cfq-iosched: More renaming to better represent wl_class and wl_type
[linux-3.10.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 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_entry(rq->queuelist.prev, struct request, 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_entry(rq->queuelist.next, struct request, queuelist);
60 }
61
62 static int noop_init_queue(struct request_queue *q)
63 {
64         struct noop_data *nd;
65
66         nd = kmalloc_node(sizeof(*nd), GFP_KERNEL, q->node);
67         if (!nd)
68                 return -ENOMEM;
69
70         INIT_LIST_HEAD(&nd->queue);
71         q->elevator->elevator_data = nd;
72         return 0;
73 }
74
75 static void noop_exit_queue(struct elevator_queue *e)
76 {
77         struct noop_data *nd = e->elevator_data;
78
79         BUG_ON(!list_empty(&nd->queue));
80         kfree(nd);
81 }
82
83 static struct elevator_type elevator_noop = {
84         .ops = {
85                 .elevator_merge_req_fn          = noop_merged_requests,
86                 .elevator_dispatch_fn           = noop_dispatch,
87                 .elevator_add_req_fn            = noop_add_request,
88                 .elevator_former_req_fn         = noop_former_request,
89                 .elevator_latter_req_fn         = noop_latter_request,
90                 .elevator_init_fn               = noop_init_queue,
91                 .elevator_exit_fn               = noop_exit_queue,
92         },
93         .elevator_name = "noop",
94         .elevator_owner = THIS_MODULE,
95 };
96
97 static int __init noop_init(void)
98 {
99         return elv_register(&elevator_noop);
100 }
101
102 static void __exit noop_exit(void)
103 {
104         elv_unregister(&elevator_noop);
105 }
106
107 module_init(noop_init);
108 module_exit(noop_exit);
109
110
111 MODULE_AUTHOR("Jens Axboe");
112 MODULE_LICENSE("GPL");
113 MODULE_DESCRIPTION("No-op IO scheduler");