NBD device doesn't get disconnected after terminating LXC instance

[bastichelaar]

Steps to reproduce:

- Create a LXC instance
- Terminate the instance
- The qemu-nbd device is still connected

Attached is a proposed solution. I'm not a very good Python programmer, but this does the job.

[Chuck Short (zulcss)]

lgtm

[Chuck Short (zulcss)]

Im not able to reproduce this.

[Thierry Carrez (ttx)]

@bas-t: can you still reproduce ? Could you give us more details ?

[bastichelaar (bas-t)]

Ok, a little bit more details. My situation:

- I'm not using NBD anymore, so this is for normal LXC mounted chroots
- I'm using Nova Cactus

To reproduce this bug:

- Run an instance with Nova (with LXC / Libvirt hypervisor)
- Reboot the system while having a running instance
- When the system is rebooted, the instances are not mounted anymore, so when I try to terminate the instance it complains that it cannot unmount the LXC chroot, and therefore cannot terminate the instance

I created a small two line patch, that first checks if that directory is mounted. If so, it unmounts the directory. If not, it continues. I have no errors anymore.

Let me know if anybody can reproduce this bug.

[Thierry Carrez (ttx)]

Maybe it's a Cactus-specific issue, which would explain why Chuck doesn't reproduce it... it's great that you have a workaround for it. Any chance you could spin up a diablo-4 setup and doublecheck that the issue is gone ?

[bastichelaar (bas-t)]

I upgraded to Diablo (without many problems btw), and the problem is still there. In fact, it's a combination of two bugs:

- While terminating, it tries to unmount the mounted root of the instance. If the root is not mounted (due to a reboot), it fails.
- When it is mounted, it umounts correctly, but then tries to umount the loop device. There is a bug in this command.

Attached a patch, which will fix both issues.

[Thierry Carrez (ttx)]

Sounds sane -- Chuck can you confirm the fix ?

[Thierry Carrez (ttx)]

See also duplicate bug 841051

[Thierry Carrez (ttx)]

and bug 841069.