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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 
blk_stat_deactivate(struct blk_stat_callback * cb)148 static inline void blk_stat_deactivate(struct blk_stat_callback *cb)
149 {
150 	del_timer_sync(&cb->timer);
151 }
152 
153 /**
154  * blk_stat_activate_msecs() - Gather block statistics during a time window in
155  * milliseconds.
156  * @cb: The callback.
157  * @msecs: Number of milliseconds to gather statistics for.
158  *
159  * The timer callback will be called when the window expires.
160  */
blk_stat_activate_msecs(struct blk_stat_callback * cb,unsigned int msecs)161 static inline void blk_stat_activate_msecs(struct blk_stat_callback *cb,
162 					   unsigned int msecs)
163 {
164 	mod_timer(&cb->timer, jiffies + msecs_to_jiffies(msecs));
165 }
166 
167 void blk_rq_stat_add(struct blk_rq_stat *, u64);
168 void blk_rq_stat_sum(struct blk_rq_stat *, struct blk_rq_stat *);
169 void blk_rq_stat_init(struct blk_rq_stat *);
170 
171 #endif
172