include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit...
[linux-2.6.git] / block / noop-iosched.c
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");