From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Lord Subject: Re: [PATCH] libata: Don't trust current capacity values in identify words 57-58 Date: Mon, 16 Feb 2009 18:03:20 -0500 Message-ID: <4999F0B8.7020700@rtr.ca> References: <4999CA54.1060306@gmail.com> <4999F032.6060107@rtr.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from rtr.ca ([76.10.145.34]:37769 "EHLO mail.rtr.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751102AbZBPXDT (ORCPT ); Mon, 16 Feb 2009 18:03:19 -0500 In-Reply-To: <4999F032.6060107@rtr.ca> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Robert Hancock Cc: linux-kernel , ide , Jeff Garzik , Sergei Shtylyov , =?UTF-8?B?SGFubm8gQsO2Y2s=?= Mark Lord wrote: > Robert Hancock wrote: >> Hanno B=C3=B6ck reported a problem where an old Conner CP30254 240MB= hard=20 >> drive >> was reported as 1.1TB in capacity by libata: >> >> http://lkml.org/lkml/2009/2/13/134 >> >> This was caused by libata trusting the drive's reported current=20 >> capacity in sectors in identify words 57 and 58 if the drive does no= t=20 >> support LBA and the >> current CHS translation values appear valid. Unfortunately it seems = older >> ATA specs were vague about what this field should contain and a numb= er=20 >> of drives >> used values with wrong byte order or that were totally bogus. There'= s no >> unique information that it conveys and so we can just calculate the=20 >> number >> of sectors from the reported current CHS values. >> >> Signed-off-by: Robert Hancock > .. >> } else { >> if (ata_id_current_chs_valid(id)) >> - return ata_id_u32(id, 57); >> + return id[54] * id[55] * id[56]; >> else >> return id[1] * id[3] * id[6]; > .. >=20 > NAK. That's not quite correct, either. >=20 > The LBA capacity can be larger than the CHS capacity, > so we have to use the reported LBA values if at all possible. >=20 > That's why ata_id_is_lba_capacity_ok() exists, > and why it looks so peculiar. >=20 > Some of those early drives really did require that kind of logic. =2E. Mind you, one can do better than that, too. The "10% solution" in there right now is a bit of a (working) hack. It really probably just needs to check for a flipped-LBA that is within +/- one full cylinder of the CHS capacity. Cheers