[libvirt] [PATCH] qemu: Fix all callers of qemuMonitorGetBlockJobInfo()

[Andrea Bolognani]

On Mon, 2016-01-04 at 15:46 +0100, Michal Privoznik wrote:
> On 04.01.2016 15:20, Andrea Bolognani wrote:
> > Commit 1b43885 modified one of the callers of this function to take
> > into account the possible return value of 0 when the block job can't be
> > found.
> > 
> > This commit finishes the job by updating the remaining caller.
> > ---
> >  src/qemu/qemu_driver.c | 13 ++++++-------
> >  1 file changed, 6 insertions(+), 7 deletions(-)
> > 
> > diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> > index 304165c..c4573d9 100644
> > --- a/src/qemu/qemu_driver.c
> > +++ b/src/qemu/qemu_driver.c
> > @@ -16150,14 +16150,13 @@ qemuDomainBlockPivot(virQEMUDriverPtr driver,
> >          rc = qemuMonitorGetBlockJobInfo(priv->mon, disk->info.alias, &info);
> >          if (qemuDomainObjExitMonitor(driver, vm) < 0)
> >              goto cleanup;
> > -        if (rc < 0)
> > +        if (rc <= 0)
> >              goto cleanup;
> > -        if (rc == 1 &&
> > -            (info.ready == 1 ||
> > -             (info.ready == -1 &&
> > -              info.end == info.cur &&
> > -              (info.type == VIR_DOMAIN_BLOCK_JOB_TYPE_COPY ||
> > -               info.type == VIR_DOMAIN_BLOCK_JOB_TYPE_COMMIT))))
> > +        if (info.ready == 1 ||
> > +            (info.ready == -1 &&
> > +             info.end == info.cur &&
> > +             (info.type == VIR_DOMAIN_BLOCK_JOB_TYPE_COPY ||
> > +              info.type == VIR_DOMAIN_BLOCK_JOB_TYPE_COMMIT)))
> >              disk->mirrorState = VIR_DOMAIN_DISK_MIRROR_STATE_READY;
> >      }
> 
> Interesting. So previously this code worked just right with no block
> operation running on @disk. Now it will fail. I guess that's correct
> approach since this function's job is to abort a block job.
> 
> ACK

I'm actually having second thoughts about this.

We only call qemuMonitorGetBlockJobInfo() if !disk->mirrorState.
However, having it return 0 before would skip reading from info (my
main concern, as it would not have been filled in) and cause the
check for

  disk->mirrorState != VIR_DOMAIN_DISK_MIRROR_STATE_READY

immediately afterwards to fail and an error to be raised before
jumping to cleanup.

After my patch, the function will jump to cleanup earlier, still
returning a negative error code, but not raising any error in the
process.

I guess what I'm trying to say is that, unless you can convince
otherwise, I'm going to have to SNACK this one :)

Cheers.

-- 
Andrea Bolognani
Software Engineer - Virtualization Team