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Date: Mon, 14 Sep 2015 10:45:55 +0200
From: Kevin Wolf <kwolf@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v3 2/4] block: Add 'ignore-backing' field
 to BlockdevOptionsGenericCOWFormat
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To: Alberto Garcia <berto@igalia.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>, qemu-devel@nongnu.org, qemu-block@nongnu.org, Max Reitz <mreitz@redhat.com>

Am 14.09.2015 um 07:54 hat Alberto Garcia geschrieben:
> On Fri 11 Sep 2015 07:33:41 PM CEST, Max Reitz <mreitz@redhat.com> wrote:
> 
> >>> So why do we need the new flag? Because "backing: ''" is ugly?
> >> 
> >> I guess it's just because you're the only one who actually reads the
> >> documentation. When discussing this, I didn't remember that we
> >> already had a way to express this (an additional bool wouldn't have
> >> been my favourite solution anyway). Thanks for catching this.
> >
> > I read the patch, it was part of the context. ;-)
> 
> Oh, that was embarrassing :-) Yes, it was the discussion from two weeks
> ago about passing empty strings as BlockdevRef that made me think that
> this would be ugly.
> 
> Anyway, was this ever implemented? It seems that passing a string to the
> 'backing' parameter is only specified in the JSON schema, but no one
> actually uses that.
> 
> So I'll implement that for the next version of my series.

I have a patch that actually allows passing a node-name reference as a
string here. v1 was posted a few months ago; it just turned out that I
need to kill bdrv_swap() before that can work because bdrv_swap()
doesn't work with nodes that have a BlockBackend attached.

Of course, I didn't check what an empty string would do with my patch...

Kevin