linux-kernel - Re: perf bug: bad page map

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Date:	Tue, 19 Nov 2013 08:06:44 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Vince Weaver <vincent.weaver@...ne.edu>
Cc:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	tytso@....edu, adilger.kernel@...ger.ca
Subject: Re: perf bug: bad page map


* Vince Weaver <vincent.weaver@...ne.edu> wrote:

> On Mon, 18 Nov 2013, One Thousand Gnomes wrote:
> 
> > On Mon, 18 Nov 2013 11:41:22 -0500 (EST)
> > Vince Weaver <vincent.weaver@...ne.edu> wrote:
> > 
> > > On Mon, 18 Nov 2013, Peter Zijlstra wrote:
> > > 
> > > > On Fri, Nov 15, 2013 at 01:04:23PM -0500, Vince Weaver wrote:
> > > > > 
> > > > > (figured out the minicom issue).
> > > > > 
> > > > > Anyway while trying to reproduce the last bug I instead got this with
> > > > > the perf_fuzzer.
> > > > > 
> > > > > Is it worth continuing to run and report these issues?  I'm losing track 
> > > > > of all the open bugs.
> > > > 
> > > > This is looks like ext4. Not entirely sure how perf ties into this.
> > > 
> > > It's believable the filesystem could have issues (it's a fuzzer machine, 
> > > so it's had 100+ unclean shutdowns on an SSD drive in the past few months)
> > > but as far as I know there shouldn't have been any filesystem accesses 
> > > happening at all when the bug triggered.
> > 
> > Obvious question - does it pass fsck currently. If it does then
> > presumably it was sane at the time it went pop ?
> 
> # e2fsck -f /dev/sda1                                                           
> e2fsck 1.42.8 (20-Jun-2013)                                                     
> Pass 1: Checking inodes, blocks, and sizes                                      
> Pass 2: Checking directory structure                                            
> Pass 3: Checking directory connectivity                                         
> Pass 4: Checking reference counts                                               
> Pass 5: Checking group summary information                                      
> /dev/sda1: 620972/3514368 files (0.5% non-contiguous), 9796212/14047744 blocks  
> 
> so it looks clean now...

Also, in no way should a corrupted filesystem be able to provoke 
kernel crashes. So even if the filesystem had errors, this would still 
be a kernel bug we need to fix.

Thanks,

	Ingo
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