xref: /openbmc/linux/block/mq-deadline.c (revision f220d3eb)
1 /*
2  *  MQ Deadline i/o scheduler - adaptation of the legacy deadline scheduler,
3  *  for the blk-mq scheduling framework
4  *
5  *  Copyright (C) 2016 Jens Axboe <axboe@kernel.dk>
6  */
7 #include <linux/kernel.h>
8 #include <linux/fs.h>
9 #include <linux/blkdev.h>
10 #include <linux/blk-mq.h>
11 #include <linux/elevator.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 "blk.h"
21 #include "blk-mq.h"
22 #include "blk-mq-debugfs.h"
23 #include "blk-mq-tag.h"
24 #include "blk-mq-sched.h"
25 
26 /*
27  * See Documentation/block/deadline-iosched.txt
28  */
29 static const int read_expire = HZ / 2;  /* max time before a read is submitted. */
30 static const int write_expire = 5 * HZ; /* ditto for writes, these limits are SOFT! */
31 static const int writes_starved = 2;    /* max times reads can starve a write */
32 static const int fifo_batch = 16;       /* # of sequential requests treated as one
33 				     by the above parameters. For throughput. */
34 
35 struct deadline_data {
36 	/*
37 	 * run time data
38 	 */
39 
40 	/*
41 	 * requests (deadline_rq s) are present on both sort_list and fifo_list
42 	 */
43 	struct rb_root sort_list[2];
44 	struct list_head fifo_list[2];
45 
46 	/*
47 	 * next in sort order. read, write or both are NULL
48 	 */
49 	struct request *next_rq[2];
50 	unsigned int batching;		/* number of sequential requests made */
51 	unsigned int starved;		/* times reads have starved writes */
52 
53 	/*
54 	 * settings that change how the i/o scheduler behaves
55 	 */
56 	int fifo_expire[2];
57 	int fifo_batch;
58 	int writes_starved;
59 	int front_merges;
60 
61 	spinlock_t lock;
62 	spinlock_t zone_lock;
63 	struct list_head dispatch;
64 };
65 
66 static inline struct rb_root *
67 deadline_rb_root(struct deadline_data *dd, struct request *rq)
68 {
69 	return &dd->sort_list[rq_data_dir(rq)];
70 }
71 
72 /*
73  * get the request after `rq' in sector-sorted order
74  */
75 static inline struct request *
76 deadline_latter_request(struct request *rq)
77 {
78 	struct rb_node *node = rb_next(&rq->rb_node);
79 
80 	if (node)
81 		return rb_entry_rq(node);
82 
83 	return NULL;
84 }
85 
86 static void
87 deadline_add_rq_rb(struct deadline_data *dd, struct request *rq)
88 {
89 	struct rb_root *root = deadline_rb_root(dd, rq);
90 
91 	elv_rb_add(root, rq);
92 }
93 
94 static inline void
95 deadline_del_rq_rb(struct deadline_data *dd, struct request *rq)
96 {
97 	const int data_dir = rq_data_dir(rq);
98 
99 	if (dd->next_rq[data_dir] == rq)
100 		dd->next_rq[data_dir] = deadline_latter_request(rq);
101 
102 	elv_rb_del(deadline_rb_root(dd, rq), rq);
103 }
104 
105 /*
106  * remove rq from rbtree and fifo.
107  */
108 static void deadline_remove_request(struct request_queue *q, struct request *rq)
109 {
110 	struct deadline_data *dd = q->elevator->elevator_data;
111 
112 	list_del_init(&rq->queuelist);
113 
114 	/*
115 	 * We might not be on the rbtree, if we are doing an insert merge
116 	 */
117 	if (!RB_EMPTY_NODE(&rq->rb_node))
118 		deadline_del_rq_rb(dd, rq);
119 
120 	elv_rqhash_del(q, rq);
121 	if (q->last_merge == rq)
122 		q->last_merge = NULL;
123 }
124 
125 static void dd_request_merged(struct request_queue *q, struct request *req,
126 			      enum elv_merge type)
127 {
128 	struct deadline_data *dd = q->elevator->elevator_data;
129 
130 	/*
131 	 * if the merge was a front merge, we need to reposition request
132 	 */
133 	if (type == ELEVATOR_FRONT_MERGE) {
134 		elv_rb_del(deadline_rb_root(dd, req), req);
135 		deadline_add_rq_rb(dd, req);
136 	}
137 }
138 
139 static void dd_merged_requests(struct request_queue *q, struct request *req,
140 			       struct request *next)
141 {
142 	/*
143 	 * if next expires before rq, assign its expire time to rq
144 	 * and move into next position (next will be deleted) in fifo
145 	 */
146 	if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) {
147 		if (time_before((unsigned long)next->fifo_time,
148 				(unsigned long)req->fifo_time)) {
149 			list_move(&req->queuelist, &next->queuelist);
150 			req->fifo_time = next->fifo_time;
151 		}
152 	}
153 
154 	/*
155 	 * kill knowledge of next, this one is a goner
156 	 */
157 	deadline_remove_request(q, next);
158 }
159 
160 /*
161  * move an entry to dispatch queue
162  */
163 static void
164 deadline_move_request(struct deadline_data *dd, struct request *rq)
165 {
166 	const int data_dir = rq_data_dir(rq);
167 
168 	dd->next_rq[READ] = NULL;
169 	dd->next_rq[WRITE] = NULL;
170 	dd->next_rq[data_dir] = deadline_latter_request(rq);
171 
172 	/*
173 	 * take it off the sort and fifo list
174 	 */
175 	deadline_remove_request(rq->q, rq);
176 }
177 
178 /*
179  * deadline_check_fifo returns 0 if there are no expired requests on the fifo,
180  * 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
181  */
182 static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
183 {
184 	struct request *rq = rq_entry_fifo(dd->fifo_list[ddir].next);
185 
186 	/*
187 	 * rq is expired!
188 	 */
189 	if (time_after_eq(jiffies, (unsigned long)rq->fifo_time))
190 		return 1;
191 
192 	return 0;
193 }
194 
195 /*
196  * For the specified data direction, return the next request to
197  * dispatch using arrival ordered lists.
198  */
199 static struct request *
200 deadline_fifo_request(struct deadline_data *dd, int data_dir)
201 {
202 	struct request *rq;
203 	unsigned long flags;
204 
205 	if (WARN_ON_ONCE(data_dir != READ && data_dir != WRITE))
206 		return NULL;
207 
208 	if (list_empty(&dd->fifo_list[data_dir]))
209 		return NULL;
210 
211 	rq = rq_entry_fifo(dd->fifo_list[data_dir].next);
212 	if (data_dir == READ || !blk_queue_is_zoned(rq->q))
213 		return rq;
214 
215 	/*
216 	 * Look for a write request that can be dispatched, that is one with
217 	 * an unlocked target zone.
218 	 */
219 	spin_lock_irqsave(&dd->zone_lock, flags);
220 	list_for_each_entry(rq, &dd->fifo_list[WRITE], queuelist) {
221 		if (blk_req_can_dispatch_to_zone(rq))
222 			goto out;
223 	}
224 	rq = NULL;
225 out:
226 	spin_unlock_irqrestore(&dd->zone_lock, flags);
227 
228 	return rq;
229 }
230 
231 /*
232  * For the specified data direction, return the next request to
233  * dispatch using sector position sorted lists.
234  */
235 static struct request *
236 deadline_next_request(struct deadline_data *dd, int data_dir)
237 {
238 	struct request *rq;
239 	unsigned long flags;
240 
241 	if (WARN_ON_ONCE(data_dir != READ && data_dir != WRITE))
242 		return NULL;
243 
244 	rq = dd->next_rq[data_dir];
245 	if (!rq)
246 		return NULL;
247 
248 	if (data_dir == READ || !blk_queue_is_zoned(rq->q))
249 		return rq;
250 
251 	/*
252 	 * Look for a write request that can be dispatched, that is one with
253 	 * an unlocked target zone.
254 	 */
255 	spin_lock_irqsave(&dd->zone_lock, flags);
256 	while (rq) {
257 		if (blk_req_can_dispatch_to_zone(rq))
258 			break;
259 		rq = deadline_latter_request(rq);
260 	}
261 	spin_unlock_irqrestore(&dd->zone_lock, flags);
262 
263 	return rq;
264 }
265 
266 /*
267  * deadline_dispatch_requests selects the best request according to
268  * read/write expire, fifo_batch, etc
269  */
270 static struct request *__dd_dispatch_request(struct deadline_data *dd)
271 {
272 	struct request *rq, *next_rq;
273 	bool reads, writes;
274 	int data_dir;
275 
276 	if (!list_empty(&dd->dispatch)) {
277 		rq = list_first_entry(&dd->dispatch, struct request, queuelist);
278 		list_del_init(&rq->queuelist);
279 		goto done;
280 	}
281 
282 	reads = !list_empty(&dd->fifo_list[READ]);
283 	writes = !list_empty(&dd->fifo_list[WRITE]);
284 
285 	/*
286 	 * batches are currently reads XOR writes
287 	 */
288 	rq = deadline_next_request(dd, WRITE);
289 	if (!rq)
290 		rq = deadline_next_request(dd, READ);
291 
292 	if (rq && dd->batching < dd->fifo_batch)
293 		/* we have a next request are still entitled to batch */
294 		goto dispatch_request;
295 
296 	/*
297 	 * at this point we are not running a batch. select the appropriate
298 	 * data direction (read / write)
299 	 */
300 
301 	if (reads) {
302 		BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[READ]));
303 
304 		if (deadline_fifo_request(dd, WRITE) &&
305 		    (dd->starved++ >= dd->writes_starved))
306 			goto dispatch_writes;
307 
308 		data_dir = READ;
309 
310 		goto dispatch_find_request;
311 	}
312 
313 	/*
314 	 * there are either no reads or writes have been starved
315 	 */
316 
317 	if (writes) {
318 dispatch_writes:
319 		BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[WRITE]));
320 
321 		dd->starved = 0;
322 
323 		data_dir = WRITE;
324 
325 		goto dispatch_find_request;
326 	}
327 
328 	return NULL;
329 
330 dispatch_find_request:
331 	/*
332 	 * we are not running a batch, find best request for selected data_dir
333 	 */
334 	next_rq = deadline_next_request(dd, data_dir);
335 	if (deadline_check_fifo(dd, data_dir) || !next_rq) {
336 		/*
337 		 * A deadline has expired, the last request was in the other
338 		 * direction, or we have run out of higher-sectored requests.
339 		 * Start again from the request with the earliest expiry time.
340 		 */
341 		rq = deadline_fifo_request(dd, data_dir);
342 	} else {
343 		/*
344 		 * The last req was the same dir and we have a next request in
345 		 * sort order. No expired requests so continue on from here.
346 		 */
347 		rq = next_rq;
348 	}
349 
350 	/*
351 	 * For a zoned block device, if we only have writes queued and none of
352 	 * them can be dispatched, rq will be NULL.
353 	 */
354 	if (!rq)
355 		return NULL;
356 
357 	dd->batching = 0;
358 
359 dispatch_request:
360 	/*
361 	 * rq is the selected appropriate request.
362 	 */
363 	dd->batching++;
364 	deadline_move_request(dd, rq);
365 done:
366 	/*
367 	 * If the request needs its target zone locked, do it.
368 	 */
369 	blk_req_zone_write_lock(rq);
370 	rq->rq_flags |= RQF_STARTED;
371 	return rq;
372 }
373 
374 /*
375  * One confusing aspect here is that we get called for a specific
376  * hardware queue, but we return a request that may not be for a
377  * different hardware queue. This is because mq-deadline has shared
378  * state for all hardware queues, in terms of sorting, FIFOs, etc.
379  */
380 static struct request *dd_dispatch_request(struct blk_mq_hw_ctx *hctx)
381 {
382 	struct deadline_data *dd = hctx->queue->elevator->elevator_data;
383 	struct request *rq;
384 
385 	spin_lock(&dd->lock);
386 	rq = __dd_dispatch_request(dd);
387 	spin_unlock(&dd->lock);
388 
389 	return rq;
390 }
391 
392 static void dd_exit_queue(struct elevator_queue *e)
393 {
394 	struct deadline_data *dd = e->elevator_data;
395 
396 	BUG_ON(!list_empty(&dd->fifo_list[READ]));
397 	BUG_ON(!list_empty(&dd->fifo_list[WRITE]));
398 
399 	kfree(dd);
400 }
401 
402 /*
403  * initialize elevator private data (deadline_data).
404  */
405 static int dd_init_queue(struct request_queue *q, struct elevator_type *e)
406 {
407 	struct deadline_data *dd;
408 	struct elevator_queue *eq;
409 
410 	eq = elevator_alloc(q, e);
411 	if (!eq)
412 		return -ENOMEM;
413 
414 	dd = kzalloc_node(sizeof(*dd), GFP_KERNEL, q->node);
415 	if (!dd) {
416 		kobject_put(&eq->kobj);
417 		return -ENOMEM;
418 	}
419 	eq->elevator_data = dd;
420 
421 	INIT_LIST_HEAD(&dd->fifo_list[READ]);
422 	INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
423 	dd->sort_list[READ] = RB_ROOT;
424 	dd->sort_list[WRITE] = RB_ROOT;
425 	dd->fifo_expire[READ] = read_expire;
426 	dd->fifo_expire[WRITE] = write_expire;
427 	dd->writes_starved = writes_starved;
428 	dd->front_merges = 1;
429 	dd->fifo_batch = fifo_batch;
430 	spin_lock_init(&dd->lock);
431 	spin_lock_init(&dd->zone_lock);
432 	INIT_LIST_HEAD(&dd->dispatch);
433 
434 	q->elevator = eq;
435 	return 0;
436 }
437 
438 static int dd_request_merge(struct request_queue *q, struct request **rq,
439 			    struct bio *bio)
440 {
441 	struct deadline_data *dd = q->elevator->elevator_data;
442 	sector_t sector = bio_end_sector(bio);
443 	struct request *__rq;
444 
445 	if (!dd->front_merges)
446 		return ELEVATOR_NO_MERGE;
447 
448 	__rq = elv_rb_find(&dd->sort_list[bio_data_dir(bio)], sector);
449 	if (__rq) {
450 		BUG_ON(sector != blk_rq_pos(__rq));
451 
452 		if (elv_bio_merge_ok(__rq, bio)) {
453 			*rq = __rq;
454 			return ELEVATOR_FRONT_MERGE;
455 		}
456 	}
457 
458 	return ELEVATOR_NO_MERGE;
459 }
460 
461 static bool dd_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio)
462 {
463 	struct request_queue *q = hctx->queue;
464 	struct deadline_data *dd = q->elevator->elevator_data;
465 	struct request *free = NULL;
466 	bool ret;
467 
468 	spin_lock(&dd->lock);
469 	ret = blk_mq_sched_try_merge(q, bio, &free);
470 	spin_unlock(&dd->lock);
471 
472 	if (free)
473 		blk_mq_free_request(free);
474 
475 	return ret;
476 }
477 
478 /*
479  * add rq to rbtree and fifo
480  */
481 static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
482 			      bool at_head)
483 {
484 	struct request_queue *q = hctx->queue;
485 	struct deadline_data *dd = q->elevator->elevator_data;
486 	const int data_dir = rq_data_dir(rq);
487 
488 	/*
489 	 * This may be a requeue of a write request that has locked its
490 	 * target zone. If it is the case, this releases the zone lock.
491 	 */
492 	blk_req_zone_write_unlock(rq);
493 
494 	if (blk_mq_sched_try_insert_merge(q, rq))
495 		return;
496 
497 	blk_mq_sched_request_inserted(rq);
498 
499 	if (at_head || blk_rq_is_passthrough(rq)) {
500 		if (at_head)
501 			list_add(&rq->queuelist, &dd->dispatch);
502 		else
503 			list_add_tail(&rq->queuelist, &dd->dispatch);
504 	} else {
505 		deadline_add_rq_rb(dd, rq);
506 
507 		if (rq_mergeable(rq)) {
508 			elv_rqhash_add(q, rq);
509 			if (!q->last_merge)
510 				q->last_merge = rq;
511 		}
512 
513 		/*
514 		 * set expire time and add to fifo list
515 		 */
516 		rq->fifo_time = jiffies + dd->fifo_expire[data_dir];
517 		list_add_tail(&rq->queuelist, &dd->fifo_list[data_dir]);
518 	}
519 }
520 
521 static void dd_insert_requests(struct blk_mq_hw_ctx *hctx,
522 			       struct list_head *list, bool at_head)
523 {
524 	struct request_queue *q = hctx->queue;
525 	struct deadline_data *dd = q->elevator->elevator_data;
526 
527 	spin_lock(&dd->lock);
528 	while (!list_empty(list)) {
529 		struct request *rq;
530 
531 		rq = list_first_entry(list, struct request, queuelist);
532 		list_del_init(&rq->queuelist);
533 		dd_insert_request(hctx, rq, at_head);
534 	}
535 	spin_unlock(&dd->lock);
536 }
537 
538 /*
539  * Nothing to do here. This is defined only to ensure that .finish_request
540  * method is called upon request completion.
541  */
542 static void dd_prepare_request(struct request *rq, struct bio *bio)
543 {
544 }
545 
546 /*
547  * For zoned block devices, write unlock the target zone of
548  * completed write requests. Do this while holding the zone lock
549  * spinlock so that the zone is never unlocked while deadline_fifo_request()
550  * or deadline_next_request() are executing. This function is called for
551  * all requests, whether or not these requests complete successfully.
552  */
553 static void dd_finish_request(struct request *rq)
554 {
555 	struct request_queue *q = rq->q;
556 
557 	if (blk_queue_is_zoned(q)) {
558 		struct deadline_data *dd = q->elevator->elevator_data;
559 		unsigned long flags;
560 
561 		spin_lock_irqsave(&dd->zone_lock, flags);
562 		blk_req_zone_write_unlock(rq);
563 		spin_unlock_irqrestore(&dd->zone_lock, flags);
564 	}
565 }
566 
567 static bool dd_has_work(struct blk_mq_hw_ctx *hctx)
568 {
569 	struct deadline_data *dd = hctx->queue->elevator->elevator_data;
570 
571 	return !list_empty_careful(&dd->dispatch) ||
572 		!list_empty_careful(&dd->fifo_list[0]) ||
573 		!list_empty_careful(&dd->fifo_list[1]);
574 }
575 
576 /*
577  * sysfs parts below
578  */
579 static ssize_t
580 deadline_var_show(int var, char *page)
581 {
582 	return sprintf(page, "%d\n", var);
583 }
584 
585 static void
586 deadline_var_store(int *var, const char *page)
587 {
588 	char *p = (char *) page;
589 
590 	*var = simple_strtol(p, &p, 10);
591 }
592 
593 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)				\
594 static ssize_t __FUNC(struct elevator_queue *e, char *page)		\
595 {									\
596 	struct deadline_data *dd = e->elevator_data;			\
597 	int __data = __VAR;						\
598 	if (__CONV)							\
599 		__data = jiffies_to_msecs(__data);			\
600 	return deadline_var_show(__data, (page));			\
601 }
602 SHOW_FUNCTION(deadline_read_expire_show, dd->fifo_expire[READ], 1);
603 SHOW_FUNCTION(deadline_write_expire_show, dd->fifo_expire[WRITE], 1);
604 SHOW_FUNCTION(deadline_writes_starved_show, dd->writes_starved, 0);
605 SHOW_FUNCTION(deadline_front_merges_show, dd->front_merges, 0);
606 SHOW_FUNCTION(deadline_fifo_batch_show, dd->fifo_batch, 0);
607 #undef SHOW_FUNCTION
608 
609 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)			\
610 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count)	\
611 {									\
612 	struct deadline_data *dd = e->elevator_data;			\
613 	int __data;							\
614 	deadline_var_store(&__data, (page));				\
615 	if (__data < (MIN))						\
616 		__data = (MIN);						\
617 	else if (__data > (MAX))					\
618 		__data = (MAX);						\
619 	if (__CONV)							\
620 		*(__PTR) = msecs_to_jiffies(__data);			\
621 	else								\
622 		*(__PTR) = __data;					\
623 	return count;							\
624 }
625 STORE_FUNCTION(deadline_read_expire_store, &dd->fifo_expire[READ], 0, INT_MAX, 1);
626 STORE_FUNCTION(deadline_write_expire_store, &dd->fifo_expire[WRITE], 0, INT_MAX, 1);
627 STORE_FUNCTION(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX, 0);
628 STORE_FUNCTION(deadline_front_merges_store, &dd->front_merges, 0, 1, 0);
629 STORE_FUNCTION(deadline_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX, 0);
630 #undef STORE_FUNCTION
631 
632 #define DD_ATTR(name) \
633 	__ATTR(name, 0644, deadline_##name##_show, deadline_##name##_store)
634 
635 static struct elv_fs_entry deadline_attrs[] = {
636 	DD_ATTR(read_expire),
637 	DD_ATTR(write_expire),
638 	DD_ATTR(writes_starved),
639 	DD_ATTR(front_merges),
640 	DD_ATTR(fifo_batch),
641 	__ATTR_NULL
642 };
643 
644 #ifdef CONFIG_BLK_DEBUG_FS
645 #define DEADLINE_DEBUGFS_DDIR_ATTRS(ddir, name)				\
646 static void *deadline_##name##_fifo_start(struct seq_file *m,		\
647 					  loff_t *pos)			\
648 	__acquires(&dd->lock)						\
649 {									\
650 	struct request_queue *q = m->private;				\
651 	struct deadline_data *dd = q->elevator->elevator_data;		\
652 									\
653 	spin_lock(&dd->lock);						\
654 	return seq_list_start(&dd->fifo_list[ddir], *pos);		\
655 }									\
656 									\
657 static void *deadline_##name##_fifo_next(struct seq_file *m, void *v,	\
658 					 loff_t *pos)			\
659 {									\
660 	struct request_queue *q = m->private;				\
661 	struct deadline_data *dd = q->elevator->elevator_data;		\
662 									\
663 	return seq_list_next(v, &dd->fifo_list[ddir], pos);		\
664 }									\
665 									\
666 static void deadline_##name##_fifo_stop(struct seq_file *m, void *v)	\
667 	__releases(&dd->lock)						\
668 {									\
669 	struct request_queue *q = m->private;				\
670 	struct deadline_data *dd = q->elevator->elevator_data;		\
671 									\
672 	spin_unlock(&dd->lock);						\
673 }									\
674 									\
675 static const struct seq_operations deadline_##name##_fifo_seq_ops = {	\
676 	.start	= deadline_##name##_fifo_start,				\
677 	.next	= deadline_##name##_fifo_next,				\
678 	.stop	= deadline_##name##_fifo_stop,				\
679 	.show	= blk_mq_debugfs_rq_show,				\
680 };									\
681 									\
682 static int deadline_##name##_next_rq_show(void *data,			\
683 					  struct seq_file *m)		\
684 {									\
685 	struct request_queue *q = data;					\
686 	struct deadline_data *dd = q->elevator->elevator_data;		\
687 	struct request *rq = dd->next_rq[ddir];				\
688 									\
689 	if (rq)								\
690 		__blk_mq_debugfs_rq_show(m, rq);			\
691 	return 0;							\
692 }
693 DEADLINE_DEBUGFS_DDIR_ATTRS(READ, read)
694 DEADLINE_DEBUGFS_DDIR_ATTRS(WRITE, write)
695 #undef DEADLINE_DEBUGFS_DDIR_ATTRS
696 
697 static int deadline_batching_show(void *data, struct seq_file *m)
698 {
699 	struct request_queue *q = data;
700 	struct deadline_data *dd = q->elevator->elevator_data;
701 
702 	seq_printf(m, "%u\n", dd->batching);
703 	return 0;
704 }
705 
706 static int deadline_starved_show(void *data, struct seq_file *m)
707 {
708 	struct request_queue *q = data;
709 	struct deadline_data *dd = q->elevator->elevator_data;
710 
711 	seq_printf(m, "%u\n", dd->starved);
712 	return 0;
713 }
714 
715 static void *deadline_dispatch_start(struct seq_file *m, loff_t *pos)
716 	__acquires(&dd->lock)
717 {
718 	struct request_queue *q = m->private;
719 	struct deadline_data *dd = q->elevator->elevator_data;
720 
721 	spin_lock(&dd->lock);
722 	return seq_list_start(&dd->dispatch, *pos);
723 }
724 
725 static void *deadline_dispatch_next(struct seq_file *m, void *v, loff_t *pos)
726 {
727 	struct request_queue *q = m->private;
728 	struct deadline_data *dd = q->elevator->elevator_data;
729 
730 	return seq_list_next(v, &dd->dispatch, pos);
731 }
732 
733 static void deadline_dispatch_stop(struct seq_file *m, void *v)
734 	__releases(&dd->lock)
735 {
736 	struct request_queue *q = m->private;
737 	struct deadline_data *dd = q->elevator->elevator_data;
738 
739 	spin_unlock(&dd->lock);
740 }
741 
742 static const struct seq_operations deadline_dispatch_seq_ops = {
743 	.start	= deadline_dispatch_start,
744 	.next	= deadline_dispatch_next,
745 	.stop	= deadline_dispatch_stop,
746 	.show	= blk_mq_debugfs_rq_show,
747 };
748 
749 #define DEADLINE_QUEUE_DDIR_ATTRS(name)						\
750 	{#name "_fifo_list", 0400, .seq_ops = &deadline_##name##_fifo_seq_ops},	\
751 	{#name "_next_rq", 0400, deadline_##name##_next_rq_show}
752 static const struct blk_mq_debugfs_attr deadline_queue_debugfs_attrs[] = {
753 	DEADLINE_QUEUE_DDIR_ATTRS(read),
754 	DEADLINE_QUEUE_DDIR_ATTRS(write),
755 	{"batching", 0400, deadline_batching_show},
756 	{"starved", 0400, deadline_starved_show},
757 	{"dispatch", 0400, .seq_ops = &deadline_dispatch_seq_ops},
758 	{},
759 };
760 #undef DEADLINE_QUEUE_DDIR_ATTRS
761 #endif
762 
763 static struct elevator_type mq_deadline = {
764 	.ops.mq = {
765 		.insert_requests	= dd_insert_requests,
766 		.dispatch_request	= dd_dispatch_request,
767 		.prepare_request	= dd_prepare_request,
768 		.finish_request		= dd_finish_request,
769 		.next_request		= elv_rb_latter_request,
770 		.former_request		= elv_rb_former_request,
771 		.bio_merge		= dd_bio_merge,
772 		.request_merge		= dd_request_merge,
773 		.requests_merged	= dd_merged_requests,
774 		.request_merged		= dd_request_merged,
775 		.has_work		= dd_has_work,
776 		.init_sched		= dd_init_queue,
777 		.exit_sched		= dd_exit_queue,
778 	},
779 
780 	.uses_mq	= true,
781 #ifdef CONFIG_BLK_DEBUG_FS
782 	.queue_debugfs_attrs = deadline_queue_debugfs_attrs,
783 #endif
784 	.elevator_attrs = deadline_attrs,
785 	.elevator_name = "mq-deadline",
786 	.elevator_alias = "deadline",
787 	.elevator_owner = THIS_MODULE,
788 };
789 MODULE_ALIAS("mq-deadline-iosched");
790 
791 static int __init deadline_init(void)
792 {
793 	return elv_register(&mq_deadline);
794 }
795 
796 static void __exit deadline_exit(void)
797 {
798 	elv_unregister(&mq_deadline);
799 }
800 
801 module_init(deadline_init);
802 module_exit(deadline_exit);
803 
804 MODULE_AUTHOR("Jens Axboe");
805 MODULE_LICENSE("GPL");
806 MODULE_DESCRIPTION("MQ deadline IO scheduler");
807