This is less portable, since currently sidelocks rely on /dev/shm.
But, I've seen crazy lustre inconsistencies that make me not trust the
link() method at all, so what can you do.
I have a strace taken on a lustre filesystem on which link() returned 0,
but didn't actually succeed, since the file already existed.
One of the linux man pages recommended using link followed by checking like
this. I was reading it yesterday, but cannot find it now.
