From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: REQUEST for new 'topology' metrics to be moved out of the 'queue' sysfs directory. Date: Fri, 26 Jun 2009 15:29:40 +0200 Message-ID: <20090626132940.GR23611@kernel.dk> References: <19010.62951.886231.96622@notabene.brown> <125b48b7ffc99a496fbdd512f38cada5.squirrel@neil.brown.name> <20090625194015.GB31415@kernel.dk> <19012.49673.454853.975682@notabene.brown> <20090626125037.GO23611@kernel.dk> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "Martin K. Petersen" , Mike Snitzer , linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, linux-ide@vger.kernel.org, device-mapper development , linux-scsi@vger.kernel.org, linux-fsdevel@vger.kernel.org, Linus Torvalds , Alasdair G Kergon To: NeilBrown Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com List-Id: linux-fsdevel.vger.kernel.org On Fri, Jun 26 2009, NeilBrown wrote: > On Fri, June 26, 2009 10:50 pm, Jens Axboe wrote: > > On Fri, Jun 26 2009, Neil Brown wrote: > >> Every block device has a 'gendisk' (aka generic disk). > >> Every block device also (currently) has a request_queue. > > > > I don't know why you keep saying currently. It has always had a queue, > > and I don't see a good reason why that should change for "special" block > > devices like md/dm/loop/whatnot. > > I say "currently" because I'm planning to create patches to make it > optional, and I want to get you used to the idea :-) > > And md/dm/loop/whatnot are not "special" block devices, any more than > scsi/ide are "special" block devices. They are all just block devices. > They use different mechanisms, but each is just as valid as the other. That was why I put it in quotes, they are just regular devices. > The current code makes 'struct request' based block devices in to > first-class citizens, and all the rest are second class (having to > tag our data structures on ->queue data and/or ->private_data). ?? How is that different from devices, the ones you refer to as first-class citizens? They too store device private data in eg ->queue_data. > I just want all block devices to be equal. There's no such thing as first or second class block devices. The fact that drivers using ->make_request_fn directly do not utilize the full scope of the queue isn't a very interesting fact, imho. -- Jens Axboe