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 * from upper:
 13 * 3 bits: reserved for other usage
 14 * 12 bits: size
 15 * 49 bits: time
 16 */
 17#define BLK_STAT_RES_BITS	3
 18#define BLK_STAT_SIZE_BITS	12
 19#define BLK_STAT_RES_SHIFT	(64 - BLK_STAT_RES_BITS)
 20#define BLK_STAT_SIZE_SHIFT	(BLK_STAT_RES_SHIFT - BLK_STAT_SIZE_BITS)
 21#define BLK_STAT_TIME_MASK	((1ULL << BLK_STAT_SIZE_SHIFT) - 1)
 22#define BLK_STAT_SIZE_MASK	\
 23	(((1ULL << BLK_STAT_SIZE_BITS) - 1) << BLK_STAT_SIZE_SHIFT)
 24#define BLK_STAT_RES_MASK	(~((1ULL << BLK_STAT_RES_SHIFT) - 1))
 25
 26/**
 27 * struct blk_stat_callback - Block statistics callback.
 28 *
 29 * A &struct blk_stat_callback is associated with a &struct request_queue. While
 30 * @timer is active, that queue's request completion latencies are sorted into
 31 * buckets by @bucket_fn and added to a per-cpu buffer, @cpu_stat. When the
 32 * timer fires, @cpu_stat is flushed to @stat and @timer_fn is invoked.
 33 */
 34struct blk_stat_callback {
 35	/*
 36	 * @list: RCU list of callbacks for a &struct request_queue.
 37	 */
 38	struct list_head list;
 39
 40	/**
 41	 * @timer: Timer for the next callback invocation.
 42	 */
 43	struct timer_list timer;
 44
 45	/**
 46	 * @cpu_stat: Per-cpu statistics buckets.
 47	 */
 48	struct blk_rq_stat __percpu *cpu_stat;
 49
 50	/**
 51	 * @bucket_fn: Given a request, returns which statistics bucket it
 52	 * should be accounted under. Return -1 for no bucket for this
 53	 * request.
 54	 */
 55	int (*bucket_fn)(const struct request *);
 56
 57	/**
 58	 * @buckets: Number of statistics buckets.
 59	 */
 60	unsigned int buckets;
 61
 62	/**
 63	 * @stat: Array of statistics buckets.
 64	 */
 65	struct blk_rq_stat *stat;
 66
 67	/**
 68	 * @fn: Callback function.
 69	 */
 70	void (*timer_fn)(struct blk_stat_callback *);
 71
 72	/**
 73	 * @data: Private pointer for the user.
 74	 */
 75	void *data;
 76
 77	struct rcu_head rcu;
 78};
 79
 80struct blk_queue_stats *blk_alloc_queue_stats(void);
 81void blk_free_queue_stats(struct blk_queue_stats *);
 82
 83void blk_stat_add(struct request *);
 84
 85static inline u64 __blk_stat_time(u64 time)
 86{
 87	return time & BLK_STAT_TIME_MASK;
 88}
 89
 90static inline u64 blk_stat_time(struct blk_issue_stat *stat)
 91{
 92	return __blk_stat_time(stat->stat);
 93}
 94
 95static inline sector_t blk_capped_size(sector_t size)
 96{
 97	return size & ((1ULL << BLK_STAT_SIZE_BITS) - 1);
 98}
 99
100static inline sector_t blk_stat_size(struct blk_issue_stat *stat)
101{
102	return (stat->stat & BLK_STAT_SIZE_MASK) >> BLK_STAT_SIZE_SHIFT;
103}
104
105static inline void blk_stat_set_issue(struct blk_issue_stat *stat,
106	sector_t size)
107{
108	stat->stat = (stat->stat & BLK_STAT_RES_MASK) |
109		(ktime_to_ns(ktime_get()) & BLK_STAT_TIME_MASK) |
110		(((u64)blk_capped_size(size)) << BLK_STAT_SIZE_SHIFT);
111}
112
113/* record time/size info in request but not add a callback */
114void blk_stat_enable_accounting(struct request_queue *q);
115
116/**
117 * blk_stat_alloc_callback() - Allocate a block statistics callback.
118 * @timer_fn: Timer callback function.
119 * @bucket_fn: Bucket callback function.
120 * @buckets: Number of statistics buckets.
121 * @data: Value for the @data field of the &struct blk_stat_callback.
122 *
123 * See &struct blk_stat_callback for details on the callback functions.
124 *
125 * Return: &struct blk_stat_callback on success or NULL on ENOMEM.
126 */
127struct blk_stat_callback *
128blk_stat_alloc_callback(void (*timer_fn)(struct blk_stat_callback *),
129			int (*bucket_fn)(const struct request *),
130			unsigned int buckets, void *data);
131
132/**
133 * blk_stat_add_callback() - Add a block statistics callback to be run on a
134 * request queue.
135 * @q: The request queue.
136 * @cb: The callback.
137 *
138 * Note that a single &struct blk_stat_callback can only be added to a single
139 * &struct request_queue.
140 */
141void blk_stat_add_callback(struct request_queue *q,
142			   struct blk_stat_callback *cb);
143
144/**
145 * blk_stat_remove_callback() - Remove a block statistics callback from a
146 * request queue.
147 * @q: The request queue.
148 * @cb: The callback.
149 *
150 * When this returns, the callback is not running on any CPUs and will not be
151 * called again unless readded.
152 */
153void blk_stat_remove_callback(struct request_queue *q,
154			      struct blk_stat_callback *cb);
155
156/**
157 * blk_stat_free_callback() - Free a block statistics callback.
158 * @cb: The callback.
159 *
160 * @cb may be NULL, in which case this does nothing. If it is not NULL, @cb must
161 * not be associated with a request queue. I.e., if it was previously added with
162 * blk_stat_add_callback(), it must also have been removed since then with
163 * blk_stat_remove_callback().
164 */
165void blk_stat_free_callback(struct blk_stat_callback *cb);
166
167/**
168 * blk_stat_is_active() - Check if a block statistics callback is currently
169 * gathering statistics.
170 * @cb: The callback.
171 */
172static inline bool blk_stat_is_active(struct blk_stat_callback *cb)
173{
174	return timer_pending(&cb->timer);
175}
176
177/**
178 * blk_stat_activate_nsecs() - Gather block statistics during a time window in
179 * nanoseconds.
180 * @cb: The callback.
181 * @nsecs: Number of nanoseconds to gather statistics for.
182 *
183 * The timer callback will be called when the window expires.
184 */
185static inline void blk_stat_activate_nsecs(struct blk_stat_callback *cb,
186					   u64 nsecs)
187{
188	mod_timer(&cb->timer, jiffies + nsecs_to_jiffies(nsecs));
189}
190
191/**
192 * blk_stat_activate_msecs() - Gather block statistics during a time window in
193 * milliseconds.
194 * @cb: The callback.
195 * @msecs: Number of milliseconds to gather statistics for.
196 *
197 * The timer callback will be called when the window expires.
198 */
199static inline void blk_stat_activate_msecs(struct blk_stat_callback *cb,
200					   unsigned int msecs)
201{
202	mod_timer(&cb->timer, jiffies + msecs_to_jiffies(msecs));
203}
204
205#endif