block/mq-deadline: Add cgroup support

Maintain statistics per cgroup and export these to user space. These
statistics are essential for verifying whether the proper I/O priorities
have been assigned to requests. An example of the statistics data with
this patch applied:

$ cat /sys/fs/cgroup/io.stat
11:2 rbytes=0 wbytes=0 rios=3 wios=0 dbytes=0 dios=0 [NONE] dispatched=0 inserted=0 merged=171 [RT] dispatched=0 inserted=0 merged=0 [BE] dispatched=0 inserted=0 merged=0 [IDLE] dispatched=0 inserted=0 merged=0
8:32 rbytes=2142720 wbytes=0 rios=105 wios=0 dbytes=0 dios=0 [NONE] dispatched=0 inserted=0 merged=171 [RT] dispatched=0 inserted=0 merged=0 [BE] dispatched=0 inserted=0 merged=0 [IDLE] dispatched=0 inserted=0 merged=0

Cc: Damien Le Moal <damien.lemoal@wdc.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Cc: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20210618004456.7280-16-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 0 insertions, 1095 deletions

diff --git a/block/mq-deadline.c b/block/mq-deadline.c
deleted file mode 100644
index 04d9d6b3745b..000000000000
--- a/block/mq-deadline.c
+++ /dev/null
@@ -1,1095 +0,0 @@
-// 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! */
-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;
-
-	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
- */
-static struct request *__dd_dispatch_request(struct deadline_data *dd,
-					     struct dd_per_prio *per_prio)
-{
-	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);
-		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:
-	/*
-	 * 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;
-	struct request *rq;
-	enum dd_prio prio;
-
-	spin_lock(&dd->lock);
-	for (prio = 0; prio <= DD_PRIO_MAX; prio++) {
-		rq = __dd_dispatch_request(dd, &dd->per_prio[prio]);
-		if (rq)
-			break;
-	}
-	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;
-	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;
-
-	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))
-		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_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_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),
-	__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");