From: Alexander Duyck

These patches introduce two new primitives for synchronizing cache-enabled
memory writes and reads.  These two new primitives are:

	fast_rmb()
	fast_wmb()

Not sure I like the names.
If the aim is to sync data into the local cache so that hardware
that is doing cache-snooping accesses sees the data then maybe
	local_rmb() and local_wmb()

IIRC read_barrier_depends() is a nop on everything except alpha.
Maybe add the default if it isn't defined by the MD file?

	David