Re: xfs_repair segfaults with ag_stride option

On 2/6/12 5:19 AM, Tom Crane wrote:

Eric Sandeen wrote:

...

quoted

Newer tools are fine to use on older filesystems, there should be no
  

Good!

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issue there.

running fsr can cause an awful lot of IO, and a lot of file reorganization.
(meaning, they will get moved to new locations on disk, etc).

How bad is it, really?  How did you arrive at the 40% number?  Unless
  

xfs_db -c frag -r <block device>

which does:

                answer = (double)(extcount_actual - extcount_ideal) * 100.0 /
                         (double)extcount_actual;

If you work it out, if every file was split into only 2 extents, you'd have
"50%" - and really, that's not bad.  40% is even less bad.

Some users on our compute farm with large jobs (lots of I/O) find they take longer than with some of our other scratch arrays hosted on other machines.  We also typically find many nfsd tasks in an uninterruptible wait state (sync_page), waiting for data to be copied in from the FS.

So fragmentation may not be the problem... 

-Eric

quoted

you see perf problems which you know you can attribute to fragmentation,
I might not worry about it.

You can also check the fragmentation of individual files with the
xfs_bmap tool.

-Eric
  

Thanks for your advice.
Cheers
Tom.

quoted

quoted

Tom.

Christoph Hellwig wrote:
   

quoted

Hi Tom,

On Wed, Feb 01, 2012 at 01:36:12PM +0000, Tom Crane wrote:
 
     

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Dear XFS Support,
   I am attempting to use xfs_repair to fix a damaged FS but always
get a segfault if and only if -o ag_stride is specified. I have
tried ag_stride=2,8,16 & 32.  The FS is approx 60T. I can't find
reports of this particular problem on the mailing list archive.
Further details are;

xfs_repair version 3.1.7, recently downloaded via git repository.
uname -a
Linux store3 2.6.18-274.17.1.el5 #1 SMP Wed Jan 11 11:10:32 CET 2012
x86_64 x86_64 x86_64 GNU/Linux
            

Thanks for the detailed bug report.

Can you please try the attached patch?

        

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