1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef BLK_STAT_H
3 #define BLK_STAT_H
4
5 #include <linux/kernel.h>
6 #include <linux/blkdev.h>
7 #include <linux/ktime.h>
8 #include <linux/rcupdate.h>
9 #include <linux/timer.h>
10
11 /**
12 * struct blk_stat_callback - Block statistics callback.
13 *
14 * A &struct blk_stat_callback is associated with a &struct request_queue. While
15 * @timer is active, that queue's request completion latencies are sorted into
16 * buckets by @bucket_fn and added to a per-cpu buffer, @cpu_stat. When the
17 * timer fires, @cpu_stat is flushed to @stat and @timer_fn is invoked.
18 */
19 struct blk_stat_callback {
20 /*
21 * @list: RCU list of callbacks for a &struct request_queue.
22 */
23 struct list_head list;
24
25 /**
26 * @timer: Timer for the next callback invocation.
27 */
28 struct timer_list timer;
29
30 /**
31 * @cpu_stat: Per-cpu statistics buckets.
32 */
33 struct blk_rq_stat __percpu *cpu_stat;
34
35 /**
36 * @bucket_fn: Given a request, returns which statistics bucket it
37 * should be accounted under. Return -1 for no bucket for this
38 * request.
39 */
40 int (*bucket_fn)(const struct request *);
41
42 /**
43 * @buckets: Number of statistics buckets.
44 */
45 unsigned int buckets;
46
47 /**
48 * @stat: Array of statistics buckets.
49 */
50 struct blk_rq_stat *stat;
51
52 /**
53 * @fn: Callback function.
54 */
55 void (*timer_fn)(struct blk_stat_callback *);
56
57 /**
58 * @data: Private pointer for the user.
59 */
60 void *data;
61
62 struct rcu_head rcu;
63 };
64
65 struct blk_queue_stats *blk_alloc_queue_stats(void);
66 void blk_free_queue_stats(struct blk_queue_stats *);
67
68 void blk_stat_add(struct request *rq, u64 now);
69
70 /* record time/size info in request but not add a callback */
71 void blk_stat_enable_accounting(struct request_queue *q);
72
73 /**
74 * blk_stat_alloc_callback() - Allocate a block statistics callback.
75 * @timer_fn: Timer callback function.
76 * @bucket_fn: Bucket callback function.
77 * @buckets: Number of statistics buckets.
78 * @data: Value for the @data field of the &struct blk_stat_callback.
79 *
80 * See &struct blk_stat_callback for details on the callback functions.
81 *
82 * Return: &struct blk_stat_callback on success or NULL on ENOMEM.
83 */
84 struct blk_stat_callback *
85 blk_stat_alloc_callback(void (*timer_fn)(struct blk_stat_callback *),
86 int (*bucket_fn)(const struct request *),
87 unsigned int buckets, void *data);
88
89 /**
90 * blk_stat_add_callback() - Add a block statistics callback to be run on a
91 * request queue.
92 * @q: The request queue.
93 * @cb: The callback.
94 *
95 * Note that a single &struct blk_stat_callback can only be added to a single
96 * &struct request_queue.
97 */
98 void blk_stat_add_callback(struct request_queue *q,
99 struct blk_stat_callback *cb);
100
101 /**
102 * blk_stat_remove_callback() - Remove a block statistics callback from a
103 * request queue.
104 * @q: The request queue.
105 * @cb: The callback.
106 *
107 * When this returns, the callback is not running on any CPUs and will not be
108 * called again unless readded.
109 */
110 void blk_stat_remove_callback(struct request_queue *q,
111 struct blk_stat_callback *cb);
112
113 /**
114 * blk_stat_free_callback() - Free a block statistics callback.
115 * @cb: The callback.
116 *
117 * @cb may be NULL, in which case this does nothing. If it is not NULL, @cb must
118 * not be associated with a request queue. I.e., if it was previously added with
119 * blk_stat_add_callback(), it must also have been removed since then with
120 * blk_stat_remove_callback().
121 */
122 void blk_stat_free_callback(struct blk_stat_callback *cb);
123
124 /**
125 * blk_stat_is_active() - Check if a block statistics callback is currently
126 * gathering statistics.
127 * @cb: The callback.
128 */
blk_stat_is_active(struct blk_stat_callback * cb)129 static inline bool blk_stat_is_active(struct blk_stat_callback *cb)
130 {
131 return timer_pending(&cb->timer);
132 }
133
134 /**
135 * blk_stat_activate_nsecs() - Gather block statistics during a time window in
136 * nanoseconds.
137 * @cb: The callback.
138 * @nsecs: Number of nanoseconds to gather statistics for.
139 *
140 * The timer callback will be called when the window expires.
141 */
blk_stat_activate_nsecs(struct blk_stat_callback * cb,u64 nsecs)142 static inline void blk_stat_activate_nsecs(struct blk_stat_callback *cb,
143 u64 nsecs)
144 {
145 mod_timer(&cb->timer, jiffies + nsecs_to_jiffies(nsecs));
146 }
147
148 /**
149 * blk_stat_activate_msecs() - Gather block statistics during a time window in
150 * milliseconds.
151 * @cb: The callback.
152 * @msecs: Number of milliseconds to gather statistics for.
153 *
154 * The timer callback will be called when the window expires.
155 */
blk_stat_activate_msecs(struct blk_stat_callback * cb,unsigned int msecs)156 static inline void blk_stat_activate_msecs(struct blk_stat_callback *cb,
157 unsigned int msecs)
158 {
159 mod_timer(&cb->timer, jiffies + msecs_to_jiffies(msecs));
160 }
161
162 void blk_rq_stat_add(struct blk_rq_stat *, u64);
163 void blk_rq_stat_sum(struct blk_rq_stat *, struct blk_rq_stat *);
164 void blk_rq_stat_init(struct blk_rq_stat *);
165
166 #endif
167
