[BusyBox] pivot_root - devfs problem

[Roberto De Leo]

Hi,
I am trying to build a floppy boot disk for my project (movix.sf.net) 
and I'm almost there, except for a detail: after pivoting I cannot 
umount the old root since I cannot umount its dev directory mounted with 
"-t devfs".

I searched with google and found many messages about this topic here and 
there [it is thanks to them that now almost everything works] but none 
of them managed to solve this last problem.

Any help would be greatly appreciated,
 Roberto De Leo