[PATCH] block: document io scheduler allow_merge_fn hook
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/Documentation/block/biodoc.txt b/Documentation/block/biodoc.txt
index c6c9a9c..3adaace 100644
--- a/Documentation/block/biodoc.txt
+++ b/Documentation/block/biodoc.txt
@@ -946,6 +946,13 @@
scheduler for example, to reposition the request
if its sorting order has changed.
+elevator_allow_merge_fn called whenever the block layer determines
+ that a bio can be merged into an existing
+ request safely. The io scheduler may still
+ want to stop a merge at this point if it
+ results in some sort of conflict internally,
+ this hook allows it to do that.
+
elevator_dispatch_fn fills the dispatch queue with ready requests.
I/O schedulers are free to postpone requests by
not filling the dispatch queue unless @force