LXR linux/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
   8typedef int (elevator_merge_fn) (struct request_queue *, struct request **,
   9                                 struct bio *);
  10
  11typedef void (elevator_merge_req_fn) (struct request_queue *, struct request *, struct request *);
  12
  13typedef void (elevator_merged_fn) (struct request_queue *, struct request *, int);
  14
  15typedef int (elevator_allow_merge_fn) (struct request_queue *, struct request *, struct bio *);
  16
  17typedef void (elevator_bio_merged_fn) (struct request_queue *,
  18                                                struct request *, struct bio *);
  19
  20typedef int (elevator_dispatch_fn) (struct request_queue *, int);
  21
  22typedef void (elevator_add_req_fn) (struct request_queue *, struct request *);
  23typedef int (elevator_queue_empty_fn) (struct request_queue *);
  24typedef struct request *(elevator_request_list_fn) (struct request_queue *, struct request *);
  25typedef void (elevator_completed_req_fn) (struct request_queue *, struct request *);
  26typedef int (elevator_may_queue_fn) (struct request_queue *, int);
  27
  28typedef int (elevator_set_req_fn) (struct request_queue *, struct request *, gfp_t);
  29typedef void (elevator_put_req_fn) (struct request *);
  30typedef void (elevator_activate_req_fn) (struct request_queue *, struct request *);
  31typedef void (elevator_deactivate_req_fn) (struct request_queue *, struct request *);
  32
  33typedef void *(elevator_init_fn) (struct request_queue *);
  34typedef void (elevator_exit_fn) (struct elevator_queue *);
  35
  36struct 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
  67struct 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 */
  76struct 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 */
  88struct 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 */
 101extern void elv_dispatch_sort(struct request_queue *, struct request *);
 102extern void elv_dispatch_add_tail(struct request_queue *, struct request *);
 103extern void elv_add_request(struct request_queue *, struct request *, int, int);
 104extern void __elv_add_request(struct request_queue *, struct request *, int, int);
 105extern void elv_insert(struct request_queue *, struct request *, int);
 106extern int elv_merge(struct request_queue *, struct request **, struct bio *);
 107extern void elv_merge_requests(struct request_queue *, struct request *,
 108                               struct request *);
 109extern void elv_merged_request(struct request_queue *, struct request *, int);
 110extern void elv_bio_merged(struct request_queue *q, struct request *,
 111                                struct bio *);
 112extern void elv_requeue_request(struct request_queue *, struct request *);
 113extern int elv_queue_empty(struct request_queue *);
 114extern struct request *elv_former_request(struct request_queue *, struct request *);
 115extern struct request *elv_latter_request(struct request_queue *, struct request *);
 116extern int elv_register_queue(struct request_queue *q);
 117extern void elv_unregister_queue(struct request_queue *q);
 118extern int elv_may_queue(struct request_queue *, int);
 119extern void elv_abort_queue(struct request_queue *);
 120extern void elv_completed_request(struct request_queue *, struct request *);
 121extern int elv_set_request(struct request_queue *, struct request *, gfp_t);
 122extern void elv_put_request(struct request_queue *, struct request *);
 123extern void elv_drain_elevator(struct request_queue *);
 124
 125/*
 126 * io scheduler registration
 127 */
 128extern void elv_register(struct elevator_type *);
 129extern void elv_unregister(struct elevator_type *);
 130
 131/*
 132 * io scheduler sysfs switching
 133 */
 134extern ssize_t elv_iosched_show(struct request_queue *, char *);
 135extern ssize_t elv_iosched_store(struct request_queue *, const char *, size_t);
 136
 137extern int elevator_init(struct request_queue *, char *);
 138extern void elevator_exit(struct elevator_queue *);
 139extern int elv_rq_merge_ok(struct request *, struct bio *);
 140
 141/*
 142 * Helper functions.
 143 */
 144extern struct request *elv_rb_former_request(struct request_queue *, struct request *);
 145extern struct request *elv_rb_latter_request(struct request_queue *, struct request *);
 146
 147/*
 148 * rb support functions.
 149 */
 150extern struct request *elv_rb_add(struct rb_root *, struct request *);
 151extern void elv_rb_del(struct rb_root *, struct request *);
 152extern struct request *elv_rb_find(struct rb_root *, sector_t);
 153
 154/*
 155 * Return values from elevator merger
 156 */
 157#define ELEVATOR_NO_MERGE       0
 158#define ELEVATOR_FRONT_MERGE    1
 159#define ELEVATOR_BACK_MERGE     2
 160
 161/*
 162 * Insertion selection
 163 */
 164#define ELEVATOR_INSERT_FRONT   1
 165#define ELEVATOR_INSERT_BACK    2
 166#define ELEVATOR_INSERT_SORT    3
 167#define ELEVATOR_INSERT_REQUEUE 4
 168
 169/*
 170 * return values from elevator_may_queue_fn
 171 */
 172enum {
 173        ELV_MQUEUE_MAY,
 174        ELV_MQUEUE_NO,
 175        ELV_MQUEUE_MUST,
 176};
 177
 178#define rq_end_sector(rq)       (blk_rq_pos(rq) + blk_rq_sectors(rq))
 179#define rb_entry_rq(node)       rb_entry((node), struct request, rb_node)
 180
 181/*
 182 * Hack to reuse the csd.list list_head as the fifo time holder while
 183 * the request is in the io scheduler. Saves an unsigned long in rq.
 184 */
 185#define rq_fifo_time(rq)        ((unsigned long) (rq)->csd.list.next)
 186#define rq_set_fifo_time(rq,exp)        ((rq)->csd.list.next = (void *) (exp))
 187#define rq_entry_fifo(ptr)      list_entry((ptr), struct request, queuelist)
 188#define rq_fifo_clear(rq)       do {            \
 189        list_del_init(&(rq)->queuelist);        \
 190        INIT_LIST_HEAD(&(rq)->csd.list);        \
 191        } while (0)
 192
 193/*
 194 * io context count accounting
 195 */
 196#define elv_ioc_count_mod(name, __val)                          \
 197        do {                                                    \
 198                preempt_disable();                              \
 199                __get_cpu_var(name) += (__val);                 \
 200                preempt_enable();                               \
 201        } while (0)
 202
 203#define elv_ioc_count_inc(name) elv_ioc_count_mod(name, 1)
 204#define elv_ioc_count_dec(name) elv_ioc_count_mod(name, -1)
 205
 206#define elv_ioc_count_read(name)                                \
 207({                                                              \
 208        unsigned long __val = 0;                                \
 209        int __cpu;                                              \
 210        smp_wmb();                                              \
 211        for_each_possible_cpu(__cpu)                            \
 212                __val += per_cpu(name, __cpu);                  \
 213        __val;                                                  \
 214})
 215
 216#endif /* CONFIG_BLOCK */
 217#endif
 218