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