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1 | /* |
2 | * elevator noop |
3 | */ |
4 | #include <linux/blkdev.h> |
5 | #include <linux/elevator.h> |
6 | #include <linux/bio.h> |
7 | #include <linux/module.h> |
8 | #include <linux/init.h> |
9 | |
10 | struct noop_data { |
11 | struct list_head queue; |
12 | }; |
13 | |
14 | static void noop_merged_requests(struct request_queue *q, struct request *rq, |
15 | struct request *next) |
16 | { |
17 | list_del_init(&next->queuelist); |
18 | } |
19 | |
20 | static int noop_dispatch(struct request_queue *q, int force) |
21 | { |
22 | struct noop_data *nd = q->elevator->elevator_data; |
23 | |
24 | if (!list_empty(&nd->queue)) { |
25 | struct request *rq; |
26 | rq = list_entry(nd->queue.next, struct request, queuelist); |
27 | list_del_init(&rq->queuelist); |
28 | elv_dispatch_sort(q, rq); |
29 | return 1; |
30 | } |
31 | return 0; |
32 | } |
33 | |
34 | static void noop_add_request(struct request_queue *q, struct request *rq) |
35 | { |
36 | struct noop_data *nd = q->elevator->elevator_data; |
37 | |
38 | list_add_tail(&rq->queuelist, &nd->queue); |
39 | } |
40 | |
41 | static int noop_queue_empty(struct request_queue *q) |
42 | { |
43 | struct noop_data *nd = q->elevator->elevator_data; |
44 | |
45 | return list_empty(&nd->queue); |
46 | } |
47 | |
48 | static struct request * |
49 | noop_former_request(struct request_queue *q, struct request *rq) |
50 | { |
51 | struct noop_data *nd = q->elevator->elevator_data; |
52 | |
53 | if (rq->queuelist.prev == &nd->queue) |
54 | return NULL; |
55 | return list_entry(rq->queuelist.prev, struct request, queuelist); |
56 | } |
57 | |
58 | static struct request * |
59 | noop_latter_request(struct request_queue *q, struct request *rq) |
60 | { |
61 | struct noop_data *nd = q->elevator->elevator_data; |
62 | |
63 | if (rq->queuelist.next == &nd->queue) |
64 | return NULL; |
65 | return list_entry(rq->queuelist.next, struct request, queuelist); |
66 | } |
67 | |
68 | static void *noop_init_queue(struct request_queue *q) |
69 | { |
70 | struct noop_data *nd; |
71 | |
72 | nd = kmalloc_node(sizeof(*nd), GFP_KERNEL, q->node); |
73 | if (!nd) |
74 | return NULL; |
75 | INIT_LIST_HEAD(&nd->queue); |
76 | return nd; |
77 | } |
78 | |
79 | static void noop_exit_queue(struct elevator_queue *e) |
80 | { |
81 | struct noop_data *nd = e->elevator_data; |
82 | |
83 | BUG_ON(!list_empty(&nd->queue)); |
84 | kfree(nd); |
85 | } |
86 | |
87 | static struct elevator_type elevator_noop = { |
88 | .ops = { |
89 | .elevator_merge_req_fn = noop_merged_requests, |
90 | .elevator_dispatch_fn = noop_dispatch, |
91 | .elevator_add_req_fn = noop_add_request, |
92 | .elevator_queue_empty_fn = noop_queue_empty, |
93 | .elevator_former_req_fn = noop_former_request, |
94 | .elevator_latter_req_fn = noop_latter_request, |
95 | .elevator_init_fn = noop_init_queue, |
96 | .elevator_exit_fn = noop_exit_queue, |
97 | }, |
98 | .elevator_name = "noop", |
99 | .elevator_owner = THIS_MODULE, |
100 | }; |
101 | |
102 | static int __init noop_init(void) |
103 | { |
104 | elv_register(&elevator_noop); |
105 | |
106 | return 0; |
107 | } |
108 | |
109 | static void __exit noop_exit(void) |
110 | { |
111 | elv_unregister(&elevator_noop); |
112 | } |
113 | |
114 | module_init(noop_init); |
115 | module_exit(noop_exit); |
116 | |
117 | |
118 | MODULE_AUTHOR("Jens Axboe"); |
119 | MODULE_LICENSE("GPL"); |
120 | MODULE_DESCRIPTION("No-op IO scheduler"); |
121 |
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Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
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