include/linux/elevator.h

   1 #ifndef _LINUX_ELEVATOR_H
   2 #define _LINUX_ELEVATOR_H
   3
   4 #include <linux/percpu.h>
   5
   6 typedef int (elevator_merge_fn) (request_queue_t *, struct request **,
   7                                  struct bio *);
   8
   9 typedef void (elevator_merge_req_fn) (request_queue_t *, struct request *, struct request *);
  10
  11 typedef void (elevator_merged_fn) (request_queue_t *, struct request *, int);
  12
  13 typedef int (elevator_dispatch_fn) (request_queue_t *, int);
  14
  15 typedef void (elevator_add_req_fn) (request_queue_t *, struct request *);
  16 typedef int (elevator_queue_empty_fn) (request_queue_t *);
  17 typedef struct request *(elevator_request_list_fn) (request_queue_t *, struct request *);
  18 typedef void (elevator_completed_req_fn) (request_queue_t *, struct request *);
  19 typedef int (elevator_may_queue_fn) (request_queue_t *, int);
  20
  21 typedef int (elevator_set_req_fn) (request_queue_t *, struct request *, gfp_t);
  22 typedef void (elevator_put_req_fn) (request_queue_t *, struct request *);
  23 typedef void (elevator_activate_req_fn) (request_queue_t *, struct request *);
  24 typedef void (elevator_deactivate_req_fn) (request_queue_t *, struct request *);
  25
  26 typedef void *(elevator_init_fn) (request_queue_t *, elevator_t *);
  27 typedef void (elevator_exit_fn) (elevator_t *);
  28
  29 struct elevator_ops
  30 {
  31         elevator_merge_fn *elevator_merge_fn;
  32         elevator_merged_fn *elevator_merged_fn;
  33         elevator_merge_req_fn *elevator_merge_req_fn;
  34
  35         elevator_dispatch_fn *elevator_dispatch_fn;
  36         elevator_add_req_fn *elevator_add_req_fn;
  37         elevator_activate_req_fn *elevator_activate_req_fn;
  38         elevator_deactivate_req_fn *elevator_deactivate_req_fn;
  39
  40         elevator_queue_empty_fn *elevator_queue_empty_fn;
  41         elevator_completed_req_fn *elevator_completed_req_fn;
  42
  43         elevator_request_list_fn *elevator_former_req_fn;
  44         elevator_request_list_fn *elevator_latter_req_fn;
  45
  46         elevator_set_req_fn *elevator_set_req_fn;
  47         elevator_put_req_fn *elevator_put_req_fn;
  48
  49         elevator_may_queue_fn *elevator_may_queue_fn;
  50
  51         elevator_init_fn *elevator_init_fn;
  52         elevator_exit_fn *elevator_exit_fn;
  53         void (*trim)(struct io_context *);
  54 };
  55
  56 #define ELV_NAME_MAX    (16)
  57
  58 struct elv_fs_entry {
  59         struct attribute attr;
  60         ssize_t (*show)(elevator_t *, char *);
  61         ssize_t (*store)(elevator_t *, const char *, size_t);
  62 };
  63
  64 /*
  65  * identifies an elevator type, such as AS or deadline
  66  */
  67 struct elevator_type
  68 {
  69         struct list_head list;
  70         struct elevator_ops ops;
  71         struct elevator_type *elevator_type;
  72         struct elv_fs_entry *elevator_attrs;
  73         char elevator_name[ELV_NAME_MAX];
  74         struct module *elevator_owner;
  75 };
  76
  77 /*
  78  * each queue has an elevator_queue associated with it
  79  */
  80 struct elevator_queue
  81 {
  82         struct elevator_ops *ops;
  83         void *elevator_data;
  84         struct kobject kobj;
  85         struct elevator_type *elevator_type;
  86         struct mutex sysfs_lock;
  87         struct hlist_head *hash;
  88 };
  89
  90 /*
  91  * block elevator interface
  92  */
  93 extern void elv_dispatch_sort(request_queue_t *, struct request *);
  94 extern void elv_dispatch_add_tail(request_queue_t *, struct request *);
  95 extern void elv_add_request(request_queue_t *, struct request *, int, int);
  96 extern void __elv_add_request(request_queue_t *, struct request *, int, int);
  97 extern void elv_insert(request_queue_t *, struct request *, int);
  98 extern int elv_merge(request_queue_t *, struct request **, struct bio *);
  99 extern void elv_merge_requests(request_queue_t *, struct request *,
 100                                struct request *);
 101 extern void elv_merged_request(request_queue_t *, struct request *, int);
 102 extern void elv_dequeue_request(request_queue_t *, struct request *);
 103 extern void elv_requeue_request(request_queue_t *, struct request *);
 104 extern int elv_queue_empty(request_queue_t *);
 105 extern struct request *elv_next_request(struct request_queue *q);
 106 extern struct request *elv_former_request(request_queue_t *, struct request *);
 107 extern struct request *elv_latter_request(request_queue_t *, struct request *);
 108 extern int elv_register_queue(request_queue_t *q);
 109 extern void elv_unregister_queue(request_queue_t *q);
 110 extern int elv_may_queue(request_queue_t *, int);
 111 extern void elv_completed_request(request_queue_t *, struct request *);
 112 extern int elv_set_request(request_queue_t *, struct request *, gfp_t);
 113 extern void elv_put_request(request_queue_t *, struct request *);
 114
 115 /*
 116  * io scheduler registration
 117  */
 118 extern int elv_register(struct elevator_type *);
 119 extern void elv_unregister(struct elevator_type *);
 120
 121 /*
 122  * io scheduler sysfs switching
 123  */
 124 extern ssize_t elv_iosched_show(request_queue_t *, char *);
 125 extern ssize_t elv_iosched_store(request_queue_t *, const char *, size_t);
 126
 127 extern int elevator_init(request_queue_t *, char *);
 128 extern void elevator_exit(elevator_t *);
 129 extern int elv_rq_merge_ok(struct request *, struct bio *);
 130
 131 /*
 132  * Helper functions.
 133  */
 134 extern struct request *elv_rb_former_request(request_queue_t *, struct request *);
 135 extern struct request *elv_rb_latter_request(request_queue_t *, struct request *);
 136
 137 /*
 138  * rb support functions.
 139  */
 140 extern struct request *elv_rb_add(struct rb_root *, struct request *);
 141 extern void elv_rb_del(struct rb_root *, struct request *);
 142 extern struct request *elv_rb_find(struct rb_root *, sector_t);
 143
 144 /*
 145  * Return values from elevator merger
 146  */
 147 #define ELEVATOR_NO_MERGE       0
 148 #define ELEVATOR_FRONT_MERGE    1
 149 #define ELEVATOR_BACK_MERGE     2
 150
 151 /*
 152  * Insertion selection
 153  */
 154 #define ELEVATOR_INSERT_FRONT   1
 155 #define ELEVATOR_INSERT_BACK    2
 156 #define ELEVATOR_INSERT_SORT    3
 157 #define ELEVATOR_INSERT_REQUEUE 4
 158
 159 /*
 160  * return values from elevator_may_queue_fn
 161  */
 162 enum {
 163         ELV_MQUEUE_MAY,
 164         ELV_MQUEUE_NO,
 165         ELV_MQUEUE_MUST,
 166 };
 167
 168 #define rq_end_sector(rq)       ((rq)->sector + (rq)->nr_sectors)
 169 #define rb_entry_rq(node)       rb_entry((node), struct request, rb_node)
 170
 171 /*
 172  * Hack to reuse the donelist list_head as the fifo time holder while
 173  * the request is in the io scheduler. Saves an unsigned long in rq.
 174  */
 175 #define rq_fifo_time(rq)        ((unsigned long) (rq)->donelist.next)
 176 #define rq_set_fifo_time(rq,exp)        ((rq)->donelist.next = (void *) (exp))
 177 #define rq_entry_fifo(ptr)      list_entry((ptr), struct request, queuelist)
 178 #define rq_fifo_clear(rq)       do {            \
 179         list_del_init(&(rq)->queuelist);        \
 180         INIT_LIST_HEAD(&(rq)->donelist);        \
 181         } while (0)
 182
 183 /*
 184  * io context count accounting
 185  */
 186 #define elv_ioc_count_mod(name, __val)                          \
 187         do {                                                    \
 188                 preempt_disable();                              \
 189                 __get_cpu_var(name) += (__val);                 \
 190                 preempt_enable();                               \
 191         } while (0)
 192
 193 #define elv_ioc_count_inc(name) elv_ioc_count_mod(name, 1)
 194 #define elv_ioc_count_dec(name) elv_ioc_count_mod(name, -1)
 195
 196 #define elv_ioc_count_read(name)                                \
 197 ({                                                              \
 198         unsigned long __val = 0;                                \
 199         int __cpu;                                              \
 200         smp_wmb();                                              \
 201         for_each_possible_cpu(__cpu)                            \
 202                 __val += per_cpu(name, __cpu);                  \
 203         __val;                                                  \
 204 })
 205
 206 #endif