From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: [RFD] BIO_RW_BARRIER - what it means for devices, filesystems, and dm/md. Date: Thu, 31 May 2007 21:00:13 +0200 Message-ID: <20070531190013.GD32105@kernel.dk> References: <20070528024559.GA85884050@sgi.com> <465C871F.708@cfl.rr.com> <20070529234832.GT85884050@sgi.com> <20070530061723.GY85884050@sgi.com> <20070531002011.GC85884050@sgi.com> <20070531062644.GI32105@kernel.dk> <20070531070307.GK85884050@sgi.com> <465F1479.70100@cfl.rr.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <465F1479.70100@cfl.rr.com> Sender: linux-raid-owner@vger.kernel.org To: Phillip Susi Cc: David Chinner , david@lang.hm, Neil Brown , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, dm-devel@redhat.com, linux-raid@vger.kernel.org, Stefan Bader , Andreas Dilger , Tejun Heo List-Id: linux-raid.ids On Thu, May 31 2007, Phillip Susi wrote: > David Chinner wrote: > >That sounds like a good idea - we can leave the existing > >WRITE_BARRIER behaviour unchanged and introduce a new WRITE_ORDERED > >behaviour that only guarantees ordering. The filesystem can then > >choose which to use where appropriate.... > > So what if you want a synchronous write, but DON'T care about the order? > They need to be two completely different flags which you can choose > to combine, or use individually. If you have a use case for that, we can easily support it as well... Depending on the drive capabilities (FUA support or not), it may be nearly as slow as a "real" barrier write. -- Jens Axboe