RDS: use rb_entry()

To make the code clearer, use rb_entry() instead of container_of() to
deal with rbtree.
Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/rds/rdma.c

@@ -135,7 +135,7 @@ void rds_rdma_drop_keys(struct rds_sock *rs)
 	/* Release any MRs associated with this socket */
 	spin_lock_irqsave(&rs->rs_rdma_lock, flags);
 	while ((node = rb_first(&rs->rs_rdma_keys))) {
-		mr = container_of(node, struct rds_mr, r_rb_node);
+		mr = rb_entry(node, struct rds_mr, r_rb_node);
 		if (mr->r_trans == rs->rs_transport)
 			mr->r_invalidate = 0;
 		rb_erase(&mr->r_rb_node, &rs->rs_rdma_keys);