block: Add __attribute__((format(printf...) and fix fallout

Use the compiler to verify format strings and arguments.

Fix fallout.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/include/linux/blktrace_api.h b/include/linux/blktrace_api.h
index b22fb0d..8c7c2de 100644
--- a/include/linux/blktrace_api.h
+++ b/include/linux/blktrace_api.h
@@ -169,7 +169,8 @@
 extern int do_blk_trace_setup(struct request_queue *q, char *name,
 			      dev_t dev, struct block_device *bdev,
 			      struct blk_user_trace_setup *buts);
-extern void __trace_note_message(struct blk_trace *, const char *fmt, ...);
+extern __attribute__((format(printf, 2, 3)))
+void __trace_note_message(struct blk_trace *, const char *fmt, ...);
 
 /**
  * blk_add_trace_msg - Add a (simple) message to the blktrace stream