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) (request_queue_t *, struct request **,
   9                                  struct bio *);
  10
  11 typedef void (elevator_merge_req_fn) (request_queue_t *, struct request *, struct request *);
  12
  13 typedef void (elevator_merged_fn) (request_queue_t *, struct request *, int);
  14
  15 typedef int (elevator_dispatch_fn) (request_queue_t *, int);
  16
  17 typedef void (elevator_add_req_fn) (request_queue_t *, struct request *);
  18 typedef int (elevator_queue_empty_fn) (request_queue_t *);
  19 typedef struct request *(elevator_request_list_fn) (request_queue_t *, struct request *);
  20 typedef void (elevator_completed_req_fn) (request_queue_t *, struct request *);
  21 typedef int (elevator_may_queue_fn) (request_queue_t *, int);
  22
  23 typedef int (elevator_set_req_fn) (request_queue_t *, struct request *, gfp_t);
  24 typedef void (elevator_put_req_fn) (request_queue_t *, struct request *);
  25 typedef void (elevator_activate_req_fn) (request_queue_t *, struct request *);
  26 typedef void (elevator_deactivate_req_fn) (request_queue_t *, struct request *);
  27
  28 typedef void *(elevator_init_fn) (request_queue_t *, elevator_t *);
  29 typedef void (elevator_exit_fn) (elevator_t *);
  30
  31 struct elevator_ops
  32 {
  33         elevator_merge_fn *elevator_merge_fn;
  34         elevator_merged_fn *elevator_merged_fn;
  35         elevator_merge_req_fn *elevator_merge_req_fn;
  36
  37         elevator_dispatch_fn *elevator_dispatch_fn;
  38         elevator_add_req_fn *elevator_add_req_fn;
  39         elevator_activate_req_fn *elevator_activate_req_fn;
  40         elevator_deactivate_req_fn *elevator_deactivate_req_fn;
  41
  42         elevator_queue_empty_fn *elevator_queue_empty_fn;
  43         elevator_completed_req_fn *elevator_completed_req_fn;
  44
  45         elevator_request_list_fn *elevator_former_req_fn;
  46         elevator_request_list_fn *elevator_latter_req_fn;
  47
  48         elevator_set_req_fn *elevator_set_req_fn;
  49         elevator_put_req_fn *elevator_put_req_fn;
  50
  51         elevator_may_queue_fn *elevator_may_queue_fn;
  52
  53         elevator_init_fn *elevator_init_fn;
  54         elevator_exit_fn *elevator_exit_fn;
  55         void (*trim)(struct io_context *);
  56 };
  57
  58 #define ELV_NAME_MAX    (16)
  59
  60 struct elv_fs_entry {
  61         struct attribute attr;
  62         ssize_t (*show)(elevator_t *, char *);
  63         ssize_t (*store)(elevator_t *, const char *, size_t);
  64 };
  65
  66 /*
  67  * identifies an elevator type, such as AS or deadline
  68  */
  69 struct elevator_type
  70 {
  71         struct list_head list;
  72         struct elevator_ops ops;
  73         struct elevator_type *elevator_type;
  74         struct elv_fs_entry *elevator_attrs;
  75         char elevator_name[ELV_NAME_MAX];
  76         struct module *elevator_owner;
  77 };
  78
  79 /*
  80  * each queue has an elevator_queue associated with it
  81  */
  82 struct elevator_queue
  83 {
  84         struct elevator_ops *ops;
  85         void *elevator_data;
  86         struct kobject kobj;
  87         struct elevator_type *elevator_type;
  88         struct mutex sysfs_lock;
  89         struct hlist_head *hash;
  90 };
  91
  92 /*
  93  * block elevator interface
  94  */
  95 extern void elv_dispatch_sort(request_queue_t *, struct request *);
  96 extern void elv_dispatch_add_tail(request_queue_t *, struct request *);
  97 extern void elv_add_request(request_queue_t *, struct request *, int, int);
  98 extern void __elv_add_request(request_queue_t *, struct request *, int, int);
  99 extern void elv_insert(request_queue_t *, struct request *, int);
 100 extern int elv_merge(request_queue_t *, struct request **, struct bio *);
 101 extern void elv_merge_requests(request_queue_t *, struct request *,
 102                                struct request *);
 103 extern void elv_merged_request(request_queue_t *, struct request *, int);
 104 extern void elv_dequeue_request(request_queue_t *, struct request *);
 105 extern void elv_requeue_request(request_queue_t *, struct request *);
 106 extern int elv_queue_empty(request_queue_t *);
 107 extern struct request *elv_next_request(struct request_queue *q);
 108 extern struct request *elv_former_request(request_queue_t *, struct request *);
 109 extern struct request *elv_latter_request(request_queue_t *, struct request *);
 110 extern int elv_register_queue(request_queue_t *q);
 111 extern void elv_unregister_queue(request_queue_t *q);
 112 extern int elv_may_queue(request_queue_t *, int);
 113 extern void elv_completed_request(request_queue_t *, struct request *);
 114 extern int elv_set_request(request_queue_t *, struct request *, gfp_t);
 115 extern void elv_put_request(request_queue_t *, struct request *);
 116
 117 /*
 118  * io scheduler registration
 119  */
 120 extern int elv_register(struct elevator_type *);
 121 extern void elv_unregister(struct elevator_type *);
 122
 123 /*
 124  * io scheduler sysfs switching
 125  */
 126 extern ssize_t elv_iosched_show(request_queue_t *, char *);
 127 extern ssize_t elv_iosched_store(request_queue_t *, const char *, size_t);
 128
 129 extern int elevator_init(request_queue_t *, char *);
 130 extern void elevator_exit(elevator_t *);
 131 extern int elv_rq_merge_ok(struct request *, struct bio *);
 132
 133 /*
 134  * Helper functions.
 135  */
 136 extern struct request *elv_rb_former_request(request_queue_t *, struct request *);
 137 extern struct request *elv_rb_latter_request(request_queue_t *, struct request *);
 138
 139 /*
 140  * rb support functions.
 141  */
 142 extern struct request *elv_rb_add(struct rb_root *, struct request *);
 143 extern void elv_rb_del(struct rb_root *, struct request *);
 144 extern struct request *elv_rb_find(struct rb_root *, sector_t);
 145
 146 /*
 147  * Return values from elevator merger
 148  */
 149 #define ELEVATOR_NO_MERGE       0
 150 #define ELEVATOR_FRONT_MERGE    1
 151 #define ELEVATOR_BACK_MERGE     2
 152
 153 /*
 154  * Insertion selection
 155  */
 156 #define ELEVATOR_INSERT_FRONT   1
 157 #define ELEVATOR_INSERT_BACK    2
 158 #define ELEVATOR_INSERT_SORT    3
 159 #define ELEVATOR_INSERT_REQUEUE 4
 160
 161 /*
 162  * return values from elevator_may_queue_fn
 163  */
 164 enum {
 165         ELV_MQUEUE_MAY,
 166         ELV_MQUEUE_NO,
 167         ELV_MQUEUE_MUST,
 168 };
 169
 170 #define rq_end_sector(rq)       ((rq)->sector + (rq)->nr_sectors)
 171 #define rb_entry_rq(node)       rb_entry((node), struct request, rb_node)
 172
 173 /*
 174  * Hack to reuse the donelist list_head as the fifo time holder while
 175  * the request is in the io scheduler. Saves an unsigned long in rq.
 176  */
 177 #define rq_fifo_time(rq)        ((unsigned long) (rq)->donelist.next)
 178 #define rq_set_fifo_time(rq,exp)        ((rq)->donelist.next = (void *) (exp))
 179 #define rq_entry_fifo(ptr)      list_entry((ptr), struct request, queuelist)
 180 #define rq_fifo_clear(rq)       do {            \
 181         list_del_init(&(rq)->queuelist);        \
 182         INIT_LIST_HEAD(&(rq)->donelist);        \
 183         } while (0)
 184
 185 /*
 186  * io context count accounting
 187  */
 188 #define elv_ioc_count_mod(name, __val)                          \
 189         do {                                                    \
 190                 preempt_disable();                              \
 191                 __get_cpu_var(name) += (__val);                 \
 192                 preempt_enable();                               \
 193         } while (0)
 194
 195 #define elv_ioc_count_inc(name) elv_ioc_count_mod(name, 1)
 196 #define elv_ioc_count_dec(name) elv_ioc_count_mod(name, -1)
 197
 198 #define elv_ioc_count_read(name)                                \
 199 ({                                                              \
 200         unsigned long __val = 0;                                \
 201         int __cpu;                                              \
 202         smp_wmb();                                              \
 203         for_each_possible_cpu(__cpu)                            \
 204                 __val += per_cpu(name, __cpu);                  \
 205         __val;                                                  \
 206 })
 207
 208 #endif /* CONFIG_BLOCK */
 209 #endif