TODO list:
find "device busy" bug (probably missing dput/release_path somewhere)
extensive testing, compile kernel
rewrite getdents for layers>=2
sort & uniq within getdents and whiteout entry support
allow specification of excluded directories (e.g. mount points) 
better .. handling 
fs= param (with magic numbers as in "grep SUPER_MAGIC include/linux/*.h")

`grep TODO *`
