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Re: [PATCH] Re: XFS: Assertion failed: first <= last && last < BBTOB(bp-

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH] Re: XFS: Assertion failed: first <= last && last < BBTOB(bp->b_length), file: fs/xfs/xfs_trans_buf.c, line: 568
From: Mark Tinguely <tinguely@xxxxxxx>
Date: Mon, 26 Aug 2013 16:19:06 -0500
Cc: Brian Foster <bfoster@xxxxxxxxxx>, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20130826210445.GW6023@dastard>
References: <52165830.8050006@xxxxxxxxxx> <20130826041330.GU6023@dastard> <521B59C7.1080803@xxxxxxxxxx> <521B6D88.30608@xxxxxxx> <20130826210445.GW6023@dastard>
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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@xxxxxxxxxx>

(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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