Re: [PATCH] Re: XFS: Assertion failed: first <= last && last < BBTOB(bp->b_length), file: fs/xfs/xfs_trans_buf.c, line: 568

[Mark Tinguely <tinguely@sgi.com>]

On 08/26/13 16:04, Dave Chinner wrote:
> On Mon, Aug 26, 2013 at 10:00:24AM -0500, Mark Tinguely wrote:
>> On 08/26/13 08:36, Brian Foster wrote:
>>> 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....
>>
>> I agree. As we see here, bugs in common directory code effect all
>> filesystems. It may not matter if the feature the code was written
>> for is enabled or not.
>
> Well, this is *only* a v5 bug. The fact is, the only difference the
> change I made makes to v4 filesystems is that it removed the typedef
> from the sizeof calculation. On my test systems, the value
> mp->m_dir_node_ents is identical for v4 filesystems with or without
> the patch applied.....
>
>>>> 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)
>>
>> I got the XFS v4 to assert on the remove in Linux 3.10 and 3.11.
>
> Did you test 3.9 - before the crc changes were made to the
> filesystem?  i.e. if an invalid mp->m_dir_node_ents value is the
> real cause of the v4 filesystem problem, then it should reproduce on
> just about every kernel we chose to test.
>
>> With the patch, a shorter test on Linux 3.10 did not assert. I will
>> do the full test on Linux 3.10/3.11, review and report back.
>
> Because nobody can explain why this patch would fix a problem on a v4
> filesystem, we need more triage of the v4 problem needs to be done. I
> haven't been able to reproduce the unlink issue (and don't have time
> to do everything), so could you triage the problem further, Mark?
> We really need to understand the root cause of the problem on v4
> filesystems so we can determine what the impact of it is...
>
> Cheers,
>
> Dave.

A full test still asserts on the remove with the patched Linux 3.10 - I 
am about 50% into the retest of Linux 3.10 and then I was planning to 
move back to Linux 3.9.

kdump did not work, so I have no vmcore and therefore no productive 
information.

--Mark.

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