Adding linux_link(2) system call, second round

[manu%netbsd.org@localhost (Emmanuel Dreyfus)]

Quick summary for the impatient: NetBSD link(2) first resolves symlinks
before doing the actual link to the target. As a result, NetBSD link(2)
fails on symlinks to directories or to non existent targets.

On the other side, Linux link(2) is dumb and just create a second
symlink with the same inode. Therefore it does not care about the
symlink target, and will succeed even if it is a directory or if it is
nonexistent. 

Both behaviors are standard compliant, since SUSv2 says nothing about
resolving symlinks or not. I found at least one program (glusterfs),
which assumes the Linux behavior, and is a real pain to fix on NetBSD
because of that.

I proposed to implement a linux_link(2), or lazy_link(2), whatever
sounds nicer. It seems it does not reach consensus, but I am not sure I
understood why: what are the problems that would be introduced by adding
such a system call? At least I can tell what benefit it would have: it
would ease porting from Linux.

-- 
Emmanuel Dreyfus
http://hcpnet.free.fr/pubz
manu%netbsd.org@localhost