[Linux-cluster] Scipt to revert GFS2 to GFS1?

[Bob Peterson]

On Mon, 2008-06-09 at 21:19 +0000, Hofmeister, James (WTEC Linux) wrote:
> Hello All,
> 
> I have a customer RHEL-5.1 who converted a GFS1 file system to GFS2 with gfs2_convert.  They are experiencing hangs on unmount of GFS2 file systems since this change. Is there a tool to convert GFS2 file systems back to GFS1?
> 
> Regards,
> James Hofmeister
> Hewlett Packard Linux Solutions Engineer

The short answer is No, the gfs2_convert tool is one-way.  It could be
done because the on-disk formats are not that different.  You would have
to write a tool that does gfs2_convert in reverse: changing all the
inode numbers back to match their disk block locations, converting all
your journals back into giant journal-sized holes in the file system,
and changing all the file flags from standard Linux format to GFS format.
This would not be impossible, but it would be a big project.
The biggest challenge would be in figuring out where the journals belong
and moving anything that got moved to those locations different RGs.
The would be a very good "start" of a "gfs_shrink" tool that doesn't
exist, by the way.

So I recommend they upgrade to the latest and greatest GFS2 code, which
would either be from the nwm git tree, or else the newest RHEL5.2 kmod
RPM.  Then, if they still have a problem unmounting, post the symptoms
and we'll try to address the issues here.

If there is a bug in the unmount code, we need to find and fix it.
I am only aware of one such bug at the moment, which is:

https://bugzilla.redhat.com/show_bug.cgi?id=207697

You may or may not be able to read this bug record; My apologies if you
can't read it; the bug record permissions are out of my control.
This bug is only for the unmount that happens when systems are rebooted.
There is a work-around for it, too, which is to enable the gfs2 init
script.  If you've encountered some other problem, and it can be
recreated on recent levels of GFS2 code, please open a bugzilla record
so we can help find and fix it.

Regards,

Bob Peterson
Red Hat Clustering & GFS