RDS: add __printf format attribute to error reporting functions

This is helpful to detect at compile-time errors related to format
strings.
Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/rds/ib.h

@@ -333,6 +333,7 @@ void rds_ib_conn_path_shutdown(struct rds_conn_path *cp);
 void rds_ib_state_change(struct sock *sk);
 int rds_ib_listen_init(void);
 void rds_ib_listen_stop(void);
+__printf(2, 3)
 void __rds_ib_conn_error(struct rds_connection *conn, const char *, ...);
 int rds_ib_cm_handle_connect(struct rdma_cm_id *cm_id,
 			     struct rdma_cm_event *event);

net/rds/rds.h

@@ -688,6 +688,7 @@ void __rds_conn_error(struct rds_connection *conn, const char *, ...);
 #define rds_conn_error(conn, fmt...) \
 	__rds_conn_error(conn, KERN_WARNING "RDS: " fmt)
 
+__printf(2, 3)
 void __rds_conn_path_error(struct rds_conn_path *cp, const char *, ...);
 #define rds_conn_path_error(cp, fmt...) \
 	__rds_conn_path_error(cp, KERN_WARNING "RDS: " fmt)