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 typedef int (elevator_merge_fn) (struct request_queue *, struct request **,
   9                                  struct bio *);
  10
  11 typedef void (elevator_merge_req_fn) (struct request_queue *, struct request *, struct request *);
  12
  13 typedef void (elevator_merged_fn) (struct request_queue *, struct request *, int);
  14
  15 typedef int (elevator_allow_merge_fn) (struct request_queue *, struct request *, struct bio *);
  16
  17 typedef void (elevator_bio_merged_fn) (struct request_queue *,
  18                                                 struct request *, struct bio *);
  19
  20 typedef int (elevator_dispatch_fn) (struct request_queue *, int);
  21
  22 typedef void (elevator_add_req_fn) (struct request_queue *, struct request *);
  23 typedef int (elevator_queue_empty_fn) (struct request_queue *);
  24 typedef struct request *(elevator_request_list_fn) (struct request_queue *, struct request *);
  25 typedef void (elevator_completed_req_fn) (struct request_queue *, struct request *);
  26 typedef int (elevator_may_queue_fn) (struct request_queue *, int);
  27
  28 typedef int (elevator_set_req_fn) (struct request_queue *, struct request *, gfp_t);
  29 typedef void (elevator_put_req_fn) (struct request *);
  30 typedef void (elevator_activate_req_fn) (struct request_queue *, struct request *);
  31 typedef void (elevator_deactivate_req_fn) (struct request_queue *, struct request *);
  32
  33 typedef void *(elevator_init_fn) (struct request_queue *);
  34 typedef void (elevator_exit_fn) (struct elevator_queue *);
  35
  36 struct elevator_ops
  37 {
  38         elevator_merge_fn *elevator_merge_fn;
  39         elevator_merged_fn *elevator_merged_fn;
  40         elevator_merge_req_fn *elevator_merge_req_fn;
  41         elevator_allow_merge_fn *elevator_allow_merge_fn;
  42         elevator_bio_merged_fn *elevator_bio_merged_fn;
  43
  44         elevator_dispatch_fn *elevator_dispatch_fn;
  45         elevator_add_req_fn *elevator_add_req_fn;
  46         elevator_activate_req_fn *elevator_activate_req_fn;
  47         elevator_deactivate_req_fn *elevator_deactivate_req_fn;
  48
  49         elevator_queue_empty_fn *elevator_queue_empty_fn;
  50         elevator_completed_req_fn *elevator_completed_req_fn;
  51
  52         elevator_request_list_fn *elevator_former_req_fn;
  53         elevator_request_list_fn *elevator_latter_req_fn;
  54
  55         elevator_set_req_fn *elevator_set_req_fn;
  56         elevator_put_req_fn *elevator_put_req_fn;
  57
  58         elevator_may_queue_fn *elevator_may_queue_fn;
  59
  60         elevator_init_fn *elevator_init_fn;
  61         elevator_exit_fn *elevator_exit_fn;
  62         void (*trim)(struct io_context *);
  63 };
  64
  65 #define ELV_NAME_MAX    (16)
  66
  67 struct elv_fs_entry {
  68         struct attribute attr;
  69         ssize_t (*show)(struct elevator_queue *, char *);
  70         ssize_t (*store)(struct elevator_queue *, const char *, size_t);
  71 };
  72
  73 /*
  74  * identifies an elevator type, such as AS or deadline
  75  */
  76 struct elevator_type
  77 {
  78         struct list_head list;
  79         struct elevator_ops ops;
  80         struct elv_fs_entry *elevator_attrs;
  81         char elevator_name[ELV_NAME_MAX];
  82         struct module *elevator_owner;
  83 };
  84
  85 /*
  86  * each queue has an elevator_queue associated with it
  87  */
  88 struct elevator_queue
  89 {
  90         struct elevator_ops *ops;
  91         void *elevator_data;
  92         struct kobject kobj;
  93         struct elevator_type *elevator_type;
  94         struct mutex sysfs_lock;
  95         struct hlist_head *hash;
  96 };
  97
  98 /*
  99  * block elevator interface
 100  */
 101 extern void elv_dispatch_sort(struct request_queue *, struct request *);
 102 extern void elv_dispatch_add_tail(struct request_queue *, struct request *);
 103 extern void elv_add_request(struct request_queue *, struct request *, int, int);
 104 extern void __elv_add_request(struct request_queue *, struct request *, int, int);
 105 extern void elv_insert(struct request_queue *, struct request *, int);
 106 extern int elv_merge(struct request_queue *, struct request **, struct bio *);
 107 extern void elv_merge_requests(struct request_queue *, struct request *,
 108                                struct request *);
 109 extern void elv_merged_request(struct request_queue *, struct request *, int);
 110 extern void elv_bio_merged(struct request_queue *q, struct request *,
 111                                 struct bio *);
 112 extern void elv_requeue_request(struct request_queue *, struct request *);
 113 extern int elv_queue_empty(struct request_queue *);
 114 extern struct request *elv_former_request(struct request_queue *, struct request *);
 115 extern struct request *elv_latter_request(struct request_queue *, struct request *);
 116 extern int elv_register_queue(struct request_queue *q);
 117 extern void elv_unregister_queue(struct request_queue *q);
 118 extern int elv_may_queue(struct request_queue *, int);
 119 extern void elv_abort_queue(struct request_queue *);
 120 extern void elv_completed_request(struct request_queue *, struct request *);
 121 extern int elv_set_request(struct request_queue *, struct request *, gfp_t);
 122 extern void elv_put_request(struct request_queue *, struct request *);
 123 extern void elv_drain_elevator(struct request_queue *);
 124
 125 /*
 126  * io scheduler registration
 127  */
 128 extern void elv_register(struct elevator_type *);
 129 extern void elv_unregister(struct elevator_type *);
 130
 131 /*
 132  * io scheduler sysfs switching
 133  */
 134 extern ssize_t elv_iosched_show(struct request_queue *, char *);
 135 extern ssize_t elv_iosched_store(struct request_queue *, const char *, size_t);
 136
 137 extern int elevator_init(struct request_queue *, char *);
 138 extern void elevator_exit(struct elevator_queue *);
 139 extern int elevator_change(struct request_queue *, const char *);
 140 extern int elv_rq_merge_ok(struct request *, struct bio *);
 141
 142 /*
 143  * Helper functions.
 144  */
 145 extern struct request *elv_rb_former_request(struct request_queue *, struct request *);
 146 extern struct request *elv_rb_latter_request(struct request_queue *, struct request *);
 147
 148 /*
 149  * rb support functions.
 150  */
 151 extern struct request *elv_rb_add(struct rb_root *, struct request *);
 152 extern void elv_rb_del(struct rb_root *, struct request *);
 153 extern struct request *elv_rb_find(struct rb_root *, sector_t);
 154
 155 /*
 156  * Return values from elevator merger
 157  */
 158 #define ELEVATOR_NO_MERGE       0
 159 #define ELEVATOR_FRONT_MERGE    1
 160 #define ELEVATOR_BACK_MERGE     2
 161
 162 /*
 163  * Insertion selection
 164  */
 165 #define ELEVATOR_INSERT_FRONT   1
 166 #define ELEVATOR_INSERT_BACK    2
 167 #define ELEVATOR_INSERT_SORT    3
 168 #define ELEVATOR_INSERT_REQUEUE 4
 169
 170 /*
 171  * return values from elevator_may_queue_fn
 172  */
 173 enum {
 174         ELV_MQUEUE_MAY,
 175         ELV_MQUEUE_NO,
 176         ELV_MQUEUE_MUST,
 177 };
 178
 179 #define rq_end_sector(rq)       (blk_rq_pos(rq) + blk_rq_sectors(rq))
 180 #define rb_entry_rq(node)       rb_entry((node), struct request, rb_node)
 181
 182 /*
 183  * Hack to reuse the csd.list list_head as the fifo time holder while
 184  * the request is in the io scheduler. Saves an unsigned long in rq.
 185  */
 186 #define rq_fifo_time(rq)        ((unsigned long) (rq)->csd.list.next)
 187 #define rq_set_fifo_time(rq,exp)        ((rq)->csd.list.next = (void *) (exp))
 188 #define rq_entry_fifo(ptr)      list_entry((ptr), struct request, queuelist)
 189 #define rq_fifo_clear(rq)       do {            \
 190         list_del_init(&(rq)->queuelist);        \
 191         INIT_LIST_HEAD(&(rq)->csd.list);        \
 192         } while (0)
 193
 194 /*
 195  * io context count accounting
 196  */
 197 #define elv_ioc_count_mod(name, __val)                          \
 198         do {                                                    \
 199                 preempt_disable();                              \
 200                 __get_cpu_var(name) += (__val);                 \
 201                 preempt_enable();                               \
 202         } while (0)
 203
 204 #define elv_ioc_count_inc(name) elv_ioc_count_mod(name, 1)
 205 #define elv_ioc_count_dec(name) elv_ioc_count_mod(name, -1)
 206
 207 #define elv_ioc_count_read(name)                                \
 208 ({                                                              \
 209         unsigned long __val = 0;                                \
 210         int __cpu;                                              \
 211         smp_wmb();                                              \
 212         for_each_possible_cpu(__cpu)                            \
 213                 __val += per_cpu(name, __cpu);                  \
 214         __val;                                                  \
 215 })
 216
 217 #endif /* CONFIG_BLOCK */
 218 #endif