diff --git a/include/linux/jbd.h b/include/linux/jbd.h
index 6384b19efe64..64246dce5663 100644
--- a/include/linux/jbd.h
+++ b/include/linux/jbd.h
@@ -614,6 +614,8 @@ struct transaction_s
  * @j_wbufsize: maximum number of buffer_heads allowed in j_wbuf, the
  *	number that will fit in j_blocksize
  * @j_last_sync_writer: most recent pid which did a synchronous write
+ * @j_average_commit_time: the average amount of time in nanoseconds it
+ *	takes to commit a transaction to the disk.
  * @j_private: An opaque pointer to fs-private information.
  */