include/linux/elevator.h

   1 #ifndef _LINUX_ELEVATOR_H
   2 #define _LINUX_ELEVATOR_H
   3
   4 #include <linux/percpu.h>
   5
   6 #ifdef CONFIG_BLOCK
   7
   8 struct io_cq;
   9
  10 typedef int (elevator_merge_fn) (struct request_queue *, struct request **,
  11                                  struct bio *);
  12
  13 typedef void (elevator_merge_req_fn) (struct request_queue *, struct request *, struct request *);
  14
  15 typedef void (elevator_merged_fn) (struct request_queue *, struct request *, int);
  16
  17 typedef int (elevator_allow_merge_fn) (struct request_queue *, struct request *, struct bio *);
  18
  19 typedef void (elevator_bio_merged_fn) (struct request_queue *,
  20                                                 struct request *, struct bio *);
  21
  22 typedef int (elevator_dispatch_fn) (struct request_queue *, int);
  23
  24 typedef void (elevator_add_req_fn) (struct request_queue *, struct request *);
  25 typedef struct request *(elevator_request_list_fn) (struct request_queue *, struct request *);
  26 typedef void (elevator_completed_req_fn) (struct request_queue *, struct request *);
  27 typedef int (elevator_may_queue_fn) (struct request_queue *, int);
  28
  29 typedef void (elevator_init_icq_fn) (struct io_cq *);
  30 typedef void (elevator_exit_icq_fn) (struct io_cq *);
  31 typedef int (elevator_set_req_fn) (struct request_queue *, struct request *, gfp_t);
  32 typedef void (elevator_put_req_fn) (struct request *);
  33 typedef void (elevator_activate_req_fn) (struct request_queue *, struct request *);
  34 typedef void (elevator_deactivate_req_fn) (struct request_queue *, struct request *);
  35
  36 typedef void *(elevator_init_fn) (struct request_queue *);
  37 typedef void (elevator_exit_fn) (struct elevator_queue *);
  38
  39 struct elevator_ops
  40 {
  41         elevator_merge_fn *elevator_merge_fn;
  42         elevator_merged_fn *elevator_merged_fn;
  43         elevator_merge_req_fn *elevator_merge_req_fn;
  44         elevator_allow_merge_fn *elevator_allow_merge_fn;
  45         elevator_bio_merged_fn *elevator_bio_merged_fn;
  46
  47         elevator_dispatch_fn *elevator_dispatch_fn;
  48         elevator_add_req_fn *elevator_add_req_fn;
  49         elevator_activate_req_fn *elevator_activate_req_fn;
  50         elevator_deactivate_req_fn *elevator_deactivate_req_fn;
  51
  52         elevator_completed_req_fn *elevator_completed_req_fn;
  53
  54         elevator_request_list_fn *elevator_former_req_fn;
  55         elevator_request_list_fn *elevator_latter_req_fn;
  56
  57         elevator_init_icq_fn *elevator_init_icq_fn;     /* see iocontext.h */
  58         elevator_exit_icq_fn *elevator_exit_icq_fn;     /* ditto */
  59
  60         elevator_set_req_fn *elevator_set_req_fn;
  61         elevator_put_req_fn *elevator_put_req_fn;
  62
  63         elevator_may_queue_fn *elevator_may_queue_fn;
  64
  65         elevator_init_fn *elevator_init_fn;
  66         elevator_exit_fn *elevator_exit_fn;
  67 };
  68
  69 #define ELV_NAME_MAX    (16)
  70
  71 struct elv_fs_entry {
  72         struct attribute attr;
  73         ssize_t (*show)(struct elevator_queue *, char *);
  74         ssize_t (*store)(struct elevator_queue *, const char *, size_t);
  75 };
  76
  77 /*
  78  * identifies an elevator type, such as AS or deadline
  79  */
  80 struct elevator_type
  81 {
  82         /* managed by elevator core */
  83         struct kmem_cache *icq_cache;
  84
  85         /* fields provided by elevator implementation */
  86         struct elevator_ops ops;
  87         size_t icq_size;        /* see iocontext.h */
  88         size_t icq_align;       /* ditto */
  89         struct elv_fs_entry *elevator_attrs;
  90         char elevator_name[ELV_NAME_MAX];
  91         struct module *elevator_owner;
  92
  93         /* managed by elevator core */
  94         char icq_cache_name[ELV_NAME_MAX + 5];  /* elvname + "_io_cq" */
  95         struct list_head list;
  96 };
  97
  98 /*
  99  * each queue has an elevator_queue associated with it
 100  */
 101 struct elevator_queue
 102 {
 103         struct elevator_type *type;
 104         void *elevator_data;
 105         struct kobject kobj;
 106         struct mutex sysfs_lock;
 107         struct hlist_head *hash;
 108         unsigned int registered:1;
 109 };
 110
 111 /*
 112  * block elevator interface
 113  */
 114 extern void elv_dispatch_sort(struct request_queue *, struct request *);
 115 extern void elv_dispatch_add_tail(struct request_queue *, struct request *);
 116 extern void elv_add_request(struct request_queue *, struct request *, int);
 117 extern void __elv_add_request(struct request_queue *, struct request *, int);
 118 extern int elv_merge(struct request_queue *, struct request **, struct bio *);
 119 extern void elv_merge_requests(struct request_queue *, struct request *,
 120                                struct request *);
 121 extern void elv_merged_request(struct request_queue *, struct request *, int);
 122 extern void elv_bio_merged(struct request_queue *q, struct request *,
 123                                 struct bio *);
 124 extern void elv_requeue_request(struct request_queue *, struct request *);
 125 extern struct request *elv_former_request(struct request_queue *, struct request *);
 126 extern struct request *elv_latter_request(struct request_queue *, struct request *);
 127 extern int elv_register_queue(struct request_queue *q);
 128 extern void elv_unregister_queue(struct request_queue *q);
 129 extern int elv_may_queue(struct request_queue *, int);
 130 extern void elv_abort_queue(struct request_queue *);
 131 extern void elv_completed_request(struct request_queue *, struct request *);
 132 extern int elv_set_request(struct request_queue *, struct request *, gfp_t);
 133 extern void elv_put_request(struct request_queue *, struct request *);
 134 extern void elv_drain_elevator(struct request_queue *);
 135
 136 /*
 137  * io scheduler registration
 138  */
 139 extern int elv_register(struct elevator_type *);
 140 extern void elv_unregister(struct elevator_type *);
 141
 142 /*
 143  * io scheduler sysfs switching
 144  */
 145 extern ssize_t elv_iosched_show(struct request_queue *, char *);
 146 extern ssize_t elv_iosched_store(struct request_queue *, const char *, size_t);
 147
 148 extern int elevator_init(struct request_queue *, char *);
 149 extern void elevator_exit(struct elevator_queue *);
 150 extern int elevator_change(struct request_queue *, const char *);
 151 extern bool elv_rq_merge_ok(struct request *, struct bio *);
 152
 153 /*
 154  * Helper functions.
 155  */
 156 extern struct request *elv_rb_former_request(struct request_queue *, struct request *);
 157 extern struct request *elv_rb_latter_request(struct request_queue *, struct request *);
 158
 159 /*
 160  * rb support functions.
 161  */
 162 extern void elv_rb_add(struct rb_root *, struct request *);
 163 extern void elv_rb_del(struct rb_root *, struct request *);
 164 extern struct request *elv_rb_find(struct rb_root *, sector_t);
 165
 166 /*
 167  * Return values from elevator merger
 168  */
 169 #define ELEVATOR_NO_MERGE       0
 170 #define ELEVATOR_FRONT_MERGE    1
 171 #define ELEVATOR_BACK_MERGE     2
 172
 173 /*
 174  * Insertion selection
 175  */
 176 #define ELEVATOR_INSERT_FRONT   1
 177 #define ELEVATOR_INSERT_BACK    2
 178 #define ELEVATOR_INSERT_SORT    3
 179 #define ELEVATOR_INSERT_REQUEUE 4
 180 #define ELEVATOR_INSERT_FLUSH   5
 181 #define ELEVATOR_INSERT_SORT_MERGE      6
 182
 183 /*
 184  * return values from elevator_may_queue_fn
 185  */
 186 enum {
 187         ELV_MQUEUE_MAY,
 188         ELV_MQUEUE_NO,
 189         ELV_MQUEUE_MUST,
 190 };
 191
 192 #define rq_end_sector(rq)       (blk_rq_pos(rq) + blk_rq_sectors(rq))
 193 #define rb_entry_rq(node)       rb_entry((node), struct request, rb_node)
 194
 195 /*
 196  * Hack to reuse the csd.list list_head as the fifo time holder while
 197  * the request is in the io scheduler. Saves an unsigned long in rq.
 198  */
 199 #define rq_fifo_time(rq)        ((unsigned long) (rq)->csd.list.next)
 200 #define rq_set_fifo_time(rq,exp)        ((rq)->csd.list.next = (void *) (exp))
 201 #define rq_entry_fifo(ptr)      list_entry((ptr), struct request, queuelist)
 202 #define rq_fifo_clear(rq)       do {            \
 203         list_del_init(&(rq)->queuelist);        \
 204         INIT_LIST_HEAD(&(rq)->csd.list);        \
 205         } while (0)
 206
 207 #endif /* CONFIG_BLOCK */
 208 #endif