Comment 49 for bug 47848

Hm, it's possible that this is no longer needed (if Ubuntu is using grub > 0.97). According to http://oss.sgi.com/projects/xfs/faq.html#grubwork :

Q: Does GRUB work with XFS?

There is native XFS filesystem support for GRUB starting with version 0.91 and onward. Unfortunately, GRUB used to make incorrect assumptions about being able to read a block device image while a filesystem is mounted and actively being written to, which could cause intermittent problems when using XFS. This has reportedly since been fixed, and the 0.97 version (at least) of GRUB is apparently stable.