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Re: Daily crash in xfs_cmn_err

To: Juerg Haefliger <juergh@xxxxxxxxx>
Subject: Re: Daily crash in xfs_cmn_err
From: Carlos Maiolino <cmaiolino@xxxxxxxxxx>
Date: Mon, 29 Oct 2012 12:23:18 -0200
Cc: xfs@xxxxxxxxxxx
In-reply-to: <CADLDEKtkwaitKCsU21JnsesM70H5AwkEFQFcdmOHE0JU9Oa8nw@xxxxxxxxxxxxxx>
References: <CADLDEKtkwaitKCsU21JnsesM70H5AwkEFQFcdmOHE0JU9Oa8nw@xxxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
Hi,
> 
> I have a node that used to crash every day at 6:25am in xfs_cmn_err
> (Null pointer dereference). I'm running 2.6.38 (yes I know it's old)
> and I'm not reporting a bug as I'm sure the problem has been fixed in
> newer kernels :-) The crashes occurred daily when logrotate ran,
> /var/log is a separate 100GB XFS volume. I finally took the node down
> and ran xfs_check on the the /var/log volume and it did indeed report
> some errors/warnings (see end of email). I then ran xfs_repair (see
> end of email for output) and the node is stable ever since.
> 
> So my questions are:
> 
> 1) I was under the impression that during the mounting of an XFS
> volume some sort of check/repair is performed. How does that differ
> from running xfs_check and/or xfs_repair?
> 
AFAICT, there is no repair or check happening at mount time, only information
needed to mount the filesystem are checked, everything else (like consistency of
blocks and inodes) are not checked during mount time. Maybe you mean the journal
replay that happens during mount time?

> 2) Any ideas how the filesystem might have gotten into this state? I
> don't have the history of that node but it's possible that it crashed
> previously due to an unrelated problem. Could this have left the
> filesystem is this state?
> 
> 3) What exactly does the ouput of the xfs_check mean? How serious is
> it? Are those warning or errors? Will some of them get cleanup up
> during the mounting of the filesystem?
> 
comments below

> 4) We have a whole bunch of production nodes running the same kernel.
> I'm more than a little concerned that we might have a ticking timebomb
> with some filesystems being in a state that might trigger a crash
> eventually. Is there any way to perform a live check on a mounted
> filesystem so that I can get an idea of how big of a problem we have
> (if any)? i don't claim to know exactly what I'm doing but I picked a
> node, froze the filesystem and then ran a modified xfs_check (which
> bypasses the is_mounted check and ignores non-committed metadata) and
> it did report some issues. At this point I believe those are false
> positive. Do you have any suggestions short of rebooting the nodes and
> running xfs_check on the unmounted filesystem?
> 
You must umount the filesystem before run xfs_repair/check, even with a freezed
fs you may get inconsistent data wich may lead you to have more problems.

> Thanks
> ....Juerg
> 
> 
> (initramfs) xfs_check  /dev/mapper/vg0-varlog
> block 0/3538 expected type unknown got free2
> block 0/13862 expected type unknown got free2
> block 0/13863 expected type unknown got free2
> 
> <SNIP>
> 
> block 0/16983 expected type unknown got free2
> block 0/16984 expected type unknown got free2
> block 0/21700 expected type unknown got data
> block 0/21701 expected type unknown got data
> 
> <SNIP>
> 
> block 0/21826 expected type unknown got data
> block 0/21827 expected type unknown got data
> block 0/21700 claimed by inode 178, previous inum 148
> block 0/21701 claimed by inode 178, previous inum 148
> 
> <SNIP>
> 
> block 0/21826 claimed by inode 178, previous inum 148
> block 0/21827 claimed by inode 178, previous inum 148
> block 0/1250 expected type unknown got data
> block 0/1251 expected type unknown got data
> 
> <SNIP>
> 
> block 0/1264 expected type unknown got data
> block 0/1265 expected type unknown got data
> block 0/1250 claimed by inode 1706, previous inum 148
> block 0/1251 claimed by inode 1706, previous inum 148
> 
> <SNIP>
> 
> block 0/1264 claimed by inode 1706, previous inum 148
> block 0/1265 claimed by inode 1706, previous inum 148
> block 0/16729 expected type unknown got data
> block 0/16730 expected type unknown got data
> 
> <SNIP>
> 
> block 0/16889 expected type unknown got data
> block 0/16890 expected type unknown got data
> block 0/16729 claimed by inode 1710, previous inum 148
> block 0/16730 claimed by inode 1710, previous inum 148
> 
> <SNIP>
> 
> block 0/16889 claimed by inode 1710, previous inum 148
> block 0/16890 claimed by inode 1710, previous inum 148
> block 0/3523 expected type unknown got data
> block 0/3524 expected type unknown got data
> 
> <SNIP>
> 
> block 0/3536 expected type unknown got data
> block 0/3537 expected type unknown got data
> block 0/3523 claimed by inode 1994, previous inum 148
> block 0/3524 claimed by inode 1994, previous inum 148
> 
> <SNIP>
> 
> block 0/3536 claimed by inode 1994, previous inum 148
> block 0/3537 claimed by inode 1994, previous inum 148
> block 0/510 type unknown not expected
> block 0/511 type unknown not expected
> block 0/512 type unknown not expected
> 
> <SNIP>
> 
> block 0/2341 type unknown not expected
> block 0/2342 type unknown not expected
> 
> 
> 
> (initramfs) xfs_repair /dev/mapper/vg0-varlog
> Phase 1 - find and verify superblock...
> Phase 2 - using internal log
>         - zero log...
>         - scan filesystem freespace and inode maps...
>         - found root inode chunk
> Phase 3 - for each AG...
>         - scan and clear agi unlinked lists...
>         - process known inodes and perform inode discovery...
>         - agno = 0
> data fork in ino 148 claims free block 3538
> data fork in ino 148 claims free block 13862
> data fork in ino 148 claims free block 13863
> data fork in ino 148 claims free block 16891
> data fork in ino 148 claims free block 16892
> data fork in regular inode 178 claims used block 21700
> bad data fork in inode 178
> cleared inode 178
> data fork in regular inode 1706 claims used block 1250
> bad data fork in inode 1706
> cleared inode 1706
> data fork in regular inode 1710 claims used block 16729
> bad data fork in inode 1710
> cleared inode 1710
> data fork in regular inode 1994 claims used block 3523
> bad data fork in inode 1994
> cleared inode 1994
>         - agno = 1
>         - agno = 2
>         - agno = 3
>         - process newly discovered inodes...
> Phase 4 - check for duplicate blocks...
>         - setting up duplicate extent list...
>         - check for inodes claiming duplicate blocks...
>         - agno = 0
>         - agno = 1
> entry "syslog" at block 0 offset 2384 in directory inode 128
> references free inode 178
>         - agno = 3
>       clearing inode number in entry at offset 2384...
>         - agno = 2
> data fork in ino 148 claims dup extent, off - 0, start - 1250, cnt 16
> bad data fork in inode 148
> cleared inode 148
> entry "nova-api.log" at block 0 offset 552 in directory inode 165
> references free inode 1994
>       clearing inode number in entry at offset 552...
> entry "nova-network.log.6" at block 0 offset 2608 in directory inode
> 165 references free inode 1706
>       clearing inode number in entry at offset 2608...
> entry "nova-api.log.6" at block 0 offset 4032 in directory inode 165
> references free inode 1710
>       clearing inode number in entry at offset 4032...
> Phase 5 - rebuild AG headers and trees...
>         - reset superblock...
> Phase 6 - check inode connectivity...
>         - resetting contents of realtime bitmap and summary inodes
>         - traversing filesystem ...
> entry "syslog.1" in directory inode 128 points to free inode 148
> bad hash table for directory inode 128 (no data entry): rebuilding
> rebuilding directory inode 128
> bad hash table for directory inode 165 (no data entry): rebuilding
> rebuilding directory inode 165
>         - traversal finished ...
>         - moving disconnected inodes to lost+found ...
> Phase 7 - verify and correct link counts...
> done
> 

Looking through these logs, I'd say that the system crashed before and was not
using a kind of storage without a battery backed unit and some metadata has been
lost during the crash, or, a xfs_repair were ran, or the filesystem mounted
after drop the dirty logs into the filesystem (like run xfs_repair -L).

These are my points of view though, some other people may give you more detailed
answer.

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-- 
--Carlos

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