Re: filesystem shrinks after using xfs_repair

[Dave Chinner <david@fromorbit.com>]

On Sun, Jul 25, 2010 at 11:46:29PM -0700, Eli Morris wrote:
> On Jul 25, 2010, at 11:06 PM, Dave Chinner wrote:
> > On Sun, Jul 25, 2010 at 09:04:03PM -0700, Eli Morris wrote:
> >> On Jul 25, 2010, at 8:45 PM, Dave Chinner wrote:
> > I've just confirmed that the problem does not exist at top-of-tree.
> > The following commands gives the right output, and the repair at the
> > end does not truncate the filesystem:
> > 
> > xfs_io -f -c "truncate $((13427728384 * 4096))" fsfile
> > mkfs.xfs -f -l size=128m,lazy-count=0 -d size=13427728384b,agcount=126,file,name=fsfile
> > xfs_io -f -c "truncate $((16601554944 * 4096))" fsfile
> > mount -o loop fsfile /mnt/scratch
> > xfs_growfs /mnt/scratch
> > xfs_info /mnt/scratch
> > umount /mnt/scratch
> > xfs_db -c "sb 0" -c "p agcount" -c "p dblocks" -f fsfile
> > xfs_db -c "sb 1" -c "p agcount" -c "p dblocks" -f fsfile
> > xfs_db -c "sb 127" -c "p agcount" -c "p dblocks" -f fsfile
> > xfs_repair -f fsfile
> > 
> > So rather than try to triage this any further, can you upgrade your
> > kernel/system to something more recent?
> 
> I can update this to Centos 5 Update 4, but I can't install
> updates forward of it's release date of Dec 15, 2009. The reason
> is that this is the head node of a cluster and it uses the Rocks
> cluster distribution. The newest of Rocks is based on Centos 5
> Update 4, but Rocks systems do not support updates (via yum, for
> example). 
> 
> Updating the OS takes me a day or two for the whole cluster and
> all the user programs. If you're pretty sure that will fix the
> problem, I'll go for it tomorrow. I'd appreciate it very much if
> you could let me know if Centos 5.4 is recent enough that it will
> fix the problem..

The only way I can find out is to load CentOS 5.4 onto a
system and run the above test. You can probably do that just as
easily as I can...

> I will note that I've grown the filesystem several times, and
> while I recall having to unmount and remount the filesystem each
> time for it to report its new size, I've never seen it fall back
> to its old size when running xfs_repair. In fact, the original
> filesystem is about 12 TB, so xfs_repair only reverses the last
> grow and not the previous ones.

Hmmm - I can't recall any bug where unmount was required before
the new size would show up. I know we had problems with arithmetic
overflows in both the xfs_growfs binary and the kernel code, but
they did not manifest in this manner. Hence I can't really say why
you are seeing that behaviour or why this time it is different.

The suggestion of using a recent live CD to do the grow is a good
one - it might be your best option, rather than upgrading everything....

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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