Certainly, thanks for your help!
I put cinderlib and engine.log here: http://www.mulix.org/misc/ovirt-logs-20220223123641.tar.gz
If you grep for 'mulivm1' you will see for example:

2022-02-22 04:31:04,473-05 ERROR [org.ovirt.engine.core.vdsbroker.vdsbroker.HotPlugDiskVDSCommand] (default task-10) [36d8a122] Command 'HotPlugDiskVDSCommand(HostName = client1, HotPlugDiskVDSParameters:{hostId='fc5c2860-36b1-4213-843f-10ca7b35556c', vmId='e13f73a0-8e20-4ec3-837f-aeacc082c7aa', diskId='d1e1286b-38cc-4d56-9d4e-f331ffbe830f', addressMap='[bus=0, controller=0, unit=2, type=drive, target=0]'})' execution failed: VDSGenericException: VDSErrorException: Failed to HotPlugDiskVDS, error = Failed to bind /dev/mapper/ on to /var/run/libvirt/qemu/21-mulivm1.mapper.: Not a directory, code = 45

Please let me know what other information will be useful and I will prove.

Cheers,
Muli

On Wed, Feb 23, 2022 at 11:14 AM Benny Zlotnik <bzlotnik@redhat.com> wrote:
Hi,

We haven't tested this, and we do not have any code to handle nvme/tcp
drivers, only iscsi and rbd. Given the path seen in the logs
'/dev/mapper', it looks like it might require code changes to support
this.
Can you share cinderlib[1] and engine logs to see what is returned by
the driver? I may be able to estimate what would be required (it's
possible that it would be enough to just change the handling of the
path in the engine)

[1] /var/log/ovirt-engine/cinderlib/cinderlib//log

On Wed, Feb 23, 2022 at 10:54 AM <muli@lightbitslabs.com> wrote:
>
> Hi everyone,
>
> We are trying to set up ovirt (4.3.10 at the moment, customer preference) to use Lightbits (https://www.lightbitslabs.com) storage via our openstack cinder driver with cinderlib. The cinderlib and cinder driver bits are working fine but when ovirt tries to attach the device to a VM we get the following error:
>
> libvirt:  error : cannot create file '/var/run/libvirt/qemu/18-mulivm1.dev/mapper/': Is a directory
>
> We get the same error regardless of whether I try to run the VM or try to attach the device while it is running. The error appears to come from vdsm which passes /dev/mapper as the prefered device?
>
> 2022-02-22 09:50:11,848-0500 INFO  (vm/3ae7dcf4) [vdsm.api] FINISH appropriateDevice return={'path': '/dev/mapper/', 'truesize': '53687091200', 'apparentsize': '53687091200'} from=internal, task_id=77f40c4e-733d-4d82-b418-aaeb6b912d39 (api:54)
> 2022-02-22 09:50:11,849-0500 INFO  (vm/3ae7dcf4) [vds] prepared volume path: /dev/mapper/ (clientIF:510)
>
> Suggestions for how to debug this further? Is this a known issue? Did anyone get nvme/tcp storage working with ovirt and/or vdsm?
>
> Thanks,
> Muli
>
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