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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/elevator.h>
 13 #include <linux/bio.h>
 14 #include <linux/module.h>
 15 #include <linux/slab.h>
 16 #include <linux/init.h>
 17 #include <linux/compiler.h>
 18 #include <linux/rbtree.h>
 19 #include <linux/sbitmap.h>
 20 
 21 #include "blk.h"
 22 #include "blk-mq.h"
 23 #include "blk-mq-debugfs.h"
 24 #include "blk-mq-tag.h"
 25 #include "blk-mq-sched.h"
 26 
 27 /*
 28  * See Documentation/block/deadline-iosched.rst
 29  */
 30 static const int read_expire = HZ / 2;  /* max time before a read is submitted. */
 31 static const int write_expire = 5 * HZ; /* ditto for writes, these limits are SOFT! */
 32 static const int writes_starved = 2;    /* max times reads can starve a write */
 33 static const int fifo_batch = 16;       /* # of sequential requests treated as one
 34                                      by the above parameters. For throughput. */
 35 
 36 struct deadline_data {
 37         /*
 38          * run time data
 39          */
 40 
 41         /*
 42          * requests (deadline_rq s) are present on both sort_list and fifo_list
 43          */
 44         struct rb_root sort_list[2];
 45         struct list_head fifo_list[2];
 46 
 47         /*
 48          * next in sort order. read, write or both are NULL
 49          */
 50         struct request *next_rq[2];
 51         unsigned int batching;          /* number of sequential requests made */
 52         unsigned int starved;           /* times reads have starved writes */
 53 
 54         /*
 55          * settings that change how the i/o scheduler behaves
 56          */
 57         int fifo_expire[2];
 58         int fifo_batch;
 59         int writes_starved;
 60         int front_merges;
 61 
 62         spinlock_t lock;
 63         spinlock_t zone_lock;
 64         struct list_head dispatch;
 65 };
 66 
 67 static inline struct rb_root *
 68 deadline_rb_root(struct deadline_data *dd, struct request *rq)
 69 {
 70         return &dd->sort_list[rq_data_dir(rq)];
 71 }
 72 
 73 /*
 74  * get the request after `rq' in sector-sorted order
 75  */
 76 static inline struct request *
 77 deadline_latter_request(struct request *rq)
 78 {
 79         struct rb_node *node = rb_next(&rq->rb_node);
 80 
 81         if (node)
 82                 return rb_entry_rq(node);
 83 
 84         return NULL;
 85 }
 86 
 87 static void
 88 deadline_add_rq_rb(struct deadline_data *dd, struct request *rq)
 89 {
 90         struct rb_root *root = deadline_rb_root(dd, rq);
 91 
 92         elv_rb_add(root, rq);
 93 }
 94 
 95 static inline void
 96 deadline_del_rq_rb(struct deadline_data *dd, struct request *rq)
 97 {
 98         const int data_dir = rq_data_dir(rq);
 99 
100         if (dd->next_rq[data_dir] == rq)
101                 dd->next_rq[data_dir] = deadline_latter_request(rq);
102 
103         elv_rb_del(deadline_rb_root(dd, rq), rq);
104 }
105 
106 /*
107  * remove rq from rbtree and fifo.
108  */
109 static void deadline_remove_request(struct request_queue *q, struct request *rq)
110 {
111         struct deadline_data *dd = q->elevator->elevator_data;
112 
113         list_del_init(&rq->queuelist);
114 
115         /*
116          * We might not be on the rbtree, if we are doing an insert merge
117          */
118         if (!RB_EMPTY_NODE(&rq->rb_node))
119                 deadline_del_rq_rb(dd, rq);
120 
121         elv_rqhash_del(q, rq);
122         if (q->last_merge == rq)
123                 q->last_merge = NULL;
124 }
125 
126 static void dd_request_merged(struct request_queue *q, struct request *req,
127                               enum elv_merge type)
128 {
129         struct deadline_data *dd = q->elevator->elevator_data;
130 
131         /*
132          * if the merge was a front merge, we need to reposition request
133          */
134         if (type == ELEVATOR_FRONT_MERGE) {
135                 elv_rb_del(deadline_rb_root(dd, req), req);
136                 deadline_add_rq_rb(dd, req);
137         }
138 }
139 
140 static void dd_merged_requests(struct request_queue *q, struct request *req,
141                                struct request *next)
142 {
143         /*
144          * if next expires before rq, assign its expire time to rq
145          * and move into next position (next will be deleted) in fifo
146          */
147         if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) {
148                 if (time_before((unsigned long)next->fifo_time,
149                                 (unsigned long)req->fifo_time)) {
150                         list_move(&req->queuelist, &next->queuelist);
151                         req->fifo_time = next->fifo_time;
152                 }
153         }
154 
155         /*
156          * kill knowledge of next, this one is a goner
157          */
158         deadline_remove_request(q, next);
159 }
160 
161 /*
162  * move an entry to dispatch queue
163  */
164 static void
165 deadline_move_request(struct deadline_data *dd, struct request *rq)
166 {
167         const int data_dir = rq_data_dir(rq);
168 
169         dd->next_rq[READ] = NULL;
170         dd->next_rq[WRITE] = NULL;
171         dd->next_rq[data_dir] = deadline_latter_request(rq);
172 
173         /*
174          * take it off the sort and fifo list
175          */
176         deadline_remove_request(rq->q, rq);
177 }
178 
179 /*
180  * deadline_check_fifo returns 0 if there are no expired requests on the fifo,
181  * 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
182  */
183 static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
184 {
185         struct request *rq = rq_entry_fifo(dd->fifo_list[ddir].next);
186 
187         /*
188          * rq is expired!
189          */
190         if (time_after_eq(jiffies, (unsigned long)rq->fifo_time))
191                 return 1;
192 
193         return 0;
194 }
195 
196 /*
197  * For the specified data direction, return the next request to
198  * dispatch using arrival ordered lists.
199  */
200 static struct request *
201 deadline_fifo_request(struct deadline_data *dd, int data_dir)
202 {
203         struct request *rq;
204         unsigned long flags;
205 
206         if (WARN_ON_ONCE(data_dir != READ && data_dir != WRITE))
207                 return NULL;
208 
209         if (list_empty(&dd->fifo_list[data_dir]))
210                 return NULL;
211 
212         rq = rq_entry_fifo(dd->fifo_list[data_dir].next);
213         if (data_dir == READ || !blk_queue_is_zoned(rq->q))
214                 return rq;
215 
216         /*
217          * Look for a write request that can be dispatched, that is one with
218          * an unlocked target zone.
219          */
220         spin_lock_irqsave(&dd->zone_lock, flags);
221         list_for_each_entry(rq, &dd->fifo_list[WRITE], queuelist) {
222                 if (blk_req_can_dispatch_to_zone(rq))
223                         goto out;
224         }
225         rq = NULL;
226 out:
227         spin_unlock_irqrestore(&dd->zone_lock, flags);
228 
229         return rq;
230 }
231 
232 /*
233  * For the specified data direction, return the next request to
234  * dispatch using sector position sorted lists.
235  */
236 static struct request *
237 deadline_next_request(struct deadline_data *dd, int data_dir)
238 {
239         struct request *rq;
240         unsigned long flags;
241 
242         if (WARN_ON_ONCE(data_dir != READ && data_dir != WRITE))
243                 return NULL;
244 
245         rq = dd->next_rq[data_dir];
246         if (!rq)
247                 return NULL;
248 
249         if (data_dir == READ || !blk_queue_is_zoned(rq->q))
250                 return rq;
251 
252         /*
253          * Look for a write request that can be dispatched, that is one with
254          * an unlocked target zone.
255          */
256         spin_lock_irqsave(&dd->zone_lock, flags);
257         while (rq) {
258                 if (blk_req_can_dispatch_to_zone(rq))
259                         break;
260                 rq = deadline_latter_request(rq);
261         }
262         spin_unlock_irqrestore(&dd->zone_lock, flags);
263 
264         return rq;
265 }
266 
267 /*
268  * deadline_dispatch_requests selects the best request according to
269  * read/write expire, fifo_batch, etc
270  */
271 static struct request *__dd_dispatch_request(struct deadline_data *dd)
272 {
273         struct request *rq, *next_rq;
274         bool reads, writes;
275         int data_dir;
276 
277         if (!list_empty(&dd->dispatch)) {
278                 rq = list_first_entry(&dd->dispatch, struct request, queuelist);
279                 list_del_init(&rq->queuelist);
280                 goto done;
281         }
282 
283         reads = !list_empty(&dd->fifo_list[READ]);
284         writes = !list_empty(&dd->fifo_list[WRITE]);
285 
286         /*
287          * batches are currently reads XOR writes
288          */
289         rq = deadline_next_request(dd, WRITE);
290         if (!rq)
291                 rq = deadline_next_request(dd, READ);
292 
293         if (rq && dd->batching < dd->fifo_batch)
294                 /* we have a next request are still entitled to batch */
295                 goto dispatch_request;
296 
297         /*
298          * at this point we are not running a batch. select the appropriate
299          * data direction (read / write)
300          */
301 
302         if (reads) {
303                 BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[READ]));
304 
305                 if (deadline_fifo_request(dd, WRITE) &&
306                     (dd->starved++ >= dd->writes_starved))
307                         goto dispatch_writes;
308 
309                 data_dir = READ;
310 
311                 goto dispatch_find_request;
312         }
313 
314         /*
315          * there are either no reads or writes have been starved
316          */
317 
318         if (writes) {
319 dispatch_writes:
320                 BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[WRITE]));
321 
322                 dd->starved = 0;
323 
324                 data_dir = WRITE;
325 
326                 goto dispatch_find_request;
327         }
328 
329         return NULL;
330 
331 dispatch_find_request:
332         /*
333          * we are not running a batch, find best request for selected data_dir
334          */
335         next_rq = deadline_next_request(dd, data_dir);
336         if (deadline_check_fifo(dd, data_dir) || !next_rq) {
337                 /*
338                  * A deadline has expired, the last request was in the other
339                  * direction, or we have run out of higher-sectored requests.
340                  * Start again from the request with the earliest expiry time.
341                  */
342                 rq = deadline_fifo_request(dd, data_dir);
343         } else {
344                 /*
345                  * The last req was the same dir and we have a next request in
346                  * sort order. No expired requests so continue on from here.
347                  */
348                 rq = next_rq;
349         }
350 
351         /*
352          * For a zoned block device, if we only have writes queued and none of
353          * them can be dispatched, rq will be NULL.
354          */
355         if (!rq)
356                 return NULL;
357 
358         dd->batching = 0;
359 
360 dispatch_request:
361         /*
362          * rq is the selected appropriate request.
363          */
364         dd->batching++;
365         deadline_move_request(dd, rq);
366 done:
367         /*
368          * If the request needs its target zone locked, do it.
369          */
370         blk_req_zone_write_lock(rq);
371         rq->rq_flags |= RQF_STARTED;
372         return rq;
373 }
374 
375 /*
376  * One confusing aspect here is that we get called for a specific
377  * hardware queue, but we may return a request that is for a
378  * different hardware queue. This is because mq-deadline has shared
379  * state for all hardware queues, in terms of sorting, FIFOs, etc.
380  */
381 static struct request *dd_dispatch_request(struct blk_mq_hw_ctx *hctx)
382 {
383         struct deadline_data *dd = hctx->queue->elevator->elevator_data;
384         struct request *rq;
385 
386         spin_lock(&dd->lock);
387         rq = __dd_dispatch_request(dd);
388         spin_unlock(&dd->lock);
389 
390         return rq;
391 }
392 
393 static void dd_exit_queue(struct elevator_queue *e)
394 {
395         struct deadline_data *dd = e->elevator_data;
396 
397         BUG_ON(!list_empty(&dd->fifo_list[READ]));
398         BUG_ON(!list_empty(&dd->fifo_list[WRITE]));
399 
400         kfree(dd);
401 }
402 
403 /*
404  * initialize elevator private data (deadline_data).
405  */
406 static int dd_init_queue(struct request_queue *q, struct elevator_type *e)
407 {
408         struct deadline_data *dd;
409         struct elevator_queue *eq;
410 
411         eq = elevator_alloc(q, e);
412         if (!eq)
413                 return -ENOMEM;
414 
415         dd = kzalloc_node(sizeof(*dd), GFP_KERNEL, q->node);
416         if (!dd) {
417                 kobject_put(&eq->kobj);
418                 return -ENOMEM;
419         }
420         eq->elevator_data = dd;
421 
422         INIT_LIST_HEAD(&dd->fifo_list[READ]);
423         INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
424         dd->sort_list[READ] = RB_ROOT;
425         dd->sort_list[WRITE] = RB_ROOT;
426         dd->fifo_expire[READ] = read_expire;
427         dd->fifo_expire[WRITE] = write_expire;
428         dd->writes_starved = writes_starved;
429         dd->front_merges = 1;
430         dd->fifo_batch = fifo_batch;
431         spin_lock_init(&dd->lock);
432         spin_lock_init(&dd->zone_lock);
433         INIT_LIST_HEAD(&dd->dispatch);
434 
435         q->elevator = eq;
436         return 0;
437 }
438 
439 static int dd_request_merge(struct request_queue *q, struct request **rq,
440                             struct bio *bio)
441 {
442         struct deadline_data *dd = q->elevator->elevator_data;
443         sector_t sector = bio_end_sector(bio);
444         struct request *__rq;
445 
446         if (!dd->front_merges)
447                 return ELEVATOR_NO_MERGE;
448 
449         __rq = elv_rb_find(&dd->sort_list[bio_data_dir(bio)], sector);
450         if (__rq) {
451                 BUG_ON(sector != blk_rq_pos(__rq));
452 
453                 if (elv_bio_merge_ok(__rq, bio)) {
454                         *rq = __rq;
455                         return ELEVATOR_FRONT_MERGE;
456                 }
457         }
458 
459         return ELEVATOR_NO_MERGE;
460 }
461 
462 static bool dd_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio,
463                 unsigned int nr_segs)
464 {
465         struct request_queue *q = hctx->queue;
466         struct deadline_data *dd = q->elevator->elevator_data;
467         struct request *free = NULL;
468         bool ret;
469 
470         spin_lock(&dd->lock);
471         ret = blk_mq_sched_try_merge(q, bio, nr_segs, &free);
472         spin_unlock(&dd->lock);
473 
474         if (free)
475                 blk_mq_free_request(free);
476 
477         return ret;
478 }
479 
480 /*
481  * add rq to rbtree and fifo
482  */
483 static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
484                               bool at_head)
485 {
486         struct request_queue *q = hctx->queue;
487         struct deadline_data *dd = q->elevator->elevator_data;
488         const int data_dir = rq_data_dir(rq);
489 
490         /*
491          * This may be a requeue of a write request that has locked its
492          * target zone. If it is the case, this releases the zone lock.
493          */
494         blk_req_zone_write_unlock(rq);
495 
496         if (blk_mq_sched_try_insert_merge(q, rq))
497                 return;
498 
499         blk_mq_sched_request_inserted(rq);
500 
501         if (at_head || blk_rq_is_passthrough(rq)) {
502                 if (at_head)
503                         list_add(&rq->queuelist, &dd->dispatch);
504                 else
505                         list_add_tail(&rq->queuelist, &dd->dispatch);
506         } else {
507                 deadline_add_rq_rb(dd, rq);
508 
509                 if (rq_mergeable(rq)) {
510                         elv_rqhash_add(q, rq);
511                         if (!q->last_merge)
512                                 q->last_merge = rq;
513                 }
514 
515                 /*
516                  * set expire time and add to fifo list
517                  */
518                 rq->fifo_time = jiffies + dd->fifo_expire[data_dir];
519                 list_add_tail(&rq->queuelist, &dd->fifo_list[data_dir]);
520         }
521 }
522 
523 static void dd_insert_requests(struct blk_mq_hw_ctx *hctx,
524                                struct list_head *list, bool at_head)
525 {
526         struct request_queue *q = hctx->queue;
527         struct deadline_data *dd = q->elevator->elevator_data;
528 
529         spin_lock(&dd->lock);
530         while (!list_empty(list)) {
531                 struct request *rq;
532 
533                 rq = list_first_entry(list, struct request, queuelist);
534                 list_del_init(&rq->queuelist);
535                 dd_insert_request(hctx, rq, at_head);
536         }
537         spin_unlock(&dd->lock);
538 }
539 
540 /*
541  * Nothing to do here. This is defined only to ensure that .finish_request
542  * method is called upon request completion.
543  */
544 static void dd_prepare_request(struct request *rq, struct bio *bio)
545 {
546 }
547 
548 /*
549  * For zoned block devices, write unlock the target zone of
550  * completed write requests. Do this while holding the zone lock
551  * spinlock so that the zone is never unlocked while deadline_fifo_request()
552  * or deadline_next_request() are executing. This function is called for
553  * all requests, whether or not these requests complete successfully.
554  *
555  * For a zoned block device, __dd_dispatch_request() may have stopped
556  * dispatching requests if all the queued requests are write requests directed
557  * at zones that are already locked due to on-going write requests. To ensure
558  * write request dispatch progress in this case, mark the queue as needing a
559  * restart to ensure that the queue is run again after completion of the
560  * request and zones being unlocked.
561  */
562 static void dd_finish_request(struct request *rq)
563 {
564         struct request_queue *q = rq->q;
565 
566         if (blk_queue_is_zoned(q)) {
567                 struct deadline_data *dd = q->elevator->elevator_data;
568                 unsigned long flags;
569 
570                 spin_lock_irqsave(&dd->zone_lock, flags);
571                 blk_req_zone_write_unlock(rq);
572                 if (!list_empty(&dd->fifo_list[WRITE]))
573                         blk_mq_sched_mark_restart_hctx(rq->mq_hctx);
574                 spin_unlock_irqrestore(&dd->zone_lock, flags);
575         }
576 }
577 
578 static bool dd_has_work(struct blk_mq_hw_ctx *hctx)
579 {
580         struct deadline_data *dd = hctx->queue->elevator->elevator_data;
581 
582         return !list_empty_careful(&dd->dispatch) ||
583                 !list_empty_careful(&dd->fifo_list[0]) ||
584                 !list_empty_careful(&dd->fifo_list[1]);
585 }
586 
587 /*
588  * sysfs parts below
589  */
590 static ssize_t
591 deadline_var_show(int var, char *page)
592 {
593         return sprintf(page, "%d\n", var);
594 }
595 
596 static void
597 deadline_var_store(int *var, const char *page)
598 {
599         char *p = (char *) page;
600 
601         *var = simple_strtol(p, &p, 10);
602 }
603 
604 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)                            \
605 static ssize_t __FUNC(struct elevator_queue *e, char *page)             \
606 {                                                                       \
607         struct deadline_data *dd = e->elevator_data;                    \
608         int __data = __VAR;                                             \
609         if (__CONV)                                                     \
610                 __data = jiffies_to_msecs(__data);                      \
611         return deadline_var_show(__data, (page));                       \
612 }
613 SHOW_FUNCTION(deadline_read_expire_show, dd->fifo_expire[READ], 1);
614 SHOW_FUNCTION(deadline_write_expire_show, dd->fifo_expire[WRITE], 1);
615 SHOW_FUNCTION(deadline_writes_starved_show, dd->writes_starved, 0);
616 SHOW_FUNCTION(deadline_front_merges_show, dd->front_merges, 0);
617 SHOW_FUNCTION(deadline_fifo_batch_show, dd->fifo_batch, 0);
618 #undef SHOW_FUNCTION
619 
620 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
621 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
622 {                                                                       \
623         struct deadline_data *dd = e->elevator_data;                    \
624         int __data;                                                     \
625         deadline_var_store(&__data, (page));                            \
626         if (__data < (MIN))                                             \
627                 __data = (MIN);                                         \
628         else if (__data > (MAX))                                        \
629                 __data = (MAX);                                         \
630         if (__CONV)                                                     \
631                 *(__PTR) = msecs_to_jiffies(__data);                    \
632         else                                                            \
633                 *(__PTR) = __data;                                      \
634         return count;                                                   \
635 }
636 STORE_FUNCTION(deadline_read_expire_store, &dd->fifo_expire[READ], 0, INT_MAX, 1);
637 STORE_FUNCTION(deadline_write_expire_store, &dd->fifo_expire[WRITE], 0, INT_MAX, 1);
638 STORE_FUNCTION(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX, 0);
639 STORE_FUNCTION(deadline_front_merges_store, &dd->front_merges, 0, 1, 0);
640 STORE_FUNCTION(deadline_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX, 0);
641 #undef STORE_FUNCTION
642 
643 #define DD_ATTR(name) \
644         __ATTR(name, 0644, deadline_##name##_show, deadline_##name##_store)
645 
646 static struct elv_fs_entry deadline_attrs[] = {
647         DD_ATTR(read_expire),
648         DD_ATTR(write_expire),
649         DD_ATTR(writes_starved),
650         DD_ATTR(front_merges),
651         DD_ATTR(fifo_batch),
652         __ATTR_NULL
653 };
654 
655 #ifdef CONFIG_BLK_DEBUG_FS
656 #define DEADLINE_DEBUGFS_DDIR_ATTRS(ddir, name)                         \
657 static void *deadline_##name##_fifo_start(struct seq_file *m,           \
658                                           loff_t *pos)                  \
659         __acquires(&dd->lock)                                           \
660 {                                                                       \
661         struct request_queue *q = m->private;                           \
662         struct deadline_data *dd = q->elevator->elevator_data;          \
663                                                                         \
664         spin_lock(&dd->lock);                                           \
665         return seq_list_start(&dd->fifo_list[ddir], *pos);              \
666 }                                                                       \
667                                                                         \
668 static void *deadline_##name##_fifo_next(struct seq_file *m, void *v,   \
669                                          loff_t *pos)                   \
670 {                                                                       \
671         struct request_queue *q = m->private;                           \
672         struct deadline_data *dd = q->elevator->elevator_data;          \
673                                                                         \
674         return seq_list_next(v, &dd->fifo_list[ddir], pos);             \
675 }                                                                       \
676                                                                         \
677 static void deadline_##name##_fifo_stop(struct seq_file *m, void *v)    \
678         __releases(&dd->lock)                                           \
679 {                                                                       \
680         struct request_queue *q = m->private;                           \
681         struct deadline_data *dd = q->elevator->elevator_data;          \
682                                                                         \
683         spin_unlock(&dd->lock);                                         \
684 }                                                                       \
685                                                                         \
686 static const struct seq_operations deadline_##name##_fifo_seq_ops = {   \
687         .start  = deadline_##name##_fifo_start,                         \
688         .next   = deadline_##name##_fifo_next,                          \
689         .stop   = deadline_##name##_fifo_stop,                          \
690         .show   = blk_mq_debugfs_rq_show,                               \
691 };                                                                      \
692                                                                         \
693 static int deadline_##name##_next_rq_show(void *data,                   \
694                                           struct seq_file *m)           \
695 {                                                                       \
696         struct request_queue *q = data;                                 \
697         struct deadline_data *dd = q->elevator->elevator_data;          \
698         struct request *rq = dd->next_rq[ddir];                         \
699                                                                         \
700         if (rq)                                                         \
701                 __blk_mq_debugfs_rq_show(m, rq);                        \
702         return 0;                                                       \
703 }
704 DEADLINE_DEBUGFS_DDIR_ATTRS(READ, read)
705 DEADLINE_DEBUGFS_DDIR_ATTRS(WRITE, write)
706 #undef DEADLINE_DEBUGFS_DDIR_ATTRS
707 
708 static int deadline_batching_show(void *data, struct seq_file *m)
709 {
710         struct request_queue *q = data;
711         struct deadline_data *dd = q->elevator->elevator_data;
712 
713         seq_printf(m, "%u\n", dd->batching);
714         return 0;
715 }
716 
717 static int deadline_starved_show(void *data, struct seq_file *m)
718 {
719         struct request_queue *q = data;
720         struct deadline_data *dd = q->elevator->elevator_data;
721 
722         seq_printf(m, "%u\n", dd->starved);
723         return 0;
724 }
725 
726 static void *deadline_dispatch_start(struct seq_file *m, loff_t *pos)
727         __acquires(&dd->lock)
728 {
729         struct request_queue *q = m->private;
730         struct deadline_data *dd = q->elevator->elevator_data;
731 
732         spin_lock(&dd->lock);
733         return seq_list_start(&dd->dispatch, *pos);
734 }
735 
736 static void *deadline_dispatch_next(struct seq_file *m, void *v, loff_t *pos)
737 {
738         struct request_queue *q = m->private;
739         struct deadline_data *dd = q->elevator->elevator_data;
740 
741         return seq_list_next(v, &dd->dispatch, pos);
742 }
743 
744 static void deadline_dispatch_stop(struct seq_file *m, void *v)
745         __releases(&dd->lock)
746 {
747         struct request_queue *q = m->private;
748         struct deadline_data *dd = q->elevator->elevator_data;
749 
750         spin_unlock(&dd->lock);
751 }
752 
753 static const struct seq_operations deadline_dispatch_seq_ops = {
754         .start  = deadline_dispatch_start,
755         .next   = deadline_dispatch_next,
756         .stop   = deadline_dispatch_stop,
757         .show   = blk_mq_debugfs_rq_show,
758 };
759 
760 #define DEADLINE_QUEUE_DDIR_ATTRS(name)                                         \
761         {#name "_fifo_list", 0400, .seq_ops = &deadline_##name##_fifo_seq_ops}, \
762         {#name "_next_rq", 0400, deadline_##name##_next_rq_show}
763 static const struct blk_mq_debugfs_attr deadline_queue_debugfs_attrs[] = {
764         DEADLINE_QUEUE_DDIR_ATTRS(read),
765         DEADLINE_QUEUE_DDIR_ATTRS(write),
766         {"batching", 0400, deadline_batching_show},
767         {"starved", 0400, deadline_starved_show},
768         {"dispatch", 0400, .seq_ops = &deadline_dispatch_seq_ops},
769         {},
770 };
771 #undef DEADLINE_QUEUE_DDIR_ATTRS
772 #endif
773 
774 static struct elevator_type mq_deadline = {
775         .ops = {
776                 .insert_requests        = dd_insert_requests,
777                 .dispatch_request       = dd_dispatch_request,
778                 .prepare_request        = dd_prepare_request,
779                 .finish_request         = dd_finish_request,
780                 .next_request           = elv_rb_latter_request,
781                 .former_request         = elv_rb_former_request,
782                 .bio_merge              = dd_bio_merge,
783                 .request_merge          = dd_request_merge,
784                 .requests_merged        = dd_merged_requests,
785                 .request_merged         = dd_request_merged,
786                 .has_work               = dd_has_work,
787                 .init_sched             = dd_init_queue,
788                 .exit_sched             = dd_exit_queue,
789         },
790 
791 #ifdef CONFIG_BLK_DEBUG_FS
792         .queue_debugfs_attrs = deadline_queue_debugfs_attrs,
793 #endif
794         .elevator_attrs = deadline_attrs,
795         .elevator_name = "mq-deadline",
796         .elevator_alias = "deadline",
797         .elevator_owner = THIS_MODULE,
798 };
799 MODULE_ALIAS("mq-deadline-iosched");
800 
801 static int __init deadline_init(void)
802 {
803         return elv_register(&mq_deadline);
804 }
805 
806 static void __exit deadline_exit(void)
807 {
808         elv_unregister(&mq_deadline);
809 }
810 
811 module_init(deadline_init);
812 module_exit(deadline_exit);
813 
814 MODULE_AUTHOR("Jens Axboe");
815 MODULE_LICENSE("GPL");
816 MODULE_DESCRIPTION("MQ deadline IO scheduler");
817 

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