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

[Eric Blake <eblake@redhat.com>]

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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 <mreitz@redhat.com>
> ---
>  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.

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

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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