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-rw-r--r--mm/rmap.c13
1 files changed, 8 insertions, 5 deletions
diff --git a/mm/rmap.c b/mm/rmap.c
index ba58ca3..6bada99 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;