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         void (*trim)(struct io_context *);
  67 };
  68
  69 #define ELV_NAME_MAX    (16)
  70
  71 struct elv_fs_entry {
  72         struct attribute attr;
  73         ssize_t (*show)(struct elevator_queue *, char *);
  74         ssize_t (*store)(struct elevator_queue *, const char *, size_t);
  75 };
  76
  77 /*
  78  * identifies an elevator type, such as AS or deadline
  79  */
  80 struct elevator_type
  81 {
  82         struct list_head list;
  83         struct elevator_ops ops;
  84         struct elv_fs_entry *elevator_attrs;
  85         char elevator_name[ELV_NAME_MAX];
  86         struct module *elevator_owner;
  87 };
  88
  89 /*
  90  * each queue has an elevator_queue associated with it
  91  */
  92 struct elevator_queue
  93 {
  94         struct elevator_ops *ops;
  95         void *elevator_data;
  96         struct kobject kobj;
  97         struct elevator_type *elevator_type;
  98         struct mutex sysfs_lock;
  99         struct hlist_head *hash;
 100         unsigned int registered:1;
 101 };
 102
 103 /*
 104  * block elevator interface
 105  */
 106 extern void elv_dispatch_sort(struct request_queue *, struct request *);
 107 extern void elv_dispatch_add_tail(struct request_queue *, struct request *);
 108 extern void elv_add_request(struct request_queue *, struct request *, int);
 109 extern void __elv_add_request(struct request_queue *, struct request *, int);
 110 extern int elv_merge(struct request_queue *, struct request **, struct bio *);
 111 extern int elv_try_merge(struct request *, struct bio *);
 112 extern void elv_merge_requests(struct request_queue *, struct request *,
 113                                struct request *);
 114 extern void elv_merged_request(struct request_queue *, struct request *, int);
 115 extern void elv_bio_merged(struct request_queue *q, struct request *,
 116                                 struct bio *);
 117 extern void elv_requeue_request(struct request_queue *, struct request *);
 118 extern struct request *elv_former_request(struct request_queue *, struct request *);
 119 extern struct request *elv_latter_request(struct request_queue *, struct request *);
 120 extern int elv_register_queue(struct request_queue *q);
 121 extern void elv_unregister_queue(struct request_queue *q);
 122 extern int elv_may_queue(struct request_queue *, int);
 123 extern void elv_abort_queue(struct request_queue *);
 124 extern void elv_completed_request(struct request_queue *, struct request *);
 125 extern int elv_set_request(struct request_queue *, struct request *, gfp_t);
 126 extern void elv_put_request(struct request_queue *, struct request *);
 127 extern void elv_drain_elevator(struct request_queue *);
 128
 129 /*
 130  * io scheduler registration
 131  */
 132 extern void elv_register(struct elevator_type *);
 133 extern void elv_unregister(struct elevator_type *);
 134
 135 /*
 136  * io scheduler sysfs switching
 137  */
 138 extern ssize_t elv_iosched_show(struct request_queue *, char *);
 139 extern ssize_t elv_iosched_store(struct request_queue *, const char *, size_t);
 140
 141 extern int elevator_init(struct request_queue *, char *);
 142 extern void elevator_exit(struct elevator_queue *);
 143 extern int elevator_change(struct request_queue *, const char *);
 144 extern int elv_rq_merge_ok(struct request *, struct bio *);
 145
 146 /*
 147  * Helper functions.
 148  */
 149 extern struct request *elv_rb_former_request(struct request_queue *, struct request *);
 150 extern struct request *elv_rb_latter_request(struct request_queue *, struct request *);
 151
 152 /*
 153  * rb support functions.
 154  */
 155 extern void elv_rb_add(struct rb_root *, struct request *);
 156 extern void elv_rb_del(struct rb_root *, struct request *);
 157 extern struct request *elv_rb_find(struct rb_root *, sector_t);
 158
 159 /*
 160  * Return values from elevator merger
 161  */
 162 #define ELEVATOR_NO_MERGE       0
 163 #define ELEVATOR_FRONT_MERGE    1
 164 #define ELEVATOR_BACK_MERGE     2
 165
 166 /*
 167  * Insertion selection
 168  */
 169 #define ELEVATOR_INSERT_FRONT   1
 170 #define ELEVATOR_INSERT_BACK    2
 171 #define ELEVATOR_INSERT_SORT    3
 172 #define ELEVATOR_INSERT_REQUEUE 4
 173 #define ELEVATOR_INSERT_FLUSH   5
 174 #define ELEVATOR_INSERT_SORT_MERGE      6
 175
 176 /*
 177  * return values from elevator_may_queue_fn
 178  */
 179 enum {
 180         ELV_MQUEUE_MAY,
 181         ELV_MQUEUE_NO,
 182         ELV_MQUEUE_MUST,
 183 };
 184
 185 #define rq_end_sector(rq)       (blk_rq_pos(rq) + blk_rq_sectors(rq))
 186 #define rb_entry_rq(node)       rb_entry((node), struct request, rb_node)
 187
 188 /*
 189  * Hack to reuse the csd.list list_head as the fifo time holder while
 190  * the request is in the io scheduler. Saves an unsigned long in rq.
 191  */
 192 #define rq_fifo_time(rq)        ((unsigned long) (rq)->csd.list.next)
 193 #define rq_set_fifo_time(rq,exp)        ((rq)->csd.list.next = (void *) (exp))
 194 #define rq_entry_fifo(ptr)      list_entry((ptr), struct request, queuelist)
 195 #define rq_fifo_clear(rq)       do {            \
 196         list_del_init(&(rq)->queuelist);        \
 197         INIT_LIST_HEAD(&(rq)->csd.list);        \
 198         } while (0)
 199
 200 /*
 201  * io context count accounting
 202  */
 203 #define elv_ioc_count_mod(name, __val) this_cpu_add(name, __val)
 204 #define elv_ioc_count_inc(name) this_cpu_inc(name)
 205 #define elv_ioc_count_dec(name) this_cpu_dec(name)
 206
 207 #define elv_ioc_count_read(name)                                \
 208 ({                                                              \
 209         unsigned long __val = 0;                                \
 210         int __cpu;                                              \
 211         smp_wmb();                                              \
 212         for_each_possible_cpu(__cpu)                            \
 213                 __val += per_cpu(name, __cpu);                  \
 214         __val;                                                  \
 215 })
 216
 217 #endif /* CONFIG_BLOCK */
 218 #endif