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 */ 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 */ 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 */ 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 #endif 163