Allow GFS2 to be used for NFS serving and local file access simultaneously

At the present time a GFS2 mount can only be used either for local access or NFS file serving. Doing both can cause panics or file system corruption at present.  This would allow a filesystem to be shared to Windows (via Samba) and Linux clients via NFS.

There has been some work in this area I believe but isn't there yet. I think this bug

 https://bugzilla.redhat.com/show_bug.cgi?id=673198

This would finally allow GFS2 to be a filesystem with *no surprises*, removing one of it's last areas where it is limited compared to single node filesystems.

Colin