Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1755170Ab0H0SDu (ORCPT <rfc822;w@1wt.eu>);
	Fri, 27 Aug 2010 14:03:50 -0400
Received: from mail-ey0-f174.google.com ([209.85.215.174]:37430 "EHLO
	mail-ey0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1752357Ab0H0SDr (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Fri, 27 Aug 2010 14:03:47 -0400
DomainKey-Signature: a=rsa-sha1; c=nofws;
        d=gmail.com; s=gamma;
        h=date:from:to:cc:subject:message-id:references:mime-version
         :content-type:content-disposition:in-reply-to:user-agent;
        b=Bo0UOQoddIqUE8i55ThwnOENlyr9r8ladu3PcK8G1q2SUwq5yG+vi52y/PBcVlLeRR
         X+6lhqTjxD8HhFGtfhDBiYWgO9q367y8nUne6iH/34M98w/+QSQ4MNrxGYO1K4W0rMRC
         l7GrONzO7Kr9D5hKqtC/gnne+HLzH6UYJRRxM=
Date: Fri, 27 Aug 2010 20:03:01 +0200
From: "Carlos R. Mafra" <crmafra2@gmail.com>
To: liubo <liubo2009@cn.fujitsu.com>
Cc: linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org,
        Chris Mason <chris.mason@oracle.com>
Subject: Re: [2.6.35.3] BUG: unable to handle kernel NULL pointer
 dereference at (null)
Message-ID: <20100827180301.GA5981@Pilar.aei.mpg.de>
References: <20100826095357.GA7202@Pilar.aei.mpg.de>
 <4C778779.1090808@cn.fujitsu.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <4C778779.1090808@cn.fujitsu.com>
User-Agent: Mutt/1.5.20 (2009-06-14)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 2264
Lines: 52

On Fr 27.Aug'10 at 17:38:01 +0800, liubo wrote:
> On 08/26/2010 05:53 PM, Carlos R. Mafra wrote:
> > Hi,
> >
> > I've just got this BUG: message in dmesg which I think is btrfs related.
> >   
> [...]
> 
> > [  148.152107] Call Trace:
> > [  148.152113]  [<ffffffff8104e730>] ? process_timeout+0x0/0x10
> > [  148.152118]  [<ffffffff8118a42d>] end_workqueue_fn+0x10d/0x130
> > [  148.152122]  [<ffffffff811b98f0>] worker_loop+0xb0/0x5a0
> > [  148.152126]  [<ffffffff811b9840>] ? worker_loop+0x0/0x5a0
> > [  148.152130]  [<ffffffff8105b60e>] kthread+0x8e/0xa0
> > [  148.152135]  [<ffffffff81003a54>] kernel_thread_helper+0x4/0x10
> > [  148.152138]  [<ffffffff8105b580>] ? kthread+0x0/0xa0
> > [  148.152142]  [<ffffffff81003a50>] ? kernel_thread_helper+0x0/0x10
> > [  148.152144] Code: d3 ff ff 89 c2 b8 01 00 00 00 85 d2 75 56 4c 39 eb 77 51 0f 1f 80 00 00 00 00 48 89 de 49 8b 7c 24 10 48 c1 ee 0c e8 3f 21 ef ff <f6> 00 08 74 2a 48 89 c7 48 81 c3 00 10 00 00 e8 4b af ef ff 49 
> > [  148.152176] RIP  [<ffffffff811b1301>] extent_range_uptodate+0x51/0xa0
> > [  148.152180]  RSP <ffff880079acddd0>
> > [  148.152182] CR2: 0000000000000000
> > [  148.152185] ---[ end trace c11a5009b12451d7 ]---
> >
> >   
> 
> Hi, Carlos,
> Did you hit this bug under heavy memory stress?

Not at all! 

My laptop had been recently booted (see the timings in the dmesg)
and it was basically idle: just a couple xterms and WindowMaker running,
apart from the chromium which I tried to open and led to the bug.
 
> And, could you reproduce the bug? or show some reproduce steps for us?

Unfortunately not. That was the first time, and it didn't repeat so far.

> After digging into extent_range_uptodate(), IMO, this NULL pointer bug that issued page 
> can barely be hit. 
> 
> Maybe, due to heavy memory stress, a page of the extent_buffer has been freed before, 
> which leads that it is missing in page_cache and return NULL.

Could it be that the memory card had some bad block and btrfs could not
recover from the failure?

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/