block: remove dead elevator code

This removes a bunch of core and elevator related code. On the core
front, we remove anything related to queue running, draining,
initialization, plugging, and congestions. We also kill anything
related to request allocation, merging, retrieval, and completion.

Remove any checking for single queue IO schedulers, as they no
longer exist. This means we can also delete a bunch of code related
to request issue, adding, completion, etc - and all the SQ related
ops and helpers.

Also kill the load_default_modules(), as all that did was provide
for a way to load the default single queue elevator.

Tested-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 0 insertions, 5 deletions

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 6b5ad275ed56..c068c30b0c35 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -862,13 +862,8 @@ struct request *attempt_front_merge(struct request_queue *q, struct request *rq)
 int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
 			  struct request *next)
 {
-	struct elevator_queue *e = q->elevator;
 	struct request *free;
 
-	if (!e->uses_mq && e->type->ops.sq.elevator_allow_rq_merge_fn)
-		if (!e->type->ops.sq.elevator_allow_rq_merge_fn(q, rq, next))
-			return 0;
-
 	free = attempt_merge(q, rq, next);
 	if (free) {
 		__blk_put_request(q, free);