From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCHSET block#for-2.6.36-post] block: replace barrier with sequenced flush Date: Wed, 18 Aug 2010 10:11:22 +0200 Message-ID: <4C6B95AA.7040502@suse.de> References: <1281616891-5691-1-git-send-email-tj@kernel.org> <20100813114858.GA31937@lst.de> <4C654D4B.1030507@kernel.org> <20100813143820.GA7931@lst.de> <4C655BE5.4070809@kernel.org> <20100814103654.GA13292@lst.de> <4C6A5D8A.4010205@kernel.org> <20100817131915.GB2963@lst.de> <4C6ABBCB.9030306@kernel.org> <20100817165929.GB13800@lst.de> <4C6B7F4A.2040807@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4C6B7F4A.2040807@kernel.org> Sender: linux-fsdevel-owner@vger.kernel.org To: Christoph Hellwig Cc: jaxboe@fusionio.com, linux-fsdevel@vger.kernel.org, linux-scsi@vger.kernel.org, linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, James.Bottomley@suse.de, tytso@mit.edu, chris.mason@oracle.com, swhiteho@redhat.com, konishi.ryusuke@lab.ntt.co.jp, dm-devel@redhat.com, vst@vlnb.net, jack@suse.cz, rwheeler@redhat.com, hare@suse.de List-Id: linux-raid.ids Hello, On 08/18/2010 08:35 AM, Tejun Heo wrote: >> It's not bisecting to find bugs in the barrier conversion. We can't >> easily bisect it down anyway. The problem is when we try to bisect >> other problems and get into the middle of the series barriers suddenly >> are gone. Which is not very helpful for things like data integrity >> problems in filesystems. > > Ah, okay, hmmm.... alright, I'll resequence the patches. If the > filesystem changes can be put into a single tree somehow, we can keep > things mostly working at least for direct devices. Sorry but I'm doing it. It just doesn't make much sense. I can't relax the ordering for REQ_HARDBARRIER without breaking the remapping drivers. So, to keep things working, I'll have to 1. relax the ordering 2. implement new REQ_FLUSH/FUA based interface and 3. use them in the filesystems in the same patch. That's just wrong. And I don't think md/dm changes can or should go through the block tree. They're way too invasive for that. It's a new implementation and barrier won't work (fail gracefully) for several commits during the transition. I don't think there's a better way around it. Thanks. -- tejun