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 */
 19struct 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
 65struct blk_queue_stats *blk_alloc_queue_stats(void);
 66void blk_free_queue_stats(struct blk_queue_stats *);
 67bool blk_stats_alloc_enable(struct request_queue *q);
 68
 69void blk_stat_add(struct request *rq, u64 now);
 70
 71/* record time/size info in request but not add a callback */
 72void blk_stat_enable_accounting(struct request_queue *q);
 73void blk_stat_disable_accounting(struct request_queue *q);
 74
 75/**
 76 * blk_stat_alloc_callback() - Allocate a block statistics callback.
 77 * @timer_fn: Timer callback function.
 78 * @bucket_fn: Bucket callback function.
 79 * @buckets: Number of statistics buckets.
 80 * @data: Value for the @data field of the &struct blk_stat_callback.
 81 *
 82 * See &struct blk_stat_callback for details on the callback functions.
 83 *
 84 * Return: &struct blk_stat_callback on success or NULL on ENOMEM.
 85 */
 86struct blk_stat_callback *
 87blk_stat_alloc_callback(void (*timer_fn)(struct blk_stat_callback *),
 88			int (*bucket_fn)(const struct request *),
 89			unsigned int buckets, void *data);
 90
 91/**
 92 * blk_stat_add_callback() - Add a block statistics callback to be run on a
 93 * request queue.
 94 * @q: The request queue.
 95 * @cb: The callback.
 96 *
 97 * Note that a single &struct blk_stat_callback can only be added to a single
 98 * &struct request_queue.
 99 */
100void blk_stat_add_callback(struct request_queue *q,
101			   struct blk_stat_callback *cb);
102
103/**
104 * blk_stat_remove_callback() - Remove a block statistics callback from a
105 * request queue.
106 * @q: The request queue.
107 * @cb: The callback.
108 *
109 * When this returns, the callback is not running on any CPUs and will not be
110 * called again unless readded.
111 */
112void blk_stat_remove_callback(struct request_queue *q,
113			      struct blk_stat_callback *cb);
114
115/**
116 * blk_stat_free_callback() - Free a block statistics callback.
117 * @cb: The callback.
118 *
119 * @cb may be NULL, in which case this does nothing. If it is not NULL, @cb must
120 * not be associated with a request queue. I.e., if it was previously added with
121 * blk_stat_add_callback(), it must also have been removed since then with
122 * blk_stat_remove_callback().
123 */
124void blk_stat_free_callback(struct blk_stat_callback *cb);
125
126/**
127 * blk_stat_is_active() - Check if a block statistics callback is currently
128 * gathering statistics.
129 * @cb: The callback.
130 */
131static inline bool blk_stat_is_active(struct blk_stat_callback *cb)
132{
133	return timer_pending(&cb->timer);
134}
135
136/**
137 * blk_stat_activate_nsecs() - Gather block statistics during a time window in
138 * nanoseconds.
139 * @cb: The callback.
140 * @nsecs: Number of nanoseconds to gather statistics for.
141 *
142 * The timer callback will be called when the window expires.
143 */
144static inline void blk_stat_activate_nsecs(struct blk_stat_callback *cb,
145					   u64 nsecs)
146{
147	mod_timer(&cb->timer, jiffies + nsecs_to_jiffies(nsecs));
148}
149
150static inline void blk_stat_deactivate(struct blk_stat_callback *cb)
151{
152	del_timer_sync(&cb->timer);
153}
154
155/**
156 * blk_stat_activate_msecs() - Gather block statistics during a time window in
157 * milliseconds.
158 * @cb: The callback.
159 * @msecs: Number of milliseconds to gather statistics for.
160 *
161 * The timer callback will be called when the window expires.
162 */
163static inline void blk_stat_activate_msecs(struct blk_stat_callback *cb,
164					   unsigned int msecs)
165{
166	mod_timer(&cb->timer, jiffies + msecs_to_jiffies(msecs));
167}
168
169void blk_rq_stat_add(struct blk_rq_stat *, u64);
170void blk_rq_stat_sum(struct blk_rq_stat *, struct blk_rq_stat *);
171void blk_rq_stat_init(struct blk_rq_stat *);
172
173#endif