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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                 :            :  */
     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                 :            : 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                 :            :  */
     161                 :          0 : static inline void blk_stat_activate_msecs(struct blk_stat_callback *cb,
     162                 :            :                                            unsigned int msecs)
     163                 :            : {
     164                 :          0 :         mod_timer(&cb->timer, jiffies + msecs_to_jiffies(msecs));
     165                 :          0 : }
     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