From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [RFC] relaxed barrier semantics Date: Fri, 30 Jul 2010 15:09:57 +0200 Message-ID: <20100730130957.GA26894@lst.de> References: <20100728090025.GA9252@lst.de> <4C4FF592.9090800@kernel.org> <20100728092859.GA11096@lst.de> <20100729014431.GD4506@thunk.org> <4C51DA1F.2040701@redhat.com> <20100729194904.GA17098@lst.de> <4C51DCF1.3010507@redhat.com> <25F5E16E-968D-4FEF-8187-70453985B19B@dilger.ca> <20100729230406.GI4506@thunk.org> <4C52CBFF.6090406@vlnb.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "Ted Ts'o" , Andreas Dilger , Ric Wheeler , Christoph Hellwig , Tejun Heo , Vivek Goyal , Jan Kara , jaxboe@fusionio.com, James.Bottomley@suse.de, linux-fsdevel@vger.kernel.org, linux-scsi@vger.kernel.org, chris.mason@oracle.com, swhiteho@redhat.com, konishi.ryusuke@lab.ntt.co.jp To: Vladislav Bolkhovitin Return-path: Received: from verein.lst.de ([213.95.11.210]:40063 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756650Ab0G3NKa (ORCPT ); Fri, 30 Jul 2010 09:10:30 -0400 Content-Disposition: inline In-Reply-To: <4C52CBFF.6090406@vlnb.net> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Fri, Jul 30, 2010 at 04:56:31PM +0400, Vladislav Bolkhovitin wrote: > For a simpler device (a disk without support for ORDERED queuing) the > same meta-data updates would be: > > 1. 1st journal write command > > 2. 2d journal write command > > 3. 3d journal write command > > 4. The queue draining. Which is complete overkill. We have state machines for everything we do block I/O on (both data and the journal), which allows us to just wait on the I/O requests we need inside the filesystem instead of draining the queue, or enforce global ordering using ordered tags.