There is some code in UFS and devfs that assumes that one can safely
copy a name component into a buffer of size MAXNAMLEN or SPECNAMELEN,
respectively, while the limit on name components is NAME_MAX. All of
these constants are equal, but one may try changing them (I know that
OneFS has done this, for instance). Add a seatbelt to help catch cases
where this isn't done correctly.
Reported by: Alexey Kulaev <email@example.com>