From b8ab956c544e51a8d19ea3f38b54355d6aa92c33 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Tue, 4 Nov 2014 12:52:41 +0100 Subject: [PATCH] block: Expand a bit documentation about elevator_allow_merge_fn Explain that two requests can be merged without elevator_allow_merge_fn() being called. Signed-off-by: Jan Kara Signed-off-by: Jens Axboe --- Documentation/block/biodoc.txt | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/Documentation/block/biodoc.txt b/Documentation/block/biodoc.txt index 2101e718670d..f1323c6b7ed2 100644 --- a/Documentation/block/biodoc.txt +++ b/Documentation/block/biodoc.txt @@ -946,7 +946,11 @@ elevator_allow_merge_fn called whenever the block layer determines 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. + this hook allows it to do that. Note however + that two *requests* can still be merged at later + time. Currently the io scheduler has no way to + prevent that. It can only learn about the fact + from elevator_merge_req_fn callback. elevator_dispatch_fn* fills the dispatch queue with ready requests. I/O schedulers are free to postpone requests by -- 2.20.1