Re: [Qemu-devel] [RFC PATCH 1/7] block/qdev: Allow node name for drive properties

[Eric Blake <eblake@redhat.com>]

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On 06/23/2016 08:36 AM, Kevin Wolf wrote:
> If a node name instead of a BlockBackend name is specified as the driver
> for a guest device, an anonymous BlockBackend is created now.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  hw/core/qdev-properties-system.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/core/qdev-properties-system.c b/hw/core/qdev-properties-system.c
> index df38b8a..c5cc9cf 100644
> --- a/hw/core/qdev-properties-system.c
> +++ b/hw/core/qdev-properties-system.c
> @@ -72,9 +72,18 @@ static void parse_drive(DeviceState *dev, const char *str, void **ptr,
>                          const char *propname, Error **errp)
>  {
>      BlockBackend *blk;
> +    bool blk_created = false;
>  
>      blk = blk_by_name(str);
>      if (!blk) {
> +        BlockDriverState *bs = bdrv_lookup_bs(NULL, str, NULL);

So BB name takes priority, but if one is not found, you try a BDS lookup
(node name) and create an anonymous BB to match.  Seems okay.

> +        if (bs) {
> +            blk = blk_new();
> +            blk_insert_bs(blk, bs);
> +            blk_created = true;
> +        }
> +    }
> +    if (!blk) {
>          error_setg(errp, "Property '%s.%s' can't find value '%s'",
>                     object_get_typename(OBJECT(dev)), propname, str);
>          return;

This return is safe, but looks a bit odd...

> @@ -91,9 +100,16 @@ static void parse_drive(DeviceState *dev, const char *str, void **ptr,
>              error_setg(errp, "Drive '%s' is already in use by another device",
>                         str);
>          }
> -        return;
> +        goto fail;

...given that you had to convert this return to a goto.

>      }
> +
>      *ptr = blk;
> +
> +fail:
> +    if (blk_created) {
> +        /* If we need to keep a reference, blk_attach_dev() took it */
> +        blk_unref(blk);
> +    }
>  }
>  
>  static void release_drive(Object *obj, const char *name, void *opaque)
> 

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


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