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2024-02-20 ea08eeccae9297f7aabd2ef7f0c2517ac4549acc 
 kernel/block/blk-iolatency.c
....@@ -1,3 +1,4 @@
1
+// SPDX-License-Identifier: GPL-2.0
12 /*
23  * Block rq-qos base io controller
34  *
....@@ -85,17 +86,22 @@
8586 struct blk_iolatency {
8687 	struct rq_qos rqos;
8788 	struct timer_list timer;
88
-	atomic_t enabled;
89
+
90
+	/*
91
+	 * ->enabled is the master enable switch gating the throttling logic and
92
+	 * inflight tracking. The number of cgroups which have iolat enabled is
93
+	 * tracked in ->enable_cnt, and ->enable is flipped on/off accordingly
94
+	 * from ->enable_work with the request_queue frozen. For details, See
95
+	 * blkiolatency_enable_work_fn().
96
+	 */
97
+	bool enabled;
98
+	atomic_t enable_cnt;
99
+	struct work_struct enable_work;
89100 };
90101 
91102 static inline struct blk_iolatency *BLKIOLATENCY(struct rq_qos *rqos)
92103 {
93104 	return container_of(rqos, struct blk_iolatency, rqos);
94
-}
95
-
96
-static inline bool blk_iolatency_enabled(struct blk_iolatency *blkiolat)
97
-{
98
-	return atomic_read(&blkiolat->enabled) > 0;
99105 }
100106 
101107 struct child_latency_info {
....@@ -117,9 +123,22 @@
117123 	atomic_t scale_cookie;
118124 };
119125 
126
+struct percentile_stats {
127
+	u64 total;
128
+	u64 missed;
129
+};
130
+
131
+struct latency_stat {
132
+	union {
133
+		struct percentile_stats ps;
134
+		struct blk_rq_stat rqs;
135
+	};
136
+};
137
+
120138 struct iolatency_grp {
121139 	struct blkg_policy_data pd;
122
-	struct blk_rq_stat __percpu *stats;
140
+	struct latency_stat __percpu *stats;
141
+	struct latency_stat cur_stat;
123142 	struct blk_iolatency *blkiolat;
124143 	struct rq_depth rq_depth;
125144 	struct rq_wait rq_wait;
....@@ -134,6 +153,7 @@
134153 	/* Our current number of IO's for the last summation. */
135154 	u64 nr_samples;
136155 
156
+	bool ssd;
137157 	struct child_latency_info child_lat;
138158 };
139159 
....@@ -174,29 +194,101 @@
174194 	return pd_to_blkg(&iolat->pd);
175195 }
176196 
177
-static inline bool iolatency_may_queue(struct iolatency_grp *iolat,
178
-				       wait_queue_entry_t *wait,
179
-				       bool first_block)
197
+static inline void latency_stat_init(struct iolatency_grp *iolat,
198
+				     struct latency_stat *stat)
180199 {
181
-	struct rq_wait *rqw = &iolat->rq_wait;
200
+	if (iolat->ssd) {
201
+		stat->ps.total = 0;
202
+		stat->ps.missed = 0;
203
+	} else
204
+		blk_rq_stat_init(&stat->rqs);
205
+}
182206 
183
-	if (first_block && waitqueue_active(&rqw->wait) &&
184
-	    rqw->wait.head.next != &wait->entry)
185
-		return false;
207
+static inline void latency_stat_sum(struct iolatency_grp *iolat,
208
+				    struct latency_stat *sum,
209
+				    struct latency_stat *stat)
210
+{
211
+	if (iolat->ssd) {
212
+		sum->ps.total += stat->ps.total;
213
+		sum->ps.missed += stat->ps.missed;
214
+	} else
215
+		blk_rq_stat_sum(&sum->rqs, &stat->rqs);
216
+}
217
+
218
+static inline void latency_stat_record_time(struct iolatency_grp *iolat,
219
+					    u64 req_time)
220
+{
221
+	struct latency_stat *stat = get_cpu_ptr(iolat->stats);
222
+	if (iolat->ssd) {
223
+		if (req_time >= iolat->min_lat_nsec)
224
+			stat->ps.missed++;
225
+		stat->ps.total++;
226
+	} else
227
+		blk_rq_stat_add(&stat->rqs, req_time);
228
+	put_cpu_ptr(stat);
229
+}
230
+
231
+static inline bool latency_sum_ok(struct iolatency_grp *iolat,
232
+				  struct latency_stat *stat)
233
+{
234
+	if (iolat->ssd) {
235
+		u64 thresh = div64_u64(stat->ps.total, 10);
236
+		thresh = max(thresh, 1ULL);
237
+		return stat->ps.missed < thresh;
238
+	}
239
+	return stat->rqs.mean <= iolat->min_lat_nsec;
240
+}
241
+
242
+static inline u64 latency_stat_samples(struct iolatency_grp *iolat,
243
+				       struct latency_stat *stat)
244
+{
245
+	if (iolat->ssd)
246
+		return stat->ps.total;
247
+	return stat->rqs.nr_samples;
248
+}
249
+
250
+static inline void iolat_update_total_lat_avg(struct iolatency_grp *iolat,
251
+					      struct latency_stat *stat)
252
+{
253
+	int exp_idx;
254
+
255
+	if (iolat->ssd)
256
+		return;
257
+
258
+	/*
259
+	 * calc_load() takes in a number stored in fixed point representation.
260
+	 * Because we are using this for IO time in ns, the values stored
261
+	 * are significantly larger than the FIXED_1 denominator (2048).
262
+	 * Therefore, rounding errors in the calculation are negligible and
263
+	 * can be ignored.
264
+	 */
265
+	exp_idx = min_t(int, BLKIOLATENCY_NR_EXP_FACTORS - 1,
266
+			div64_u64(iolat->cur_win_nsec,
267
+				  BLKIOLATENCY_EXP_BUCKET_SIZE));
268
+	iolat->lat_avg = calc_load(iolat->lat_avg,
269
+				   iolatency_exp_factors[exp_idx],
270
+				   stat->rqs.mean);
271
+}
272
+
273
+static void iolat_cleanup_cb(struct rq_wait *rqw, void *private_data)
274
+{
275
+	atomic_dec(&rqw->inflight);
276
+	wake_up(&rqw->wait);
277
+}
278
+
279
+static bool iolat_acquire_inflight(struct rq_wait *rqw, void *private_data)
280
+{
281
+	struct iolatency_grp *iolat = private_data;
186282 	return rq_wait_inc_below(rqw, iolat->rq_depth.max_depth);
187283 }
188284 
189285 static void __blkcg_iolatency_throttle(struct rq_qos *rqos,
190286 				       struct iolatency_grp *iolat,
191
-				       spinlock_t *lock, bool issue_as_root,
287
+				       bool issue_as_root,
192288 				       bool use_memdelay)
193
-	__releases(lock)
194
-	__acquires(lock)
195289 {
196290 	struct rq_wait *rqw = &iolat->rq_wait;
197291 	unsigned use_delay = atomic_read(&lat_to_blkg(iolat)->use_delay);
198
-	DEFINE_WAIT(wait);
199
-	bool first_block = true;
200292 
201293 	if (use_delay)
202294 		blkcg_schedule_throttle(rqos->q, use_memdelay);
....@@ -213,27 +305,7 @@
213305 		return;
214306 	}
215307 
216
-	if (iolatency_may_queue(iolat, &wait, first_block))
217
-		return;
218
-
219
-	do {
220
-		prepare_to_wait_exclusive(&rqw->wait, &wait,
221
-					  TASK_UNINTERRUPTIBLE);
222
-
223
-		if (iolatency_may_queue(iolat, &wait, first_block))
224
-			break;
225
-		first_block = false;
226
-
227
-		if (lock) {
228
-			spin_unlock_irq(lock);
229
-			io_schedule();
230
-			spin_lock_irq(lock);
231
-		} else {
232
-			io_schedule();
233
-		}
234
-	} while (1);
235
-
236
-	finish_wait(&rqw->wait, &wait);
308
+	rq_qos_wait(rqw, iolat, iolat_acquire_inflight, iolat_cleanup_cb);
237309 }
238310 
239311 #define SCALE_DOWN_FACTOR 2
....@@ -257,7 +329,7 @@
257329 				struct child_latency_info *lat_info,
258330 				bool up)
259331 {
260
-	unsigned long qd = blk_queue_depth(blkiolat->rqos.q);
332
+	unsigned long qd = blkiolat->rqos.q->nr_requests;
261333 	unsigned long scale = scale_amount(qd, up);
262334 	unsigned long old = atomic_read(&lat_info->scale_cookie);
263335 	unsigned long max_scale = qd << 1;
....@@ -297,10 +369,9 @@
297369  */
298370 static void scale_change(struct iolatency_grp *iolat, bool up)
299371 {
300
-	unsigned long qd = blk_queue_depth(iolat->blkiolat->rqos.q);
372
+	unsigned long qd = iolat->blkiolat->rqos.q->nr_requests;
301373 	unsigned long scale = scale_amount(qd, up);
302374 	unsigned long old = iolat->rq_depth.max_depth;
303
-	bool changed = false;
304375 
305376 	if (old > qd)
306377 		old = qd;
....@@ -310,15 +381,13 @@
310381 			return;
311382 
312383 		if (old < qd) {
313
-			changed = true;
314384 			old += scale;
315385 			old = min(old, qd);
316386 			iolat->rq_depth.max_depth = old;
317387 			wake_up_all(&iolat->rq_wait.wait);
318388 		}
319
-	} else if (old > 1) {
389
+	} else {
320390 		old >>= 1;
321
-		changed = true;
322391 		iolat->rq_depth.max_depth = max(old, 1UL);
323392 	}
324393 }
....@@ -371,7 +440,7 @@
371440 		 * scale down event.
372441 		 */
373442 		samples_thresh = lat_info->nr_samples * 5;
374
-		samples_thresh = div64_u64(samples_thresh, 100);
443
+		samples_thresh = max(1ULL, div64_u64(samples_thresh, 100));
375444 		if (iolat->nr_samples <= samples_thresh)
376445 			return;
377446 	}
....@@ -393,38 +462,15 @@
393462 	scale_change(iolat, direction > 0);
394463 }
395464 
396
-static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio,
397
-				     spinlock_t *lock)
465
+static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio)
398466 {
399467 	struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos);
400
-	struct blkcg *blkcg;
401
-	struct blkcg_gq *blkg;
402
-	struct request_queue *q = rqos->q;
468
+	struct blkcg_gq *blkg = bio->bi_blkg;
403469 	bool issue_as_root = bio_issue_as_root_blkg(bio);
404470 
405
-	if (!blk_iolatency_enabled(blkiolat))
471
+	if (!blkiolat->enabled)
406472 		return;
407473 
408
-	rcu_read_lock();
409
-	blkcg = bio_blkcg(bio);
410
-	bio_associate_blkcg(bio, &blkcg->css);
411
-	blkg = blkg_lookup(blkcg, q);
412
-	if (unlikely(!blkg)) {
413
-		if (!lock)
414
-			spin_lock_irq(q->queue_lock);
415
-		blkg = blkg_lookup_create(blkcg, q);
416
-		if (IS_ERR(blkg))
417
-			blkg = NULL;
418
-		if (!lock)
419
-			spin_unlock_irq(q->queue_lock);
420
-	}
421
-	if (!blkg)
422
-		goto out;
423
-
424
-	bio_issue_init(&bio->bi_issue, bio_sectors(bio));
425
-	bio_associate_blkg(bio, blkg);
426
-out:
427
-	rcu_read_unlock();
428474 	while (blkg && blkg->parent) {
429475 		struct iolatency_grp *iolat = blkg_to_lat(blkg);
430476 		if (!iolat) {
....@@ -433,7 +479,7 @@
433479 		}
434480 
435481 		check_scale_change(iolat);
436
-		__blkcg_iolatency_throttle(rqos, iolat, lock, issue_as_root,
482
+		__blkcg_iolatency_throttle(rqos, iolat, issue_as_root,
437483 				     (bio->bi_opf & REQ_SWAP) == REQ_SWAP);
438484 		blkg = blkg->parent;
439485 	}
....@@ -445,7 +491,6 @@
445491 				  struct bio_issue *issue, u64 now,
446492 				  bool issue_as_root)
447493 {
448
-	struct blk_rq_stat *rq_stat;
449494 	u64 start = bio_issue_time(issue);
450495 	u64 req_time;
451496 
....@@ -471,9 +516,7 @@
471516 		return;
472517 	}
473518 
474
-	rq_stat = get_cpu_ptr(iolat->stats);
475
-	blk_rq_stat_add(rq_stat, req_time);
476
-	put_cpu_ptr(rq_stat);
519
+	latency_stat_record_time(iolat, req_time);
477520 }
478521 
479522 #define BLKIOLATENCY_MIN_ADJUST_TIME (500 * NSEC_PER_MSEC)
....@@ -484,17 +527,17 @@
484527 	struct blkcg_gq *blkg = lat_to_blkg(iolat);
485528 	struct iolatency_grp *parent;
486529 	struct child_latency_info *lat_info;
487
-	struct blk_rq_stat stat;
530
+	struct latency_stat stat;
488531 	unsigned long flags;
489
-	int cpu, exp_idx;
532
+	int cpu;
490533 
491
-	blk_rq_stat_init(&stat);
534
+	latency_stat_init(iolat, &stat);
492535 	preempt_disable();
493536 	for_each_online_cpu(cpu) {
494
-		struct blk_rq_stat *s;
537
+		struct latency_stat *s;
495538 		s = per_cpu_ptr(iolat->stats, cpu);
496
-		blk_rq_stat_sum(&stat, s);
497
-		blk_rq_stat_init(s);
539
+		latency_stat_sum(iolat, &stat, s);
540
+		latency_stat_init(iolat, s);
498541 	}
499542 	preempt_enable();
500543 
....@@ -504,43 +547,36 @@
504547 
505548 	lat_info = &parent->child_lat;
506549 
507
-	/*
508
-	 * calc_load() takes in a number stored in fixed point representation.
509
-	 * Because we are using this for IO time in ns, the values stored
510
-	 * are significantly larger than the FIXED_1 denominator (2048).
511
-	 * Therefore, rounding errors in the calculation are negligible and
512
-	 * can be ignored.
513
-	 */
514
-	exp_idx = min_t(int, BLKIOLATENCY_NR_EXP_FACTORS - 1,
515
-			div64_u64(iolat->cur_win_nsec,
516
-				  BLKIOLATENCY_EXP_BUCKET_SIZE));
517
-	iolat->lat_avg = calc_load(iolat->lat_avg,
518
-				   iolatency_exp_factors[exp_idx],
519
-				   stat.mean);
550
+	iolat_update_total_lat_avg(iolat, &stat);
520551 
521552 	/* Everything is ok and we don't need to adjust the scale. */
522
-	if (stat.mean <= iolat->min_lat_nsec &&
553
+	if (latency_sum_ok(iolat, &stat) &&
523554 	    atomic_read(&lat_info->scale_cookie) == DEFAULT_SCALE_COOKIE)
524555 		return;
525556 
526557 	/* Somebody beat us to the punch, just bail. */
527558 	spin_lock_irqsave(&lat_info->lock, flags);
559
+
560
+	latency_stat_sum(iolat, &iolat->cur_stat, &stat);
528561 	lat_info->nr_samples -= iolat->nr_samples;
529
-	lat_info->nr_samples += stat.nr_samples;
530
-	iolat->nr_samples = stat.nr_samples;
562
+	lat_info->nr_samples += latency_stat_samples(iolat, &iolat->cur_stat);
563
+	iolat->nr_samples = latency_stat_samples(iolat, &iolat->cur_stat);
531564 
532565 	if ((lat_info->last_scale_event >= now ||
533
-	    now - lat_info->last_scale_event < BLKIOLATENCY_MIN_ADJUST_TIME) &&
534
-	    lat_info->scale_lat <= iolat->min_lat_nsec)
566
+	    now - lat_info->last_scale_event < BLKIOLATENCY_MIN_ADJUST_TIME))
535567 		goto out;
536568 
537
-	if (stat.mean <= iolat->min_lat_nsec &&
538
-	    stat.nr_samples >= BLKIOLATENCY_MIN_GOOD_SAMPLES) {
569
+	if (latency_sum_ok(iolat, &iolat->cur_stat) &&
570
+	    latency_sum_ok(iolat, &stat)) {
571
+		if (latency_stat_samples(iolat, &iolat->cur_stat) <
572
+		    BLKIOLATENCY_MIN_GOOD_SAMPLES)
573
+			goto out;
539574 		if (lat_info->scale_grp == iolat) {
540575 			lat_info->last_scale_event = now;
541576 			scale_cookie_change(iolat->blkiolat, lat_info, true);
542577 		}
543
-	} else if (stat.mean > iolat->min_lat_nsec) {
578
+	} else if (lat_info->scale_lat == 0 ||
579
+		   lat_info->scale_lat >= iolat->min_lat_nsec) {
544580 		lat_info->last_scale_event = now;
545581 		if (!lat_info->scale_grp ||
546582 		    lat_info->scale_lat > iolat->min_lat_nsec) {
....@@ -549,6 +585,7 @@
549585 		}
550586 		scale_cookie_change(iolat->blkiolat, lat_info, false);
551587 	}
588
+	latency_stat_init(iolat, &iolat->cur_stat);
552589 out:
553590 	spin_unlock_irqrestore(&lat_info->lock, flags);
554591 }
....@@ -559,23 +596,22 @@
559596 	struct rq_wait *rqw;
560597 	struct iolatency_grp *iolat;
561598 	u64 window_start;
562
-	u64 now = ktime_to_ns(ktime_get());
599
+	u64 now;
563600 	bool issue_as_root = bio_issue_as_root_blkg(bio);
564
-	bool enabled = false;
565601 	int inflight = 0;
566602 
567603 	blkg = bio->bi_blkg;
568
-	if (!blkg)
604
+	if (!blkg || !bio_flagged(bio, BIO_TRACKED))
569605 		return;
570606 
571607 	iolat = blkg_to_lat(bio->bi_blkg);
572608 	if (!iolat)
573609 		return;
574610 
575
-	enabled = blk_iolatency_enabled(iolat->blkiolat);
576
-	if (!enabled)
611
+	if (!iolat->blkiolat->enabled)
577612 		return;
578613 
614
+	now = ktime_to_ns(ktime_get());
579615 	while (blkg && blkg->parent) {
580616 		iolat = blkg_to_lat(blkg);
581617 		if (!iolat) {
....@@ -611,6 +647,7 @@
611647 	struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos);
612648 
613649 	del_timer_sync(&blkiolat->timer);
650
+	flush_work(&blkiolat->enable_work);
614651 	blkcg_deactivate_policy(rqos->q, &blkcg_policy_iolatency);
615652 	kfree(blkiolat);
616653 }
....@@ -640,7 +677,7 @@
640677 		 * We could be exiting, don't access the pd unless we have a
641678 		 * ref on the blkg.
642679 		 */
643
-		if (!blkg_try_get(blkg))
680
+		if (!blkg_tryget(blkg))
644681 			continue;
645682 
646683 		iolat = blkg_to_lat(blkg);
....@@ -682,6 +719,44 @@
682719 	rcu_read_unlock();
683720 }
684721 
722
+/**
723
+ * blkiolatency_enable_work_fn - Enable or disable iolatency on the device
724
+ * @work: enable_work of the blk_iolatency of interest
725
+ *
726
+ * iolatency needs to keep track of the number of in-flight IOs per cgroup. This
727
+ * is relatively expensive as it involves walking up the hierarchy twice for
728
+ * every IO. Thus, if iolatency is not enabled in any cgroup for the device, we
729
+ * want to disable the in-flight tracking.
730
+ *
731
+ * We have to make sure that the counting is balanced - we don't want to leak
732
+ * the in-flight counts by disabling accounting in the completion path while IOs
733
+ * are in flight. This is achieved by ensuring that no IO is in flight by
734
+ * freezing the queue while flipping ->enabled. As this requires a sleepable
735
+ * context, ->enabled flipping is punted to this work function.
736
+ */
737
+static void blkiolatency_enable_work_fn(struct work_struct *work)
738
+{
739
+	struct blk_iolatency *blkiolat = container_of(work, struct blk_iolatency,
740
+						      enable_work);
741
+	bool enabled;
742
+
743
+	/*
744
+	 * There can only be one instance of this function running for @blkiolat
745
+	 * and it's guaranteed to be executed at least once after the latest
746
+	 * ->enabled_cnt modification. Acting on the latest ->enable_cnt is
747
+	 * sufficient.
748
+	 *
749
+	 * Also, we know @blkiolat is safe to access as ->enable_work is flushed
750
+	 * in blkcg_iolatency_exit().
751
+	 */
752
+	enabled = atomic_read(&blkiolat->enable_cnt);
753
+	if (enabled != blkiolat->enabled) {
754
+		blk_mq_freeze_queue(blkiolat->rqos.q);
755
+		blkiolat->enabled = enabled;
756
+		blk_mq_unfreeze_queue(blkiolat->rqos.q);
757
+	}
758
+}
759
+
685760 int blk_iolatency_init(struct request_queue *q)
686761 {
687762 	struct blk_iolatency *blkiolat;
....@@ -693,7 +768,7 @@
693768 		return -ENOMEM;
694769 
695770 	rqos = &blkiolat->rqos;
696
-	rqos->id = RQ_QOS_CGROUP;
771
+	rqos->id = RQ_QOS_LATENCY;
697772 	rqos->ops = &blkcg_iolatency_ops;
698773 	rqos->q = q;
699774 
....@@ -707,17 +782,15 @@
707782 	}
708783 
709784 	timer_setup(&blkiolat->timer, blkiolatency_timer_fn, 0);
785
+	INIT_WORK(&blkiolat->enable_work, blkiolatency_enable_work_fn);
710786 
711787 	return 0;
712788 }
713789 
714
-/*
715
- * return 1 for enabling iolatency, return -1 for disabling iolatency, otherwise
716
- * return 0.
717
- */
718
-static int iolatency_set_min_lat_nsec(struct blkcg_gq *blkg, u64 val)
790
+static void iolatency_set_min_lat_nsec(struct blkcg_gq *blkg, u64 val)
719791 {
720792 	struct iolatency_grp *iolat = blkg_to_lat(blkg);
793
+	struct blk_iolatency *blkiolat = iolat->blkiolat;
721794 	u64 oldval = iolat->min_lat_nsec;
722795 
723796 	iolat->min_lat_nsec = val;
....@@ -725,13 +798,15 @@
725798 	iolat->cur_win_nsec = min_t(u64, iolat->cur_win_nsec,
726799 				    BLKIOLATENCY_MAX_WIN_SIZE);
727800 
728
-	if (!oldval && val)
729
-		return 1;
801
+	if (!oldval && val) {
802
+		if (atomic_inc_return(&blkiolat->enable_cnt) == 1)
803
+			schedule_work(&blkiolat->enable_work);
804
+	}
730805 	if (oldval && !val) {
731806 		blkcg_clear_delay(blkg);
732
-		return -1;
807
+		if (atomic_dec_return(&blkiolat->enable_cnt) == 0)
808
+			schedule_work(&blkiolat->enable_work);
733809 	}
734
-	return 0;
735810 }
736811 
737812 static void iolatency_clear_scaling(struct blkcg_gq *blkg)
....@@ -757,21 +832,18 @@
757832 {
758833 	struct blkcg *blkcg = css_to_blkcg(of_css(of));
759834 	struct blkcg_gq *blkg;
760
-	struct blk_iolatency *blkiolat;
761835 	struct blkg_conf_ctx ctx;
762836 	struct iolatency_grp *iolat;
763837 	char *p, *tok;
764838 	u64 lat_val = 0;
765839 	u64 oldval;
766840 	int ret;
767
-	int enable = 0;
768841 
769842 	ret = blkg_conf_prep(blkcg, &blkcg_policy_iolatency, buf, &ctx);
770843 	if (ret)
771844 		return ret;
772845 
773846 	iolat = blkg_to_lat(ctx.blkg);
774
-	blkiolat = iolat->blkiolat;
775847 	p = ctx.body;
776848 
777849 	ret = -EINVAL;
....@@ -800,41 +872,12 @@
800872 	blkg = ctx.blkg;
801873 	oldval = iolat->min_lat_nsec;
802874 
803
-	enable = iolatency_set_min_lat_nsec(blkg, lat_val);
804
-	if (enable) {
805
-		if (!blk_get_queue(blkg->q)) {
806
-			ret = -ENODEV;
807
-			goto out;
808
-		}
809
-
810
-		blkg_get(blkg);
811
-	}
812
-
813
-	if (oldval != iolat->min_lat_nsec) {
875
+	iolatency_set_min_lat_nsec(blkg, lat_val);
876
+	if (oldval != iolat->min_lat_nsec)
814877 		iolatency_clear_scaling(blkg);
815
-	}
816
-
817878 	ret = 0;
818879 out:
819880 	blkg_conf_finish(&ctx);
820
-	if (ret == 0 && enable) {
821
-		struct iolatency_grp *tmp = blkg_to_lat(blkg);
822
-		struct blk_iolatency *blkiolat = tmp->blkiolat;
823
-
824
-		blk_mq_freeze_queue(blkg->q);
825
-
826
-		if (enable == 1)
827
-			atomic_inc(&blkiolat->enabled);
828
-		else if (enable == -1)
829
-			atomic_dec(&blkiolat->enabled);
830
-		else
831
-			WARN_ON_ONCE(1);
832
-
833
-		blk_mq_unfreeze_queue(blkg->q);
834
-
835
-		blkg_put(blkg);
836
-		blk_put_queue(blkg->q);
837
-	}
838881 	return ret ?: nbytes;
839882 }
840883 
....@@ -859,13 +902,46 @@
859902 	return 0;
860903 }
861904 
905
+static size_t iolatency_ssd_stat(struct iolatency_grp *iolat, char *buf,
906
+				 size_t size)
907
+{
908
+	struct latency_stat stat;
909
+	int cpu;
910
+
911
+	latency_stat_init(iolat, &stat);
912
+	preempt_disable();
913
+	for_each_online_cpu(cpu) {
914
+		struct latency_stat *s;
915
+		s = per_cpu_ptr(iolat->stats, cpu);
916
+		latency_stat_sum(iolat, &stat, s);
917
+	}
918
+	preempt_enable();
919
+
920
+	if (iolat->rq_depth.max_depth == UINT_MAX)
921
+		return scnprintf(buf, size, " missed=%llu total=%llu depth=max",
922
+				 (unsigned long long)stat.ps.missed,
923
+				 (unsigned long long)stat.ps.total);
924
+	return scnprintf(buf, size, " missed=%llu total=%llu depth=%u",
925
+			 (unsigned long long)stat.ps.missed,
926
+			 (unsigned long long)stat.ps.total,
927
+			 iolat->rq_depth.max_depth);
928
+}
929
+
862930 static size_t iolatency_pd_stat(struct blkg_policy_data *pd, char *buf,
863931 				size_t size)
864932 {
865933 	struct iolatency_grp *iolat = pd_to_lat(pd);
866
-	unsigned long long avg_lat = div64_u64(iolat->lat_avg, NSEC_PER_USEC);
867
-	unsigned long long cur_win = div64_u64(iolat->cur_win_nsec, NSEC_PER_MSEC);
934
+	unsigned long long avg_lat;
935
+	unsigned long long cur_win;
868936 
937
+	if (!blkcg_debug_stats)
938
+		return 0;
939
+
940
+	if (iolat->ssd)
941
+		return iolatency_ssd_stat(iolat, buf, size);
942
+
943
+	avg_lat = div64_u64(iolat->lat_avg, NSEC_PER_USEC);
944
+	cur_win = div64_u64(iolat->cur_win_nsec, NSEC_PER_MSEC);
869945 	if (iolat->rq_depth.max_depth == UINT_MAX)
870946 		return scnprintf(buf, size, " depth=max avg_lat=%llu win=%llu",
871947 				 avg_lat, cur_win);
....@@ -875,15 +951,17 @@
875951 }
876952 
877953 
878
-static struct blkg_policy_data *iolatency_pd_alloc(gfp_t gfp, int node)
954
+static struct blkg_policy_data *iolatency_pd_alloc(gfp_t gfp,
955
+						   struct request_queue *q,
956
+						   struct blkcg *blkcg)
879957 {
880958 	struct iolatency_grp *iolat;
881959 
882
-	iolat = kzalloc_node(sizeof(*iolat), gfp, node);
960
+	iolat = kzalloc_node(sizeof(*iolat), gfp, q->node);
883961 	if (!iolat)
884962 		return NULL;
885
-	iolat->stats = __alloc_percpu_gfp(sizeof(struct blk_rq_stat),
886
-				       __alignof__(struct blk_rq_stat), gfp);
963
+	iolat->stats = __alloc_percpu_gfp(sizeof(struct latency_stat),
964
+				       __alignof__(struct latency_stat), gfp);
887965 	if (!iolat->stats) {
888966 		kfree(iolat);
889967 		return NULL;
....@@ -900,15 +978,21 @@
900978 	u64 now = ktime_to_ns(ktime_get());
901979 	int cpu;
902980 
981
+	if (blk_queue_nonrot(blkg->q))
982
+		iolat->ssd = true;
983
+	else
984
+		iolat->ssd = false;
985
+
903986 	for_each_possible_cpu(cpu) {
904
-		struct blk_rq_stat *stat;
987
+		struct latency_stat *stat;
905988 		stat = per_cpu_ptr(iolat->stats, cpu);
906
-		blk_rq_stat_init(stat);
989
+		latency_stat_init(iolat, stat);
907990 	}
908991 
992
+	latency_stat_init(iolat, &iolat->cur_stat);
909993 	rq_wait_init(&iolat->rq_wait);
910994 	spin_lock_init(&iolat->child_lat.lock);
911
-	iolat->rq_depth.queue_depth = blk_queue_depth(blkg->q);
995
+	iolat->rq_depth.queue_depth = blkg->q->nr_requests;
912996 	iolat->rq_depth.max_depth = UINT_MAX;
913997 	iolat->rq_depth.default_depth = iolat->rq_depth.queue_depth;
914998 	iolat->blkiolat = blkiolat;
....@@ -934,14 +1018,8 @@
9341018 {
9351019 	struct iolatency_grp *iolat = pd_to_lat(pd);
9361020 	struct blkcg_gq *blkg = lat_to_blkg(iolat);
937
-	struct blk_iolatency *blkiolat = iolat->blkiolat;
938
-	int ret;
9391021 
940
-	ret = iolatency_set_min_lat_nsec(blkg, 0);
941
-	if (ret == 1)
942
-		atomic_inc(&blkiolat->enabled);
943
-	if (ret == -1)
944
-		atomic_dec(&blkiolat->enabled);
1022
+	iolatency_set_min_lat_nsec(blkg, 0);
9451023 	iolatency_clear_scaling(blkg);
9461024 }
9471025 
....@@ -978,7 +1056,7 @@
9781056 
9791057 static void __exit iolatency_exit(void)
9801058 {
981
-	return blkcg_policy_unregister(&blkcg_policy_iolatency);
1059
+	blkcg_policy_unregister(&blkcg_policy_iolatency);
9821060 }
9831061 
9841062 module_init(iolatency_init);