From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([140.186.70.92]:40653)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <kwolf@redhat.com>) id 1Ra2S8-0006IP-15
	for qemu-devel@nongnu.org; Mon, 12 Dec 2011 04:45:48 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <kwolf@redhat.com>) id 1Ra2S5-0002V0-S8
	for qemu-devel@nongnu.org; Mon, 12 Dec 2011 04:45:43 -0500
Received: from mx1.redhat.com ([209.132.183.28]:14846)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <kwolf@redhat.com>) id 1Ra2S5-0002Uq-LP
	for qemu-devel@nongnu.org; Mon, 12 Dec 2011 04:45:41 -0500
Message-ID: <4EE5CDFB.1080809@redhat.com>
Date: Mon, 12 Dec 2011 10:48:43 +0100
From: Kevin Wolf <kwolf@redhat.com>
MIME-Version: 1.0
References: <958CDBC95A3252B592B5E3C9@nimrod.local>
	<4EE0B059.4010903@redhat.com>
	<98D05E44527FF395E0A60016@nimrod.local>
In-Reply-To: <98D05E44527FF395E0A60016@nimrod.local>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] RFC: raw device support for block device targets
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Alex Bligh <alex@alex.org.uk>
Cc: qemu-devel@nongnu.org

Am 11.12.2011 11:45, schrieb Alex Bligh:
> 
> 
> --On 8 December 2011 13:40:57 +0100 Kevin Wolf <kwolf@redhat.com> wrote:
> 
>>> qemu-img convert appears to support block devices as input, but not
>>> as output. That is irritating, as when using qemu-img convert to
>>> convert qcow to raw on a block partition, an intermediate file has
>>> to be used, which slows things down and pointlessly uses disk space.
>>>
>>> The problem is that ftruncate() is being called on the output file
>>> in order ensure it is sufficiently large, and this fails on
>>> block devices.
> ...
>>
>> Creating an image on a block device shouldn't even call raw_create(),
>> but only hdev_create(), which doesn't try to truncate the device, but
>> just uses lseek to make sure that it's large enough.
>>
>> Which qemu version are you using and what's your command line?
> 
> I was testing on:
> 
> amb@alex-test:~$ qemu-img --version
> qemu-img version 0.12.3, Copyright (c) 2004-2008 Fabrice Bellard

That's the problem. It should work since 0.13.

Kevin