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