rds: Use RCU for the bind lookup searches

The RDS bind lookups are somewhat expensive in terms of CPU
time and locking overhead.  This commit changes them into a
faster RCU based hash tree instead of the rbtrees they were using
before.

On large NUMA systems it is a significant improvement.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

net/rds/ib_rdma.c

diff --git a/net/rds/ib_rdma.c b/net/rds/ib_rdma.c
index cc341cd7..4ba01b9 100644
--- a/net/rds/ib_rdma.c
+++ b/net/rds/ib_rdma.c
@@ -303,6 +303,8 @@
 		goto out_no_cigar;
 	}
 
+	memset(ibmr, 0, sizeof(*ibmr));
+
 	ibmr->fmr = ib_alloc_fmr(rds_ibdev->pd,
 			(IB_ACCESS_LOCAL_WRITE |
 			 IB_ACCESS_REMOTE_READ |