From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43)
	id 1MxLZd-0007Dp-QH
	for qemu-devel@nongnu.org; Mon, 12 Oct 2009 10:08:29 -0400
Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43)
	id 1MxLZY-0007BW-RI
	for qemu-devel@nongnu.org; Mon, 12 Oct 2009 10:08:29 -0400
Received: from [199.232.76.173] (port=46380 helo=monty-python.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1MxLZY-0007BT-Mv
	for qemu-devel@nongnu.org; Mon, 12 Oct 2009 10:08:24 -0400
Received: from mx1.redhat.com ([209.132.183.28]:28099)
	by monty-python.gnu.org with esmtp (Exim 4.60)
	(envelope-from <kwolf@redhat.com>) id 1MxLZY-0003nX-1O
	for qemu-devel@nongnu.org; Mon, 12 Oct 2009 10:08:24 -0400
Message-ID: <4AD33813.6090006@redhat.com>
Date: Mon, 12 Oct 2009 16:07:15 +0200
From: Kevin Wolf <kwolf@redhat.com>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] [PATCH] Add readonly flag to -drive command
References: <4AD32550.8040901@redhat.com> <4AD32DF6.4050100@redhat.com>
	<20091012135032.GA13560@shareable.org>
In-Reply-To: <20091012135032.GA13560@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: Naphtali Sprei <nsprei@redhat.com>, qemu-devel@nongnu.org

Am 12.10.2009 15:50, schrieb Jamie Lokier:
> Right now there is already a 'readonly' flag called 'chmod -r image',
> because QEMU opens a file read-only if it can't open it writable, so
> it's not a new case.  Just moving it from the filesystem into QEMU.

Right, but I'm not sure how well it is tested. I think, when moving it
into qemu we should take the opportunity to do it right. If everything
works right now, the right description of it is probably "pure luck".
And I assume you didn't do stupid things like savevm on a read-only
image which we still should be able to handle.

> When opened read-only, it would be better for the block drivers to
> return an error themselves, instead of trying to write and (hopefully)
> getting a host OS error.

For simple read/write operations, the generic block layer is doing the
check already.

Kevin