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Re: xfs_repair segfault + debug info

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: xfs_repair segfault + debug info
From: Mike Grant <mggr@xxxxxxxxx>
Date: Mon, 1 Jun 2015 08:32:43 +0100
Cc: <xfs@xxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20150529222717.GB24666@dastard>
References: <556871CD.6090507@xxxxxxxxx> <20150529222717.GB24666@dastard>
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0
On 29/05/15 23:27, Dave Chinner wrote:
> Given it is choking on directory corruption repair, I'd strong
> recommend trying the current git version (3.2.3-rc1) here:

Thanks for the reply.  I did actually grab the git version (as of May
28) before bothering you all and got something that looked like the same
crash.  The log is here:

https://rsg.pml.ac.uk/shared_files/mggr/xfs_segfault/xfs_repair_fail-git.log

Since I messed up the backtrace on that log, here it is in full (binary
and core also available from the parent directory of the link above):
#0  libxfs_putbuf (bp=0x100010000) at rdwr.c:656
#1  0x000000000041e7ce in longform_dir2_entry_check (hashtab=<optimized
out>, ino_offset=37, irec=0x7f37ddaafe20, need_dot=0x7fff1955bad0,
num_illegal=0x7fff1955bad8,
    ip=0x11696610, ino=20136101, mp=0x7fff1955c170) at phase6.c:2297
#2  process_dir_inode (mp=0x7fff1955c170, agno=agno@entry=0,
irec=irec@entry=0x7f37ddaafe20, ino_offset=ino_offset@entry=37) at
phase6.c:2801
#3  0x00000000004205f6 in traverse_function (wq=0x7fff1955bdc0, agno=0,
arg=0x0) at phase6.c:3085
#4  0x00000000004255fa in prefetch_ag_range (work=0x7fff1955bdc0,
start_ag=<optimized out>, end_ag=204, dirs_only=true, func=0x420560
<traverse_function>) at prefetch.c:906
#5  0x000000000042575b in do_inode_prefetch (mp=0x7fff1955c170,
stride=0, func=0x420560 <traverse_function>, check_cache=<optimized
out>, dirs_only=true) at prefetch.c:969
#6  0x0000000000421365 in traverse_ags (mp=0x7fff1955c170) at phase6.c:3115
#7  phase6 (mp=mp@entry=0x7fff1955c170) at phase6.c:3203
#8  0x00000000004036c6 in main (argc=<optimized out>, argv=<optimized
out>) at xfs_repair.c:808

> Probably because you turned off prefetch, which makes it *slow*. :P

Ah, fair enough - my colleague was trying to reduce RAM usage before we
dug deeper into it and I just picked up his command line when
replicating his results.  I'll ditch the -P in future.

> Just remember, though, that even once the FS has been repaired,
> you'll still have to search for data corruption manually and deal
> with that...

Yeah, we're conscious that the data are probably damaged :(  My main aim
here is to provide some debug data for a xfs_repair crasher.

Cheers,

Mike.


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