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 list_head **,
   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 *, struct list_head *);
  14 typedef int (elevator_queue_empty_fn) (request_queue_t *);
  15 typedef void (elevator_remove_req_fn) (request_queue_t *, struct request *);
  16 typedef struct request *(elevator_request_list_fn) (request_queue_t *, struct request *);
  17 typedef struct list_head *(elevator_get_sort_head_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
  37         elevator_queue_empty_fn *elevator_queue_empty_fn;
  38         elevator_completed_req_fn *elevator_completed_req_fn;
  39
  40         elevator_request_list_fn *elevator_former_req_fn;
  41         elevator_request_list_fn *elevator_latter_req_fn;
  42
  43         elevator_set_req_fn *elevator_set_req_fn;
  44         elevator_put_req_fn *elevator_put_req_fn;
  45
  46         elevator_may_queue_fn *elevator_may_queue_fn;
  47
  48         elevator_init_fn *elevator_init_fn;
  49         elevator_exit_fn *elevator_exit_fn;
  50
  51         void *elevator_data;
  52
  53         struct kobject kobj;
  54         struct kobj_type *elevator_ktype;
  55 };
  56
  57 /*
  58  * block elevator interface
  59  */
  60 extern void elv_add_request(request_queue_t *, struct request *, int, int);
  61 extern void __elv_add_request(request_queue_t *, struct request *, int, int);
  62 extern int elv_merge(request_queue_t *, struct list_head **, struct bio *);
  63 extern void elv_merge_requests(request_queue_t *, struct request *,
  64                                struct request *);
  65 extern void elv_merged_request(request_queue_t *, struct request *);
  66 extern void elv_remove_request(request_queue_t *, struct request *);
  67 extern int elv_queue_empty(request_queue_t *);
  68 extern struct request *elv_next_request(struct request_queue *q);
  69 extern struct request *elv_former_request(request_queue_t *, struct request *);
  70 extern struct request *elv_latter_request(request_queue_t *, struct request *);
  71 extern int elv_register_queue(request_queue_t *q);
  72 extern void elv_unregister_queue(request_queue_t *q);
  73 extern int elv_may_queue(request_queue_t *, int);
  74 extern void elv_completed_request(request_queue_t *, struct request *);
  75 extern int elv_set_request(request_queue_t *, struct request *, int);
  76 extern void elv_put_request(request_queue_t *, struct request *);
  77
  78 #define __elv_add_request_pos(q, rq, pos)       \
  79         (q)->elevator.elevator_add_req_fn((q), (rq), (pos))
  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 extern int elevator_init(request_queue_t *, elevator_t *);
  98 extern void elevator_exit(request_queue_t *);
  99 extern inline int elv_rq_merge_ok(struct request *, struct bio *);
 100 extern inline int elv_try_merge(struct request *, struct bio *);
 101 extern inline int elv_try_last_merge(request_queue_t *, struct bio *);
 102
 103 /*
 104  * Return values from elevator merger
 105  */
 106 #define ELEVATOR_NO_MERGE       0
 107 #define ELEVATOR_FRONT_MERGE    1
 108 #define ELEVATOR_BACK_MERGE     2
 109
 110 #endif