Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755962AbYLELyP (ORCPT ); Fri, 5 Dec 2008 06:54:15 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750895AbYLELyA (ORCPT ); Fri, 5 Dec 2008 06:54:00 -0500 Received: from earthlight.etchedpixels.co.uk ([81.2.110.250]:54934 "EHLO lxorguk.ukuu.org.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750773AbYLELx7 (ORCPT ); Fri, 5 Dec 2008 06:53:59 -0500 Date: Fri, 5 Dec 2008 11:52:25 +0000 From: Alan Cox To: Andi Kleen Cc: Mikulas Patocka , Andi Kleen , linux-kernel@vger.kernel.org, xfs@oss.sgi.com, Alasdair G Kergon , Andi Kleen , Milan Broz Subject: Re: Device loses barrier support (was: Fixed patch for simple barriers.) Message-ID: <20081205115225.13c277ee@lxorguk.ukuu.org.uk> In-Reply-To: <20081205013739.GZ6703@one.firstfloor.org> References: <20081204142015.GQ6703@one.firstfloor.org> <20081204145810.GR6703@one.firstfloor.org> <20081204174838.GS6703@one.firstfloor.org> <20081204221551.GV6703@one.firstfloor.org> <20081205004849.GX6703@one.firstfloor.org> <20081205013739.GZ6703@one.firstfloor.org> X-Mailer: Claws Mail 3.5.0 (GTK+ 2.12.12; x86_64-redhat-linux-gnu) Organization: Red Hat UK Cyf., Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE, Y Deyrnas Gyfunol. Cofrestrwyd yng Nghymru a Lloegr o'r rhif cofrestru 3798903 Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1003 Lines: 24 On Fri, 5 Dec 2008 02:37:39 +0100 Andi Kleen wrote: > > * barrier support in md-raid1 deviates from the specification at > > Documentation/block/barrier.txt. The specification says that requests > > submitted after the barrier request hit the media after the barrier > > request hits the media. The reality is that the barrier request can be > > randomly aborted and the requests submitted after it hit the media before > > the barrier request. > > Yes the spec should be probably updated. > > But also see Linus' rant from yesterday about code vs documentation. > When in doubt the code wins. Not when the fundamental design of the code is broken and trashes performance. The documented behaviour is strongly desirable. Alan -- 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/