From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Martin K. Petersen" Subject: Re: ATA 4 KiB sector issues. Date: Mon, 08 Mar 2010 22:11:32 -0500 Message-ID: References: <4B947393.2050002@kernel.org> <20100308195847.GC18077@nb.net.home> <4B95B39C.70402@kernel.org> <4B95B5AC.8050101@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: In-Reply-To: <4B95B5AC.8050101@gmail.com> (Tejun Heo's message of "Tue, 09 Mar 2010 11:42:52 +0900") Sender: linux-kernel-owner@vger.kernel.org To: Tejun Heo Cc: Karel Zak , "Martin K. Petersen" , "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, Jim Meyering List-Id: linux-ide@vger.kernel.org >>>>> "Tejun" == Tejun Heo writes: >> This will result in incorrect alignment for drives which lie about >> the physical sector size to work around BIOS/drivers issues (C-1). >> It would probably be best to align to at least 1MiB. Tejun> I misread it. C-1 would be disks w/o alignment information which Tejun> will be aligned to optimal_io_size which again would be 0 and Tejun> thus 1MiB alignment. So, this should work, right? Correct. ATA only provides physical block size whereas SCSI has the extra knobs in the block limits VPD. And consequently ATA block devices have min_io = physical block size and optimal_io = 0. So we'll align to 1 MB by default. -- Martin K. Petersen Oracle Linux Engineering