Revert "block/mq-deadline: Add cgroup support"

This reverts commit 08a9ad8bf607 ("block/mq-deadline: Add cgroup support")
and a follow-up commit c06bc5a3fb42 ("block/mq-deadline: Remove a
WARN_ON_ONCE() call"). The added cgroup support has the following issues:

* It breaks cgroup interface file format rule by adding custom elements to a
  nested key-value file.

* It registers mq-deadline as a cgroup-aware policy even though all it's
  doing is collecting per-cgroup stats. Even if we need these stats, this
  isn't the right way to add them.

* It hasn't been reviewed from cgroup side.

Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 1130 insertions, 0 deletions

diff --git a/block/mq-deadline.c b/block/mq-deadline.c
new file mode 100644
index 000000000000..a09761cbdf12
--- /dev/null
+++ b/block/mq-deadline.c
@@ -0,0 +1,1130 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  MQ Deadline i/o scheduler - adaptation of the legacy deadline scheduler,
+ *  for the blk-mq scheduling framework
+ *
+ *  Copyright (C) 2016 Jens Axboe <axboe@kernel.dk>
+ */
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/blkdev.h>
+#include <linux/blk-mq.h>
+#include <linux/elevator.h>
+#include <linux/bio.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/compiler.h>
+#include <linux/rbtree.h>
+#include <linux/sbitmap.h>
+
+#include <trace/events/block.h>
+
+#include "blk.h"
+#include "blk-mq.h"
+#include "blk-mq-debugfs.h"
+#include "blk-mq-tag.h"
+#include "blk-mq-sched.h"
+
+/*
+ * See Documentation/block/deadline-iosched.rst
+ */
+static const int read_expire = HZ / 2;  /* max time before a read is submitted. */
+static const int write_expire = 5 * HZ; /* ditto for writes, these limits are SOFT! */
+/*
+ * Time after which to dispatch lower priority requests even if higher
+ * priority requests are pending.
+ */
+static const int aging_expire = 10 * HZ;
+static const int writes_starved = 2;    /* max times reads can starve a write */
+static const int fifo_batch = 16;       /* # of sequential requests treated as one
+				     by the above parameters. For throughput. */
+
+enum dd_data_dir {
+	DD_READ		= READ,
+	DD_WRITE	= WRITE,
+};
+
+enum { DD_DIR_COUNT = 2 };
+
+enum dd_prio {
+	DD_RT_PRIO	= 0,
+	DD_BE_PRIO	= 1,
+	DD_IDLE_PRIO	= 2,
+	DD_PRIO_MAX	= 2,
+};
+
+enum { DD_PRIO_COUNT = 3 };
+
+/* I/O statistics per I/O priority. */
+struct io_stats_per_prio {
+	local_t inserted;
+	local_t merged;
+	local_t dispatched;
+	local_t completed;
+};
+
+/* I/O statistics for all I/O priorities (enum dd_prio). */
+struct io_stats {
+	struct io_stats_per_prio stats[DD_PRIO_COUNT];
+};
+
+/*
+ * Deadline scheduler data per I/O priority (enum dd_prio). Requests are
+ * present on both sort_list[] and fifo_list[].
+ */
+struct dd_per_prio {
+	struct list_head dispatch;
+	struct rb_root sort_list[DD_DIR_COUNT];
+	struct list_head fifo_list[DD_DIR_COUNT];
+	/* Next request in FIFO order. Read, write or both are NULL. */
+	struct request *next_rq[DD_DIR_COUNT];
+};
+
+struct deadline_data {
+	/*
+	 * run time data
+	 */
+
+	struct dd_per_prio per_prio[DD_PRIO_COUNT];
+
+	/* Data direction of latest dispatched request. */
+	enum dd_data_dir last_dir;
+	unsigned int batching;		/* number of sequential requests made */
+	unsigned int starved;		/* times reads have starved writes */
+
+	struct io_stats __percpu *stats;
+
+	/*
+	 * settings that change how the i/o scheduler behaves
+	 */
+	int fifo_expire[DD_DIR_COUNT];
+	int fifo_batch;
+	int writes_starved;
+	int front_merges;
+	u32 async_depth;
+	int aging_expire;
+
+	spinlock_t lock;
+	spinlock_t zone_lock;
+};
+
+/* Count one event of type 'event_type' and with I/O priority 'prio' */
+#define dd_count(dd, event_type, prio) do {				\
+	struct io_stats *io_stats = get_cpu_ptr((dd)->stats);		\
+									\
+	BUILD_BUG_ON(!__same_type((dd), struct deadline_data *));	\
+	BUILD_BUG_ON(!__same_type((prio), enum dd_prio));		\
+	local_inc(&io_stats->stats[(prio)].event_type);			\
+	put_cpu_ptr(io_stats);						\
+} while (0)
+
+/*
+ * Returns the total number of dd_count(dd, event_type, prio) calls across all
+ * CPUs. No locking or barriers since it is fine if the returned sum is slightly
+ * outdated.
+ */
+#define dd_sum(dd, event_type, prio) ({					\
+	unsigned int cpu;						\
+	u32 sum = 0;							\
+									\
+	BUILD_BUG_ON(!__same_type((dd), struct deadline_data *));	\
+	BUILD_BUG_ON(!__same_type((prio), enum dd_prio));		\
+	for_each_present_cpu(cpu)					\
+		sum += local_read(&per_cpu_ptr((dd)->stats, cpu)->	\
+				  stats[(prio)].event_type);		\
+	sum;								\
+})
+
+/* Maps an I/O priority class to a deadline scheduler priority. */
+static const enum dd_prio ioprio_class_to_prio[] = {
+	[IOPRIO_CLASS_NONE]	= DD_BE_PRIO,
+	[IOPRIO_CLASS_RT]	= DD_RT_PRIO,
+	[IOPRIO_CLASS_BE]	= DD_BE_PRIO,
+	[IOPRIO_CLASS_IDLE]	= DD_IDLE_PRIO,
+};
+
+static inline struct rb_root *
+deadline_rb_root(struct dd_per_prio *per_prio, struct request *rq)
+{
+	return &per_prio->sort_list[rq_data_dir(rq)];
+}
+
+/*
+ * Returns the I/O priority class (IOPRIO_CLASS_*) that has been assigned to a
+ * request.
+ */
+static u8 dd_rq_ioclass(struct request *rq)
+{
+	return IOPRIO_PRIO_CLASS(req_get_ioprio(rq));
+}
+
+/*
+ * get the request after `rq' in sector-sorted order
+ */
+static inline struct request *
+deadline_latter_request(struct request *rq)
+{
+	struct rb_node *node = rb_next(&rq->rb_node);
+
+	if (node)
+		return rb_entry_rq(node);
+
+	return NULL;
+}
+
+static void
+deadline_add_rq_rb(struct dd_per_prio *per_prio, struct request *rq)
+{
+	struct rb_root *root = deadline_rb_root(per_prio, rq);
+
+	elv_rb_add(root, rq);
+}
+
+static inline void
+deadline_del_rq_rb(struct dd_per_prio *per_prio, struct request *rq)
+{
+	const enum dd_data_dir data_dir = rq_data_dir(rq);
+
+	if (per_prio->next_rq[data_dir] == rq)
+		per_prio->next_rq[data_dir] = deadline_latter_request(rq);
+
+	elv_rb_del(deadline_rb_root(per_prio, rq), rq);
+}
+
+/*
+ * remove rq from rbtree and fifo.
+ */
+static void deadline_remove_request(struct request_queue *q,
+				    struct dd_per_prio *per_prio,
+				    struct request *rq)
+{
+	list_del_init(&rq->queuelist);
+
+	/*
+	 * We might not be on the rbtree, if we are doing an insert merge
+	 */
+	if (!RB_EMPTY_NODE(&rq->rb_node))
+		deadline_del_rq_rb(per_prio, rq);
+
+	elv_rqhash_del(q, rq);
+	if (q->last_merge == rq)
+		q->last_merge = NULL;
+}
+
+static void dd_request_merged(struct request_queue *q, struct request *req,
+			      enum elv_merge type)
+{
+	struct deadline_data *dd = q->elevator->elevator_data;
+	const u8 ioprio_class = dd_rq_ioclass(req);
+	const enum dd_prio prio = ioprio_class_to_prio[ioprio_class];
+	struct dd_per_prio *per_prio = &dd->per_prio[prio];
+
+	/*
+	 * if the merge was a front merge, we need to reposition request
+	 */
+	if (type == ELEVATOR_FRONT_MERGE) {
+		elv_rb_del(deadline_rb_root(per_prio, req), req);
+		deadline_add_rq_rb(per_prio, req);
+	}
+}
+
+/*
+ * Callback function that is invoked after @next has been merged into @req.
+ */
+static void dd_merged_requests(struct request_queue *q, struct request *req,
+			       struct request *next)
+{
+	struct deadline_data *dd = q->elevator->elevator_data;
+	const u8 ioprio_class = dd_rq_ioclass(next);
+	const enum dd_prio prio = ioprio_class_to_prio[ioprio_class];
+
+	dd_count(dd, merged, prio);
+
+	/*
+	 * if next expires before rq, assign its expire time to rq
+	 * and move into next position (next will be deleted) in fifo
+	 */
+	if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) {
+		if (time_before((unsigned long)next->fifo_time,
+				(unsigned long)req->fifo_time)) {
+			list_move(&req->queuelist, &next->queuelist);
+			req->fifo_time = next->fifo_time;
+		}
+	}
+
+	/*
+	 * kill knowledge of next, this one is a goner
+	 */
+	deadline_remove_request(q, &dd->per_prio[prio], next);
+}
+
+/*
+ * move an entry to dispatch queue
+ */
+static void
+deadline_move_request(struct deadline_data *dd, struct dd_per_prio *per_prio,
+		      struct request *rq)
+{
+	const enum dd_data_dir data_dir = rq_data_dir(rq);
+
+	per_prio->next_rq[data_dir] = deadline_latter_request(rq);
+
+	/*
+	 * take it off the sort and fifo list
+	 */
+	deadline_remove_request(rq->q, per_prio, rq);
+}
+
+/* Number of requests queued for a given priority level. */
+static u32 dd_queued(struct deadline_data *dd, enum dd_prio prio)
+{
+	return dd_sum(dd, inserted, prio) - dd_sum(dd, completed, prio);
+}
+
+/*
+ * deadline_check_fifo returns 0 if there are no expired requests on the fifo,
+ * 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
+ */
+static inline int deadline_check_fifo(struct dd_per_prio *per_prio,
+				      enum dd_data_dir data_dir)
+{
+	struct request *rq = rq_entry_fifo(per_prio->fifo_list[data_dir].next);
+
+	/*
+	 * rq is expired!
+	 */
+	if (time_after_eq(jiffies, (unsigned long)rq->fifo_time))
+		return 1;
+
+	return 0;
+}
+
+/*
+ * For the specified data direction, return the next request to
+ * dispatch using arrival ordered lists.
+ */
+static struct request *
+deadline_fifo_request(struct deadline_data *dd, struct dd_per_prio *per_prio,
+		      enum dd_data_dir data_dir)
+{
+	struct request *rq;
+	unsigned long flags;
+
+	if (list_empty(&per_prio->fifo_list[data_dir]))
+		return NULL;
+
+	rq = rq_entry_fifo(per_prio->fifo_list[data_dir].next);
+	if (data_dir == DD_READ || !blk_queue_is_zoned(rq->q))
+		return rq;
+
+	/*
+	 * Look for a write request that can be dispatched, that is one with
+	 * an unlocked target zone.
+	 */
+	spin_lock_irqsave(&dd->zone_lock, flags);
+	list_for_each_entry(rq, &per_prio->fifo_list[DD_WRITE], queuelist) {
+		if (blk_req_can_dispatch_to_zone(rq))
+			goto out;
+	}
+	rq = NULL;
+out:
+	spin_unlock_irqrestore(&dd->zone_lock, flags);
+
+	return rq;
+}
+
+/*
+ * For the specified data direction, return the next request to
+ * dispatch using sector position sorted lists.
+ */
+static struct request *
+deadline_next_request(struct deadline_data *dd, struct dd_per_prio *per_prio,
+		      enum dd_data_dir data_dir)
+{
+	struct request *rq;
+	unsigned long flags;
+
+	rq = per_prio->next_rq[data_dir];
+	if (!rq)
+		return NULL;
+
+	if (data_dir == DD_READ || !blk_queue_is_zoned(rq->q))
+		return rq;
+
+	/*
+	 * Look for a write request that can be dispatched, that is one with
+	 * an unlocked target zone.
+	 */
+	spin_lock_irqsave(&dd->zone_lock, flags);
+	while (rq) {
+		if (blk_req_can_dispatch_to_zone(rq))
+			break;
+		rq = deadline_latter_request(rq);
+	}
+	spin_unlock_irqrestore(&dd->zone_lock, flags);
+
+	return rq;
+}
+
+/*
+ * deadline_dispatch_requests selects the best request according to
+ * read/write expire, fifo_batch, etc and with a start time <= @latest.
+ */
+static struct request *__dd_dispatch_request(struct deadline_data *dd,
+					     struct dd_per_prio *per_prio,
+					     u64 latest_start_ns)
+{
+	struct request *rq, *next_rq;
+	enum dd_data_dir data_dir;
+	enum dd_prio prio;
+	u8 ioprio_class;
+
+	lockdep_assert_held(&dd->lock);
+
+	if (!list_empty(&per_prio->dispatch)) {
+		rq = list_first_entry(&per_prio->dispatch, struct request,
+				      queuelist);
+		if (rq->start_time_ns > latest_start_ns)
+			return NULL;
+		list_del_init(&rq->queuelist);
+		goto done;
+	}
+
+	/*
+	 * batches are currently reads XOR writes
+	 */
+	rq = deadline_next_request(dd, per_prio, dd->last_dir);
+	if (rq && dd->batching < dd->fifo_batch)
+		/* we have a next request are still entitled to batch */
+		goto dispatch_request;
+
+	/*
+	 * at this point we are not running a batch. select the appropriate
+	 * data direction (read / write)
+	 */
+
+	if (!list_empty(&per_prio->fifo_list[DD_READ])) {
+		BUG_ON(RB_EMPTY_ROOT(&per_prio->sort_list[DD_READ]));
+
+		if (deadline_fifo_request(dd, per_prio, DD_WRITE) &&
+		    (dd->starved++ >= dd->writes_starved))
+			goto dispatch_writes;
+
+		data_dir = DD_READ;
+
+		goto dispatch_find_request;
+	}
+
+	/*
+	 * there are either no reads or writes have been starved
+	 */
+
+	if (!list_empty(&per_prio->fifo_list[DD_WRITE])) {
+dispatch_writes:
+		BUG_ON(RB_EMPTY_ROOT(&per_prio->sort_list[DD_WRITE]));
+
+		dd->starved = 0;
+
+		data_dir = DD_WRITE;
+
+		goto dispatch_find_request;
+	}
+
+	return NULL;
+
+dispatch_find_request:
+	/*
+	 * we are not running a batch, find best request for selected data_dir
+	 */
+	next_rq = deadline_next_request(dd, per_prio, data_dir);
+	if (deadline_check_fifo(per_prio, data_dir) || !next_rq) {
+		/*
+		 * A deadline has expired, the last request was in the other
+		 * direction, or we have run out of higher-sectored requests.
+		 * Start again from the request with the earliest expiry time.
+		 */
+		rq = deadline_fifo_request(dd, per_prio, data_dir);
+	} else {
+		/*
+		 * The last req was the same dir and we have a next request in
+		 * sort order. No expired requests so continue on from here.
+		 */
+		rq = next_rq;
+	}
+
+	/*
+	 * For a zoned block device, if we only have writes queued and none of
+	 * them can be dispatched, rq will be NULL.
+	 */
+	if (!rq)
+		return NULL;
+
+	dd->last_dir = data_dir;
+	dd->batching = 0;
+
+dispatch_request:
+	if (rq->start_time_ns > latest_start_ns)
+		return NULL;
+	/*
+	 * rq is the selected appropriate request.
+	 */
+	dd->batching++;
+	deadline_move_request(dd, per_prio, rq);
+done:
+	ioprio_class = dd_rq_ioclass(rq);
+	prio = ioprio_class_to_prio[ioprio_class];
+	dd_count(dd, dispatched, prio);
+	/*
+	 * If the request needs its target zone locked, do it.
+	 */
+	blk_req_zone_write_lock(rq);
+	rq->rq_flags |= RQF_STARTED;
+	return rq;
+}
+
+/*
+ * Called from blk_mq_run_hw_queue() -> __blk_mq_sched_dispatch_requests().
+ *
+ * One confusing aspect here is that we get called for a specific
+ * hardware queue, but we may return a request that is for a
+ * different hardware queue. This is because mq-deadline has shared
+ * state for all hardware queues, in terms of sorting, FIFOs, etc.
+ */
+static struct request *dd_dispatch_request(struct blk_mq_hw_ctx *hctx)
+{
+	struct deadline_data *dd = hctx->queue->elevator->elevator_data;
+	const u64 now_ns = ktime_get_ns();
+	struct request *rq = NULL;
+	enum dd_prio prio;
+
+	spin_lock(&dd->lock);
+	/*
+	 * Start with dispatching requests whose deadline expired more than
+	 * aging_expire jiffies ago.
+	 */
+	for (prio = DD_BE_PRIO; prio <= DD_PRIO_MAX; prio++) {
+		rq = __dd_dispatch_request(dd, &dd->per_prio[prio], now_ns -
+					   jiffies_to_nsecs(dd->aging_expire));
+		if (rq)
+			goto unlock;
+	}
+	/*
+	 * Next, dispatch requests in priority order. Ignore lower priority
+	 * requests if any higher priority requests are pending.
+	 */
+	for (prio = 0; prio <= DD_PRIO_MAX; prio++) {
+		rq = __dd_dispatch_request(dd, &dd->per_prio[prio], now_ns);
+		if (rq || dd_queued(dd, prio))
+			break;
+	}
+
+unlock:
+	spin_unlock(&dd->lock);
+
+	return rq;
+}
+
+/*
+ * Called by __blk_mq_alloc_request(). The shallow_depth value set by this
+ * function is used by __blk_mq_get_tag().
+ */
+static void dd_limit_depth(unsigned int op, struct blk_mq_alloc_data *data)
+{
+	struct deadline_data *dd = data->q->elevator->elevator_data;
+
+	/* Do not throttle synchronous reads. */
+	if (op_is_sync(op) && !op_is_write(op))
+		return;
+
+	/*
+	 * Throttle asynchronous requests and writes such that these requests
+	 * do not block the allocation of synchronous requests.
+	 */
+	data->shallow_depth = dd->async_depth;
+}
+
+/* Called by blk_mq_update_nr_requests(). */
+static void dd_depth_updated(struct blk_mq_hw_ctx *hctx)
+{
+	struct request_queue *q = hctx->queue;
+	struct deadline_data *dd = q->elevator->elevator_data;
+	struct blk_mq_tags *tags = hctx->sched_tags;
+
+	dd->async_depth = max(1UL, 3 * q->nr_requests / 4);
+
+	sbitmap_queue_min_shallow_depth(tags->bitmap_tags, dd->async_depth);
+}
+
+/* Called by blk_mq_init_hctx() and blk_mq_init_sched(). */
+static int dd_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
+{
+	dd_depth_updated(hctx);
+	return 0;
+}
+
+static void dd_exit_sched(struct elevator_queue *e)
+{
+	struct deadline_data *dd = e->elevator_data;
+	enum dd_prio prio;
+
+	for (prio = 0; prio <= DD_PRIO_MAX; prio++) {
+		struct dd_per_prio *per_prio = &dd->per_prio[prio];
+
+		WARN_ON_ONCE(!list_empty(&per_prio->fifo_list[DD_READ]));
+		WARN_ON_ONCE(!list_empty(&per_prio->fifo_list[DD_WRITE]));
+	}
+
+	free_percpu(dd->stats);
+
+	kfree(dd);
+}
+
+/*
+ * initialize elevator private data (deadline_data).
+ */
+static int dd_init_sched(struct request_queue *q, struct elevator_type *e)
+{
+	struct deadline_data *dd;
+	struct elevator_queue *eq;
+	enum dd_prio prio;
+	int ret = -ENOMEM;
+
+	eq = elevator_alloc(q, e);
+	if (!eq)
+		return ret;
+
+	dd = kzalloc_node(sizeof(*dd), GFP_KERNEL, q->node);
+	if (!dd)
+		goto put_eq;
+
+	eq->elevator_data = dd;
+
+	dd->stats = alloc_percpu_gfp(typeof(*dd->stats),
+				     GFP_KERNEL | __GFP_ZERO);
+	if (!dd->stats)
+		goto free_dd;
+
+	for (prio = 0; prio <= DD_PRIO_MAX; prio++) {
+		struct dd_per_prio *per_prio = &dd->per_prio[prio];
+
+		INIT_LIST_HEAD(&per_prio->dispatch);
+		INIT_LIST_HEAD(&per_prio->fifo_list[DD_READ]);
+		INIT_LIST_HEAD(&per_prio->fifo_list[DD_WRITE]);
+		per_prio->sort_list[DD_READ] = RB_ROOT;
+		per_prio->sort_list[DD_WRITE] = RB_ROOT;
+	}
+	dd->fifo_expire[DD_READ] = read_expire;
+	dd->fifo_expire[DD_WRITE] = write_expire;
+	dd->writes_starved = writes_starved;
+	dd->front_merges = 1;
+	dd->last_dir = DD_WRITE;
+	dd->fifo_batch = fifo_batch;
+	dd->aging_expire = aging_expire;
+	spin_lock_init(&dd->lock);
+	spin_lock_init(&dd->zone_lock);
+
+	q->elevator = eq;
+	return 0;
+
+free_dd:
+	kfree(dd);
+
+put_eq:
+	kobject_put(&eq->kobj);
+	return ret;
+}
+
+/*
+ * Try to merge @bio into an existing request. If @bio has been merged into
+ * an existing request, store the pointer to that request into *@rq.
+ */
+static int dd_request_merge(struct request_queue *q, struct request **rq,
+			    struct bio *bio)
+{
+	struct deadline_data *dd = q->elevator->elevator_data;
+	const u8 ioprio_class = IOPRIO_PRIO_CLASS(bio->bi_ioprio);
+	const enum dd_prio prio = ioprio_class_to_prio[ioprio_class];
+	struct dd_per_prio *per_prio = &dd->per_prio[prio];
+	sector_t sector = bio_end_sector(bio);
+	struct request *__rq;
+
+	if (!dd->front_merges)
+		return ELEVATOR_NO_MERGE;
+
+	__rq = elv_rb_find(&per_prio->sort_list[bio_data_dir(bio)], sector);
+	if (__rq) {
+		BUG_ON(sector != blk_rq_pos(__rq));
+
+		if (elv_bio_merge_ok(__rq, bio)) {
+			*rq = __rq;
+			return ELEVATOR_FRONT_MERGE;
+		}
+	}
+
+	return ELEVATOR_NO_MERGE;
+}
+
+/*
+ * Attempt to merge a bio into an existing request. This function is called
+ * before @bio is associated with a request.
+ */
+static bool dd_bio_merge(struct request_queue *q, struct bio *bio,
+		unsigned int nr_segs)
+{
+	struct deadline_data *dd = q->elevator->elevator_data;
+	struct request *free = NULL;
+	bool ret;
+
+	spin_lock(&dd->lock);
+	ret = blk_mq_sched_try_merge(q, bio, nr_segs, &free);
+	spin_unlock(&dd->lock);
+
+	if (free)
+		blk_mq_free_request(free);
+
+	return ret;
+}
+
+/*
+ * add rq to rbtree and fifo
+ */
+static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
+			      bool at_head)
+{
+	struct request_queue *q = hctx->queue;
+	struct deadline_data *dd = q->elevator->elevator_data;
+	const enum dd_data_dir data_dir = rq_data_dir(rq);
+	u16 ioprio = req_get_ioprio(rq);
+	u8 ioprio_class = IOPRIO_PRIO_CLASS(ioprio);
+	struct dd_per_prio *per_prio;
+	enum dd_prio prio;
+	LIST_HEAD(free);
+
+	lockdep_assert_held(&dd->lock);
+
+	/*
+	 * This may be a requeue of a write request that has locked its
+	 * target zone. If it is the case, this releases the zone lock.
+	 */
+	blk_req_zone_write_unlock(rq);
+
+	prio = ioprio_class_to_prio[ioprio_class];
+	dd_count(dd, inserted, prio);
+
+	if (blk_mq_sched_try_insert_merge(q, rq, &free)) {
+		blk_mq_free_requests(&free);
+		return;
+	}
+
+	trace_block_rq_insert(rq);
+
+	per_prio = &dd->per_prio[prio];
+	if (at_head) {
+		list_add(&rq->queuelist, &per_prio->dispatch);
+	} else {
+		deadline_add_rq_rb(per_prio, rq);
+
+		if (rq_mergeable(rq)) {
+			elv_rqhash_add(q, rq);
+			if (!q->last_merge)
+				q->last_merge = rq;
+		}
+
+		/*
+		 * set expire time and add to fifo list
+		 */
+		rq->fifo_time = jiffies + dd->fifo_expire[data_dir];
+		list_add_tail(&rq->queuelist, &per_prio->fifo_list[data_dir]);
+	}
+}
+
+/*
+ * Called from blk_mq_sched_insert_request() or blk_mq_sched_insert_requests().
+ */
+static void dd_insert_requests(struct blk_mq_hw_ctx *hctx,
+			       struct list_head *list, bool at_head)
+{
+	struct request_queue *q = hctx->queue;
+	struct deadline_data *dd = q->elevator->elevator_data;
+
+	spin_lock(&dd->lock);
+	while (!list_empty(list)) {
+		struct request *rq;
+
+		rq = list_first_entry(list, struct request, queuelist);
+		list_del_init(&rq->queuelist);
+		dd_insert_request(hctx, rq, at_head);
+	}
+	spin_unlock(&dd->lock);
+}
+
+/*
+ * Nothing to do here. This is defined only to ensure that .finish_request
+ * method is called upon request completion.
+ */
+static void dd_prepare_request(struct request *rq)
+{
+}
+
+/*
+ * Callback from inside blk_mq_free_request().
+ *
+ * For zoned block devices, write unlock the target zone of
+ * completed write requests. Do this while holding the zone lock
+ * spinlock so that the zone is never unlocked while deadline_fifo_request()
+ * or deadline_next_request() are executing. This function is called for
+ * all requests, whether or not these requests complete successfully.
+ *
+ * For a zoned block device, __dd_dispatch_request() may have stopped
+ * dispatching requests if all the queued requests are write requests directed
+ * at zones that are already locked due to on-going write requests. To ensure
+ * write request dispatch progress in this case, mark the queue as needing a
+ * restart to ensure that the queue is run again after completion of the
+ * request and zones being unlocked.
+ */
+static void dd_finish_request(struct request *rq)
+{
+	struct request_queue *q = rq->q;
+	struct deadline_data *dd = q->elevator->elevator_data;
+	const u8 ioprio_class = dd_rq_ioclass(rq);
+	const enum dd_prio prio = ioprio_class_to_prio[ioprio_class];
+	struct dd_per_prio *per_prio = &dd->per_prio[prio];
+
+	dd_count(dd, completed, prio);
+
+	if (blk_queue_is_zoned(q)) {
+		unsigned long flags;
+
+		spin_lock_irqsave(&dd->zone_lock, flags);
+		blk_req_zone_write_unlock(rq);
+		if (!list_empty(&per_prio->fifo_list[DD_WRITE]))
+			blk_mq_sched_mark_restart_hctx(rq->mq_hctx);
+		spin_unlock_irqrestore(&dd->zone_lock, flags);
+	}
+}
+
+static bool dd_has_work_for_prio(struct dd_per_prio *per_prio)
+{
+	return !list_empty_careful(&per_prio->dispatch) ||
+		!list_empty_careful(&per_prio->fifo_list[DD_READ]) ||
+		!list_empty_careful(&per_prio->fifo_list[DD_WRITE]);
+}
+
+static bool dd_has_work(struct blk_mq_hw_ctx *hctx)
+{
+	struct deadline_data *dd = hctx->queue->elevator->elevator_data;
+	enum dd_prio prio;
+
+	for (prio = 0; prio <= DD_PRIO_MAX; prio++)
+		if (dd_has_work_for_prio(&dd->per_prio[prio]))
+			return true;
+
+	return false;
+}
+
+/*
+ * sysfs parts below
+ */
+#define SHOW_INT(__FUNC, __VAR)						\
+static ssize_t __FUNC(struct elevator_queue *e, char *page)		\
+{									\
+	struct deadline_data *dd = e->elevator_data;			\
+									\
+	return sysfs_emit(page, "%d\n", __VAR);				\
+}
+#define SHOW_JIFFIES(__FUNC, __VAR) SHOW_INT(__FUNC, jiffies_to_msecs(__VAR))
+SHOW_JIFFIES(deadline_read_expire_show, dd->fifo_expire[DD_READ]);
+SHOW_JIFFIES(deadline_write_expire_show, dd->fifo_expire[DD_WRITE]);
+SHOW_JIFFIES(deadline_aging_expire_show, dd->aging_expire);
+SHOW_INT(deadline_writes_starved_show, dd->writes_starved);
+SHOW_INT(deadline_front_merges_show, dd->front_merges);
+SHOW_INT(deadline_async_depth_show, dd->front_merges);
+SHOW_INT(deadline_fifo_batch_show, dd->fifo_batch);
+#undef SHOW_INT
+#undef SHOW_JIFFIES
+
+#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)			\
+static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count)	\
+{									\
+	struct deadline_data *dd = e->elevator_data;			\
+	int __data, __ret;						\
+									\
+	__ret = kstrtoint(page, 0, &__data);				\
+	if (__ret < 0)							\
+		return __ret;						\
+	if (__data < (MIN))						\
+		__data = (MIN);						\
+	else if (__data > (MAX))					\
+		__data = (MAX);						\
+	*(__PTR) = __CONV(__data);					\
+	return count;							\
+}
+#define STORE_INT(__FUNC, __PTR, MIN, MAX)				\
+	STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, )
+#define STORE_JIFFIES(__FUNC, __PTR, MIN, MAX)				\
+	STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, msecs_to_jiffies)
+STORE_JIFFIES(deadline_read_expire_store, &dd->fifo_expire[DD_READ], 0, INT_MAX);
+STORE_JIFFIES(deadline_write_expire_store, &dd->fifo_expire[DD_WRITE], 0, INT_MAX);
+STORE_JIFFIES(deadline_aging_expire_store, &dd->aging_expire, 0, INT_MAX);
+STORE_INT(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX);
+STORE_INT(deadline_front_merges_store, &dd->front_merges, 0, 1);
+STORE_INT(deadline_async_depth_store, &dd->front_merges, 1, INT_MAX);
+STORE_INT(deadline_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX);
+#undef STORE_FUNCTION
+#undef STORE_INT
+#undef STORE_JIFFIES
+
+#define DD_ATTR(name) \
+	__ATTR(name, 0644, deadline_##name##_show, deadline_##name##_store)
+
+static struct elv_fs_entry deadline_attrs[] = {
+	DD_ATTR(read_expire),
+	DD_ATTR(write_expire),
+	DD_ATTR(writes_starved),
+	DD_ATTR(front_merges),
+	DD_ATTR(async_depth),
+	DD_ATTR(fifo_batch),
+	DD_ATTR(aging_expire),
+	__ATTR_NULL
+};
+
+#ifdef CONFIG_BLK_DEBUG_FS
+#define DEADLINE_DEBUGFS_DDIR_ATTRS(prio, data_dir, name)		\
+static void *deadline_##name##_fifo_start(struct seq_file *m,		\
+					  loff_t *pos)			\
+	__acquires(&dd->lock)						\
+{									\
+	struct request_queue *q = m->private;				\
+	struct deadline_data *dd = q->elevator->elevator_data;		\
+	struct dd_per_prio *per_prio = &dd->per_prio[prio];		\
+									\
+	spin_lock(&dd->lock);						\
+	return seq_list_start(&per_prio->fifo_list[data_dir], *pos);	\
+}									\
+									\
+static void *deadline_##name##_fifo_next(struct seq_file *m, void *v,	\
+					 loff_t *pos)			\
+{									\
+	struct request_queue *q = m->private;				\
+	struct deadline_data *dd = q->elevator->elevator_data;		\
+	struct dd_per_prio *per_prio = &dd->per_prio[prio];		\
+									\
+	return seq_list_next(v, &per_prio->fifo_list[data_dir], pos);	\
+}									\
+									\
+static void deadline_##name##_fifo_stop(struct seq_file *m, void *v)	\
+	__releases(&dd->lock)						\
+{									\
+	struct request_queue *q = m->private;				\
+	struct deadline_data *dd = q->elevator->elevator_data;		\
+									\
+	spin_unlock(&dd->lock);						\
+}									\
+									\
+static const struct seq_operations deadline_##name##_fifo_seq_ops = {	\
+	.start	= deadline_##name##_fifo_start,				\
+	.next	= deadline_##name##_fifo_next,				\
+	.stop	= deadline_##name##_fifo_stop,				\
+	.show	= blk_mq_debugfs_rq_show,				\
+};									\
+									\
+static int deadline_##name##_next_rq_show(void *data,			\
+					  struct seq_file *m)		\
+{									\
+	struct request_queue *q = data;					\
+	struct deadline_data *dd = q->elevator->elevator_data;		\
+	struct dd_per_prio *per_prio = &dd->per_prio[prio];		\
+	struct request *rq = per_prio->next_rq[data_dir];		\
+									\
+	if (rq)								\
+		__blk_mq_debugfs_rq_show(m, rq);			\
+	return 0;							\
+}
+
+DEADLINE_DEBUGFS_DDIR_ATTRS(DD_RT_PRIO, DD_READ, read0);
+DEADLINE_DEBUGFS_DDIR_ATTRS(DD_RT_PRIO, DD_WRITE, write0);
+DEADLINE_DEBUGFS_DDIR_ATTRS(DD_BE_PRIO, DD_READ, read1);
+DEADLINE_DEBUGFS_DDIR_ATTRS(DD_BE_PRIO, DD_WRITE, write1);
+DEADLINE_DEBUGFS_DDIR_ATTRS(DD_IDLE_PRIO, DD_READ, read2);
+DEADLINE_DEBUGFS_DDIR_ATTRS(DD_IDLE_PRIO, DD_WRITE, write2);
+#undef DEADLINE_DEBUGFS_DDIR_ATTRS
+
+static int deadline_batching_show(void *data, struct seq_file *m)
+{
+	struct request_queue *q = data;
+	struct deadline_data *dd = q->elevator->elevator_data;
+
+	seq_printf(m, "%u\n", dd->batching);
+	return 0;
+}
+
+static int deadline_starved_show(void *data, struct seq_file *m)
+{
+	struct request_queue *q = data;
+	struct deadline_data *dd = q->elevator->elevator_data;
+
+	seq_printf(m, "%u\n", dd->starved);
+	return 0;
+}
+
+static int dd_async_depth_show(void *data, struct seq_file *m)
+{
+	struct request_queue *q = data;
+	struct deadline_data *dd = q->elevator->elevator_data;
+
+	seq_printf(m, "%u\n", dd->async_depth);
+	return 0;
+}
+
+static int dd_queued_show(void *data, struct seq_file *m)
+{
+	struct request_queue *q = data;
+	struct deadline_data *dd = q->elevator->elevator_data;
+
+	seq_printf(m, "%u %u %u\n", dd_queued(dd, DD_RT_PRIO),
+		   dd_queued(dd, DD_BE_PRIO),
+		   dd_queued(dd, DD_IDLE_PRIO));
+	return 0;
+}
+
+/* Number of requests owned by the block driver for a given priority. */
+static u32 dd_owned_by_driver(struct deadline_data *dd, enum dd_prio prio)
+{
+	return dd_sum(dd, dispatched, prio) + dd_sum(dd, merged, prio)
+		- dd_sum(dd, completed, prio);
+}
+
+static int dd_owned_by_driver_show(void *data, struct seq_file *m)
+{
+	struct request_queue *q = data;
+	struct deadline_data *dd = q->elevator->elevator_data;
+
+	seq_printf(m, "%u %u %u\n", dd_owned_by_driver(dd, DD_RT_PRIO),
+		   dd_owned_by_driver(dd, DD_BE_PRIO),
+		   dd_owned_by_driver(dd, DD_IDLE_PRIO));
+	return 0;
+}
+
+#define DEADLINE_DISPATCH_ATTR(prio)					\
+static void *deadline_dispatch##prio##_start(struct seq_file *m,	\
+					     loff_t *pos)		\
+	__acquires(&dd->lock)						\
+{									\
+	struct request_queue *q = m->private;				\
+	struct deadline_data *dd = q->elevator->elevator_data;		\
+	struct dd_per_prio *per_prio = &dd->per_prio[prio];		\
+									\
+	spin_lock(&dd->lock);						\
+	return seq_list_start(&per_prio->dispatch, *pos);		\
+}									\
+									\
+static void *deadline_dispatch##prio##_next(struct seq_file *m,		\
+					    void *v, loff_t *pos)	\
+{									\
+	struct request_queue *q = m->private;				\
+	struct deadline_data *dd = q->elevator->elevator_data;		\
+	struct dd_per_prio *per_prio = &dd->per_prio[prio];		\
+									\
+	return seq_list_next(v, &per_prio->dispatch, pos);		\
+}									\
+									\
+static void deadline_dispatch##prio##_stop(struct seq_file *m, void *v)	\
+	__releases(&dd->lock)						\
+{									\
+	struct request_queue *q = m->private;				\
+	struct deadline_data *dd = q->elevator->elevator_data;		\
+									\
+	spin_unlock(&dd->lock);						\
+}									\
+									\
+static const struct seq_operations deadline_dispatch##prio##_seq_ops = { \
+	.start	= deadline_dispatch##prio##_start,			\
+	.next	= deadline_dispatch##prio##_next,			\
+	.stop	= deadline_dispatch##prio##_stop,			\
+	.show	= blk_mq_debugfs_rq_show,				\
+}
+
+DEADLINE_DISPATCH_ATTR(0);
+DEADLINE_DISPATCH_ATTR(1);
+DEADLINE_DISPATCH_ATTR(2);
+#undef DEADLINE_DISPATCH_ATTR
+
+#define DEADLINE_QUEUE_DDIR_ATTRS(name)					\
+	{#name "_fifo_list", 0400,					\
+			.seq_ops = &deadline_##name##_fifo_seq_ops}
+#define DEADLINE_NEXT_RQ_ATTR(name)					\
+	{#name "_next_rq", 0400, deadline_##name##_next_rq_show}
+static const struct blk_mq_debugfs_attr deadline_queue_debugfs_attrs[] = {
+	DEADLINE_QUEUE_DDIR_ATTRS(read0),
+	DEADLINE_QUEUE_DDIR_ATTRS(write0),
+	DEADLINE_QUEUE_DDIR_ATTRS(read1),
+	DEADLINE_QUEUE_DDIR_ATTRS(write1),
+	DEADLINE_QUEUE_DDIR_ATTRS(read2),
+	DEADLINE_QUEUE_DDIR_ATTRS(write2),
+	DEADLINE_NEXT_RQ_ATTR(read0),
+	DEADLINE_NEXT_RQ_ATTR(write0),
+	DEADLINE_NEXT_RQ_ATTR(read1),
+	DEADLINE_NEXT_RQ_ATTR(write1),
+	DEADLINE_NEXT_RQ_ATTR(read2),
+	DEADLINE_NEXT_RQ_ATTR(write2),
+	{"batching", 0400, deadline_batching_show},
+	{"starved", 0400, deadline_starved_show},
+	{"async_depth", 0400, dd_async_depth_show},
+	{"dispatch0", 0400, .seq_ops = &deadline_dispatch0_seq_ops},
+	{"dispatch1", 0400, .seq_ops = &deadline_dispatch1_seq_ops},
+	{"dispatch2", 0400, .seq_ops = &deadline_dispatch2_seq_ops},
+	{"owned_by_driver", 0400, dd_owned_by_driver_show},
+	{"queued", 0400, dd_queued_show},
+	{},
+};
+#undef DEADLINE_QUEUE_DDIR_ATTRS
+#endif
+
+static struct elevator_type mq_deadline = {
+	.ops = {
+		.depth_updated		= dd_depth_updated,
+		.limit_depth		= dd_limit_depth,
+		.insert_requests	= dd_insert_requests,
+		.dispatch_request	= dd_dispatch_request,
+		.prepare_request	= dd_prepare_request,
+		.finish_request		= dd_finish_request,
+		.next_request		= elv_rb_latter_request,
+		.former_request		= elv_rb_former_request,
+		.bio_merge		= dd_bio_merge,
+		.request_merge		= dd_request_merge,
+		.requests_merged	= dd_merged_requests,
+		.request_merged		= dd_request_merged,
+		.has_work		= dd_has_work,
+		.init_sched		= dd_init_sched,
+		.exit_sched		= dd_exit_sched,
+		.init_hctx		= dd_init_hctx,
+	},
+
+#ifdef CONFIG_BLK_DEBUG_FS
+	.queue_debugfs_attrs = deadline_queue_debugfs_attrs,
+#endif
+	.elevator_attrs = deadline_attrs,
+	.elevator_name = "mq-deadline",
+	.elevator_alias = "deadline",
+	.elevator_features = ELEVATOR_F_ZBD_SEQ_WRITE,
+	.elevator_owner = THIS_MODULE,
+};
+MODULE_ALIAS("mq-deadline-iosched");
+
+static int __init deadline_init(void)
+{
+	return elv_register(&mq_deadline);
+}
+
+static void __exit deadline_exit(void)
+{
+	elv_unregister(&mq_deadline);
+}
+
+module_init(deadline_init);
+module_exit(deadline_exit);
+
+MODULE_AUTHOR("Jens Axboe, Damien Le Moal and Bart Van Assche");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("MQ deadline IO scheduler");