Re: [xfs-masters] 2.6.29-rc: kernel BUG at fs/xfs/support/debug.c:108

From: Dave Chinner <david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org>
To: Alexander Beregalov
	<a.beregalov-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
	xfs-masters-VZNHf3L845pBDgjK7y7TUQ@public.gmane.org,
	xfs-VZNHf3L845pBDgjK7y7TUQ@public.gmane.org,
	kernel-testers-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [xfs-masters] 2.6.29-rc: kernel BUG at fs/xfs/support/debug.c:108
Date: Tue, 13 Jan 2009 08:18:48 +1100	[thread overview]
Message-ID: <20090112211848.GL8071@disturbed> (raw)
In-Reply-To: <a4423d670901120008j728af9cdrbed8bbb938117ea3-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>

On Mon, Jan 12, 2009 at 11:08:55AM +0300, Alexander Beregalov wrote:
> 2009/1/12 Dave Chinner <david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org>:
> > On Mon, Jan 12, 2009 at 03:48:13AM +0300, Alexander Beregalov wrote:
> >> > Hmmmm - this might be getting closer to the source of the bug.
> >> > It's being detecting when reading in the buffer to do a left shift
> >> > now, not during the delete of a record.
> >> >
> >> > I'd suggest that you treat this as the same failure and continue
> >> > the bisect to try to find when no problems show up at all.
> >>
> >> 687b890a184fef263ebb773926e1f4aa69240d01 is the first bad commit.
> >
> >    [XFS] implement generic xfs_btree_lshift
> >
> >    Make the btree left shift code generic. Based on a patch from David
> >    Chinner with lots of changes to follow the original btree implementations
> >    more closely. While this loses some of the generic helper routines for
> >    inserting/moving/removing records it also solves some of the one off bugs
> >    in the original code and makes it easier to verify.
> >
> >> Does it make sense?
> >
> > Yes, a bug in that patch could corrupt the btree in memory which we then trip
> > over later in delrec before it has been written to disk.
> >
> > Thank you for isolating the problem to that commit - it greatly narrows down
> > the amount of code we need to search to find the bug. I'll have a look tonight
> > to see if I can spot the problem.
> 
> It seems 9eaead5 (implement generic xfs_btree_rshift) is really guilty, unless
> the bug "XFS internal error xfs_btree_check_lblock at line 200 of file
> fs/xfs/xfs_btree.c:"
> which I posted 5 hours ago is completely different from the original
> bug message.
> I can not reproduce the bug on 278d0ca14.

Ok, Thanks for clarifying. ;)

I'll have a look through the rshift patch and try to find what
we broke by inspection.

Cheers,

Dave.
-- 
Dave Chinner
david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org