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 typedef int (elevator_merge_fn) (struct request_queue *, struct request **,
   9                                  struct bio *);
  10
  11 typedef void (elevator_merge_req_fn) (struct request_queue *, struct request *, struct request *);
  12
  13 typedef void (elevator_merged_fn) (struct request_queue *, struct request *, int);
  14
  15 typedef int (elevator_allow_merge_fn) (struct request_queue *, struct request *, struct bio *);
  16
  17 typedef void (elevator_bio_merged_fn) (struct request_queue *,
  18                                                 struct request *, struct bio *);
  19
  20 typedef int (elevator_dispatch_fn) (struct request_queue *, int);
  21
  22 typedef void (elevator_add_req_fn) (struct request_queue *, struct request *);
  23 typedef struct request *(elevator_request_list_fn) (struct request_queue *, struct request *);
  24 typedef void (elevator_completed_req_fn) (struct request_queue *, struct request *);
  25 typedef int (elevator_may_queue_fn) (struct request_queue *, int);
  26
  27 typedef int (elevator_set_req_fn) (struct request_queue *, struct request *, gfp_t);
  28 typedef void (elevator_put_req_fn) (struct request *);
  29 typedef void (elevator_activate_req_fn) (struct request_queue *, struct request *);
  30 typedef void (elevator_deactivate_req_fn) (struct request_queue *, struct request *);
  31
  32 typedef void *(elevator_init_fn) (struct request_queue *);
  33 typedef void (elevator_exit_fn) (struct elevator_queue *);
  34
  35 struct elevator_ops
  36 {
  37         elevator_merge_fn *elevator_merge_fn;
  38         elevator_merged_fn *elevator_merged_fn;
  39         elevator_merge_req_fn *elevator_merge_req_fn;
  40         elevator_allow_merge_fn *elevator_allow_merge_fn;
  41
  42         /*
  43          * Used for both plugged list and elevator merging and in the
  44          * former case called without queue_lock.  Read comment on top of
  45          * attempt_plug_merge() for details.
  46          */
  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_set_req_fn *elevator_set_req_fn;
  60         elevator_put_req_fn *elevator_put_req_fn;
  61
  62         elevator_may_queue_fn *elevator_may_queue_fn;
  63
  64         elevator_init_fn *elevator_init_fn;
  65         elevator_exit_fn *elevator_exit_fn;
  66 };
  67
  68 #define ELV_NAME_MAX    (16)
  69
  70 struct elv_fs_entry {
  71         struct attribute attr;
  72         ssize_t (*show)(struct elevator_queue *, char *);
  73         ssize_t (*store)(struct elevator_queue *, const char *, size_t);
  74 };
  75
  76 /*
  77  * identifies an elevator type, such as AS or deadline
  78  */
  79 struct elevator_type
  80 {
  81         struct list_head list;
  82         struct elevator_ops ops;
  83         struct elv_fs_entry *elevator_attrs;
  84         char elevator_name[ELV_NAME_MAX];
  85         struct module *elevator_owner;
  86 };
  87
  88 /*
  89  * each queue has an elevator_queue associated with it
  90  */
  91 struct elevator_queue
  92 {
  93         struct elevator_ops *ops;
  94         void *elevator_data;
  95         struct kobject kobj;
  96         struct elevator_type *elevator_type;
  97         struct mutex sysfs_lock;
  98         struct hlist_head *hash;
  99         unsigned int registered:1;
 100 };
 101
 102 /*
 103  * block elevator interface
 104  */
 105 extern void elv_dispatch_sort(struct request_queue *, struct request *);
 106 extern void elv_dispatch_add_tail(struct request_queue *, struct request *);
 107 extern void elv_add_request(struct request_queue *, struct request *, int);
 108 extern void __elv_add_request(struct request_queue *, struct request *, int);
 109 extern int elv_merge(struct request_queue *, struct request **, struct bio *);
 110 extern int elv_try_merge(struct request *, struct bio *);
 111 extern void elv_merge_requests(struct request_queue *, struct request *,
 112                                struct request *);
 113 extern void elv_merged_request(struct request_queue *, struct request *, int);
 114 extern void elv_bio_merged(struct request_queue *q, struct request *,
 115                                 struct bio *);
 116 extern void elv_requeue_request(struct request_queue *, struct request *);
 117 extern struct request *elv_former_request(struct request_queue *, struct request *);
 118 extern struct request *elv_latter_request(struct request_queue *, struct request *);
 119 extern int elv_register_queue(struct request_queue *q);
 120 extern void elv_unregister_queue(struct request_queue *q);
 121 extern int elv_may_queue(struct request_queue *, int);
 122 extern void elv_abort_queue(struct request_queue *);
 123 extern void elv_completed_request(struct request_queue *, struct request *);
 124 extern int elv_set_request(struct request_queue *, struct request *, gfp_t);
 125 extern void elv_put_request(struct request_queue *, struct request *);
 126 extern void elv_drain_elevator(struct request_queue *);
 127
 128 /*
 129  * io scheduler registration
 130  */
 131 extern void elv_register(struct elevator_type *);
 132 extern void elv_unregister(struct elevator_type *);
 133
 134 /*
 135  * io scheduler sysfs switching
 136  */
 137 extern ssize_t elv_iosched_show(struct request_queue *, char *);
 138 extern ssize_t elv_iosched_store(struct request_queue *, const char *, size_t);
 139
 140 extern int elevator_init(struct request_queue *, char *);
 141 extern void elevator_exit(struct elevator_queue *);
 142 extern int elevator_change(struct request_queue *, const char *);
 143 extern int elv_rq_merge_ok(struct request *, struct bio *);
 144
 145 /*
 146  * Helper functions.
 147  */
 148 extern struct request *elv_rb_former_request(struct request_queue *, struct request *);
 149 extern struct request *elv_rb_latter_request(struct request_queue *, struct request *);
 150
 151 /*
 152  * rb support functions.
 153  */
 154 extern void elv_rb_add(struct rb_root *, struct request *);
 155 extern void elv_rb_del(struct rb_root *, struct request *);
 156 extern struct request *elv_rb_find(struct rb_root *, sector_t);
 157
 158 /*
 159  * Return values from elevator merger
 160  */
 161 #define ELEVATOR_NO_MERGE       0
 162 #define ELEVATOR_FRONT_MERGE    1
 163 #define ELEVATOR_BACK_MERGE     2
 164
 165 /*
 166  * Insertion selection
 167  */
 168 #define ELEVATOR_INSERT_FRONT   1
 169 #define ELEVATOR_INSERT_BACK    2
 170 #define ELEVATOR_INSERT_SORT    3
 171 #define ELEVATOR_INSERT_REQUEUE 4
 172 #define ELEVATOR_INSERT_FLUSH   5
 173 #define ELEVATOR_INSERT_SORT_MERGE      6
 174
 175 /*
 176  * return values from elevator_may_queue_fn
 177  */
 178 enum {
 179         ELV_MQUEUE_MAY,
 180         ELV_MQUEUE_NO,
 181         ELV_MQUEUE_MUST,
 182 };
 183
 184 #define rq_end_sector(rq)       (blk_rq_pos(rq) + blk_rq_sectors(rq))
 185 #define rb_entry_rq(node)       rb_entry((node), struct request, rb_node)
 186
 187 /*
 188  * Hack to reuse the csd.list list_head as the fifo time holder while
 189  * the request is in the io scheduler. Saves an unsigned long in rq.
 190  */
 191 #define rq_fifo_time(rq)        ((unsigned long) (rq)->csd.list.next)
 192 #define rq_set_fifo_time(rq,exp)        ((rq)->csd.list.next = (void *) (exp))
 193 #define rq_entry_fifo(ptr)      list_entry((ptr), struct request, queuelist)
 194 #define rq_fifo_clear(rq)       do {            \
 195         list_del_init(&(rq)->queuelist);        \
 196         INIT_LIST_HEAD(&(rq)->csd.list);        \
 197         } while (0)
 198
 199 /*
 200  * io context count accounting
 201  */
 202 #define elv_ioc_count_mod(name, __val) this_cpu_add(name, __val)
 203 #define elv_ioc_count_inc(name) this_cpu_inc(name)
 204 #define elv_ioc_count_dec(name) this_cpu_dec(name)
 205
 206 #define elv_ioc_count_read(name)                                \
 207 ({                                                              \
 208         unsigned long __val = 0;                                \
 209         int __cpu;                                              \
 210         smp_wmb();                                              \
 211         for_each_possible_cpu(__cpu)                            \
 212                 __val += per_cpu(name, __cpu);                  \
 213         __val;                                                  \
 214 })
 215
 216 #endif /* CONFIG_BLOCK */
 217 #endif