/usr as a partition. Possible to upgrade?

My system is configured with /usr on it's own partition (old time unix habit...)
After getting the upgrade notification I went through the loop of starting to upgrade and rebooting with the upgrade prep boot loader entry. (I say loop, because each time it rebooted I got an upgrade notification and it asked me to reboot with the same option.)
Having read a little about what the upgrade prep is trying to do, I don't think it's possible to upgrade my system. Once /bin/mount is moved to /usr/bin/mount it won't be possible to mount /usr (because the mount command won't be on a mounted file system). Have I missed something?
Thanks,
Rob.
After getting the upgrade notification I went through the loop of starting to upgrade and rebooting with the upgrade prep boot loader entry. (I say loop, because each time it rebooted I got an upgrade notification and it asked me to reboot with the same option.)
Having read a little about what the upgrade prep is trying to do, I don't think it's possible to upgrade my system. Once /bin/mount is moved to /usr/bin/mount it won't be possible to mount /usr (because the mount command won't be on a mounted file system). Have I missed something?
Thanks,
Rob.