Finding Open Files in FreeBSD

Following up the same in Solaris, here's how to identify open files on
a particular filesystem (FS) in a FreeBSD environment.  Our host details
for this are:

Overlaid Mount Problem

In UNIX environments, it's not uncommon to see various file systems (FS)
mounted, be it local storage, fiber attached from a SAN, network based
like NFS, etc.  These mounts may be exist for any number of reasons,
such as application data, user home directories, additional log space,