From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759654AbZELAye (ORCPT ); Mon, 11 May 2009 20:54:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754611AbZELAyW (ORCPT ); Mon, 11 May 2009 20:54:22 -0400 Received: from hera.kernel.org ([140.211.167.34]:33715 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753807AbZELAyV (ORCPT ); Mon, 11 May 2009 20:54:21 -0400 Message-ID: <4A08C871.9000100@kernel.org> Date: Tue, 12 May 2009 09:53:05 +0900 From: Tejun Heo User-Agent: Thunderbird 2.0.0.19 (X11/20081227) MIME-Version: 1.0 To: Konrad Rzeszutek CC: device-mapper development , Kay Sievers , jeff@garzik.org, linux-scsi@vger.kernel.org, Mauelshagen@redhat.com, linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org, jens.axboe@oracle.com, martin.petersen@oracle.com Subject: Re: [dm-devel] Re: [PATCH 1/3] block: add alt_size References: <1241828002-12742-1-git-send-email-tj@kernel.org> <1241828002-12742-2-git-send-email-tj@kernel.org> <4A058D5C.6030206@kernel.org> <20090511134534.GA32678@mars.virtualiron.com> In-Reply-To: <20090511134534.GA32678@mars.virtualiron.com> X-Enigmail-Version: 0.95.7 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.0 (hera.kernel.org [127.0.0.1]); Tue, 12 May 2009 00:53:10 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Konrad Rzeszutek wrote: > .. snip .. >>> Also, values with magic block counts, while there is no way to get the >>> blocksize with the same interface, are pretty weird. I think the >>> current "size" attribute is just a bug. >> Logical block size is fixed at 512 bytes. Offset and size are always >> represented in multiples of 512 bytes and only get converted to >> hardware block size in the lld. > > That interpretation is at odds with the work that Martin Peterson is > doing with the 4K support. In the e-mail titled: "Re: [PATCH 4 of 8] sd: > Physical block size and alignment support", > Message-ID: he says: > > " > Konrad> about what a 'logical block', and 'physical block' is > Konrad> vs. 'hardware sector' ? > > Well, another item on my todo list is to kill the notion of hardware > sector completely. The protocols have been referring to logical blocks > for ages. > > It hasn't been a big problem until now because logical block size has > been equal to the hardware sector size. That's no longer a valid > assumption. > " > > Are the ATA/SCSI/etc specs at odds with each other about this? Hardware specs aren't of concern here. The logical block concept is there simply to give 9 bit addressing advantage, nothing more, nothing less. If hardware's sector size doesn't match it, the lld should be mapping the sector addresses and sizes and cdrom and a few other drives have been doing that for ages. There's nothing new about devices with sectors larger than 512 bytes. Thanks. -- tejun