diff options
| -rw-r--r-- | mm/migrate.c | 17 | ||||
| -rw-r--r-- | mm/rmap.c | 42 |
2 files changed, 31 insertions, 28 deletions
diff --git a/mm/migrate.c b/mm/migrate.c index 34132f8e910..e4a5c912983 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -721,15 +721,11 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, * 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); + anon_vma = page_get_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 + * Anon page */ - 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 @@ -857,13 +853,8 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, lock_page(hpage); } - if (PageAnon(hpage)) { - anon_vma = page_lock_anon_vma(hpage); - if (anon_vma) { - get_anon_vma(anon_vma); - page_unlock_anon_vma(anon_vma); - } - } + if (PageAnon(hpage)) + anon_vma = page_get_anon_vma(hpage); try_to_unmap(hpage, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS); diff --git a/mm/rmap.c b/mm/rmap.c index cc140811af5..d271845d7d1 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -337,9 +337,9 @@ void __init anon_vma_init(void) * that the anon_vma pointer from page->mapping is valid if there is a * mapcount, we can dereference the anon_vma after observing those. */ -struct anon_vma *page_lock_anon_vma(struct page *page) +struct anon_vma *page_get_anon_vma(struct page *page) { - struct anon_vma *anon_vma, *root_anon_vma; + struct anon_vma *anon_vma = NULL; unsigned long anon_mapping; rcu_read_lock(); @@ -350,30 +350,42 @@ struct anon_vma *page_lock_anon_vma(struct page *page) goto out; anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); - root_anon_vma = ACCESS_ONCE(anon_vma->root); - spin_lock(&root_anon_vma->lock); + if (!atomic_inc_not_zero(&anon_vma->refcount)) { + anon_vma = NULL; + goto out; + } /* * If this page is still mapped, then its anon_vma cannot have been - * freed. But if it has been unmapped, we have no security against - * the anon_vma structure being freed and reused (for another anon_vma: - * SLAB_DESTROY_BY_RCU guarantees that - so the spin_lock above cannot - * corrupt): with anon_vma_prepare() or anon_vma_fork() redirecting - * anon_vma->root before page_unlock_anon_vma() is called to unlock. + * freed. But if it has been unmapped, we have no security against the + * anon_vma structure being freed and reused (for another anon_vma: + * SLAB_DESTROY_BY_RCU guarantees that - so the atomic_inc_not_zero() + * above cannot corrupt). */ - if (page_mapped(page)) - return anon_vma; - - spin_unlock(&root_anon_vma->lock); + if (!page_mapped(page)) { + put_anon_vma(anon_vma); + anon_vma = NULL; + } out: rcu_read_unlock(); - return NULL; + + return anon_vma; +} + +struct anon_vma *page_lock_anon_vma(struct page *page) +{ + struct anon_vma *anon_vma = page_get_anon_vma(page); + + if (anon_vma) + anon_vma_lock(anon_vma); + + return anon_vma; } void page_unlock_anon_vma(struct anon_vma *anon_vma) { anon_vma_unlock(anon_vma); - rcu_read_unlock(); + put_anon_vma(anon_vma); } /* |