Avoiding lockspace already exists error from virtlockd

[Jim Fehlig]

Hi All!

I received a bug report about virtlockd emitting an error whenever libvirtd is 
(re)started

May 25 15:44:31 virt81 virtlockd[7723]: Requested operation is not valid: 
Lockspace for path /data/libvirtd/lockspace already exists

The problem is easily reproducible with git master by enabling lockd in 
qemu.conf, setting file_lockspace_dir in qemu-lockd.conf, then restarting libvirtd.

If I understand the code correctly, when the qemu driver loads, it calls 
virLockManagerPluginNew, which dlopens lockd.so and calls drvInit, aka 
virLockManagerLockDaemonInit. Here the driver object is created, config loaded, 
and virLockManagerLockDaemonSetupLockspace is called. 
virLockManagerLockDaemonSetupLockspace sends 
virLockSpaceProtocolCreateLockSpaceArgs rpc to virtlockd, where it is dispatched 
to virLockSpaceProtocolDispatchCreateLockSpace. Alas we encounter the error when 
virLockDaemonFindLockSpace finds the existing lockspace.

I'm not really sure how to go about fixing it and fishing for opinions. 
virLockManagerLockDaemonSetupLockspace already has some code to handle the error

https://gitlab.com/libvirt/libvirt/-/blob/master/src/locking/lock_driver_lockd.c#L286

Since libvirtd ignores VIR_ERR_OPERATION_INVALID, should virtlockd be changed to 
not return error in that case? It would be better if libvirtd knew it already 
told virtlockd to configure the lockspace and avoid needlessly doing it again.

BTW, this cosmetic problem is exasperated by the default '--timeout 120' option 
to libvirtd, since it results in more daemon restarts.

Thanks for any suggestions!
Jim