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, 6 insertions, 27 deletions

diff --git a/block/blk-ioc.c b/block/blk-ioc.c
index 01580f88fcb3..391128456aec 100644
--- a/block/blk-ioc.c
+++ b/block/blk-ioc.c
@@ -48,10 +48,8 @@ static void ioc_exit_icq(struct io_cq *icq)
 	if (icq->flags & ICQ_EXITED)
 		return;
 
-	if (et->uses_mq && et->ops.mq.exit_icq)
+	if (et->ops.mq.exit_icq)
 		et->ops.mq.exit_icq(icq);
-	else if (!et->uses_mq && et->ops.sq.elevator_exit_icq_fn)
-		et->ops.sq.elevator_exit_icq_fn(icq);
 
 	icq->flags |= ICQ_EXITED;
 }
@@ -187,25 +185,13 @@ void put_io_context_active(struct io_context *ioc)
 	 * reverse double locking.  Read comment in ioc_release_fn() for
 	 * explanation on the nested locking annotation.
 	 */
-retry:
 	spin_lock_irqsave_nested(&ioc->lock, flags, 1);
 	hlist_for_each_entry(icq, &ioc->icq_list, ioc_node) {
 		if (icq->flags & ICQ_EXITED)
 			continue;
 
 		et = icq->q->elevator->type;
-		if (et->uses_mq) {
-			ioc_exit_icq(icq);
-		} else {
-			if (spin_trylock(icq->q->queue_lock)) {
-				ioc_exit_icq(icq);
-				spin_unlock(icq->q->queue_lock);
-			} else {
-				spin_unlock_irqrestore(&ioc->lock, flags);
-				cpu_relax();
-				goto retry;
-			}
-		}
+		ioc_exit_icq(icq);
 	}
 	spin_unlock_irqrestore(&ioc->lock, flags);
 
@@ -232,7 +218,7 @@ static void __ioc_clear_queue(struct list_head *icq_list)
 
 	while (!list_empty(icq_list)) {
 		struct io_cq *icq = list_entry(icq_list->next,
-					       struct io_cq, q_node);
+						struct io_cq, q_node);
 		struct io_context *ioc = icq->ioc;
 
 		spin_lock_irqsave(&ioc->lock, flags);
@@ -253,14 +239,9 @@ void ioc_clear_queue(struct request_queue *q)
 
 	spin_lock_irq(q->queue_lock);
 	list_splice_init(&q->icq_list, &icq_list);
+	spin_unlock_irq(q->queue_lock);
 
-	if (q->mq_ops) {
-		spin_unlock_irq(q->queue_lock);
-		__ioc_clear_queue(&icq_list);
-	} else {
-		__ioc_clear_queue(&icq_list);
-		spin_unlock_irq(q->queue_lock);
-	}
+	__ioc_clear_queue(&icq_list);
 }
 
 int create_task_io_context(struct task_struct *task, gfp_t gfp_flags, int node)
@@ -415,10 +396,8 @@ struct io_cq *ioc_create_icq(struct io_context *ioc, struct request_queue *q,
 	if (likely(!radix_tree_insert(&ioc->icq_tree, q->id, icq))) {
 		hlist_add_head(&icq->ioc_node, &ioc->icq_list);
 		list_add(&icq->q_node, &q->icq_list);
-		if (et->uses_mq && et->ops.mq.init_icq)
+		if (et->ops.mq.init_icq)
 			et->ops.mq.init_icq(icq);
-		else if (!et->uses_mq && et->ops.sq.elevator_init_icq_fn)
-			et->ops.sq.elevator_init_icq_fn(icq);
 	} else {
 		kmem_cache_free(et->icq_cache, icq);
 		icq = ioc_lookup_icq(ioc, q);