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>
diff --git a/net/rds/rds.h b/net/rds/rds.h
index b2d17f0..fd0bccb 100644
--- a/net/rds/rds.h
+++ b/net/rds/rds.h
@@ -688,6 +688,7 @@
 #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)