[libvirt] [PATCH] qemu: reject rather than hang on blockcommit of active layer

[Peter Krempa]

On 05/28/14 01:14, Eric Blake wrote:
> qemu 2.0 added the ability to commit the active layer, but slightly
> differently than what libvirt had been anticipating in its
> implementation of the virDomainBlockCommit call.  As a result, if
> you attempt to do a 'virsh blockcommit $dom vda', qemu gets into a
> state where it is waiting on libvirt to end the job, while libvirt
> is waiting on qemu to end the job, and the guest is effectively
> hung with regards to further commands for that block device.
> 
> I have patches coming down the pipeline that will add full support
> for blockcommit of the active layer when coupled with qemu 2.0 or
> later; but they depend on Peter's improvements to block job handling
> and form enough of a new feature that they are not ready for
> inclusion in the 1.2.5 release.  So for now, just reject the
> attempt, rather than letting the user get stuck.  This is no worse
> than the behavior of qemu 1.7 rejecting the job.
> 
> * src/qemu/qemu_driver.c (qemuDomainBlockCommit): Reject active
> commit.
> 
> Signed-off-by: Eric Blake <eblake at redhat.com>
> ---
> 
> This patch should be committed before the 1.2.5 release, while
> I continue to polish my full series for active commit support
> for inclusion after the release.

Agreed.

> 
>  src/qemu/qemu_driver.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 

ACK,

Peter


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