mtd: spi-nor: Kill check with no effect
[sfrench/cifs-2.6.git] / 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/slab.h>
9 #include <linux/init.h>
10
11 struct noop_data {
12         struct list_head queue;
13 };
14
15 static void noop_merged_requests(struct request_queue *q, struct request *rq,
16                                  struct request *next)
17 {
18         list_del_init(&next->queuelist);
19 }
20
21 static int noop_dispatch(struct request_queue *q, int force)
22 {
23         struct noop_data *nd = q->elevator->elevator_data;
24         struct request *rq;
25
26         rq = list_first_entry_or_null(&nd->queue, struct request, queuelist);
27         if (rq) {
28                 list_del_init(&rq->queuelist);
29                 elv_dispatch_sort(q, rq);
30                 return 1;
31         }
32         return 0;
33 }
34
35 static 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
42 static struct request *
43 noop_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_prev_entry(rq, queuelist);
50 }
51
52 static struct request *
53 noop_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_next_entry(rq, queuelist);
60 }
61
62 static int noop_init_queue(struct request_queue *q, struct elevator_type *e)
63 {
64         struct noop_data *nd;
65         struct elevator_queue *eq;
66
67         eq = elevator_alloc(q, e);
68         if (!eq)
69                 return -ENOMEM;
70
71         nd = kmalloc_node(sizeof(*nd), GFP_KERNEL, q->node);
72         if (!nd) {
73                 kobject_put(&eq->kobj);
74                 return -ENOMEM;
75         }
76         eq->elevator_data = nd;
77
78         INIT_LIST_HEAD(&nd->queue);
79
80         spin_lock_irq(q->queue_lock);
81         q->elevator = eq;
82         spin_unlock_irq(q->queue_lock);
83         return 0;
84 }
85
86 static void noop_exit_queue(struct elevator_queue *e)
87 {
88         struct noop_data *nd = e->elevator_data;
89
90         BUG_ON(!list_empty(&nd->queue));
91         kfree(nd);
92 }
93
94 static struct elevator_type elevator_noop = {
95         .ops.sq = {
96                 .elevator_merge_req_fn          = noop_merged_requests,
97                 .elevator_dispatch_fn           = noop_dispatch,
98                 .elevator_add_req_fn            = noop_add_request,
99                 .elevator_former_req_fn         = noop_former_request,
100                 .elevator_latter_req_fn         = noop_latter_request,
101                 .elevator_init_fn               = noop_init_queue,
102                 .elevator_exit_fn               = noop_exit_queue,
103         },
104         .elevator_name = "noop",
105         .elevator_owner = THIS_MODULE,
106 };
107
108 static int __init noop_init(void)
109 {
110         return elv_register(&elevator_noop);
111 }
112
113 static void __exit noop_exit(void)
114 {
115         elv_unregister(&elevator_noop);
116 }
117
118 module_init(noop_init);
119 module_exit(noop_exit);
120
121
122 MODULE_AUTHOR("Jens Axboe");
123 MODULE_LICENSE("GPL");
124 MODULE_DESCRIPTION("No-op IO scheduler");