diff options
| -rw-r--r-- | mm/migrate.c | 36 |
1 files changed, 10 insertions, 26 deletions
diff --git a/mm/migrate.c b/mm/migrate.c index 7b44ebdf2d26..08a7b6c4c266 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -819,6 +819,7 @@ static int __unmap_and_move(struct page *page, struct page *newpage, goto out_unlock; wait_on_page_writeback(page); } + /* * By try_to_unmap(), page->mapcount goes down to 0 here. In this case, * we cannot notice that anon_vma is freed while we migrates a page. @@ -826,34 +827,15 @@ static int __unmap_and_move(struct page *page, struct page *newpage, * of migration. File cache pages are no problem because of page_lock() * File Caches may use write_page() or lock_page() in migration, then, * just care Anon page here. + * + * Only page_get_anon_vma() understands the subtleties of + * getting a hold on an anon_vma from outside one of its mms. + * But if we cannot get anon_vma, then we won't need it anyway, + * because that implies that the anon page is no longer mapped + * (and cannot be remapped so long as we hold the page lock). */ - if (PageAnon(page) && !PageKsm(page)) { - /* - * Only page_lock_anon_vma_read() understands the subtleties of - * getting a hold on an anon_vma from outside one of its mms. - */ + if (PageAnon(page) && !PageKsm(page)) anon_vma = page_get_anon_vma(page); - if (anon_vma) { - /* - * Anon page - */ - } else if (PageSwapCache(page)) { - /* - * We cannot be sure that the anon_vma of an unmapped - * swapcache page is safe to use because we don't - * know in advance if the VMA that this page belonged - * to still exists. If the VMA and others sharing the - * data have been freed, then the anon_vma could - * already be invalid. - * - * To avoid this possibility, swapcache pages get - * migrated but are not remapped when migration - * completes - */ - } else { - goto out_unlock; - } - } /* * Block others from accessing the new page when we get around to @@ -898,6 +880,8 @@ static int __unmap_and_move(struct page *page, struct page *newpage, } } else if (page_mapped(page)) { /* Establish migration ptes */ + VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma, + page); try_to_unmap(page, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS); page_was_mapped = 1; |