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