Created attachment 1677092 [details]
Libvirtd log

Steps to Reproduce:
1.Prepare an image in ceph server and create snapshot
# qemu-img create -f raw rbd:libvirt-pool/test.img:id=admin:key=$key:auth_supported=cephx:mon_host=$ip 100M

# rbd snap create libvirt-pool/test.img@sn1 --keyring /etc/ceph/ceph.client.admin.keyring -c /etc/ceph/ceph.conf

# rbd snap ls libvirt-pool/test.img --keyring /etc/ceph/ceph.client.admin.keyring -c /etc/ceph/ceph.conf
SNAPID NAME SIZE    PROTECTED TIMESTAMP                
     9 sn1  100 MiB           Tue Apr  7 16:26:26 2020

2.Create a storage rbd pool
# virsh pool-dumpxml rbd-pool
<pool type='rbd'>
  <name>rbd-pool</name>
  <uuid>8c167270-e759-4e14-91f5-1f5ef3dfb8d1</uuid>
  <capacity unit='bytes'>169651208192</capacity>
  <allocation unit='bytes'>4523556864</allocation>
  <available unit='bytes'>45678919680</available>
  <source>
    <host name='10.66.146.31' port='6789'/>
    <name>libvirt-pool</name>
    <auth type='chap' username='admin'>
      <secret type='ceph' usage='client.ceph'/>
    </auth>
  </source>
</pool>

# virsh vol-list rbd-pool
 Name             Path
-----------------------------------------------
 test.img         libvirt-pool/test.img

3.Define a guest with this rbd image
# virsh define test1111.xml
Domain test1 defined from test1111.xml

# virsh dumpxml test1 |grep "auth" -A5 -B5
...
    <disk type='network' device='disk'>
      <driver name='qemu' type='raw' cache='none'/>
      <source protocol='rbd' name='libvirt-pool/test.img'>
        <host name='$ip'/>
        <auth username='admin'>
          <secret type='ceph' usage='client.ceph'/>
        </auth>
      </source>
      <backingStore/>
      <target dev='vda' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x05' slot='0x00' function='0x0'/>
    </disk>
...

Start the domain and it works well:
# virsh start test1
Domain test1 started

4.Destroy and undefine the domain with removing its backing volume
# virsh destroy test1
Domain test1 destroyed

# virsh undefine test1 --remove-all-storage --delete-storage-volume-snapshots
Domain test1 has been undefined
error: Failed to remove storage volume 'vda'(libvirt-pool/test.img)
error: failed to remove volume 'libvirt-pool/test.img': No such file or directory

Double check in libvirt and ceph server:
# virsh pool-refresh rbd-pool
Pool rbd-pool refreshed

# virsh vol-list rbd-pool
 Name             Path
-----------------------------------------------
 test.img         libvirt-pool/test.img

# rbd snap ls libvirt-pool/test.img --keyring /etc/ceph/ceph.client.admin.keyring -c /etc/ceph/ceph.conf
SNAPID NAME SIZE    PROTECTED TIMESTAMP                
     9 sn1  100 MiB           Tue Apr  7 16:26:26 2020


Actual results:
As step4,undefine with removing its backing volume failed,and the error should be updated.

Expected results:
Undefine the domain and remove the backing image in rbd-pool.

Additional info:
And according to the man page:
The  --delete-storage-volume-snapshots  (previously  --delete-snapshots)  flag specifies that any snapshots associated with the storage volume should be deleted as well. 
So it should be successful here.