blob: 06389e9ef96d552836a1509ddf86745d82c09762 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * elevator noop
3 */
4#include <linux/blkdev.h>
5#include <linux/elevator.h>
6#include <linux/bio.h>
7#include <linux/module.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +09008#include <linux/slab.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -07009#include <linux/init.h>
10
Tejun Heo5a7c47e2005-11-10 18:21:30 +010011struct noop_data {
12 struct list_head queue;
13};
14
Jens Axboe165125e2007-07-24 09:28:11 +020015static void noop_merged_requests(struct request_queue *q, struct request *rq,
Tejun Heo5a7c47e2005-11-10 18:21:30 +010016 struct request *next)
Linus Torvalds1da177e2005-04-16 15:20:36 -070017{
Tejun Heo5a7c47e2005-11-10 18:21:30 +010018 list_del_init(&next->queuelist);
Linus Torvalds1da177e2005-04-16 15:20:36 -070019}
20
Jens Axboe165125e2007-07-24 09:28:11 +020021static int noop_dispatch(struct request_queue *q, int force)
Linus Torvalds1da177e2005-04-16 15:20:36 -070022{
Tejun Heo5a7c47e2005-11-10 18:21:30 +010023 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 }
Jens Axboeb4878f22005-10-20 16:42:29 +020032 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -070033}
34
Jens Axboe165125e2007-07-24 09:28:11 +020035static void noop_add_request(struct request_queue *q, struct request *rq)
Tejun Heo5a7c47e2005-11-10 18:21:30 +010036{
37 struct noop_data *nd = q->elevator->elevator_data;
38
39 list_add_tail(&rq->queuelist, &nd->queue);
40}
41
Tejun Heo5a7c47e2005-11-10 18:21:30 +010042static struct request *
Jens Axboe165125e2007-07-24 09:28:11 +020043noop_former_request(struct request_queue *q, struct request *rq)
Tejun Heo5a7c47e2005-11-10 18:21:30 +010044{
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
52static struct request *
Jens Axboe165125e2007-07-24 09:28:11 +020053noop_latter_request(struct request_queue *q, struct request *rq)
Tejun Heo5a7c47e2005-11-10 18:21:30 +010054{
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
Jens Axboe165125e2007-07-24 09:28:11 +020062static void *noop_init_queue(struct request_queue *q)
Tejun Heo5a7c47e2005-11-10 18:21:30 +010063{
64 struct noop_data *nd;
65
Jens Axboeb5deef92006-07-19 23:39:40 +020066 nd = kmalloc_node(sizeof(*nd), GFP_KERNEL, q->node);
Tejun Heo5a7c47e2005-11-10 18:21:30 +010067 if (!nd)
Jens Axboebc1c1162006-06-08 08:49:06 +020068 return NULL;
Tejun Heo5a7c47e2005-11-10 18:21:30 +010069 INIT_LIST_HEAD(&nd->queue);
Jens Axboebc1c1162006-06-08 08:49:06 +020070 return nd;
Tejun Heo5a7c47e2005-11-10 18:21:30 +010071}
72
Jens Axboeb374d182008-10-31 10:05:07 +010073static void noop_exit_queue(struct elevator_queue *e)
Tejun Heo5a7c47e2005-11-10 18:21:30 +010074{
75 struct noop_data *nd = e->elevator_data;
76
77 BUG_ON(!list_empty(&nd->queue));
78 kfree(nd);
79}
80
Linus Torvalds1da177e2005-04-16 15:20:36 -070081static struct elevator_type elevator_noop = {
82 .ops = {
Tejun Heo5a7c47e2005-11-10 18:21:30 +010083 .elevator_merge_req_fn = noop_merged_requests,
84 .elevator_dispatch_fn = noop_dispatch,
85 .elevator_add_req_fn = noop_add_request,
Tejun Heo5a7c47e2005-11-10 18:21:30 +010086 .elevator_former_req_fn = noop_former_request,
87 .elevator_latter_req_fn = noop_latter_request,
88 .elevator_init_fn = noop_init_queue,
89 .elevator_exit_fn = noop_exit_queue,
Linus Torvalds1da177e2005-04-16 15:20:36 -070090 },
91 .elevator_name = "noop",
92 .elevator_owner = THIS_MODULE,
93};
94
95static int __init noop_init(void)
96{
Adrian Bunk2fdd82b2007-12-12 18:51:56 +010097 elv_register(&elevator_noop);
98
99 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700100}
101
102static void __exit noop_exit(void)
103{
104 elv_unregister(&elevator_noop);
105}
106
107module_init(noop_init);
108module_exit(noop_exit);
109
110
111MODULE_AUTHOR("Jens Axboe");
112MODULE_LICENSE("GPL");
113MODULE_DESCRIPTION("No-op IO scheduler");