Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754507AbZIJHsT (ORCPT ); Thu, 10 Sep 2009 03:48:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753926AbZIJHsS (ORCPT ); Thu, 10 Sep 2009 03:48:18 -0400 Received: from brick.kernel.dk ([93.163.65.50]:46906 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751634AbZIJHsS (ORCPT ); Thu, 10 Sep 2009 03:48:18 -0400 Date: Thu, 10 Sep 2009 09:48:20 +0200 From: Jens Axboe To: Ed Cashin Cc: alan@lxorguk.ukuu.org.uk, akpm@linux-foundation.org, apw@canonical.com, bonbons@linux-vserver.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] aoe: end barrier bios with EOPNOTSUPP Message-ID: <20090910074820.GS18599@kernel.dk> References: <20090904183525.GB18599@kernel.dk> <20090905051735.GH18599@kernel.dk> <366469f19c41e0150028b886f6859019@coraid.com> <20090908193540.GB18599@kernel.dk> <60772f633c524ba873f569966fccd6ce@coraid.com> <20090909180804.3e62331a@lxorguk.ukuu.org.uk> <30b7855d211ab5b6bef6fe2cd9b76295@coraid.com> <20090909205835.GK18599@kernel.dk> <810bbe1723b0a205f9b5018a5ddaa722@coraid.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <810bbe1723b0a205f9b5018a5ddaa722@coraid.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1614 Lines: 36 On Wed, Sep 09 2009, Ed Cashin wrote: > On Wed Sep 9 16:59:30 EDT 2009, jens.axboe@oracle.com wrote: > > On Wed, Sep 09 2009, Ed Cashin wrote: > ... > > > To implement the barrier, [aoe] would stop generating new AoE write > > > commands, wait for AoE write responses for all the outstanding write > > > commands, issue the ATA cache flush command, wait for the response to > > > the flush, and then resume normal activity. > > > > That's how barriers work with sata to begin with, so I'd very much > > recommend that you do the same in aoe instead of just not supporting it. > > This patch with EOPNOTSUPP just fixes the regression in 2.6.31-rc9. > > A patch adding support for barriers would be nice. Since I have > limited time I tried to motivate that work by using the torture tests > that Chris Mason (I believe it was) posted a while ago, but I could > not get any problems to manifest using that torture test. > > If I had a reproducable problem case that the barrier implementation > could fix, it would be very helpful. Depending on timing and the other end, it may not be easy to reproduce. But the problem is indeed real, so I think you should just add the proper barrier implementation instead of spending too much time trying to create a reproducable problem. By the time you get there, you could have fixed it many times over :-) -- Jens Axboe -- 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/