From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752836AbZHFMWa (ORCPT ); Thu, 6 Aug 2009 08:22:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751287AbZHFMW3 (ORCPT ); Thu, 6 Aug 2009 08:22:29 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:47963 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751251AbZHFMW3 (ORCPT ); Thu, 6 Aug 2009 08:22:29 -0400 Date: Thu, 6 Aug 2009 08:22:21 -0400 From: Christoph Hellwig To: Mark McLoughlin , device-mapper development , Jens Axboe , Rusty Russell , linux-kernel , virtualization , Mikulas Patocka Subject: Re: [dm-devel] [PATCH] block: silently error unsupported empty barriers too Message-ID: <20090806122221.GA5175@infradead.org> References: <1249557257.3721.55.camel@blaa> <20090806114550.GL29899@agk-dp.fab.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090806114550.GL29899@agk-dp.fab.redhat.com> User-Agent: Mutt/1.5.19 (2009-01-05) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 06, 2009 at 12:45:50PM +0100, Alasdair G Kergon wrote: > On Thu, Aug 06, 2009 at 12:14:17PM +0100, Mark McLoughlin wrote: > > We should error all barriers, even empty barriers, on devices like > > virtio_blk which don't support them. > > Have you considered whether or not virtio_blk actually needs to > support empty barriers? virtio_blk on kvm does not support any barriers at all, similar to many other drivers out there. If the queue flags say we don't support barriers higher layers should not submit any barrier requests.