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;
  10struct elevator_type;
  11
  12typedef int (elevator_merge_fn) (struct request_queue *, struct request **,
  13                                 struct bio *);
  14
  15typedef void (elevator_merge_req_fn) (struct request_queue *, struct request *, struct request *);
  16
  17typedef void (elevator_merged_fn) (struct request_queue *, struct request *, int);
  18
  19typedef int (elevator_allow_merge_fn) (struct request_queue *, struct request *, struct bio *);
  20
  21typedef void (elevator_bio_merged_fn) (struct request_queue *,
  22                                                struct request *, struct bio *);
  23
  24typedef int (elevator_dispatch_fn) (struct request_queue *, int);
  25
  26typedef void (elevator_add_req_fn) (struct request_queue *, struct request *);
  27typedef struct request *(elevator_request_list_fn) (struct request_queue *, struct request *);
  28typedef void (elevator_completed_req_fn) (struct request_queue *, struct request *);
  29typedef int (elevator_may_queue_fn) (struct request_queue *, int);
  30
  31typedef void (elevator_init_icq_fn) (struct io_cq *);
  32typedef void (elevator_exit_icq_fn) (struct io_cq *);
  33typedef int (elevator_set_req_fn) (struct request_queue *, struct request *,
  34                                   struct bio *, gfp_t);
  35typedef void (elevator_put_req_fn) (struct request *);
  36typedef void (elevator_activate_req_fn) (struct request_queue *, struct request *);
  37typedef void (elevator_deactivate_req_fn) (struct request_queue *, struct request *);
  38
  39typedef int (elevator_init_fn) (struct request_queue *,
  40                                struct elevator_type *e);
  41typedef void (elevator_exit_fn) (struct elevator_queue *);
  42
  43struct elevator_ops
  44{
  45        elevator_merge_fn *elevator_merge_fn;
  46        elevator_merged_fn *elevator_merged_fn;
  47        elevator_merge_req_fn *elevator_merge_req_fn;
  48        elevator_allow_merge_fn *elevator_allow_merge_fn;
  49        elevator_bio_merged_fn *elevator_bio_merged_fn;
  50
  51        elevator_dispatch_fn *elevator_dispatch_fn;
  52        elevator_add_req_fn *elevator_add_req_fn;
  53        elevator_activate_req_fn *elevator_activate_req_fn;
  54        elevator_deactivate_req_fn *elevator_deactivate_req_fn;
  55
  56        elevator_completed_req_fn *elevator_completed_req_fn;
  57
  58        elevator_request_list_fn *elevator_former_req_fn;
  59        elevator_request_list_fn *elevator_latter_req_fn;
  60
  61        elevator_init_icq_fn *elevator_init_icq_fn;     /* see iocontext.h */
  62        elevator_exit_icq_fn *elevator_exit_icq_fn;     /* ditto */
  63
  64        elevator_set_req_fn *elevator_set_req_fn;
  65        elevator_put_req_fn *elevator_put_req_fn;
  66
  67        elevator_may_queue_fn *elevator_may_queue_fn;
  68
  69        elevator_init_fn *elevator_init_fn;
  70        elevator_exit_fn *elevator_exit_fn;
  71};
  72
  73#define ELV_NAME_MAX    (16)
  74
  75struct elv_fs_entry {
  76        struct attribute attr;
  77        ssize_t (*show)(struct elevator_queue *, char *);
  78        ssize_t (*store)(struct elevator_queue *, const char *, size_t);
  79};
  80
  81/*
  82 * identifies an elevator type, such as AS or deadline
  83 */
  84struct elevator_type
  85{
  86        /* managed by elevator core */
  87        struct kmem_cache *icq_cache;
  88
  89        /* fields provided by elevator implementation */
  90        struct elevator_ops ops;
  91        size_t icq_size;        /* see iocontext.h */
  92        size_t icq_align;       /* ditto */
  93        struct elv_fs_entry *elevator_attrs;
  94        char elevator_name[ELV_NAME_MAX];
  95        struct module *elevator_owner;
  96
  97        /* managed by elevator core */
  98        char icq_cache_name[ELV_NAME_MAX + 5];  /* elvname + "_io_cq" */
  99        struct list_head list;
 100};
 101
 102#define ELV_HASH_BITS 6
 103
 104/*
 105 * each queue has an elevator_queue associated with it
 106 */
 107struct elevator_queue
 108{
 109        struct elevator_type *type;
 110        void *elevator_data;
 111        struct kobject kobj;
 112        struct mutex sysfs_lock;
 113        unsigned int registered:1;
 114        DECLARE_HASHTABLE(hash, ELV_HASH_BITS);
 115};
 116
 117/*
 118 * block elevator interface
 119 */
 120extern void elv_dispatch_sort(struct request_queue *, struct request *);
 121extern void elv_dispatch_add_tail(struct request_queue *, struct request *);
 122extern void elv_add_request(struct request_queue *, struct request *, int);
 123extern void __elv_add_request(struct request_queue *, struct request *, int);
 124extern int elv_merge(struct request_queue *, struct request **, struct bio *);
 125extern void elv_merge_requests(struct request_queue *, struct request *,
 126                               struct request *);
 127extern void elv_merged_request(struct request_queue *, struct request *, int);
 128extern void elv_bio_merged(struct request_queue *q, struct request *,
 129                                struct bio *);
 130extern void elv_requeue_request(struct request_queue *, struct request *);
 131extern struct request *elv_former_request(struct request_queue *, struct request *);
 132extern struct request *elv_latter_request(struct request_queue *, struct request *);
 133extern int elv_register_queue(struct request_queue *q);
 134extern void elv_unregister_queue(struct request_queue *q);
 135extern int elv_may_queue(struct request_queue *, int);
 136extern void elv_abort_queue(struct request_queue *);
 137extern void elv_completed_request(struct request_queue *, struct request *);
 138extern int elv_set_request(struct request_queue *q, struct request *rq,
 139                           struct bio *bio, gfp_t gfp_mask);
 140extern void elv_put_request(struct request_queue *, struct request *);
 141extern void elv_drain_elevator(struct request_queue *);
 142
 143/*
 144 * io scheduler registration
 145 */
 146extern void __init load_default_elevator_module(void);
 147extern int elv_register(struct elevator_type *);
 148extern void elv_unregister(struct elevator_type *);
 149
 150/*
 151 * io scheduler sysfs switching
 152 */
 153extern ssize_t elv_iosched_show(struct request_queue *, char *);
 154extern ssize_t elv_iosched_store(struct request_queue *, const char *, size_t);
 155
 156extern int elevator_init(struct request_queue *, char *);
 157extern void elevator_exit(struct elevator_queue *);
 158extern int elevator_change(struct request_queue *, const char *);
 159extern bool elv_rq_merge_ok(struct request *, struct bio *);
 160extern struct elevator_queue *elevator_alloc(struct request_queue *,
 161                                        struct elevator_type *);
 162
 163/*
 164 * Helper functions.
 165 */
 166extern struct request *elv_rb_former_request(struct request_queue *, struct request *);
 167extern struct request *elv_rb_latter_request(struct request_queue *, struct request *);
 168
 169/*
 170 * rb support functions.
 171 */
 172extern void elv_rb_add(struct rb_root *, struct request *);
 173extern void elv_rb_del(struct rb_root *, struct request *);
 174extern struct request *elv_rb_find(struct rb_root *, sector_t);
 175
 176/*
 177 * Return values from elevator merger
 178 */
 179#define ELEVATOR_NO_MERGE       0
 180#define ELEVATOR_FRONT_MERGE    1
 181#define ELEVATOR_BACK_MERGE     2
 182
 183/*
 184 * Insertion selection
 185 */
 186#define ELEVATOR_INSERT_FRONT   1
 187#define ELEVATOR_INSERT_BACK    2
 188#define ELEVATOR_INSERT_SORT    3
 189#define ELEVATOR_INSERT_REQUEUE 4
 190#define ELEVATOR_INSERT_FLUSH   5
 191#define ELEVATOR_INSERT_SORT_MERGE      6
 192
 193/*
 194 * return values from elevator_may_queue_fn
 195 */
 196enum {
 197        ELV_MQUEUE_MAY,
 198        ELV_MQUEUE_NO,
 199        ELV_MQUEUE_MUST,
 200};
 201
 202#define rq_end_sector(rq)       (blk_rq_pos(rq) + blk_rq_sectors(rq))
 203#define rb_entry_rq(node)       rb_entry((node), struct request, rb_node)
 204
 205/*
 206 * Hack to reuse the csd.list list_head as the fifo time holder while
 207 * the request is in the io scheduler. Saves an unsigned long in rq.
 208 */
 209#define rq_fifo_time(rq)        ((unsigned long) (rq)->csd.list.next)
 210#define rq_set_fifo_time(rq,exp)        ((rq)->csd.list.next = (void *) (exp))
 211#define rq_entry_fifo(ptr)      list_entry((ptr), struct request, queuelist)
 212#define rq_fifo_clear(rq)       do {            \
 213        list_del_init(&(rq)->queuelist);        \
 214        INIT_LIST_HEAD(&(rq)->csd.list);        \
 215        } while (0)
 216
 217#else /* CONFIG_BLOCK */
 218
 219static inline void load_default_elevator_module(void) { }
 220
 221#endif /* CONFIG_BLOCK */
 222#endif
 223