); | |
513 | } | |
514 | } | |
515 | if (retry && pass++ < 10) | |
516 | goto redo; | |
517 | ||
518 | if (!swapwrite) | |
519 | current->flags &= ~PF_SWAPWRITE; | |
520 | ||
521 | return nr_failed + retry; | |
522 | } | |
523 | ||
524 | /* | |
525 | * Migration function for pages with buffers. This function can only be used | |
526 | * if the underlying filesystem guarantees that no other references to "page" | |
527 | * exist. | |
528 | */ | |
529 | int buffer_migrate_page(struct page *newpage, struct page *page) | |
530 | { | |
531 | struct address_space *mapping = page->mapping; | |
532 | struct buffer_head *bh, *head; | |
533 | int rc; | |
534 | ||
535 | if (!mapping) | |
536 | return -EAGAIN; | |
537 | ||
538 | if (!page_has_buffers(page)) | |
539 | return migrate_page(newpage, page); | |
540 | ||
541 | head = page_buffers(page); | |
542 | ||
543 | rc = migrate_page_remove_references(newpage, page, 3); | |
544 | ||
545 | if (rc) | |
546 | return rc; | |
547 | ||
548 | bh = head; | |
549 | do { | |
550 | get_bh(bh); | |
551 | lock_buffer(bh); | |
552 | bh = bh->b_this_page; | |
553 | ||
554 | } while (bh != head); | |
555 | ||
556 | ClearPagePrivate(page); | |
557 | set_page_private(newpage, page_private(page)); | |
558 | set_page_private(page, 0); | |
559 | put_page(page); | |
560 | get_page(newpage); | |
561 | ||
562 | bh = head; | |
563 | do { | |
564 | set_bh_page(bh, newpage, bh_offset(bh)); | |
565 | bh = bh->b_this_page; | |
566 | ||
567 | } while (bh != head); | |
568 | ||
569 | SetPagePrivate(newpage); | |
570 | ||
571 | migrate_page_copy(newpage, page); | |
572 | ||
573 | bh = head; | |
574 | do { | |
575 | unlock_buffer(bh); | |
576 | put_bh(bh); | |
577 | bh = bh->b_this_page; | |
578 | ||
579 | } while (bh != head); | |
580 | ||
581 | return 0; | |
582 | } | |
583 | EXPORT_SYMBOL(buffer_migrate_page); | |
584 | ||
585 | /* | |
586 | * Migrate the list 'pagelist' of pages to a certain destination. | |
587 | * | |
588 | * Specify destination with either non-NULL vma or dest_node >= 0 | |
589 | * Return the number of pages not migrated or error code | |
590 | */ | |
591 | int migrate_pages_to(struct list_head *pagelist, | |
592 | struct vm_area_struct *vma, int dest) | |
593 | { | |
594 | LIST_HEAD(newlist); | |
595 | LIST_HEAD(moved); | |
596 | LIST_HEAD(failed); | |
597 | int err = 0; | |
598 | unsigned long offset = 0; | |
599 | int nr_pages; | |
600 | struct page *page; | |
601 | struct list_head *p; | |
602 | ||
603 | redo: | |
604 | nr_pages = 0; | |
605 | list_for_each(p, pagelist) { | |
606 | if (vma) { | |
607 | /* | |
608 | * The address passed to alloc_page_vma is used to | |
609 | * generate the proper interleave behavior. We fake | |
610 | * the address here by an increasing offset in order | |
611 | * to get the proper distribution of pages. | |
612 | * | |
613 | * No decision has been made as to which page | |
614 | * a certain old page is moved to so we cannot | |
615 | * specify the correct address. | |
616 | */ | |
617 | page = alloc_page_vma(GFP_HIGHUSER, vma, | |
618 | offset + vma->vm_start); | |
619 | offset += PAGE_SIZE; | |
620 | } | |
621 | else | |
622 | page = alloc_pages_node(dest, GFP_HIGHUSER, 0); | |
623 | ||
624 | if (!page) { | |
625 | err = -ENOMEM; | |
626 | goto out; | |
627 | } | |
628 | list_add_tail(&page->lru, &newlist); | |
629 | nr_pages++; | |
630 | if (nr_pages > MIGRATE_CHUNK_SIZE) | |
631 | break; | |
632 | } | |
633 | err = migrate_pages(pagelist, &newlist, &moved, &failed); | |
634 | ||
635 | putback_lru_pages(&moved); /* Call release pages instead ?? */ | |
636 | ||
637 | if (err >= 0 && list_empty(&newlist) && !list_empty(pagelist)) | |
638 | goto redo; | |
639 | out: | |
640 | /* Return leftover allocated pages */ | |
641 | while (!list_empty(&newlist)) { | |
642 | page = list_entry(newlist.next, struct page, lru); | |
643 | list_del(&page->lru); | |
644 | __free_page(page); | |
645 | } | |
646 | list_splice(&failed, pagelist); | |
647 | if (err < 0) | |
648 | return err; | |
649 | ||
650 | /* Calculate number of leftover pages */ | |
651 | nr_pages = 0; | |
652 | list_for_each(p, pagelist) | |
653 | nr_pages++; | |
654 | return nr_pages; | |
655 | } |