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/slab.h>
9#include <linux/init.h>
10
11struct noop_data {
12 struct list_head queue;
13};
14
15static void noop_merged_requests(struct request_queue *q, struct request *rq,
16 struct request *next)
17{
18 list_del_init(&next->queuelist);
19}
20
21static 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
35static 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
42static struct request *
43noop_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
52static struct request *
53noop_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
62static void *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 NULL;
69 INIT_LIST_HEAD(&nd->queue);
70 return nd;
71}
72
73static void noop_exit_queue(struct elevator_queue *e)
74{
75 struct noop_data *nd = e->elevator_data;
76
77 BUG_ON(!list_empty(&nd->queue));
78 kfree(nd);
79}
80
81static struct elevator_type elevator_noop = {
82 .ops = {
83 .elevator_merge_req_fn = noop_merged_requests,
84 .elevator_dispatch_fn = noop_dispatch,
85 .elevator_add_req_fn = noop_add_request,
86 .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,
90 },
91 .elevator_name = "noop",
92 .elevator_owner = THIS_MODULE,
93};
94
95static int __init noop_init(void)
96{
97 return elv_register(&elevator_noop);
98}
99
100static void __exit noop_exit(void)
101{
102 elv_unregister(&elevator_noop);
103}
104
105module_init(noop_init);
106module_exit(noop_exit);
107
108
109MODULE_AUTHOR("Jens Axboe");
110MODULE_LICENSE("GPL");
111MODULE_DESCRIPTION("No-op IO scheduler");