So I've been working on locking up cam using lockmgr locks, and here's
what I have so far:

http://www.theshell.com/~pavalos/wip/cam-lock.patch

Most of the work is obtained from FreeBSD.  I've only been running this
on my SCSI machine for a day, but because the patch is so large, I wanted
to make it available for people to review if they have some spare time.

Thanks,
Peter