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>

11 files changed, 52 insertions, 2218 deletions

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 3a27d31fcda6..44c7e567aa25 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -5745,7 +5745,6 @@ static struct elevator_type iosched_bfq_mq = {
 		.exit_sched		= bfq_exit_queue,
 	},
 
-	.uses_mq =		true,
 	.icq_size =		sizeof(struct bfq_io_cq),
 	.icq_align =		__alignof__(struct bfq_io_cq),
 	.elevator_attrs =	bfq_attrs,
diff --git a/block/blk-core.c b/block/blk-core.c
index daaed4dfa719..18538a41a532 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -144,46 +144,6 @@ bool blk_queue_flag_test_and_clear(unsigned int flag, struct request_queue *q)
 }
 EXPORT_SYMBOL_GPL(blk_queue_flag_test_and_clear);
 
-static void blk_clear_congested(struct request_list *rl, int sync)
-{
-#ifdef CONFIG_CGROUP_WRITEBACK
-	clear_wb_congested(rl->blkg->wb_congested, sync);
-#else
-	/*
-	 * If !CGROUP_WRITEBACK, all blkg's map to bdi->wb and we shouldn't
-	 * flip its congestion state for events on other blkcgs.
-	 */
-	if (rl == &rl->q->root_rl)
-		clear_wb_congested(rl->q->backing_dev_info->wb.congested, sync);
-#endif
-}
-
-static void blk_set_congested(struct request_list *rl, int sync)
-{
-#ifdef CONFIG_CGROUP_WRITEBACK
-	set_wb_congested(rl->blkg->wb_congested, sync);
-#else
-	/* see blk_clear_congested() */
-	if (rl == &rl->q->root_rl)
-		set_wb_congested(rl->q->backing_dev_info->wb.congested, sync);
-#endif
-}
-
-void blk_queue_congestion_threshold(struct request_queue *q)
-{
-	int nr;
-
-	nr = q->nr_requests - (q->nr_requests / 8) + 1;
-	if (nr > q->nr_requests)
-		nr = q->nr_requests;
-	q->nr_congestion_on = nr;
-
-	nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1;
-	if (nr < 1)
-		nr = 1;
-	q->nr_congestion_off = nr;
-}
-
 void blk_rq_init(struct request_queue *q, struct request *rq)
 {
 	memset(rq, 0, sizeof(*rq));
@@ -292,99 +252,6 @@ void blk_dump_rq_flags(struct request *rq, char *msg)
 }
 EXPORT_SYMBOL(blk_dump_rq_flags);
 
-static void blk_delay_work(struct work_struct *work)
-{
-	struct request_queue *q;
-
-	q = container_of(work, struct request_queue, delay_work.work);
-	spin_lock_irq(q->queue_lock);
-	__blk_run_queue(q);
-	spin_unlock_irq(q->queue_lock);
-}
-
-/**
- * blk_delay_queue - restart queueing after defined interval
- * @q:		The &struct request_queue in question
- * @msecs:	Delay in msecs
- *
- * Description:
- *   Sometimes queueing needs to be postponed for a little while, to allow
- *   resources to come back. This function will make sure that queueing is
- *   restarted around the specified time.
- */
-void blk_delay_queue(struct request_queue *q, unsigned long msecs)
-{
-	lockdep_assert_held(q->queue_lock);
-	WARN_ON_ONCE(q->mq_ops);
-
-	if (likely(!blk_queue_dead(q)))
-		queue_delayed_work(kblockd_workqueue, &q->delay_work,
-				   msecs_to_jiffies(msecs));
-}
-EXPORT_SYMBOL(blk_delay_queue);
-
-/**
- * blk_start_queue_async - asynchronously restart a previously stopped queue
- * @q:    The &struct request_queue in question
- *
- * Description:
- *   blk_start_queue_async() will clear the stop flag on the queue, and
- *   ensure that the request_fn for the queue is run from an async
- *   context.
- **/
-void blk_start_queue_async(struct request_queue *q)
-{
-	lockdep_assert_held(q->queue_lock);
-	WARN_ON_ONCE(q->mq_ops);
-
-	queue_flag_clear(QUEUE_FLAG_STOPPED, q);
-	blk_run_queue_async(q);
-}
-EXPORT_SYMBOL(blk_start_queue_async);
-
-/**
- * blk_start_queue - restart a previously stopped queue
- * @q:    The &struct request_queue in question
- *
- * Description:
- *   blk_start_queue() will clear the stop flag on the queue, and call
- *   the request_fn for the queue if it was in a stopped state when
- *   entered. Also see blk_stop_queue().
- **/
-void blk_start_queue(struct request_queue *q)
-{
-	lockdep_assert_held(q->queue_lock);
-	WARN_ON_ONCE(q->mq_ops);
-
-	queue_flag_clear(QUEUE_FLAG_STOPPED, q);
-	__blk_run_queue(q);
-}
-EXPORT_SYMBOL(blk_start_queue);
-
-/**
- * blk_stop_queue - stop a queue
- * @q:    The &struct request_queue in question
- *
- * Description:
- *   The Linux block layer assumes that a block driver will consume all
- *   entries on the request queue when the request_fn strategy is called.
- *   Often this will not happen, because of hardware limitations (queue
- *   depth settings). If a device driver gets a 'queue full' response,
- *   or if it simply chooses not to queue more I/O at one point, it can
- *   call this function to prevent the request_fn from being called until
- *   the driver has signalled it's ready to go again. This happens by calling
- *   blk_start_queue() to restart queue operations.
- **/
-void blk_stop_queue(struct request_queue *q)
-{
-	lockdep_assert_held(q->queue_lock);
-	WARN_ON_ONCE(q->mq_ops);
-
-	cancel_delayed_work(&q->delay_work);
-	queue_flag_set(QUEUE_FLAG_STOPPED, q);
-}
-EXPORT_SYMBOL(blk_stop_queue);
-
 /**
  * blk_sync_queue - cancel any pending callbacks on a queue
  * @q: the queue
@@ -415,8 +282,6 @@ void blk_sync_queue(struct request_queue *q)
 		cancel_delayed_work_sync(&q->requeue_work);
 		queue_for_each_hw_ctx(q, hctx, i)
 			cancel_delayed_work_sync(&hctx->run_work);
-	} else {
-		cancel_delayed_work_sync(&q->delay_work);
 	}
 }
 EXPORT_SYMBOL(blk_sync_queue);
@@ -442,250 +307,12 @@ void blk_clear_pm_only(struct request_queue *q)
 }
 EXPORT_SYMBOL_GPL(blk_clear_pm_only);
 
-/**
- * __blk_run_queue_uncond - run a queue whether or not it has been stopped
- * @q:	The queue to run
- *
- * Description:
- *    Invoke request handling on a queue if there are any pending requests.
- *    May be used to restart request handling after a request has completed.
- *    This variant runs the queue whether or not the queue has been
- *    stopped. Must be called with the queue lock held and interrupts
- *    disabled. See also @blk_run_queue.
- */
-inline void __blk_run_queue_uncond(struct request_queue *q)
-{
-	lockdep_assert_held(q->queue_lock);
-	WARN_ON_ONCE(q->mq_ops);
-
-	if (unlikely(blk_queue_dead(q)))
-		return;
-
-	/*
-	 * Some request_fn implementations, e.g. scsi_request_fn(), unlock
-	 * the queue lock internally. As a result multiple threads may be
-	 * running such a request function concurrently. Keep track of the
-	 * number of active request_fn invocations such that blk_drain_queue()
-	 * can wait until all these request_fn calls have finished.
-	 */
-	q->request_fn_active++;
-	q->request_fn(q);
-	q->request_fn_active--;
-}
-EXPORT_SYMBOL_GPL(__blk_run_queue_uncond);
-
-/**
- * __blk_run_queue - run a single device queue
- * @q:	The queue to run
- *
- * Description:
- *    See @blk_run_queue.
- */
-void __blk_run_queue(struct request_queue *q)
-{
-	lockdep_assert_held(q->queue_lock);
-	WARN_ON_ONCE(q->mq_ops);
-
-	if (unlikely(blk_queue_stopped(q)))
-		return;
-
-	__blk_run_queue_uncond(q);
-}
-EXPORT_SYMBOL(__blk_run_queue);
-
-/**
- * blk_run_queue_async - run a single device queue in workqueue context
- * @q:	The queue to run
- *
- * Description:
- *    Tells kblockd to perform the equivalent of @blk_run_queue on behalf
- *    of us.
- *
- * Note:
- *    Since it is not allowed to run q->delay_work after blk_cleanup_queue()
- *    has canceled q->delay_work, callers must hold the queue lock to avoid
- *    race conditions between blk_cleanup_queue() and blk_run_queue_async().
- */
-void blk_run_queue_async(struct request_queue *q)
-{
-	lockdep_assert_held(q->queue_lock);
-	WARN_ON_ONCE(q->mq_ops);
-
-	if (likely(!blk_queue_stopped(q) && !blk_queue_dead(q)))
-		mod_delayed_work(kblockd_workqueue, &q->delay_work, 0);
-}
-EXPORT_SYMBOL(blk_run_queue_async);
-
-/**
- * blk_run_queue - run a single device queue
- * @q: The queue to run
- *
- * Description:
- *    Invoke request handling on this queue, if it has pending work to do.
- *    May be used to restart queueing when a request has completed.
- */
-void blk_run_queue(struct request_queue *q)
-{
-	unsigned long flags;
-
-	WARN_ON_ONCE(q->mq_ops);
-
-	spin_lock_irqsave(q->queue_lock, flags);
-	__blk_run_queue(q);
-	spin_unlock_irqrestore(q->queue_lock, flags);
-}
-EXPORT_SYMBOL(blk_run_queue);
-
 void blk_put_queue(struct request_queue *q)
 {
 	kobject_put(&q->kobj);
 }
 EXPORT_SYMBOL(blk_put_queue);
 
-/**
- * __blk_drain_queue - drain requests from request_queue
- * @q: queue to drain
- * @drain_all: whether to drain all requests or only the ones w/ ELVPRIV
- *
- * Drain requests from @q.  If @drain_all is set, all requests are drained.
- * If not, only ELVPRIV requests are drained.  The caller is responsible
- * for ensuring that no new requests which need to be drained are queued.
- */
-static void __blk_drain_queue(struct request_queue *q, bool drain_all)
-	__releases(q->queue_lock)
-	__acquires(q->queue_lock)
-{
-	int i;
-
-	lockdep_assert_held(q->queue_lock);
-	WARN_ON_ONCE(q->mq_ops);
-
-	while (true) {
-		bool drain = false;
-
-		/*
-		 * The caller might be trying to drain @q before its
-		 * elevator is initialized.
-		 */
-		if (q->elevator)
-			elv_drain_elevator(q);
-
-		blkcg_drain_queue(q);
-
-		/*
-		 * This function might be called on a queue which failed
-		 * driver init after queue creation or is not yet fully
-		 * active yet.  Some drivers (e.g. fd and loop) get unhappy
-		 * in such cases.  Kick queue iff dispatch queue has
-		 * something on it and @q has request_fn set.
-		 */
-		if (!list_empty(&q->queue_head) && q->request_fn)
-			__blk_run_queue(q);
-
-		drain |= q->nr_rqs_elvpriv;
-		drain |= q->request_fn_active;
-
-		/*
-		 * Unfortunately, requests are queued at and tracked from
-		 * multiple places and there's no single counter which can
-		 * be drained.  Check all the queues and counters.
-		 */
-		if (drain_all) {
-			struct blk_flush_queue *fq = blk_get_flush_queue(q, NULL);
-			drain |= !list_empty(&q->queue_head);
-			for (i = 0; i < 2; i++) {
-				drain |= q->nr_rqs[i];
-				drain |= q->in_flight[i];
-				if (fq)
-				    drain |= !list_empty(&fq->flush_queue[i]);
-			}
-		}
-
-		if (!drain)
-			break;
-
-		spin_unlock_irq(q->queue_lock);
-
-		msleep(10);
-
-		spin_lock_irq(q->queue_lock);
-	}
-
-	/*
-	 * With queue marked dead, any woken up waiter will fail the
-	 * allocation path, so the wakeup chaining is lost and we're
-	 * left with hung waiters. We need to wake up those waiters.
-	 */
-	if (q->request_fn) {
-		struct request_list *rl;
-
-		blk_queue_for_each_rl(rl, q)
-			for (i = 0; i < ARRAY_SIZE(rl->wait); i++)
-				wake_up_all(&rl->wait[i]);
-	}
-}
-
-void blk_drain_queue(struct request_queue *q)
-{
-	spin_lock_irq(q->queue_lock);
-	__blk_drain_queue(q, true);
-	spin_unlock_irq(q->queue_lock);
-}
-
-/**
- * blk_queue_bypass_start - enter queue bypass mode
- * @q: queue of interest
- *
- * In bypass mode, only the dispatch FIFO queue of @q is used.  This
- * function makes @q enter bypass mode and drains all requests which were
- * throttled or issued before.  On return, it's guaranteed that no request
- * is being throttled or has ELVPRIV set and blk_queue_bypass() %true
- * inside queue or RCU read lock.
- */
-void blk_queue_bypass_start(struct request_queue *q)
-{
-	WARN_ON_ONCE(q->mq_ops);
-
-	spin_lock_irq(q->queue_lock);
-	q->bypass_depth++;
-	queue_flag_set(QUEUE_FLAG_BYPASS, q);
-	spin_unlock_irq(q->queue_lock);
-
-	/*
-	 * Queues start drained.  Skip actual draining till init is
-	 * complete.  This avoids lenghty delays during queue init which
-	 * can happen many times during boot.
-	 */
-	if (blk_queue_init_done(q)) {
-		spin_lock_irq(q->queue_lock);
-		__blk_drain_queue(q, false);
-		spin_unlock_irq(q->queue_lock);
-
-		/* ensure blk_queue_bypass() is %true inside RCU read lock */
-		synchronize_rcu();
-	}
-}
-EXPORT_SYMBOL_GPL(blk_queue_bypass_start);
-
-/**
- * blk_queue_bypass_end - leave queue bypass mode
- * @q: queue of interest
- *
- * Leave bypass mode and restore the normal queueing behavior.
- *
- * Note: although blk_queue_bypass_start() is only called for blk-sq queues,
- * this function is called for both blk-sq and blk-mq queues.
- */
-void blk_queue_bypass_end(struct request_queue *q)
-{
-	spin_lock_irq(q->queue_lock);
-	if (!--q->bypass_depth)
-		queue_flag_clear(QUEUE_FLAG_BYPASS, q);
-	WARN_ON_ONCE(q->bypass_depth < 0);
-	spin_unlock_irq(q->queue_lock);
-}
-EXPORT_SYMBOL_GPL(blk_queue_bypass_end);
-
 void blk_set_queue_dying(struct request_queue *q)
 {
 	blk_queue_flag_set(QUEUE_FLAG_DYING, q);
@@ -699,18 +326,6 @@ void blk_set_queue_dying(struct request_queue *q)
 
 	if (q->mq_ops)
 		blk_mq_wake_waiters(q);
-	else {
-		struct request_list *rl;
-
-		spin_lock_irq(q->queue_lock);
-		blk_queue_for_each_rl(rl, q) {
-			if (rl->rq_pool) {
-				wake_up_all(&rl->wait[BLK_RW_SYNC]);
-				wake_up_all(&rl->wait[BLK_RW_ASYNC]);
-			}
-		}
-		spin_unlock_irq(q->queue_lock);
-	}
 
 	/* Make blk_queue_enter() reexamine the DYING flag. */
 	wake_up_all(&q->mq_freeze_wq);
@@ -822,6 +437,7 @@ void blk_cleanup_queue(struct request_queue *q)
 
 	if (q->mq_ops)
 		blk_mq_free_queue(q);
+
 	percpu_ref_exit(&q->q_usage_counter);
 
 	spin_lock_irq(lock);
@@ -1013,8 +629,6 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id,
 
 	INIT_LIST_HEAD(&q->queue_head);
 	q->last_merge = NULL;
-	q->end_sector = 0;
-	q->boundary_rq = NULL;
 
 	q->id = ida_simple_get(&blk_queue_ida, 0, 0, gfp_mask);
 	if (q->id < 0)
@@ -1047,7 +661,6 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id,
 #ifdef CONFIG_BLK_CGROUP
 	INIT_LIST_HEAD(&q->blkg_list);
 #endif
-	INIT_DELAYED_WORK(&q->delay_work, blk_delay_work);
 
 	kobject_init(&q->kobj, &blk_queue_ktype);
 
@@ -1100,105 +713,6 @@ fail_q:
 }
 EXPORT_SYMBOL(blk_alloc_queue_node);
 
-/**
- * blk_init_queue  - prepare a request queue for use with a block device
- * @rfn:  The function to be called to process requests that have been
- *        placed on the queue.
- * @lock: Request queue spin lock
- *
- * Description:
- *    If a block device wishes to use the standard request handling procedures,
- *    which sorts requests and coalesces adjacent requests, then it must
- *    call blk_init_queue().  The function @rfn will be called when there
- *    are requests on the queue that need to be processed.  If the device
- *    supports plugging, then @rfn may not be called immediately when requests
- *    are available on the queue, but may be called at some time later instead.
- *    Plugged queues are generally unplugged when a buffer belonging to one
- *    of the requests on the queue is needed, or due to memory pressure.
- *
- *    @rfn is not required, or even expected, to remove all requests off the
- *    queue, but only as many as it can handle at a time.  If it does leave
- *    requests on the queue, it is responsible for arranging that the requests
- *    get dealt with eventually.
- *
- *    The queue spin lock must be held while manipulating the requests on the
- *    request queue; this lock will be taken also from interrupt context, so irq
- *    disabling is needed for it.
- *
- *    Function returns a pointer to the initialized request queue, or %NULL if
- *    it didn't succeed.
- *
- * Note:
- *    blk_init_queue() must be paired with a blk_cleanup_queue() call
- *    when the block device is deactivated (such as at module unload).
- **/
-
-struct request_queue *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
-{
-	return blk_init_queue_node(rfn, lock, NUMA_NO_NODE);
-}
-EXPORT_SYMBOL(blk_init_queue);
-
-struct request_queue *
-blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
-{
-	struct request_queue *q;
-
-	q = blk_alloc_queue_node(GFP_KERNEL, node_id, lock);
-	if (!q)
-		return NULL;
-
-	q->request_fn = rfn;
-	if (blk_init_allocated_queue(q) < 0) {
-		blk_cleanup_queue(q);
-		return NULL;
-	}
-
-	return q;
-}
-EXPORT_SYMBOL(blk_init_queue_node);
-
-static blk_qc_t blk_queue_bio(struct request_queue *q, struct bio *bio);
-
-
-int blk_init_allocated_queue(struct request_queue *q)
-{
-	WARN_ON_ONCE(q->mq_ops);
-
-	q->fq = blk_alloc_flush_queue(q, NUMA_NO_NODE, q->cmd_size, GFP_KERNEL);
-	if (!q->fq)
-		return -ENOMEM;
-
-	if (q->init_rq_fn && q->init_rq_fn(q, q->fq->flush_rq, GFP_KERNEL))
-		goto out_free_flush_queue;
-
-	if (blk_init_rl(&q->root_rl, q, GFP_KERNEL))
-		goto out_exit_flush_rq;
-
-	INIT_WORK(&q->timeout_work, blk_timeout_work);
-	q->queue_flags		|= QUEUE_FLAG_DEFAULT;
-
-	/*
-	 * This also sets hw/phys segments, boundary and size
-	 */
-	blk_queue_make_request(q, blk_queue_bio);
-
-	q->sg_reserved_size = INT_MAX;
-
-	if (elevator_init(q))
-		goto out_exit_flush_rq;
-	return 0;
-
-out_exit_flush_rq:
-	if (q->exit_rq_fn)
-		q->exit_rq_fn(q, q->fq->flush_rq);
-out_free_flush_queue:
-	blk_free_flush_queue(q->fq);
-	q->fq = NULL;
-	return -ENOMEM;
-}
-EXPORT_SYMBOL(blk_init_allocated_queue);
-
 bool blk_get_queue(struct request_queue *q)
 {
 	if (likely(!blk_queue_dying(q))) {
@@ -1210,406 +724,6 @@ bool blk_get_queue(struct request_queue *q)
 }
 EXPORT_SYMBOL(blk_get_queue);
 
-static inline void blk_free_request(struct request_list *rl, struct request *rq)
-{
-	if (rq->rq_flags & RQF_ELVPRIV) {
-		elv_put_request(rl->q, rq);
-		if (rq->elv.icq)
-			put_io_context(rq->elv.icq->ioc);
-	}
-
-	mempool_free(rq, rl->rq_pool);
-}
-
-/*
- * ioc_batching returns true if the ioc is a valid batching request and
- * should be given priority access to a request.
- */
-static inline int ioc_batching(struct request_queue *q, struct io_context *ioc)
-{
-	if (!ioc)
-		return 0;
-
-	/*
-	 * Make sure the process is able to allocate at least 1 request
-	 * even if the batch times out, otherwise we could theoretically
-	 * lose wakeups.
-	 */
-	return ioc->nr_batch_requests == q->nr_batching ||
-		(ioc->nr_batch_requests > 0
-		&& time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
-}
-
-/*
- * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
- * will cause the process to be a "batcher" on all queues in the system. This
- * is the behaviour we want though - once it gets a wakeup it should be given
- * a nice run.
- */
-static void ioc_set_batching(struct request_queue *q, struct io_context *ioc)
-{
-	if (!ioc || ioc_batching(q, ioc))
-		return;
-
-	ioc->nr_batch_requests = q->nr_batching;
-	ioc->last_waited = jiffies;
-}
-
-static void __freed_request(struct request_list *rl, int sync)
-{
-	struct request_queue *q = rl->q;
-
-	if (rl->count[sync] < queue_congestion_off_threshold(q))
-		blk_clear_congested(rl, sync);
-
-	if (rl->count[sync] + 1 <= q->nr_requests) {
-		if (waitqueue_active(&rl->wait[sync]))
-			wake_up(&rl->wait[sync]);
-
-		blk_clear_rl_full(rl, sync);
-	}
-}
-
-/*
- * A request has just been released.  Account for it, update the full and
- * congestion status, wake up any waiters.   Called under q->queue_lock.
- */
-static void freed_request(struct request_list *rl, bool sync,
-		req_flags_t rq_flags)
-{
-	struct request_queue *q = rl->q;
-
-	q->nr_rqs[sync]--;
-	rl->count[sync]--;
-	if (rq_flags & RQF_ELVPRIV)
-		q->nr_rqs_elvpriv--;
-
-	__freed_request(rl, sync);
-
-	if (unlikely(rl->starved[sync ^ 1]))
-		__freed_request(rl, sync ^ 1);
-}
-
-int blk_update_nr_requests(struct request_queue *q, unsigned int nr)
-{
-	struct request_list *rl;
-	int on_thresh, off_thresh;
-
-	WARN_ON_ONCE(q->mq_ops);
-
-	spin_lock_irq(q->queue_lock);
-	q->nr_requests = nr;
-	blk_queue_congestion_threshold(q);
-	on_thresh = queue_congestion_on_threshold(q);
-	off_thresh = queue_congestion_off_threshold(q);
-
-	blk_queue_for_each_rl(rl, q) {
-		if (rl->count[BLK_RW_SYNC] >= on_thresh)
-			blk_set_congested(rl, BLK_RW_SYNC);
-		else if (rl->count[BLK_RW_SYNC] < off_thresh)
-			blk_clear_congested(rl, BLK_RW_SYNC);
-
-		if (rl->count[BLK_RW_ASYNC] >= on_thresh)
-			blk_set_congested(rl, BLK_RW_ASYNC);
-		else if (rl->count[BLK_RW_ASYNC] < off_thresh)
-			blk_clear_congested(rl, BLK_RW_ASYNC);
-
-		if (rl->count[BLK_RW_SYNC] >= q->nr_requests) {
-			blk_set_rl_full(rl, BLK_RW_SYNC);
-		} else {
-			blk_clear_rl_full(rl, BLK_RW_SYNC);
-			wake_up(&rl->wait[BLK_RW_SYNC]);
-		}
-
-		if (rl->count[BLK_RW_ASYNC] >= q->nr_requests) {
-			blk_set_rl_full(rl, BLK_RW_ASYNC);
-		} else {
-			blk_clear_rl_full(rl, BLK_RW_ASYNC);
-			wake_up(&rl->wait[BLK_RW_ASYNC]);
-		}
-	}
-
-	spin_unlock_irq(q->queue_lock);
-	return 0;
-}
-
-/**
- * __get_request - get a free request
- * @rl: request list to allocate from
- * @op: operation and flags
- * @bio: bio to allocate request for (can be %NULL)
- * @flags: BLQ_MQ_REQ_* flags
- * @gfp_mask: allocator flags
- *
- * Get a free request from @q.  This function may fail under memory
- * pressure or if @q is dead.
- *
- * Must be called with @q->queue_lock held and,
- * Returns ERR_PTR on failure, with @q->queue_lock held.
- * Returns request pointer on success, with @q->queue_lock *not held*.
- */
-static struct request *__get_request(struct request_list *rl, unsigned int op,
-		struct bio *bio, blk_mq_req_flags_t flags, gfp_t gfp_mask)
-{
-	struct request_queue *q = rl->q;
-	struct request *rq;
-	struct elevator_type *et = q->elevator->type;
-	struct io_context *ioc = rq_ioc(bio);
-	struct io_cq *icq = NULL;
-	const bool is_sync = op_is_sync(op);
-	int may_queue;
-	req_flags_t rq_flags = RQF_ALLOCED;
-
-	lockdep_assert_held(q->queue_lock);
-
-	if (unlikely(blk_queue_dying(q)))
-		return ERR_PTR(-ENODEV);
-
-	may_queue = elv_may_queue(q, op);
-	if (may_queue == ELV_MQUEUE_NO)
-		goto rq_starved;
-
-	if (rl->count[is_sync]+1 >= queue_congestion_on_threshold(q)) {
-		if (rl->count[is_sync]+1 >= q->nr_requests) {
-			/*
-			 * The queue will fill after this allocation, so set
-			 * it as full, and mark this process as "batching".
-			 * This process will be allowed to complete a batch of
-			 * requests, others will be blocked.
-			 */
-			if (!blk_rl_full(rl, is_sync)) {
-				ioc_set_batching(q, ioc);
-				blk_set_rl_full(rl, is_sync);
-			} else {
-				if (may_queue != ELV_MQUEUE_MUST
-						&& !ioc_batching(q, ioc)) {
-					/*
-					 * The queue is full and the allocating
-					 * process is not a "batcher", and not
-					 * exempted by the IO scheduler
-					 */
-					return ERR_PTR(-ENOMEM);
-				}
-			}
-		}
-		blk_set_congested(rl, is_sync);
-	}
-
-	/*
-	 * Only allow batching queuers to allocate up to 50% over the defined
-	 * limit of requests, otherwise we could have thousands of requests
-	 * allocated with any setting of ->nr_requests
-	 */
-	if (rl->count[is_sync] >= (3 * q->nr_requests / 2))
-		return ERR_PTR(-ENOMEM);
-
-	q->nr_rqs[is_sync]++;
-	rl->count[is_sync]++;
-	rl->starved[is_sync] = 0;
-
-	/*
-	 * Decide whether the new request will be managed by elevator.  If
-	 * so, mark @rq_flags and increment elvpriv.  Non-zero elvpriv will
-	 * prevent the current elevator from being destroyed until the new
-	 * request is freed.  This guarantees icq's won't be destroyed and
-	 * makes creating new ones safe.
-	 *
-	 * Flush requests do not use the elevator so skip initialization.
-	 * This allows a request to share the flush and elevator data.
-	 *
-	 * Also, lookup icq while holding queue_lock.  If it doesn't exist,
-	 * it will be created after releasing queue_lock.
-	 */
-	if (!op_is_flush(op) && !blk_queue_bypass(q)) {
-		rq_flags |= RQF_ELVPRIV;
-		q->nr_rqs_elvpriv++;
-		if (et->icq_cache && ioc)
-			icq = ioc_lookup_icq(ioc, q);
-	}
-
-	if (blk_queue_io_stat(q))
-		rq_flags |= RQF_IO_STAT;
-	spin_unlock_irq(q->queue_lock);
-
-	/* allocate and init request */
-	rq = mempool_alloc(rl->rq_pool, gfp_mask);
-	if (!rq)
-		goto fail_alloc;
-
-	blk_rq_init(q, rq);
-	blk_rq_set_rl(rq, rl);
-	rq->cmd_flags = op;
-	rq->rq_flags = rq_flags;
-	if (flags & BLK_MQ_REQ_PREEMPT)
-		rq->rq_flags |= RQF_PREEMPT;
-
-	/* init elvpriv */
-	if (rq_flags & RQF_ELVPRIV) {
-		if (unlikely(et->icq_cache && !icq)) {
-			if (ioc)
-				icq = ioc_create_icq(ioc, q, gfp_mask);
-			if (!icq)
-				goto fail_elvpriv;
-		}
-
-		rq->elv.icq = icq;
-		if (unlikely(elv_set_request(q, rq, bio, gfp_mask)))
-			goto fail_elvpriv;
-
-		/* @rq->elv.icq holds io_context until @rq is freed */
-		if (icq)
-			get_io_context(icq->ioc);
-	}
-out:
-	/*
-	 * ioc may be NULL here, and ioc_batching will be false. That's
-	 * OK, if the queue is under the request limit then requests need
-	 * not count toward the nr_batch_requests limit. There will always
-	 * be some limit enforced by BLK_BATCH_TIME.
-	 */
-	if (ioc_batching(q, ioc))
-		ioc->nr_batch_requests--;
-
-	trace_block_getrq(q, bio, op);
-	return rq;
-
-fail_elvpriv:
-	/*
-	 * elvpriv init failed.  ioc, icq and elvpriv aren't mempool backed
-	 * and may fail indefinitely under memory pressure and thus
-	 * shouldn't stall IO.  Treat this request as !elvpriv.  This will
-	 * disturb iosched and blkcg but weird is bettern than dead.
-	 */
-	printk_ratelimited(KERN_WARNING "%s: dev %s: request aux data allocation failed, iosched may be disturbed\n",
-			   __func__, dev_name(q->backing_dev_info->dev));
-
-	rq->rq_flags &= ~RQF_ELVPRIV;
-	rq->elv.icq = NULL;
-
-	spin_lock_irq(q->queue_lock);
-	q->nr_rqs_elvpriv--;
-	spin_unlock_irq(q->queue_lock);
-	goto out;
-
-fail_alloc:
-	/*
-	 * Allocation failed presumably due to memory. Undo anything we
-	 * might have messed up.
-	 *
-	 * Allocating task should really be put onto the front of the wait
-	 * queue, but this is pretty rare.
-	 */
-	spin_lock_irq(q->queue_lock);
-	freed_request(rl, is_sync, rq_flags);
-
-	/*
-	 * in the very unlikely event that allocation failed and no
-	 * requests for this direction was pending, mark us starved so that
-	 * freeing of a request in the other direction will notice
-	 * us. another possible fix would be to split the rq mempool into
-	 * READ and WRITE
-	 */
-rq_starved:
-	if (unlikely(rl->count[is_sync] == 0))
-		rl->starved[is_sync] = 1;
-	return ERR_PTR(-ENOMEM);
-}
-
-/**
- * get_request - get a free request
- * @q: request_queue to allocate request from
- * @op: operation and flags
- * @bio: bio to allocate request for (can be %NULL)
- * @flags: BLK_MQ_REQ_* flags.
- * @gfp: allocator flags
- *
- * Get a free request from @q.  If %BLK_MQ_REQ_NOWAIT is set in @flags,
- * this function keeps retrying under memory pressure and fails iff @q is dead.
- *
- * Must be called with @q->queue_lock held and,
- * Returns ERR_PTR on failure, with @q->queue_lock held.
- * Returns request pointer on success, with @q->queue_lock *not held*.
- */
-static struct request *get_request(struct request_queue *q, unsigned int op,
-		struct bio *bio, blk_mq_req_flags_t flags, gfp_t gfp)
-{
-	const bool is_sync = op_is_sync(op);
-	DEFINE_WAIT(wait);
-	struct request_list *rl;
-	struct request *rq;
-
-	lockdep_assert_held(q->queue_lock);
-	WARN_ON_ONCE(q->mq_ops);
-
-	rl = blk_get_rl(q, bio);	/* transferred to @rq on success */
-retry:
-	rq = __get_request(rl, op, bio, flags, gfp);
-	if (!IS_ERR(rq))
-		return rq;
-
-	if (op & REQ_NOWAIT) {
-		blk_put_rl(rl);
-		return ERR_PTR(-EAGAIN);
-	}
-
-	if ((flags & BLK_MQ_REQ_NOWAIT) || unlikely(blk_queue_dying(q))) {
-		blk_put_rl(rl);
-		return rq;
-	}
-
-	/* wait on @rl and retry */
-	prepare_to_wait_exclusive(&rl->wait[is_sync], &wait,
-				  TASK_UNINTERRUPTIBLE);
-
-	trace_block_sleeprq(q, bio, op);
-
-	spin_unlock_irq(q->queue_lock);
-	io_schedule();
-
-	/*
-	 * After sleeping, we become a "batching" process and will be able
-	 * to allocate at least one request, and up to a big batch of them
-	 * for a small period time.  See ioc_batching, ioc_set_batching
-	 */
-	ioc_set_batching(q, current->io_context);
-
-	spin_lock_irq(q->queue_lock);
-	finish_wait(&rl->wait[is_sync], &wait);
-
-	goto retry;
-}
-
-/* flags: BLK_MQ_REQ_PREEMPT and/or BLK_MQ_REQ_NOWAIT. */
-static struct request *blk_old_get_request(struct request_queue *q,
-				unsigned int op, blk_mq_req_flags_t flags)
-{
-	struct request *rq;
-	gfp_t gfp_mask = flags & BLK_MQ_REQ_NOWAIT ? GFP_ATOMIC : GFP_NOIO;
-	int ret = 0;
-
-	WARN_ON_ONCE(q->mq_ops);
-
-	/* create ioc upfront */
-	create_io_context(gfp_mask, q->node);
-
-	ret = blk_queue_enter(q, flags);
-	if (ret)
-		return ERR_PTR(ret);
-	spin_lock_irq(q->queue_lock);
-	rq = get_request(q, op, NULL, flags, gfp_mask);
-	if (IS_ERR(rq)) {
-		spin_unlock_irq(q->queue_lock);
-		blk_queue_exit(q);
-		return rq;
-	}
-
-	/* q->queue_lock is unlocked at this point */
-	rq->__data_len = 0;
-	rq->__sector = (sector_t) -1;
-	rq->bio = rq->biotail = NULL;
-	return rq;
-}
-
 /**
  * blk_get_request - allocate a request
  * @q: request queue to allocate a request for
@@ -1624,53 +738,14 @@ struct request *blk_get_request(struct request_queue *q, unsigned int op,
 	WARN_ON_ONCE(op & REQ_NOWAIT);
 	WARN_ON_ONCE(flags & ~(BLK_MQ_REQ_NOWAIT | BLK_MQ_REQ_PREEMPT));
 
-	if (q->mq_ops) {
-		req = blk_mq_alloc_request(q, op, flags);
-		if (!IS_ERR(req) && q->mq_ops->initialize_rq_fn)
-			q->mq_ops->initialize_rq_fn(req);
-	} else {
-		req = blk_old_get_request(q, op, flags);
-		if (!IS_ERR(req) && q->initialize_rq_fn)
-			q->initialize_rq_fn(req);
-	}
+	req = blk_mq_alloc_request(q, op, flags);
+	if (!IS_ERR(req) && q->mq_ops->initialize_rq_fn)
+		q->mq_ops->initialize_rq_fn(req);
 
 	return req;
 }
 EXPORT_SYMBOL(blk_get_request);
 
-/**
- * blk_requeue_request - put a request back on queue
- * @q:		request queue where request should be inserted
- * @rq:		request to be inserted
- *
- * Description:
- *    Drivers often keep queueing requests until the hardware cannot accept
- *    more, when that condition happens we need to put the request back
- *    on the queue. Must be called with queue lock held.
- */
-void blk_requeue_request(struct request_queue *q, struct request *rq)
-{
-	lockdep_assert_held(q->queue_lock);
-	WARN_ON_ONCE(q->mq_ops);
-
-	blk_delete_timer(rq);
-	blk_clear_rq_complete(rq);
-	trace_block_rq_requeue(q, rq);
-	rq_qos_requeue(q, rq);
-
-	BUG_ON(blk_queued_rq(rq));
-
-	elv_requeue_request(q, rq);
-}
-EXPORT_SYMBOL(blk_requeue_request);
-
-static void add_acct_request(struct request_queue *q, struct request *rq,
-			     int where)
-{
-	blk_account_io_start(rq, true);
-	__elv_add_request(q, rq, where);
-}
-
 static void part_round_stats_single(struct request_queue *q, int cpu,
 				    struct hd_struct *part, unsigned long now,
 				    unsigned int inflight)
@@ -1730,61 +805,16 @@ EXPORT_SYMBOL_GPL(part_round_stats);
 
 void __blk_put_request(struct request_queue *q, struct request *req)
 {
-	req_flags_t rq_flags = req->rq_flags;
-
 	if (unlikely(!q))
 		return;
 
-	if (q->mq_ops) {
-		blk_mq_free_request(req);
-		return;
-	}
-
-	lockdep_assert_held(q->queue_lock);
-
-	blk_req_zone_write_unlock(req);
-	blk_pm_put_request(req);
-	blk_pm_mark_last_busy(req);
-
-	elv_completed_request(q, req);
-
-	/* this is a bio leak */
-	WARN_ON(req->bio != NULL);
-
-	rq_qos_done(q, req);
-
-	/*
-	 * Request may not have originated from ll_rw_blk. if not,
-	 * it didn't come out of our reserved rq pools
-	 */
-	if (rq_flags & RQF_ALLOCED) {
-		struct request_list *rl = blk_rq_rl(req);
-		bool sync = op_is_sync(req->cmd_flags);
-
-		BUG_ON(!list_empty(&req->queuelist));
-		BUG_ON(ELV_ON_HASH(req));
-
-		blk_free_request(rl, req);
-		freed_request(rl, sync, rq_flags);
-		blk_put_rl(rl);
-		blk_queue_exit(q);
-	}
+	blk_mq_free_request(req);
 }
 EXPORT_SYMBOL_GPL(__blk_put_request);
 
 void blk_put_request(struct request *req)
 {
-	struct request_queue *q = req->q;
-
-	if (q->mq_ops)
-		blk_mq_free_request(req);
-	else {
-		unsigned long flags;
-
-		spin_lock_irqsave(q->queue_lock, flags);
-		__blk_put_request(q, req);
-		spin_unlock_irqrestore(q->queue_lock, flags);
-	}
+	blk_mq_free_request(req);
 }
 EXPORT_SYMBOL(blk_put_request);
 
@@ -1893,10 +923,7 @@ bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
 		return false;
 	*request_count = 0;
 
-	if (q->mq_ops)
-		plug_list = &plug->mq_list;
-	else
-		plug_list = &plug->list;
+	plug_list = &plug->mq_list;
 
 	list_for_each_entry_reverse(rq, plug_list, queuelist) {
 		bool merged = false;
@@ -1947,11 +974,7 @@ unsigned int blk_plug_queued_count(struct request_queue *q)
 	if (!plug)
 		goto out;
 
-	if (q->mq_ops)
-		plug_list = &plug->mq_list;
-	else
-		plug_list = &plug->list;
-
+	plug_list = &plug->mq_list;
 	list_for_each_entry(rq, plug_list, queuelist) {
 		if (rq->q == q)
 			ret++;
@@ -1979,133 +1002,6 @@ void blk_init_request_from_bio(struct request *req, struct bio *bio)
 }
 EXPORT_SYMBOL_GPL(blk_init_request_from_bio);
 
-static blk_qc_t blk_queue_bio(struct request_queue *q, struct bio *bio)
-{
-	struct blk_plug *plug;
-	int where = ELEVATOR_INSERT_SORT;
-	struct request *req, *free;
-	unsigned int request_count = 0;
-
-	/*
-	 * low level driver can indicate that it wants pages above a
-	 * certain limit bounced to low memory (ie for highmem, or even
-	 * ISA dma in theory)
-	 */
-	blk_queue_bounce(q, &bio);
-
-	blk_queue_split(q, &bio);
-
-	if (!bio_integrity_prep(bio))
-		return BLK_QC_T_NONE;
-
-	if (op_is_flush(bio->bi_opf)) {
-		spin_lock_irq(q->queue_lock);
-		where = ELEVATOR_INSERT_FLUSH;
-		goto get_rq;
-	}
-
-	/*
-	 * Check if we can merge with the plugged list before grabbing
-	 * any locks.
-	 */
-	if (!blk_queue_nomerges(q)) {
-		if (blk_attempt_plug_merge(q, bio, &request_count, NULL))
-			return BLK_QC_T_NONE;
-	} else
-		request_count = blk_plug_queued_count(q);
-
-	spin_lock_irq(q->queue_lock);
-
-	switch (elv_merge(q, &req, bio)) {
-	case ELEVATOR_BACK_MERGE:
-		if (!bio_attempt_back_merge(q, req, bio))
-			break;
-		elv_bio_merged(q, req, bio);
-		free = attempt_back_merge(q, req);
-		if (free)
-			__blk_put_request(q, free);
-		else
-			elv_merged_request(q, req, ELEVATOR_BACK_MERGE);
-		goto out_unlock;
-	case ELEVATOR_FRONT_MERGE:
-		if (!bio_attempt_front_merge(q, req, bio))
-			break;
-		elv_bio_merged(q, req, bio);
-		free = attempt_front_merge(q, req);
-		if (free)
-			__blk_put_request(q, free);
-		else
-			elv_merged_request(q, req, ELEVATOR_FRONT_MERGE);
-		goto out_unlock;
-	default:
-		break;
-	}
-
-get_rq:
-	rq_qos_throttle(q, bio, q->queue_lock);
-
-	/*
-	 * Grab a free request. This is might sleep but can not fail.
-	 * Returns with the queue unlocked.
-	 */
-	blk_queue_enter_live(q);
-	req = get_request(q, bio->bi_opf, bio, 0, GFP_NOIO);
-	if (IS_ERR(req)) {
-		blk_queue_exit(q);
-		rq_qos_cleanup(q, bio);
-		if (PTR_ERR(req) == -ENOMEM)
-			bio->bi_status = BLK_STS_RESOURCE;
-		else
-			bio->bi_status = BLK_STS_IOERR;
-		bio_endio(bio);
-		goto out_unlock;
-	}
-
-	rq_qos_track(q, req, bio);
-
-	/*
-	 * After dropping the lock and possibly sleeping here, our request
-	 * may now be mergeable after it had proven unmergeable (above).
-	 * We don't worry about that case for efficiency. It won't happen
-	 * often, and the elevators are able to handle it.
-	 */
-	blk_init_request_from_bio(req, bio);
-
-	if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags))
-		req->cpu = raw_smp_processor_id();
-
-	plug = current->plug;
-	if (plug) {
-		/*
-		 * If this is the first request added after a plug, fire
-		 * of a plug trace.
-		 *
-		 * @request_count may become stale because of schedule
-		 * out, so check plug list again.
-		 */
-		if (!request_count || list_empty(&plug->list))
-			trace_block_plug(q);
-		else {
-			struct request *last = list_entry_rq(plug->list.prev);
-			if (request_count >= BLK_MAX_REQUEST_COUNT ||
-			    blk_rq_bytes(last) >= BLK_PLUG_FLUSH_SIZE) {
-				blk_flush_plug_list(plug, false);
-				trace_block_plug(q);
-			}
-		}
-		list_add_tail(&req->queuelist, &plug->list);
-		blk_account_io_start(req, true);
-	} else {
-		spin_lock_irq(q->queue_lock);
-		add_acct_request(q, req, where);
-		__blk_run_queue(q);
-out_unlock:
-		spin_unlock_irq(q->queue_lock);
-	}
-
-	return BLK_QC_T_NONE;
-}
-
 static void handle_bad_sector(struct bio *bio, sector_t maxsector)
 {
 	char b[BDEVNAME_SIZE];
@@ -2617,9 +1513,6 @@ static int blk_cloned_rq_check_limits(struct request_queue *q,
  */
 blk_status_t blk_insert_cloned_request(struct request_queue *q, struct request *rq)
 {
-	unsigned long flags;
-	int where = ELEVATOR_INSERT_BACK;
-
 	if (blk_cloned_rq_check_limits(q, rq))
 		return BLK_STS_IOERR;
 
@@ -2627,38 +1520,15 @@ blk_status_t blk_insert_cloned_request(struct request_queue *q, struct request *
 	    should_fail_request(&rq->rq_disk->part0, blk_rq_bytes(rq)))
 		return BLK_STS_IOERR;
 
-	if (q->mq_ops) {
-		if (blk_queue_io_stat(q))
-			blk_account_io_start(rq, true);
-		/*
-		 * Since we have a scheduler attached on the top device,
-		 * bypass a potential scheduler on the bottom device for
-		 * insert.
-		 */
-		return blk_mq_request_issue_directly(rq);
-	}
-
-	spin_lock_irqsave(q->queue_lock, flags);
-	if (unlikely(blk_queue_dying(q))) {
-		spin_unlock_irqrestore(q->queue_lock, flags);
-		return BLK_STS_IOERR;
-	}
+	if (blk_queue_io_stat(q))
+		blk_account_io_start(rq, true);
 
 	/*
-	 * Submitting request must be dequeued before calling this function
-	 * because it will be linked to another request_queue
+	 * Since we have a scheduler attached on the top device,
+	 * bypass a potential scheduler on the bottom device for
+	 * insert.
 	 */
-	BUG_ON(blk_queued_rq(rq));
-
-	if (op_is_flush(rq->cmd_flags))
-		where = ELEVATOR_INSERT_FLUSH;
-
-	add_acct_request(q, rq, where);
-	if (where == ELEVATOR_INSERT_FLUSH)
-		__blk_run_queue(q);
-	spin_unlock_irqrestore(q->queue_lock, flags);
-
-	return BLK_STS_OK;
+	return blk_mq_request_issue_directly(rq);
 }
 EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
 
@@ -2778,225 +1648,6 @@ void blk_account_io_start(struct request *rq, bool new_io)
 	part_stat_unlock();
 }
 
-static struct request *elv_next_request(struct request_queue *q)
-{
-	struct request *rq;
-	struct blk_flush_queue *fq = blk_get_flush_queue(q, NULL);
-
-	WARN_ON_ONCE(q->mq_ops);
-
-	while (1) {
-		list_for_each_entry(rq, &q->queue_head, queuelist) {
-#ifdef CONFIG_PM
-			/*
-			 * If a request gets queued in state RPM_SUSPENDED
-			 * then that's a kernel bug.
-			 */
-			WARN_ON_ONCE(q->rpm_status == RPM_SUSPENDED);
-#endif
-			return rq;
-		}
-
-		/*
-		 * Flush request is running and flush request isn't queueable
-		 * in the drive, we can hold the queue till flush request is
-		 * finished. Even we don't do this, driver can't dispatch next
-		 * requests and will requeue them. And this can improve
-		 * throughput too. For example, we have request flush1, write1,
-		 * flush 2. flush1 is dispatched, then queue is hold, write1
-		 * isn't inserted to queue. After flush1 is finished, flush2
-		 * will be dispatched. Since disk cache is already clean,
-		 * flush2 will be finished very soon, so looks like flush2 is
-		 * folded to flush1.
-		 * Since the queue is hold, a flag is set to indicate the queue
-		 * should be restarted later. Please see flush_end_io() for
-		 * details.
-		 */
-		if (fq->flush_pending_idx != fq->flush_running_idx &&
-				!queue_flush_queueable(q)) {
-			fq->flush_queue_delayed = 1;
-			return NULL;
-		}
-		if (unlikely(blk_queue_bypass(q)) ||
-		    !q->elevator->type->ops.sq.elevator_dispatch_fn(q, 0))
-			return NULL;
-	}
-}
-
-/**
- * blk_peek_request - peek at the top of a request queue
- * @q: request queue to peek at
- *
- * Description:
- *     Return the request at the top of @q.  The returned request
- *     should be started using blk_start_request() before LLD starts
- *     processing it.
- *
- * Return:
- *     Pointer to the request at the top of @q if available.  Null
- *     otherwise.
- */
-struct request *blk_peek_request(struct request_queue *q)
-{
-	struct request *rq;
-	int ret;
-
-	lockdep_assert_held(q->queue_lock);
-	WARN_ON_ONCE(q->mq_ops);
-
-	while ((rq = elv_next_request(q)) != NULL) {
-		if (!(rq->rq_flags & RQF_STARTED)) {
-			/*
-			 * This is the first time the device driver
-			 * sees this request (possibly after
-			 * requeueing).  Notify IO scheduler.
-			 */
-			if (rq->rq_flags & RQF_SORTED)
-				elv_activate_rq(q, rq);
-
-			/*
-			 * just mark as started even if we don't start
-			 * it, a request that has been delayed should
-			 * not be passed by new incoming requests
-			 */
-			rq->rq_flags |= RQF_STARTED;
-			trace_block_rq_issue(q, rq);
-		}
-
-		if (!q->boundary_rq || q->boundary_rq == rq) {
-			q->end_sector = rq_end_sector(rq);
-			q->boundary_rq = NULL;
-		}
-
-		if (rq->rq_flags & RQF_DONTPREP)
-			break;
-
-		if (q->dma_drain_size && blk_rq_bytes(rq)) {
-			/*
-			 * make sure space for the drain appears we
-			 * know we can do this because max_hw_segments
-			 * has been adjusted to be one fewer than the
-			 * device can handle
-			 */
-			rq->nr_phys_segments++;
-		}
-
-		if (!q->prep_rq_fn)
-			break;
-
-		ret = q->prep_rq_fn(q, rq);
-		if (ret == BLKPREP_OK) {
-			break;
-		} else if (ret == BLKPREP_DEFER) {
-			/*
-			 * the request may have been (partially) prepped.
-			 * we need to keep this request in the front to
-			 * avoid resource deadlock.  RQF_STARTED will
-			 * prevent other fs requests from passing this one.
-			 */
-			if (q->dma_drain_size && blk_rq_bytes(rq) &&
-			    !(rq->rq_flags & RQF_DONTPREP)) {
-				/*
-				 * remove the space for the drain we added
-				 * so that we don't add it again
-				 */
-				--rq->nr_phys_segments;
-			}
-
-			rq = NULL;
-			break;
-		} else if (ret == BLKPREP_KILL || ret == BLKPREP_INVALID) {
-			rq->rq_flags |= RQF_QUIET;
-			/*
-			 * Mark this request as started so we don't trigger
-			 * any debug logic in the end I/O path.
-			 */
-			blk_start_request(rq);
-			__blk_end_request_all(rq, ret == BLKPREP_INVALID ?
-					BLK_STS_TARGET : BLK_STS_IOERR);
-		} else {
-			printk(KERN_ERR "%s: bad return=%d\n", __func__, ret);
-			break;
-		}
-	}
-
-	return rq;
-}
-EXPORT_SYMBOL(blk_peek_request);
-
-static void blk_dequeue_request(struct request *rq)
-{
-	struct request_queue *q = rq->q;
-
-	BUG_ON(list_empty(&rq->queuelist));
-	BUG_ON(ELV_ON_HASH(rq));
-
-	list_del_init(&rq->queuelist);
-
-	/*
-	 * the time frame between a request being removed from the lists
-	 * and to it is freed is accounted as io that is in progress at
-	 * the driver side.
-	 */
-	if (blk_account_rq(rq))
-		q->in_flight[rq_is_sync(rq)]++;
-}
-
-/**
- * blk_start_request - start request processing on the driver
- * @req: request to dequeue
- *
- * Description:
- *     Dequeue @req and start timeout timer on it.  This hands off the
- *     request to the driver.
- */
-void blk_start_request(struct request *req)
-{
-	lockdep_assert_held(req->q->queue_lock);
-	WARN_ON_ONCE(req->q->mq_ops);
-
-	blk_dequeue_request(req);
-
-	if (test_bit(QUEUE_FLAG_STATS, &req->q->queue_flags)) {
-		req->io_start_time_ns = ktime_get_ns();
-#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
-		req->throtl_size = blk_rq_sectors(req);
-#endif
-		req->rq_flags |= RQF_STATS;
-		rq_qos_issue(req->q, req);
-	}
-
-	BUG_ON(blk_rq_is_complete(req));
-	blk_add_timer(req);
-}
-EXPORT_SYMBOL(blk_start_request);
-
-/**
- * blk_fetch_request - fetch a request from a request queue
- * @q: request queue to fetch a request from
- *
- * Description:
- *     Return the request at the top of @q.  The request is started on
- *     return and LLD can start processing it immediately.
- *
- * Return:
- *     Pointer to the request at the top of @q if available.  Null
- *     otherwise.
- */
-struct request *blk_fetch_request(struct request_queue *q)
-{
-	struct request *rq;
-
-	lockdep_assert_held(q->queue_lock);
-	WARN_ON_ONCE(q->mq_ops);
-
-	rq = blk_peek_request(q);
-	if (rq)
-		blk_start_request(rq);
-	return rq;
-}
-EXPORT_SYMBOL(blk_fetch_request);
-
 /*
  * Steal bios from a request and add them to a bio list.
  * The request must not have been partially completed before.
@@ -3122,252 +1773,6 @@ bool blk_update_request(struct request *req, blk_status_t error,
 }
 EXPORT_SYMBOL_GPL(blk_update_request);
 
-static bool blk_update_bidi_request(struct request *rq, blk_status_t error,
-				    unsigned int nr_bytes,
-				    unsigned int bidi_bytes)
-{
-	if (blk_update_request(rq, error, nr_bytes))
-		return true;
-
-	/* Bidi request must be completed as a whole */
-	if (unlikely(blk_bidi_rq(rq)) &&
-	    blk_update_request(rq->next_rq, error, bidi_bytes))
-		return true;
-
-	if (blk_queue_add_random(rq->q))
-		add_disk_randomness(rq->rq_disk);
-
-	return false;
-}
-
-/**
- * blk_unprep_request - unprepare a request
- * @req:	the request
- *
- * This function makes a request ready for complete resubmission (or
- * completion).  It happens only after all error handling is complete,
- * so represents the appropriate moment to deallocate any resources
- * that were allocated to the request in the prep_rq_fn.  The queue
- * lock is held when calling this.
- */
-void blk_unprep_request(struct request *req)
-{
-	struct request_queue *q = req->q;
-
-	req->rq_flags &= ~RQF_DONTPREP;
-	if (q->unprep_rq_fn)
-		q->unprep_rq_fn(q, req);
-}
-EXPORT_SYMBOL_GPL(blk_unprep_request);
-
-void blk_finish_request(struct request *req, blk_status_t error)
-{
-	struct request_queue *q = req->q;
-	u64 now = ktime_get_ns();
-
-	lockdep_assert_held(req->q->queue_lock);
-	WARN_ON_ONCE(q->mq_ops);
-
-	if (req->rq_flags & RQF_STATS)
-		blk_stat_add(req, now);
-
-	BUG_ON(blk_queued_rq(req));
-
-	if (unlikely(laptop_mode) && !blk_rq_is_passthrough(req))
-		laptop_io_completion(req->q->backing_dev_info);
-
-	blk_delete_timer(req);
-
-	if (req->rq_flags & RQF_DONTPREP)
-		blk_unprep_request(req);
-
-	blk_account_io_done(req, now);
-
-	if (req->end_io) {
-		rq_qos_done(q, req);
-		req->end_io(req, error);
-	} else {
-		if (blk_bidi_rq(req))
-			__blk_put_request(req->next_rq->q, req->next_rq);
-
-		__blk_put_request(q, req);
-	}
-}
-EXPORT_SYMBOL(blk_finish_request);
-
-/**
- * blk_end_bidi_request - Complete a bidi request
- * @rq:         the request to complete
- * @error:      block status code
- * @nr_bytes:   number of bytes to complete @rq
- * @bidi_bytes: number of bytes to complete @rq->next_rq
- *
- * Description:
- *     Ends I/O on a number of bytes attached to @rq and @rq->next_rq.
- *     Drivers that supports bidi can safely call this member for any
- *     type of request, bidi or uni.  In the later case @bidi_bytes is
- *     just ignored.
- *
- * Return:
- *     %false - we are done with this request
- *     %true  - still buffers pending for this request
- **/
-static bool blk_end_bidi_request(struct request *rq, blk_status_t error,
-				 unsigned int nr_bytes, unsigned int bidi_bytes)
-{
-	struct request_queue *q = rq->q;
-	unsigned long flags;
-
-	WARN_ON_ONCE(q->mq_ops);
-
-	if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
-		return true;
-
-	spin_lock_irqsave(q->queue_lock, flags);
-	blk_finish_request(rq, error);
-	spin_unlock_irqrestore(q->queue_lock, flags);
-
-	return false;
-}
-
-/**
- * __blk_end_bidi_request - Complete a bidi request with queue lock held
- * @rq:         the request to complete
- * @error:      block status code
- * @nr_bytes:   number of bytes to complete @rq
- * @bidi_bytes: number of bytes to complete @rq->next_rq
- *
- * Description:
- *     Identical to blk_end_bidi_request() except that queue lock is
- *     assumed to be locked on entry and remains so on return.
- *
- * Return:
- *     %false - we are done with this request
- *     %true  - still buffers pending for this request
- **/
-static bool __blk_end_bidi_request(struct request *rq, blk_status_t error,
-				   unsigned int nr_bytes, unsigned int bidi_bytes)
-{
-	lockdep_assert_held(rq->q->queue_lock);
-	WARN_ON_ONCE(rq->q->mq_ops);
-
-	if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
-		return true;
-
-	blk_finish_request(rq, error);
-
-	return false;
-}
-
-/**
- * blk_end_request - Helper function for drivers to complete the request.
- * @rq:       the request being processed
- * @error:    block status code
- * @nr_bytes: number of bytes to complete
- *
- * Description:
- *     Ends I/O on a number of bytes attached to @rq.
- *     If @rq has leftover, sets it up for the next range of segments.
- *
- * Return:
- *     %false - we are done with this request
- *     %true  - still buffers pending for this request
- **/
-bool blk_end_request(struct request *rq, blk_status_t error,
-		unsigned int nr_bytes)
-{
-	WARN_ON_ONCE(rq->q->mq_ops);
-	return blk_end_bidi_request(rq, error, nr_bytes, 0);
-}
-EXPORT_SYMBOL(blk_end_request);
-
-/**
- * blk_end_request_all - Helper function for drives to finish the request.
- * @rq: the request to finish
- * @error: block status code
- *
- * Description:
- *     Completely finish @rq.
- */
-void blk_end_request_all(struct request *rq, blk_status_t error)
-{
-	bool pending;
-	unsigned int bidi_bytes = 0;
-
-	if (unlikely(blk_bidi_rq(rq)))
-		bidi_bytes = blk_rq_bytes(rq->next_rq);
-
-	pending = blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
-	BUG_ON(pending);
-}
-EXPORT_SYMBOL(blk_end_request_all);
-
-/**
- * __blk_end_request - Helper function for drivers to complete the request.
- * @rq:       the request being processed
- * @error:    block status code
- * @nr_bytes: number of bytes to complete
- *
- * Description:
- *     Must be called with queue lock held unlike blk_end_request().
- *
- * Return:
- *     %false - we are done with this request
- *     %true  - still buffers pending for this request
- **/
-bool __blk_end_request(struct request *rq, blk_status_t error,
-		unsigned int nr_bytes)
-{
-	lockdep_assert_held(rq->q->queue_lock);
-	WARN_ON_ONCE(rq->q->mq_ops);
-
-	return __blk_end_bidi_request(rq, error, nr_bytes, 0);
-}
-EXPORT_SYMBOL(__blk_end_request);
-
-/**
- * __blk_end_request_all - Helper function for drives to finish the request.
- * @rq: the request to finish
- * @error:    block status code
- *
- * Description:
- *     Completely finish @rq.  Must be called with queue lock held.
- */
-void __blk_end_request_all(struct request *rq, blk_status_t error)
-{
-	bool pending;
-	unsigned int bidi_bytes = 0;
-
-	lockdep_assert_held(rq->q->queue_lock);
-	WARN_ON_ONCE(rq->q->mq_ops);
-
-	if (unlikely(blk_bidi_rq(rq)))
-		bidi_bytes = blk_rq_bytes(rq->next_rq);
-
-	pending = __blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
-	BUG_ON(pending);
-}
-EXPORT_SYMBOL(__blk_end_request_all);
-
-/**
- * __blk_end_request_cur - Helper function to finish the current request chunk.
- * @rq: the request to finish the current chunk for
- * @error:    block status code
- *
- * Description:
- *     Complete the current consecutively mapped chunk from @rq.  Must
- *     be called with queue lock held.
- *
- * Return:
- *     %false - we are done with this request
- *     %true  - still buffers pending for this request
- */
-bool __blk_end_request_cur(struct request *rq, blk_status_t error)
-{
-	return __blk_end_request(rq, error, blk_rq_cur_bytes(rq));
-}
-EXPORT_SYMBOL(__blk_end_request_cur);
-
 void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
 		     struct bio *bio)
 {
@@ -3567,7 +1972,6 @@ void blk_start_plug(struct blk_plug *plug)
 	if (tsk->plug)
 		return;
 
-	INIT_LIST_HEAD(&plug->list);
 	INIT_LIST_HEAD(&plug->mq_list);
 	INIT_LIST_HEAD(&plug->cb_list);
 	/*
@@ -3578,36 +1982,6 @@ void blk_start_plug(struct blk_plug *plug)
 }
 EXPORT_SYMBOL(blk_start_plug);
 
-static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
-{
-	struct request *rqa = container_of(a, struct request, queuelist);
-	struct request *rqb = container_of(b, struct request, queuelist);
-
-	return !(rqa->q < rqb->q ||
-		(rqa->q == rqb->q && blk_rq_pos(rqa) < blk_rq_pos(rqb)));
-}
-
-/*
- * If 'from_schedule' is true, then postpone the dispatch of requests
- * until a safe kblockd context. We due this to avoid accidental big
- * additional stack usage in driver dispatch, in places where the originally
- * plugger did not intend it.
- */
-static void queue_unplugged(struct request_queue *q, unsigned int depth,
-			    bool from_schedule)
-	__releases(q->queue_lock)
-{
-	lockdep_assert_held(q->queue_lock);
-
-	trace_block_unplug(q, depth, !from_schedule);
-
-	if (from_schedule)
-		blk_run_queue_async(q);
-	else
-		__blk_run_queue(q);
-	spin_unlock_irq(q->queue_lock);
-}
-
 static void flush_plug_callbacks(struct blk_plug *plug, bool from_schedule)
 {
 	LIST_HEAD(callbacks);
@@ -3652,65 +2026,10 @@ EXPORT_SYMBOL(blk_check_plugged);
 
 void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
 {
-	struct request_queue *q;
-	struct request *rq;
-	LIST_HEAD(list);
-	unsigned int depth;
-
 	flush_plug_callbacks(plug, from_schedule);
 
 	if (!list_empty(&plug->mq_list))
 		blk_mq_flush_plug_list(plug, from_schedule);
-
-	if (list_empty(&plug->list))
-		return;
-
-	list_splice_init(&plug->list, &list);
-
-	list_sort(NULL, &list, plug_rq_cmp);
-
-	q = NULL;
-	depth = 0;
-
-	while (!list_empty(&list)) {
-		rq = list_entry_rq(list.next);
-		list_del_init(&rq->queuelist);
-		BUG_ON(!rq->q);
-		if (rq->q != q) {
-			/*
-			 * This drops the queue lock
-			 */
-			if (q)
-				queue_unplugged(q, depth, from_schedule);
-			q = rq->q;
-			depth = 0;
-			spin_lock_irq(q->queue_lock);
-		}
-
-		/*
-		 * Short-circuit if @q is dead
-		 */
-		if (unlikely(blk_queue_dying(q))) {
-			__blk_end_request_all(rq, BLK_STS_IOERR);
-			continue;
-		}
-
-		/*
-		 * rq is already accounted, so use raw insert
-		 */
-		if (op_is_flush(rq->cmd_flags))
-			__elv_add_request(q, rq, ELEVATOR_INSERT_FLUSH);
-		else
-			__elv_add_request(q, rq, ELEVATOR_INSERT_SORT_MERGE);
-
-		depth++;
-	}
-
-	/*
-	 * This drops the queue lock
-	 */
-	if (q)
-		queue_unplugged(q, depth, from_schedule);
 }
 
 void blk_finish_plug(struct blk_plug *plug)
diff --git a/block/blk-exec.c b/block/blk-exec.c
index f7b292f12449..a34b7d918742 100644
--- a/block/blk-exec.c
+++ b/block/blk-exec.c
@@ -48,8 +48,6 @@ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk,
 			   struct request *rq, int at_head,
 			   rq_end_io_fn *done)
 {
-	int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
-
 	WARN_ON(irqs_disabled());
 	WARN_ON(!blk_rq_is_passthrough(rq));
 
@@ -60,23 +58,7 @@ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk,
 	 * don't check dying flag for MQ because the request won't
 	 * be reused after dying flag is set
 	 */
-	if (q->mq_ops) {
-		blk_mq_sched_insert_request(rq, at_head, true, false);
-		return;
-	}
-
-	spin_lock_irq(q->queue_lock);
-
-	if (unlikely(blk_queue_dying(q))) {
-		rq->rq_flags |= RQF_QUIET;
-		__blk_end_request_all(rq, BLK_STS_IOERR);
-		spin_unlock_irq(q->queue_lock);
-		return;
-	}
-
-	__elv_add_request(q, rq, where);
-	__blk_run_queue(q);
-	spin_unlock_irq(q->queue_lock);
+	blk_mq_sched_insert_request(rq, at_head, true, false);
 }
 EXPORT_SYMBOL_GPL(blk_execute_rq_nowait);
 
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);
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);
diff --git a/block/blk-settings.c b/block/blk-settings.c
index ac8b8ba4b126..39c3c301a687 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -20,40 +20,6 @@ EXPORT_SYMBOL(blk_max_low_pfn);
 
 unsigned long blk_max_pfn;
 
-/**
- * blk_queue_prep_rq - set a prepare_request function for queue
- * @q:		queue
- * @pfn:	prepare_request function
- *
- * It's possible for a queue to register a prepare_request callback which
- * is invoked before the request is handed to the request_fn. The goal of
- * the function is to prepare a request for I/O, it can be used to build a
- * cdb from the request data for instance.
- *
- */
-void blk_queue_prep_rq(struct request_queue *q, prep_rq_fn *pfn)
-{
-	q->prep_rq_fn = pfn;
-}
-EXPORT_SYMBOL(blk_queue_prep_rq);
-
-/**
- * blk_queue_unprep_rq - set an unprepare_request function for queue
- * @q:		queue
- * @ufn:	unprepare_request function
- *
- * It's possible for a queue to register an unprepare_request callback
- * which is invoked before the request is finally completed. The goal
- * of the function is to deallocate any data that was allocated in the
- * prepare_request callback.
- *
- */
-void blk_queue_unprep_rq(struct request_queue *q, unprep_rq_fn *ufn)
-{
-	q->unprep_rq_fn = ufn;
-}
-EXPORT_SYMBOL(blk_queue_unprep_rq);
-
 void blk_queue_softirq_done(struct request_queue *q, softirq_done_fn *fn)
 {
 	q->softirq_done_fn = fn;
@@ -163,8 +129,6 @@ void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
 
 	q->make_request_fn = mfn;
 	blk_queue_dma_alignment(q, 511);
-	blk_queue_congestion_threshold(q);
-	q->nr_batching = BLK_BATCH_REQ;
 
 	blk_set_default_limits(&q->limits);
 }
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 1b82ccfde3fe..d4b1b84ba8ca 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -68,7 +68,7 @@ queue_requests_store(struct request_queue *q, const char *page, size_t count)
 	unsigned long nr;
 	int ret, err;
 
-	if (!q->request_fn && !q->mq_ops)
+	if (!q->mq_ops)
 		return -EINVAL;
 
 	ret = queue_var_store(&nr, page, count);
@@ -78,11 +78,7 @@ queue_requests_store(struct request_queue *q, const char *page, size_t count)
 	if (nr < BLKDEV_MIN_RQ)
 		nr = BLKDEV_MIN_RQ;
 
-	if (q->request_fn)
-		err = blk_update_nr_requests(q, nr);
-	else
-		err = blk_mq_update_nr_requests(q, nr);
-
+	err = blk_mq_update_nr_requests(q, nr);
 	if (err)
 		return err;
 
@@ -463,20 +459,14 @@ static ssize_t queue_wb_lat_store(struct request_queue *q, const char *page,
 	 * ends up either enabling or disabling wbt completely. We can't
 	 * have IO inflight if that happens.
 	 */
-	if (q->mq_ops) {
-		blk_mq_freeze_queue(q);
-		blk_mq_quiesce_queue(q);
-	} else
-		blk_queue_bypass_start(q);
+	blk_mq_freeze_queue(q);
+	blk_mq_quiesce_queue(q);
 
 	wbt_set_min_lat(q, val);
 	wbt_update_limits(q);
 
-	if (q->mq_ops) {
-		blk_mq_unquiesce_queue(q);
-		blk_mq_unfreeze_queue(q);
-	} else
-		blk_queue_bypass_end(q);
+	blk_mq_unquiesce_queue(q);
+	blk_mq_unfreeze_queue(q);
 
 	return count;
 }
@@ -847,17 +837,10 @@ static void __blk_release_queue(struct work_struct *work)
 
 	blk_free_queue_stats(q->stats);
 
-	blk_exit_rl(q, &q->root_rl);
-
 	blk_queue_free_zone_bitmaps(q);
 
-	if (!q->mq_ops) {
-		if (q->exit_rq_fn)
-			q->exit_rq_fn(q, q->fq->flush_rq);
-		blk_free_flush_queue(q->fq);
-	} else {
+	if (q->mq_ops)
 		blk_mq_release(q);
-	}
 
 	blk_trace_shutdown(q);
 
@@ -920,7 +903,6 @@ int blk_register_queue(struct gendisk *disk)
 	if (!blk_queue_init_done(q)) {
 		queue_flag_set_unlocked(QUEUE_FLAG_INIT_DONE, q);
 		percpu_ref_switch_to_percpu(&q->q_usage_counter);
-		blk_queue_bypass_end(q);
 	}
 
 	ret = blk_trace_init_sysfs(dev);
@@ -947,7 +929,7 @@ int blk_register_queue(struct gendisk *disk)
 
 	blk_throtl_register_queue(q);
 
-	if (q->request_fn || (q->mq_ops && q->elevator)) {
+	if ((q->mq_ops && q->elevator)) {
 		ret = elv_register_queue(q);
 		if (ret) {
 			mutex_unlock(&q->sysfs_lock);
@@ -1005,7 +987,7 @@ void blk_unregister_queue(struct gendisk *disk)
 	blk_trace_remove_sysfs(disk_to_dev(disk));
 
 	mutex_lock(&q->sysfs_lock);
-	if (q->request_fn || (q->mq_ops && q->elevator))
+	if (q->mq_ops && q->elevator)
 		elv_unregister_queue(q);
 	mutex_unlock(&q->sysfs_lock);
 
diff --git a/block/blk.h b/block/blk.h
index 57a302bf5a70..e2604ae7ddfa 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -7,12 +7,6 @@
 #include <xen/xen.h>
 #include "blk-mq.h"
 
-/* Amount of time in which a process may batch requests */
-#define BLK_BATCH_TIME	(HZ/50UL)
-
-/* Number of requests a "batching" process may submit */
-#define BLK_BATCH_REQ	32
-
 /* Max future timer expiry for timeouts */
 #define BLK_MAX_TIMEOUT		(5 * HZ)
 
@@ -132,9 +126,6 @@ void blk_exit_rl(struct request_queue *q, struct request_list *rl);
 void blk_exit_queue(struct request_queue *q);
 void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
 			struct bio *bio);
-void blk_queue_bypass_start(struct request_queue *q);
-void blk_queue_bypass_end(struct request_queue *q);
-void __blk_queue_free_tags(struct request_queue *q);
 void blk_freeze_queue(struct request_queue *q);
 
 static inline void blk_queue_enter_live(struct request_queue *q)
@@ -281,23 +272,6 @@ static inline bool blk_rq_is_complete(struct request *rq)
 
 void blk_insert_flush(struct request *rq);
 
-static inline void elv_activate_rq(struct request_queue *q, struct request *rq)
-{
-	struct elevator_queue *e = q->elevator;
-
-	if (e->type->ops.sq.elevator_activate_req_fn)
-		e->type->ops.sq.elevator_activate_req_fn(q, rq);
-}
-
-static inline void elv_deactivate_rq(struct request_queue *q, struct request *rq)
-{
-	struct elevator_queue *e = q->elevator;
-
-	if (e->type->ops.sq.elevator_deactivate_req_fn)
-		e->type->ops.sq.elevator_deactivate_req_fn(q, rq);
-}
-
-int elevator_init(struct request_queue *);
 int elevator_init_mq(struct request_queue *q);
 int elevator_switch_mq(struct request_queue *q,
 			      struct elevator_type *new_e);
@@ -332,31 +306,8 @@ void blk_rq_set_mixed_merge(struct request *rq);
 bool blk_rq_merge_ok(struct request *rq, struct bio *bio);
 enum elv_merge blk_try_merge(struct request *rq, struct bio *bio);
 
-void blk_queue_congestion_threshold(struct request_queue *q);
-
 int blk_dev_init(void);
 
-
-/*
- * Return the threshold (number of used requests) at which the queue is
- * considered to be congested.  It include a little hysteresis to keep the
- * context switch rate down.
- */
-static inline int queue_congestion_on_threshold(struct request_queue *q)
-{
-	return q->nr_congestion_on;
-}
-
-/*
- * The threshold at which a queue is considered to be uncongested
- */
-static inline int queue_congestion_off_threshold(struct request_queue *q)
-{
-	return q->nr_congestion_off;
-}
-
-extern int blk_update_nr_requests(struct request_queue *, unsigned int);
-
 /*
  * Contribute to IO statistics IFF:
  *
@@ -478,8 +429,6 @@ static inline void blk_queue_bounce(struct request_queue *q, struct bio **bio)
 }
 #endif /* CONFIG_BOUNCE */
 
-extern void blk_drain_queue(struct request_queue *q);
-
 #ifdef CONFIG_BLK_CGROUP_IOLATENCY
 extern int blk_iolatency_init(struct request_queue *q);
 #else
diff --git a/block/elevator.c b/block/elevator.c
index 54e1adac26c5..334097c54b08 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -61,10 +61,8 @@ static int elv_iosched_allow_bio_merge(struct request *rq, struct bio *bio)
 	struct request_queue *q = rq->q;
 	struct elevator_queue *e = q->elevator;
 
-	if (e->uses_mq && e->type->ops.mq.allow_merge)
+	if (e->type->ops.mq.allow_merge)
 		return e->type->ops.mq.allow_merge(q, rq, bio);
-	else if (!e->uses_mq && e->type->ops.sq.elevator_allow_bio_merge_fn)
-		return e->type->ops.sq.elevator_allow_bio_merge_fn(q, rq, bio);
 
 	return 1;
 }
@@ -95,14 +93,14 @@ static bool elevator_match(const struct elevator_type *e, const char *name)
 }
 
 /*
- * Return scheduler with name 'name' and with matching 'mq capability
+ * Return scheduler with name 'name'
  */
-static struct elevator_type *elevator_find(const char *name, bool mq)
+static struct elevator_type *elevator_find(const char *name)
 {
 	struct elevator_type *e;
 
 	list_for_each_entry(e, &elv_list, list) {
-		if (elevator_match(e, name) && (mq == e->uses_mq))
+		if (elevator_match(e, name))
 			return e;
 	}
 
@@ -121,12 +119,12 @@ static struct elevator_type *elevator_get(struct request_queue *q,
 
 	spin_lock(&elv_list_lock);
 
-	e = elevator_find(name, q->mq_ops != NULL);
+	e = elevator_find(name);
 	if (!e && try_loading) {
 		spin_unlock(&elv_list_lock);
 		request_module("%s-iosched", name);
 		spin_lock(&elv_list_lock);
-		e = elevator_find(name, q->mq_ops != NULL);
+		e = elevator_find(name);
 	}
 
 	if (e && !try_module_get(e->elevator_owner))
@@ -150,26 +148,6 @@ static int __init elevator_setup(char *str)
 
 __setup("elevator=", elevator_setup);
 
-/* called during boot to load the elevator chosen by the elevator param */
-void __init load_default_elevator_module(void)
-{
-	struct elevator_type *e;
-
-	if (!chosen_elevator[0])
-		return;
-
-	/*
-	 * Boot parameter is deprecated, we haven't supported that for MQ.
-	 * Only look for non-mq schedulers from here.
-	 */
-	spin_lock(&elv_list_lock);
-	e = elevator_find(chosen_elevator, false);
-	spin_unlock(&elv_list_lock);
-
-	if (!e)
-		request_module("%s-iosched", chosen_elevator);
-}
-
 static struct kobj_type elv_ktype;
 
 struct elevator_queue *elevator_alloc(struct request_queue *q,
@@ -185,7 +163,6 @@ struct elevator_queue *elevator_alloc(struct request_queue *q,
 	kobject_init(&eq->kobj, &elv_ktype);
 	mutex_init(&eq->sysfs_lock);
 	hash_init(eq->hash);
-	eq->uses_mq = e->uses_mq;
 
 	return eq;
 }
@@ -200,52 +177,11 @@ static void elevator_release(struct kobject *kobj)
 	kfree(e);
 }
 
-/*
- * Use the default elevator specified by config boot param for non-mq devices,
- * or by config option.  Don't try to load modules as we could be running off
- * async and request_module() isn't allowed from async.
- */
-int elevator_init(struct request_queue *q)
-{
-	struct elevator_type *e = NULL;
-	int err = 0;
-
-	/*
-	 * q->sysfs_lock must be held to provide mutual exclusion between
-	 * elevator_switch() and here.
-	 */
-	mutex_lock(&q->sysfs_lock);
-	if (unlikely(q->elevator))
-		goto out_unlock;
-
-	if (*chosen_elevator) {
-		e = elevator_get(q, chosen_elevator, false);
-		if (!e)
-			printk(KERN_ERR "I/O scheduler %s not found\n",
-							chosen_elevator);
-	}
-
-	if (!e) {
-		printk(KERN_ERR
-			"Default I/O scheduler not found. Using noop.\n");
-		e = elevator_get(q, "noop", false);
-	}
-
-	err = e->ops.sq.elevator_init_fn(q, e);
-	if (err)
-		elevator_put(e);
-out_unlock:
-	mutex_unlock(&q->sysfs_lock);
-	return err;
-}
-
 void elevator_exit(struct request_queue *q, struct elevator_queue *e)
 {
 	mutex_lock(&e->sysfs_lock);
-	if (e->uses_mq && e->type->ops.mq.exit_sched)
+	if (e->type->ops.mq.exit_sched)
 		blk_mq_exit_sched(q, e);
-	else if (!e->uses_mq && e->type->ops.sq.elevator_exit_fn)
-		e->type->ops.sq.elevator_exit_fn(e);
 	mutex_unlock(&e->sysfs_lock);
 
 	kobject_put(&e->kobj);
@@ -393,10 +329,8 @@ enum elv_merge elv_merge(struct request_queue *q, struct request **req,
 		return ELEVATOR_BACK_MERGE;
 	}
 
-	if (e->uses_mq && e->type->ops.mq.request_merge)
+	if (e->type->ops.mq.request_merge)
 		return e->type->ops.mq.request_merge(q, req, bio);
-	else if (!e->uses_mq && e->type->ops.sq.elevator_merge_fn)
-		return e->type->ops.sq.elevator_merge_fn(q, req, bio);
 
 	return ELEVATOR_NO_MERGE;
 }
@@ -447,10 +381,8 @@ void elv_merged_request(struct request_queue *q, struct request *rq,
 {
 	struct elevator_queue *e = q->elevator;
 
-	if (e->uses_mq && e->type->ops.mq.request_merged)
+	if (e->type->ops.mq.request_merged)
 		e->type->ops.mq.request_merged(q, rq, type);
-	else if (!e->uses_mq && e->type->ops.sq.elevator_merged_fn)
-		e->type->ops.sq.elevator_merged_fn(q, rq, type);
 
 	if (type == ELEVATOR_BACK_MERGE)
 		elv_rqhash_reposition(q, rq);
@@ -464,13 +396,8 @@ void elv_merge_requests(struct request_queue *q, struct request *rq,
 	struct elevator_queue *e = q->elevator;
 	bool next_sorted = false;
 
-	if (e->uses_mq && e->type->ops.mq.requests_merged)
+	if (e->type->ops.mq.requests_merged)
 		e->type->ops.mq.requests_merged(q, rq, next);
-	else if (e->type->ops.sq.elevator_merge_req_fn) {
-		next_sorted = (__force bool)(next->rq_flags & RQF_SORTED);
-		if (next_sorted)
-			e->type->ops.sq.elevator_merge_req_fn(q, rq, next);
-	}
 
 	elv_rqhash_reposition(q, rq);
 
@@ -482,156 +409,12 @@ void elv_merge_requests(struct request_queue *q, struct request *rq,
 	q->last_merge = rq;
 }
 
-void elv_bio_merged(struct request_queue *q, struct request *rq,
-			struct bio *bio)
-{
-	struct elevator_queue *e = q->elevator;
-
-	if (WARN_ON_ONCE(e->uses_mq))
-		return;
-
-	if (e->type->ops.sq.elevator_bio_merged_fn)
-		e->type->ops.sq.elevator_bio_merged_fn(q, rq, bio);
-}
-
-void elv_requeue_request(struct request_queue *q, struct request *rq)
-{
-	/*
-	 * it already went through dequeue, we need to decrement the
-	 * in_flight count again
-	 */
-	if (blk_account_rq(rq)) {
-		q->in_flight[rq_is_sync(rq)]--;
-		if (rq->rq_flags & RQF_SORTED)
-			elv_deactivate_rq(q, rq);
-	}
-
-	rq->rq_flags &= ~RQF_STARTED;
-
-	blk_pm_requeue_request(rq);
-
-	__elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE);
-}
-
-void elv_drain_elevator(struct request_queue *q)
-{
-	struct elevator_queue *e = q->elevator;
-	static int printed;
-
-	if (WARN_ON_ONCE(e->uses_mq))
-		return;
-
-	lockdep_assert_held(q->queue_lock);
-
-	while (e->type->ops.sq.elevator_dispatch_fn(q, 1))
-		;
-	if (q->nr_sorted && !blk_queue_is_zoned(q) && printed++ < 10 ) {
-		printk(KERN_ERR "%s: forced dispatching is broken "
-		       "(nr_sorted=%u), please report this\n",
-		       q->elevator->type->elevator_name, q->nr_sorted);
-	}
-}
-
-void __elv_add_request(struct request_queue *q, struct request *rq, int where)
-{
-	trace_block_rq_insert(q, rq);
-
-	blk_pm_add_request(q, rq);
-
-	rq->q = q;
-
-	if (rq->rq_flags & RQF_SOFTBARRIER) {
-		/* barriers are scheduling boundary, update end_sector */
-		if (!blk_rq_is_passthrough(rq)) {
-			q->end_sector = rq_end_sector(rq);
-			q->boundary_rq = rq;
-		}
-	} else if (!(rq->rq_flags & RQF_ELVPRIV) &&
-		    (where == ELEVATOR_INSERT_SORT ||
-		     where == ELEVATOR_INSERT_SORT_MERGE))
-		where = ELEVATOR_INSERT_BACK;
-
-	switch (where) {
-	case ELEVATOR_INSERT_REQUEUE:
-	case ELEVATOR_INSERT_FRONT:
-		rq->rq_flags |= RQF_SOFTBARRIER;
-		list_add(&rq->queuelist, &q->queue_head);
-		break;
-
-	case ELEVATOR_INSERT_BACK:
-		rq->rq_flags |= RQF_SOFTBARRIER;
-		elv_drain_elevator(q);
-		list_add_tail(&rq->queuelist, &q->queue_head);
-		/*
-		 * We kick the queue here for the following reasons.
-		 * - The elevator might have returned NULL previously
-		 *   to delay requests and returned them now.  As the
-		 *   queue wasn't empty before this request, ll_rw_blk
-		 *   won't run the queue on return, resulting in hang.
-		 * - Usually, back inserted requests won't be merged
-		 *   with anything.  There's no point in delaying queue
-		 *   processing.
-		 */
-		__blk_run_queue(q);
-		break;
-
-	case ELEVATOR_INSERT_SORT_MERGE:
-		/*
-		 * If we succeed in merging this request with one in the
-		 * queue already, we are done - rq has now been freed,
-		 * so no need to do anything further.
-		 */
-		if (elv_attempt_insert_merge(q, rq))
-			break;
-		/* fall through */
-	case ELEVATOR_INSERT_SORT:
-		BUG_ON(blk_rq_is_passthrough(rq));
-		rq->rq_flags |= RQF_SORTED;
-		q->nr_sorted++;
-		if (rq_mergeable(rq)) {
-			elv_rqhash_add(q, rq);
-			if (!q->last_merge)
-				q->last_merge = rq;
-		}
-
-		/*
-		 * Some ioscheds (cfq) run q->request_fn directly, so
-		 * rq cannot be accessed after calling
-		 * elevator_add_req_fn.
-		 */
-		q->elevator->type->ops.sq.elevator_add_req_fn(q, rq);
-		break;
-
-	case ELEVATOR_INSERT_FLUSH:
-		rq->rq_flags |= RQF_SOFTBARRIER;
-		blk_insert_flush(rq);
-		break;
-	default:
-		printk(KERN_ERR "%s: bad insertion point %d\n",
-		       __func__, where);
-		BUG();
-	}
-}
-EXPORT_SYMBOL(__elv_add_request);
-
-void elv_add_request(struct request_queue *q, struct request *rq, int where)
-{
-	unsigned long flags;
-
-	spin_lock_irqsave(q->queue_lock, flags);
-	__elv_add_request(q, rq, where);
-	spin_unlock_irqrestore(q->queue_lock, flags);
-}
-EXPORT_SYMBOL(elv_add_request);
-
 struct request *elv_latter_request(struct request_queue *q, struct request *rq)
 {
 	struct elevator_queue *e = q->elevator;
 
-	if (e->uses_mq && e->type->ops.mq.next_request)
+	if (e->type->ops.mq.next_request)
 		return e->type->ops.mq.next_request(q, rq);
-	else if (!e->uses_mq && e->type->ops.sq.elevator_latter_req_fn)
-		return e->type->ops.sq.elevator_latter_req_fn(q, rq);
 
 	return NULL;
 }
@@ -640,66 +423,10 @@ struct request *elv_former_request(struct request_queue *q, struct request *rq)
 {
 	struct elevator_queue *e = q->elevator;
 
-	if (e->uses_mq && e->type->ops.mq.former_request)
+	if (e->type->ops.mq.former_request)
 		return e->type->ops.mq.former_request(q, rq);
-	if (!e->uses_mq && e->type->ops.sq.elevator_former_req_fn)
-		return e->type->ops.sq.elevator_former_req_fn(q, rq);
-	return NULL;
-}
-
-int elv_set_request(struct request_queue *q, struct request *rq,
-		    struct bio *bio, gfp_t gfp_mask)
-{
-	struct elevator_queue *e = q->elevator;
-
-	if (WARN_ON_ONCE(e->uses_mq))
-		return 0;
 
-	if (e->type->ops.sq.elevator_set_req_fn)
-		return e->type->ops.sq.elevator_set_req_fn(q, rq, bio, gfp_mask);
-	return 0;
-}
-
-void elv_put_request(struct request_queue *q, struct request *rq)
-{
-	struct elevator_queue *e = q->elevator;
-
-	if (WARN_ON_ONCE(e->uses_mq))
-		return;
-
-	if (e->type->ops.sq.elevator_put_req_fn)
-		e->type->ops.sq.elevator_put_req_fn(rq);
-}
-
-int elv_may_queue(struct request_queue *q, unsigned int op)
-{
-	struct elevator_queue *e = q->elevator;
-
-	if (WARN_ON_ONCE(e->uses_mq))
-		return 0;
-
-	if (e->type->ops.sq.elevator_may_queue_fn)
-		return e->type->ops.sq.elevator_may_queue_fn(q, op);
-
-	return ELV_MQUEUE_MAY;
-}
-
-void elv_completed_request(struct request_queue *q, struct request *rq)
-{
-	struct elevator_queue *e = q->elevator;
-
-	if (WARN_ON_ONCE(e->uses_mq))
-		return;
-
-	/*
-	 * request is released from the driver, io must be done
-	 */
-	if (blk_account_rq(rq)) {
-		q->in_flight[rq_is_sync(rq)]--;
-		if ((rq->rq_flags & RQF_SORTED) &&
-		    e->type->ops.sq.elevator_completed_req_fn)
-			e->type->ops.sq.elevator_completed_req_fn(q, rq);
-	}
+	return NULL;
 }
 
 #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
@@ -768,8 +495,6 @@ int elv_register_queue(struct request_queue *q)
 		}
 		kobject_uevent(&e->kobj, KOBJ_ADD);
 		e->registered = 1;
-		if (!e->uses_mq && e->type->ops.sq.elevator_registered_fn)
-			e->type->ops.sq.elevator_registered_fn(q);
 	}
 	return error;
 }
@@ -809,7 +534,7 @@ int elv_register(struct elevator_type *e)
 
 	/* register, don't allow duplicate names */
 	spin_lock(&elv_list_lock);
-	if (elevator_find(e->elevator_name, e->uses_mq)) {
+	if (elevator_find(e->elevator_name)) {
 		spin_unlock(&elv_list_lock);
 		kmem_cache_destroy(e->icq_cache);
 		return -EBUSY;
@@ -919,71 +644,17 @@ out_unlock:
  */
 static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
 {
-	struct elevator_queue *old = q->elevator;
-	bool old_registered = false;
 	int err;
 
 	lockdep_assert_held(&q->sysfs_lock);
 
-	if (q->mq_ops) {
-		blk_mq_freeze_queue(q);
-		blk_mq_quiesce_queue(q);
-
-		err = elevator_switch_mq(q, new_e);
-
-		blk_mq_unquiesce_queue(q);
-		blk_mq_unfreeze_queue(q);
-
-		return err;
-	}
-
-	/*
-	 * Turn on BYPASS and drain all requests w/ elevator private data.
-	 * Block layer doesn't call into a quiesced elevator - all requests
-	 * are directly put on the dispatch list without elevator data
-	 * using INSERT_BACK.  All requests have SOFTBARRIER set and no
-	 * merge happens either.
-	 */
-	if (old) {
-		old_registered = old->registered;
-
-		blk_queue_bypass_start(q);
-
-		/* unregister and clear all auxiliary data of the old elevator */
-		if (old_registered)
-			elv_unregister_queue(q);
-
-		ioc_clear_queue(q);
-	}
-
-	/* allocate, init and register new elevator */
-	err = new_e->ops.sq.elevator_init_fn(q, new_e);
-	if (err)
-		goto fail_init;
-
-	err = elv_register_queue(q);
-	if (err)
-		goto fail_register;
-
-	/* done, kill the old one and finish */
-	if (old) {
-		elevator_exit(q, old);
-		blk_queue_bypass_end(q);
-	}
-
-	blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name);
+	blk_mq_freeze_queue(q);
+	blk_mq_quiesce_queue(q);
 
-	return 0;
+	err = elevator_switch_mq(q, new_e);
 
-fail_register:
-	elevator_exit(q, q->elevator);
-fail_init:
-	/* switch failed, restore and re-register old elevator */
-	if (old) {
-		q->elevator = old;
-		elv_register_queue(q);
-		blk_queue_bypass_end(q);
-	}
+	blk_mq_unquiesce_queue(q);
+	blk_mq_unfreeze_queue(q);
 
 	return err;
 }
@@ -1032,7 +703,7 @@ ssize_t elv_iosched_store(struct request_queue *q, const char *name,
 {
 	int ret;
 
-	if (!(q->mq_ops || q->request_fn) || !elv_support_iosched(q))
+	if (!q->mq_ops || !elv_support_iosched(q))
 		return count;
 
 	ret = __elevator_change(q, name);
@@ -1047,7 +718,6 @@ ssize_t elv_iosched_show(struct request_queue *q, char *name)
 	struct elevator_queue *e = q->elevator;
 	struct elevator_type *elv = NULL;
 	struct elevator_type *__e;
-	bool uses_mq = q->mq_ops != NULL;
 	int len = 0;
 
 	if (!queue_is_rq_based(q))
@@ -1060,14 +730,11 @@ ssize_t elv_iosched_show(struct request_queue *q, char *name)
 
 	spin_lock(&elv_list_lock);
 	list_for_each_entry(__e, &elv_list, list) {
-		if (elv && elevator_match(elv, __e->elevator_name) &&
-		    (__e->uses_mq == uses_mq)) {
+		if (elv && elevator_match(elv, __e->elevator_name)) {
 			len += sprintf(name+len, "[%s] ", elv->elevator_name);
 			continue;
 		}
-		if (__e->uses_mq && q->mq_ops && elv_support_iosched(q))
-			len += sprintf(name+len, "%s ", __e->elevator_name);
-		else if (!__e->uses_mq && !q->mq_ops)
+		if (elv_support_iosched(q))
 			len += sprintf(name+len, "%s ", __e->elevator_name);
 	}
 	spin_unlock(&elv_list_lock);
diff --git a/block/kyber-iosched.c b/block/kyber-iosched.c
index eccac01a10b6..728757a34fa0 100644
--- a/block/kyber-iosched.c
+++ b/block/kyber-iosched.c
@@ -1032,7 +1032,6 @@ static struct elevator_type kyber_sched = {
 		.dispatch_request = kyber_dispatch_request,
 		.has_work = kyber_has_work,
 	},
-	.uses_mq = true,
 #ifdef CONFIG_BLK_DEBUG_FS
 	.queue_debugfs_attrs = kyber_queue_debugfs_attrs,
 	.hctx_debugfs_attrs = kyber_hctx_debugfs_attrs,
diff --git a/block/mq-deadline.c b/block/mq-deadline.c
index 099a9e05854c..513edefd10fd 100644
--- a/block/mq-deadline.c
+++ b/block/mq-deadline.c
@@ -777,7 +777,6 @@ static struct elevator_type mq_deadline = {
 		.exit_sched		= dd_exit_queue,
 	},
 
-	.uses_mq	= true,
 #ifdef CONFIG_BLK_DEBUG_FS
 	.queue_debugfs_attrs = deadline_queue_debugfs_attrs,
 #endif