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tag: v2.6.15
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Octocat-spinner-32-eaf2f5

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/*
* elevator noop
*/
#include <linux/blkdev.h>
#include <linux/elevator.h>
#include <linux/bio.h>
#include <linux/module.h>
#include <linux/init.h>

struct noop_data {
struct list_head queue;
};

static void noop_merged_requests(request_queue_t *q, struct request *rq,
struct request *next)
{
list_del_init(&next->queuelist);
}

static int noop_dispatch(request_queue_t *q, int force)
{
struct noop_data *nd = q->elevator->elevator_data;

if (!list_empty(&nd->queue)) {
struct request *rq;
rq = list_entry(nd->queue.next, struct request, queuelist);
list_del_init(&rq->queuelist);
elv_dispatch_sort(q, rq);
return 1;
}
return 0;
}

static void noop_add_request(request_queue_t *q, struct request *rq)
{
struct noop_data *nd = q->elevator->elevator_data;

list_add_tail(&rq->queuelist, &nd->queue);
}

static int noop_queue_empty(request_queue_t *q)
{
struct noop_data *nd = q->elevator->elevator_data;

return list_empty(&nd->queue);
}

static struct request *
noop_former_request(request_queue_t *q, struct request *rq)
{
struct noop_data *nd = q->elevator->elevator_data;

if (rq->queuelist.prev == &nd->queue)
return NULL;
return list_entry(rq->queuelist.prev, struct request, queuelist);
}

static struct request *
noop_latter_request(request_queue_t *q, struct request *rq)
{
struct noop_data *nd = q->elevator->elevator_data;

if (rq->queuelist.next == &nd->queue)
return NULL;
return list_entry(rq->queuelist.next, struct request, queuelist);
}

static int noop_init_queue(request_queue_t *q, elevator_t *e)
{
struct noop_data *nd;

nd = kmalloc(sizeof(*nd), GFP_KERNEL);
if (!nd)
return -ENOMEM;
INIT_LIST_HEAD(&nd->queue);
e->elevator_data = nd;
return 0;
}

static void noop_exit_queue(elevator_t *e)
{
struct noop_data *nd = e->elevator_data;

BUG_ON(!list_empty(&nd->queue));
kfree(nd);
}

static struct elevator_type elevator_noop = {
.ops = {
.elevator_merge_req_fn = noop_merged_requests,
.elevator_dispatch_fn = noop_dispatch,
.elevator_add_req_fn = noop_add_request,
.elevator_queue_empty_fn = noop_queue_empty,
.elevator_former_req_fn = noop_former_request,
.elevator_latter_req_fn = noop_latter_request,
.elevator_init_fn = noop_init_queue,
.elevator_exit_fn = noop_exit_queue,
},
.elevator_name = "noop",
.elevator_owner = THIS_MODULE,
};

static int __init noop_init(void)
{
return elv_register(&elevator_noop);
}

static void __exit noop_exit(void)
{
elv_unregister(&elevator_noop);
}

module_init(noop_init);
module_exit(noop_exit);


MODULE_AUTHOR("Jens Axboe");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("No-op IO scheduler");
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