See summary. If I leave the option --quiesce out, the snapshot completes successfully. This bug has already been reported to upstream, see: https://bugzilla.redhat.com/show_bug.cgi?id=1598084 Reproducible: Always Steps to Reproduce: 1. virsh -q snapshot-create-as "$domain_name" "$SNAPSHOT_PREFIX-$timestamp" --no-metadata --disk-only --atomic --quiesce 2. 3. Actual Results: "Timed out during operation: cannot acquire state change lock" Expected Results: First a request to quiesce the filesystems is sent to the qemu guest agent on the client. Subsequently snapshots are made of the images of the client KVM machine. As a work-around I now leave out the --quiesce option when making nightly snapshots. This is of course suboptimal.
The patch should have made it into 4.6.0 according to the git repository: https://www.redhat.com/archives/libvir-list/2018-July/msg00258.html