Comment 7 for bug 1641518

1) create volume xxx;
2）clone volume xxx: xxx-clone-1,xxx-clone-2,xxx-clone3
now ceph state is :
# rbd -p volumes ls -l
volume-xxx
volume-xxx@volume-xxx-clone-1.clone_snap
volume-xxx@volume-xxx-clone-2.clone_snap
volume-xxx@volume-xxx-clone-3.clone_snap
volume-xxx-clone-1
volume-xxx-clone-2
volume-xxx-clone-3

3) delete volume and clones concurrently
now ceph state is:
# rbd -p volumes ls -l
volume-xxx.deleted
volume-xxx.deleted@volume-xxx-clone-1.clone_snap

if i try like https://review.openstack.org/#/c/397863/, ceph state is the same, just no error message returned to user.