From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: ATA 4 KiB sector issues. Date: Tue, 16 Mar 2010 08:23:13 -0700 Message-ID: <1268752993.21384.23.camel@mulgrave.site> References: <4B947393.2050002@kernel.org> <201003100046.24695.arnd@arndb.de> <1158166a1003100114j6ea329fbh84bfad65dcac90bf@mail.gmail.com> <4B9EED55.10201@kernel.org> <1268720060.21384.10.camel@mulgrave.site> <4B9F2388.2030803@kernel.org> <1268745897.21384.14.camel@mulgrave.site> <4B9F8E1A.2020608@kernel.org> <1268749297.21384.15.camel@mulgrave.site> <4B9F9AAF.6080709@kernel.org> <1268751748.21384.18.camel@mulgrave.site> <4B9FA1C6.7090305@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: Received: from cantor2.suse.de ([195.135.220.15]:35491 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757904Ab0CPPX1 (ORCPT ); Tue, 16 Mar 2010 11:23:27 -0400 In-Reply-To: <4B9FA1C6.7090305@kernel.org> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Tejun Heo Cc: Denys Vlasenko , Arnd Bergmann , "linux-ide@vger.kernel.org" , lkml , Daniel Taylor , Jeff Garzik , Mark Lord , tytso@mit.edu, "H. Peter Anvin" , hirofumi@mail.parknet.co.jp, Andrew Morton , Alan Cox , irtiger@gmail.com, Matthew Wilcox , aschnell@suse.de, knikanth@suse.de, jdelvare@suse.de On Wed, 2010-03-17 at 00:20 +0900, Tejun Heo wrote: > On 03/17/2010 12:02 AM, James Bottomley wrote: > > On Tue, 2010-03-16 at 23:50 +0900, Tejun Heo wrote: > >> e.g. If the first partition begins at CHS 0/32/33 and ends at > >> 12/233/19 and the corresponding LBA addresses are 2048 and 206848, you > >> can solve the equation and determine that the parameters gotta be 63 > >> secs/trk and 255 heads/cyl to make those two pairs of addresses match > >> each other and in fact some BIOSs try to do this depending on > >> configuration (and sometimes falls into infinite loop or causes other > >> boot related problems if the parameters are too uncommon). > > > > for an msdos label, this is illegal, that was Arnd's point. The > > partitions have to begin and end on cylinder boundaries*. Knowing that, > > you can deduce the geometry from the last sector entry. > > > > * at least if you want to preserve windows compatibility, which is what > > most of our partitioning tools seem to do. > > Well, the thing is that > > * Anything remotely modern (>= XP) doesn't give a hoot about cylinder > alignment. > > * Anything older (<= 2000) is very likely to get confused with custom > geometry starting from the BIOS itself. For those cases, the only > thing we can do is aligning partitions to cylinders abiding BIOS > supplied geometry parameters which will usually be 255/63. > > So, using custom geometry doesn't help compatibility at all. Our partitioning tool still obey the integral cylinder rule ... we can argue about whether they should, but what we need is a strategy for fixing what is rather than what should be. James