Comment 12 for bug 1587065

Steps to reproduce

uvt-simplestreams-libvirt --verbose sync --source http://cloud-images.ubuntu.com/daily arch=amd64 release=xenial label=daily
uvt-kvm create --password ubuntu x-freeze arch=amd64 release=xenial label=daily

Add this to the guest definition and restart it
<channel type='unix'>
   <source mode='bind'/>
   <target type='virtio' name='org.qemu.guest_agent.0'/>
</channel>

From the host freeze and thaw it:
$ virsh domfsfreeze x-freeze
$ virsh domfsthaw x-freeze

# The above works

In the Guest then add a bind mount to trigger the issue
$ sudo mkdir /mnt/test
$ sudo mount -o bind / /mnt/test/

Then again try to freeze/unfreeze
$ virsh domfsfreeze x-freeze
error: Unable to freeze filesystems
error: internal error: unable to execute QEMU agent command 'guest-fsfreeze-freeze': failed to freeze /: Device or resource busy

I installed a fix from my PPA [1] and with that it works just fine now.
Proposing an MP for review by the team, to afterwards move on into SRU processing.

[1]: https://launchpad.net/~ci-train-ppa-service/+archive/ubuntu/3310