On Mon, 19 Jul 1999, Bill Studenmund wrote:

# And it's REALLY dangerous. While the setup you describe (multiple
# directory entries sitting in the same directory point to the same dir) 
# isn't super evil, the ability to give a directory multiple parrents
# (directories which contain an entry pointing to it) is nasty. As Christos
# said, you can get into a position of making many tools get into infinite
# loops, and to make fsck unusable. Also, you could mess up the vnode
# locking & get into deadlocks as the lookup protocol assumes the directory
# tree is a tree. :-)

There's nothing of this sort that I've seen that a good clri
wouldn't fix, but I'm kind of glad to see the VDIR check
in there, courtesy of christos.  I ain't taking it out; is anyone
else?

I've heard that when directories are linkable, if you have two
directories a and b, and you link b to a/c and a to b/d, it will
do one of:
	- hang the machine hard
	- panic the machine with "panic: locking against myself",
		"panic: ialloc: dup ialloc" or something similarly evil

				--*greywolf;
--
NetBSD: the second best thing you can get for free