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Date: Mon, 26 Aug 2013 09:36:07 -0400
From: Brian Foster <bfoster@redhat.com>
MIME-Version: 1.0
Subject: Re: [PATCH] Re: XFS: Assertion failed: first <= last && last <
	BBTOB(bp->b_length), file: fs/xfs/xfs_trans_buf.c, line: 568
References: <52165830.8050006@redhat.com> <20130826041330.GU6023@dastard>
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To: Dave Chinner <david@fromorbit.com>
Cc: xfs@oss.sgi.com

On 08/26/2013 12:13 AM, Dave Chinner wrote:
> On Thu, Aug 22, 2013 at 02:28:00PM -0400, Brian Foster wrote:
>> Hi all,
>>
>> I hit an assert on a debug kernel while beating on some finobt work and
>> eventually reproduced it on unmodified/TOT xfs/xfsprogs as of today. I
>> hit it through a couple different paths, first while running fsstress on
>> a CRC enabled filesystem (with otherwise default mkfs options):
>>
>> (These tests are running on a 4p, 4GB VM against a 100GB virtio disk,
>> hosted on a single spindle desktop box).
>>
>> crc=1
>> fsstress -z -fsymlink=1 -n99999999 -p4 -d /mnt/test
>>
>> XFS: Assertion failed: first <= last && last < BBTOB(bp->b_length),
> 
> Directory buffer overrun.
> 
>>  [<ffffffffa031d549>] xfs_trans_log_buf+0x89/0x1b0 [xfs]
>>  [<ffffffffa02e7c1c>] xfs_da3_node_add+0x11c/0x210 [xfs]
>>  [<ffffffffa02ea703>] xfs_da3_node_split+0xc3/0x230 [xfs]
>>  [<ffffffffa02eaa18>] xfs_da3_split+0x1a8/0x410 [xfs]
>>  [<ffffffffa02f743f>] xfs_dir2_node_addname+0x47f/0xde0 [xfs]
> 
> During a split.
> 
> Easily reproduced with "seq 200000 | xargs touch" as Michael Semon
> reported last week.
> 
> The fix demonstrates my concerns about modifying directory code -
> the CRC changes missed a *fundamental* directory format definition,
> and we've only just tripped over it....
> 
>> rm -rf /mnt/test
>>
>> XFS: Assertion failed: first <= last && last < BBTOB(bp->b_length),
> 
> Directory buffer overrun.
> 
>>  [<ffffffffa032b549>] xfs_trans_log_buf+0x89/0x1b0 [xfs]
>>  [<ffffffffa02f61ff>] xfs_da3_node_unbalance+0xef/0x1d0 [xfs]
>>  [<ffffffffa02f98b0>] xfs_da3_join+0x240/0x290 [xfs]
>>  [<ffffffffa030659b>] xfs_dir2_node_removename+0x69b/0x8b0 [xfs]
> 
> During a merge. Not sure why that is happening on a v4 filesystem.
> V5 filesystem, yes, due to the above bug but v4 should not be
> affected.
> 

Interesting, thanks Dave. FWIW, I no longer reproduce the assert in
either scenario with this patch applied. I also don't see how it would
make a difference for a v4 superblock filesystem. Perhaps that
particular test was bogus. I haven't heard if Mark happened to reproduce
that one. Regardless, consider it:

Tested-by: Brian Foster <bfoster@redhat.com>

(xfs: fix calculation of the number of node entries in a dir3 node)

Brian

> Cheers,
> 
> Dave.
> 

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