Comment 17 for bug 8058

As far as Daniel Silverstone and I could determine, xfs_freeze -f followed by
xfs_freeze -u is not sufficient; we did try doing this in grub-install, and it
still hung. It may work sometimes, but it doesn't break the race condition.

I think the right answer for Warty is to totally refuse to put /boot on XFS. As
a rule, people seem to ignore the warning.