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

On Wed, 15 Feb 2017 10:55:24 +0000 "Richard W.M. Jones" <rjones(a)redhat.com&gt; wrote: > 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(a)redhat.com&gt; 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. Ah, sorry. I didn't notice your JSON was bad from the start and I just blindly extended it. The correct JSON should look like this: json: { "file": { "driver":"raw", "file": { "driver":"file", "filename":"/var/tmp/backing.img" } } }