tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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>
9
10struct noop_data {
11 struct list_head queue;
12};
13
14static void noop_merged_requests(struct request_queue *q, struct request *rq,
15 struct request *next)
16{
17 list_del_init(&next->queuelist);
18}
19
20static int noop_dispatch(struct request_queue *q, int force)
21{
22 struct noop_data *nd = q->elevator->elevator_data;
23
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;
30 }
31 return 0;
32}
33
34static void noop_add_request(struct request_queue *q, struct request *rq)
35{
36 struct noop_data *nd = q->elevator->elevator_data;
37
38 list_add_tail(&rq->queuelist, &nd->queue);
39}
40
41static int noop_queue_empty(struct request_queue *q)
42{
43 struct noop_data *nd = q->elevator->elevator_data;
44
45 return list_empty(&nd->queue);
46}
47
48static struct request *
49noop_former_request(struct request_queue *q, struct request *rq)
50{
51 struct noop_data *nd = q->elevator->elevator_data;
52
53 if (rq->queuelist.prev == &nd->queue)
54 return NULL;
55 return list_entry(rq->queuelist.prev, struct request, queuelist);
56}
57
58static struct request *
59noop_latter_request(struct request_queue *q, struct request *rq)
60{
61 struct noop_data *nd = q->elevator->elevator_data;
62
63 if (rq->queuelist.next == &nd->queue)
64 return NULL;
65 return list_entry(rq->queuelist.next, struct request, queuelist);
66}
67
68static void *noop_init_queue(struct request_queue *q)
69{
70 struct noop_data *nd;
71
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;
77}
78
79static void noop_exit_queue(elevator_t *e)
80{
81 struct noop_data *nd = e->elevator_data;
82
83 BUG_ON(!list_empty(&nd->queue));
84 kfree(nd);
85}
86
87static 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,
97 },
98 .elevator_name = "noop",
99 .elevator_owner = THIS_MODULE,
100};
101
102static int __init noop_init(void)
103{
104 return elv_register(&elevator_noop);
105}
106
107static void __exit noop_exit(void)
108{
109 elv_unregister(&elevator_noop);
110}
111
112module_init(noop_init);
113module_exit(noop_exit);
114
115
116MODULE_AUTHOR("Jens Axboe");
117MODULE_LICENSE("GPL");
118MODULE_DESCRIPTION("No-op IO scheduler");