diff --git a/include/linux/blktrace_api.h b/include/linux/blktrace_api.h
index 11484f1d19a1..e17d04abf6a3 100644
--- a/include/linux/blktrace_api.h
+++ b/include/linux/blktrace_api.h
@@ -119,7 +119,7 @@ struct compat_blk_user_trace_setup {
 
 #endif
 
-extern void blk_fill_rwbs(char *rwbs, unsigned int op);
+void blk_fill_rwbs(char *rwbs, unsigned int op);
 
 static inline sector_t blk_rq_trace_sector(struct request *rq)
 {
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 8a2591c7aa41..d7ebef83771c 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -1867,6 +1867,16 @@ void blk_trace_remove_sysfs(struct device *dev)
 
 #ifdef CONFIG_EVENT_TRACING
 
+/**
+ * blk_fill_rwbs - Fill the buffer rwbs by mapping op to character string.
+ * @rwbs	buffer to be filled
+ * @op:		REQ_OP_XXX for the tracepoint
+ *
+ * Description:
+ *     Maps the REQ_OP_XXX to character and fills the buffer provided by the
+ *     caller with resulting string.
+ *
+ **/
 void blk_fill_rwbs(char *rwbs, unsigned int op)
 {
 	int i = 0;