Root/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/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(struct elevator_queue *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    elv_register(&elevator_noop);
105
106    return 0;
107}
108
109static void __exit noop_exit(void)
110{
111    elv_unregister(&elevator_noop);
112}
113
114module_init(noop_init);
115module_exit(noop_exit);
116
117
118MODULE_AUTHOR("Jens Axboe");
119MODULE_LICENSE("GPL");
120MODULE_DESCRIPTION("No-op IO scheduler");
121

Archive Download this file



interactive