[pve-devel] VM locked after failed Snapshot

[Stefan Priebe - Profihost AG]

Hi,

today i had the following problem.

1.) i wanted to create a snapshot of a vm
2.) it failed for unknown reason and i had the following output (PVE
Webgui):

image has watchers - not removing
Removing image: 0% complete...failed.
rbd: error: image still has watchers
TASK ERROR: received interrupt

3.) The VM was than in a locked state (VM is locked (snapshot))

I see multiple problems here.

1.) lock state should be removed by PVE in case of a failure.

Currently snapshot_create calls snapshot_prepare to set the lock. And at
the end snapshot_commit deletes the log.

But currently in case of $err

    if ($err) {
        warn "snapshot create failed: starting cleanup\n";
        eval { snapshot_delete($vmid, $snapname, 0, $drivehash); };
        warn $@ if $@;
        die $err;
    }

The lock isn't removed.

What is the correct way to remove a lock in this case?

2.) in case of an unexpected failure or signal ceph/rbd does not remove
it's watcher from the image. So the snapshot_delete failed in this case.

Output:

image has watchers - not removing
Removing image: 0% complete...failed.
rbd: error: image still has watchers

rbd has an automatic timeout after 30s should PVE handle this by waiting
30s and try it again?

Greets,
Stefan