[linux.git] / block / noop-iosched.c

/*
 * 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");
Commit	Line	Data
1da177e4 LT	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
5a7c47ee TH	10	struct noop_data {
	11	struct list_head queue;
	12	};
	13
	14	static void noop_merged_requests(request_queue_t q, struct request rq,
	15	struct request *next)
	16	{
	17	list_del_init(&next->queuelist);
	18	}
	19
	20	static int noop_dispatch(request_queue_t *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
	34	static void noop_add_request(request_queue_t 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
	41	static int noop_queue_empty(request_queue_t *q)
1da177e4	42	{
5a7c47ee TH	43	struct noop_data *nd = q->elevator->elevator_data;
	44
	45	return list_empty(&nd->queue);
	46	}
	47
	48	static struct request *
	49	noop_former_request(request_queue_t 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
	58	static struct request *
	59	noop_latter_request(request_queue_t 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);
1da177e4 LT	66	}
1da177e4 LT	67
5a7c47ee	68	static int noop_init_queue(request_queue_t q, elevator_t e)
1da177e4	69	{
5a7c47ee TH	70	struct noop_data *nd;
	71
	72	nd = kmalloc(sizeof(*nd), GFP_KERNEL);
	73	if (!nd)
	74	return -ENOMEM;
	75	INIT_LIST_HEAD(&nd->queue);
	76	e->elevator_data = nd;
b4878f24	77	return 0;
1da177e4 LT	78	}
1da177e4 LT	79
5a7c47ee TH	80	static void noop_exit_queue(elevator_t *e)
	81	{
	82	struct noop_data *nd = e->elevator_data;
	83
	84	BUG_ON(!list_empty(&nd->queue));
	85	kfree(nd);
	86	}
	87
1da177e4 LT	88	static struct elevator_type elevator_noop = {
1da177e4 LT	89	.ops = {
5a7c47ee TH	90	.elevator_merge_req_fn = noop_merged_requests,
	91	.elevator_dispatch_fn = noop_dispatch,
	92	.elevator_add_req_fn = noop_add_request,
	93	.elevator_queue_empty_fn = noop_queue_empty,
	94	.elevator_former_req_fn = noop_former_request,
	95	.elevator_latter_req_fn = noop_latter_request,
	96	.elevator_init_fn = noop_init_queue,
	97	.elevator_exit_fn = noop_exit_queue,
1da177e4 LT	98	},
	99	.elevator_name = "noop",
	100	.elevator_owner = THIS_MODULE,
	101	};
	102
	103	static int __init noop_init(void)
	104	{
	105	return elv_register(&elevator_noop);
	106	}
	107
	108	static void __exit noop_exit(void)
	109	{
	110	elv_unregister(&elevator_noop);
	111	}
	112
	113	module_init(noop_init);
	114	module_exit(noop_exit);
	115
	116
	117	MODULE_AUTHOR("Jens Axboe");
	118	MODULE_LICENSE("GPL");
	119	MODULE_DESCRIPTION("No-op IO scheduler");