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 elv_fs_entry *elevator_attrs;
  74         char elevator_name[ELV_NAME_MAX];
  75         struct module *elevator_owner;
  76 };
  77
  78 /*
  79  * each queue has an elevator_queue associated with it
  80  */
  81 struct elevator_queue
  82 {
  83         struct elevator_ops *ops;
  84         void *elevator_data;
  85         struct kobject kobj;
  86         struct elevator_type *elevator_type;
  87         struct mutex sysfs_lock;
  88         struct hlist_head *hash;
  89 };
  90
  91 /*
  92  * block elevator interface
  93  */
  94 extern void elv_dispatch_sort(request_queue_t *, struct request *);
  95 extern void elv_dispatch_add_tail(request_queue_t *, struct request *);
  96 extern void elv_add_request(request_queue_t *, struct request *, int, int);
  97 extern void __elv_add_request(request_queue_t *, struct request *, int, int);
  98 extern void elv_insert(request_queue_t *, struct request *, int);
  99 extern int elv_merge(request_queue_t *, struct request **, struct bio *);
 100 extern void elv_merge_requests(request_queue_t *, struct request *,
 101                                struct request *);
 102 extern void elv_merged_request(request_queue_t *, struct request *, int);
 103 extern void elv_dequeue_request(request_queue_t *, struct request *);
 104 extern void elv_requeue_request(request_queue_t *, struct request *);
 105 extern int elv_queue_empty(request_queue_t *);
 106 extern struct request *elv_next_request(struct request_queue *q);
 107 extern struct request *elv_former_request(request_queue_t *, struct request *);
 108 extern struct request *elv_latter_request(request_queue_t *, struct request *);
 109 extern int elv_register_queue(request_queue_t *q);
 110 extern void elv_unregister_queue(request_queue_t *q);
 111 extern int elv_may_queue(request_queue_t *, int);
 112 extern void elv_completed_request(request_queue_t *, struct request *);
 113 extern int elv_set_request(request_queue_t *, struct request *, gfp_t);
 114 extern void elv_put_request(request_queue_t *, struct request *);
 115
 116 /*
 117  * io scheduler registration
 118  */
 119 extern int elv_register(struct elevator_type *);
 120 extern void elv_unregister(struct elevator_type *);
 121
 122 /*
 123  * io scheduler sysfs switching
 124  */
 125 extern ssize_t elv_iosched_show(request_queue_t *, char *);
 126 extern ssize_t elv_iosched_store(request_queue_t *, const char *, size_t);
 127
 128 extern int elevator_init(request_queue_t *, char *);
 129 extern void elevator_exit(elevator_t *);
 130 extern int elv_rq_merge_ok(struct request *, struct bio *);
 131
 132 /*
 133  * Helper functions.
 134  */
 135 extern struct request *elv_rb_former_request(request_queue_t *, struct request *);
 136 extern struct request *elv_rb_latter_request(request_queue_t *, struct request *);
 137
 138 /*
 139  * rb support functions.
 140  */
 141 extern struct request *elv_rb_add(struct rb_root *, struct request *);
 142 extern void elv_rb_del(struct rb_root *, struct request *);
 143 extern struct request *elv_rb_find(struct rb_root *, sector_t);
 144
 145 /*
 146  * Return values from elevator merger
 147  */
 148 #define ELEVATOR_NO_MERGE       0
 149 #define ELEVATOR_FRONT_MERGE    1
 150 #define ELEVATOR_BACK_MERGE     2
 151
 152 /*
 153  * Insertion selection
 154  */
 155 #define ELEVATOR_INSERT_FRONT   1
 156 #define ELEVATOR_INSERT_BACK    2
 157 #define ELEVATOR_INSERT_SORT    3
 158 #define ELEVATOR_INSERT_REQUEUE 4
 159
 160 /*
 161  * return values from elevator_may_queue_fn
 162  */
 163 enum {
 164         ELV_MQUEUE_MAY,
 165         ELV_MQUEUE_NO,
 166         ELV_MQUEUE_MUST,
 167 };
 168
 169 #define rq_end_sector(rq)       ((rq)->sector + (rq)->nr_sectors)
 170 #if 0   // mask by Victor Yu. 02-12-2007
 171 #define rb_entry_rq(node)       rb_entry((node), struct request, rb_node)
 172 #else
 173 #define rb_entry_rq(node)       rb_entry((node), struct request, u.rb_node)
 174 #endif
 175
 176 /*
 177  * Hack to reuse the donelist list_head as the fifo time holder while
 178  * the request is in the io scheduler. Saves an unsigned long in rq.
 179  */
 180 #define rq_fifo_time(rq)        ((unsigned long) (rq)->donelist.next)
 181 #define rq_set_fifo_time(rq,exp)        ((rq)->donelist.next = (void *) (exp))
 182 #define rq_entry_fifo(ptr)      list_entry((ptr), struct request, queuelist)
 183 #define rq_fifo_clear(rq)       do {            \
 184         list_del_init(&(rq)->queuelist);        \
 185         INIT_LIST_HEAD(&(rq)->donelist);        \
 186         } while (0)
 187
 188 /*
 189  * io context count accounting
 190  */
 191 #define elv_ioc_count_mod(name, __val)                          \
 192         do {                                                    \
 193                 preempt_disable();                              \
 194                 __get_cpu_var(name) += (__val);                 \
 195                 preempt_enable();                               \
 196         } while (0)
 197
 198 #define elv_ioc_count_inc(name) elv_ioc_count_mod(name, 1)
 199 #define elv_ioc_count_dec(name) elv_ioc_count_mod(name, -1)
 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