diff options
| -rw-r--r-- | mm/rmap.c | 13 |
1 files changed, 8 insertions, 5 deletions
diff --git a/mm/rmap.c b/mm/rmap.c index ba58ca36fc9..6bada99cd61 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -405,6 +405,7 @@ out: struct anon_vma *page_lock_anon_vma(struct page *page) { struct anon_vma *anon_vma = NULL; + struct anon_vma *root_anon_vma; unsigned long anon_mapping; rcu_read_lock(); @@ -415,13 +416,15 @@ struct anon_vma *page_lock_anon_vma(struct page *page) goto out; anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); - if (mutex_trylock(&anon_vma->root->mutex)) { + root_anon_vma = ACCESS_ONCE(anon_vma->root); + if (mutex_trylock(&root_anon_vma->mutex)) { /* - * If we observe a !0 refcount, then holding the lock ensures - * the anon_vma will not go away, see __put_anon_vma(). + * If the page is still mapped, then this anon_vma is still + * its anon_vma, and holding the mutex ensures that it will + * not go away, see __put_anon_vma(). */ - if (!atomic_read(&anon_vma->refcount)) { - anon_vma_unlock(anon_vma); + if (!page_mapped(page)) { + mutex_unlock(&root_anon_vma->mutex); anon_vma = NULL; } goto out; |