From: "Yan, Zheng" <zyan@redhat.com>
Date: Mon, 11 Feb 2019 15:18:52 +0800
Subject: ceph: avoid repeatedly adding inode to mdsc->snap_flush_list
Git-commit: 04242ff3ac0abbaa4362f97781dac268e6c3541a
Patch-mainline: v5.0-rc8
References: bsc#1126790 bsc#1126775

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>
Acked-by: Luis Henriques <lhenriques@suse.com>
---
 fs/ceph/snap.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/ceph/snap.c
+++ b/fs/ceph/snap.c
@@ -615,7 +615,8 @@ 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 */
 }