This patch append more detail explanation to the Documentation of API of I/O scheduler.
Thank you for reading.
---
diff --git a/Documentation/block/biodoc.txt b/Documentation/block/biodoc.txt
index 8d2158a..7c04f54 100644
--- a/Documentation/block/biodoc.txt
+++ b/Documentation/block/biodoc.txt
@@ -935,7 +935,12 @@ keeping work.
4.1. I/O scheduler API
The functions an elevator may implement are: (* are mandatory)
-elevator_merge_fn called to query requests for merge with a bio
+elevator_merge_fn called to query requests for merge with a bio. This method
+ have two following works. One is to indicate how to merge request
+ with bio from head or tail. This function doesn't merge them actually,
+ but just indicate direction for merging from head or tail, or that
+ there is no request with that bio can merge. Another work is to get
+ the request object which is merged, if the bio can do.
elevator_merge_req_fn called when two requests get merged. the one
which gets merged into the other one will be