From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43)
	id 1Mlf15-0000k4-5c
	for qemu-devel@nongnu.org; Thu, 10 Sep 2009 04:28:31 -0400
Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43)
	id 1Mlf10-0000je-Gy
	for qemu-devel@nongnu.org; Thu, 10 Sep 2009 04:28:30 -0400
Received: from [199.232.76.173] (port=41045 helo=monty-python.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1Mlf10-0000jb-Aw
	for qemu-devel@nongnu.org; Thu, 10 Sep 2009 04:28:26 -0400
Received: from mx1.redhat.com ([209.132.183.28]:45158)
	by monty-python.gnu.org with esmtp (Exim 4.60)
	(envelope-from <kwolf@redhat.com>) id 1Mlf0z-0002Sa-Nm
	for qemu-devel@nongnu.org; Thu, 10 Sep 2009 04:28:26 -0400
Message-ID: <4AA8B865.8000809@redhat.com>
Date: Thu, 10 Sep 2009 10:27:17 +0200
From: Kevin Wolf <kwolf@redhat.com>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] More qcow2 bugs? - qemu-img convert/commit
References: <20090909232654.GA20719@shareable.org>
In-Reply-To: <20090909232654.GA20719@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: qemu-devel@nongnu.org

Am 10.09.2009 01:26, schrieb Jamie Lokier:
> 37% is large enough to be a clue: Does it simply expand the qcow2 file
> without reading the backing file at all?  A quick strace shows that
> indeed, it does *open* the backing file and it does read the backing
> file's header, but after that it doesn't read it at all.
> 
> Did I miss something obvious which means this is ok?

No, this definitely looks like a bug. I tend to suspect qemu-img rather
than qcow2, though. After all, your qcow2 image works when a VM reads it
and from a qcow2 perspective there should be no difference from reading
in qemu-img.

I'll have a look at it.

> Should the output of "qemu-img convert" be identical to the backing
> file after "qemu-img commit", assuming they are the same format?

No, same format isn't enough. Assuming they are both raw images (as in
your case), I would agree, though.

Kevin