// 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/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 "elevator.h"
#include "blk.h"
#include "blk-mq.h"
#include "blk-mq-debugfs.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 prio_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. It is fine if these counters overflow.
 * What matters is that these counters are at least as wide as
 * log2(max_outstanding_requests).
 */
struct io_stats_per_prio {
        uint32_t inserted;
        uint32_t merged;
        uint32_t dispatched;
        atomic_t completed;
};

/*
 * 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];
        /* Position of the most recently dispatched request. */
        sector_t latest_pos[DD_DIR_COUNT];
        struct io_stats_per_prio stats;
};

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 */

        /*
         * 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 prio_aging_expire;

        spinlock_t lock;
        spinlock_t zone_lock;
};

/* 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 before `rq' in sector-sorted order
 */
static inline struct request *
deadline_earlier_request(struct request *rq)
{
        struct rb_node *node = rb_prev(&rq->rb_node);

        if (node)
                return rb_entry_rq(node);

        return NULL;
}

/*
 * 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;
}

/*
 * Return the first request for which blk_rq_pos() >= @pos. For zoned devices,
 * return the first request after the start of the zone containing @pos.
 */
static inline struct request *deadline_from_pos(struct dd_per_prio *per_prio,
                                enum dd_data_dir data_dir, sector_t pos)
{
        struct rb_node *node = per_prio->sort_list[data_dir].rb_node;
        struct request *rq, *res = NULL;

        if (!node)
                return NULL;

        rq = rb_entry_rq(node);
        /*
         * A zoned write may have been requeued with a starting position that
         * is below that of the most recently dispatched request. Hence, for
         * zoned writes, start searching from the start of a zone.
         */
        if (blk_rq_is_seq_zoned_write(rq))
                pos = round_down(pos, rq->q->limits.chunk_sectors);

        while (node) {
                rq = rb_entry_rq(node);
                if (blk_rq_pos(rq) >= pos) {
                        res = rq;
                        node = node->rb_left;
                } else {
                        node = node->rb_right;
                }
        }
        return res;
}

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)
{
        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];

        lockdep_assert_held(&dd->lock);

        dd->per_prio[prio].stats.merged++;

        /*
         * 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)
{
        /*
         * 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)
{
        const struct io_stats_per_prio *stats = &dd->per_prio[prio].stats;

        lockdep_assert_held(&dd->lock);

        return stats->inserted - atomic_read(&stats->completed);
}

/*
 * deadline_check_fifo returns true if and only if there are expired requests
 * in the FIFO list. Requires !list_empty(&dd->fifo_list[data_dir]).
 */
static inline bool 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);

        return time_is_before_eq_jiffies((unsigned long)rq->fifo_time);
}

/*
 * Check if rq has a sequential request preceding it.
 */
static bool deadline_is_seq_write(struct deadline_data *dd, struct request *rq)
{
        struct request *prev = deadline_earlier_request(rq);

        if (!prev)
                return false;

        return blk_rq_pos(prev) + blk_rq_sectors(prev) == blk_rq_pos(rq);
}

/*
 * Skip all write requests that are sequential from @rq, even if we cross
 * a zone boundary.
 */
static struct request *deadline_skip_seq_writes(struct deadline_data *dd,
                                                struct request *rq)
{
        sector_t pos = blk_rq_pos(rq);

        do {
                pos += blk_rq_sectors(rq);
                rq = deadline_latter_request(rq);
        } while (rq && blk_rq_pos(rq) == pos);

        return rq;
}

/*
 * 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, *rb_rq, *next;
        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. For some HDDs, breaking a sequential
         * write stream can lead to lower throughput, so make sure to preserve
         * sequential write streams, even if that stream crosses into the next
         * zones and these zones are unlocked.
         */
        spin_lock_irqsave(&dd->zone_lock, flags);
        list_for_each_entry_safe(rq, next, &per_prio->fifo_list[DD_WRITE],
                                 queuelist) {
                /* Check whether a prior request exists for the same zone. */
                rb_rq = deadline_from_pos(per_prio, data_dir, blk_rq_pos(rq));
                if (rb_rq && blk_rq_pos(rb_rq) < blk_rq_pos(rq))
                        rq = rb_rq;
                if (blk_req_can_dispatch_to_zone(rq) &&
                    (blk_queue_nonrot(rq->q) ||
                     !deadline_is_seq_write(dd, 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 = deadline_from_pos(per_prio, data_dir,
                               per_prio->latest_pos[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. For some HDDs, breaking a sequential
         * write stream can lead to lower throughput, so make sure to preserve
         * sequential write streams, even if that stream crosses into the next
         * zones and these zones are unlocked.
         */
        spin_lock_irqsave(&dd->zone_lock, flags);
        while (rq) {
                if (blk_req_can_dispatch_to_zone(rq))
                        break;
                if (blk_queue_nonrot(rq->q))
                        rq = deadline_latter_request(rq);
                else
                        rq = deadline_skip_seq_writes(dd, rq);
        }
        spin_unlock_irqrestore(&dd->zone_lock, flags);

        return rq;
}

/*
 * Returns true if and only if @rq started after @latest_start where
 * @latest_start is in jiffies.
 */
static bool started_after(struct deadline_data *dd, struct request *rq,
                          unsigned long latest_start)
{
        unsigned long start_time = (unsigned long)rq->fifo_time;

        start_time -= dd->fifo_expire[rq_data_dir(rq)];

        return time_after(start_time, latest_start);
}

/*
 * deadline_dispatch_requests selects the best request according to
 * read/write expire, fifo_batch, etc and with a start time <= @latest_start.
 */
static struct request *__dd_dispatch_request(struct deadline_data *dd,
                                             struct dd_per_prio *per_prio,
                                             unsigned long latest_start)
{
        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 (started_after(dd, rq, latest_start))
                        return NULL;
                list_del_init(&rq->queuelist);
                data_dir = rq_data_dir(rq);
                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 and are still entitled to batch */
                data_dir = rq_data_dir(rq);
                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 (started_after(dd, rq, latest_start))
                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->per_prio[prio].latest_pos[data_dir] = blk_rq_pos(rq);
        dd->per_prio[prio].stats.dispatched++;
        /*
         * If the request needs its target zone locked, do it.
         */
        blk_req_zone_write_lock(rq);
        rq->rq_flags |= RQF_STARTED;
        return rq;
}

/*
 * Check whether there are any requests with priority other than DD_RT_PRIO
 * that were inserted more than prio_aging_expire jiffies ago.
 */
static struct request *dd_dispatch_prio_aged_requests(struct deadline_data *dd,
                                                      unsigned long now)
{
        struct request *rq;
        enum dd_prio prio;
        int prio_cnt;

        lockdep_assert_held(&dd->lock);

        prio_cnt = !!dd_queued(dd, DD_RT_PRIO) + !!dd_queued(dd, DD_BE_PRIO) +
                   !!dd_queued(dd, DD_IDLE_PRIO);
        if (prio_cnt < 2)
                return NULL;

        for (prio = DD_BE_PRIO; prio <= DD_PRIO_MAX; prio++) {
                rq = __dd_dispatch_request(dd, &dd->per_prio[prio],
                                           now - dd->prio_aging_expire);
                if (rq)
                        return rq;
        }

        return NULL;
}

/*
 * 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 unsigned long now = jiffies;
        struct request *rq;
        enum dd_prio prio;

        spin_lock(&dd->lock);
        rq = dd_dispatch_prio_aged_requests(dd, now);
        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);
                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(blk_opf_t opf, struct blk_mq_alloc_data *data)
{
        struct deadline_data *dd = data->q->elevator->elevator_data;

        /* Do not throttle synchronous reads. */
        if (op_is_sync(opf) && !op_is_write(opf))
                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;
        unsigned int shift = tags->bitmap_tags.sb.shift;

        dd->async_depth = max(1U, 3 * (1U << shift)  / 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];
                const struct io_stats_per_prio *stats = &per_prio->stats;
                uint32_t queued;

                WARN_ON_ONCE(!list_empty(&per_prio->fifo_list[DD_READ]));
                WARN_ON_ONCE(!list_empty(&per_prio->fifo_list[DD_WRITE]));

                spin_lock(&dd->lock);
                queued = dd_queued(dd, prio);
                spin_unlock(&dd->lock);

                WARN_ONCE(queued != 0,
                          "statistics for priority %d: i %u m %u d %u c %u\n",
                          prio, stats->inserted, stats->merged,
                          stats->dispatched, atomic_read(&stats->completed));
        }

        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;

        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->prio_aging_expire = prio_aging_expire;
        spin_lock_init(&dd->lock);
        spin_lock_init(&dd->zone_lock);

        /* We dispatch from request queue wide instead of hw queue */
        blk_queue_flag_set(QUEUE_FLAG_SQ_SCHED, q);

        q->elevator = eq;
        return 0;

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;
                        if (blk_discard_mergable(__rq))
                                return ELEVATOR_DISCARD_MERGE;
                        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,
                              blk_insert_t flags, struct list_head *free)
{
        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];
        per_prio = &dd->per_prio[prio];
        if (!rq->elv.priv[0]) {
                per_prio->stats.inserted++;
                rq->elv.priv[0] = (void *)(uintptr_t)1;
        }

        if (blk_mq_sched_try_insert_merge(q, rq, free))
                return;

        trace_block_rq_insert(rq);

        if (flags & BLK_MQ_INSERT_AT_HEAD) {
                list_add(&rq->queuelist, &per_prio->dispatch);
                rq->fifo_time = jiffies;
        } else {
                struct list_head *insert_before;

                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];
                insert_before = &per_prio->fifo_list[data_dir];
#ifdef CONFIG_BLK_DEV_ZONED
                /*
                 * Insert zoned writes such that requests are sorted by
                 * position per zone.
                 */
                if (blk_rq_is_seq_zoned_write(rq)) {
                        struct request *rq2 = deadline_latter_request(rq);

                        if (rq2 && blk_rq_zone_no(rq2) == blk_rq_zone_no(rq))
                                insert_before = &rq2->queuelist;
                }
#endif
                list_add_tail(&rq->queuelist, insert_before);
        }
}

/*
 * Called from blk_mq_insert_request() or blk_mq_dispatch_plug_list().
 */
static void dd_insert_requests(struct blk_mq_hw_ctx *hctx,
                               struct list_head *list,
                               blk_insert_t flags)
{
        struct request_queue *q = hctx->queue;
        struct deadline_data *dd = q->elevator->elevator_data;
        LIST_HEAD(free);

        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, flags, &free);
        }
        spin_unlock(&dd->lock);

        blk_mq_free_requests(&free);
}

/* Callback from inside blk_mq_rq_ctx_init(). */
static void dd_prepare_request(struct request *rq)
{
        rq->elv.priv[0] = NULL;
}

static bool dd_has_write_work(struct blk_mq_hw_ctx *hctx)
{
        struct deadline_data *dd = hctx->queue->elevator->elevator_data;
        enum dd_prio p;

        for (p = 0; p <= DD_PRIO_MAX; p++)
                if (!list_empty_careful(&dd->per_prio[p].fifo_list[DD_WRITE]))
                        return true;

        return false;
}

/*
 * 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];

        /*
         * The block layer core may call dd_finish_request() without having
         * called dd_insert_requests(). Skip requests that bypassed I/O
         * scheduling. See also blk_mq_request_bypass_insert().
         */
        if (!rq->elv.priv[0])
                return;

        atomic_inc(&per_prio->stats.completed);

        if (blk_queue_is_zoned(q)) {
                unsigned long flags;

                spin_lock_irqsave(&dd->zone_lock, flags);
                blk_req_zone_write_unlock(rq);
                spin_unlock_irqrestore(&dd->zone_lock, flags);

                if (dd_has_write_work(rq->mq_hctx))
                        blk_mq_sched_mark_restart_hctx(rq->mq_hctx);
        }
}

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_prio_aging_expire_show, dd->prio_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->async_depth);
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_prio_aging_expire_store, &dd->prio_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->async_depth, 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(prio_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;                                             \
                                                                        \
        rq = deadline_from_pos(per_prio, data_dir,                      \
                               per_prio->latest_pos[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;
        u32 rt, be, idle;

        spin_lock(&dd->lock);
        rt = dd_queued(dd, DD_RT_PRIO);
        be = dd_queued(dd, DD_BE_PRIO);
        idle = dd_queued(dd, DD_IDLE_PRIO);
        spin_unlock(&dd->lock);

        seq_printf(m, "%u %u %u\n", rt, be, idle);

        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)
{
        const struct io_stats_per_prio *stats = &dd->per_prio[prio].stats;

        lockdep_assert_held(&dd->lock);

        return stats->dispatched + stats->merged -
                atomic_read(&stats->completed);
}

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;
        u32 rt, be, idle;

        spin_lock(&dd->lock);
        rt = dd_owned_by_driver(dd, DD_RT_PRIO);
        be = dd_owned_by_driver(dd, DD_BE_PRIO);
        idle = dd_owned_by_driver(dd, DD_IDLE_PRIO);
        spin_unlock(&dd->lock);

        seq_printf(m, "%u %u %u\n", rt, be, idle);

        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");