[ovirt-users] Discard after Delete

Hi list, I forgot to check "Discard after Delete" when creating a new volume. Is there a way (other than to empty the volume) to reclaim free blocks. In https://bugzilla.redhat.com/show_bug.cgi?id=981626 I read about blkdiscard, but as far as I understand it will erase my VMs ... Thanks for your answers Joris