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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // 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/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-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 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];
     /* Next request in FIFO order. Read, write or both are NULL. */
     struct request *next_rq[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 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];
 
     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)
 {
     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)
 {
     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 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;
 }
 
 /*
  * 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);
         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 (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].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;
 
     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];
         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,
                   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];
     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)) {
         blk_mq_free_requests(&free);
         return;
     }
 
     trace_block_rq_insert(rq);
 
     if (at_head) {
         list_add(&rq->queuelist, &per_prio->dispatch);
         rq->fifo_time = jiffies;
     } 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);
 }
 
 /* Callback from inside blk_mq_rq_ctx_init(). */
 static void dd_prepare_request(struct request *rq)
 {
     rq->elv.priv[0] = NULL;
 }
 
 /*
  * 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);
         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_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 = 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;
     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");

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