HWPOISON: Export some rmap vma locking to outside world
[linux-2.6/linux-2.6-openrd.git] / block / noop-iosched.c
blob3a0d369d08c7488f8f475091ef3ee6b5dfe46211
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>
10 struct noop_data {
11 struct list_head queue;
14 static void noop_merged_requests(struct request_queue *q, struct request *rq,
15 struct request *next)
17 list_del_init(&next->queuelist);
20 static int noop_dispatch(struct request_queue *q, int force)
22 struct noop_data *nd = q->elevator->elevator_data;
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;
31 return 0;
34 static void noop_add_request(struct request_queue *q, struct request *rq)
36 struct noop_data *nd = q->elevator->elevator_data;
38 list_add_tail(&rq->queuelist, &nd->queue);
41 static int noop_queue_empty(struct request_queue *q)
43 struct noop_data *nd = q->elevator->elevator_data;
45 return list_empty(&nd->queue);
48 static struct request *
49 noop_former_request(struct request_queue *q, struct request *rq)
51 struct noop_data *nd = q->elevator->elevator_data;
53 if (rq->queuelist.prev == &nd->queue)
54 return NULL;
55 return list_entry(rq->queuelist.prev, struct request, queuelist);
58 static struct request *
59 noop_latter_request(struct request_queue *q, struct request *rq)
61 struct noop_data *nd = q->elevator->elevator_data;
63 if (rq->queuelist.next == &nd->queue)
64 return NULL;
65 return list_entry(rq->queuelist.next, struct request, queuelist);
68 static void *noop_init_queue(struct request_queue *q)
70 struct noop_data *nd;
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;
79 static void noop_exit_queue(struct elevator_queue *e)
81 struct noop_data *nd = e->elevator_data;
83 BUG_ON(!list_empty(&nd->queue));
84 kfree(nd);
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,
98 .elevator_name = "noop",
99 .elevator_owner = THIS_MODULE,
102 static int __init noop_init(void)
104 elv_register(&elevator_noop);
106 return 0;
109 static void __exit noop_exit(void)
111 elv_unregister(&elevator_noop);
114 module_init(noop_init);
115 module_exit(noop_exit);
118 MODULE_AUTHOR("Jens Axboe");
119 MODULE_LICENSE("GPL");
120 MODULE_DESCRIPTION("No-op IO scheduler");