[PATCH] Add locking to adv(4)

Continuing with the theme of locking older storage drivers, I have
patches to add locking to adv(4) and mark it MPSAFE.  The patches are
from HEAD but should apply to 8 or 9.  If you test it on 8 or 9 please
enable INVARIANTS for at least the initial testing.  Thanks.

http://www.FreeBSD.org/~jhb/patches/adv_locking.patch

-- 
John Baldwin