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git.ipfire.org Git - thirdparty/kernel/stable.git/blob - mm/migrate.c
2 * Memory Migration functionality - linux/mm/migration.c
4 * Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter
6 * Page migration was first developed in the context of the memory hotplug
7 * project. The main authors of the migration code are:
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>
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>
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>
30 /* The maximum number of pages to take off the LRU for migration */
31 #define MIGRATE_CHUNK_SIZE 256
33 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
36 * Isolate one page from the LRU lists. If successful put it onto
37 * the indicated list with elevated page count.
40 * -EBUSY: page not on LRU list
41 * 0: page removed from LRU list and added to the specified list.
43 int isolate_lru_page(struct page
*page
, struct list_head
*pagelist
)
48 struct zone
*zone
= page_zone(page
);
50 spin_lock_irq(&zone
->lru_lock
);
56 del_page_from_active_list(zone
, page
);
58 del_page_from_inactive_list(zone
, page
);
59 list_add_tail(&page
->lru
, pagelist
);
61 spin_unlock_irq(&zone
->lru_lock
);
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
71 int migrate_prep(void)
73 /* Must have swap device for migration */
74 if (nr_swap_pages
<= 0)
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.
88 static inline void move_to_lru(struct page
*page
)
91 if (PageActive(page
)) {
93 * lru_cache_add_active checks that
94 * the PG_active bit is off.
96 ClearPageActive(page
);
97 lru_cache_add_active(page
);
105 * Add isolated pages on the list back to the LRU.
107 * returns the number of pages put back.
109 int putback_lru_pages(struct list_head
*l
)
115 list_for_each_entry_safe(page
, page2
, l
, lru
) {
123 * swapout a single page
124 * page is locked upon entry, unlocked on exit
126 static int swap_page(struct page
*page
)
128 struct address_space
*mapping
= page_mapping(page
);
130 if (page_mapped(page
) && mapping
)
131 if (try_to_unmap(page
, 1) != SWAP_SUCCESS
)
134 if (PageDirty(page
)) {
135 /* Page is dirty, try to write it out here */
136 switch(pageout(page
, mapping
)) {
145 ; /* try to free the page below */
149 if (PagePrivate(page
)) {
150 if (!try_to_release_page(page
, GFP_KERNEL
) ||
151 (!mapping
&& page_count(page
) == 1))
155 if (remove_mapping(mapping
, page
)) {
169 * Replace the page in the mapping.
171 * The number of remaining references must be:
172 * 1 for anonymous pages without a mapping
173 * 2 for pages with a mapping
174 * 3 for pages with a mapping and PagePrivate set.
176 static int migrate_page_move_mapping(struct address_space
*mapping
,
177 struct page
*newpage
, struct page
*page
)
179 struct page
**radix_pointer
;
181 write_lock_irq(&mapping
->tree_lock
);
183 radix_pointer
= (struct page
**)radix_tree_lookup_slot(
187 if (!page_mapping(page
) ||
188 page_count(page
) != 2 + !!PagePrivate(page
) ||
189 *radix_pointer
!= page
) {
190 write_unlock_irq(&mapping
->tree_lock
);
195 * Now we know that no one else is looking at the page.
198 if (PageSwapCache(page
)) {
199 SetPageSwapCache(newpage
);
200 set_page_private(newpage
, page_private(page
));
203 *radix_pointer
= newpage
;
205 write_unlock_irq(&mapping
->tree_lock
);
211 * Copy the page to its new location
213 static void migrate_page_copy(struct page
*newpage
, struct page
*page
)
215 copy_highpage(newpage
, page
);
218 SetPageError(newpage
);
219 if (PageReferenced(page
))
220 SetPageReferenced(newpage
);
221 if (PageUptodate(page
))
222 SetPageUptodate(newpage
);
223 if (PageActive(page
))
224 SetPageActive(newpage
);
225 if (PageChecked(page
))
226 SetPageChecked(newpage
);
227 if (PageMappedToDisk(page
))
228 SetPageMappedToDisk(newpage
);
230 if (PageDirty(page
)) {
231 clear_page_dirty_for_io(page
);
232 set_page_dirty(newpage
);
235 ClearPageSwapCache(page
);
236 ClearPageActive(page
);
237 ClearPagePrivate(page
);
238 set_page_private(page
, 0);
239 page
->mapping
= NULL
;
242 * If any waiters have accumulated on the new page then
245 if (PageWriteback(newpage
))
246 end_page_writeback(newpage
);
249 /************************************************************
250 * Migration functions
251 ***********************************************************/
253 /* Always fail migration. Used for mappings that are not movable */
254 int fail_migrate_page(struct address_space
*mapping
,
255 struct page
*newpage
, struct page
*page
)
259 EXPORT_SYMBOL(fail_migrate_page
);
262 * Common logic to directly migrate a single page suitable for
263 * pages that do not use PagePrivate.
265 * Pages are locked upon entry and exit.
267 int migrate_page(struct address_space
*mapping
,
268 struct page
*newpage
, struct page
*page
)
272 BUG_ON(PageWriteback(page
)); /* Writeback must be complete */
274 rc
= migrate_page_move_mapping(mapping
, newpage
, page
);
279 migrate_page_copy(newpage
, page
);
282 * Remove auxiliary swap entries and replace
283 * them with real ptes.
285 * Note that a real pte entry will allow processes that are not
286 * waiting on the page lock to use the new page via the page tables
287 * before the new page is unlocked.
289 remove_from_swap(newpage
);
292 EXPORT_SYMBOL(migrate_page
);
295 * Migration function for pages with buffers. This function can only be used
296 * if the underlying filesystem guarantees that no other references to "page"
299 int buffer_migrate_page(struct address_space
*mapping
,
300 struct page
*newpage
, struct page
*page
)
302 struct buffer_head
*bh
, *head
;
305 if (!page_has_buffers(page
))
306 return migrate_page(mapping
, newpage
, page
);
308 head
= page_buffers(page
);
310 rc
= migrate_page_move_mapping(mapping
, newpage
, page
);
319 bh
= bh
->b_this_page
;
321 } while (bh
!= head
);
323 ClearPagePrivate(page
);
324 set_page_private(newpage
, page_private(page
));
325 set_page_private(page
, 0);
331 set_bh_page(bh
, newpage
, bh_offset(bh
));
332 bh
= bh
->b_this_page
;
334 } while (bh
!= head
);
336 SetPagePrivate(newpage
);
338 migrate_page_copy(newpage
, page
);
344 bh
= bh
->b_this_page
;
346 } while (bh
!= head
);
350 EXPORT_SYMBOL(buffer_migrate_page
);
352 static int fallback_migrate_page(struct address_space
*mapping
,
353 struct page
*newpage
, struct page
*page
)
356 * Default handling if a filesystem does not provide
357 * a migration function. We can only migrate clean
358 * pages so try to write out any dirty pages first.
360 if (PageDirty(page
)) {
361 switch (pageout(page
, mapping
)) {
367 /* Relock since we lost the lock */
369 /* Must retry since page state may have changed */
373 ; /* try to migrate the page below */
378 * Buffers may be managed in a filesystem specific way.
379 * We must have no buffers or drop them.
381 if (page_has_buffers(page
) &&
382 !try_to_release_page(page
, GFP_KERNEL
))
385 return migrate_page(mapping
, newpage
, page
);
391 * Two lists are passed to this function. The first list
392 * contains the pages isolated from the LRU to be migrated.
393 * The second list contains new pages that the pages isolated
394 * can be moved to. If the second list is NULL then all
395 * pages are swapped out.
397 * The function returns after 10 attempts or if no pages
398 * are movable anymore because to has become empty
399 * or no retryable pages exist anymore.
401 * Return: Number of pages not migrated when "to" ran empty.
403 int migrate_pages(struct list_head
*from
, struct list_head
*to
,
404 struct list_head
*moved
, struct list_head
*failed
)
411 int swapwrite
= current
->flags
& PF_SWAPWRITE
;
415 current
->flags
|= PF_SWAPWRITE
;
420 list_for_each_entry_safe(page
, page2
, from
, lru
) {
421 struct page
*newpage
= NULL
;
422 struct address_space
*mapping
;
427 if (page_count(page
) == 1)
428 /* page was freed from under us. So we are done. */
431 if (to
&& list_empty(to
))
435 * Skip locked pages during the first two passes to give the
436 * functions holding the lock time to release the page. Later we
437 * use lock_page() to have a higher chance of acquiring the
444 if (TestSetPageLocked(page
))
448 * Only wait on writeback if we have already done a pass where
449 * we we may have triggered writeouts for lots of pages.
452 wait_on_page_writeback(page
);
454 if (PageWriteback(page
))
459 * Anonymous pages must have swap cache references otherwise
460 * the information contained in the page maps cannot be
463 if (PageAnon(page
) && !PageSwapCache(page
)) {
464 if (!add_to_swap(page
, GFP_KERNEL
)) {
471 rc
= swap_page(page
);
476 * Establish swap ptes for anonymous pages or destroy pte
479 * In order to reestablish file backed mappings the fault handlers
480 * will take the radix tree_lock which may then be used to stop
481 * processses from accessing this page until the new page is ready.
483 * A process accessing via a swap pte (an anonymous page) will take a
484 * page_lock on the old page which will block the process until the
485 * migration attempt is complete. At that time the PageSwapCache bit
486 * will be examined. If the page was migrated then the PageSwapCache
487 * bit will be clear and the operation to retrieve the page will be
488 * retried which will find the new page in the radix tree. Then a new
489 * direct mapping may be generated based on the radix tree contents.
491 * If the page was not migrated then the PageSwapCache bit
492 * is still set and the operation may continue.
495 if (try_to_unmap(page
, 1) == SWAP_FAIL
)
496 /* A vma has VM_LOCKED set -> permanent failure */
500 if (page_mapped(page
))
503 newpage
= lru_to_page(to
);
505 /* Prepare mapping for the new page.*/
506 newpage
->index
= page
->index
;
507 newpage
->mapping
= page
->mapping
;
510 * Pages are properly locked and writeback is complete.
511 * Try to migrate the page.
513 mapping
= page_mapping(page
);
517 if (mapping
->a_ops
->migratepage
)
519 * Most pages have a mapping and most filesystems
520 * should provide a migration function. Anonymous
521 * pages are part of swap space which also has its
522 * own migration function. This is the most common
523 * path for page migration.
525 rc
= mapping
->a_ops
->migratepage(mapping
,
528 rc
= fallback_migrate_page(mapping
, newpage
, page
);
531 unlock_page(newpage
);
539 newpage
->mapping
= NULL
;
544 /* Permanent failure */
545 list_move(&page
->lru
, failed
);
550 /* Successful migration. Return page to LRU */
551 move_to_lru(newpage
);
553 list_move(&page
->lru
, moved
);
556 if (retry
&& pass
++ < 10)
560 current
->flags
&= ~PF_SWAPWRITE
;
562 return nr_failed
+ retry
;
566 * Migrate the list 'pagelist' of pages to a certain destination.
568 * Specify destination with either non-NULL vma or dest_node >= 0
569 * Return the number of pages not migrated or error code
571 int migrate_pages_to(struct list_head
*pagelist
,
572 struct vm_area_struct
*vma
, int dest
)
578 unsigned long offset
= 0;
585 list_for_each(p
, pagelist
) {
588 * The address passed to alloc_page_vma is used to
589 * generate the proper interleave behavior. We fake
590 * the address here by an increasing offset in order
591 * to get the proper distribution of pages.
593 * No decision has been made as to which page
594 * a certain old page is moved to so we cannot
595 * specify the correct address.
597 page
= alloc_page_vma(GFP_HIGHUSER
, vma
,
598 offset
+ vma
->vm_start
);
602 page
= alloc_pages_node(dest
, GFP_HIGHUSER
, 0);
608 list_add_tail(&page
->lru
, &newlist
);
610 if (nr_pages
> MIGRATE_CHUNK_SIZE
)
613 err
= migrate_pages(pagelist
, &newlist
, &moved
, &failed
);
615 putback_lru_pages(&moved
); /* Call release pages instead ?? */
617 if (err
>= 0 && list_empty(&newlist
) && !list_empty(pagelist
))
620 /* Return leftover allocated pages */
621 while (!list_empty(&newlist
)) {
622 page
= list_entry(newlist
.next
, struct page
, lru
);
623 list_del(&page
->lru
);
626 list_splice(&failed
, pagelist
);
630 /* Calculate number of leftover pages */
632 list_for_each(p
, pagelist
)