From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [RFC] relaxed barrier semantics Date: Wed, 28 Jul 2010 11:17:06 +0200 Message-ID: <4C4FF592.9090800@kernel.org> References: <20100727165627.GA474@lst.de> <20100727175418.GF6820@quack.suse.cz> <20100727183546.GG7347@redhat.com> <4C4FE58C.8080403@kernel.org> <20100728082447.GA7668@lst.de> <4C4FECFE.9040509@kernel.org> <20100728085048.GA8884@lst.de> <4C4FF136.5000205@kernel.org> <20100728090025.GA9252@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Vivek Goyal , Jan Kara , jaxboe@fusionio.com, James.Bottomley@suse.de, linux-fsdevel@vger.kernel.org, linux-scsi@vger.kernel.org, tytso@mit.edu, chris.mason@oracle.com, swhiteho@redhat.com, konishi.ryusuke@lab.ntt.co.jp To: Christoph Hellwig Return-path: In-Reply-To: <20100728090025.GA9252@lst.de> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On 07/28/2010 11:00 AM, Christoph Hellwig wrote: > On Wed, Jul 28, 2010 at 10:58:30AM +0200, Tejun Heo wrote: >> I see. It probably would be good to have ordering requirements >> carried in the bio / request, so that filesystems can mix and match >> barriers of different strengths as necesasry. As you seem to be >> already working on it, are you interested in pursuing that direction? > > I've been working on that for a while, but it got a lot more urgent > as there's been an application hit particularly hard by the barrier > semantics on cache less devices and people started getting angry > about it. That's why fixing this for cache less devices has become > a higher priority than solving the big picture. Well, if disabling barrier works around the problem for them (which is basically what was suggeseted in the first message), that's not too bad for short term, I think. At least, there's a handy workaround. I'll re-read barrier code and see how hard it would be to implement a proper solution. Thanks. -- tejun