From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754908Ab0FPB4g (ORCPT ); Tue, 15 Jun 2010 21:56:36 -0400 Received: from ozlabs.org ([203.10.76.45]:53615 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754582Ab0FPB4f (ORCPT ); Tue, 15 Jun 2010 21:56:35 -0400 From: Rusty Russell To: Christoph Hellwig Subject: Re: [PATCH] virtio_blk: support barriers without FLUSH feature Date: Wed, 16 Jun 2010 11:26:32 +0930 User-Agent: KMail/1.13.2 (Linux/2.6.32-22-generic; KDE/4.4.2; i686; ; ) Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org References: <20100615124348.GA25804@lst.de> In-Reply-To: <20100615124348.GA25804@lst.de> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201006161126.32894.rusty@rustcorp.com.au> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 15 Jun 2010 10:13:48 pm Christoph Hellwig wrote: > If we want to support barriers with the cache=writethrough mode in qemu > we need to tell the block layer that we only need queue drains to > implement a barrier. Follow the model set by SCSI and IDE and assume > that there is no volatile write cache if the host doesn't advertize it. > While this might imply working barriers on old qemu versions or other > hypervisors that actually have a volatile write cache this is only a > cosmetic issue - these hypervisors don't guarantee any data integrity > with or without this patch, but with the patch we at least provide > data ordering. > > Signed-off-by: Christoph Hellwig Thanks, applied. Cheers, Rusty.