I've been going through Mark's changes with a fine toothcomb and this merges
most of them. Its tested on 64bit SMP hardware and seems to be fine. There
are a couple of Mark's changes I've left out for now but there isnt really
an easy way to break down the changes further.

This fixes a whole host of problems including random hangs under high load
Signed-off-by: Alan Cox <alan@redhat.com>
        
Original contribution under GPL from Adaptec, updates checking by Red Hat
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>