Help with "umount -f /mnt/smbfs"

[Jason Martens <me@jasonmartens.com>]

Hey all,
   I have a situation where I mount a smb filesystem, and occasionally 
the server becomes unavailable.  However, after the server is 
unavailable and I try to force unmount the share, I get the following 
error messages, and am unable to unmount it:

server:~# umount -f /mnt/smbfs
umount2: Device or resource busy
umount: //winxpserver/F$: not found
umount: /mnt/smbfs: Illegal seek
umount2: Device or resource busy
umount: /mnt/smbfs: device is busy


I've tried using fuser and lsof on the partition to see if any processes 
are still trying to use it, but I get errors from both of those (after a 
long wait).

lsof: WARNING: can't stat() smbfs file system /mnt/smbfs
     Output information may be incomplete.
lsof: status error on /mnt/smbfs: Input/output error


Any thoughts to how I might be able to unmount this bugger without 
rebooting the machine?

Thanks,
Jason