[libvirt] [PATCH 2/2] qemu: blockjob: Refuse to register blockjob if disk already has one

[Peter Krempa]

On Sat, Sep 14, 2019 at 21:04:28 -0500, Eric Blake wrote:
> On 9/14/19 3:44 AM, Peter Krempa wrote:
> > Most code paths prevent starting a blockjob if we already have one but
> > the job registering function does not do this check. While this isn't a
> > problem for regular cases we had a bad test case where we registered two
> > jobs for a single disk which leaked one of the jobs. Prevent this in the
> > registering function until we allow having multiple jobs per disk.
> > 
> > Signed-off-by: Peter Krempa <pkrempa at redhat.com>
> > ---
> >  src/qemu/qemu_blockjob.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/src/qemu/qemu_blockjob.c b/src/qemu/qemu_blockjob.c
> > index a991309ee7..80d0269128 100644
> > --- a/src/qemu/qemu_blockjob.c
> > +++ b/src/qemu/qemu_blockjob.c
> > @@ -143,6 +143,12 @@ qemuBlockJobRegister(qemuBlockJobDataPtr job,
> >  {
> >      qemuDomainObjPrivatePtr priv = vm->privateData;
> > 
> > +    if (disk && QEMU_DOMAIN_DISK_PRIVATE(disk)->blockjob) {
> > +        virReportError(VIR_ERR_INTERNAL_ERROR,
> > +                       _("disk '%s' has a blockjob assigned"), disk->dst);
> > +        return -1;
> > +    }
> > +
> 
> Can the user ever trigger this, in which case OPERATION_FAILED might be
> a nicer message?

All block job entrypoints should properly catch this error beforehand,
so this is a programmer error check.

Look for qemuDomainDiskBlockJobIsActive().
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