Re: _xfs_buf_find: Block out of range, then umount hung

Chris Dunlop
2018-01-16T01:35:39Z

On Mon, Jan 15, 2018 at 07:02:58AM -0500, Brian Foster wrote:
> On Sun, Jan 14, 2018 at 01:52:28AM +1100, Chris Dunlop wrote:
>> Hi,
>>
>> tl;dr: a filesystem corruption (cause unknown) has produced an unkillable
>> umount. Is the only recourse to reboot?
>
> From this particular state, probably.

Yeah, I figured that and rebooted.

> So for one reason or another, you end up trying to remove a bogus block
> number from the AGFL (perhaps the old agfl size issue?).

This stuff?

https://www.spinics.net/lists/xfs/msg42213.html

FYI the filesystem was created on linux-3.18.25 and the error appeared shortly
after moving to linux-4.9.76.

>> Jan 13 19:57:31 b2 kernel: ================================================
>> Jan 13 19:57:31 b2 kernel: [ BUG: lock held when returning to user space! ]
>> Jan 13 19:57:31 b2 kernel: 4.9.76-otn-00021-g2af03421 #1 Tainted: G W
>> Jan 13 19:57:31 b2 kernel: ------------------------------------------------
>> Jan 13 19:57:31 b2 kernel: tp_fstore_op/31412 is leaving the kernel with locks still held!
>> Jan 13 19:57:31 b2 kernel: 1 lock held by tp_fstore_op/31412:
>> Jan 13 19:57:31 b2 kernel: #0: (sb_internal){......}, at: [<ffffffffa07692a3>] xfs_trans_alloc+0xe3/0x130 [xfs]
>
> Though it looks like we return to userspace in transaction context..?
> This is the same pid as above and the current code looks like the
> transaction should be cancelled in xfs_attr_set(). We're somewhere down
> in xfs_attr_leaf_addname(), however. From there, both calls to
> xfs_defer_finish() jump to out_defer_cancel on failure, which sets
> args->trans = NULL before we return. Hmm, that looks like a bug to me.
>
> Are you able to reproduce this particular hung unmount behavior? If so,
> does anything change with something like the appended hunk? Note that
> you may have to backport that to v4.9-<whatever> since it appears that
> is before out_defer_cancel was created.

Sorry, wasn't able to reproduce: once it was up again mount didn't succeed:

# mount /dev/sdp1 /var/lib/ceph/osd/ceph-60
mount: mount /dev/sdp1 on /var/lib/ceph/osd/ceph-60 failed: Structure needs cleaning
# mount -f /dev/sdp1 /var/lib/ceph/osd/ceph-60
# umount /var/lib/ceph/osd/ceph-60
umount: /var/lib/ceph/osd/ceph-60: not mounted

I tried an 'xfs_repair -L' which found some stuff, but I don't know if the
"stuff" was due to the log being lost or part of the original problem:

# xfs_repair -L -vv /dev/sdp1
Phase 1 - find and verify superblock...
- max_mem = 148590945, icount = 203072, imem = 793, dblock = 233112145, dmem = 113824
- block cache size set to 18553288 entries
Phase 2 - using internal log
- zero log...
zero_log: head block 554618 tail block 553989
ALERT: The filesystem has valuable metadata changes in a log which is being
destroyed because the -L option was used.
- scan filesystem freespace and inode maps...
bad agbno 4294967295 in agfl, agno 2
freeblk count 8 != flcount 7 in ag 2
bad agbno 4294967295 in agfl, agno 1
freeblk count 7 != flcount 6 in ag 1
sb_ifree 42557, counted 42256
sb_fdblocks 82529171, counted 82532805
...

The rest of the output didn't look particularly interesting to my untrained
eye, but the full output is available at: https://pastebin.com/KD7BKTLu

The mount succeeded after this.

In the end, as I wasn't sure of the status of the data and it was replicated
elsewhere anyway, I blew away the filesystem and started again.

Thanks for your time!

Chris

>
> Brian
>
> ---8<---
>
> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> index a76914db72ef..e86c51d39e66 100644
> --- a/fs/xfs/libxfs/xfs_attr.c
> +++ b/fs/xfs/libxfs/xfs_attr.c
> @@ -717,7 +717,6 @@ xfs_attr_leaf_addname(xfs_da_args_t *args)
> return error;
> out_defer_cancel:
> xfs_defer_cancel(args->dfops);
> - args->trans = NULL;
> return error;
> }
>