1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Block stat tracking code
4  *
5  * Copyright (C) 2016 Jens Axboe
6  */
7 #include <linux/kernel.h>
8 #include <linux/rculist.h>
9 #include <linux/blk-mq.h>
10 
11 #include "blk-stat.h"
12 #include "blk-mq.h"
13 #include "blk.h"
14 
15 struct blk_queue_stats {
16 	struct list_head callbacks;
17 	spinlock_t lock;
18 	bool enable_accounting;
19 };
20 
blk_rq_stat_init(struct blk_rq_stat * stat)21 void blk_rq_stat_init(struct blk_rq_stat *stat)
22 {
23 	stat->min = -1ULL;
24 	stat->max = stat->nr_samples = stat->mean = 0;
25 	stat->batch = 0;
26 }
27 
28 /* src is a per-cpu stat, mean isn't initialized */
blk_rq_stat_sum(struct blk_rq_stat * dst,struct blk_rq_stat * src)29 void blk_rq_stat_sum(struct blk_rq_stat *dst, struct blk_rq_stat *src)
30 {
31 	if (!src->nr_samples)
32 		return;
33 
34 	dst->min = min(dst->min, src->min);
35 	dst->max = max(dst->max, src->max);
36 
37 	dst->mean = div_u64(src->batch + dst->mean * dst->nr_samples,
38 				dst->nr_samples + src->nr_samples);
39 
40 	dst->nr_samples += src->nr_samples;
41 }
42 
blk_rq_stat_add(struct blk_rq_stat * stat,u64 value)43 void blk_rq_stat_add(struct blk_rq_stat *stat, u64 value)
44 {
45 	stat->min = min(stat->min, value);
46 	stat->max = max(stat->max, value);
47 	stat->batch += value;
48 	stat->nr_samples++;
49 }
50 
blk_stat_add(struct request * rq,u64 now)51 void blk_stat_add(struct request *rq, u64 now)
52 {
53 	struct request_queue *q = rq->q;
54 	struct blk_stat_callback *cb;
55 	struct blk_rq_stat *stat;
56 	int bucket, cpu;
57 	u64 value;
58 
59 	value = (now >= rq->io_start_time_ns) ? now - rq->io_start_time_ns : 0;
60 
61 	blk_throtl_stat_add(rq, value);
62 
63 	rcu_read_lock();
64 	cpu = get_cpu();
65 	list_for_each_entry_rcu(cb, &q->stats->callbacks, list) {
66 		if (!blk_stat_is_active(cb))
67 			continue;
68 
69 		bucket = cb->bucket_fn(rq);
70 		if (bucket < 0)
71 			continue;
72 
73 		stat = &per_cpu_ptr(cb->cpu_stat, cpu)[bucket];
74 		blk_rq_stat_add(stat, value);
75 	}
76 	put_cpu();
77 	rcu_read_unlock();
78 }
79 
blk_stat_timer_fn(struct timer_list * t)80 static void blk_stat_timer_fn(struct timer_list *t)
81 {
82 	struct blk_stat_callback *cb = from_timer(cb, t, timer);
83 	unsigned int bucket;
84 	int cpu;
85 
86 	for (bucket = 0; bucket < cb->buckets; bucket++)
87 		blk_rq_stat_init(&cb->stat[bucket]);
88 
89 	for_each_online_cpu(cpu) {
90 		struct blk_rq_stat *cpu_stat;
91 
92 		cpu_stat = per_cpu_ptr(cb->cpu_stat, cpu);
93 		for (bucket = 0; bucket < cb->buckets; bucket++) {
94 			blk_rq_stat_sum(&cb->stat[bucket], &cpu_stat[bucket]);
95 			blk_rq_stat_init(&cpu_stat[bucket]);
96 		}
97 	}
98 
99 	cb->timer_fn(cb);
100 }
101 
102 struct blk_stat_callback *
blk_stat_alloc_callback(void (* timer_fn)(struct blk_stat_callback *),int (* bucket_fn)(const struct request *),unsigned int buckets,void * data)103 blk_stat_alloc_callback(void (*timer_fn)(struct blk_stat_callback *),
104 			int (*bucket_fn)(const struct request *),
105 			unsigned int buckets, void *data)
106 {
107 	struct blk_stat_callback *cb;
108 
109 	cb = kmalloc(sizeof(*cb), GFP_KERNEL);
110 	if (!cb)
111 		return NULL;
112 
113 	cb->stat = kmalloc_array(buckets, sizeof(struct blk_rq_stat),
114 				 GFP_KERNEL);
115 	if (!cb->stat) {
116 		kfree(cb);
117 		return NULL;
118 	}
119 	cb->cpu_stat = __alloc_percpu(buckets * sizeof(struct blk_rq_stat),
120 				      __alignof__(struct blk_rq_stat));
121 	if (!cb->cpu_stat) {
122 		kfree(cb->stat);
123 		kfree(cb);
124 		return NULL;
125 	}
126 
127 	cb->timer_fn = timer_fn;
128 	cb->bucket_fn = bucket_fn;
129 	cb->data = data;
130 	cb->buckets = buckets;
131 	timer_setup(&cb->timer, blk_stat_timer_fn, 0);
132 
133 	return cb;
134 }
135 
blk_stat_add_callback(struct request_queue * q,struct blk_stat_callback * cb)136 void blk_stat_add_callback(struct request_queue *q,
137 			   struct blk_stat_callback *cb)
138 {
139 	unsigned int bucket;
140 	unsigned long flags;
141 	int cpu;
142 
143 	for_each_possible_cpu(cpu) {
144 		struct blk_rq_stat *cpu_stat;
145 
146 		cpu_stat = per_cpu_ptr(cb->cpu_stat, cpu);
147 		for (bucket = 0; bucket < cb->buckets; bucket++)
148 			blk_rq_stat_init(&cpu_stat[bucket]);
149 	}
150 
151 	spin_lock_irqsave(&q->stats->lock, flags);
152 	list_add_tail_rcu(&cb->list, &q->stats->callbacks);
153 	blk_queue_flag_set(QUEUE_FLAG_STATS, q);
154 	spin_unlock_irqrestore(&q->stats->lock, flags);
155 }
156 
blk_stat_remove_callback(struct request_queue * q,struct blk_stat_callback * cb)157 void blk_stat_remove_callback(struct request_queue *q,
158 			      struct blk_stat_callback *cb)
159 {
160 	unsigned long flags;
161 
162 	spin_lock_irqsave(&q->stats->lock, flags);
163 	list_del_rcu(&cb->list);
164 	if (list_empty(&q->stats->callbacks) && !q->stats->enable_accounting)
165 		blk_queue_flag_clear(QUEUE_FLAG_STATS, q);
166 	spin_unlock_irqrestore(&q->stats->lock, flags);
167 
168 	del_timer_sync(&cb->timer);
169 }
170 
blk_stat_free_callback_rcu(struct rcu_head * head)171 static void blk_stat_free_callback_rcu(struct rcu_head *head)
172 {
173 	struct blk_stat_callback *cb;
174 
175 	cb = container_of(head, struct blk_stat_callback, rcu);
176 	free_percpu(cb->cpu_stat);
177 	kfree(cb->stat);
178 	kfree(cb);
179 }
180 
blk_stat_free_callback(struct blk_stat_callback * cb)181 void blk_stat_free_callback(struct blk_stat_callback *cb)
182 {
183 	if (cb)
184 		call_rcu(&cb->rcu, blk_stat_free_callback_rcu);
185 }
186 
blk_stat_enable_accounting(struct request_queue * q)187 void blk_stat_enable_accounting(struct request_queue *q)
188 {
189 	unsigned long flags;
190 
191 	spin_lock_irqsave(&q->stats->lock, flags);
192 	q->stats->enable_accounting = true;
193 	blk_queue_flag_set(QUEUE_FLAG_STATS, q);
194 	spin_unlock_irqrestore(&q->stats->lock, flags);
195 }
196 EXPORT_SYMBOL_GPL(blk_stat_enable_accounting);
197 
blk_alloc_queue_stats(void)198 struct blk_queue_stats *blk_alloc_queue_stats(void)
199 {
200 	struct blk_queue_stats *stats;
201 
202 	stats = kmalloc(sizeof(*stats), GFP_KERNEL);
203 	if (!stats)
204 		return NULL;
205 
206 	INIT_LIST_HEAD(&stats->callbacks);
207 	spin_lock_init(&stats->lock);
208 	stats->enable_accounting = false;
209 
210 	return stats;
211 }
212 
blk_free_queue_stats(struct blk_queue_stats * stats)213 void blk_free_queue_stats(struct blk_queue_stats *stats)
214 {
215 	if (!stats)
216 		return;
217 
218 	WARN_ON(!list_empty(&stats->callbacks));
219 
220 	kfree(stats);
221 }
222