Re: [Qemu-devel] [PATCH 3/4] block: Allow JSON filenames

[Max Reitz]

On 06.05.2014 21:57, Eric Blake wrote:
> On 05/06/2014 01:30 PM, Max Reitz wrote:
> > If the filename given to bdrv_open() is prefixed with "json:", parse the
> > rest as a JSON object and use the result as the options QDict.
> >
> > Signed-off-by: Max Reitz <address@hidden>
> > ---
> >   block.c | 41 +++++++++++++++++++++++++++++++++++++++++
> >   1 file changed, 41 insertions(+)
> >
> >   /*
> >    * Opens a disk image (raw, qcow2, vmdk, ...)
> >    *
> > @@ -1337,6 +1364,20 @@ int bdrv_open(BlockDriverState **pbs, const char 
> > *filename,
> >           options = qdict_new();
> >       }
> >   
> > +    if (filename && g_str_has_prefix(filename, "json:")) {
> > +        QDict *json_options = parse_json_filename(filename, &local_err);
> > +        if (local_err) {
> > +            ret = -EINVAL;
> > +            goto fail;
> > +        }
> > +
> > +        qdict_join(options, json_options, true);
> > +        assert(qdict_size(json_options) == 0);
> Would it be better to pass false to qdict_join(), and then raise an
> error if the user specified conflicting options?  For example (untested,
> just typing off the top of my head here),
>
> -drive
> file='json:{"driver":"qcow2","file.filename":"foo","backing.file.driver":"raw"}',backing.file.driver=qcow2
>
> looks like it specifies conflicting backing.file.driver options.
> Passing true means that qdict_join silently overwrites the value in
> options to instead be the value in the json string; passing false means
> you could flag the user error.

Yes, you're right; I'll change it.

Max

> > +        QDECREF(json_options);
> > +
> > +        filename = NULL;
> > +    }
> > +
> >       bs->options = options;
> >       options = qdict_clone_shallow(options);