nested file system types

["Steven M. Bellovin" <smb%cs.columbia.edu@localhost>]

As I mentioned the other day, I'm working on mount_vnd(8).  It's pretty
straight-forward; the catch is that I need to be able to specify the
file system type that's layered on top of vnd.  That in turn raises the
question of whether two levels is enough -- it's not; ffs on cgd on vnd
is a perfectly legal (and very useful) construct.  At that point, I
have to wonder about the proper way to next things.  1 is an
interesting number.  2 might be.  3 definitely is not; if we support 3,
we should support N.  How is that best done?


                --Steve Bellovin, http://www.cs.columbia.edu/~smb