From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751243AbWDZXdJ (ORCPT ); Wed, 26 Apr 2006 19:33:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751164AbWDZXdI (ORCPT ); Wed, 26 Apr 2006 19:33:08 -0400 Received: from smtp.osdl.org ([65.172.181.4]:23727 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S1751127AbWDZXdH (ORCPT ); Wed, 26 Apr 2006 19:33:07 -0400 Date: Wed, 26 Apr 2006 16:35:36 -0700 From: Andrew Morton To: Mark Lord Cc: James.Bottomley@SteelEye.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] drivers/scsi/sd.c: fix uninitialized variable in handling medium errors Message-Id: <20060426163536.6f7bff77.akpm@osdl.org> In-Reply-To: <44500033.3010605@rtr.ca> References: <200604261627.29419.lkml@rtr.ca> <1146092161.12914.3.camel@mulgrave.il.steeleye.com> <20060426161444.423a8296.akpm@osdl.org> <44500033.3010605@rtr.ca> X-Mailer: Sylpheed version 1.0.0 (GTK+ 1.2.10; i386-vine-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Mark Lord wrote: > > > That's if we think -stable needs this fixed. > > Let's say a bunch of read bio's get coalesced into a single > 200+ sector request. This then fails on one single bad sector > out of the 200+. Without the patch, there is a very good chance > that sd.c will simply fail the entire request, all 200+ sectors. > > With the patch, it will fail the first block, and then retry > the remaining blocks. And repeat this until something works, > or until everything has failed one by one. Yowch. I have the feeling that this'll take our EIO-handling time from far-too-long to far-too-long*200. I am still traumatised by my recent ten-minute wait for a dodgy DVD to become ejectable. I don't think -stable needs this, personally. > Better, but still not the best. > > What I need to have happen when a request is failed due to bad-media, > is have it split the request into a sequence of single-block requests > that are passed to the LLD one at a time. The ones with real bad > sectors will then be independently failed, and the rest will get done. > > Much better. Much more complex. > > I'm thinking about something like that, just not sure whether to put it > (initially) in libata, sd.c, or the block layer. block, I suspect. My DVD trauma was IDE-induced. Jens is mulling the problem - I'd suggest you coordinate with him. It would be a good thing to fix. It's moderately hard to test, though. Easy enough for DVDs and CDs, but it's harder to take a marker pen to a hard drive.