Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932959AbZDIK3i (ORCPT ); Thu, 9 Apr 2009 06:29:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933561AbZDIK27 (ORCPT ); Thu, 9 Apr 2009 06:28:59 -0400 Received: from mx2.redhat.com ([66.187.237.31]:43730 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933591AbZDIK26 (ORCPT ); Thu, 9 Apr 2009 06:28:58 -0400 Date: Thu, 9 Apr 2009 11:28:51 +0100 From: Alasdair G Kergon To: Chris Mason Cc: Mikulas Patocka , device-mapper development , ak@linux.intel.com, Linux Kernel Mailing List , Jens Axboe Subject: Re: [dm-devel] Barriers still not passing on simple dm devices... Message-ID: <20090409102851.GT5688@agk.fab.redhat.com> Mail-Followup-To: Chris Mason , Mikulas Patocka , device-mapper development , ak@linux.intel.com, Linux Kernel Mailing List , Jens Axboe References: <20090325152751.GV27476@kernel.dk> <20090326084205.GG27476@kernel.dk> <20090331104933.GJ5178@kernel.dk> <20090403081131.GP5178@kernel.dk> <1239240440.11220.3.camel@think.oraclecorp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1239240440.11220.3.camel@think.oraclecorp.com> User-Agent: Mutt/1.4.1i Organization: Red Hat UK Ltd. Registered in England and Wales, number 03798903. Registered Office: Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE. Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 820 Lines: 18 On Wed, Apr 08, 2009 at 09:27:20PM -0400, Chris Mason wrote: > I'm afraid expecting barriers forever in the future isn't completely > compatible with dm or md. Both of these allow the storage to change > over time, and the filesystem needs to handle this without corruptions. The missing piece of the jigsaw is notification to upper layers *ahead* of such reconfigurations. (We have similar notification issues when devices are resized - the current approach is to leave the sysadmin responsible for co-ordinating changes through userspace.) Alasdair -- agk@redhat.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/