From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from [140.186.70.92] (port=57781 helo=eggs.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1Pb7qj-00026e-ND
	for qemu-devel@nongnu.org; Fri, 07 Jan 2011 03:39:06 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <hch@lst.de>) id 1Pb7qi-00045t-A7
	for qemu-devel@nongnu.org; Fri, 07 Jan 2011 03:39:05 -0500
Received: from verein.lst.de ([213.95.11.210]:51570)
	by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from <hch@lst.de>)
	id 1Pb7qh-00043L-UO
	for qemu-devel@nongnu.org; Fri, 07 Jan 2011 03:39:04 -0500
Date: Fri, 7 Jan 2011 09:38:55 +0100
From: Christoph Hellwig <hch@lst.de>
Subject: Re: [Qemu-devel] [PATCH 5/5] drive_open: Add invalidate option for
	block devices
Message-ID: <20110107083855.GA15053@lst.de>
References: <cover.1294150511.git.quintela@redhat.com>
	<95fe2a778152f50d942dcb17872927247195d0b1.1294150511.git.quintela@redhat.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <95fe2a778152f50d942dcb17872927247195d0b1.1294150511.git.quintela@redhat.com>
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.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: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Juan Quintela <quintela@redhat.com>
Cc: qemu-devel@nongnu.org

On Tue, Jan 04, 2011 at 03:33:30PM +0100, Juan Quintela wrote:
> Linux allows to invalidate block devices.  This is needed for the incoming
> migration part.

It's not.  The only thing that makes migration on block devices safe is
using O_DIRECT, aka cache=none.