Re: [Qemu-devel] [RFC PATCH 05/10] qcow2: Use BlockdevRef in qcow2_create2()

[Max Reitz <mreitz@redhat.com>]

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On 2018-01-11 20:52, Kevin Wolf wrote:
> Instead of passing a separate BlockDriverState* into qcow2_create2(),
> make use of the BlockdevRef that is included in BlockdevCreateOptions.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  include/block/block.h |  1 +
>  block.c               | 39 +++++++++++++++++++++++++++++++++++++++
>  block/qcow2.c         | 33 +++++++++++++++++++++------------
>  3 files changed, 61 insertions(+), 12 deletions(-)

[...]

> diff --git a/block.c b/block.c
> index a8da4f2b25..c9b0e1d6d3 100644
> --- a/block.c
> +++ b/block.c

[...]

> @@ -2405,6 +2407,43 @@ BdrvChild *bdrv_open_child(const char *filename,
>      return c;
>  }
>  
> +/* TODO Future callers may need to specify parent/child_role in order for
> + * option inheritance to work. Existing callers use it for the root node. */
> +BlockDriverState *bdrv_open_blockdev_ref(BlockdevRef *ref, Error **errp)
> +{
> +    BlockDriverState *bs = NULL;
> +    Error *local_err = NULL;
> +    QObject *obj = NULL;
> +    QDict *qdict = NULL;
> +    const char *reference = NULL;
> +    Visitor *v = NULL;
> +
> +    if (ref->type == QTYPE_QSTRING) {
> +        reference = ref->u.reference;
> +    } else {
> +        BlockdevOptions *options = &ref->u.definition;
> +        assert(ref->type == QTYPE_QDICT);
> +
> +        v = qobject_output_visitor_new(&obj);
> +        visit_type_BlockdevOptions(v, NULL, &options, &local_err);
> +        if (local_err) {
> +            error_propagate(errp, local_err);
> +            goto fail;
> +        }
> +        visit_complete(v, &obj);
> +
> +        qdict = qobject_to_qdict(obj);
> +        qdict_flatten(qdict);
> +    }
> +
> +    bs = bdrv_open_inherit(NULL, reference, qdict, 0, NULL, NULL, errp);
> +
> +fail:
> +    qobject_decref(obj);

I'd prefer QDECREF(qdict), myself, although I can't quite explain why.
Probably because @qdict is the object you're actually using and @obj is
just some temporary designation.

Also, doesn't bdrv_open_inherit() take ownership of @qdict and thus @obj?

Max

> +    visit_free(v);
> +    return bs;
> +}
> +
>  static BlockDriverState *bdrv_append_temp_snapshot(BlockDriverState *bs,
>                                                     int flags,
>                                                     QDict *snapshot_options,


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