From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43)
	id 1McwT7-00057i-9e
	for qemu-devel@nongnu.org; Mon, 17 Aug 2009 03:17:25 -0400
Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43)
	id 1McwT2-00057W-OL
	for qemu-devel@nongnu.org; Mon, 17 Aug 2009 03:17:25 -0400
Received: from [199.232.76.173] (port=51723 helo=monty-python.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1McwT2-00057T-K9
	for qemu-devel@nongnu.org; Mon, 17 Aug 2009 03:17:20 -0400
Received: from mx20.gnu.org ([199.232.41.8]:40798)
	by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32)
	(Exim 4.60) (envelope-from <kwolf@redhat.com>) id 1McwT2-0004qz-1F
	for qemu-devel@nongnu.org; Mon, 17 Aug 2009 03:17:20 -0400
Received: from mx2.redhat.com ([66.187.237.31])
	by mx20.gnu.org with esmtp (Exim 4.60)
	(envelope-from <kwolf@redhat.com>) id 1McwT1-0000tC-9D
	for qemu-devel@nongnu.org; Mon, 17 Aug 2009 03:17:19 -0400
Message-ID: <4A8903B9.3010109@redhat.com>
Date: Mon, 17 Aug 2009 09:16:09 +0200
From: Kevin Wolf <kwolf@redhat.com>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] [PATCH] qcow2: Metadata preallocation
References: <1250262015-996-1-git-send-email-kwolf@redhat.com>
	<4A87F44B.5080308@redhat.com>
	<5b31733c0908160512r25abf0d2ld45a3602a8c540fa@mail.gmail.com>
	<20090816164841.GA27122@shareable.org>
In-Reply-To: <20090816164841.GA27122@shareable.org>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
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: Jamie Lokier <jamie@shareable.org>
Cc: Filip Navara <filip.navara@gmail.com>, Avi Kivity <avi@redhat.com>, qemu-devel@nongnu.org

Jamie Lokier schrieb:
> Filip Navara wrote:
>> FILE_ATTRIBUTE_SPARSE_FILE? You can't actually set it when
>> opening/creating the file, a separate call to
>> DeviceIoControl/FSCTL_SET_SPARSE is needed.
> 
> I see that you increase the file size by writing zeros to the end.
> 
> Can't you use the Windows equivalent of unix ftruncate() to extend the
> file instead, after FSCTL_SET_SPARSE?

There actually exists a bdrv_truncate(). I wasn't aware of that. If you
prefer, I can resend the patch with bdrv_truncate instead of a zero write.

Kevin