]>
Commit | Line | Data |
---|---|---|
b20a3503 CL |
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> | |
e23ca00b | 19 | #include <linux/buffer_head.h> |
b20a3503 CL |
20 | #include <linux/mm_inline.h> |
21 | #include <linux/pagevec.h> | |
22 | #include <linux/rmap.h> | |
23 | #include <linux/topology.h> | |
24 | #include <linux/cpu.h> | |
25 | #include <linux/cpuset.h> | |
26 | #include <linux/swapops.h> | |
27 | ||
28 | #include "internal.h" | |
29 | ||
b20a3503 CL |
30 | /* The maximum number of pages to take off the LRU for migration */ |
31 | #define MIGRATE_CHUNK_SIZE 256 | |
32 | ||
33 | #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) | |
34 | ||
35 | /* | |
36 | * Isolate one page from the LRU lists. If successful put it onto | |
37 | * the indicated list with elevated page count. | |
38 | * | |
39 | * Result: | |
40 | * -EBUSY: page not on LRU list | |
41 | * 0: page removed from LRU list and added to the specified list. | |
42 | */ | |
43 | int isolate_lru_page(struct page *page, struct list_head *pagelist) | |
44 | { | |
45 | int ret = -EBUSY; | |
46 | ||
47 | if (PageLRU(page)) { | |
48 | struct zone *zone = page_zone(page); | |
49 | ||
50 | spin_lock_irq(&zone->lru_lock); | |
51 | if (PageLRU(page)) { | |
52 | ret = 0; | |
53 | get_page(page); | |
54 | ClearPageLRU(page); | |
55 | if (PageActive(page)) | |
56 | del_page_from_active_list(zone, page); | |
57 | else | |
58 | del_page_from_inactive_list(zone, page); | |
59 | list_add_tail(&page->lru, pagelist); | |
60 | } | |
61 | spin_unlock_irq(&zone->lru_lock); | |
62 | } | |
63 | return ret; | |
64 | } | |
65 | ||
66 | /* | |
67 | * migrate_prep() needs to be called after we have compiled the list of pages | |
68 | * to be migrated using isolate_lru_page() but before we begin a series of calls | |
69 | * to migrate_pages(). | |
70 | */ | |
71 | int migrate_prep(void) | |
72 | { | |
73 | /* Must have swap device for migration */ | |
74 | if (nr_swap_pages <= 0) | |
75 | return -ENODEV; | |
76 | ||
77 | /* | |
78 | * Clear the LRU lists so pages can be isolated. | |
79 | * Note that pages may be moved off the LRU after we have | |
80 | * drained them. Those pages will fail to migrate like other | |
81 | * pages that may be busy. | |
82 | */ | |
83 | lru_add_drain_all(); | |
84 | ||
85 | return 0; | |
86 | } | |
87 | ||
88 | static inline void move_to_lru(struct page *page) | |
89 | { | |
90 | list_del(&page->lru); | |
91 | if (PageActive(page)) { | |
92 | /* | |
93 | * lru_cache_add_active checks that | |
94 | * the PG_active bit is off. | |
95 | */ | |
96 | ClearPageActive(page); | |
97 | lru_cache_add_active(page); | |
98 | } else { | |
99 | lru_cache_add(page); | |
100 | } | |
101 | put_page(page); | |
102 | } | |
103 | ||
104 | /* | |
105 | * Add isolated pages on the list back to the LRU. | |
106 | * | |
107 | * returns the number of pages put back. | |
108 | */ | |
109 | int putback_lru_pages(struct list_head *l) | |
110 | { | |
111 | struct page *page; | |
112 | struct page *page2; | |
113 | int count = 0; | |
114 | ||
115 | list_for_each_entry_safe(page, page2, l, lru) { | |
116 | move_to_lru(page); | |
117 | count++; | |
118 | } | |
119 | return count; | |
120 | } | |
121 | ||
122 | /* | |
123 | * Non migratable page | |
124 | */ | |
125 | int fail_migrate_page(struct page *newpage, struct page *page) | |
126 | { | |
127 | return -EIO; | |
128 | } | |
129 | EXPORT_SYMBOL(fail_migrate_page); | |
130 | ||
131 | /* | |
132 | * swapout a single page | |
133 | * page is locked upon entry, unlocked on exit | |
134 | */ | |
135 | static int swap_page(struct page *page) | |
136 | { | |
137 | struct address_space *mapping = page_mapping(page); | |
138 | ||
139 | if (page_mapped(page) && mapping) | |
140 | if (try_to_unmap(page, 1) != SWAP_SUCCESS) | |
141 | goto unlock_retry; | |
142 | ||
143 | if (PageDirty(page)) { | |
144 | /* Page is dirty, try to write it out here */ | |
145 | switch(pageout(page, mapping)) { | |
146 | case PAGE_KEEP: | |
147 | case PAGE_ACTIVATE: | |
148 | goto unlock_retry; | |
149 | ||
150 | case PAGE_SUCCESS: | |
151 | goto retry; | |
152 | ||
153 | case PAGE_CLEAN: | |
154 | ; /* try to free the page below */ | |
155 | } | |
156 | } | |
157 | ||
158 | if (PagePrivate(page)) { | |
159 | if (!try_to_release_page(page, GFP_KERNEL) || | |
160 | (!mapping && page_count(page) == 1)) | |
161 | goto unlock_retry; | |
162 | } | |
163 | ||
164 | if (remove_mapping(mapping, page)) { | |
165 | /* Success */ | |
166 | unlock_page(page); | |
167 | return 0; | |
168 | } | |
169 | ||
170 | unlock_retry: | |
171 | unlock_page(page); | |
172 | ||
173 | retry: | |
174 | return -EAGAIN; | |
175 | } | |
b20a3503 CL |
176 | |
177 | /* | |
178 | * Remove references for a page and establish the new page with the correct | |
179 | * basic settings to be able to stop accesses to the page. | |
180 | */ | |
181 | int migrate_page_remove_references(struct page *newpage, | |
182 | struct page *page, int nr_refs) | |
183 | { | |
184 | struct address_space *mapping = page_mapping(page); | |
185 | struct page **radix_pointer; | |
186 | ||
187 | /* | |
188 | * Avoid doing any of the following work if the page count | |
189 | * indicates that the page is in use or truncate has removed | |
190 | * the page. | |
191 | */ | |
192 | if (!mapping || page_mapcount(page) + nr_refs != page_count(page)) | |
193 | return -EAGAIN; | |
194 | ||
195 | /* | |
196 | * Establish swap ptes for anonymous pages or destroy pte | |
197 | * maps for files. | |
198 | * | |
199 | * In order to reestablish file backed mappings the fault handlers | |
200 | * will take the radix tree_lock which may then be used to stop | |
201 | * processses from accessing this page until the new page is ready. | |
202 | * | |
203 | * A process accessing via a swap pte (an anonymous page) will take a | |
204 | * page_lock on the old page which will block the process until the | |
205 | * migration attempt is complete. At that time the PageSwapCache bit | |
206 | * will be examined. If the page was migrated then the PageSwapCache | |
207 | * bit will be clear and the operation to retrieve the page will be | |
208 | * retried which will find the new page in the radix tree. Then a new | |
209 | * direct mapping may be generated based on the radix tree contents. | |
210 | * | |
211 | * If the page was not migrated then the PageSwapCache bit | |
212 | * is still set and the operation may continue. | |
213 | */ | |
214 | if (try_to_unmap(page, 1) == SWAP_FAIL) | |
215 | /* A vma has VM_LOCKED set -> permanent failure */ | |
216 | return -EPERM; | |
217 | ||
218 | /* | |
219 | * Give up if we were unable to remove all mappings. | |
220 | */ | |
221 | if (page_mapcount(page)) | |
222 | return -EAGAIN; | |
223 | ||
224 | write_lock_irq(&mapping->tree_lock); | |
225 | ||
226 | radix_pointer = (struct page **)radix_tree_lookup_slot( | |
227 | &mapping->page_tree, | |
228 | page_index(page)); | |
229 | ||
230 | if (!page_mapping(page) || page_count(page) != nr_refs || | |
231 | *radix_pointer != page) { | |
232 | write_unlock_irq(&mapping->tree_lock); | |
e23ca00b | 233 | return -EAGAIN; |
b20a3503 CL |
234 | } |
235 | ||
236 | /* | |
237 | * Now we know that no one else is looking at the page. | |
238 | * | |
239 | * Certain minimal information about a page must be available | |
240 | * in order for other subsystems to properly handle the page if they | |
241 | * find it through the radix tree update before we are finished | |
242 | * copying the page. | |
243 | */ | |
244 | get_page(newpage); | |
245 | newpage->index = page->index; | |
246 | newpage->mapping = page->mapping; | |
247 | if (PageSwapCache(page)) { | |
248 | SetPageSwapCache(newpage); | |
249 | set_page_private(newpage, page_private(page)); | |
250 | } | |
251 | ||
252 | *radix_pointer = newpage; | |
253 | __put_page(page); | |
254 | write_unlock_irq(&mapping->tree_lock); | |
255 | ||
256 | return 0; | |
257 | } | |
258 | EXPORT_SYMBOL(migrate_page_remove_references); | |
259 | ||
260 | /* | |
261 | * Copy the page to its new location | |
262 | */ | |
263 | void migrate_page_copy(struct page *newpage, struct page *page) | |
264 | { | |
265 | copy_highpage(newpage, page); | |
266 | ||
267 | if (PageError(page)) | |
268 | SetPageError(newpage); | |
269 | if (PageReferenced(page)) | |
270 | SetPageReferenced(newpage); | |
271 | if (PageUptodate(page)) | |
272 | SetPageUptodate(newpage); | |
273 | if (PageActive(page)) | |
274 | SetPageActive(newpage); | |
275 | if (PageChecked(page)) | |
276 | SetPageChecked(newpage); | |
277 | if (PageMappedToDisk(page)) | |
278 | SetPageMappedToDisk(newpage); | |
279 | ||
280 | if (PageDirty(page)) { | |
281 | clear_page_dirty_for_io(page); | |
282 | set_page_dirty(newpage); | |
283 | } | |
284 | ||
285 | ClearPageSwapCache(page); | |
286 | ClearPageActive(page); | |
287 | ClearPagePrivate(page); | |
288 | set_page_private(page, 0); | |
289 | page->mapping = NULL; | |
290 | ||
291 | /* | |
292 | * If any waiters have accumulated on the new page then | |
293 | * wake them up. | |
294 | */ | |
295 | if (PageWriteback(newpage)) | |
296 | end_page_writeback(newpage); | |
297 | } | |
298 | EXPORT_SYMBOL(migrate_page_copy); | |
299 | ||
300 | /* | |
301 | * Common logic to directly migrate a single page suitable for | |
302 | * pages that do not use PagePrivate. | |
303 | * | |
304 | * Pages are locked upon entry and exit. | |
305 | */ | |
306 | int migrate_page(struct page *newpage, struct page *page) | |
307 | { | |
308 | int rc; | |
309 | ||
310 | BUG_ON(PageWriteback(page)); /* Writeback must be complete */ | |
311 | ||
312 | rc = migrate_page_remove_references(newpage, page, 2); | |
313 | ||
314 | if (rc) | |
315 | return rc; | |
316 | ||
317 | migrate_page_copy(newpage, page); | |
318 | ||
319 | /* | |
320 | * Remove auxiliary swap entries and replace | |
321 | * them with real ptes. | |
322 | * | |
323 | * Note that a real pte entry will allow processes that are not | |
324 | * waiting on the page lock to use the new page via the page tables | |
325 | * before the new page is unlocked. | |
326 | */ | |
327 | remove_from_swap(newpage); | |
328 | return 0; | |
329 | } | |
330 | EXPORT_SYMBOL(migrate_page); | |
331 | ||
332 | /* | |
333 | * migrate_pages | |
334 | * | |
335 | * Two lists are passed to this function. The first list | |
336 | * contains the pages isolated from the LRU to be migrated. | |
337 | * The second list contains new pages that the pages isolated | |
338 | * can be moved to. If the second list is NULL then all | |
339 | * pages are swapped out. | |
340 | * | |
341 | * The function returns after 10 attempts or if no pages | |
342 | * are movable anymore because to has become empty | |
343 | * or no retryable pages exist anymore. | |
344 | * | |
345 | * Return: Number of pages not migrated when "to" ran empty. | |
346 | */ | |
347 | int migrate_pages(struct list_head *from, struct list_head *to, | |
348 | struct list_head *moved, struct list_head *failed) | |
349 | { | |
350 | int retry; | |
351 | int nr_failed = 0; | |
352 | int pass = 0; | |
353 | struct page *page; | |
354 | struct page *page2; | |
355 | int swapwrite = current->flags & PF_SWAPWRITE; | |
356 | int rc; | |
357 | ||
358 | if (!swapwrite) | |
359 | current->flags |= PF_SWAPWRITE; | |
360 | ||
361 | redo: | |
362 | retry = 0; | |
363 | ||
364 | list_for_each_entry_safe(page, page2, from, lru) { | |
365 | struct page *newpage = NULL; | |
366 | struct address_space *mapping; | |
367 | ||
368 | cond_resched(); | |
369 | ||
370 | rc = 0; | |
371 | if (page_count(page) == 1) | |
372 | /* page was freed from under us. So we are done. */ | |
373 | goto next; | |
374 | ||
375 | if (to && list_empty(to)) | |
376 | break; | |
377 | ||
378 | /* | |
379 | * Skip locked pages during the first two passes to give the | |
380 | * functions holding the lock time to release the page. Later we | |
381 | * use lock_page() to have a higher chance of acquiring the | |
382 | * lock. | |
383 | */ | |
384 | rc = -EAGAIN; | |
385 | if (pass > 2) | |
386 | lock_page(page); | |
387 | else | |
388 | if (TestSetPageLocked(page)) | |
389 | goto next; | |
390 | ||
391 | /* | |
392 | * Only wait on writeback if we have already done a pass where | |
393 | * we we may have triggered writeouts for lots of pages. | |
394 | */ | |
395 | if (pass > 0) { | |
396 | wait_on_page_writeback(page); | |
397 | } else { | |
398 | if (PageWriteback(page)) | |
399 | goto unlock_page; | |
400 | } | |
401 | ||
402 | /* | |
403 | * Anonymous pages must have swap cache references otherwise | |
404 | * the information contained in the page maps cannot be | |
405 | * preserved. | |
406 | */ | |
407 | if (PageAnon(page) && !PageSwapCache(page)) { | |
408 | if (!add_to_swap(page, GFP_KERNEL)) { | |
409 | rc = -ENOMEM; | |
410 | goto unlock_page; | |
411 | } | |
412 | } | |
413 | ||
414 | if (!to) { | |
415 | rc = swap_page(page); | |
416 | goto next; | |
417 | } | |
418 | ||
419 | newpage = lru_to_page(to); | |
420 | lock_page(newpage); | |
421 | ||
422 | /* | |
423 | * Pages are properly locked and writeback is complete. | |
424 | * Try to migrate the page. | |
425 | */ | |
426 | mapping = page_mapping(page); | |
427 | if (!mapping) | |
428 | goto unlock_both; | |
429 | ||
430 | if (mapping->a_ops->migratepage) { | |
431 | /* | |
432 | * Most pages have a mapping and most filesystems | |
433 | * should provide a migration function. Anonymous | |
434 | * pages are part of swap space which also has its | |
435 | * own migration function. This is the most common | |
436 | * path for page migration. | |
437 | */ | |
438 | rc = mapping->a_ops->migratepage(newpage, page); | |
439 | goto unlock_both; | |
440 | } | |
441 | ||
4c28f811 CL |
442 | /* Make sure the dirty bit is up to date */ |
443 | if (try_to_unmap(page, 1) == SWAP_FAIL) { | |
444 | rc = -EPERM; | |
445 | goto unlock_both; | |
446 | } | |
447 | ||
448 | if (page_mapcount(page)) { | |
449 | rc = -EAGAIN; | |
450 | goto unlock_both; | |
451 | } | |
452 | ||
b20a3503 CL |
453 | /* |
454 | * Default handling if a filesystem does not provide | |
455 | * a migration function. We can only migrate clean | |
456 | * pages so try to write out any dirty pages first. | |
457 | */ | |
458 | if (PageDirty(page)) { | |
459 | switch (pageout(page, mapping)) { | |
460 | case PAGE_KEEP: | |
461 | case PAGE_ACTIVATE: | |
462 | goto unlock_both; | |
463 | ||
464 | case PAGE_SUCCESS: | |
465 | unlock_page(newpage); | |
466 | goto next; | |
467 | ||
468 | case PAGE_CLEAN: | |
469 | ; /* try to migrate the page below */ | |
470 | } | |
471 | } | |
472 | ||
473 | /* | |
474 | * Buffers are managed in a filesystem specific way. | |
475 | * We must have no buffers or drop them. | |
476 | */ | |
477 | if (!page_has_buffers(page) || | |
478 | try_to_release_page(page, GFP_KERNEL)) { | |
479 | rc = migrate_page(newpage, page); | |
480 | goto unlock_both; | |
481 | } | |
482 | ||
483 | /* | |
484 | * On early passes with mapped pages simply | |
485 | * retry. There may be a lock held for some | |
486 | * buffers that may go away. Later | |
487 | * swap them out. | |
488 | */ | |
489 | if (pass > 4) { | |
490 | /* | |
491 | * Persistently unable to drop buffers..... As a | |
492 | * measure of last resort we fall back to | |
493 | * swap_page(). | |
494 | */ | |
495 | unlock_page(newpage); | |
496 | newpage = NULL; | |
497 | rc = swap_page(page); | |
498 | goto next; | |
499 | } | |
500 | ||
501 | unlock_both: | |
502 | unlock_page(newpage); | |
503 | ||
504 | unlock_page: | |
505 | unlock_page(page); | |
506 | ||
507 | next: | |
508 | if (rc == -EAGAIN) { | |
509 | retry++; | |
510 | } else if (rc) { | |
511 | /* Permanent failure */ | |
512 | list_move(&page->lru, failed); | |
513 | nr_failed++; | |
514 | } else { | |
515 | if (newpage) { | |
516 | /* Successful migration. Return page to LRU */ | |
517 | move_to_lru(newpage); | |
518 | } | |
519 | list_move(&page->lru, moved); | |
520 | } | |
521 | } | |
522 | if (retry && pass++ < 10) | |
523 | goto redo; | |
524 | ||
525 | if (!swapwrite) | |
526 | current->flags &= ~PF_SWAPWRITE; | |
527 | ||
528 | return nr_failed + retry; | |
529 | } | |
530 | ||
531 | /* | |
532 | * Migration function for pages with buffers. This function can only be used | |
533 | * if the underlying filesystem guarantees that no other references to "page" | |
534 | * exist. | |
535 | */ | |
536 | int buffer_migrate_page(struct page *newpage, struct page *page) | |
537 | { | |
538 | struct address_space *mapping = page->mapping; | |
539 | struct buffer_head *bh, *head; | |
540 | int rc; | |
541 | ||
542 | if (!mapping) | |
543 | return -EAGAIN; | |
544 | ||
545 | if (!page_has_buffers(page)) | |
546 | return migrate_page(newpage, page); | |
547 | ||
548 | head = page_buffers(page); | |
549 | ||
550 | rc = migrate_page_remove_references(newpage, page, 3); | |
551 | ||
552 | if (rc) | |
553 | return rc; | |
554 | ||
555 | bh = head; | |
556 | do { | |
557 | get_bh(bh); | |
558 | lock_buffer(bh); | |
559 | bh = bh->b_this_page; | |
560 | ||
561 | } while (bh != head); | |
562 | ||
563 | ClearPagePrivate(page); | |
564 | set_page_private(newpage, page_private(page)); | |
565 | set_page_private(page, 0); | |
566 | put_page(page); | |
567 | get_page(newpage); | |
568 | ||
569 | bh = head; | |
570 | do { | |
571 | set_bh_page(bh, newpage, bh_offset(bh)); | |
572 | bh = bh->b_this_page; | |
573 | ||
574 | } while (bh != head); | |
575 | ||
576 | SetPagePrivate(newpage); | |
577 | ||
578 | migrate_page_copy(newpage, page); | |
579 | ||
580 | bh = head; | |
581 | do { | |
582 | unlock_buffer(bh); | |
583 | put_bh(bh); | |
584 | bh = bh->b_this_page; | |
585 | ||
586 | } while (bh != head); | |
587 | ||
588 | return 0; | |
589 | } | |
590 | EXPORT_SYMBOL(buffer_migrate_page); | |
591 | ||
592 | /* | |
593 | * Migrate the list 'pagelist' of pages to a certain destination. | |
594 | * | |
595 | * Specify destination with either non-NULL vma or dest_node >= 0 | |
596 | * Return the number of pages not migrated or error code | |
597 | */ | |
598 | int migrate_pages_to(struct list_head *pagelist, | |
599 | struct vm_area_struct *vma, int dest) | |
600 | { | |
601 | LIST_HEAD(newlist); | |
602 | LIST_HEAD(moved); | |
603 | LIST_HEAD(failed); | |
604 | int err = 0; | |
605 | unsigned long offset = 0; | |
606 | int nr_pages; | |
607 | struct page *page; | |
608 | struct list_head *p; | |
609 | ||
610 | redo: | |
611 | nr_pages = 0; | |
612 | list_for_each(p, pagelist) { | |
613 | if (vma) { | |
614 | /* | |
615 | * The address passed to alloc_page_vma is used to | |
616 | * generate the proper interleave behavior. We fake | |
617 | * the address here by an increasing offset in order | |
618 | * to get the proper distribution of pages. | |
619 | * | |
620 | * No decision has been made as to which page | |
621 | * a certain old page is moved to so we cannot | |
622 | * specify the correct address. | |
623 | */ | |
624 | page = alloc_page_vma(GFP_HIGHUSER, vma, | |
625 | offset + vma->vm_start); | |
626 | offset += PAGE_SIZE; | |
627 | } | |
628 | else | |
629 | page = alloc_pages_node(dest, GFP_HIGHUSER, 0); | |
630 | ||
631 | if (!page) { | |
632 | err = -ENOMEM; | |
633 | goto out; | |
634 | } | |
635 | list_add_tail(&page->lru, &newlist); | |
636 | nr_pages++; | |
637 | if (nr_pages > MIGRATE_CHUNK_SIZE) | |
638 | break; | |
639 | } | |
640 | err = migrate_pages(pagelist, &newlist, &moved, &failed); | |
641 | ||
642 | putback_lru_pages(&moved); /* Call release pages instead ?? */ | |
643 | ||
644 | if (err >= 0 && list_empty(&newlist) && !list_empty(pagelist)) | |
645 | goto redo; | |
646 | out: | |
647 | /* Return leftover allocated pages */ | |
648 | while (!list_empty(&newlist)) { | |
649 | page = list_entry(newlist.next, struct page, lru); | |
650 | list_del(&page->lru); | |
651 | __free_page(page); | |
652 | } | |
653 | list_splice(&failed, pagelist); | |
654 | if (err < 0) | |
655 | return err; | |
656 | ||
657 | /* Calculate number of leftover pages */ | |
658 | nr_pages = 0; | |
659 | list_for_each(p, pagelist) | |
660 | nr_pages++; | |
661 | return nr_pages; | |
662 | } |