diff options
| -rw-r--r-- | mm/migrate.c | 48 |
1 files changed, 19 insertions, 29 deletions
diff --git a/mm/migrate.c b/mm/migrate.c index 89a6bc8cd30..a20cf12eded 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -622,7 +622,6 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, int *result = NULL; struct page *newpage = get_new_page(page, private, &result); int remap_swapcache = 1; - int rcu_locked = 0; int charge = 0; struct mem_cgroup *mem = NULL; struct anon_vma *anon_vma = NULL; @@ -694,20 +693,26 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, /* * 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. - * This rcu_read_lock() delays freeing anon_vma pointer until the end + * This get_anon_vma() delays freeing anon_vma pointer until the end * 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. */ if (PageAnon(page)) { - rcu_read_lock(); - rcu_locked = 1; - - /* Determine how to safely use anon_vma */ - if (!page_mapped(page)) { - if (!PageSwapCache(page)) - goto rcu_unlock; - + /* + * Only page_lock_anon_vma() understands the subtleties of + * getting a hold on an anon_vma from outside one of its mms. + */ + anon_vma = page_lock_anon_vma(page); + if (anon_vma) { + /* + * Take a reference count on the anon_vma if the + * page is mapped so that it is guaranteed to + * exist when the page is remapped later + */ + get_anon_vma(anon_vma); + page_unlock_anon_vma(anon_vma); + } 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 @@ -722,13 +727,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, */ remap_swapcache = 0; } else { - /* - * Take a reference count on the anon_vma if the - * page is mapped so that it is guaranteed to - * exist when the page is remapped later - */ - anon_vma = page_anon_vma(page); - get_anon_vma(anon_vma); + goto uncharge; } } @@ -745,16 +744,10 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, * free the metadata, so the page can be freed. */ if (!page->mapping) { - if (!PageAnon(page) && page_has_private(page)) { - /* - * Go direct to try_to_free_buffers() here because - * a) that's what try_to_release_page() would do anyway - * b) we may be under rcu_read_lock() here, so we can't - * use GFP_KERNEL which is what try_to_release_page() - * needs to be effective. - */ + VM_BUG_ON(PageAnon(page)); + if (page_has_private(page)) { try_to_free_buffers(page); - goto rcu_unlock; + goto uncharge; } goto skip_unmap; } @@ -768,14 +761,11 @@ skip_unmap: if (rc && remap_swapcache) remove_migration_ptes(page, page); -rcu_unlock: /* Drop an anon_vma reference if we took one */ if (anon_vma) drop_anon_vma(anon_vma); - if (rcu_locked) - rcu_read_unlock(); uncharge: if (!charge) mem_cgroup_end_migration(mem, page, newpage); |