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 *, gfp_t);
  32 typedef void (elevator_put_req_fn) (struct request *);
  33 typedef void (elevator_activate_req_fn) (struct request_queue *, struct request *);
  34 typedef void (elevator_deactivate_req_fn) (struct request_queue *, struct request *);
  35
  36 typedef void *(elevator_init_fn) (struct request_queue *);
  37 typedef void (elevator_exit_fn) (struct elevator_queue *);
  38
  39 struct elevator_ops
  40 {
  41         elevator_merge_fn *elevator_merge_fn;
  42         elevator_merged_fn *elevator_merged_fn;
  43         elevator_merge_req_fn *elevator_merge_req_fn;
  44         elevator_allow_merge_fn *elevator_allow_merge_fn;
  45
  46         /*
  47          * Used for both plugged list and elevator merging and in the
  48          * former case called without queue_lock.  Read comment on top of
  49          * attempt_plug_merge() for details.
  50          */
  51         elevator_bio_merged_fn *elevator_bio_merged_fn;
  52
  53         elevator_dispatch_fn *elevator_dispatch_fn;
  54         elevator_add_req_fn *elevator_add_req_fn;
  55         elevator_activate_req_fn *elevator_activate_req_fn;
  56         elevator_deactivate_req_fn *elevator_deactivate_req_fn;
  57
  58         elevator_completed_req_fn *elevator_completed_req_fn;
  59
  60         elevator_request_list_fn *elevator_former_req_fn;
  61         elevator_request_list_fn *elevator_latter_req_fn;
  62
  63         elevator_init_icq_fn *elevator_init_icq_fn;     /* see iocontext.h */
  64         elevator_exit_icq_fn *elevator_exit_icq_fn;     /* ditto */
  65
  66         elevator_set_req_fn *elevator_set_req_fn;
  67         elevator_put_req_fn *elevator_put_req_fn;
  68
  69         elevator_may_queue_fn *elevator_may_queue_fn;
  70
  71         elevator_init_fn *elevator_init_fn;
  72         elevator_exit_fn *elevator_exit_fn;
  73 };
  74
  75 #define ELV_NAME_MAX    (16)
  76
  77 struct elv_fs_entry {
  78         struct attribute attr;
  79         ssize_t (*show)(struct elevator_queue *, char *);
  80         ssize_t (*store)(struct elevator_queue *, const char *, size_t);
  81 };
  82
  83 /*
  84  * identifies an elevator type, such as AS or deadline
  85  */
  86 struct elevator_type
  87 {
  88         /* managed by elevator core */
  89         struct kmem_cache *icq_cache;
  90
  91         /* fields provided by elevator implementation */
  92         struct elevator_ops ops;
  93         size_t icq_size;        /* see iocontext.h */
  94         size_t icq_align;       /* ditto */
  95         struct elv_fs_entry *elevator_attrs;
  96         char elevator_name[ELV_NAME_MAX];
  97         struct module *elevator_owner;
  98
  99         /* managed by elevator core */
 100         char icq_cache_name[ELV_NAME_MAX + 5];  /* elvname + "_io_cq" */
 101         struct list_head list;
 102 };
 103
 104 /*
 105  * each queue has an elevator_queue associated with it
 106  */
 107 struct elevator_queue
 108 {
 109         struct elevator_type *type;
 110         void *elevator_data;
 111         struct kobject kobj;
 112         struct mutex sysfs_lock;
 113         struct hlist_head *hash;
 114         unsigned int registered:1;
 115 };
 116
 117 /*
 118  * block elevator interface
 119  */
 120 extern void elv_dispatch_sort(struct request_queue *, struct request *);
 121 extern void elv_dispatch_add_tail(struct request_queue *, struct request *);
 122 extern void elv_add_request(struct request_queue *, struct request *, int);
 123 extern void __elv_add_request(struct request_queue *, struct request *, int);
 124 extern int elv_merge(struct request_queue *, struct request **, struct bio *);
 125 extern void elv_merge_requests(struct request_queue *, struct request *,
 126                                struct request *);
 127 extern void elv_merged_request(struct request_queue *, struct request *, int);
 128 extern void elv_bio_merged(struct request_queue *q, struct request *,
 129                                 struct bio *);
 130 extern void elv_requeue_request(struct request_queue *, struct request *);
 131 extern struct request *elv_former_request(struct request_queue *, struct request *);
 132 extern struct request *elv_latter_request(struct request_queue *, struct request *);
 133 extern int elv_register_queue(struct request_queue *q);
 134 extern void elv_unregister_queue(struct request_queue *q);
 135 extern int elv_may_queue(struct request_queue *, int);
 136 extern void elv_abort_queue(struct request_queue *);
 137 extern void elv_completed_request(struct request_queue *, struct request *);
 138 extern int elv_set_request(struct request_queue *, struct request *, gfp_t);
 139 extern void elv_put_request(struct request_queue *, struct request *);
 140 extern void elv_drain_elevator(struct request_queue *);
 141
 142 /*
 143  * io scheduler registration
 144  */
 145 extern int elv_register(struct elevator_type *);
 146 extern void elv_unregister(struct elevator_type *);
 147
 148 /*
 149  * io scheduler sysfs switching
 150  */
 151 extern ssize_t elv_iosched_show(struct request_queue *, char *);
 152 extern ssize_t elv_iosched_store(struct request_queue *, const char *, size_t);
 153
 154 extern int elevator_init(struct request_queue *, char *);
 155 extern void elevator_exit(struct elevator_queue *);
 156 extern int elevator_change(struct request_queue *, const char *);
 157 extern bool elv_rq_merge_ok(struct request *, struct bio *);
 158
 159 /*
 160  * Helper functions.
 161  */
 162 extern struct request *elv_rb_former_request(struct request_queue *, struct request *);
 163 extern struct request *elv_rb_latter_request(struct request_queue *, struct request *);
 164
 165 /*
 166  * rb support functions.
 167  */
 168 extern void elv_rb_add(struct rb_root *, struct request *);
 169 extern void elv_rb_del(struct rb_root *, struct request *);
 170 extern 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  */
 192 enum {
 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 #endif /* CONFIG_BLOCK */
 214 #endif