ceph: avoid repeatedly adding inode to mdsc->snap_flush_list

Otherwise, mdsc->snap_flush_list may get corrupted.

Cc: stable@vger.kernel.org
Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
index 041c27ea8de1..f74193da0e09 100644
--- a/fs/ceph/snap.c
+++ b/fs/ceph/snap.c
@@ -616,7 +616,8 @@ int __ceph_finish_cap_snap(struct ceph_inode_info *ci,
              capsnap->size);
 
         spin_lock(&mdsc->snap_flush_lock);
-        list_add_tail(&ci->i_snap_flush_item, &mdsc->snap_flush_list);
+        if (list_empty(&ci->i_snap_flush_item))
+                list_add_tail(&ci->i_snap_flush_item, &mdsc->snap_flush_list);
         spin_unlock(&mdsc->snap_flush_lock);
         return 1;  /* caller may want to ceph_flush_snaps */
 }