Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761392AbXE1Job (ORCPT ); Mon, 28 May 2007 05:44:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754232AbXE1JoT (ORCPT ); Mon, 28 May 2007 05:44:19 -0400 Received: from mx1.redhat.com ([66.187.233.31]:60005 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752976AbXE1JoR (ORCPT ); Mon, 28 May 2007 05:44:17 -0400 Date: Mon, 28 May 2007 10:43:58 +0100 From: Alasdair G Kergon To: device-mapper development , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, Jens Axboe , David Chinner , Phillip Susi , Stefan Bader , Andreas Dilger , Tejun Heo Subject: Re: [dm-devel] Re: [RFD] BIO_RW_BARRIER - what it means for devices, filesystems, and dm/md. Message-ID: <20070528094358.GM25091@agk.fab.redhat.com> Mail-Followup-To: device-mapper development , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, Jens Axboe , David Chinner , Phillip Susi , Stefan Bader , Andreas Dilger , Tejun Heo References: <18006.38689.818186.221707@notabene.brown> <18010.12472.209452.148229@notabene.brown> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <18010.12472.209452.148229@notabene.brown> 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 X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 924 Lines: 26 On Mon, May 28, 2007 at 11:30:32AM +1000, Neil Brown wrote: > 1/ A BIO_RW_BARRIER request should never fail with -EOPNOTSUP. The device-mapper position has always been that we require > a zero-length BIO_RW_BARRIER (i.e. containing no data to read or write - or emulated, possibly device-specific) before we can provide full barrier support. (Consider multiple active paths - each must see barrier.) Until every device supports barriers -EOPNOTSUP support is required. (Consider reconfiguration of stacks of devices - barrier support is a dynamic block device property that can switch between available and unavailable at any time.) 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/