1/*
2 * buffered writeback throttling. loosely based on CoDel. We can't drop
3 * packets for IO scheduling, so the logic is something like this:
4 *
5 * - Monitor latencies in a defined window of time.
6 * - If the minimum latency in the above window exceeds some target, increment
7 * scaling step and scale down queue depth by a factor of 2x. The monitoring
8 * window is then shrunk to 100 / sqrt(scaling step + 1).
9 * - For any window where we don't have solid data on what the latencies
10 * look like, retain status quo.
11 * - If latencies look good, decrement scaling step.
12 * - If we're only doing writes, allow the scaling step to go negative. This
13 * will temporarily boost write performance, snapping back to a stable
14 * scaling step of 0 if reads show up or the heavy writers finish. Unlike
15 * positive scaling steps where we shrink the monitoring window, a negative
16 * scaling step retains the default step==0 window size.
17 *
18 * Copyright (C) 2016 Jens Axboe
19 *
20 */
21#include <linux/kernel.h>
22#include <linux/blk_types.h>
23#include <linux/slab.h>
24#include <linux/backing-dev.h>
25#include <linux/swap.h>
26
27#include "blk-wbt.h"
28#include "blk-rq-qos.h"
29
30#define CREATE_TRACE_POINTS
31#include <trace/events/wbt.h>
32
33static inline void wbt_clear_state(struct request *rq)
34{
35 rq->wbt_flags = 0;
36}
37
38static inline enum wbt_flags wbt_flags(struct request *rq)
39{
40 return rq->wbt_flags;
41}
42
43static inline bool wbt_is_tracked(struct request *rq)
44{
45 return rq->wbt_flags & WBT_TRACKED;
46}
47
48static inline bool wbt_is_read(struct request *rq)
49{
50 return rq->wbt_flags & WBT_READ;
51}
52
53enum {
54 /*
55 * Default setting, we'll scale up (to 75% of QD max) or down (min 1)
56 * from here depending on device stats
57 */
58 RWB_DEF_DEPTH = 16,
59
60 /*
61 * 100msec window
62 */
63 RWB_WINDOW_NSEC = 100 * 1000 * 1000ULL,
64
65 /*
66 * Disregard stats, if we don't meet this minimum
67 */
68 RWB_MIN_WRITE_SAMPLES = 3,
69
70 /*
71 * If we have this number of consecutive windows with not enough
72 * information to scale up or down, scale up.
73 */
74 RWB_UNKNOWN_BUMP = 5,
75};
76
77static inline bool rwb_enabled(struct rq_wb *rwb)
78{
79 return rwb && rwb->wb_normal != 0;
80}
81
82static void wb_timestamp(struct rq_wb *rwb, unsigned long *var)
83{
84 if (rwb_enabled(rwb)) {
85 const unsigned long cur = jiffies;
86
87 if (cur != *var)
88 *var = cur;
89 }
90}
91
92/*
93 * If a task was rate throttled in balance_dirty_pages() within the last
94 * second or so, use that to indicate a higher cleaning rate.
95 */
96static bool wb_recent_wait(struct rq_wb *rwb)
97{
98 struct bdi_writeback *wb = &rwb->rqos.q->backing_dev_info->wb;
99
100 return time_before(jiffies, wb->dirty_sleep + HZ);
101}
102
103static inline struct rq_wait *get_rq_wait(struct rq_wb *rwb,
104 enum wbt_flags wb_acct)
105{
106 if (wb_acct & WBT_KSWAPD)
107 return &rwb->rq_wait[WBT_RWQ_KSWAPD];
108 else if (wb_acct & WBT_DISCARD)
109 return &rwb->rq_wait[WBT_RWQ_DISCARD];
110
111 return &rwb->rq_wait[WBT_RWQ_BG];
112}
113
114static void rwb_wake_all(struct rq_wb *rwb)
115{
116 int i;
117
118 for (i = 0; i < WBT_NUM_RWQ; i++) {
119 struct rq_wait *rqw = &rwb->rq_wait[i];
120
121 if (wq_has_sleeper(&rqw->wait))
122 wake_up_all(&rqw->wait);
123 }
124}
125
126static void wbt_rqw_done(struct rq_wb *rwb, struct rq_wait *rqw,
127 enum wbt_flags wb_acct)
128{
129 int inflight, limit;
130
131 inflight = atomic_dec_return(&rqw->inflight);
132
133 /*
134 * wbt got disabled with IO in flight. Wake up any potential
135 * waiters, we don't have to do more than that.
136 */
137 if (unlikely(!rwb_enabled(rwb))) {
138 rwb_wake_all(rwb);
139 return;
140 }
141
142 /*
143 * For discards, our limit is always the background. For writes, if
144 * the device does write back caching, drop further down before we
145 * wake people up.
146 */
147 if (wb_acct & WBT_DISCARD)
148 limit = rwb->wb_background;
149 else if (rwb->wc && !wb_recent_wait(rwb))
150 limit = 0;
151 else
152 limit = rwb->wb_normal;
153
154 /*
155 * Don't wake anyone up if we are above the normal limit.
156 */
157 if (inflight && inflight >= limit)
158 return;
159
160 if (wq_has_sleeper(&rqw->wait)) {
161 int diff = limit - inflight;
162
163 if (!inflight || diff >= rwb->wb_background / 2)
164 wake_up_all(&rqw->wait);
165 }
166}
167
168static void __wbt_done(struct rq_qos *rqos, enum wbt_flags wb_acct)
169{
170 struct rq_wb *rwb = RQWB(rqos);
171 struct rq_wait *rqw;
172
173 if (!(wb_acct & WBT_TRACKED))
174 return;
175
176 rqw = get_rq_wait(rwb, wb_acct);
177 wbt_rqw_done(rwb, rqw, wb_acct);
178}
179
180/*
181 * Called on completion of a request. Note that it's also called when
182 * a request is merged, when the request gets freed.
183 */
184static void wbt_done(struct rq_qos *rqos, struct request *rq)
185{
186 struct rq_wb *rwb = RQWB(rqos);
187
188 if (!wbt_is_tracked(rq)) {
189 if (rwb->sync_cookie == rq) {
190 rwb->sync_issue = 0;
191 rwb->sync_cookie = NULL;
192 }
193
194 if (wbt_is_read(rq))
195 wb_timestamp(rwb, &rwb->last_comp);
196 } else {
197 WARN_ON_ONCE(rq == rwb->sync_cookie);
198 __wbt_done(rqos, wbt_flags(rq));
199 }
200 wbt_clear_state(rq);
201}
202
203static inline bool stat_sample_valid(struct blk_rq_stat *stat)
204{
205 /*
206 * We need at least one read sample, and a minimum of
207 * RWB_MIN_WRITE_SAMPLES. We require some write samples to know
208 * that it's writes impacting us, and not just some sole read on
209 * a device that is in a lower power state.
210 */
211 return (stat[READ].nr_samples >= 1 &&
212 stat[WRITE].nr_samples >= RWB_MIN_WRITE_SAMPLES);
213}
214
215static u64 rwb_sync_issue_lat(struct rq_wb *rwb)
216{
217 u64 now, issue = READ_ONCE(rwb->sync_issue);
218
219 if (!issue || !rwb->sync_cookie)
220 return 0;
221
222 now = ktime_to_ns(ktime_get());
223 return now - issue;
224}
225
226enum {
227 LAT_OK = 1,
228 LAT_UNKNOWN,
229 LAT_UNKNOWN_WRITES,
230 LAT_EXCEEDED,
231};
232
233static int latency_exceeded(struct rq_wb *rwb, struct blk_rq_stat *stat)
234{
235 struct backing_dev_info *bdi = rwb->rqos.q->backing_dev_info;
236 struct rq_depth *rqd = &rwb->rq_depth;
237 u64 thislat;
238
239 /*
240 * If our stored sync issue exceeds the window size, or it
241 * exceeds our min target AND we haven't logged any entries,
242 * flag the latency as exceeded. wbt works off completion latencies,
243 * but for a flooded device, a single sync IO can take a long time
244 * to complete after being issued. If this time exceeds our
245 * monitoring window AND we didn't see any other completions in that
246 * window, then count that sync IO as a violation of the latency.
247 */
248 thislat = rwb_sync_issue_lat(rwb);
249 if (thislat > rwb->cur_win_nsec ||
250 (thislat > rwb->min_lat_nsec && !stat[READ].nr_samples)) {
251 trace_wbt_lat(bdi, thislat);
252 return LAT_EXCEEDED;
253 }
254
255 /*
256 * No read/write mix, if stat isn't valid
257 */
258 if (!stat_sample_valid(stat)) {
259 /*
260 * If we had writes in this stat window and the window is
261 * current, we're only doing writes. If a task recently
262 * waited or still has writes in flights, consider us doing
263 * just writes as well.
264 */
265 if (stat[WRITE].nr_samples || wb_recent_wait(rwb) ||
266 wbt_inflight(rwb))
267 return LAT_UNKNOWN_WRITES;
268 return LAT_UNKNOWN;
269 }
270
271 /*
272 * If the 'min' latency exceeds our target, step down.
273 */
274 if (stat[READ].min > rwb->min_lat_nsec) {
275 trace_wbt_lat(bdi, stat[READ].min);
276 trace_wbt_stat(bdi, stat);
277 return LAT_EXCEEDED;
278 }
279
280 if (rqd->scale_step)
281 trace_wbt_stat(bdi, stat);
282
283 return LAT_OK;
284}
285
286static void rwb_trace_step(struct rq_wb *rwb, const char *msg)
287{
288 struct backing_dev_info *bdi = rwb->rqos.q->backing_dev_info;
289 struct rq_depth *rqd = &rwb->rq_depth;
290
291 trace_wbt_step(bdi, msg, rqd->scale_step, rwb->cur_win_nsec,
292 rwb->wb_background, rwb->wb_normal, rqd->max_depth);
293}
294
295static void calc_wb_limits(struct rq_wb *rwb)
296{
297 if (rwb->min_lat_nsec == 0) {
298 rwb->wb_normal = rwb->wb_background = 0;
299 } else if (rwb->rq_depth.max_depth <= 2) {
300 rwb->wb_normal = rwb->rq_depth.max_depth;
301 rwb->wb_background = 1;
302 } else {
303 rwb->wb_normal = (rwb->rq_depth.max_depth + 1) / 2;
304 rwb->wb_background = (rwb->rq_depth.max_depth + 3) / 4;
305 }
306}
307
308static void scale_up(struct rq_wb *rwb)
309{
310 rq_depth_scale_up(&rwb->rq_depth);
311 calc_wb_limits(rwb);
312 rwb->unknown_cnt = 0;
313 rwb_wake_all(rwb);
314 rwb_trace_step(rwb, "scale up");
315}
316
317static void scale_down(struct rq_wb *rwb, bool hard_throttle)
318{
319 rq_depth_scale_down(&rwb->rq_depth, hard_throttle);
320 calc_wb_limits(rwb);
321 rwb->unknown_cnt = 0;
322 rwb_trace_step(rwb, "scale down");
323}
324
325static void rwb_arm_timer(struct rq_wb *rwb)
326{
327 struct rq_depth *rqd = &rwb->rq_depth;
328
329 if (rqd->scale_step > 0) {
330 /*
331 * We should speed this up, using some variant of a fast
332 * integer inverse square root calculation. Since we only do
333 * this for every window expiration, it's not a huge deal,
334 * though.
335 */
336 rwb->cur_win_nsec = div_u64(rwb->win_nsec << 4,
337 int_sqrt((rqd->scale_step + 1) << 8));
338 } else {
339 /*
340 * For step < 0, we don't want to increase/decrease the
341 * window size.
342 */
343 rwb->cur_win_nsec = rwb->win_nsec;
344 }
345
346 blk_stat_activate_nsecs(rwb->cb, rwb->cur_win_nsec);
347}
348
349static void wb_timer_fn(struct blk_stat_callback *cb)
350{
351 struct rq_wb *rwb = cb->data;
352 struct rq_depth *rqd = &rwb->rq_depth;
353 unsigned int inflight = wbt_inflight(rwb);
354 int status;
355
356 status = latency_exceeded(rwb, cb->stat);
357
358 trace_wbt_timer(rwb->rqos.q->backing_dev_info, status, rqd->scale_step,
359 inflight);
360
361 /*
362 * If we exceeded the latency target, step down. If we did not,
363 * step one level up. If we don't know enough to say either exceeded
364 * or ok, then don't do anything.
365 */
366 switch (status) {
367 case LAT_EXCEEDED:
368 scale_down(rwb, true);
369 break;
370 case LAT_OK:
371 scale_up(rwb);
372 break;
373 case LAT_UNKNOWN_WRITES:
374 /*
375 * We started a the center step, but don't have a valid
376 * read/write sample, but we do have writes going on.
377 * Allow step to go negative, to increase write perf.
378 */
379 scale_up(rwb);
380 break;
381 case LAT_UNKNOWN:
382 if (++rwb->unknown_cnt < RWB_UNKNOWN_BUMP)
383 break;
384 /*
385 * We get here when previously scaled reduced depth, and we
386 * currently don't have a valid read/write sample. For that
387 * case, slowly return to center state (step == 0).
388 */
389 if (rqd->scale_step > 0)
390 scale_up(rwb);
391 else if (rqd->scale_step < 0)
392 scale_down(rwb, false);
393 break;
394 default:
395 break;
396 }
397
398 /*
399 * Re-arm timer, if we have IO in flight
400 */
401 if (rqd->scale_step || inflight)
402 rwb_arm_timer(rwb);
403}
404
405static void __wbt_update_limits(struct rq_wb *rwb)
406{
407 struct rq_depth *rqd = &rwb->rq_depth;
408
409 rqd->scale_step = 0;
410 rqd->scaled_max = false;
411
412 rq_depth_calc_max_depth(rqd);
413 calc_wb_limits(rwb);
414
415 rwb_wake_all(rwb);
416}
417
418void wbt_update_limits(struct request_queue *q)
419{
420 struct rq_qos *rqos = wbt_rq_qos(q);
421 if (!rqos)
422 return;
423 __wbt_update_limits(RQWB(rqos));
424}
425
426u64 wbt_get_min_lat(struct request_queue *q)
427{
428 struct rq_qos *rqos = wbt_rq_qos(q);
429 if (!rqos)
430 return 0;
431 return RQWB(rqos)->min_lat_nsec;
432}
433
434void wbt_set_min_lat(struct request_queue *q, u64 val)
435{
436 struct rq_qos *rqos = wbt_rq_qos(q);
437 if (!rqos)
438 return;
439 RQWB(rqos)->min_lat_nsec = val;
440 RQWB(rqos)->enable_state = WBT_STATE_ON_MANUAL;
441 __wbt_update_limits(RQWB(rqos));
442}
443
444
445static bool close_io(struct rq_wb *rwb)
446{
447 const unsigned long now = jiffies;
448
449 return time_before(now, rwb->last_issue + HZ / 10) ||
450 time_before(now, rwb->last_comp + HZ / 10);
451}
452
453#define REQ_HIPRIO (REQ_SYNC | REQ_META | REQ_PRIO)
454
455static inline unsigned int get_limit(struct rq_wb *rwb, unsigned long rw)
456{
457 unsigned int limit;
458
459 /*
460 * If we got disabled, just return UINT_MAX. This ensures that
461 * we'll properly inc a new IO, and dec+wakeup at the end.
462 */
463 if (!rwb_enabled(rwb))
464 return UINT_MAX;
465
466 if ((rw & REQ_OP_MASK) == REQ_OP_DISCARD)
467 return rwb->wb_background;
468
469 /*
470 * At this point we know it's a buffered write. If this is
471 * kswapd trying to free memory, or REQ_SYNC is set, then
472 * it's WB_SYNC_ALL writeback, and we'll use the max limit for
473 * that. If the write is marked as a background write, then use
474 * the idle limit, or go to normal if we haven't had competing
475 * IO for a bit.
476 */
477 if ((rw & REQ_HIPRIO) || wb_recent_wait(rwb) || current_is_kswapd())
478 limit = rwb->rq_depth.max_depth;
479 else if ((rw & REQ_BACKGROUND) || close_io(rwb)) {
480 /*
481 * If less than 100ms since we completed unrelated IO,
482 * limit us to half the depth for background writeback.
483 */
484 limit = rwb->wb_background;
485 } else
486 limit = rwb->wb_normal;
487
488 return limit;
489}
490
491struct wbt_wait_data {
492 struct rq_wb *rwb;
493 enum wbt_flags wb_acct;
494 unsigned long rw;
495};
496
497static bool wbt_inflight_cb(struct rq_wait *rqw, void *private_data)
498{
499 struct wbt_wait_data *data = private_data;
500 return rq_wait_inc_below(rqw, get_limit(data->rwb, data->rw));
501}
502
503static void wbt_cleanup_cb(struct rq_wait *rqw, void *private_data)
504{
505 struct wbt_wait_data *data = private_data;
506 wbt_rqw_done(data->rwb, rqw, data->wb_acct);
507}
508
509/*
510 * Block if we will exceed our limit, or if we are currently waiting for
511 * the timer to kick off queuing again.
512 */
513static void __wbt_wait(struct rq_wb *rwb, enum wbt_flags wb_acct,
514 unsigned long rw)
515{
516 struct rq_wait *rqw = get_rq_wait(rwb, wb_acct);
517 struct wbt_wait_data data = {
518 .rwb = rwb,
519 .wb_acct = wb_acct,
520 .rw = rw,
521 };
522
523 rq_qos_wait(rqw, &data, wbt_inflight_cb, wbt_cleanup_cb);
524}
525
526static inline bool wbt_should_throttle(struct rq_wb *rwb, struct bio *bio)
527{
528 switch (bio_op(bio)) {
529 case REQ_OP_WRITE:
530 /*
531 * Don't throttle WRITE_ODIRECT
532 */
533 if ((bio->bi_opf & (REQ_SYNC | REQ_IDLE)) ==
534 (REQ_SYNC | REQ_IDLE))
535 return false;
536 /* fallthrough */
537 case REQ_OP_DISCARD:
538 return true;
539 default:
540 return false;
541 }
542}
543
544static enum wbt_flags bio_to_wbt_flags(struct rq_wb *rwb, struct bio *bio)
545{
546 enum wbt_flags flags = 0;
547
548 if (!rwb_enabled(rwb))
549 return 0;
550
551 if (bio_op(bio) == REQ_OP_READ) {
552 flags = WBT_READ;
553 } else if (wbt_should_throttle(rwb, bio)) {
554 if (current_is_kswapd())
555 flags |= WBT_KSWAPD;
556 if (bio_op(bio) == REQ_OP_DISCARD)
557 flags |= WBT_DISCARD;
558 flags |= WBT_TRACKED;
559 }
560 return flags;
561}
562
563static void wbt_cleanup(struct rq_qos *rqos, struct bio *bio)
564{
565 struct rq_wb *rwb = RQWB(rqos);
566 enum wbt_flags flags = bio_to_wbt_flags(rwb, bio);
567 __wbt_done(rqos, flags);
568}
569
570/*
571 * Returns true if the IO request should be accounted, false if not.
572 * May sleep, if we have exceeded the writeback limits. Caller can pass
573 * in an irq held spinlock, if it holds one when calling this function.
574 * If we do sleep, we'll release and re-grab it.
575 */
576static void wbt_wait(struct rq_qos *rqos, struct bio *bio)
577{
578 struct rq_wb *rwb = RQWB(rqos);
579 enum wbt_flags flags;
580
581 flags = bio_to_wbt_flags(rwb, bio);
582 if (!(flags & WBT_TRACKED)) {
583 if (flags & WBT_READ)
584 wb_timestamp(rwb, &rwb->last_issue);
585 return;
586 }
587
588 __wbt_wait(rwb, flags, bio->bi_opf);
589
590 if (!blk_stat_is_active(rwb->cb))
591 rwb_arm_timer(rwb);
592}
593
594static void wbt_track(struct rq_qos *rqos, struct request *rq, struct bio *bio)
595{
596 struct rq_wb *rwb = RQWB(rqos);
597 rq->wbt_flags |= bio_to_wbt_flags(rwb, bio);
598}
599
600static void wbt_issue(struct rq_qos *rqos, struct request *rq)
601{
602 struct rq_wb *rwb = RQWB(rqos);
603
604 if (!rwb_enabled(rwb))
605 return;
606
607 /*
608 * Track sync issue, in case it takes a long time to complete. Allows us
609 * to react quicker, if a sync IO takes a long time to complete. Note
610 * that this is just a hint. The request can go away when it completes,
611 * so it's important we never dereference it. We only use the address to
612 * compare with, which is why we store the sync_issue time locally.
613 */
614 if (wbt_is_read(rq) && !rwb->sync_issue) {
615 rwb->sync_cookie = rq;
616 rwb->sync_issue = rq->io_start_time_ns;
617 }
618}
619
620static void wbt_requeue(struct rq_qos *rqos, struct request *rq)
621{
622 struct rq_wb *rwb = RQWB(rqos);
623 if (!rwb_enabled(rwb))
624 return;
625 if (rq == rwb->sync_cookie) {
626 rwb->sync_issue = 0;
627 rwb->sync_cookie = NULL;
628 }
629}
630
631void wbt_set_queue_depth(struct request_queue *q, unsigned int depth)
632{
633 struct rq_qos *rqos = wbt_rq_qos(q);
634 if (rqos) {
635 RQWB(rqos)->rq_depth.queue_depth = depth;
636 __wbt_update_limits(RQWB(rqos));
637 }
638}
639
640void wbt_set_write_cache(struct request_queue *q, bool write_cache_on)
641{
642 struct rq_qos *rqos = wbt_rq_qos(q);
643 if (rqos)
644 RQWB(rqos)->wc = write_cache_on;
645}
646
647/*
648 * Enable wbt if defaults are configured that way
649 */
650void wbt_enable_default(struct request_queue *q)
651{
652 struct rq_qos *rqos = wbt_rq_qos(q);
653 /* Throttling already enabled? */
654 if (rqos)
655 return;
656
657 /* Queue not registered? Maybe shutting down... */
658 if (!test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags))
659 return;
660
661 if (queue_is_mq(q) && IS_ENABLED(CONFIG_BLK_WBT_MQ))
662 wbt_init(q);
663}
664EXPORT_SYMBOL_GPL(wbt_enable_default);
665
666u64 wbt_default_latency_nsec(struct request_queue *q)
667{
668 /*
669 * We default to 2msec for non-rotational storage, and 75msec
670 * for rotational storage.
671 */
672 if (blk_queue_nonrot(q))
673 return 2000000ULL;
674 else
675 return 75000000ULL;
676}
677
678static int wbt_data_dir(const struct request *rq)
679{
680 const int op = req_op(rq);
681
682 if (op == REQ_OP_READ)
683 return READ;
684 else if (op_is_write(op))
685 return WRITE;
686
687 /* don't account */
688 return -1;
689}
690
691static void wbt_exit(struct rq_qos *rqos)
692{
693 struct rq_wb *rwb = RQWB(rqos);
694 struct request_queue *q = rqos->q;
695
696 blk_stat_remove_callback(q, rwb->cb);
697 blk_stat_free_callback(rwb->cb);
698 kfree(rwb);
699}
700
701/*
702 * Disable wbt, if enabled by default.
703 */
704void wbt_disable_default(struct request_queue *q)
705{
706 struct rq_qos *rqos = wbt_rq_qos(q);
707 struct rq_wb *rwb;
708 if (!rqos)
709 return;
710 rwb = RQWB(rqos);
711 if (rwb->enable_state == WBT_STATE_ON_DEFAULT) {
712 blk_stat_deactivate(rwb->cb);
713 rwb->wb_normal = 0;
714 }
715}
716EXPORT_SYMBOL_GPL(wbt_disable_default);
717
718#ifdef CONFIG_BLK_DEBUG_FS
719static int wbt_curr_win_nsec_show(void *data, struct seq_file *m)
720{
721 struct rq_qos *rqos = data;
722 struct rq_wb *rwb = RQWB(rqos);
723
724 seq_printf(m, "%llu\n", rwb->cur_win_nsec);
725 return 0;
726}
727
728static int wbt_enabled_show(void *data, struct seq_file *m)
729{
730 struct rq_qos *rqos = data;
731 struct rq_wb *rwb = RQWB(rqos);
732
733 seq_printf(m, "%d\n", rwb->enable_state);
734 return 0;
735}
736
737static int wbt_id_show(void *data, struct seq_file *m)
738{
739 struct rq_qos *rqos = data;
740
741 seq_printf(m, "%u\n", rqos->id);
742 return 0;
743}
744
745static int wbt_inflight_show(void *data, struct seq_file *m)
746{
747 struct rq_qos *rqos = data;
748 struct rq_wb *rwb = RQWB(rqos);
749 int i;
750
751 for (i = 0; i < WBT_NUM_RWQ; i++)
752 seq_printf(m, "%d: inflight %d\n", i,
753 atomic_read(&rwb->rq_wait[i].inflight));
754 return 0;
755}
756
757static int wbt_min_lat_nsec_show(void *data, struct seq_file *m)
758{
759 struct rq_qos *rqos = data;
760 struct rq_wb *rwb = RQWB(rqos);
761
762 seq_printf(m, "%lu\n", rwb->min_lat_nsec);
763 return 0;
764}
765
766static int wbt_unknown_cnt_show(void *data, struct seq_file *m)
767{
768 struct rq_qos *rqos = data;
769 struct rq_wb *rwb = RQWB(rqos);
770
771 seq_printf(m, "%u\n", rwb->unknown_cnt);
772 return 0;
773}
774
775static int wbt_normal_show(void *data, struct seq_file *m)
776{
777 struct rq_qos *rqos = data;
778 struct rq_wb *rwb = RQWB(rqos);
779
780 seq_printf(m, "%u\n", rwb->wb_normal);
781 return 0;
782}
783
784static int wbt_background_show(void *data, struct seq_file *m)
785{
786 struct rq_qos *rqos = data;
787 struct rq_wb *rwb = RQWB(rqos);
788
789 seq_printf(m, "%u\n", rwb->wb_background);
790 return 0;
791}
792
793static const struct blk_mq_debugfs_attr wbt_debugfs_attrs[] = {
794 {"curr_win_nsec", 0400, wbt_curr_win_nsec_show},
795 {"enabled", 0400, wbt_enabled_show},
796 {"id", 0400, wbt_id_show},
797 {"inflight", 0400, wbt_inflight_show},
798 {"min_lat_nsec", 0400, wbt_min_lat_nsec_show},
799 {"unknown_cnt", 0400, wbt_unknown_cnt_show},
800 {"wb_normal", 0400, wbt_normal_show},
801 {"wb_background", 0400, wbt_background_show},
802 {},
803};
804#endif
805
806static struct rq_qos_ops wbt_rqos_ops = {
807 .throttle = wbt_wait,
808 .issue = wbt_issue,
809 .track = wbt_track,
810 .requeue = wbt_requeue,
811 .done = wbt_done,
812 .cleanup = wbt_cleanup,
813 .exit = wbt_exit,
814#ifdef CONFIG_BLK_DEBUG_FS
815 .debugfs_attrs = wbt_debugfs_attrs,
816#endif
817};
818
819int wbt_init(struct request_queue *q)
820{
821 struct rq_wb *rwb;
822 int i;
823
824 rwb = kzalloc(sizeof(*rwb), GFP_KERNEL);
825 if (!rwb)
826 return -ENOMEM;
827
828 rwb->cb = blk_stat_alloc_callback(wb_timer_fn, wbt_data_dir, 2, rwb);
829 if (!rwb->cb) {
830 kfree(rwb);
831 return -ENOMEM;
832 }
833
834 for (i = 0; i < WBT_NUM_RWQ; i++)
835 rq_wait_init(&rwb->rq_wait[i]);
836
837 rwb->rqos.id = RQ_QOS_WBT;
838 rwb->rqos.ops = &wbt_rqos_ops;
839 rwb->rqos.q = q;
840 rwb->last_comp = rwb->last_issue = jiffies;
841 rwb->win_nsec = RWB_WINDOW_NSEC;
842 rwb->enable_state = WBT_STATE_ON_DEFAULT;
843 rwb->wc = 1;
844 rwb->rq_depth.default_depth = RWB_DEF_DEPTH;
845 __wbt_update_limits(rwb);
846
847 /*
848 * Assign rwb and add the stats callback.
849 */
850 rq_qos_add(q, &rwb->rqos);
851 blk_stat_add_callback(q, rwb->cb);
852
853 rwb->min_lat_nsec = wbt_default_latency_nsec(q);
854
855 wbt_set_queue_depth(q, blk_queue_depth(q));
856 wbt_set_write_cache(q, test_bit(QUEUE_FLAG_WC, &q->queue_flags));
857
858 return 0;
859}
860