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Date: Fri, 3 Jan 2014 17:02:11 +0800
From: Stefan Hajnoczi <stefanha@gmail.com>
Message-ID: <20140103090211.GA1483@stefanha-thinkpad.redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v8 06/12] block: Add bdrv_set_backing_hd()
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To: Fam Zheng <famz@redhat.com>
Cc: kwolf@redhat.com, rjones@redhat.com, armbru@redhat.com, qemu-devel@nongnu.org, imain@redhat.com, stefanha@redhat.com, pbonzini@redhat.com

On Fri, Dec 13, 2013 at 03:35:14PM +0800, Fam Zheng wrote:
> +void bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd)
> +{
> +    if (bs->backing_hd) {
> +        bdrv_unref(bs->backing_hd);
> +    }
> +
> +    bs->backing_hd = backing_hd;
> +    if (!backing_hd) {
> +        return;
> +    }

Maybe we should also do:
bs->backing_file[0] = '\0';
bs->backing_format[0] = '\0';