From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43)
	id 1LKcIK-0007C7-4b
	for qemu-devel@nongnu.org; Wed, 07 Jan 2009 12:34:16 -0500
Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43)
	id 1LKcII-00079f-Cs
	for qemu-devel@nongnu.org; Wed, 07 Jan 2009 12:34:15 -0500
Received: from [199.232.76.173] (port=39821 helo=monty-python.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1LKcII-00079D-7l
	for qemu-devel@nongnu.org; Wed, 07 Jan 2009 12:34:14 -0500
Received: from qw-out-1920.google.com ([74.125.92.147]:23606)
	by monty-python.gnu.org with esmtp (Exim 4.60)
	(envelope-from <anthony@codemonkey.ws>) id 1LKcIH-00049m-OT
	for qemu-devel@nongnu.org; Wed, 07 Jan 2009 12:34:13 -0500
Received: by qw-out-1920.google.com with SMTP id 5so3865817qwc.4
	for <qemu-devel@nongnu.org>; Wed, 07 Jan 2009 09:34:13 -0800 (PST)
Message-ID: <4964E78F.1010206@codemonkey.ws>
Date: Wed, 07 Jan 2009 11:34:07 -0600
From: Anthony Liguori <anthony@codemonkey.ws>
MIME-Version: 1.0
References: <4964E38A.5050204@suse.de>
In-Reply-To: <4964E38A.5050204@suse.de>
Content-Type: text/plain; charset=ISO-8859-15; format=flowed
Content-Transfer-Encoding: 7bit
Subject: [Qemu-devel] Re: [PATCH][RESEND] qcow2: Fix cluster allocation
Reply-To: qemu-devel@nongnu.org
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.gnu.org/pipermail/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Kevin Wolf <kwolf@suse.de>
Cc: qemu-devel@nongnu.org

Kevin Wolf wrote:
> When allocating multiple clusters at once, the qcow2 implementation
> tries to find as many physically contiguous clusters as possible to
> allow larger writes. This search includes allocated clusters which are
> in the right place and still free clusters. If the range to allocate
> spans clusters in patterns like "10 allocated, then 10 free, then again
> 10 allocated" it is only checked that the chunks of allocated clusters
> are contiguous for themselves.
>
> However, what is actually needed is to have _all_ allocated clusters
> contiguous, starting at the first cluster of the allocation and spanning
> multiple such chunks. This patch changes the check so that each offset
> is not compared to the offset of the first cluster in its own chunk but
> to the first cluster in the whole allocation.
>
> I haven't seen it happen, but without this fix data corruption on qcow2
> images is possible.
>
> Signed-off-by: Kevin Wolf <kwolf@suse.de>
> Acked-by: Gleb Natapov <gleb@redhat.com>
>   

Applied.  Thanks.

Regards,

Anthony Liguori