RDS: break out rdma and data ops into nested structs in rds_message

Clearly separate rdma-related variables in rm from data-related ones.
This is in anticipation of adding atomic support.

Signed-off-by: Andy Grover <andy.grover@oracle.com>
diff --git a/net/rds/rds.h b/net/rds/rds.h
index 1d3eef6..07a750b 100644
--- a/net/rds/rds.h
+++ b/net/rds/rds.h
@@ -259,12 +259,18 @@
 	 */
 	spinlock_t		m_rs_lock;
 	struct rds_sock		*m_rs;
-	struct rds_rdma_op	*m_rdma_op;
 	rds_rdma_cookie_t	m_rdma_cookie;
-	struct rds_mr		*m_rdma_mr;
-	unsigned int		m_nents;
-	unsigned int		m_count;
-	struct scatterlist	m_sg[0];
+	struct {
+		struct {
+			struct rds_rdma_op	*m_rdma_op;
+			struct rds_mr		*m_rdma_mr;
+		} rdma;
+		struct {
+			unsigned int		m_nents;
+			unsigned int		m_count;
+			struct scatterlist	m_sg[0];
+		} data;
+	};
 };
 
 /*