The following patch against recent -mm kernels implements lockless
radix tree lookups using RCU. No users of this new facility yet,
but it is a requirement for lockless pagecache.

I have recently added (what I think are) the missing rcu_dereference
calls needed on Alpha, and the implementation now has no known bugs.
(actually that's wrong: the new capabilities in the lookup APIs need
commenting)

I realise that radix-tree.c isn't a trivial bit of code so I don't
expect reviews to be forthcoming, but if anyone had some spare time
to glance over it that would be great.

Is my given detail of the implementation clear? Sufficient? Would
diagrams be helpful?

Thanks,
Nick

-- 
SUSE Labs, Novell Inc.