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 int (elevator_dispatch_fn) (struct request_queue *, int);
  18
  19 typedef void (elevator_add_req_fn) (struct request_queue *, struct request *);
  20 typedef int (elevator_queue_empty_fn) (struct request_queue *);
  21 typedef struct request *(elevator_request_list_fn) (struct request_queue *, struct request *);
  22 typedef void (elevator_completed_req_fn) (struct request_queue *, struct request *);
  23 typedef int (elevator_may_queue_fn) (struct request_queue *, int);
  24
  25 typedef int (elevator_set_req_fn) (struct request_queue *, struct request *, gfp_t);
  26 typedef void (elevator_put_req_fn) (struct request *);
  27 typedef void (elevator_activate_req_fn) (struct request_queue *, struct request *);
  28 typedef void (elevator_deactivate_req_fn) (struct request_queue *, struct request *);
  29
  30 typedef void *(elevator_init_fn) (struct request_queue *);
  31 typedef void (elevator_exit_fn) (struct elevator_queue *);
  32
  33 struct elevator_ops
  34 {
  35         elevator_merge_fn *elevator_merge_fn;
  36         elevator_merged_fn *elevator_merged_fn;
  37         elevator_merge_req_fn *elevator_merge_req_fn;
  38         elevator_allow_merge_fn *elevator_allow_merge_fn;
  39
  40         elevator_dispatch_fn *elevator_dispatch_fn;
  41         elevator_add_req_fn *elevator_add_req_fn;
  42         elevator_activate_req_fn *elevator_activate_req_fn;
  43         elevator_deactivate_req_fn *elevator_deactivate_req_fn;
  44
  45         elevator_queue_empty_fn *elevator_queue_empty_fn;
  46         elevator_completed_req_fn *elevator_completed_req_fn;
  47
  48         elevator_request_list_fn *elevator_former_req_fn;
  49         elevator_request_list_fn *elevator_latter_req_fn;
  50
  51         elevator_set_req_fn *elevator_set_req_fn;
  52         elevator_put_req_fn *elevator_put_req_fn;
  53
  54         elevator_may_queue_fn *elevator_may_queue_fn;
  55
  56         elevator_init_fn *elevator_init_fn;
  57         elevator_exit_fn *elevator_exit_fn;
  58         void (*trim)(struct io_context *);
  59 };
  60
  61 #define ELV_NAME_MAX    (16)
  62
  63 struct elv_fs_entry {
  64         struct attribute attr;
  65         ssize_t (*show)(struct elevator_queue *, char *);
  66         ssize_t (*store)(struct elevator_queue *, const char *, size_t);
  67 };
  68
  69 /*
  70  * identifies an elevator type, such as AS or deadline
  71  */
  72 struct elevator_type
  73 {
  74         struct list_head list;
  75         struct elevator_ops ops;
  76         struct elv_fs_entry *elevator_attrs;
  77         char elevator_name[ELV_NAME_MAX];
  78         struct module *elevator_owner;
  79 };
  80
  81 /*
  82  * each queue has an elevator_queue associated with it
  83  */
  84 struct elevator_queue
  85 {
  86         struct elevator_ops *ops;
  87         void *elevator_data;
  88         struct kobject kobj;
  89         struct elevator_type *elevator_type;
  90         struct mutex sysfs_lock;
  91         struct hlist_head *hash;
  92 };
  93
  94 /*
  95  * block elevator interface
  96  */
  97 extern void elv_dispatch_sort(struct request_queue *, struct request *);
  98 extern void elv_dispatch_add_tail(struct request_queue *, struct request *);
  99 extern void elv_add_request(struct request_queue *, struct request *, int, int);
 100 extern void __elv_add_request(struct request_queue *, struct request *, int, int);
 101 extern void elv_insert(struct request_queue *, struct request *, int);
 102 extern int elv_merge(struct request_queue *, struct request **, struct bio *);
 103 extern void elv_merge_requests(struct request_queue *, struct request *,
 104                                struct request *);
 105 extern void elv_merged_request(struct request_queue *, struct request *, int);
 106 extern void elv_dequeue_request(struct request_queue *, struct request *);
 107 extern void elv_requeue_request(struct request_queue *, struct request *);
 108 extern int elv_queue_empty(struct request_queue *);
 109 extern struct request *elv_next_request(struct request_queue *q);
 110 extern struct request *elv_former_request(struct request_queue *, struct request *);
 111 extern struct request *elv_latter_request(struct request_queue *, struct request *);
 112 extern int elv_register_queue(struct request_queue *q);
 113 extern void elv_unregister_queue(struct request_queue *q);
 114 extern int elv_may_queue(struct request_queue *, int);
 115 extern void elv_abort_queue(struct request_queue *);
 116 extern void elv_completed_request(struct request_queue *, struct request *);
 117 extern int elv_set_request(struct request_queue *, struct request *, gfp_t);
 118 extern void elv_put_request(struct request_queue *, struct request *);
 119 extern void elv_drain_elevator(struct request_queue *);
 120
 121 /*
 122  * io scheduler registration
 123  */
 124 extern void elv_register(struct elevator_type *);
 125 extern void elv_unregister(struct elevator_type *);
 126
 127 /*
 128  * io scheduler sysfs switching
 129  */
 130 extern ssize_t elv_iosched_show(struct request_queue *, char *);
 131 extern ssize_t elv_iosched_store(struct request_queue *, const char *, size_t);
 132
 133 extern int elevator_init(struct request_queue *, char *);
 134 extern void elevator_exit(struct elevator_queue *);
 135 extern int elv_rq_merge_ok(struct request *, struct bio *);
 136
 137 /*
 138  * Helper functions.
 139  */
 140 extern struct request *elv_rb_former_request(struct request_queue *, struct request *);
 141 extern struct request *elv_rb_latter_request(struct request_queue *, struct request *);
 142
 143 /*
 144  * rb support functions.
 145  */
 146 extern struct request *elv_rb_add(struct rb_root *, struct request *);
 147 extern void elv_rb_del(struct rb_root *, struct request *);
 148 extern struct request *elv_rb_find(struct rb_root *, sector_t);
 149
 150 /*
 151  * Return values from elevator merger
 152  */
 153 #define ELEVATOR_NO_MERGE       0
 154 #define ELEVATOR_FRONT_MERGE    1
 155 #define ELEVATOR_BACK_MERGE     2
 156
 157 /*
 158  * Insertion selection
 159  */
 160 #define ELEVATOR_INSERT_FRONT   1
 161 #define ELEVATOR_INSERT_BACK    2
 162 #define ELEVATOR_INSERT_SORT    3
 163 #define ELEVATOR_INSERT_REQUEUE 4
 164
 165 /*
 166  * return values from elevator_may_queue_fn
 167  */
 168 enum {
 169         ELV_MQUEUE_MAY,
 170         ELV_MQUEUE_NO,
 171         ELV_MQUEUE_MUST,
 172 };
 173
 174 #define rq_end_sector(rq)       ((rq)->sector + (rq)->nr_sectors)
 175 #define rb_entry_rq(node)       rb_entry((node), struct request, rb_node)
 176
 177 /*
 178  * Hack to reuse the csd.list list_head as the fifo time holder while
 179  * the request is in the io scheduler. Saves an unsigned long in rq.
 180  */
 181 #define rq_fifo_time(rq)        ((unsigned long) (rq)->csd.list.next)
 182 #define rq_set_fifo_time(rq,exp)        ((rq)->csd.list.next = (void *) (exp))
 183 #define rq_entry_fifo(ptr)      list_entry((ptr), struct request, queuelist)
 184 #define rq_fifo_clear(rq)       do {            \
 185         list_del_init(&(rq)->queuelist);        \
 186         INIT_LIST_HEAD(&(rq)->csd.list);        \
 187         } while (0)
 188
 189 /*
 190  * io context count accounting
 191  */
 192 #define elv_ioc_count_mod(name, __val)                          \
 193         do {                                                    \
 194                 preempt_disable();                              \
 195                 __get_cpu_var(name) += (__val);                 \
 196                 preempt_enable();                               \
 197         } while (0)
 198
 199 #define elv_ioc_count_inc(name) elv_ioc_count_mod(name, 1)
 200 #define elv_ioc_count_dec(name) elv_ioc_count_mod(name, -1)
 201
 202 #define elv_ioc_count_read(name)                                \
 203 ({                                                              \
 204         unsigned long __val = 0;                                \
 205         int __cpu;                                              \
 206         smp_wmb();                                              \
 207         for_each_possible_cpu(__cpu)                            \
 208                 __val += per_cpu(name, __cpu);                  \
 209         __val;                                                  \
 210 })
 211
 212 #endif /* CONFIG_BLOCK */
 213 #endif