[libvirt] [PATCH 2/2] util: storage: add JSON backing volume parser 'raw' block driver

[Richard W.M. Jones]

On Tue, Feb 14, 2017 at 10:03:54PM +0100, Tomáš Golembiovský wrote:
> Hi,
> 
> On Tue, 14 Feb 2017 15:58:45 +0000
> "Richard W.M. Jones" <rjones at redhat.com> wrote:
> 
> > The patches compile.
> > 
> > I looked at both commits and they at least superficially seem
> > sensible.  I'm not intimately familiar enough with the original code
> > to review this fully.
> > 
> > However I want to try to test this using libguestfs.  I believe the
> > following test case should be sufficient:
> > 
> >   $ cd /var/tmp
> >   $ truncate -s 1M backing.img
> >   $ qemu-img create \
> >       -b 'json:{"driver":"raw", "file":{"filename":"/var/tmp/backing.img"}}' \
> 
> The problem lies in the JSON here. Libvirt lacks the driver probing
> mechanism QEMU has (which makes sense). That means one has to be
> explicit about the drivers. Try with the following backing definition:
> 
> json:{"driver":"raw", "file":{ "driver":"file", "filename":"/var/tmp/backing.img"}}

OK, that works.  However it also works with the unpatched version of
libvirt, so it's not proof that these patches fix any problem.

Rich.

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