[PATCH 4.9 03/63] ceph: avoid repeatedly adding inode to mdsc->snap_flush_list

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Yan, Zheng <zyan@xxxxxxxxxx>

commit 04242ff3ac0abbaa4362f97781dac268e6c3541a upstream.

Otherwise, mdsc->snap_flush_list may get corrupted.

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: "Yan, Zheng" <zyan@xxxxxxxxxx>
Reviewed-by: Ilya Dryomov <idryomov@xxxxxxxxx>
Signed-off-by: Ilya Dryomov <idryomov@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/ceph/snap.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/ceph/snap.c
+++ b/fs/ceph/snap.c
@@ -609,7 +609,8 @@ int __ceph_finish_cap_snap(struct ceph_i
 	     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 */
 }