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