From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH] block: fix oops with block tag queueing Date: Wed, 27 May 2009 07:53:50 +0900 Message-ID: <4A1C72FE.2040604@gmail.com> References: <1242839186.2881.57.camel@localhost.localdomain> <4A14B4A1.5050303@gmail.com> <1243353531.2815.37.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: Received: from mail-bw0-f222.google.com ([209.85.218.222]:44066 "EHLO mail-bw0-f222.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759459AbZEZWwb (ORCPT ); Tue, 26 May 2009 18:52:31 -0400 Received: by bwz22 with SMTP id 22so4183570bwz.37 for ; Tue, 26 May 2009 15:52:32 -0700 (PDT) In-Reply-To: <1243353531.2815.37.camel@localhost.localdomain> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: James Bottomley Cc: Jens Axboe , linux-scsi James Bottomley wrote: > On Thu, 2009-05-21 at 10:55 +0900, Tejun Heo wrote: >> James Bottomley wrote: >>> commit e8939a50466fd963eb1ba9118c34b9ffb7ff6aa6 >>> Author: Tejun Heo >>> Date: Fri May 8 11:54:16 2009 +0900 >>> >>> block: implement and enforce request peek/start/fetch >>> >>> Added a BUG_ON(blk_queued_rq(req)) to the top of blk_finish_req(). >>> Unfortunately, this checks whether req->queuelist is empty. This list >>> is doing double duty both as the queue list and the tag list, so tagged >>> requests come in here with this not empty and boom (the tag list is >>> emptied by blk_queue_end_tag() lower down). >>> >>> Fix this by moving the BUG_ON to below the end tag we also seem >>> vulnerable to this in blk_requeue_request() as well. I think all uses >>> of blk_queued_rq() need auditing because the check is clearly wrong in >>> the tagged case. >>> >>> Signed-off-by: James Bottomley >> Oops, >> >> Acked-by: Tejun Heo >> >> There are also some drivers which use queuelist for internal purposes >> after dequeueing, which also screws up blk_queued_rq() test in >> addition to being questionable practice to begin with. Maybe we would >> be better off with a flag? > > Either is fine by me ... could we get some fix in, please? I'm > currently carrying this below the merge-base on the SCSI postmerge tree > to prevent my main build server oopsing under SCSI testing ... I'm a bit > surprised we haven't had more reports from linux-oops ... but you can > bet that if Jens moves libata to generic tag use, that will change ... For now, I think your patch is fine and thus the Acked-by. Jens? Thanks. -- tejun