Instances are locked and unable to start after server crash (queens)

[Jacolex]

After restarting crashed host, disks of hosted instances on nfs are locked and cannot be restarted:

libvirtError: internal error: process exited while connecting to monitor: 2018-10-10T10:16:09.816477Z qemu-system-x86_64: -drive file=/var/lib/nova/instances/ed7760a8-3008-4feb-83f3-3b753b0e7d6e/disk,format=qcow2,if=none,id=drive-virtio-disk0,cache=none: Failed to get "write" lock
ERROR nova.compute.manager [instance: ed7760a8-3008-4feb-83f3-3b753b0e7d6e] Is another process using the image?

The same situation occurs on other compute nodes connected to the same shared file system, after evacuate instances. So it seems that disks are locked by libvirt in an unknown, undocumented way. As workaround I had to make copy of all failed instances, delete their disk files and restore them from copy. After that instances started successfully.

If there is other solution to unlock those instance disks, please share.

[Balazs Gibizer (balazs-gibizer)]

This is more a libvirt / nfs question than a nova question. I suggest to reach out to the libvirt community: https://libvirt.org/bugs.html