From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1755054Ab1GLBXJ (ORCPT <rfc822;w@1wt.eu>);
	Mon, 11 Jul 2011 21:23:09 -0400
Received: from mx1.redhat.com ([209.132.183.28]:25010 "EHLO mx1.redhat.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1751363Ab1GLBXH (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Mon, 11 Jul 2011 21:23:07 -0400
Date: Mon, 11 Jul 2011 21:22:06 -0400
From: Mike Snitzer <snitzer@redhat.com>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Roland Dreier <roland@kernel.org>, Jens Axboe <axboe@kernel.dk>,
        James Bottomley <James.Bottomley@hansenpartnership.com>,
        Heiko Carstens <heiko.carstens@de.ibm.com>, linux-scsi@vger.kernel.org,
        Steffen Maier <maier@linux.vnet.ibm.com>,
        "Manvanthara B. Puttashankar" <manvanth@linux.vnet.ibm.com>,
        Tarak Reddy <tarak.reddy@in.ibm.com>,
        "Seshagiri N. Ippili" <sesh17@linux.vnet.ibm.com>,
        linux-kernel@vger.kernel.org,
        device-mapper development <dm-devel@redhat.com>,
        Vivek Goyal <vgoyal@redhat.com>, Tejun Heo <tj@kernel.org>,
        jaxboe@fusionio.com
Subject: Re: block: Check that queue is alive in blk_insert_cloned_request()
Message-ID: <20110712012206.GA30690@redhat.com>
References: <CAMM=eLfzKuw-2vbERV6D7dAHb1BWopOKZ=dB7vWxcxSCoj6Tkw@mail.gmail.com>
 <Pine.LNX.4.44L0.1107112050480.17690-100000@netrider.rowland.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <Pine.LNX.4.44L0.1107112050480.17690-100000@netrider.rowland.org>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Mon, Jul 11 2011 at  8:52pm -0400,
Alan Stern <stern@rowland.harvard.edu> wrote:

> On Mon, 11 Jul 2011, Mike Snitzer wrote:
> 
> > [cc'ing dm-devel, vivek and tejun]
> > 
> > On Fri, Jul 8, 2011 at 7:04 PM, Roland Dreier <roland@kernel.org> wrote:
> > > From: Roland Dreier <roland@purestorage.com>
> > >
> > > This fixes crashes such as the below that I see when the storage
> > > underlying a dm-multipath device is hot-removed. ?The problem is that
> > > dm requeues a request to a device whose block queue has already been
> > > cleaned up, and blk_insert_cloned_request() doesn't check if the queue
> > > is alive, but rather goes ahead and tries to queue the request. ?This
> > > ends up dereferencing the elevator that was already freed in
> > > blk_cleanup_queue().
> > 
> > Your patch looks fine to me:
> > Acked-by: Mike Snitzer <snitzer@redhat.com>
> 
> There's still the issue that Stefan Richter pointed out: The test for a 
> dead queue must be made _after_ acquiring the queue lock, not _before_.

Yes, quite important.

Jens, can you tweak the patch or should Roland send a v2?