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| author |   Jan Kara <jack@suse.cz> | 2014-11-04 12:52:41 +0100 |
|---|---|---|
| committer |   Jens Axboe <axboe@fb.com> | 2014-11-04 08:28:15 -0700 |
| commit | b8ab956c544e51a8d19ea3f38b54355d6aa92c33 (patch) | |
| tree | 98cb2d607852e0f69c6b9cddaec479429460c732 /Documentation/block | |
| parent | blk-mq: add BLK_MQ_F_DEFER_ISSUE support flag (diff) | |
| download | linux-dev-b8ab956c544e51a8d19ea3f38b54355d6aa92c33.tar.xz linux-dev-b8ab956c544e51a8d19ea3f38b54355d6aa92c33.zip | |
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 <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'Documentation/block')
| -rw-r--r-- | Documentation/block/biodoc.txt | 6 |
1 files changed, 5 insertions, 1 deletions
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 |