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
   9 struct io_cq;
  10 struct elevator_type;
  11
  12 typedef int (elevator_merge_fn) (struct request_queue *, struct request **,
  13                                  struct bio *);
  14
  15 typedef void (elevator_merge_req_fn) (struct request_queue *, struct request *, struct request *);
  16
  17 typedef void (elevator_merged_fn) (struct request_queue *, struct request *, int);
  18
  19 typedef int (elevator_allow_merge_fn) (struct request_queue *, struct request *, struct bio *);
  20
  21 typedef void (elevator_bio_merged_fn) (struct request_queue *,
  22                                                 struct request *, struct bio *);
  23
  24 typedef int (elevator_dispatch_fn) (struct request_queue *, int);
  25
  26 typedef void (elevator_add_req_fn) (struct request_queue *, struct request *);
  27 typedef struct request *(elevator_request_list_fn) (struct request_queue *, struct request *);
  28 typedef void (elevator_completed_req_fn) (struct request_queue *, struct request *);
  29 typedef int (elevator_may_queue_fn) (struct request_queue *, int);
  30
  31 typedef void (elevator_init_icq_fn) (struct io_cq *);
  32 typedef void (elevator_exit_icq_fn) (struct io_cq *);
  33 typedef int (elevator_set_req_fn) (struct request_queue *, struct request *,
  34                                    struct bio *, gfp_t);
  35 typedef void (elevator_put_req_fn) (struct request *);
  36 typedef void (elevator_activate_req_fn) (struct request_queue *, struct request *);
  37 typedef void (elevator_deactivate_req_fn) (struct request_queue *, struct request *);
  38
  39 typedef int (elevator_init_fn) (struct request_queue *,
  40                                 struct elevator_type *e);
  41 typedef void (elevator_exit_fn) (struct elevator_queue *);
  42
  43 struct 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
  75 struct 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  */
  84 struct 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  */
 107 struct 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  */
 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 *q, struct request *rq,
 139                            struct bio *bio, gfp_t gfp_mask);
 140 extern void elv_put_request(struct request_queue *, struct request *);
 141 extern void elv_drain_elevator(struct request_queue *);
 142
 143 /*
 144  * io scheduler registration
 145  */
 146 extern void __init load_default_elevator_module(void);
 147 extern int elv_register(struct elevator_type *);
 148 extern void elv_unregister(struct elevator_type *);
 149
 150 /*
 151  * io scheduler sysfs switching
 152  */
 153 extern ssize_t elv_iosched_show(struct request_queue *, char *);
 154 extern ssize_t elv_iosched_store(struct request_queue *, const char *, size_t);
 155
 156 extern int elevator_init(struct request_queue *, char *);
 157 extern void elevator_exit(struct elevator_queue *);
 158 extern int elevator_change(struct request_queue *, const char *);
 159 extern bool elv_rq_merge_ok(struct request *, struct bio *);
 160 extern struct elevator_queue *elevator_alloc(struct request_queue *,
 161                                         struct elevator_type *);
 162
 163 /*
 164  * Helper functions.
 165  */
 166 extern struct request *elv_rb_former_request(struct request_queue *, struct request *);
 167 extern struct request *elv_rb_latter_request(struct request_queue *, struct request *);
 168
 169 /*
 170  * rb support functions.
 171  */
 172 extern void elv_rb_add(struct rb_root *, struct request *);
 173 extern void elv_rb_del(struct rb_root *, struct request *);
 174 extern 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  */
 196 enum {
 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
 219 static inline void load_default_elevator_module(void) { }
 220
 221 #endif /* CONFIG_BLOCK */
 222 #endif