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elevator.h
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1 #ifndef _LINUX_ELEVATOR_H
2 #define _LINUX_ELEVATOR_H
3 
4 #include <linux/percpu.h>
5 
6 #ifdef CONFIG_BLOCK
7 
8 struct io_cq;
9 
10 typedef int (elevator_merge_fn) (struct request_queue *, struct request **,
11  struct bio *);
12 
13 typedef void (elevator_merge_req_fn) (struct request_queue *, struct request *, struct request *);
14 
15 typedef void (elevator_merged_fn) (struct request_queue *, struct request *, int);
16 
17 typedef int (elevator_allow_merge_fn) (struct request_queue *, struct request *, struct bio *);
18 
19 typedef void (elevator_bio_merged_fn) (struct request_queue *,
20  struct request *, struct bio *);
21 
22 typedef int (elevator_dispatch_fn) (struct request_queue *, int);
23 
24 typedef void (elevator_add_req_fn) (struct request_queue *, struct request *);
25 typedef struct request *(elevator_request_list_fn) (struct request_queue *, struct request *);
26 typedef void (elevator_completed_req_fn) (struct request_queue *, struct request *);
27 typedef int (elevator_may_queue_fn) (struct request_queue *, int);
28 
29 typedef void (elevator_init_icq_fn) (struct io_cq *);
30 typedef void (elevator_exit_icq_fn) (struct io_cq *);
31 typedef int (elevator_set_req_fn) (struct request_queue *, struct request *,
32  struct bio *, gfp_t);
33 typedef void (elevator_put_req_fn) (struct request *);
34 typedef void (elevator_activate_req_fn) (struct request_queue *, struct request *);
35 typedef void (elevator_deactivate_req_fn) (struct request_queue *, struct request *);
36 
37 typedef int (elevator_init_fn) (struct request_queue *);
38 typedef void (elevator_exit_fn) (struct elevator_queue *);
39 
40 struct elevator_ops
41 {
42  elevator_merge_fn *elevator_merge_fn;
43  elevator_merged_fn *elevator_merged_fn;
44  elevator_merge_req_fn *elevator_merge_req_fn;
45  elevator_allow_merge_fn *elevator_allow_merge_fn;
46  elevator_bio_merged_fn *elevator_bio_merged_fn;
47 
48  elevator_dispatch_fn *elevator_dispatch_fn;
49  elevator_add_req_fn *elevator_add_req_fn;
50  elevator_activate_req_fn *elevator_activate_req_fn;
51  elevator_deactivate_req_fn *elevator_deactivate_req_fn;
52 
53  elevator_completed_req_fn *elevator_completed_req_fn;
54 
55  elevator_request_list_fn *elevator_former_req_fn;
56  elevator_request_list_fn *elevator_latter_req_fn;
57 
58  elevator_init_icq_fn *elevator_init_icq_fn; /* see iocontext.h */
59  elevator_exit_icq_fn *elevator_exit_icq_fn; /* ditto */
60 
61  elevator_set_req_fn *elevator_set_req_fn;
62  elevator_put_req_fn *elevator_put_req_fn;
63 
64  elevator_may_queue_fn *elevator_may_queue_fn;
65 
66  elevator_init_fn *elevator_init_fn;
67  elevator_exit_fn *elevator_exit_fn;
68 };
69 
70 #define ELV_NAME_MAX (16)
71 
72 struct elv_fs_entry {
73  struct attribute attr;
74  ssize_t (*show)(struct elevator_queue *, char *);
75  ssize_t (*store)(struct elevator_queue *, const char *, size_t);
76 };
77 
78 /*
79  * identifies an elevator type, such as AS or deadline
80  */
81 struct elevator_type
82 {
83  /* managed by elevator core */
84  struct kmem_cache *icq_cache;
85 
86  /* fields provided by elevator implementation */
87  struct elevator_ops ops;
88  size_t icq_size; /* see iocontext.h */
89  size_t icq_align; /* ditto */
90  struct elv_fs_entry *elevator_attrs;
91  char elevator_name[ELV_NAME_MAX];
92  struct module *elevator_owner;
93 
94  /* managed by elevator core */
95  char icq_cache_name[ELV_NAME_MAX + 5]; /* elvname + "_io_cq" */
96  struct list_head list;
97 };
98 
99 /*
100  * each queue has an elevator_queue associated with it
101  */
102 struct elevator_queue
103 {
104  struct elevator_type *type;
105  void *elevator_data;
106  struct kobject kobj;
107  struct mutex sysfs_lock;
108  struct hlist_head *hash;
109  unsigned int registered:1;
110 };
111 
112 /*
113  * block elevator interface
114  */
115 extern void elv_dispatch_sort(struct request_queue *, struct request *);
116 extern void elv_dispatch_add_tail(struct request_queue *, struct request *);
117 extern void elv_add_request(struct request_queue *, struct request *, int);
118 extern void __elv_add_request(struct request_queue *, struct request *, int);
119 extern int elv_merge(struct request_queue *, struct request **, struct bio *);
120 extern void elv_merge_requests(struct request_queue *, struct request *,
121  struct request *);
122 extern void elv_merged_request(struct request_queue *, struct request *, int);
123 extern void elv_bio_merged(struct request_queue *q, struct request *,
124  struct bio *);
125 extern void elv_requeue_request(struct request_queue *, struct request *);
126 extern struct request *elv_former_request(struct request_queue *, struct request *);
127 extern struct request *elv_latter_request(struct request_queue *, struct request *);
128 extern int elv_register_queue(struct request_queue *q);
129 extern void elv_unregister_queue(struct request_queue *q);
130 extern int elv_may_queue(struct request_queue *, int);
131 extern void elv_abort_queue(struct request_queue *);
132 extern void elv_completed_request(struct request_queue *, struct request *);
133 extern int elv_set_request(struct request_queue *q, struct request *rq,
134  struct bio *bio, gfp_t gfp_mask);
135 extern void elv_put_request(struct request_queue *, struct request *);
136 extern void elv_drain_elevator(struct request_queue *);
137 
138 /*
139  * io scheduler registration
140  */
141 extern int elv_register(struct elevator_type *);
142 extern void elv_unregister(struct elevator_type *);
143 
144 /*
145  * io scheduler sysfs switching
146  */
147 extern ssize_t elv_iosched_show(struct request_queue *, char *);
148 extern ssize_t elv_iosched_store(struct request_queue *, const char *, size_t);
149 
150 extern int elevator_init(struct request_queue *, char *);
151 extern void elevator_exit(struct elevator_queue *);
152 extern int elevator_change(struct request_queue *, const char *);
153 extern bool elv_rq_merge_ok(struct request *, struct bio *);
154 
155 /*
156  * Helper functions.
157  */
158 extern struct request *elv_rb_former_request(struct request_queue *, struct request *);
159 extern struct request *elv_rb_latter_request(struct request_queue *, struct request *);
160 
161 /*
162  * rb support functions.
163  */
164 extern void elv_rb_add(struct rb_root *, struct request *);
165 extern void elv_rb_del(struct rb_root *, struct request *);
166 extern struct request *elv_rb_find(struct rb_root *, sector_t);
167 
168 /*
169  * Return values from elevator merger
170  */
171 #define ELEVATOR_NO_MERGE 0
172 #define ELEVATOR_FRONT_MERGE 1
173 #define ELEVATOR_BACK_MERGE 2
174 
175 /*
176  * Insertion selection
177  */
178 #define ELEVATOR_INSERT_FRONT 1
179 #define ELEVATOR_INSERT_BACK 2
180 #define ELEVATOR_INSERT_SORT 3
181 #define ELEVATOR_INSERT_REQUEUE 4
182 #define ELEVATOR_INSERT_FLUSH 5
183 #define ELEVATOR_INSERT_SORT_MERGE 6
184 
185 /*
186  * return values from elevator_may_queue_fn
187  */
188 enum {
189  ELV_MQUEUE_MAY,
190  ELV_MQUEUE_NO,
191  ELV_MQUEUE_MUST,
192 };
193 
194 #define rq_end_sector(rq) (blk_rq_pos(rq) + blk_rq_sectors(rq))
195 #define rb_entry_rq(node) rb_entry((node), struct request, rb_node)
196 
197 /*
198  * Hack to reuse the csd.list list_head as the fifo time holder while
199  * the request is in the io scheduler. Saves an unsigned long in rq.
200  */
201 #define rq_fifo_time(rq) ((unsigned long) (rq)->csd.list.next)
202 #define rq_set_fifo_time(rq,exp) ((rq)->csd.list.next = (void *) (exp))
203 #define rq_entry_fifo(ptr) list_entry((ptr), struct request, queuelist)
204 #define rq_fifo_clear(rq) do { \
205  list_del_init(&(rq)->queuelist); \
206  INIT_LIST_HEAD(&(rq)->csd.list); \
207  } while (0)
208 
209 #endif /* CONFIG_BLOCK */
210 #endif
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