From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH, RFC 2/2] dm: support REQ_FLUSH directly Date: Mon, 30 Aug 2010 10:33:12 +0200 Message-ID: <4C7B6CC8.5080609@kernel.org> References: <20100727175418.GF6820@quack.suse.cz> <20100803184939.GA12198@lst.de> <20100803185148.GA12258@lst.de> <4C58F341.9060605@ct.jp.nec.com> <20100804085423.GA15687@lst.de> <4C5A1F05.40308@ce.jp.nec.com> <20100826225024.GB17832@redhat.com> <4C771852.3050500@ce.jp.nec.com> <20100827040808.GA19488@redhat.com> <4C7752B5.3020905@ce.jp.nec.com> <20100827141314.GB22504@redhat.com> <4C7B3760.2070201@ce.jp.nec.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4C7B3760.2070201@ce.jp.nec.com> Sender: linux-fsdevel-owner@vger.kernel.org To: Jun'ichi Nomura Cc: Mike Snitzer , Christoph Hellwig , Kiyoshi Ueda , Jan Kara , linux-scsi@vger.kernel.org, jaxboe@fusionio.com, linux-raid@vger.kernel.org, linux-fsdevel@vger.kernel.org, James.Bottomley@suse.de, konishi.ryusuke@lab.ntt.co.jp, tytso@mit.edu, swhiteho@redhat.com, chris.mason@oracle.com, dm-devel@redhat.com List-Id: linux-raid.ids On 08/30/2010 06:45 AM, Jun'ichi Nomura wrote: > Hi Mike, > > (08/27/10 23:13), Mike Snitzer wrote: >>> If there will be no need for supporting a request-based target >>> with num_flush_requests > 1, the special handling of flush >>> can be removed. >>> >>> And since there is no such target in the current tree, >>> I don't object if you remove that part of code for good reason. >> >> OK, certainly something to keep in mind. But _really_ knowing the >> multipath FLUSH+FUA performance difference (extra special-case code vs >> none) requires a full FLUSH conversion of request-based DM anyway. >> >> In general, request-based DM's barrier/flush code does carry a certain >> maintenance overhead. It is quite a bit of distracting code in the core >> DM which isn't buying us anything.. so we _could_ just remove it and >> never look back (until we have some specific need for num_flush_requests >>> 1 in rq-based DM). > > So, I'm not objecting to your idea. > Could you please create a patch to remove that? I did that yesterday. Will post the patch soon. Thanks. -- tejun