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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 | struct request *rq; | |
25 | ||
26 | rq = list_first_entry_or_null(&nd->queue, struct request, queuelist); | |
27 | if (rq) { | |
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 struct request * | |
43 | noop_former_request(struct request_queue *q, struct request *rq) | |
44 | { | |
45 | struct noop_data *nd = q->elevator->elevator_data; | |
46 | ||
47 | if (rq->queuelist.prev == &nd->queue) | |
48 | return NULL; | |
49 | return list_prev_entry(rq, queuelist); | |
50 | } | |
51 | ||
52 | static struct request * | |
53 | noop_latter_request(struct request_queue *q, struct request *rq) | |
54 | { | |
55 | struct noop_data *nd = q->elevator->elevator_data; | |
56 | ||
57 | if (rq->queuelist.next == &nd->queue) | |
58 | return NULL; | |
59 | return list_next_entry(rq, queuelist); | |
60 | } | |
61 | ||
62 | static int noop_init_queue(struct request_queue *q, struct elevator_type *e) | |
63 | { | |
64 | struct noop_data *nd; | |
65 | struct elevator_queue *eq; | |
66 | ||
67 | eq = elevator_alloc(q, e); | |
68 | if (!eq) | |
69 | return -ENOMEM; | |
70 | ||
71 | nd = kmalloc_node(sizeof(*nd), GFP_KERNEL, q->node); | |
72 | if (!nd) { | |
73 | kobject_put(&eq->kobj); | |
74 | return -ENOMEM; | |
75 | } | |
76 | eq->elevator_data = nd; | |
77 | ||
78 | INIT_LIST_HEAD(&nd->queue); | |
79 | ||
80 | spin_lock_irq(q->queue_lock); | |
81 | q->elevator = eq; | |
82 | spin_unlock_irq(q->queue_lock); | |
83 | return 0; | |
84 | } | |
85 | ||
86 | static void noop_exit_queue(struct elevator_queue *e) | |
87 | { | |
88 | struct noop_data *nd = e->elevator_data; | |
89 | ||
90 | BUG_ON(!list_empty(&nd->queue)); | |
91 | kfree(nd); | |
92 | } | |
93 | ||
94 | static struct elevator_type elevator_noop = { | |
95 | .ops.sq = { | |
96 | .elevator_merge_req_fn = noop_merged_requests, | |
97 | .elevator_dispatch_fn = noop_dispatch, | |
98 | .elevator_add_req_fn = noop_add_request, | |
99 | .elevator_former_req_fn = noop_former_request, | |
100 | .elevator_latter_req_fn = noop_latter_request, | |
101 | .elevator_init_fn = noop_init_queue, | |
102 | .elevator_exit_fn = noop_exit_queue, | |
103 | }, | |
104 | .elevator_name = "noop", | |
105 | .elevator_owner = THIS_MODULE, | |
106 | }; | |
107 | ||
108 | static int __init noop_init(void) | |
109 | { | |
110 | return elv_register(&elevator_noop); | |
111 | } | |
112 | ||
113 | static void __exit noop_exit(void) | |
114 | { | |
115 | elv_unregister(&elevator_noop); | |
116 | } | |
117 | ||
118 | module_init(noop_init); | |
119 | module_exit(noop_exit); | |
120 | ||
121 | ||
122 | MODULE_AUTHOR("Jens Axboe"); | |
123 | MODULE_LICENSE("GPL"); | |
124 | MODULE_DESCRIPTION("No-op IO scheduler"); |