LXR linux/include/linux/elevator.h

   1#ifndef _LINUX_ELEVATOR_H
   2#define _LINUX_ELEVATOR_H
   3
   4#include <linux/percpu.h>
   5#include <linux/hashtable.h>
   6
   7#ifdef CONFIG_BLOCK
   8
   9struct io_cq;
  10
  11typedef int (elevator_merge_fn) (struct request_queue *, struct request **,
  12                                 struct bio *);
  13
  14typedef void (elevator_merge_req_fn) (struct request_queue *, struct request *, struct request *);
  15
  16typedef void (elevator_merged_fn) (struct request_queue *, struct request *, int);
  17
  18typedef int (elevator_allow_merge_fn) (struct request_queue *, struct request *, struct bio *);
  19
  20typedef void (elevator_bio_merged_fn) (struct request_queue *,
  21                                                struct request *, struct bio *);
  22
  23typedef int (elevator_dispatch_fn) (struct request_queue *, int);
  24
  25typedef void (elevator_add_req_fn) (struct request_queue *, struct request *);
  26typedef struct request *(elevator_request_list_fn) (struct request_queue *, struct request *);
  27typedef void (elevator_completed_req_fn) (struct request_queue *, struct request *);
  28typedef int (elevator_may_queue_fn) (struct request_queue *, int);
  29
  30typedef void (elevator_init_icq_fn) (struct io_cq *);
  31typedef void (elevator_exit_icq_fn) (struct io_cq *);
  32typedef int (elevator_set_req_fn) (struct request_queue *, struct request *,
  33                                   struct bio *, gfp_t);
  34typedef void (elevator_put_req_fn) (struct request *);
  35typedef void (elevator_activate_req_fn) (struct request_queue *, struct request *);
  36typedef void (elevator_deactivate_req_fn) (struct request_queue *, struct request *);
  37
  38typedef int (elevator_init_fn) (struct request_queue *);
  39typedef void (elevator_exit_fn) (struct elevator_queue *);
  40
  41struct elevator_ops
  42{
  43        elevator_merge_fn *elevator_merge_fn;
  44        elevator_merged_fn *elevator_merged_fn;
  45        elevator_merge_req_fn *elevator_merge_req_fn;
  46        elevator_allow_merge_fn *elevator_allow_merge_fn;
  47        elevator_bio_merged_fn *elevator_bio_merged_fn;
  48
  49        elevator_dispatch_fn *elevator_dispatch_fn;
  50        elevator_add_req_fn *elevator_add_req_fn;
  51        elevator_activate_req_fn *elevator_activate_req_fn;
  52        elevator_deactivate_req_fn *elevator_deactivate_req_fn;
  53
  54        elevator_completed_req_fn *elevator_completed_req_fn;
  55
  56        elevator_request_list_fn *elevator_former_req_fn;
  57        elevator_request_list_fn *elevator_latter_req_fn;
  58
  59        elevator_init_icq_fn *elevator_init_icq_fn;     /* see iocontext.h */
  60        elevator_exit_icq_fn *elevator_exit_icq_fn;     /* ditto */
  61
  62        elevator_set_req_fn *elevator_set_req_fn;
  63        elevator_put_req_fn *elevator_put_req_fn;
  64
  65        elevator_may_queue_fn *elevator_may_queue_fn;
  66
  67        elevator_init_fn *elevator_init_fn;
  68        elevator_exit_fn *elevator_exit_fn;
  69};
  70
  71#define ELV_NAME_MAX    (16)
  72
  73struct elv_fs_entry {
  74        struct attribute attr;
  75        ssize_t (*show)(struct elevator_queue *, char *);
  76        ssize_t (*store)(struct elevator_queue *, const char *, size_t);
  77};
  78
  79/*
  80 * identifies an elevator type, such as AS or deadline
  81 */
  82struct elevator_type
  83{
  84        /* managed by elevator core */
  85        struct kmem_cache *icq_cache;
  86
  87        /* fields provided by elevator implementation */
  88        struct elevator_ops ops;
  89        size_t icq_size;        /* see iocontext.h */
  90        size_t icq_align;       /* ditto */
  91        struct elv_fs_entry *elevator_attrs;
  92        char elevator_name[ELV_NAME_MAX];
  93        struct module *elevator_owner;
  94
  95        /* managed by elevator core */
  96        char icq_cache_name[ELV_NAME_MAX + 5];  /* elvname + "_io_cq" */
  97        struct list_head list;
  98};
  99
 100#define ELV_HASH_BITS 6
 101
 102/*
 103 * each queue has an elevator_queue associated with it
 104 */
 105struct elevator_queue
 106{
 107        struct elevator_type *type;
 108        void *elevator_data;
 109        struct kobject kobj;
 110        struct mutex sysfs_lock;
 111        unsigned int registered:1;
 112        DECLARE_HASHTABLE(hash, ELV_HASH_BITS);
 113};
 114
 115/*
 116 * block elevator interface
 117 */
 118extern void elv_dispatch_sort(struct request_queue *, struct request *);
 119extern void elv_dispatch_add_tail(struct request_queue *, struct request *);
 120extern void elv_add_request(struct request_queue *, struct request *, int);
 121extern void __elv_add_request(struct request_queue *, struct request *, int);
 122extern int elv_merge(struct request_queue *, struct request **, struct bio *);
 123extern void elv_merge_requests(struct request_queue *, struct request *,
 124                               struct request *);
 125extern void elv_merged_request(struct request_queue *, struct request *, int);
 126extern void elv_bio_merged(struct request_queue *q, struct request *,
 127                                struct bio *);
 128extern void elv_requeue_request(struct request_queue *, struct request *);
 129extern struct request *elv_former_request(struct request_queue *, struct request *);
 130extern struct request *elv_latter_request(struct request_queue *, struct request *);
 131extern int elv_register_queue(struct request_queue *q);
 132extern void elv_unregister_queue(struct request_queue *q);
 133extern int elv_may_queue(struct request_queue *, int);
 134extern void elv_abort_queue(struct request_queue *);
 135extern void elv_completed_request(struct request_queue *, struct request *);
 136extern int elv_set_request(struct request_queue *q, struct request *rq,
 137                           struct bio *bio, gfp_t gfp_mask);
 138extern void elv_put_request(struct request_queue *, struct request *);
 139extern void elv_drain_elevator(struct request_queue *);
 140
 141/*
 142 * io scheduler registration
 143 */
 144extern void __init load_default_elevator_module(void);
 145extern int elv_register(struct elevator_type *);
 146extern void elv_unregister(struct elevator_type *);
 147
 148/*
 149 * io scheduler sysfs switching
 150 */
 151extern ssize_t elv_iosched_show(struct request_queue *, char *);
 152extern ssize_t elv_iosched_store(struct request_queue *, const char *, size_t);
 153
 154extern int elevator_init(struct request_queue *, char *);
 155extern void elevator_exit(struct elevator_queue *);
 156extern int elevator_change(struct request_queue *, const char *);
 157extern bool elv_rq_merge_ok(struct request *, struct bio *);
 158
 159/*
 160 * Helper functions.
 161 */
 162extern struct request *elv_rb_former_request(struct request_queue *, struct request *);
 163extern struct request *elv_rb_latter_request(struct request_queue *, struct request *);
 164
 165/*
 166 * rb support functions.
 167 */
 168extern void elv_rb_add(struct rb_root *, struct request *);
 169extern void elv_rb_del(struct rb_root *, struct request *);
 170extern struct request *elv_rb_find(struct rb_root *, sector_t);
 171
 172/*
 173 * Return values from elevator merger
 174 */
 175#define ELEVATOR_NO_MERGE       0
 176#define ELEVATOR_FRONT_MERGE    1
 177#define ELEVATOR_BACK_MERGE     2
 178
 179/*
 180 * Insertion selection
 181 */
 182#define ELEVATOR_INSERT_FRONT   1
 183#define ELEVATOR_INSERT_BACK    2
 184#define ELEVATOR_INSERT_SORT    3
 185#define ELEVATOR_INSERT_REQUEUE 4
 186#define ELEVATOR_INSERT_FLUSH   5
 187#define ELEVATOR_INSERT_SORT_MERGE      6
 188
 189/*
 190 * return values from elevator_may_queue_fn
 191 */
 192enum {
 193        ELV_MQUEUE_MAY,
 194        ELV_MQUEUE_NO,
 195        ELV_MQUEUE_MUST,
 196};
 197
 198#define rq_end_sector(rq)       (blk_rq_pos(rq) + blk_rq_sectors(rq))
 199#define rb_entry_rq(node)       rb_entry((node), struct request, rb_node)
 200
 201/*
 202 * Hack to reuse the csd.list list_head as the fifo time holder while
 203 * the request is in the io scheduler. Saves an unsigned long in rq.
 204 */
 205#define rq_fifo_time(rq)        ((unsigned long) (rq)->csd.list.next)
 206#define rq_set_fifo_time(rq,exp)        ((rq)->csd.list.next = (void *) (exp))
 207#define rq_entry_fifo(ptr)      list_entry((ptr), struct request, queuelist)
 208#define rq_fifo_clear(rq)       do {            \
 209        list_del_init(&(rq)->queuelist);        \
 210        INIT_LIST_HEAD(&(rq)->csd.list);        \
 211        } while (0)
 212
 213#else /* CONFIG_BLOCK */
 214
 215static inline void load_default_elevator_module(void) { }
 216
 217#endif /* CONFIG_BLOCK */
 218#endif
 219