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 * @timer_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 /** 63 * @rcu: rcu list head 64 */ 65 struct rcu_head rcu; 66 }; 67 68 struct blk_queue_stats *blk_alloc_queue_stats(void); 69 void blk_free_queue_stats(struct blk_queue_stats *); 70 71 void blk_stat_add(struct request *rq, u64 now); 72 73 /* record time/size info in request but not add a callback */ 74 void blk_stat_enable_accounting(struct request_queue *q); 75 void blk_stat_disable_accounting(struct request_queue *q); 76 77 /** 78 * blk_stat_alloc_callback() - Allocate a block statistics callback. 79 * @timer_fn: Timer callback function. 80 * @bucket_fn: Bucket callback function. 81 * @buckets: Number of statistics buckets. 82 * @data: Value for the @data field of the &struct blk_stat_callback. 83 * 84 * See &struct blk_stat_callback for details on the callback functions. 85 * 86 * Return: &struct blk_stat_callback on success or NULL on ENOMEM. 87 */ 88 struct blk_stat_callback * 89 blk_stat_alloc_callback(void (*timer_fn)(struct blk_stat_callback *), 90 int (*bucket_fn)(const struct request *), 91 unsigned int buckets, void *data); 92 93 /** 94 * blk_stat_add_callback() - Add a block statistics callback to be run on a 95 * request queue. 96 * @q: The request queue. 97 * @cb: The callback. 98 * 99 * Note that a single &struct blk_stat_callback can only be added to a single 100 * &struct request_queue. 101 */ 102 void blk_stat_add_callback(struct request_queue *q, 103 struct blk_stat_callback *cb); 104 105 /** 106 * blk_stat_remove_callback() - Remove a block statistics callback from a 107 * request queue. 108 * @q: The request queue. 109 * @cb: The callback. 110 * 111 * When this returns, the callback is not running on any CPUs and will not be 112 * called again unless readded. 113 */ 114 void blk_stat_remove_callback(struct request_queue *q, 115 struct blk_stat_callback *cb); 116 117 /** 118 * blk_stat_free_callback() - Free a block statistics callback. 119 * @cb: The callback. 120 * 121 * @cb may be NULL, in which case this does nothing. If it is not NULL, @cb must 122 * not be associated with a request queue. I.e., if it was previously added with 123 * blk_stat_add_callback(), it must also have been removed since then with 124 * blk_stat_remove_callback(). 125 */ 126 void blk_stat_free_callback(struct blk_stat_callback *cb); 127 128 /** 129 * blk_stat_is_active() - Check if a block statistics callback is currently 130 * gathering statistics. 131 * @cb: The callback. 132 * 133 * Returns: %true iff the callback is active. 134 */ 135 static inline bool blk_stat_is_active(struct blk_stat_callback *cb) 136 { 137 return timer_pending(&cb->timer); 138 } 139 140 /** 141 * blk_stat_activate_nsecs() - Gather block statistics during a time window in 142 * nanoseconds. 143 * @cb: The callback. 144 * @nsecs: Number of nanoseconds to gather statistics for. 145 * 146 * The timer callback will be called when the window expires. 147 */ 148 static inline void blk_stat_activate_nsecs(struct blk_stat_callback *cb, 149 u64 nsecs) 150 { 151 mod_timer(&cb->timer, jiffies + nsecs_to_jiffies(nsecs)); 152 } 153 154 static inline void blk_stat_deactivate(struct blk_stat_callback *cb) 155 { 156 timer_delete_sync(&cb->timer); 157 } 158 159 /** 160 * blk_stat_activate_msecs() - Gather block statistics during a time window in 161 * milliseconds. 162 * @cb: The callback. 163 * @msecs: Number of milliseconds to gather statistics for. 164 * 165 * The timer callback will be called when the window expires. 166 */ 167 static inline void blk_stat_activate_msecs(struct blk_stat_callback *cb, 168 unsigned int msecs) 169 { 170 mod_timer(&cb->timer, jiffies + msecs_to_jiffies(msecs)); 171 } 172 173 void blk_rq_stat_add(struct blk_rq_stat *, u64); 174 void blk_rq_stat_sum(struct blk_rq_stat *, struct blk_rq_stat *); 175 void blk_rq_stat_init(struct blk_rq_stat *); 176 177 #endif 178