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Date: Fri, 4 Jan 2013 18:25:12 +0100
From: Stefan Hajnoczi <stefanha@gmail.com>
Message-ID: <20130104172512.GA9339@stefanha-thinkpad.redhat.com>
References: <1357313548.13838.2.camel@oc2826874472.ibm.com>
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Subject: Re: [Qemu-devel] [PATCH] Fix : Enable qemu-img QED image commit
 support.
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To: Onkar N Mahajan <onmahaja@linux.vnet.ibm.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>, qemu-devel <qemu-devel@nongnu.org>, Anthony Liguori <aligouri@us.ibm.com>

On Fri, Jan 04, 2013 at 09:02:28PM +0530, Onkar N Mahajan wrote:
> @@ -695,7 +695,7 @@ static int coroutine_fn
> bdrv_qed_co_is_allocated(BlockDriverState *bs,
>  
>  static int bdrv_qed_make_empty(BlockDriverState *bs)
>  {
> -    return -ENOTSUP;
> +    return 0;
>  }

The only .bdrv_make_empty() caller is block.c:bdrv_commit():

    if (drv->bdrv_make_empty) {
        ret = drv->bdrv_make_empty(bs);
        bdrv_flush(bs);
    }

Perhaps it's best to drop bdrv_qed_make_empty() completely so
bdrv_commit() succeeds but we don't pretend to support
.bdrv_make_empty().

Stefan