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

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  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 may return a request that is 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  * For a zoned block device, __dd_dispatch_request() may return NULL
381  * if all the queued write requests are directed at zones that are already
382  * locked due to on-going write requests. In this case, make sure to mark
383  * the queue as needing a restart to ensure that the queue is run again
384  * and the pending writes dispatched once the target zones for the ongoing
385  * write requests are unlocked in dd_finish_request().
386  */
387 static struct request *dd_dispatch_request(struct blk_mq_hw_ctx *hctx)
388 {
389         struct deadline_data *dd = hctx->queue->elevator->elevator_data;
390         struct request *rq;
391 
392         spin_lock(&dd->lock);
393         rq = __dd_dispatch_request(dd);
394         if (!rq && blk_queue_is_zoned(hctx->queue) &&
395             !list_empty(&dd->fifo_list[WRITE]))
396                 blk_mq_sched_mark_restart_hctx(hctx);
397         spin_unlock(&dd->lock);
398 
399         return rq;
400 }
401 
402 static void dd_exit_queue(struct elevator_queue *e)
403 {
404         struct deadline_data *dd = e->elevator_data;
405 
406         BUG_ON(!list_empty(&dd->fifo_list[READ]));
407         BUG_ON(!list_empty(&dd->fifo_list[WRITE]));
408 
409         kfree(dd);
410 }
411 
412 /*
413  * initialize elevator private data (deadline_data).
414  */
415 static int dd_init_queue(struct request_queue *q, struct elevator_type *e)
416 {
417         struct deadline_data *dd;
418         struct elevator_queue *eq;
419 
420         eq = elevator_alloc(q, e);
421         if (!eq)
422                 return -ENOMEM;
423 
424         dd = kzalloc_node(sizeof(*dd), GFP_KERNEL, q->node);
425         if (!dd) {
426                 kobject_put(&eq->kobj);
427                 return -ENOMEM;
428         }
429         eq->elevator_data = dd;
430 
431         INIT_LIST_HEAD(&dd->fifo_list[READ]);
432         INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
433         dd->sort_list[READ] = RB_ROOT;
434         dd->sort_list[WRITE] = RB_ROOT;
435         dd->fifo_expire[READ] = read_expire;
436         dd->fifo_expire[WRITE] = write_expire;
437         dd->writes_starved = writes_starved;
438         dd->front_merges = 1;
439         dd->fifo_batch = fifo_batch;
440         spin_lock_init(&dd->lock);
441         spin_lock_init(&dd->zone_lock);
442         INIT_LIST_HEAD(&dd->dispatch);
443 
444         q->elevator = eq;
445         return 0;
446 }
447 
448 static int dd_request_merge(struct request_queue *q, struct request **rq,
449                             struct bio *bio)
450 {
451         struct deadline_data *dd = q->elevator->elevator_data;
452         sector_t sector = bio_end_sector(bio);
453         struct request *__rq;
454 
455         if (!dd->front_merges)
456                 return ELEVATOR_NO_MERGE;
457 
458         __rq = elv_rb_find(&dd->sort_list[bio_data_dir(bio)], sector);
459         if (__rq) {
460                 BUG_ON(sector != blk_rq_pos(__rq));
461 
462                 if (elv_bio_merge_ok(__rq, bio)) {
463                         *rq = __rq;
464                         return ELEVATOR_FRONT_MERGE;
465                 }
466         }
467 
468         return ELEVATOR_NO_MERGE;
469 }
470 
471 static bool dd_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio)
472 {
473         struct request_queue *q = hctx->queue;
474         struct deadline_data *dd = q->elevator->elevator_data;
475         struct request *free = NULL;
476         bool ret;
477 
478         spin_lock(&dd->lock);
479         ret = blk_mq_sched_try_merge(q, bio, &free);
480         spin_unlock(&dd->lock);
481 
482         if (free)
483                 blk_mq_free_request(free);
484 
485         return ret;
486 }
487 
488 /*
489  * add rq to rbtree and fifo
490  */
491 static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
492                               bool at_head)
493 {
494         struct request_queue *q = hctx->queue;
495         struct deadline_data *dd = q->elevator->elevator_data;
496         const int data_dir = rq_data_dir(rq);
497 
498         /*
499          * This may be a requeue of a write request that has locked its
500          * target zone. If it is the case, this releases the zone lock.
501          */
502         blk_req_zone_write_unlock(rq);
503 
504         if (blk_mq_sched_try_insert_merge(q, rq))
505                 return;
506 
507         blk_mq_sched_request_inserted(rq);
508 
509         if (at_head || blk_rq_is_passthrough(rq)) {
510                 if (at_head)
511                         list_add(&rq->queuelist, &dd->dispatch);
512                 else
513                         list_add_tail(&rq->queuelist, &dd->dispatch);
514         } else {
515                 deadline_add_rq_rb(dd, rq);
516 
517                 if (rq_mergeable(rq)) {
518                         elv_rqhash_add(q, rq);
519                         if (!q->last_merge)
520                                 q->last_merge = rq;
521                 }
522 
523                 /*
524                  * set expire time and add to fifo list
525                  */
526                 rq->fifo_time = jiffies + dd->fifo_expire[data_dir];
527                 list_add_tail(&rq->queuelist, &dd->fifo_list[data_dir]);
528         }
529 }
530 
531 static void dd_insert_requests(struct blk_mq_hw_ctx *hctx,
532                                struct list_head *list, bool at_head)
533 {
534         struct request_queue *q = hctx->queue;
535         struct deadline_data *dd = q->elevator->elevator_data;
536 
537         spin_lock(&dd->lock);
538         while (!list_empty(list)) {
539                 struct request *rq;
540 
541                 rq = list_first_entry(list, struct request, queuelist);
542                 list_del_init(&rq->queuelist);
543                 dd_insert_request(hctx, rq, at_head);
544         }
545         spin_unlock(&dd->lock);
546 }
547 
548 /*
549  * Nothing to do here. This is defined only to ensure that .finish_request
550  * method is called upon request completion.
551  */
552 static void dd_prepare_request(struct request *rq, struct bio *bio)
553 {
554 }
555 
556 /*
557  * For zoned block devices, write unlock the target zone of
558  * completed write requests. Do this while holding the zone lock
559  * spinlock so that the zone is never unlocked while deadline_fifo_request()
560  * or deadline_next_request() are executing. This function is called for
561  * all requests, whether or not these requests complete successfully.
562  */
563 static void dd_finish_request(struct request *rq)
564 {
565         struct request_queue *q = rq->q;
566 
567         if (blk_queue_is_zoned(q)) {
568                 struct deadline_data *dd = q->elevator->elevator_data;
569                 unsigned long flags;
570 
571                 spin_lock_irqsave(&dd->zone_lock, flags);
572                 blk_req_zone_write_unlock(rq);
573                 spin_unlock_irqrestore(&dd->zone_lock, flags);
574         }
575 }
576 
577 static bool dd_has_work(struct blk_mq_hw_ctx *hctx)
578 {
579         struct deadline_data *dd = hctx->queue->elevator->elevator_data;
580 
581         return !list_empty_careful(&dd->dispatch) ||
582                 !list_empty_careful(&dd->fifo_list[0]) ||
583                 !list_empty_careful(&dd->fifo_list[1]);
584 }
585 
586 /*
587  * sysfs parts below
588  */
589 static ssize_t
590 deadline_var_show(int var, char *page)
591 {
592         return sprintf(page, "%d\n", var);
593 }
594 
595 static void
596 deadline_var_store(int *var, const char *page)
597 {
598         char *p = (char *) page;
599 
600         *var = simple_strtol(p, &p, 10);
601 }
602 
603 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)                            \
604 static ssize_t __FUNC(struct elevator_queue *e, char *page)             \
605 {                                                                       \
606         struct deadline_data *dd = e->elevator_data;                    \
607         int __data = __VAR;                                             \
608         if (__CONV)                                                     \
609                 __data = jiffies_to_msecs(__data);                      \
610         return deadline_var_show(__data, (page));                       \
611 }
612 SHOW_FUNCTION(deadline_read_expire_show, dd->fifo_expire[READ], 1);
613 SHOW_FUNCTION(deadline_write_expire_show, dd->fifo_expire[WRITE], 1);
614 SHOW_FUNCTION(deadline_writes_starved_show, dd->writes_starved, 0);
615 SHOW_FUNCTION(deadline_front_merges_show, dd->front_merges, 0);
616 SHOW_FUNCTION(deadline_fifo_batch_show, dd->fifo_batch, 0);
617 #undef SHOW_FUNCTION
618 
619 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
620 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
621 {                                                                       \
622         struct deadline_data *dd = e->elevator_data;                    \
623         int __data;                                                     \
624         deadline_var_store(&__data, (page));                            \
625         if (__data < (MIN))                                             \
626                 __data = (MIN);                                         \
627         else if (__data > (MAX))                                        \
628                 __data = (MAX);                                         \
629         if (__CONV)                                                     \
630                 *(__PTR) = msecs_to_jiffies(__data);                    \
631         else                                                            \
632                 *(__PTR) = __data;                                      \
633         return count;                                                   \
634 }
635 STORE_FUNCTION(deadline_read_expire_store, &dd->fifo_expire[READ], 0, INT_MAX, 1);
636 STORE_FUNCTION(deadline_write_expire_store, &dd->fifo_expire[WRITE], 0, INT_MAX, 1);
637 STORE_FUNCTION(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX, 0);
638 STORE_FUNCTION(deadline_front_merges_store, &dd->front_merges, 0, 1, 0);
639 STORE_FUNCTION(deadline_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX, 0);
640 #undef STORE_FUNCTION
641 
642 #define DD_ATTR(name) \
643         __ATTR(name, 0644, deadline_##name##_show, deadline_##name##_store)
644 
645 static struct elv_fs_entry deadline_attrs[] = {
646         DD_ATTR(read_expire),
647         DD_ATTR(write_expire),
648         DD_ATTR(writes_starved),
649         DD_ATTR(front_merges),
650         DD_ATTR(fifo_batch),
651         __ATTR_NULL
652 };
653 
654 #ifdef CONFIG_BLK_DEBUG_FS
655 #define DEADLINE_DEBUGFS_DDIR_ATTRS(ddir, name)                         \
656 static void *deadline_##name##_fifo_start(struct seq_file *m,           \
657                                           loff_t *pos)                  \
658         __acquires(&dd->lock)                                           \
659 {                                                                       \
660         struct request_queue *q = m->private;                           \
661         struct deadline_data *dd = q->elevator->elevator_data;          \
662                                                                         \
663         spin_lock(&dd->lock);                                           \
664         return seq_list_start(&dd->fifo_list[ddir], *pos);              \
665 }                                                                       \
666                                                                         \
667 static void *deadline_##name##_fifo_next(struct seq_file *m, void *v,   \
668                                          loff_t *pos)                   \
669 {                                                                       \
670         struct request_queue *q = m->private;                           \
671         struct deadline_data *dd = q->elevator->elevator_data;          \
672                                                                         \
673         return seq_list_next(v, &dd->fifo_list[ddir], pos);             \
674 }                                                                       \
675                                                                         \
676 static void deadline_##name##_fifo_stop(struct seq_file *m, void *v)    \
677         __releases(&dd->lock)                                           \
678 {                                                                       \
679         struct request_queue *q = m->private;                           \
680         struct deadline_data *dd = q->elevator->elevator_data;          \
681                                                                         \
682         spin_unlock(&dd->lock);                                         \
683 }                                                                       \
684                                                                         \
685 static const struct seq_operations deadline_##name##_fifo_seq_ops = {   \
686         .start  = deadline_##name##_fifo_start,                         \
687         .next   = deadline_##name##_fifo_next,                          \
688         .stop   = deadline_##name##_fifo_stop,                          \
689         .show   = blk_mq_debugfs_rq_show,                               \
690 };                                                                      \
691                                                                         \
692 static int deadline_##name##_next_rq_show(void *data,                   \
693                                           struct seq_file *m)           \
694 {                                                                       \
695         struct request_queue *q = data;                                 \
696         struct deadline_data *dd = q->elevator->elevator_data;          \
697         struct request *rq = dd->next_rq[ddir];                         \
698                                                                         \
699         if (rq)                                                         \
700                 __blk_mq_debugfs_rq_show(m, rq);                        \
701         return 0;                                                       \
702 }
703 DEADLINE_DEBUGFS_DDIR_ATTRS(READ, read)
704 DEADLINE_DEBUGFS_DDIR_ATTRS(WRITE, write)
705 #undef DEADLINE_DEBUGFS_DDIR_ATTRS
706 
707 static int deadline_batching_show(void *data, struct seq_file *m)
708 {
709         struct request_queue *q = data;
710         struct deadline_data *dd = q->elevator->elevator_data;
711 
712         seq_printf(m, "%u\n", dd->batching);
713         return 0;
714 }
715 
716 static int deadline_starved_show(void *data, struct seq_file *m)
717 {
718         struct request_queue *q = data;
719         struct deadline_data *dd = q->elevator->elevator_data;
720 
721         seq_printf(m, "%u\n", dd->starved);
722         return 0;
723 }
724 
725 static void *deadline_dispatch_start(struct seq_file *m, loff_t *pos)
726         __acquires(&dd->lock)
727 {
728         struct request_queue *q = m->private;
729         struct deadline_data *dd = q->elevator->elevator_data;
730 
731         spin_lock(&dd->lock);
732         return seq_list_start(&dd->dispatch, *pos);
733 }
734 
735 static void *deadline_dispatch_next(struct seq_file *m, void *v, loff_t *pos)
736 {
737         struct request_queue *q = m->private;
738         struct deadline_data *dd = q->elevator->elevator_data;
739 
740         return seq_list_next(v, &dd->dispatch, pos);
741 }
742 
743 static void deadline_dispatch_stop(struct seq_file *m, void *v)
744         __releases(&dd->lock)
745 {
746         struct request_queue *q = m->private;
747         struct deadline_data *dd = q->elevator->elevator_data;
748 
749         spin_unlock(&dd->lock);
750 }
751 
752 static const struct seq_operations deadline_dispatch_seq_ops = {
753         .start  = deadline_dispatch_start,
754         .next   = deadline_dispatch_next,
755         .stop   = deadline_dispatch_stop,
756         .show   = blk_mq_debugfs_rq_show,
757 };
758 
759 #define DEADLINE_QUEUE_DDIR_ATTRS(name)                                         \
760         {#name "_fifo_list", 0400, .seq_ops = &deadline_##name##_fifo_seq_ops}, \
761         {#name "_next_rq", 0400, deadline_##name##_next_rq_show}
762 static const struct blk_mq_debugfs_attr deadline_queue_debugfs_attrs[] = {
763         DEADLINE_QUEUE_DDIR_ATTRS(read),
764         DEADLINE_QUEUE_DDIR_ATTRS(write),
765         {"batching", 0400, deadline_batching_show},
766         {"starved", 0400, deadline_starved_show},
767         {"dispatch", 0400, .seq_ops = &deadline_dispatch_seq_ops},
768         {},
769 };
770 #undef DEADLINE_QUEUE_DDIR_ATTRS
771 #endif
772 
773 static struct elevator_type mq_deadline = {
774         .ops = {
775                 .insert_requests        = dd_insert_requests,
776                 .dispatch_request       = dd_dispatch_request,
777                 .prepare_request        = dd_prepare_request,
778                 .finish_request         = dd_finish_request,
779                 .next_request           = elv_rb_latter_request,
780                 .former_request         = elv_rb_former_request,
781                 .bio_merge              = dd_bio_merge,
782                 .request_merge          = dd_request_merge,
783                 .requests_merged        = dd_merged_requests,
784                 .request_merged         = dd_request_merged,
785                 .has_work               = dd_has_work,
786                 .init_sched             = dd_init_queue,
787                 .exit_sched             = dd_exit_queue,
788         },
789 
790 #ifdef CONFIG_BLK_DEBUG_FS
791         .queue_debugfs_attrs = deadline_queue_debugfs_attrs,
792 #endif
793         .elevator_attrs = deadline_attrs,
794         .elevator_name = "mq-deadline",
795         .elevator_alias = "deadline",
796         .elevator_owner = THIS_MODULE,
797 };
798 MODULE_ALIAS("mq-deadline-iosched");
799 
800 static int __init deadline_init(void)
801 {
802         return elv_register(&mq_deadline);
803 }
804 
805 static void __exit deadline_exit(void)
806 {
807         elv_unregister(&mq_deadline);
808 }
809 
810 module_init(deadline_init);
811 module_exit(deadline_exit);
812 
813 MODULE_AUTHOR("Jens Axboe");
814 MODULE_LICENSE("GPL");
815 MODULE_DESCRIPTION("MQ deadline IO scheduler");
816 

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