[Review] Fixes to the VFS layer

[Francois Tigeot]

Hi,

While working on the vfs-quota branch, I found some problems in the existing
kernel VFS code.

The attached patches correspond to local commits I have created to fix them.
I'm not too sure if what I've done is ideal, and I'd like these patches
to be reviewed before pushing them to master (or not).

They have been applied to two of my machines (one desktop, one database
server), and do not seem to cause any problem.

-- 
Francois Tigeot