[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 (file)
--- a/Documentation/block/biodoc.txt
+++ b/Documentation/block/biodoc.txt
@@ -946,6 +946,13 @@ elevator_merged_fn         called when a request in the scheduler has been
                                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