Just a system programmer's tip in this area:

In Unix, you can quickly test for a given mount point directory name
being occupied or not occupied with a mount by performing the command
'ls -di' on it: if the inode number reported is 2, then a mount is
present there, which is to say that it is then the root of the file
system occupying the mount point, rather than a simple directory.

   Richard Sims      http://people.bu.edu/rbs/