Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753502AbXE3Ize (ORCPT ); Wed, 30 May 2007 04:55:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751387AbXE3IzR (ORCPT ); Wed, 30 May 2007 04:55:17 -0400 Received: from ug-out-1314.google.com ([66.249.92.169]:31616 "EHLO ug-out-1314.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751425AbXE3IzP (ORCPT ); Wed, 30 May 2007 04:55:15 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=beta; h=received:message-id:date:from:sender:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references:x-google-sender-auth; b=GYiCEHQH1H6zxvawzvmFnZy/E1WQUks0gLoy58FKTnf/x/ABhYSNeDwPd+7xHHCCBqWHIk1lRce1yZ/SysQ/e6k0XMzd3cCouJiybaCm5wBYDtx60ejMRV/Wnnbj860fg/sRFv6FV68GGOh7fMuhxkKhDNI1OGbImpxZ11vq9kA= Message-ID: <5201e28f0705300155ue7ce985m3f318ff7ff1a1396@mail.gmail.com> Date: Wed, 30 May 2007 10:55:13 +0200 From: "Stefan Bader" To: "David Chinner" Subject: Re: [RFD] BIO_RW_BARRIER - what it means for devices, filesystems, and dm/md. Cc: david@lang.hm, "Phillip Susi" , "Neil Brown" , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, dm-devel@redhat.com, linux-raid@vger.kernel.org, "Jens Axboe" , "Andreas Dilger" , "Tejun Heo" In-Reply-To: <20070530061723.GY85884050@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <18006.38689.818186.221707@notabene.brown> <18010.12472.209452.148229@notabene.brown> <20070528024559.GA85884050@sgi.com> <465C871F.708@cfl.rr.com> <20070529234832.GT85884050@sgi.com> <20070530061723.GY85884050@sgi.com> X-Google-Sender-Auth: 940b2ce0dd5d7d96 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1133 Lines: 30 > The order that these are expected by the filesystem to hit stable > storage are: > > 1. block 4 and 10 on stable storage in any order > 2. barrier block X on stable storage > 3. block 5 and 20 on stable storage in any order > > The point I'm trying to make is that in XFS, block 5 and 20 cannot > be allowed to hit the disk before the barrier block because they > have strict order dependency on block X being stable before them, > just like block X has strict order dependency that block 4 and 10 > must be stable before we start the barrier block write. > That would be the exactly how I understand Documentation/block/barrier.txt: "In other words, I/O barrier requests have the following two properties. 1. Request ordering ... 2. Forced flushing to physical medium" "So, I/O barriers need to guarantee that requests actually get written to non-volatile medium in order." Stefan - 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/