NAME
valid_link - controls the use of link(3)
SYNOPSIS
int valid_link(string from, string to);
DESCRIPTION
The driver calls valid_link(from, to) in the master object from inside the
link(from, to) efunction. If valid_link() returns 0, then the link()
will fail. If valid_link() returns 1, then the link(3) will succeed if
rename() would succeed if called with the same arguments.