[libvirt] [PATCH] qemu: Don't track quiesced state of FSs

[Jiri Denemark]

On Thu, Nov 27, 2014 at 13:27:25 +0100, Michal Privoznik wrote:
> https://bugzilla.redhat.com/show_bug.cgi?id=1160084
> 
> As of b6d4dad11b (1.2.5) we are trying to keep the status of FSFreeze
> in the guest. Even though I've tried to fixed couple of corner cases

s/fixed/fix/

> (6ea54769ba18), it occurred to me just recently, that the approach is
> broken by design. Firstly, there are many other ways to talk to
> qemu-ga (even through libvirt) that filesystems can be thawed (e.g.
> qemu-agent-command) without libvirt noticing. Moreover, there are
> plenty of ways to thaw filesystems without even qemu-ga noticing (yes,
> qemu-ga keeps internal track of FSFreeze status). So, instead of
> keeping the track ourselves, or asking qemu-ga for stale state, it's
> the best to let qemu-ga deal with that (and possibly let guest kernel
> propagate an error).
> 
> Moreover, there's one bug with the following approach, if fsfreeze
> command failed, we've executed fsthaw subsequently. So issuing
> domfsfreeze in virsh gave the following result:
> 
> virsh # domfsfreeze gentoo
> Froze 1 filesystem(s)
> 
> virsh # domfsfreeze gentoo
> error: Unable to freeze filesystems
> error: internal error: unable to execute QEMU agent command 'guest-fsfreeze-freeze': The command guest-fsfreeze-freeze has been disabled for this instance
> 
> virsh # domfsfreeze gentoo
> Froze 1 filesystem(s)

Heh, nice. I agree, we should not try to remember the state and just
send the command to qemu-ga.

ACK

Jirka