Resolve "device is busy" error when doing a umount

If get "device is busy" when doing a umount, e.g.:

[root@server/]# umount /home/data/
umount: /home/data: device is busy


To find out who's still using the share, do a, e.g.:

[root@orion /]# fuser -u -v /home/data/

USER PID ACCESS COMMAND
/home/data/ root 15376 ..c.. vim