include/linux/elevator.h

   1 #ifndef _LINUX_ELEVATOR_H
   2 #define _LINUX_ELEVATOR_H
   3
   4 typedef int (elevator_merge_fn) (request_queue_t *, struct request **,
   5                                  struct bio *);
   6
   7 typedef void (elevator_merge_req_fn) (request_queue_t *, struct request *, struct request *);
   8
   9 typedef void (elevator_merged_fn) (request_queue_t *, struct request *);
  10
  11 typedef struct request *(elevator_next_req_fn) (request_queue_t *);
  12
  13 typedef void (elevator_add_req_fn) (request_queue_t *, struct request *, int);
  14 typedef int (elevator_queue_empty_fn) (request_queue_t *);
  15 typedef void (elevator_remove_req_fn) (request_queue_t *, struct request *);
  16 typedef void (elevator_requeue_req_fn) (request_queue_t *, struct request *);
  17 typedef struct request *(elevator_request_list_fn) (request_queue_t *, struct request *);
  18 typedef void (elevator_completed_req_fn) (request_queue_t *, struct request *);
  19 typedef int (elevator_may_queue_fn) (request_queue_t *, int);
  20
  21 typedef int (elevator_set_req_fn) (request_queue_t *, struct request *, int);
  22 typedef void (elevator_put_req_fn) (request_queue_t *, struct request *);
  23
  24 typedef int (elevator_init_fn) (request_queue_t *, elevator_t *);
  25 typedef void (elevator_exit_fn) (request_queue_t *, elevator_t *);
  26
  27 struct elevator_s
  28 {
  29         elevator_merge_fn *elevator_merge_fn;
  30         elevator_merged_fn *elevator_merged_fn;
  31         elevator_merge_req_fn *elevator_merge_req_fn;
  32
  33         elevator_next_req_fn *elevator_next_req_fn;
  34         elevator_add_req_fn *elevator_add_req_fn;
  35         elevator_remove_req_fn *elevator_remove_req_fn;
  36         elevator_requeue_req_fn *elevator_requeue_req_fn;
  37
  38         elevator_queue_empty_fn *elevator_queue_empty_fn;
  39         elevator_completed_req_fn *elevator_completed_req_fn;
  40
  41         elevator_request_list_fn *elevator_former_req_fn;
  42         elevator_request_list_fn *elevator_latter_req_fn;
  43
  44         elevator_set_req_fn *elevator_set_req_fn;
  45         elevator_put_req_fn *elevator_put_req_fn;
  46
  47         elevator_may_queue_fn *elevator_may_queue_fn;
  48
  49         elevator_init_fn *elevator_init_fn;
  50         elevator_exit_fn *elevator_exit_fn;
  51
  52         void *elevator_data;
  53
  54         struct kobject kobj;
  55         struct kobj_type *elevator_ktype;
  56         const char *elevator_name;
  57 };
  58
  59 /*
  60  * block elevator interface
  61  */
  62 extern void elv_add_request(request_queue_t *, struct request *, int, int);
  63 extern void __elv_add_request(request_queue_t *, struct request *, int, int);
  64 extern int elv_merge(request_queue_t *, struct request **, struct bio *);
  65 extern void elv_merge_requests(request_queue_t *, struct request *,
  66                                struct request *);
  67 extern void elv_merged_request(request_queue_t *, struct request *);
  68 extern void elv_remove_request(request_queue_t *, struct request *);
  69 extern void elv_requeue_request(request_queue_t *, struct request *);
  70 extern int elv_queue_empty(request_queue_t *);
  71 extern struct request *elv_next_request(struct request_queue *q);
  72 extern struct request *elv_former_request(request_queue_t *, struct request *);
  73 extern struct request *elv_latter_request(request_queue_t *, struct request *);
  74 extern int elv_register_queue(request_queue_t *q);
  75 extern void elv_unregister_queue(request_queue_t *q);
  76 extern int elv_may_queue(request_queue_t *, int);
  77 extern void elv_completed_request(request_queue_t *, struct request *);
  78 extern int elv_set_request(request_queue_t *, struct request *, int);
  79 extern void elv_put_request(request_queue_t *, struct request *);
  80
  81 /*
  82  * noop I/O scheduler. always merges, always inserts new request at tail
  83  */
  84 extern elevator_t elevator_noop;
  85
  86 /*
  87  * deadline i/o scheduler. uses request time outs to prevent indefinite
  88  * starvation
  89  */
  90 extern elevator_t iosched_deadline;
  91
  92 /*
  93  * anticipatory I/O scheduler
  94  */
  95 extern elevator_t iosched_as;
  96
  97 /*
  98  * completely fair queueing I/O scheduler
  99  */
 100 extern elevator_t iosched_cfq;
 101
 102 extern int elevator_init(request_queue_t *, elevator_t *);
 103 extern void elevator_exit(request_queue_t *);
 104 extern int elv_rq_merge_ok(struct request *, struct bio *);
 105 extern int elv_try_merge(struct request *, struct bio *);
 106 extern int elv_try_last_merge(request_queue_t *, struct bio *);
 107
 108 /*
 109  * Return values from elevator merger
 110  */
 111 #define ELEVATOR_NO_MERGE       0
 112 #define ELEVATOR_FRONT_MERGE    1
 113 #define ELEVATOR_BACK_MERGE     2
 114
 115 /*
 116  * Insertion selection
 117  */
 118 #define ELEVATOR_INSERT_FRONT   1
 119 #define ELEVATOR_INSERT_BACK    2
 120 #define ELEVATOR_INSERT_SORT    3
 121
 122 #endif