bad@ora.de said:
> That gives us a different ordering problem, though, namely the case
> when a local FS should be mounted on a directory of a remote FS.
> 
> I wouldn't know why I would want to do that, but maybe someone depends
> on this. 

I regularely do this - mount a ram disk onto /tmp
on diskless machines.
Once I had a local hard disk union mounted over a
read-only NFS /usr/src. This worked basically as long
as I didn't touch the local filesystem directly; the reason
I stopped it was that there was no speed increase worth the
effort - probably due to the expensive NFS directory lookups.

best regards
Matthias