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Date: Fri, 20 Mar 2015 09:03:04 +0100
From: Alberto Garcia <berto@igalia.com>
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Subject: Re: [Qemu-devel] [PATCH 1/3] block: add
 bdrv_get_device_or_node_name()
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To: Markus Armbruster <armbru@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>

On Fri, Mar 20, 2015 at 08:40:32AM +0100, Markus Armbruster wrote:

> > +const char *bdrv_get_device_or_node_name(const BlockDriverState *bs)
> > +{
> > +    return bs->blk ? blk_name(bs->blk) : bs->node_name;
> > +}
> > +
> 
> Does this have uses beyond identifying @bs to the user?

None that I can think of, although apart from error messages it can
also be used in data types, like the cases of BLOCK_IMAGE_CORRUPTED
and BlockJobInfo that are being discussed:

   https://lists.gnu.org/archive/html/qemu-devel/2015-03/msg03651.html

> >  static void quorum_report_failure(QuorumAIOCB *acb)
> >  {
> > -    const char *reference = bdrv_get_device_name(acb->common.bs)[0] ?
> > -                            bdrv_get_device_name(acb->common.bs) :
> > -                            acb->common.bs->node_name;
> > -
> > +    const char *reference = bdrv_get_device_or_node_name(acb->common.bs);
> >      qapi_event_send_quorum_failure(reference, acb->sector_num,
> >                                     acb->nb_sectors, &error_abort);
> >  }
> 
> Preexisting: what if reference is null?

It can't happen, both the device and the node name strings are
guaranteed to be non-null. The latter is actually a static string so
there's no chance bs->node_name returns a null pointer.

Berto