1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * buffered writeback throttling. loosely based on CoDel. We can't drop
  4 * packets for IO scheduling, so the logic is something like this:
  5 *
  6 * - Monitor latencies in a defined window of time.
  7 * - If the minimum latency in the above window exceeds some target, increment
  8 *   scaling step and scale down queue depth by a factor of 2x. The monitoring
  9 *   window is then shrunk to 100 / sqrt(scaling step + 1).
 10 * - For any window where we don't have solid data on what the latencies
 11 *   look like, retain status quo.
 12 * - If latencies look good, decrement scaling step.
 13 * - If we're only doing writes, allow the scaling step to go negative. This
 14 *   will temporarily boost write performance, snapping back to a stable
 15 *   scaling step of 0 if reads show up or the heavy writers finish. Unlike
 16 *   positive scaling steps where we shrink the monitoring window, a negative
 17 *   scaling step retains the default step==0 window size.
 18 *
 19 * Copyright (C) 2016 Jens Axboe
 20 *
 21 */
 22#include <linux/kernel.h>
 23#include <linux/blk_types.h>
 24#include <linux/slab.h>
 25#include <linux/backing-dev.h>
 26#include <linux/swap.h>
 27
 28#include "blk-wbt.h"
 29#include "blk-rq-qos.h"
 30#include "elevator.h"
 31
 32#define CREATE_TRACE_POINTS
 33#include <trace/events/wbt.h>
 34
 35static inline void wbt_clear_state(struct request *rq)
 36{
 37	rq->wbt_flags = 0;
 38}
 39
 40static inline enum wbt_flags wbt_flags(struct request *rq)
 41{
 42	return rq->wbt_flags;
 43}
 44
 45static inline bool wbt_is_tracked(struct request *rq)
 46{
 47	return rq->wbt_flags & WBT_TRACKED;
 48}
 49
 50static inline bool wbt_is_read(struct request *rq)
 51{
 52	return rq->wbt_flags & WBT_READ;
 53}
 54
 55enum {
 56	/*
 57	 * Default setting, we'll scale up (to 75% of QD max) or down (min 1)
 58	 * from here depending on device stats
 59	 */
 60	RWB_DEF_DEPTH	= 16,
 61
 62	/*
 63	 * 100msec window
 64	 */
 65	RWB_WINDOW_NSEC		= 100 * 1000 * 1000ULL,
 66
 67	/*
 68	 * Disregard stats, if we don't meet this minimum
 69	 */
 70	RWB_MIN_WRITE_SAMPLES	= 3,
 71
 72	/*
 73	 * If we have this number of consecutive windows with not enough
 74	 * information to scale up or down, scale up.
 75	 */
 76	RWB_UNKNOWN_BUMP	= 5,
 77};
 78
 79static inline bool rwb_enabled(struct rq_wb *rwb)
 80{
 81	return rwb && rwb->enable_state != WBT_STATE_OFF_DEFAULT &&
 82		      rwb->wb_normal != 0;
 83}
 84
 85static void wb_timestamp(struct rq_wb *rwb, unsigned long *var)
 86{
 87	if (rwb_enabled(rwb)) {
 88		const unsigned long cur = jiffies;
 89
 90		if (cur != *var)
 91			*var = cur;
 92	}
 93}
 94
 95/*
 96 * If a task was rate throttled in balance_dirty_pages() within the last
 97 * second or so, use that to indicate a higher cleaning rate.
 98 */
 99static bool wb_recent_wait(struct rq_wb *rwb)
100{
101	struct bdi_writeback *wb = &rwb->rqos.q->disk->bdi->wb;
102
103	return time_before(jiffies, wb->dirty_sleep + HZ);
104}
105
106static inline struct rq_wait *get_rq_wait(struct rq_wb *rwb,
107					  enum wbt_flags wb_acct)
108{
109	if (wb_acct & WBT_KSWAPD)
110		return &rwb->rq_wait[WBT_RWQ_KSWAPD];
111	else if (wb_acct & WBT_DISCARD)
112		return &rwb->rq_wait[WBT_RWQ_DISCARD];
113
114	return &rwb->rq_wait[WBT_RWQ_BG];
115}
116
117static void rwb_wake_all(struct rq_wb *rwb)
118{
119	int i;
120
121	for (i = 0; i < WBT_NUM_RWQ; i++) {
122		struct rq_wait *rqw = &rwb->rq_wait[i];
123
124		if (wq_has_sleeper(&rqw->wait))
125			wake_up_all(&rqw->wait);
126	}
127}
128
129static void wbt_rqw_done(struct rq_wb *rwb, struct rq_wait *rqw,
130			 enum wbt_flags wb_acct)
131{
132	int inflight, limit;
133
134	inflight = atomic_dec_return(&rqw->inflight);
135
136	/*
137	 * wbt got disabled with IO in flight. Wake up any potential
138	 * waiters, we don't have to do more than that.
139	 */
140	if (unlikely(!rwb_enabled(rwb))) {
141		rwb_wake_all(rwb);
142		return;
143	}
144
145	/*
146	 * For discards, our limit is always the background. For writes, if
147	 * the device does write back caching, drop further down before we
148	 * wake people up.
149	 */
150	if (wb_acct & WBT_DISCARD)
151		limit = rwb->wb_background;
152	else if (rwb->wc && !wb_recent_wait(rwb))
153		limit = 0;
154	else
155		limit = rwb->wb_normal;
156
157	/*
158	 * Don't wake anyone up if we are above the normal limit.
159	 */
160	if (inflight && inflight >= limit)
161		return;
162
163	if (wq_has_sleeper(&rqw->wait)) {
164		int diff = limit - inflight;
165
166		if (!inflight || diff >= rwb->wb_background / 2)
167			wake_up_all(&rqw->wait);
168	}
169}
170
171static void __wbt_done(struct rq_qos *rqos, enum wbt_flags wb_acct)
172{
173	struct rq_wb *rwb = RQWB(rqos);
174	struct rq_wait *rqw;
175
176	if (!(wb_acct & WBT_TRACKED))
177		return;
178
179	rqw = get_rq_wait(rwb, wb_acct);
180	wbt_rqw_done(rwb, rqw, wb_acct);
181}
182
183/*
184 * Called on completion of a request. Note that it's also called when
185 * a request is merged, when the request gets freed.
186 */
187static void wbt_done(struct rq_qos *rqos, struct request *rq)
188{
189	struct rq_wb *rwb = RQWB(rqos);
190
191	if (!wbt_is_tracked(rq)) {
192		if (rwb->sync_cookie == rq) {
193			rwb->sync_issue = 0;
194			rwb->sync_cookie = NULL;
195		}
196
197		if (wbt_is_read(rq))
198			wb_timestamp(rwb, &rwb->last_comp);
199	} else {
200		WARN_ON_ONCE(rq == rwb->sync_cookie);
201		__wbt_done(rqos, wbt_flags(rq));
202	}
203	wbt_clear_state(rq);
204}
205
206static inline bool stat_sample_valid(struct blk_rq_stat *stat)
207{
208	/*
209	 * We need at least one read sample, and a minimum of
210	 * RWB_MIN_WRITE_SAMPLES. We require some write samples to know
211	 * that it's writes impacting us, and not just some sole read on
212	 * a device that is in a lower power state.
213	 */
214	return (stat[READ].nr_samples >= 1 &&
215		stat[WRITE].nr_samples >= RWB_MIN_WRITE_SAMPLES);
216}
217
218static u64 rwb_sync_issue_lat(struct rq_wb *rwb)
219{
220	u64 now, issue = READ_ONCE(rwb->sync_issue);
221
222	if (!issue || !rwb->sync_cookie)
223		return 0;
224
225	now = ktime_to_ns(ktime_get());
226	return now - issue;
227}
228
229enum {
230	LAT_OK = 1,
231	LAT_UNKNOWN,
232	LAT_UNKNOWN_WRITES,
233	LAT_EXCEEDED,
234};
235
236static int latency_exceeded(struct rq_wb *rwb, struct blk_rq_stat *stat)
237{
238	struct backing_dev_info *bdi = rwb->rqos.q->disk->bdi;
239	struct rq_depth *rqd = &rwb->rq_depth;
240	u64 thislat;
241
242	/*
243	 * If our stored sync issue exceeds the window size, or it
244	 * exceeds our min target AND we haven't logged any entries,
245	 * flag the latency as exceeded. wbt works off completion latencies,
246	 * but for a flooded device, a single sync IO can take a long time
247	 * to complete after being issued. If this time exceeds our
248	 * monitoring window AND we didn't see any other completions in that
249	 * window, then count that sync IO as a violation of the latency.
250	 */
251	thislat = rwb_sync_issue_lat(rwb);
252	if (thislat > rwb->cur_win_nsec ||
253	    (thislat > rwb->min_lat_nsec && !stat[READ].nr_samples)) {
254		trace_wbt_lat(bdi, thislat);
255		return LAT_EXCEEDED;
256	}
257
258	/*
259	 * No read/write mix, if stat isn't valid
260	 */
261	if (!stat_sample_valid(stat)) {
262		/*
263		 * If we had writes in this stat window and the window is
264		 * current, we're only doing writes. If a task recently
265		 * waited or still has writes in flights, consider us doing
266		 * just writes as well.
267		 */
268		if (stat[WRITE].nr_samples || wb_recent_wait(rwb) ||
269		    wbt_inflight(rwb))
270			return LAT_UNKNOWN_WRITES;
271		return LAT_UNKNOWN;
272	}
273
274	/*
275	 * If the 'min' latency exceeds our target, step down.
276	 */
277	if (stat[READ].min > rwb->min_lat_nsec) {
278		trace_wbt_lat(bdi, stat[READ].min);
279		trace_wbt_stat(bdi, stat);
280		return LAT_EXCEEDED;
281	}
282
283	if (rqd->scale_step)
284		trace_wbt_stat(bdi, stat);
285
286	return LAT_OK;
287}
288
289static void rwb_trace_step(struct rq_wb *rwb, const char *msg)
290{
291	struct backing_dev_info *bdi = rwb->rqos.q->disk->bdi;
292	struct rq_depth *rqd = &rwb->rq_depth;
293
294	trace_wbt_step(bdi, msg, rqd->scale_step, rwb->cur_win_nsec,
295			rwb->wb_background, rwb->wb_normal, rqd->max_depth);
296}
297
298static void calc_wb_limits(struct rq_wb *rwb)
299{
300	if (rwb->min_lat_nsec == 0) {
301		rwb->wb_normal = rwb->wb_background = 0;
302	} else if (rwb->rq_depth.max_depth <= 2) {
303		rwb->wb_normal = rwb->rq_depth.max_depth;
304		rwb->wb_background = 1;
305	} else {
306		rwb->wb_normal = (rwb->rq_depth.max_depth + 1) / 2;
307		rwb->wb_background = (rwb->rq_depth.max_depth + 3) / 4;
308	}
309}
310
311static void scale_up(struct rq_wb *rwb)
312{
313	if (!rq_depth_scale_up(&rwb->rq_depth))
314		return;
315	calc_wb_limits(rwb);
316	rwb->unknown_cnt = 0;
317	rwb_wake_all(rwb);
318	rwb_trace_step(rwb, tracepoint_string("scale up"));
319}
320
321static void scale_down(struct rq_wb *rwb, bool hard_throttle)
322{
323	if (!rq_depth_scale_down(&rwb->rq_depth, hard_throttle))
324		return;
325	calc_wb_limits(rwb);
326	rwb->unknown_cnt = 0;
327	rwb_trace_step(rwb, tracepoint_string("scale down"));
328}
329
330static void rwb_arm_timer(struct rq_wb *rwb)
331{
332	struct rq_depth *rqd = &rwb->rq_depth;
333
334	if (rqd->scale_step > 0) {
335		/*
336		 * We should speed this up, using some variant of a fast
337		 * integer inverse square root calculation. Since we only do
338		 * this for every window expiration, it's not a huge deal,
339		 * though.
340		 */
341		rwb->cur_win_nsec = div_u64(rwb->win_nsec << 4,
342					int_sqrt((rqd->scale_step + 1) << 8));
343	} else {
344		/*
345		 * For step < 0, we don't want to increase/decrease the
346		 * window size.
347		 */
348		rwb->cur_win_nsec = rwb->win_nsec;
349	}
350
351	blk_stat_activate_nsecs(rwb->cb, rwb->cur_win_nsec);
352}
353
354static void wb_timer_fn(struct blk_stat_callback *cb)
355{
356	struct rq_wb *rwb = cb->data;
357	struct rq_depth *rqd = &rwb->rq_depth;
358	unsigned int inflight = wbt_inflight(rwb);
359	int status;
360
361	if (!rwb->rqos.q->disk)
362		return;
363
364	status = latency_exceeded(rwb, cb->stat);
365
366	trace_wbt_timer(rwb->rqos.q->disk->bdi, status, rqd->scale_step,
367			inflight);
368
369	/*
370	 * If we exceeded the latency target, step down. If we did not,
371	 * step one level up. If we don't know enough to say either exceeded
372	 * or ok, then don't do anything.
373	 */
374	switch (status) {
375	case LAT_EXCEEDED:
376		scale_down(rwb, true);
377		break;
378	case LAT_OK:
379		scale_up(rwb);
380		break;
381	case LAT_UNKNOWN_WRITES:
382		/*
383		 * We started a the center step, but don't have a valid
384		 * read/write sample, but we do have writes going on.
385		 * Allow step to go negative, to increase write perf.
386		 */
387		scale_up(rwb);
388		break;
389	case LAT_UNKNOWN:
390		if (++rwb->unknown_cnt < RWB_UNKNOWN_BUMP)
391			break;
392		/*
393		 * We get here when previously scaled reduced depth, and we
394		 * currently don't have a valid read/write sample. For that
395		 * case, slowly return to center state (step == 0).
396		 */
397		if (rqd->scale_step > 0)
398			scale_up(rwb);
399		else if (rqd->scale_step < 0)
400			scale_down(rwb, false);
401		break;
402	default:
403		break;
404	}
405
406	/*
407	 * Re-arm timer, if we have IO in flight
408	 */
409	if (rqd->scale_step || inflight)
410		rwb_arm_timer(rwb);
411}
412
413static void wbt_update_limits(struct rq_wb *rwb)
414{
415	struct rq_depth *rqd = &rwb->rq_depth;
416
417	rqd->scale_step = 0;
418	rqd->scaled_max = false;
419
420	rq_depth_calc_max_depth(rqd);
421	calc_wb_limits(rwb);
422
423	rwb_wake_all(rwb);
424}
425
426bool wbt_disabled(struct request_queue *q)
427{
428	struct rq_qos *rqos = wbt_rq_qos(q);
429
430	return !rqos || RQWB(rqos)->enable_state == WBT_STATE_OFF_DEFAULT ||
431	       RQWB(rqos)->enable_state == WBT_STATE_OFF_MANUAL;
432}
433
434u64 wbt_get_min_lat(struct request_queue *q)
435{
436	struct rq_qos *rqos = wbt_rq_qos(q);
437	if (!rqos)
438		return 0;
439	return RQWB(rqos)->min_lat_nsec;
440}
441
442void wbt_set_min_lat(struct request_queue *q, u64 val)
443{
444	struct rq_qos *rqos = wbt_rq_qos(q);
445	if (!rqos)
446		return;
447
448	RQWB(rqos)->min_lat_nsec = val;
449	if (val)
450		RQWB(rqos)->enable_state = WBT_STATE_ON_MANUAL;
451	else
452		RQWB(rqos)->enable_state = WBT_STATE_OFF_MANUAL;
453
454	wbt_update_limits(RQWB(rqos));
455}
456
457
458static bool close_io(struct rq_wb *rwb)
459{
460	const unsigned long now = jiffies;
461
462	return time_before(now, rwb->last_issue + HZ / 10) ||
463		time_before(now, rwb->last_comp + HZ / 10);
464}
465
466#define REQ_HIPRIO	(REQ_SYNC | REQ_META | REQ_PRIO)
467
468static inline unsigned int get_limit(struct rq_wb *rwb, blk_opf_t opf)
469{
470	unsigned int limit;
471
472	/*
473	 * If we got disabled, just return UINT_MAX. This ensures that
474	 * we'll properly inc a new IO, and dec+wakeup at the end.
475	 */
476	if (!rwb_enabled(rwb))
477		return UINT_MAX;
478
479	if ((opf & REQ_OP_MASK) == REQ_OP_DISCARD)
480		return rwb->wb_background;
481
482	/*
483	 * At this point we know it's a buffered write. If this is
484	 * kswapd trying to free memory, or REQ_SYNC is set, then
485	 * it's WB_SYNC_ALL writeback, and we'll use the max limit for
486	 * that. If the write is marked as a background write, then use
487	 * the idle limit, or go to normal if we haven't had competing
488	 * IO for a bit.
489	 */
490	if ((opf & REQ_HIPRIO) || wb_recent_wait(rwb) || current_is_kswapd())
491		limit = rwb->rq_depth.max_depth;
492	else if ((opf & REQ_BACKGROUND) || close_io(rwb)) {
493		/*
494		 * If less than 100ms since we completed unrelated IO,
495		 * limit us to half the depth for background writeback.
496		 */
497		limit = rwb->wb_background;
498	} else
499		limit = rwb->wb_normal;
500
501	return limit;
502}
503
504struct wbt_wait_data {
505	struct rq_wb *rwb;
506	enum wbt_flags wb_acct;
507	blk_opf_t opf;
508};
509
510static bool wbt_inflight_cb(struct rq_wait *rqw, void *private_data)
511{
512	struct wbt_wait_data *data = private_data;
513	return rq_wait_inc_below(rqw, get_limit(data->rwb, data->opf));
514}
515
516static void wbt_cleanup_cb(struct rq_wait *rqw, void *private_data)
517{
518	struct wbt_wait_data *data = private_data;
519	wbt_rqw_done(data->rwb, rqw, data->wb_acct);
520}
521
522/*
523 * Block if we will exceed our limit, or if we are currently waiting for
524 * the timer to kick off queuing again.
525 */
526static void __wbt_wait(struct rq_wb *rwb, enum wbt_flags wb_acct,
527		       blk_opf_t opf)
528{
529	struct rq_wait *rqw = get_rq_wait(rwb, wb_acct);
530	struct wbt_wait_data data = {
531		.rwb = rwb,
532		.wb_acct = wb_acct,
533		.opf = opf,
534	};
535
536	rq_qos_wait(rqw, &data, wbt_inflight_cb, wbt_cleanup_cb);
537}
538
539static inline bool wbt_should_throttle(struct bio *bio)
540{
541	switch (bio_op(bio)) {
542	case REQ_OP_WRITE:
543		/*
544		 * Don't throttle WRITE_ODIRECT
545		 */
546		if ((bio->bi_opf & (REQ_SYNC | REQ_IDLE)) ==
547		    (REQ_SYNC | REQ_IDLE))
548			return false;
549		fallthrough;
550	case REQ_OP_DISCARD:
551		return true;
552	default:
553		return false;
554	}
555}
556
557static enum wbt_flags bio_to_wbt_flags(struct rq_wb *rwb, struct bio *bio)
558{
559	enum wbt_flags flags = 0;
560
561	if (!rwb_enabled(rwb))
562		return 0;
563
564	if (bio_op(bio) == REQ_OP_READ) {
565		flags = WBT_READ;
566	} else if (wbt_should_throttle(bio)) {
567		if (current_is_kswapd())
568			flags |= WBT_KSWAPD;
569		if (bio_op(bio) == REQ_OP_DISCARD)
570			flags |= WBT_DISCARD;
571		flags |= WBT_TRACKED;
572	}
573	return flags;
574}
575
576static void wbt_cleanup(struct rq_qos *rqos, struct bio *bio)
577{
578	struct rq_wb *rwb = RQWB(rqos);
579	enum wbt_flags flags = bio_to_wbt_flags(rwb, bio);
580	__wbt_done(rqos, flags);
581}
582
583/*
 
584 * May sleep, if we have exceeded the writeback limits. Caller can pass
585 * in an irq held spinlock, if it holds one when calling this function.
586 * If we do sleep, we'll release and re-grab it.
587 */
588static void wbt_wait(struct rq_qos *rqos, struct bio *bio)
589{
590	struct rq_wb *rwb = RQWB(rqos);
591	enum wbt_flags flags;
592
593	flags = bio_to_wbt_flags(rwb, bio);
594	if (!(flags & WBT_TRACKED)) {
595		if (flags & WBT_READ)
596			wb_timestamp(rwb, &rwb->last_issue);
597		return;
598	}
599
600	__wbt_wait(rwb, flags, bio->bi_opf);
601
602	if (!blk_stat_is_active(rwb->cb))
603		rwb_arm_timer(rwb);
604}
605
606static void wbt_track(struct rq_qos *rqos, struct request *rq, struct bio *bio)
607{
608	struct rq_wb *rwb = RQWB(rqos);
609	rq->wbt_flags |= bio_to_wbt_flags(rwb, bio);
610}
611
612static void wbt_issue(struct rq_qos *rqos, struct request *rq)
613{
614	struct rq_wb *rwb = RQWB(rqos);
615
616	if (!rwb_enabled(rwb))
617		return;
618
619	/*
620	 * Track sync issue, in case it takes a long time to complete. Allows us
621	 * to react quicker, if a sync IO takes a long time to complete. Note
622	 * that this is just a hint. The request can go away when it completes,
623	 * so it's important we never dereference it. We only use the address to
624	 * compare with, which is why we store the sync_issue time locally.
625	 */
626	if (wbt_is_read(rq) && !rwb->sync_issue) {
627		rwb->sync_cookie = rq;
628		rwb->sync_issue = rq->io_start_time_ns;
629	}
630}
631
632static void wbt_requeue(struct rq_qos *rqos, struct request *rq)
633{
634	struct rq_wb *rwb = RQWB(rqos);
635	if (!rwb_enabled(rwb))
636		return;
637	if (rq == rwb->sync_cookie) {
638		rwb->sync_issue = 0;
639		rwb->sync_cookie = NULL;
640	}
641}
642
643void wbt_set_write_cache(struct request_queue *q, bool write_cache_on)
644{
645	struct rq_qos *rqos = wbt_rq_qos(q);
646	if (rqos)
647		RQWB(rqos)->wc = write_cache_on;
648}
649
650/*
651 * Enable wbt if defaults are configured that way
652 */
653void wbt_enable_default(struct request_queue *q)
654{
655	struct rq_qos *rqos;
656	bool disable_flag = q->elevator &&
657		    test_bit(ELEVATOR_FLAG_DISABLE_WBT, &q->elevator->flags);
658
659	/* Throttling already enabled? */
660	rqos = wbt_rq_qos(q);
661	if (rqos) {
662		if (!disable_flag &&
663		    RQWB(rqos)->enable_state == WBT_STATE_OFF_DEFAULT)
664			RQWB(rqos)->enable_state = WBT_STATE_ON_DEFAULT;
665		return;
666	}
667
668	/* Queue not registered? Maybe shutting down... */
669	if (!blk_queue_registered(q))
670		return;
671
672	if (queue_is_mq(q) && !disable_flag)
673		wbt_init(q);
674}
675EXPORT_SYMBOL_GPL(wbt_enable_default);
676
677u64 wbt_default_latency_nsec(struct request_queue *q)
678{
679	/*
680	 * We default to 2msec for non-rotational storage, and 75msec
681	 * for rotational storage.
682	 */
683	if (blk_queue_nonrot(q))
684		return 2000000ULL;
685	else
686		return 75000000ULL;
687}
688
689static int wbt_data_dir(const struct request *rq)
690{
691	const enum req_op op = req_op(rq);
692
693	if (op == REQ_OP_READ)
694		return READ;
695	else if (op_is_write(op))
696		return WRITE;
697
698	/* don't account */
699	return -1;
700}
701
702static void wbt_queue_depth_changed(struct rq_qos *rqos)
703{
704	RQWB(rqos)->rq_depth.queue_depth = blk_queue_depth(rqos->q);
705	wbt_update_limits(RQWB(rqos));
706}
707
708static void wbt_exit(struct rq_qos *rqos)
709{
710	struct rq_wb *rwb = RQWB(rqos);
711	struct request_queue *q = rqos->q;
712
713	blk_stat_remove_callback(q, rwb->cb);
714	blk_stat_free_callback(rwb->cb);
715	kfree(rwb);
716}
717
718/*
719 * Disable wbt, if enabled by default.
720 */
721void wbt_disable_default(struct request_queue *q)
722{
723	struct rq_qos *rqos = wbt_rq_qos(q);
724	struct rq_wb *rwb;
725	if (!rqos)
726		return;
727	rwb = RQWB(rqos);
728	if (rwb->enable_state == WBT_STATE_ON_DEFAULT) {
729		blk_stat_deactivate(rwb->cb);
730		rwb->enable_state = WBT_STATE_OFF_DEFAULT;
731	}
732}
733EXPORT_SYMBOL_GPL(wbt_disable_default);
734
735#ifdef CONFIG_BLK_DEBUG_FS
736static int wbt_curr_win_nsec_show(void *data, struct seq_file *m)
737{
738	struct rq_qos *rqos = data;
739	struct rq_wb *rwb = RQWB(rqos);
740
741	seq_printf(m, "%llu\n", rwb->cur_win_nsec);
742	return 0;
743}
744
745static int wbt_enabled_show(void *data, struct seq_file *m)
746{
747	struct rq_qos *rqos = data;
748	struct rq_wb *rwb = RQWB(rqos);
749
750	seq_printf(m, "%d\n", rwb->enable_state);
751	return 0;
752}
753
754static int wbt_id_show(void *data, struct seq_file *m)
755{
756	struct rq_qos *rqos = data;
757
758	seq_printf(m, "%u\n", rqos->id);
759	return 0;
760}
761
762static int wbt_inflight_show(void *data, struct seq_file *m)
763{
764	struct rq_qos *rqos = data;
765	struct rq_wb *rwb = RQWB(rqos);
766	int i;
767
768	for (i = 0; i < WBT_NUM_RWQ; i++)
769		seq_printf(m, "%d: inflight %d\n", i,
770			   atomic_read(&rwb->rq_wait[i].inflight));
771	return 0;
772}
773
774static int wbt_min_lat_nsec_show(void *data, struct seq_file *m)
775{
776	struct rq_qos *rqos = data;
777	struct rq_wb *rwb = RQWB(rqos);
778
779	seq_printf(m, "%lu\n", rwb->min_lat_nsec);
780	return 0;
781}
782
783static int wbt_unknown_cnt_show(void *data, struct seq_file *m)
784{
785	struct rq_qos *rqos = data;
786	struct rq_wb *rwb = RQWB(rqos);
787
788	seq_printf(m, "%u\n", rwb->unknown_cnt);
789	return 0;
790}
791
792static int wbt_normal_show(void *data, struct seq_file *m)
793{
794	struct rq_qos *rqos = data;
795	struct rq_wb *rwb = RQWB(rqos);
796
797	seq_printf(m, "%u\n", rwb->wb_normal);
798	return 0;
799}
800
801static int wbt_background_show(void *data, struct seq_file *m)
802{
803	struct rq_qos *rqos = data;
804	struct rq_wb *rwb = RQWB(rqos);
805
806	seq_printf(m, "%u\n", rwb->wb_background);
807	return 0;
808}
809
810static const struct blk_mq_debugfs_attr wbt_debugfs_attrs[] = {
811	{"curr_win_nsec", 0400, wbt_curr_win_nsec_show},
812	{"enabled", 0400, wbt_enabled_show},
813	{"id", 0400, wbt_id_show},
814	{"inflight", 0400, wbt_inflight_show},
815	{"min_lat_nsec", 0400, wbt_min_lat_nsec_show},
816	{"unknown_cnt", 0400, wbt_unknown_cnt_show},
817	{"wb_normal", 0400, wbt_normal_show},
818	{"wb_background", 0400, wbt_background_show},
819	{},
820};
821#endif
822
823static struct rq_qos_ops wbt_rqos_ops = {
824	.throttle = wbt_wait,
825	.issue = wbt_issue,
826	.track = wbt_track,
827	.requeue = wbt_requeue,
828	.done = wbt_done,
829	.cleanup = wbt_cleanup,
830	.queue_depth_changed = wbt_queue_depth_changed,
831	.exit = wbt_exit,
832#ifdef CONFIG_BLK_DEBUG_FS
833	.debugfs_attrs = wbt_debugfs_attrs,
834#endif
835};
836
837int wbt_init(struct request_queue *q)
838{
839	struct rq_wb *rwb;
840	int i;
841	int ret;
842
843	rwb = kzalloc(sizeof(*rwb), GFP_KERNEL);
844	if (!rwb)
845		return -ENOMEM;
846
847	rwb->cb = blk_stat_alloc_callback(wb_timer_fn, wbt_data_dir, 2, rwb);
848	if (!rwb->cb) {
849		kfree(rwb);
850		return -ENOMEM;
851	}
852
853	for (i = 0; i < WBT_NUM_RWQ; i++)
854		rq_wait_init(&rwb->rq_wait[i]);
855
856	rwb->rqos.id = RQ_QOS_WBT;
857	rwb->rqos.ops = &wbt_rqos_ops;
858	rwb->rqos.q = q;
859	rwb->last_comp = rwb->last_issue = jiffies;
860	rwb->win_nsec = RWB_WINDOW_NSEC;
861	rwb->enable_state = WBT_STATE_ON_DEFAULT;
862	rwb->wc = test_bit(QUEUE_FLAG_WC, &q->queue_flags);
863	rwb->rq_depth.default_depth = RWB_DEF_DEPTH;
864	rwb->min_lat_nsec = wbt_default_latency_nsec(q);
865
866	wbt_queue_depth_changed(&rwb->rqos);
867
868	/*
869	 * Assign rwb and add the stats callback.
870	 */
871	ret = rq_qos_add(q, &rwb->rqos);
872	if (ret)
873		goto err_free;
874
875	blk_stat_add_callback(q, rwb->cb);
876
877	return 0;
878
879err_free:
880	blk_stat_free_callback(rwb->cb);
881	kfree(rwb);
882	return ret;
883
 
884}