From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965166AbWD0QDm (ORCPT ); Thu, 27 Apr 2006 12:03:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965163AbWD0QDl (ORCPT ); Thu, 27 Apr 2006 12:03:41 -0400 Received: from proof.pobox.com ([207.106.133.28]:11962 "EHLO proof.pobox.com") by vger.kernel.org with ESMTP id S965164AbWD0QDk (ORCPT ); Thu, 27 Apr 2006 12:03:40 -0400 Message-ID: <4450EB3E.7000902@pobox.com> Date: Thu, 27 Apr 2006 12:03:10 -0400 From: Mark Lord User-Agent: Thunderbird 1.5.0.2 (X11/20060420) MIME-Version: 1.0 To: Andrew Morton 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 References: <200604261627.29419.lkml@rtr.ca> <1146092161.12914.3.camel@mulgrave.il.steeleye.com> <20060426161444.423a8296.akpm@osdl.org> <44500033.3010605@rtr.ca> <20060426163536.6f7bff77.akpm@osdl.org> In-Reply-To: <20060426163536.6f7bff77.akpm@osdl.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Andrew Morton wrote: > 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. Perhaps, perhaps not. The current behaviour is semi *random*, though. Sometimes it may just fail the entire request (wrong!), sometimes it may do the (almost as wrong) fail a block at a time from the beginning, until the bad sector is passed, and then succeed on the remainder. Ugh. >> 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. -- Mark Lord Real-Time Remedies Inc. mlord@pobox.com