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Re: frequent kernel BUG and lockups - 2.6.39 + xfs_fsr

To: Marc Lehmann <schmorp@xxxxxxxxxx>
Subject: Re: frequent kernel BUG and lockups - 2.6.39 + xfs_fsr
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Sun, 7 Aug 2011 00:20:05 +1000
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20110806122556.GB20341@xxxxxxxxxx>
References: <20110806122556.GB20341@xxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Sat, Aug 06, 2011 at 02:25:56PM +0200, Marc Lehmann wrote:
> I get frequent (for servers) lockups and crashes when using 2.6.39. I saw the
> same problems using 3.0.0rc5, 5 and 6, and I think also 2.6.38. I don't see
> this lockups on 2.6.30 or 2.6.26 (all the respetcive latest debian kernels).
> 
> The symtpom slightly differs - sometimes I get thousands of backtraces
> before the machine locks up, usually I get only one, and either the
> machine locks up completely, or only the processes using the filesystem in
> question (presumably) lock - all unkillable.
> 
> The backtraces look all very similar:
> 
>    http://ue.tst.eu/85b9c9f66e36dda81be46892661c5bd0.txt

Tainted kernel. Please reproduce without the NVidia binary drivers.

> this is from a desktop system - it tends to be harder to get these from
> servers.
> 
> all the backtraces crash with a null pointer dereference in xfs_iget, or
> in xfs_trans_log_inode, and always for process xfs_fsr.

and when you do, please record an event trace of the
xfs_swap_extent* trace points while xfs_fsr is running and triggers
a crash. That will tell me if xfs_fsr is corrupting inodes,

> I haven't seen a crash without xfs_fsr.

Then don't use xfs_fsr until we know if it is the cause of the
problem (except to reproduce the problem).

And as I always ask - why do you need to run xfs_fsr so often?  Do
you really have filesystems that get quickly fragmented (or are you
just running it from a cron-job because having on-line
defragmentation is what all the cool kids do ;)? If you are getting
fragmentation, what is the workload that is causing it?

Cheers,

Dave.

-- 
Dave Chinner
david@xxxxxxxxxxxxx

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