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TOMOYO Linux Cross Reference
Linux/block/mq-deadline.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  *  MQ Deadline i/o scheduler - adaptation of the legacy deadline scheduler,
  4  *  for the blk-mq scheduling framework
  5  *
  6  *  Copyright (C) 2016 Jens Axboe <axboe@kernel.dk>
  7  */
  8 #include <linux/kernel.h>
  9 #include <linux/fs.h>
 10 #include <linux/blkdev.h>
 11 #include <linux/blk-mq.h>
 12 #include <linux/bio.h>
 13 #include <linux/module.h>
 14 #include <linux/slab.h>
 15 #include <linux/init.h>
 16 #include <linux/compiler.h>
 17 #include <linux/rbtree.h>
 18 #include <linux/sbitmap.h>
 19 
 20 #include <trace/events/block.h>
 21 
 22 #include "elevator.h"
 23 #include "blk.h"
 24 #include "blk-mq.h"
 25 #include "blk-mq-debugfs.h"
 26 #include "blk-mq-tag.h"
 27 #include "blk-mq-sched.h"
 28 
 29 /*
 30  * See Documentation/block/deadline-iosched.rst
 31  */
 32 static const int read_expire = HZ / 2;  /* max time before a read is submitted. */
 33 static const int write_expire = 5 * HZ; /* ditto for writes, these limits are SOFT! */
 34 /*
 35  * Time after which to dispatch lower priority requests even if higher
 36  * priority requests are pending.
 37  */
 38 static const int prio_aging_expire = 10 * HZ;
 39 static const int writes_starved = 2;    /* max times reads can starve a write */
 40 static const int fifo_batch = 16;       /* # of sequential requests treated as one
 41                                      by the above parameters. For throughput. */
 42 
 43 enum dd_data_dir {
 44         DD_READ         = READ,
 45         DD_WRITE        = WRITE,
 46 };
 47 
 48 enum { DD_DIR_COUNT = 2 };
 49 
 50 enum dd_prio {
 51         DD_RT_PRIO      = 0,
 52         DD_BE_PRIO      = 1,
 53         DD_IDLE_PRIO    = 2,
 54         DD_PRIO_MAX     = 2,
 55 };
 56 
 57 enum { DD_PRIO_COUNT = 3 };
 58 
 59 /*
 60  * I/O statistics per I/O priority. It is fine if these counters overflow.
 61  * What matters is that these counters are at least as wide as
 62  * log2(max_outstanding_requests).
 63  */
 64 struct io_stats_per_prio {
 65         uint32_t inserted;
 66         uint32_t merged;
 67         uint32_t dispatched;
 68         atomic_t completed;
 69 };
 70 
 71 /*
 72  * Deadline scheduler data per I/O priority (enum dd_prio). Requests are
 73  * present on both sort_list[] and fifo_list[].
 74  */
 75 struct dd_per_prio {
 76         struct list_head dispatch;
 77         struct rb_root sort_list[DD_DIR_COUNT];
 78         struct list_head fifo_list[DD_DIR_COUNT];
 79         /* Next request in FIFO order. Read, write or both are NULL. */
 80         struct request *next_rq[DD_DIR_COUNT];
 81         struct io_stats_per_prio stats;
 82 };
 83 
 84 struct deadline_data {
 85         /*
 86          * run time data
 87          */
 88 
 89         struct dd_per_prio per_prio[DD_PRIO_COUNT];
 90 
 91         /* Data direction of latest dispatched request. */
 92         enum dd_data_dir last_dir;
 93         unsigned int batching;          /* number of sequential requests made */
 94         unsigned int starved;           /* times reads have starved writes */
 95 
 96         /*
 97          * settings that change how the i/o scheduler behaves
 98          */
 99         int fifo_expire[DD_DIR_COUNT];
100         int fifo_batch;
101         int writes_starved;
102         int front_merges;
103         u32 async_depth;
104         int prio_aging_expire;
105 
106         spinlock_t lock;
107         spinlock_t zone_lock;
108 };
109 
110 /* Maps an I/O priority class to a deadline scheduler priority. */
111 static const enum dd_prio ioprio_class_to_prio[] = {
112         [IOPRIO_CLASS_NONE]     = DD_BE_PRIO,
113         [IOPRIO_CLASS_RT]       = DD_RT_PRIO,
114         [IOPRIO_CLASS_BE]       = DD_BE_PRIO,
115         [IOPRIO_CLASS_IDLE]     = DD_IDLE_PRIO,
116 };
117 
118 static inline struct rb_root *
119 deadline_rb_root(struct dd_per_prio *per_prio, struct request *rq)
120 {
121         return &per_prio->sort_list[rq_data_dir(rq)];
122 }
123 
124 /*
125  * Returns the I/O priority class (IOPRIO_CLASS_*) that has been assigned to a
126  * request.
127  */
128 static u8 dd_rq_ioclass(struct request *rq)
129 {
130         return IOPRIO_PRIO_CLASS(req_get_ioprio(rq));
131 }
132 
133 /*
134  * get the request after `rq' in sector-sorted order
135  */
136 static inline struct request *
137 deadline_latter_request(struct request *rq)
138 {
139         struct rb_node *node = rb_next(&rq->rb_node);
140 
141         if (node)
142                 return rb_entry_rq(node);
143 
144         return NULL;
145 }
146 
147 static void
148 deadline_add_rq_rb(struct dd_per_prio *per_prio, struct request *rq)
149 {
150         struct rb_root *root = deadline_rb_root(per_prio, rq);
151 
152         elv_rb_add(root, rq);
153 }
154 
155 static inline void
156 deadline_del_rq_rb(struct dd_per_prio *per_prio, struct request *rq)
157 {
158         const enum dd_data_dir data_dir = rq_data_dir(rq);
159 
160         if (per_prio->next_rq[data_dir] == rq)
161                 per_prio->next_rq[data_dir] = deadline_latter_request(rq);
162 
163         elv_rb_del(deadline_rb_root(per_prio, rq), rq);
164 }
165 
166 /*
167  * remove rq from rbtree and fifo.
168  */
169 static void deadline_remove_request(struct request_queue *q,
170                                     struct dd_per_prio *per_prio,
171                                     struct request *rq)
172 {
173         list_del_init(&rq->queuelist);
174 
175         /*
176          * We might not be on the rbtree, if we are doing an insert merge
177          */
178         if (!RB_EMPTY_NODE(&rq->rb_node))
179                 deadline_del_rq_rb(per_prio, rq);
180 
181         elv_rqhash_del(q, rq);
182         if (q->last_merge == rq)
183                 q->last_merge = NULL;
184 }
185 
186 static void dd_request_merged(struct request_queue *q, struct request *req,
187                               enum elv_merge type)
188 {
189         struct deadline_data *dd = q->elevator->elevator_data;
190         const u8 ioprio_class = dd_rq_ioclass(req);
191         const enum dd_prio prio = ioprio_class_to_prio[ioprio_class];
192         struct dd_per_prio *per_prio = &dd->per_prio[prio];
193 
194         /*
195          * if the merge was a front merge, we need to reposition request
196          */
197         if (type == ELEVATOR_FRONT_MERGE) {
198                 elv_rb_del(deadline_rb_root(per_prio, req), req);
199                 deadline_add_rq_rb(per_prio, req);
200         }
201 }
202 
203 /*
204  * Callback function that is invoked after @next has been merged into @req.
205  */
206 static void dd_merged_requests(struct request_queue *q, struct request *req,
207                                struct request *next)
208 {
209         struct deadline_data *dd = q->elevator->elevator_data;
210         const u8 ioprio_class = dd_rq_ioclass(next);
211         const enum dd_prio prio = ioprio_class_to_prio[ioprio_class];
212 
213         lockdep_assert_held(&dd->lock);
214 
215         dd->per_prio[prio].stats.merged++;
216 
217         /*
218          * if next expires before rq, assign its expire time to rq
219          * and move into next position (next will be deleted) in fifo
220          */
221         if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) {
222                 if (time_before((unsigned long)next->fifo_time,
223                                 (unsigned long)req->fifo_time)) {
224                         list_move(&req->queuelist, &next->queuelist);
225                         req->fifo_time = next->fifo_time;
226                 }
227         }
228 
229         /*
230          * kill knowledge of next, this one is a goner
231          */
232         deadline_remove_request(q, &dd->per_prio[prio], next);
233 }
234 
235 /*
236  * move an entry to dispatch queue
237  */
238 static void
239 deadline_move_request(struct deadline_data *dd, struct dd_per_prio *per_prio,
240                       struct request *rq)
241 {
242         const enum dd_data_dir data_dir = rq_data_dir(rq);
243 
244         per_prio->next_rq[data_dir] = deadline_latter_request(rq);
245 
246         /*
247          * take it off the sort and fifo list
248          */
249         deadline_remove_request(rq->q, per_prio, rq);
250 }
251 
252 /* Number of requests queued for a given priority level. */
253 static u32 dd_queued(struct deadline_data *dd, enum dd_prio prio)
254 {
255         const struct io_stats_per_prio *stats = &dd->per_prio[prio].stats;
256 
257         lockdep_assert_held(&dd->lock);
258 
259         return stats->inserted - atomic_read(&stats->completed);
260 }
261 
262 /*
263  * deadline_check_fifo returns 0 if there are no expired requests on the fifo,
264  * 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
265  */
266 static inline int deadline_check_fifo(struct dd_per_prio *per_prio,
267                                       enum dd_data_dir data_dir)
268 {
269         struct request *rq = rq_entry_fifo(per_prio->fifo_list[data_dir].next);
270 
271         /*
272          * rq is expired!
273          */
274         if (time_after_eq(jiffies, (unsigned long)rq->fifo_time))
275                 return 1;
276 
277         return 0;
278 }
279 
280 /*
281  * For the specified data direction, return the next request to
282  * dispatch using arrival ordered lists.
283  */
284 static struct request *
285 deadline_fifo_request(struct deadline_data *dd, struct dd_per_prio *per_prio,
286                       enum dd_data_dir data_dir)
287 {
288         struct request *rq;
289         unsigned long flags;
290 
291         if (list_empty(&per_prio->fifo_list[data_dir]))
292                 return NULL;
293 
294         rq = rq_entry_fifo(per_prio->fifo_list[data_dir].next);
295         if (data_dir == DD_READ || !blk_queue_is_zoned(rq->q))
296                 return rq;
297 
298         /*
299          * Look for a write request that can be dispatched, that is one with
300          * an unlocked target zone.
301          */
302         spin_lock_irqsave(&dd->zone_lock, flags);
303         list_for_each_entry(rq, &per_prio->fifo_list[DD_WRITE], queuelist) {
304                 if (blk_req_can_dispatch_to_zone(rq))
305                         goto out;
306         }
307         rq = NULL;
308 out:
309         spin_unlock_irqrestore(&dd->zone_lock, flags);
310 
311         return rq;
312 }
313 
314 /*
315  * For the specified data direction, return the next request to
316  * dispatch using sector position sorted lists.
317  */
318 static struct request *
319 deadline_next_request(struct deadline_data *dd, struct dd_per_prio *per_prio,
320                       enum dd_data_dir data_dir)
321 {
322         struct request *rq;
323         unsigned long flags;
324 
325         rq = per_prio->next_rq[data_dir];
326         if (!rq)
327                 return NULL;
328 
329         if (data_dir == DD_READ || !blk_queue_is_zoned(rq->q))
330                 return rq;
331 
332         /*
333          * Look for a write request that can be dispatched, that is one with
334          * an unlocked target zone.
335          */
336         spin_lock_irqsave(&dd->zone_lock, flags);
337         while (rq) {
338                 if (blk_req_can_dispatch_to_zone(rq))
339                         break;
340                 rq = deadline_latter_request(rq);
341         }
342         spin_unlock_irqrestore(&dd->zone_lock, flags);
343 
344         return rq;
345 }
346 
347 /*
348  * Returns true if and only if @rq started after @latest_start where
349  * @latest_start is in jiffies.
350  */
351 static bool started_after(struct deadline_data *dd, struct request *rq,
352                           unsigned long latest_start)
353 {
354         unsigned long start_time = (unsigned long)rq->fifo_time;
355 
356         start_time -= dd->fifo_expire[rq_data_dir(rq)];
357 
358         return time_after(start_time, latest_start);
359 }
360 
361 /*
362  * deadline_dispatch_requests selects the best request according to
363  * read/write expire, fifo_batch, etc and with a start time <= @latest_start.
364  */
365 static struct request *__dd_dispatch_request(struct deadline_data *dd,
366                                              struct dd_per_prio *per_prio,
367                                              unsigned long latest_start)
368 {
369         struct request *rq, *next_rq;
370         enum dd_data_dir data_dir;
371         enum dd_prio prio;
372         u8 ioprio_class;
373 
374         lockdep_assert_held(&dd->lock);
375 
376         if (!list_empty(&per_prio->dispatch)) {
377                 rq = list_first_entry(&per_prio->dispatch, struct request,
378                                       queuelist);
379                 if (started_after(dd, rq, latest_start))
380                         return NULL;
381                 list_del_init(&rq->queuelist);
382                 goto done;
383         }
384 
385         /*
386          * batches are currently reads XOR writes
387          */
388         rq = deadline_next_request(dd, per_prio, dd->last_dir);
389         if (rq && dd->batching < dd->fifo_batch)
390                 /* we have a next request are still entitled to batch */
391                 goto dispatch_request;
392 
393         /*
394          * at this point we are not running a batch. select the appropriate
395          * data direction (read / write)
396          */
397 
398         if (!list_empty(&per_prio->fifo_list[DD_READ])) {
399                 BUG_ON(RB_EMPTY_ROOT(&per_prio->sort_list[DD_READ]));
400 
401                 if (deadline_fifo_request(dd, per_prio, DD_WRITE) &&
402                     (dd->starved++ >= dd->writes_starved))
403                         goto dispatch_writes;
404 
405                 data_dir = DD_READ;
406 
407                 goto dispatch_find_request;
408         }
409 
410         /*
411          * there are either no reads or writes have been starved
412          */
413 
414         if (!list_empty(&per_prio->fifo_list[DD_WRITE])) {
415 dispatch_writes:
416                 BUG_ON(RB_EMPTY_ROOT(&per_prio->sort_list[DD_WRITE]));
417 
418                 dd->starved = 0;
419 
420                 data_dir = DD_WRITE;
421 
422                 goto dispatch_find_request;
423         }
424 
425         return NULL;
426 
427 dispatch_find_request:
428         /*
429          * we are not running a batch, find best request for selected data_dir
430          */
431         next_rq = deadline_next_request(dd, per_prio, data_dir);
432         if (deadline_check_fifo(per_prio, data_dir) || !next_rq) {
433                 /*
434                  * A deadline has expired, the last request was in the other
435                  * direction, or we have run out of higher-sectored requests.
436                  * Start again from the request with the earliest expiry time.
437                  */
438                 rq = deadline_fifo_request(dd, per_prio, data_dir);
439         } else {
440                 /*
441                  * The last req was the same dir and we have a next request in
442                  * sort order. No expired requests so continue on from here.
443                  */
444                 rq = next_rq;
445         }
446 
447         /*
448          * For a zoned block device, if we only have writes queued and none of
449          * them can be dispatched, rq will be NULL.
450          */
451         if (!rq)
452                 return NULL;
453 
454         dd->last_dir = data_dir;
455         dd->batching = 0;
456 
457 dispatch_request:
458         if (started_after(dd, rq, latest_start))
459                 return NULL;
460 
461         /*
462          * rq is the selected appropriate request.
463          */
464         dd->batching++;
465         deadline_move_request(dd, per_prio, rq);
466 done:
467         ioprio_class = dd_rq_ioclass(rq);
468         prio = ioprio_class_to_prio[ioprio_class];
469         dd->per_prio[prio].stats.dispatched++;
470         /*
471          * If the request needs its target zone locked, do it.
472          */
473         blk_req_zone_write_lock(rq);
474         rq->rq_flags |= RQF_STARTED;
475         return rq;
476 }
477 
478 /*
479  * Check whether there are any requests with priority other than DD_RT_PRIO
480  * that were inserted more than prio_aging_expire jiffies ago.
481  */
482 static struct request *dd_dispatch_prio_aged_requests(struct deadline_data *dd,
483                                                       unsigned long now)
484 {
485         struct request *rq;
486         enum dd_prio prio;
487         int prio_cnt;
488 
489         lockdep_assert_held(&dd->lock);
490 
491         prio_cnt = !!dd_queued(dd, DD_RT_PRIO) + !!dd_queued(dd, DD_BE_PRIO) +
492                    !!dd_queued(dd, DD_IDLE_PRIO);
493         if (prio_cnt < 2)
494                 return NULL;
495 
496         for (prio = DD_BE_PRIO; prio <= DD_PRIO_MAX; prio++) {
497                 rq = __dd_dispatch_request(dd, &dd->per_prio[prio],
498                                            now - dd->prio_aging_expire);
499                 if (rq)
500                         return rq;
501         }
502 
503         return NULL;
504 }
505 
506 /*
507  * Called from blk_mq_run_hw_queue() -> __blk_mq_sched_dispatch_requests().
508  *
509  * One confusing aspect here is that we get called for a specific
510  * hardware queue, but we may return a request that is for a
511  * different hardware queue. This is because mq-deadline has shared
512  * state for all hardware queues, in terms of sorting, FIFOs, etc.
513  */
514 static struct request *dd_dispatch_request(struct blk_mq_hw_ctx *hctx)
515 {
516         struct deadline_data *dd = hctx->queue->elevator->elevator_data;
517         const unsigned long now = jiffies;
518         struct request *rq;
519         enum dd_prio prio;
520 
521         spin_lock(&dd->lock);
522         rq = dd_dispatch_prio_aged_requests(dd, now);
523         if (rq)
524                 goto unlock;
525 
526         /*
527          * Next, dispatch requests in priority order. Ignore lower priority
528          * requests if any higher priority requests are pending.
529          */
530         for (prio = 0; prio <= DD_PRIO_MAX; prio++) {
531                 rq = __dd_dispatch_request(dd, &dd->per_prio[prio], now);
532                 if (rq || dd_queued(dd, prio))
533                         break;
534         }
535 
536 unlock:
537         spin_unlock(&dd->lock);
538 
539         return rq;
540 }
541 
542 /*
543  * Called by __blk_mq_alloc_request(). The shallow_depth value set by this
544  * function is used by __blk_mq_get_tag().
545  */
546 static void dd_limit_depth(unsigned int op, struct blk_mq_alloc_data *data)
547 {
548         struct deadline_data *dd = data->q->elevator->elevator_data;
549 
550         /* Do not throttle synchronous reads. */
551         if (op_is_sync(op) && !op_is_write(op))
552                 return;
553 
554         /*
555          * Throttle asynchronous requests and writes such that these requests
556          * do not block the allocation of synchronous requests.
557          */
558         data->shallow_depth = dd->async_depth;
559 }
560 
561 /* Called by blk_mq_update_nr_requests(). */
562 static void dd_depth_updated(struct blk_mq_hw_ctx *hctx)
563 {
564         struct request_queue *q = hctx->queue;
565         struct deadline_data *dd = q->elevator->elevator_data;
566         struct blk_mq_tags *tags = hctx->sched_tags;
567 
568         dd->async_depth = max(1UL, 3 * q->nr_requests / 4);
569 
570         sbitmap_queue_min_shallow_depth(&tags->bitmap_tags, dd->async_depth);
571 }
572 
573 /* Called by blk_mq_init_hctx() and blk_mq_init_sched(). */
574 static int dd_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
575 {
576         dd_depth_updated(hctx);
577         return 0;
578 }
579 
580 static void dd_exit_sched(struct elevator_queue *e)
581 {
582         struct deadline_data *dd = e->elevator_data;
583         enum dd_prio prio;
584 
585         for (prio = 0; prio <= DD_PRIO_MAX; prio++) {
586                 struct dd_per_prio *per_prio = &dd->per_prio[prio];
587                 const struct io_stats_per_prio *stats = &per_prio->stats;
588                 uint32_t queued;
589 
590                 WARN_ON_ONCE(!list_empty(&per_prio->fifo_list[DD_READ]));
591                 WARN_ON_ONCE(!list_empty(&per_prio->fifo_list[DD_WRITE]));
592 
593                 spin_lock(&dd->lock);
594                 queued = dd_queued(dd, prio);
595                 spin_unlock(&dd->lock);
596 
597                 WARN_ONCE(queued != 0,
598                           "statistics for priority %d: i %u m %u d %u c %u\n",
599                           prio, stats->inserted, stats->merged,
600                           stats->dispatched, atomic_read(&stats->completed));
601         }
602 
603         kfree(dd);
604 }
605 
606 /*
607  * initialize elevator private data (deadline_data).
608  */
609 static int dd_init_sched(struct request_queue *q, struct elevator_type *e)
610 {
611         struct deadline_data *dd;
612         struct elevator_queue *eq;
613         enum dd_prio prio;
614         int ret = -ENOMEM;
615 
616         eq = elevator_alloc(q, e);
617         if (!eq)
618                 return ret;
619 
620         dd = kzalloc_node(sizeof(*dd), GFP_KERNEL, q->node);
621         if (!dd)
622                 goto put_eq;
623 
624         eq->elevator_data = dd;
625 
626         for (prio = 0; prio <= DD_PRIO_MAX; prio++) {
627                 struct dd_per_prio *per_prio = &dd->per_prio[prio];
628 
629                 INIT_LIST_HEAD(&per_prio->dispatch);
630                 INIT_LIST_HEAD(&per_prio->fifo_list[DD_READ]);
631                 INIT_LIST_HEAD(&per_prio->fifo_list[DD_WRITE]);
632                 per_prio->sort_list[DD_READ] = RB_ROOT;
633                 per_prio->sort_list[DD_WRITE] = RB_ROOT;
634         }
635         dd->fifo_expire[DD_READ] = read_expire;
636         dd->fifo_expire[DD_WRITE] = write_expire;
637         dd->writes_starved = writes_starved;
638         dd->front_merges = 1;
639         dd->last_dir = DD_WRITE;
640         dd->fifo_batch = fifo_batch;
641         dd->prio_aging_expire = prio_aging_expire;
642         spin_lock_init(&dd->lock);
643         spin_lock_init(&dd->zone_lock);
644 
645         q->elevator = eq;
646         return 0;
647 
648 put_eq:
649         kobject_put(&eq->kobj);
650         return ret;
651 }
652 
653 /*
654  * Try to merge @bio into an existing request. If @bio has been merged into
655  * an existing request, store the pointer to that request into *@rq.
656  */
657 static int dd_request_merge(struct request_queue *q, struct request **rq,
658                             struct bio *bio)
659 {
660         struct deadline_data *dd = q->elevator->elevator_data;
661         const u8 ioprio_class = IOPRIO_PRIO_CLASS(bio->bi_ioprio);
662         const enum dd_prio prio = ioprio_class_to_prio[ioprio_class];
663         struct dd_per_prio *per_prio = &dd->per_prio[prio];
664         sector_t sector = bio_end_sector(bio);
665         struct request *__rq;
666 
667         if (!dd->front_merges)
668                 return ELEVATOR_NO_MERGE;
669 
670         __rq = elv_rb_find(&per_prio->sort_list[bio_data_dir(bio)], sector);
671         if (__rq) {
672                 BUG_ON(sector != blk_rq_pos(__rq));
673 
674                 if (elv_bio_merge_ok(__rq, bio)) {
675                         *rq = __rq;
676                         if (blk_discard_mergable(__rq))
677                                 return ELEVATOR_DISCARD_MERGE;
678                         return ELEVATOR_FRONT_MERGE;
679                 }
680         }
681 
682         return ELEVATOR_NO_MERGE;
683 }
684 
685 /*
686  * Attempt to merge a bio into an existing request. This function is called
687  * before @bio is associated with a request.
688  */
689 static bool dd_bio_merge(struct request_queue *q, struct bio *bio,
690                 unsigned int nr_segs)
691 {
692         struct deadline_data *dd = q->elevator->elevator_data;
693         struct request *free = NULL;
694         bool ret;
695 
696         spin_lock(&dd->lock);
697         ret = blk_mq_sched_try_merge(q, bio, nr_segs, &free);
698         spin_unlock(&dd->lock);
699 
700         if (free)
701                 blk_mq_free_request(free);
702 
703         return ret;
704 }
705 
706 /*
707  * add rq to rbtree and fifo
708  */
709 static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
710                               bool at_head)
711 {
712         struct request_queue *q = hctx->queue;
713         struct deadline_data *dd = q->elevator->elevator_data;
714         const enum dd_data_dir data_dir = rq_data_dir(rq);
715         u16 ioprio = req_get_ioprio(rq);
716         u8 ioprio_class = IOPRIO_PRIO_CLASS(ioprio);
717         struct dd_per_prio *per_prio;
718         enum dd_prio prio;
719         LIST_HEAD(free);
720 
721         lockdep_assert_held(&dd->lock);
722 
723         /*
724          * This may be a requeue of a write request that has locked its
725          * target zone. If it is the case, this releases the zone lock.
726          */
727         blk_req_zone_write_unlock(rq);
728 
729         prio = ioprio_class_to_prio[ioprio_class];
730         per_prio = &dd->per_prio[prio];
731         if (!rq->elv.priv[0]) {
732                 per_prio->stats.inserted++;
733                 rq->elv.priv[0] = (void *)(uintptr_t)1;
734         }
735 
736         if (blk_mq_sched_try_insert_merge(q, rq, &free)) {
737                 blk_mq_free_requests(&free);
738                 return;
739         }
740 
741         trace_block_rq_insert(rq);
742 
743         if (at_head) {
744                 list_add(&rq->queuelist, &per_prio->dispatch);
745         } else {
746                 deadline_add_rq_rb(per_prio, rq);
747 
748                 if (rq_mergeable(rq)) {
749                         elv_rqhash_add(q, rq);
750                         if (!q->last_merge)
751                                 q->last_merge = rq;
752                 }
753 
754                 /*
755                  * set expire time and add to fifo list
756                  */
757                 rq->fifo_time = jiffies + dd->fifo_expire[data_dir];
758                 list_add_tail(&rq->queuelist, &per_prio->fifo_list[data_dir]);
759         }
760 }
761 
762 /*
763  * Called from blk_mq_sched_insert_request() or blk_mq_sched_insert_requests().
764  */
765 static void dd_insert_requests(struct blk_mq_hw_ctx *hctx,
766                                struct list_head *list, bool at_head)
767 {
768         struct request_queue *q = hctx->queue;
769         struct deadline_data *dd = q->elevator->elevator_data;
770 
771         spin_lock(&dd->lock);
772         while (!list_empty(list)) {
773                 struct request *rq;
774 
775                 rq = list_first_entry(list, struct request, queuelist);
776                 list_del_init(&rq->queuelist);
777                 dd_insert_request(hctx, rq, at_head);
778         }
779         spin_unlock(&dd->lock);
780 }
781 
782 /* Callback from inside blk_mq_rq_ctx_init(). */
783 static void dd_prepare_request(struct request *rq)
784 {
785         rq->elv.priv[0] = NULL;
786 }
787 
788 /*
789  * Callback from inside blk_mq_free_request().
790  *
791  * For zoned block devices, write unlock the target zone of
792  * completed write requests. Do this while holding the zone lock
793  * spinlock so that the zone is never unlocked while deadline_fifo_request()
794  * or deadline_next_request() are executing. This function is called for
795  * all requests, whether or not these requests complete successfully.
796  *
797  * For a zoned block device, __dd_dispatch_request() may have stopped
798  * dispatching requests if all the queued requests are write requests directed
799  * at zones that are already locked due to on-going write requests. To ensure
800  * write request dispatch progress in this case, mark the queue as needing a
801  * restart to ensure that the queue is run again after completion of the
802  * request and zones being unlocked.
803  */
804 static void dd_finish_request(struct request *rq)
805 {
806         struct request_queue *q = rq->q;
807         struct deadline_data *dd = q->elevator->elevator_data;
808         const u8 ioprio_class = dd_rq_ioclass(rq);
809         const enum dd_prio prio = ioprio_class_to_prio[ioprio_class];
810         struct dd_per_prio *per_prio = &dd->per_prio[prio];
811 
812         /*
813          * The block layer core may call dd_finish_request() without having
814          * called dd_insert_requests(). Skip requests that bypassed I/O
815          * scheduling. See also blk_mq_request_bypass_insert().
816          */
817         if (!rq->elv.priv[0])
818                 return;
819 
820         atomic_inc(&per_prio->stats.completed);
821 
822         if (blk_queue_is_zoned(q)) {
823                 unsigned long flags;
824 
825                 spin_lock_irqsave(&dd->zone_lock, flags);
826                 blk_req_zone_write_unlock(rq);
827                 if (!list_empty(&per_prio->fifo_list[DD_WRITE]))
828                         blk_mq_sched_mark_restart_hctx(rq->mq_hctx);
829                 spin_unlock_irqrestore(&dd->zone_lock, flags);
830         }
831 }
832 
833 static bool dd_has_work_for_prio(struct dd_per_prio *per_prio)
834 {
835         return !list_empty_careful(&per_prio->dispatch) ||
836                 !list_empty_careful(&per_prio->fifo_list[DD_READ]) ||
837                 !list_empty_careful(&per_prio->fifo_list[DD_WRITE]);
838 }
839 
840 static bool dd_has_work(struct blk_mq_hw_ctx *hctx)
841 {
842         struct deadline_data *dd = hctx->queue->elevator->elevator_data;
843         enum dd_prio prio;
844 
845         for (prio = 0; prio <= DD_PRIO_MAX; prio++)
846                 if (dd_has_work_for_prio(&dd->per_prio[prio]))
847                         return true;
848 
849         return false;
850 }
851 
852 /*
853  * sysfs parts below
854  */
855 #define SHOW_INT(__FUNC, __VAR)                                         \
856 static ssize_t __FUNC(struct elevator_queue *e, char *page)             \
857 {                                                                       \
858         struct deadline_data *dd = e->elevator_data;                    \
859                                                                         \
860         return sysfs_emit(page, "%d\n", __VAR);                         \
861 }
862 #define SHOW_JIFFIES(__FUNC, __VAR) SHOW_INT(__FUNC, jiffies_to_msecs(__VAR))
863 SHOW_JIFFIES(deadline_read_expire_show, dd->fifo_expire[DD_READ]);
864 SHOW_JIFFIES(deadline_write_expire_show, dd->fifo_expire[DD_WRITE]);
865 SHOW_JIFFIES(deadline_prio_aging_expire_show, dd->prio_aging_expire);
866 SHOW_INT(deadline_writes_starved_show, dd->writes_starved);
867 SHOW_INT(deadline_front_merges_show, dd->front_merges);
868 SHOW_INT(deadline_async_depth_show, dd->front_merges);
869 SHOW_INT(deadline_fifo_batch_show, dd->fifo_batch);
870 #undef SHOW_INT
871 #undef SHOW_JIFFIES
872 
873 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
874 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
875 {                                                                       \
876         struct deadline_data *dd = e->elevator_data;                    \
877         int __data, __ret;                                              \
878                                                                         \
879         __ret = kstrtoint(page, 0, &__data);                            \
880         if (__ret < 0)                                                  \
881                 return __ret;                                           \
882         if (__data < (MIN))                                             \
883                 __data = (MIN);                                         \
884         else if (__data > (MAX))                                        \
885                 __data = (MAX);                                         \
886         *(__PTR) = __CONV(__data);                                      \
887         return count;                                                   \
888 }
889 #define STORE_INT(__FUNC, __PTR, MIN, MAX)                              \
890         STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, )
891 #define STORE_JIFFIES(__FUNC, __PTR, MIN, MAX)                          \
892         STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, msecs_to_jiffies)
893 STORE_JIFFIES(deadline_read_expire_store, &dd->fifo_expire[DD_READ], 0, INT_MAX);
894 STORE_JIFFIES(deadline_write_expire_store, &dd->fifo_expire[DD_WRITE], 0, INT_MAX);
895 STORE_JIFFIES(deadline_prio_aging_expire_store, &dd->prio_aging_expire, 0, INT_MAX);
896 STORE_INT(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX);
897 STORE_INT(deadline_front_merges_store, &dd->front_merges, 0, 1);
898 STORE_INT(deadline_async_depth_store, &dd->front_merges, 1, INT_MAX);
899 STORE_INT(deadline_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX);
900 #undef STORE_FUNCTION
901 #undef STORE_INT
902 #undef STORE_JIFFIES
903 
904 #define DD_ATTR(name) \
905         __ATTR(name, 0644, deadline_##name##_show, deadline_##name##_store)
906 
907 static struct elv_fs_entry deadline_attrs[] = {
908         DD_ATTR(read_expire),
909         DD_ATTR(write_expire),
910         DD_ATTR(writes_starved),
911         DD_ATTR(front_merges),
912         DD_ATTR(async_depth),
913         DD_ATTR(fifo_batch),
914         DD_ATTR(prio_aging_expire),
915         __ATTR_NULL
916 };
917 
918 #ifdef CONFIG_BLK_DEBUG_FS
919 #define DEADLINE_DEBUGFS_DDIR_ATTRS(prio, data_dir, name)               \
920 static void *deadline_##name##_fifo_start(struct seq_file *m,           \
921                                           loff_t *pos)                  \
922         __acquires(&dd->lock)                                           \
923 {                                                                       \
924         struct request_queue *q = m->private;                           \
925         struct deadline_data *dd = q->elevator->elevator_data;          \
926         struct dd_per_prio *per_prio = &dd->per_prio[prio];             \
927                                                                         \
928         spin_lock(&dd->lock);                                           \
929         return seq_list_start(&per_prio->fifo_list[data_dir], *pos);    \
930 }                                                                       \
931                                                                         \
932 static void *deadline_##name##_fifo_next(struct seq_file *m, void *v,   \
933                                          loff_t *pos)                   \
934 {                                                                       \
935         struct request_queue *q = m->private;                           \
936         struct deadline_data *dd = q->elevator->elevator_data;          \
937         struct dd_per_prio *per_prio = &dd->per_prio[prio];             \
938                                                                         \
939         return seq_list_next(v, &per_prio->fifo_list[data_dir], pos);   \
940 }                                                                       \
941                                                                         \
942 static void deadline_##name##_fifo_stop(struct seq_file *m, void *v)    \
943         __releases(&dd->lock)                                           \
944 {                                                                       \
945         struct request_queue *q = m->private;                           \
946         struct deadline_data *dd = q->elevator->elevator_data;          \
947                                                                         \
948         spin_unlock(&dd->lock);                                         \
949 }                                                                       \
950                                                                         \
951 static const struct seq_operations deadline_##name##_fifo_seq_ops = {   \
952         .start  = deadline_##name##_fifo_start,                         \
953         .next   = deadline_##name##_fifo_next,                          \
954         .stop   = deadline_##name##_fifo_stop,                          \
955         .show   = blk_mq_debugfs_rq_show,                               \
956 };                                                                      \
957                                                                         \
958 static int deadline_##name##_next_rq_show(void *data,                   \
959                                           struct seq_file *m)           \
960 {                                                                       \
961         struct request_queue *q = data;                                 \
962         struct deadline_data *dd = q->elevator->elevator_data;          \
963         struct dd_per_prio *per_prio = &dd->per_prio[prio];             \
964         struct request *rq = per_prio->next_rq[data_dir];               \
965                                                                         \
966         if (rq)                                                         \
967                 __blk_mq_debugfs_rq_show(m, rq);                        \
968         return 0;                                                       \
969 }
970 
971 DEADLINE_DEBUGFS_DDIR_ATTRS(DD_RT_PRIO, DD_READ, read0);
972 DEADLINE_DEBUGFS_DDIR_ATTRS(DD_RT_PRIO, DD_WRITE, write0);
973 DEADLINE_DEBUGFS_DDIR_ATTRS(DD_BE_PRIO, DD_READ, read1);
974 DEADLINE_DEBUGFS_DDIR_ATTRS(DD_BE_PRIO, DD_WRITE, write1);
975 DEADLINE_DEBUGFS_DDIR_ATTRS(DD_IDLE_PRIO, DD_READ, read2);
976 DEADLINE_DEBUGFS_DDIR_ATTRS(DD_IDLE_PRIO, DD_WRITE, write2);
977 #undef DEADLINE_DEBUGFS_DDIR_ATTRS
978 
979 static int deadline_batching_show(void *data, struct seq_file *m)
980 {
981         struct request_queue *q = data;
982         struct deadline_data *dd = q->elevator->elevator_data;
983 
984         seq_printf(m, "%u\n", dd->batching);
985         return 0;
986 }
987 
988 static int deadline_starved_show(void *data, struct seq_file *m)
989 {
990         struct request_queue *q = data;
991         struct deadline_data *dd = q->elevator->elevator_data;
992 
993         seq_printf(m, "%u\n", dd->starved);
994         return 0;
995 }
996 
997 static int dd_async_depth_show(void *data, struct seq_file *m)
998 {
999         struct request_queue *q = data;
1000         struct deadline_data *dd = q->elevator->elevator_data;
1001 
1002         seq_printf(m, "%u\n", dd->async_depth);
1003         return 0;
1004 }
1005 
1006 static int dd_queued_show(void *data, struct seq_file *m)
1007 {
1008         struct request_queue *q = data;
1009         struct deadline_data *dd = q->elevator->elevator_data;
1010         u32 rt, be, idle;
1011 
1012         spin_lock(&dd->lock);
1013         rt = dd_queued(dd, DD_RT_PRIO);
1014         be = dd_queued(dd, DD_BE_PRIO);
1015         idle = dd_queued(dd, DD_IDLE_PRIO);
1016         spin_unlock(&dd->lock);
1017 
1018         seq_printf(m, "%u %u %u\n", rt, be, idle);
1019 
1020         return 0;
1021 }
1022 
1023 /* Number of requests owned by the block driver for a given priority. */
1024 static u32 dd_owned_by_driver(struct deadline_data *dd, enum dd_prio prio)
1025 {
1026         const struct io_stats_per_prio *stats = &dd->per_prio[prio].stats;
1027 
1028         lockdep_assert_held(&dd->lock);
1029 
1030         return stats->dispatched + stats->merged -
1031                 atomic_read(&stats->completed);
1032 }
1033 
1034 static int dd_owned_by_driver_show(void *data, struct seq_file *m)
1035 {
1036         struct request_queue *q = data;
1037         struct deadline_data *dd = q->elevator->elevator_data;
1038         u32 rt, be, idle;
1039 
1040         spin_lock(&dd->lock);
1041         rt = dd_owned_by_driver(dd, DD_RT_PRIO);
1042         be = dd_owned_by_driver(dd, DD_BE_PRIO);
1043         idle = dd_owned_by_driver(dd, DD_IDLE_PRIO);
1044         spin_unlock(&dd->lock);
1045 
1046         seq_printf(m, "%u %u %u\n", rt, be, idle);
1047 
1048         return 0;
1049 }
1050 
1051 #define DEADLINE_DISPATCH_ATTR(prio)                                    \
1052 static void *deadline_dispatch##prio##_start(struct seq_file *m,        \
1053                                              loff_t *pos)               \
1054         __acquires(&dd->lock)                                           \
1055 {                                                                       \
1056         struct request_queue *q = m->private;                           \
1057         struct deadline_data *dd = q->elevator->elevator_data;          \
1058         struct dd_per_prio *per_prio = &dd->per_prio[prio];             \
1059                                                                         \
1060         spin_lock(&dd->lock);                                           \
1061         return seq_list_start(&per_prio->dispatch, *pos);               \
1062 }                                                                       \
1063                                                                         \
1064 static void *deadline_dispatch##prio##_next(struct seq_file *m,         \
1065                                             void *v, loff_t *pos)       \
1066 {                                                                       \
1067         struct request_queue *q = m->private;                           \
1068         struct deadline_data *dd = q->elevator->elevator_data;          \
1069         struct dd_per_prio *per_prio = &dd->per_prio[prio];             \
1070                                                                         \
1071         return seq_list_next(v, &per_prio->dispatch, pos);              \
1072 }                                                                       \
1073                                                                         \
1074 static void deadline_dispatch##prio##_stop(struct seq_file *m, void *v) \
1075         __releases(&dd->lock)                                           \
1076 {                                                                       \
1077         struct request_queue *q = m->private;                           \
1078         struct deadline_data *dd = q->elevator->elevator_data;          \
1079                                                                         \
1080         spin_unlock(&dd->lock);                                         \
1081 }                                                                       \
1082                                                                         \
1083 static const struct seq_operations deadline_dispatch##prio##_seq_ops = { \
1084         .start  = deadline_dispatch##prio##_start,                      \
1085         .next   = deadline_dispatch##prio##_next,                       \
1086         .stop   = deadline_dispatch##prio##_stop,                       \
1087         .show   = blk_mq_debugfs_rq_show,                               \
1088 }
1089 
1090 DEADLINE_DISPATCH_ATTR(0);
1091 DEADLINE_DISPATCH_ATTR(1);
1092 DEADLINE_DISPATCH_ATTR(2);
1093 #undef DEADLINE_DISPATCH_ATTR
1094 
1095 #define DEADLINE_QUEUE_DDIR_ATTRS(name)                                 \
1096         {#name "_fifo_list", 0400,                                      \
1097                         .seq_ops = &deadline_##name##_fifo_seq_ops}
1098 #define DEADLINE_NEXT_RQ_ATTR(name)                                     \
1099         {#name "_next_rq", 0400, deadline_##name##_next_rq_show}
1100 static const struct blk_mq_debugfs_attr deadline_queue_debugfs_attrs[] = {
1101         DEADLINE_QUEUE_DDIR_ATTRS(read0),
1102         DEADLINE_QUEUE_DDIR_ATTRS(write0),
1103         DEADLINE_QUEUE_DDIR_ATTRS(read1),
1104         DEADLINE_QUEUE_DDIR_ATTRS(write1),
1105         DEADLINE_QUEUE_DDIR_ATTRS(read2),
1106         DEADLINE_QUEUE_DDIR_ATTRS(write2),
1107         DEADLINE_NEXT_RQ_ATTR(read0),
1108         DEADLINE_NEXT_RQ_ATTR(write0),
1109         DEADLINE_NEXT_RQ_ATTR(read1),
1110         DEADLINE_NEXT_RQ_ATTR(write1),
1111         DEADLINE_NEXT_RQ_ATTR(read2),
1112         DEADLINE_NEXT_RQ_ATTR(write2),
1113         {"batching", 0400, deadline_batching_show},
1114         {"starved", 0400, deadline_starved_show},
1115         {"async_depth", 0400, dd_async_depth_show},
1116         {"dispatch0", 0400, .seq_ops = &deadline_dispatch0_seq_ops},
1117         {"dispatch1", 0400, .seq_ops = &deadline_dispatch1_seq_ops},
1118         {"dispatch2", 0400, .seq_ops = &deadline_dispatch2_seq_ops},
1119         {"owned_by_driver", 0400, dd_owned_by_driver_show},
1120         {"queued", 0400, dd_queued_show},
1121         {},
1122 };
1123 #undef DEADLINE_QUEUE_DDIR_ATTRS
1124 #endif
1125 
1126 static struct elevator_type mq_deadline = {
1127         .ops = {
1128                 .depth_updated          = dd_depth_updated,
1129                 .limit_depth            = dd_limit_depth,
1130                 .insert_requests        = dd_insert_requests,
1131                 .dispatch_request       = dd_dispatch_request,
1132                 .prepare_request        = dd_prepare_request,
1133                 .finish_request         = dd_finish_request,
1134                 .next_request           = elv_rb_latter_request,
1135                 .former_request         = elv_rb_former_request,
1136                 .bio_merge              = dd_bio_merge,
1137                 .request_merge          = dd_request_merge,
1138                 .requests_merged        = dd_merged_requests,
1139                 .request_merged         = dd_request_merged,
1140                 .has_work               = dd_has_work,
1141                 .init_sched             = dd_init_sched,
1142                 .exit_sched             = dd_exit_sched,
1143                 .init_hctx              = dd_init_hctx,
1144         },
1145 
1146 #ifdef CONFIG_BLK_DEBUG_FS
1147         .queue_debugfs_attrs = deadline_queue_debugfs_attrs,
1148 #endif
1149         .elevator_attrs = deadline_attrs,
1150         .elevator_name = "mq-deadline",
1151         .elevator_alias = "deadline",
1152         .elevator_features = ELEVATOR_F_ZBD_SEQ_WRITE,
1153         .elevator_owner = THIS_MODULE,
1154 };
1155 MODULE_ALIAS("mq-deadline-iosched");
1156 
1157 static int __init deadline_init(void)
1158 {
1159         return elv_register(&mq_deadline);
1160 }
1161 
1162 static void __exit deadline_exit(void)
1163 {
1164         elv_unregister(&mq_deadline);
1165 }
1166 
1167 module_init(deadline_init);
1168 module_exit(deadline_exit);
1169 
1170 MODULE_AUTHOR("Jens Axboe, Damien Le Moal and Bart Van Assche");
1171 MODULE_LICENSE("GPL");
1172 MODULE_DESCRIPTION("MQ deadline IO scheduler");
1173 

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