[mirror_ubuntu-artful-kernel.git] / block / deadline-iosched.c

/*
 *  Deadline i/o scheduler.
 *
 *  Copyright (C) 2002 Jens Axboe <axboe@kernel.dk>
 */
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/blkdev.h>
#include <linux/elevator.h>
#include <linux/bio.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/compiler.h>
#include <linux/rbtree.h>

/*
 * See Documentation/block/deadline-iosched.txt
 */
static const int read_expire = HZ / 2;  /* max time before a read is submitted. */
static const int write_expire = 5 * HZ; /* ditto for writes, these limits are SOFT! */
static const int writes_starved = 2;    /* max times reads can starve a write */
static const int fifo_batch = 16;       /* # of sequential requests treated as one
				     by the above parameters. For throughput. */

struct deadline_data {
	/*
	 * run time data
	 */

	/*
	 * requests (deadline_rq s) are present on both sort_list and fifo_list
	 */
	struct rb_root sort_list[2];	
	struct list_head fifo_list[2];

	/*
	 * next in sort order. read, write or both are NULL
	 */
	struct request *next_rq[2];
	unsigned int batching;		/* number of sequential requests made */
	unsigned int starved;		/* times reads have starved writes */

	/*
	 * settings that change how the i/o scheduler behaves
	 */
	int fifo_expire[2];
	int fifo_batch;
	int writes_starved;
	int front_merges;
};

static void deadline_move_request(struct deadline_data *, struct request *);

static inline struct rb_root *
deadline_rb_root(struct deadline_data *dd, struct request *rq)
{
	return &dd->sort_list[rq_data_dir(rq)];
}

/*
 * get the request after `rq' in sector-sorted order
 */
static inline struct request *
deadline_latter_request(struct request *rq)
{
	struct rb_node *node = rb_next(&rq->rb_node);

	if (node)
		return rb_entry_rq(node);

	return NULL;
}

static void
deadline_add_rq_rb(struct deadline_data *dd, struct request *rq)
{
	struct rb_root *root = deadline_rb_root(dd, rq);

	elv_rb_add(root, rq);
}

static inline void
deadline_del_rq_rb(struct deadline_data *dd, struct request *rq)
{
	const int data_dir = rq_data_dir(rq);

	if (dd->next_rq[data_dir] == rq)
		dd->next_rq[data_dir] = deadline_latter_request(rq);

	elv_rb_del(deadline_rb_root(dd, rq), rq);
}

/*
 * add rq to rbtree and fifo
 */
static void
deadline_add_request(struct request_queue *q, struct request *rq)
{
	struct deadline_data *dd = q->elevator->elevator_data;
	const int data_dir = rq_data_dir(rq);

	deadline_add_rq_rb(dd, rq);

	/*
	 * set expire time and add to fifo list
	 */
	rq->fifo_time = jiffies + dd->fifo_expire[data_dir];
	list_add_tail(&rq->queuelist, &dd->fifo_list[data_dir]);
}

/*
 * remove rq from rbtree and fifo.
 */
static void deadline_remove_request(struct request_queue *q, struct request *rq)
{
	struct deadline_data *dd = q->elevator->elevator_data;

	rq_fifo_clear(rq);
	deadline_del_rq_rb(dd, rq);
}

static enum elv_merge
deadline_merge(struct request_queue *q, struct request **req, struct bio *bio)
{
	struct deadline_data *dd = q->elevator->elevator_data;
	struct request *__rq;

	/*
	 * check for front merge
	 */
	if (dd->front_merges) {
		sector_t sector = bio_end_sector(bio);

		__rq = elv_rb_find(&dd->sort_list[bio_data_dir(bio)], sector);
		if (__rq) {
			BUG_ON(sector != blk_rq_pos(__rq));

			if (elv_bio_merge_ok(__rq, bio)) {
				*req = __rq;
				return ELEVATOR_FRONT_MERGE;
			}
		}
	}

	return ELEVATOR_NO_MERGE;
}

static void deadline_merged_request(struct request_queue *q,
				    struct request *req, enum elv_merge type)
{
	struct deadline_data *dd = q->elevator->elevator_data;

	/*
	 * if the merge was a front merge, we need to reposition request
	 */
	if (type == ELEVATOR_FRONT_MERGE) {
		elv_rb_del(deadline_rb_root(dd, req), req);
		deadline_add_rq_rb(dd, req);
	}
}

static void
deadline_merged_requests(struct request_queue *q, struct request *req,
			 struct request *next)
{
	/*
	 * if next expires before rq, assign its expire time to rq
	 * and move into next position (next will be deleted) in fifo
	 */
	if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) {
		if (time_before((unsigned long)next->fifo_time,
				(unsigned long)req->fifo_time)) {
			list_move(&req->queuelist, &next->queuelist);
			req->fifo_time = next->fifo_time;
		}
	}

	/*
	 * kill knowledge of next, this one is a goner
	 */
	deadline_remove_request(q, next);
}

/*
 * move request from sort list to dispatch queue.
 */
static inline void
deadline_move_to_dispatch(struct deadline_data *dd, struct request *rq)
{
	struct request_queue *q = rq->q;

	deadline_remove_request(q, rq);
	elv_dispatch_add_tail(q, rq);
}

/*
 * move an entry to dispatch queue
 */
static void
deadline_move_request(struct deadline_data *dd, struct request *rq)
{
	const int data_dir = rq_data_dir(rq);

	dd->next_rq[READ] = NULL;
	dd->next_rq[WRITE] = NULL;
	dd->next_rq[data_dir] = deadline_latter_request(rq);

	/*
	 * take it off the sort and fifo list, move
	 * to dispatch queue
	 */
	deadline_move_to_dispatch(dd, rq);
}

/*
 * deadline_check_fifo returns 0 if there are no expired requests on the fifo,
 * 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
 */
static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
{
	struct request *rq = rq_entry_fifo(dd->fifo_list[ddir].next);

	/*
	 * rq is expired!
	 */
	if (time_after_eq(jiffies, (unsigned long)rq->fifo_time))
		return 1;

	return 0;
}

/*
 * deadline_dispatch_requests selects the best request according to
 * read/write expire, fifo_batch, etc
 */
static int deadline_dispatch_requests(struct request_queue *q, int force)
{
	struct deadline_data *dd = q->elevator->elevator_data;
	const int reads = !list_empty(&dd->fifo_list[READ]);
	const int writes = !list_empty(&dd->fifo_list[WRITE]);
	struct request *rq;
	int data_dir;

	/*
	 * batches are currently reads XOR writes
	 */
	if (dd->next_rq[WRITE])
		rq = dd->next_rq[WRITE];
	else
		rq = dd->next_rq[READ];

	if (rq && dd->batching < dd->fifo_batch)
		/* we have a next request are still entitled to batch */
		goto dispatch_request;

	/*
	 * at this point we are not running a batch. select the appropriate
	 * data direction (read / write)
	 */

	if (reads) {
		BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[READ]));

		if (writes && (dd->starved++ >= dd->writes_starved))
			goto dispatch_writes;

		data_dir = READ;

		goto dispatch_find_request;
	}

	/*
	 * there are either no reads or writes have been starved
	 */

	if (writes) {
dispatch_writes:
		BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[WRITE]));

		dd->starved = 0;

		data_dir = WRITE;

		goto dispatch_find_request;
	}

	return 0;

dispatch_find_request:
	/*
	 * we are not running a batch, find best request for selected data_dir
	 */
	if (deadline_check_fifo(dd, data_dir) || !dd->next_rq[data_dir]) {
		/*
		 * A deadline has expired, the last request was in the other
		 * direction, or we have run out of higher-sectored requests.
		 * Start again from the request with the earliest expiry time.
		 */
		rq = rq_entry_fifo(dd->fifo_list[data_dir].next);
	} else {
		/*
		 * The last req was the same dir and we have a next request in
		 * sort order. No expired requests so continue on from here.
		 */
		rq = dd->next_rq[data_dir];
	}

	dd->batching = 0;

dispatch_request:
	/*
	 * rq is the selected appropriate request.
	 */
	dd->batching++;
	deadline_move_request(dd, rq);

	return 1;
}

static void deadline_exit_queue(struct elevator_queue *e)
{
	struct deadline_data *dd = e->elevator_data;

	BUG_ON(!list_empty(&dd->fifo_list[READ]));
	BUG_ON(!list_empty(&dd->fifo_list[WRITE]));

	kfree(dd);
}

/*
 * initialize elevator private data (deadline_data).
 */
static int deadline_init_queue(struct request_queue *q, struct elevator_type *e)
{
	struct deadline_data *dd;
	struct elevator_queue *eq;

	eq = elevator_alloc(q, e);
	if (!eq)
		return -ENOMEM;

	dd = kzalloc_node(sizeof(*dd), GFP_KERNEL, q->node);
	if (!dd) {
		kobject_put(&eq->kobj);
		return -ENOMEM;
	}
	eq->elevator_data = dd;

	INIT_LIST_HEAD(&dd->fifo_list[READ]);
	INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
	dd->sort_list[READ] = RB_ROOT;
	dd->sort_list[WRITE] = RB_ROOT;
	dd->fifo_expire[READ] = read_expire;
	dd->fifo_expire[WRITE] = write_expire;
	dd->writes_starved = writes_starved;
	dd->front_merges = 1;
	dd->fifo_batch = fifo_batch;

	spin_lock_irq(q->queue_lock);
	q->elevator = eq;
	spin_unlock_irq(q->queue_lock);
	return 0;
}

/*
 * sysfs parts below
 */

static ssize_t
deadline_var_show(int var, char *page)
{
	return sprintf(page, "%d\n", var);
}

static ssize_t
deadline_var_store(int *var, const char *page, size_t count)
{
	char *p = (char *) page;

	*var = simple_strtol(p, &p, 10);
	return count;
}

#define SHOW_FUNCTION(__FUNC, __VAR, __CONV)				\
static ssize_t __FUNC(struct elevator_queue *e, char *page)		\
{									\
	struct deadline_data *dd = e->elevator_data;			\
	int __data = __VAR;						\
	if (__CONV)							\
		__data = jiffies_to_msecs(__data);			\
	return deadline_var_show(__data, (page));			\
}
SHOW_FUNCTION(deadline_read_expire_show, dd->fifo_expire[READ], 1);
SHOW_FUNCTION(deadline_write_expire_show, dd->fifo_expire[WRITE], 1);
SHOW_FUNCTION(deadline_writes_starved_show, dd->writes_starved, 0);
SHOW_FUNCTION(deadline_front_merges_show, dd->front_merges, 0);
SHOW_FUNCTION(deadline_fifo_batch_show, dd->fifo_batch, 0);
#undef SHOW_FUNCTION

#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)			\
static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count)	\
{									\
	struct deadline_data *dd = e->elevator_data;			\
	int __data;							\
	int ret = deadline_var_store(&__data, (page), count);		\
	if (__data < (MIN))						\
		__data = (MIN);						\
	else if (__data > (MAX))					\
		__data = (MAX);						\
	if (__CONV)							\
		*(__PTR) = msecs_to_jiffies(__data);			\
	else								\
		*(__PTR) = __data;					\
	return ret;							\
}
STORE_FUNCTION(deadline_read_expire_store, &dd->fifo_expire[READ], 0, INT_MAX, 1);
STORE_FUNCTION(deadline_write_expire_store, &dd->fifo_expire[WRITE], 0, INT_MAX, 1);
STORE_FUNCTION(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX, 0);
STORE_FUNCTION(deadline_front_merges_store, &dd->front_merges, 0, 1, 0);
STORE_FUNCTION(deadline_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX, 0);
#undef STORE_FUNCTION

#define DD_ATTR(name) \
	__ATTR(name, S_IRUGO|S_IWUSR, deadline_##name##_show, \
				      deadline_##name##_store)

static struct elv_fs_entry deadline_attrs[] = {
	DD_ATTR(read_expire),
	DD_ATTR(write_expire),
	DD_ATTR(writes_starved),
	DD_ATTR(front_merges),
	DD_ATTR(fifo_batch),
	__ATTR_NULL
};

static struct elevator_type iosched_deadline = {
	.ops.sq = {
		.elevator_merge_fn = 		deadline_merge,
		.elevator_merged_fn =		deadline_merged_request,
		.elevator_merge_req_fn =	deadline_merged_requests,
		.elevator_dispatch_fn =		deadline_dispatch_requests,
		.elevator_add_req_fn =		deadline_add_request,
		.elevator_former_req_fn =	elv_rb_former_request,
		.elevator_latter_req_fn =	elv_rb_latter_request,
		.elevator_init_fn =		deadline_init_queue,
		.elevator_exit_fn =		deadline_exit_queue,
	},

	.elevator_attrs = deadline_attrs,
	.elevator_name = "deadline",
	.elevator_owner = THIS_MODULE,
};

static int __init deadline_init(void)
{
	return elv_register(&iosched_deadline);
}

static void __exit deadline_exit(void)
{
	elv_unregister(&iosched_deadline);
}

module_init(deadline_init);
module_exit(deadline_exit);

MODULE_AUTHOR("Jens Axboe");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("deadline IO scheduler");
Commit	Line	Data
1da177e4	1	/*
1da177e4 LT	2	* Deadline i/o scheduler.
1da177e4 LT	3	*
0fe23479	4	* Copyright (C) 2002 Jens Axboe <axboe@kernel.dk>
1da177e4 LT	5	*/
	6	#include <linux/kernel.h>
	7	#include <linux/fs.h>
	8	#include <linux/blkdev.h>
	9	#include <linux/elevator.h>
	10	#include <linux/bio.h>
1da177e4 LT	11	#include <linux/module.h>
	12	#include <linux/slab.h>
	13	#include <linux/init.h>
	14	#include <linux/compiler.h>
1da177e4 LT	15	#include <linux/rbtree.h>
	16
	17	/*
	18	* See Documentation/block/deadline-iosched.txt
	19	*/
64100099 AV	20	static const int read_expire = HZ / 2; /* max time before a read is submitted. */
	21	static const int write_expire = 5 * HZ; /* ditto for writes, these limits are SOFT! */
	22	static const int writes_starved = 2; /* max times reads can starve a write */
	23	static const int fifo_batch = 16; /* # of sequential requests treated as one
1da177e4 LT	24	by the above parameters. For throughput. */
1da177e4 LT	25
1da177e4 LT	26	struct deadline_data {
	27	/*
	28	* run time data
	29	*/
	30
	31	/*
	32	* requests (deadline_rq s) are present on both sort_list and fifo_list
	33	*/
	34	struct rb_root sort_list[2];
	35	struct list_head fifo_list[2];
4fb72f76	36
1da177e4 LT	37	/*
	38	* next in sort order. read, write or both are NULL
	39	*/
8840faa1	40	struct request *next_rq[2];
1da177e4	41	unsigned int batching; /* number of sequential requests made */
1da177e4 LT	42	unsigned int starved; /* times reads have starved writes */
	43
	44	/*
	45	* settings that change how the i/o scheduler behaves
	46	*/
	47	int fifo_expire[2];
	48	int fifo_batch;
	49	int writes_starved;
	50	int front_merges;
1da177e4 LT	51	};
1da177e4 LT	52
8840faa1	53	static void deadline_move_request(struct deadline_data , struct request );
1da177e4	54
4fb72f76 AC	55	static inline struct rb_root *
	56	deadline_rb_root(struct deadline_data dd, struct request rq)
	57	{
	58	return &dd->sort_list[rq_data_dir(rq)];
	59	}
1da177e4	60
5d1a5366 AC	61	/*
	62	* get the request after `rq' in sector-sorted order
	63	*/
	64	static inline struct request *
	65	deadline_latter_request(struct request *rq)
	66	{
	67	struct rb_node *node = rb_next(&rq->rb_node);
	68
	69	if (node)
	70	return rb_entry_rq(node);
	71
	72	return NULL;
	73	}
	74
1da177e4	75	static void
8840faa1	76	deadline_add_rq_rb(struct deadline_data dd, struct request rq)
1da177e4	77	{
4fb72f76	78	struct rb_root *root = deadline_rb_root(dd, rq);
1da177e4	79
796d5116	80	elv_rb_add(root, rq);
1da177e4 LT	81	}
	82
	83	static inline void
8840faa1	84	deadline_del_rq_rb(struct deadline_data dd, struct request rq)
1da177e4	85	{
b8aca35a	86	const int data_dir = rq_data_dir(rq);
1da177e4	87
5d1a5366 AC	88	if (dd->next_rq[data_dir] == rq)
5d1a5366 AC	89	dd->next_rq[data_dir] = deadline_latter_request(rq);
1da177e4	90
4fb72f76	91	elv_rb_del(deadline_rb_root(dd, rq), rq);
1da177e4 LT	92	}
	93
	94	/*
8840faa1	95	* add rq to rbtree and fifo
1da177e4	96	*/
b4878f24	97	static void
1da177e4 LT	98	deadline_add_request(struct request_queue q, struct request rq)
	99	{
	100	struct deadline_data *dd = q->elevator->elevator_data;
8840faa1	101	const int data_dir = rq_data_dir(rq);
1da177e4	102
8840faa1	103	deadline_add_rq_rb(dd, rq);
9817064b	104
1da177e4	105	/*
4fb72f76	106	* set expire time and add to fifo list
1da177e4	107	*/
8b4922d3	108	rq->fifo_time = jiffies + dd->fifo_expire[data_dir];
8840faa1	109	list_add_tail(&rq->queuelist, &dd->fifo_list[data_dir]);
1da177e4 LT	110	}
	111
	112	/*
9817064b	113	* remove rq from rbtree and fifo.
1da177e4	114	*/
165125e1	115	static void deadline_remove_request(struct request_queue q, struct request rq)
1da177e4	116	{
b4878f24	117	struct deadline_data *dd = q->elevator->elevator_data;
1da177e4	118
8840faa1 JA	119	rq_fifo_clear(rq);
8840faa1 JA	120	deadline_del_rq_rb(dd, rq);
1da177e4 LT	121	}
1da177e4 LT	122
34fe7c05	123	static enum elv_merge
165125e1	124	deadline_merge(struct request_queue q, struct request req, struct bio bio)
1da177e4 LT	125	{
	126	struct deadline_data *dd = q->elevator->elevator_data;
	127	struct request *__rq;
1da177e4	128
1da177e4 LT	129	/*
	130	* check for front merge
	131	*/
	132	if (dd->front_merges) {
f73a1c7d	133	sector_t sector = bio_end_sector(bio);
1da177e4	134
b8aca35a	135	__rq = elv_rb_find(&dd->sort_list[bio_data_dir(bio)], sector);
1da177e4	136	if (__rq) {
83096ebf	137	BUG_ON(sector != blk_rq_pos(__rq));
1da177e4	138
72ef799b	139	if (elv_bio_merge_ok(__rq, bio)) {
34fe7c05 CH	140	*req = __rq;
34fe7c05 CH	141	return ELEVATOR_FRONT_MERGE;
1da177e4 LT	142	}
	143	}
	144	}
	145
	146	return ELEVATOR_NO_MERGE;
1da177e4 LT	147	}
1da177e4 LT	148
165125e1	149	static void deadline_merged_request(struct request_queue *q,
34fe7c05	150	struct request *req, enum elv_merge type)
1da177e4 LT	151	{
1da177e4 LT	152	struct deadline_data *dd = q->elevator->elevator_data;
1da177e4	153
1da177e4 LT	154	/*
	155	* if the merge was a front merge, we need to reposition request
	156	*/
b8aca35a	157	if (type == ELEVATOR_FRONT_MERGE) {
4fb72f76	158	elv_rb_del(deadline_rb_root(dd, req), req);
8840faa1	159	deadline_add_rq_rb(dd, req);
1da177e4	160	}
1da177e4 LT	161	}
	162
	163	static void
165125e1	164	deadline_merged_requests(struct request_queue q, struct request req,
1da177e4 LT	165	struct request *next)
1da177e4 LT	166	{
1da177e4	167	/*
8840faa1 JA	168	* if next expires before rq, assign its expire time to rq
8840faa1 JA	169	* and move into next position (next will be deleted) in fifo
1da177e4	170	*/
8840faa1	171	if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) {
9828c2c6 JK	172	if (time_before((unsigned long)next->fifo_time,
9828c2c6 JK	173	(unsigned long)req->fifo_time)) {
8840faa1	174	list_move(&req->queuelist, &next->queuelist);
8b4922d3	175	req->fifo_time = next->fifo_time;
1da177e4 LT	176	}
	177	}
	178
	179	/*
	180	* kill knowledge of next, this one is a goner
	181	*/
	182	deadline_remove_request(q, next);
	183	}
	184
	185	/*
	186	* move request from sort list to dispatch queue.
	187	*/
	188	static inline void
8840faa1	189	deadline_move_to_dispatch(struct deadline_data dd, struct request rq)
1da177e4	190	{
165125e1	191	struct request_queue *q = rq->q;
1da177e4	192
8840faa1 JA	193	deadline_remove_request(q, rq);
8840faa1 JA	194	elv_dispatch_add_tail(q, rq);
1da177e4 LT	195	}
	196
	197	/*
	198	* move an entry to dispatch queue
	199	*/
	200	static void
8840faa1	201	deadline_move_request(struct deadline_data dd, struct request rq)
1da177e4	202	{
b8aca35a	203	const int data_dir = rq_data_dir(rq);
1da177e4	204
8840faa1 JA	205	dd->next_rq[READ] = NULL;
8840faa1 JA	206	dd->next_rq[WRITE] = NULL;
5d1a5366	207	dd->next_rq[data_dir] = deadline_latter_request(rq);
1da177e4	208
1da177e4 LT	209	/*
	210	* take it off the sort and fifo list, move
	211	* to dispatch queue
	212	*/
8840faa1	213	deadline_move_to_dispatch(dd, rq);
1da177e4 LT	214	}
1da177e4 LT	215
1da177e4	216	/*
4fb72f76	217	* deadline_check_fifo returns 0 if there are no expired requests on the fifo,
1da177e4 LT	218	* 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
	219	*/
	220	static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
	221	{
8840faa1	222	struct request *rq = rq_entry_fifo(dd->fifo_list[ddir].next);
1da177e4 LT	223
1da177e4 LT	224	/*
8840faa1	225	* rq is expired!
1da177e4	226	*/
9828c2c6	227	if (time_after_eq(jiffies, (unsigned long)rq->fifo_time))
1da177e4 LT	228	return 1;
	229
	230	return 0;
	231	}
	232
	233	/*
	234	* deadline_dispatch_requests selects the best request according to
	235	* read/write expire, fifo_batch, etc
	236	*/
165125e1	237	static int deadline_dispatch_requests(struct request_queue *q, int force)
1da177e4	238	{
b4878f24	239	struct deadline_data *dd = q->elevator->elevator_data;
1da177e4 LT	240	const int reads = !list_empty(&dd->fifo_list[READ]);
1da177e4 LT	241	const int writes = !list_empty(&dd->fifo_list[WRITE]);
8840faa1	242	struct request *rq;
4b0dc07e	243	int data_dir;
1da177e4 LT	244
	245	/*
	246	* batches are currently reads XOR writes
	247	*/
8840faa1 JA	248	if (dd->next_rq[WRITE])
8840faa1 JA	249	rq = dd->next_rq[WRITE];
9d5c1e1b	250	else
8840faa1	251	rq = dd->next_rq[READ];
1da177e4	252
63de428b AC	253	if (rq && dd->batching < dd->fifo_batch)
	254	/* we have a next request are still entitled to batch */
	255	goto dispatch_request;
1da177e4 LT	256
	257	/*
	258	* at this point we are not running a batch. select the appropriate
	259	* data direction (read / write)
	260	*/
	261
	262	if (reads) {
dd67d051	263	BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[READ]));
1da177e4 LT	264
	265	if (writes && (dd->starved++ >= dd->writes_starved))
	266	goto dispatch_writes;
	267
	268	data_dir = READ;
1da177e4 LT	269
	270	goto dispatch_find_request;
	271	}
	272
	273	/*
	274	* there are either no reads or writes have been starved
	275	*/
	276
	277	if (writes) {
	278	dispatch_writes:
dd67d051	279	BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[WRITE]));
1da177e4 LT	280
	281	dd->starved = 0;
	282
	283	data_dir = WRITE;
1da177e4 LT	284
	285	goto dispatch_find_request;
	286	}
	287
	288	return 0;
	289
	290	dispatch_find_request:
	291	/*
	292	* we are not running a batch, find best request for selected data_dir
	293	*/
6f5d8aa6 AC	294	if (deadline_check_fifo(dd, data_dir) \|\| !dd->next_rq[data_dir]) {
	295	/*
	296	* A deadline has expired, the last request was in the other
	297	* direction, or we have run out of higher-sectored requests.
	298	* Start again from the request with the earliest expiry time.
	299	*/
8840faa1	300	rq = rq_entry_fifo(dd->fifo_list[data_dir].next);
6f5d8aa6	301	} else {
1da177e4 LT	302	/*
	303	* The last req was the same dir and we have a next request in
	304	* sort order. No expired requests so continue on from here.
	305	*/
8840faa1	306	rq = dd->next_rq[data_dir];
1da177e4 LT	307	}
1da177e4 LT	308
dfb3d72a AC	309	dd->batching = 0;
dfb3d72a AC	310
1da177e4 LT	311	dispatch_request:
1da177e4 LT	312	/*
8840faa1	313	* rq is the selected appropriate request.
1da177e4 LT	314	*/
1da177e4 LT	315	dd->batching++;
8840faa1	316	deadline_move_request(dd, rq);
1da177e4 LT	317
	318	return 1;
	319	}
	320
b374d18a	321	static void deadline_exit_queue(struct elevator_queue *e)
1da177e4 LT	322	{
	323	struct deadline_data *dd = e->elevator_data;
	324
	325	BUG_ON(!list_empty(&dd->fifo_list[READ]));
	326	BUG_ON(!list_empty(&dd->fifo_list[WRITE]));
	327
1da177e4 LT	328	kfree(dd);
	329	}
	330
	331	/*
8840faa1	332	* initialize elevator private data (deadline_data).
1da177e4	333	*/
d50235b7	334	static int deadline_init_queue(struct request_queue q, struct elevator_type e)
1da177e4 LT	335	{
1da177e4 LT	336	struct deadline_data *dd;
d50235b7 JM	337	struct elevator_queue *eq;
	338
	339	eq = elevator_alloc(q, e);
	340	if (!eq)
	341	return -ENOMEM;
1da177e4	342
c1b511eb	343	dd = kzalloc_node(sizeof(*dd), GFP_KERNEL, q->node);
d50235b7 JM	344	if (!dd) {
d50235b7 JM	345	kobject_put(&eq->kobj);
b2fab5ac	346	return -ENOMEM;
d50235b7 JM	347	}
d50235b7 JM	348	eq->elevator_data = dd;
1da177e4	349
1da177e4 LT	350	INIT_LIST_HEAD(&dd->fifo_list[READ]);
	351	INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
	352	dd->sort_list[READ] = RB_ROOT;
	353	dd->sort_list[WRITE] = RB_ROOT;
1da177e4 LT	354	dd->fifo_expire[READ] = read_expire;
	355	dd->fifo_expire[WRITE] = write_expire;
	356	dd->writes_starved = writes_starved;
	357	dd->front_merges = 1;
	358	dd->fifo_batch = fifo_batch;
b2fab5ac	359
d50235b7 JM	360	spin_lock_irq(q->queue_lock);
	361	q->elevator = eq;
	362	spin_unlock_irq(q->queue_lock);
b2fab5ac	363	return 0;
1da177e4 LT	364	}
1da177e4 LT	365
1da177e4 LT	366	/*
	367	* sysfs parts below
	368	*/
1da177e4 LT	369
	370	static ssize_t
	371	deadline_var_show(int var, char *page)
	372	{
	373	return sprintf(page, "%d\n", var);
	374	}
	375
	376	static ssize_t
	377	deadline_var_store(int var, const char page, size_t count)
	378	{
	379	char p = (char ) page;
	380
	381	*var = simple_strtol(p, &p, 10);
	382	return count;
	383	}
	384
	385	#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
b374d18a	386	static ssize_t __FUNC(struct elevator_queue e, char page) \
1da177e4	387	{ \
3d1ab40f AV	388	struct deadline_data *dd = e->elevator_data; \
3d1ab40f AV	389	int __data = __VAR; \
1da177e4 LT	390	if (__CONV) \
	391	__data = jiffies_to_msecs(__data); \
	392	return deadline_var_show(__data, (page)); \
	393	}
e572ec7e AV	394	SHOW_FUNCTION(deadline_read_expire_show, dd->fifo_expire[READ], 1);
	395	SHOW_FUNCTION(deadline_write_expire_show, dd->fifo_expire[WRITE], 1);
	396	SHOW_FUNCTION(deadline_writes_starved_show, dd->writes_starved, 0);
	397	SHOW_FUNCTION(deadline_front_merges_show, dd->front_merges, 0);
	398	SHOW_FUNCTION(deadline_fifo_batch_show, dd->fifo_batch, 0);
1da177e4 LT	399	#undef SHOW_FUNCTION
	400
	401	#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
b374d18a	402	static ssize_t __FUNC(struct elevator_queue e, const char page, size_t count) \
1da177e4	403	{ \
3d1ab40f	404	struct deadline_data *dd = e->elevator_data; \
1da177e4 LT	405	int __data; \
	406	int ret = deadline_var_store(&__data, (page), count); \
	407	if (__data < (MIN)) \
	408	__data = (MIN); \
	409	else if (__data > (MAX)) \
	410	__data = (MAX); \
	411	if (__CONV) \
	412	*(__PTR) = msecs_to_jiffies(__data); \
	413	else \
	414	*(__PTR) = __data; \
	415	return ret; \
	416	}
e572ec7e AV	417	STORE_FUNCTION(deadline_read_expire_store, &dd->fifo_expire[READ], 0, INT_MAX, 1);
	418	STORE_FUNCTION(deadline_write_expire_store, &dd->fifo_expire[WRITE], 0, INT_MAX, 1);
	419	STORE_FUNCTION(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX, 0);
	420	STORE_FUNCTION(deadline_front_merges_store, &dd->front_merges, 0, 1, 0);
	421	STORE_FUNCTION(deadline_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX, 0);
1da177e4 LT	422	#undef STORE_FUNCTION
1da177e4 LT	423
e572ec7e AV	424	#define DD_ATTR(name) \
	425	__ATTR(name, S_IRUGO\|S_IWUSR, deadline_##name##_show, \
	426	deadline_##name##_store)
	427
	428	static struct elv_fs_entry deadline_attrs[] = {
	429	DD_ATTR(read_expire),
	430	DD_ATTR(write_expire),
	431	DD_ATTR(writes_starved),
	432	DD_ATTR(front_merges),
	433	DD_ATTR(fifo_batch),
	434	__ATTR_NULL
1da177e4 LT	435	};
1da177e4 LT	436
1da177e4	437	static struct elevator_type iosched_deadline = {
c51ca6cf	438	.ops.sq = {
1da177e4 LT	439	.elevator_merge_fn = deadline_merge,
	440	.elevator_merged_fn = deadline_merged_request,
	441	.elevator_merge_req_fn = deadline_merged_requests,
b4878f24 JA	442	.elevator_dispatch_fn = deadline_dispatch_requests,
b4878f24 JA	443	.elevator_add_req_fn = deadline_add_request,
b8aca35a JA	444	.elevator_former_req_fn = elv_rb_former_request,
b8aca35a JA	445	.elevator_latter_req_fn = elv_rb_latter_request,
1da177e4 LT	446	.elevator_init_fn = deadline_init_queue,
	447	.elevator_exit_fn = deadline_exit_queue,
	448	},
	449
3d1ab40f	450	.elevator_attrs = deadline_attrs,
1da177e4 LT	451	.elevator_name = "deadline",
	452	.elevator_owner = THIS_MODULE,
	453	};
	454
	455	static int __init deadline_init(void)
	456	{
3d3c2379	457	return elv_register(&iosched_deadline);
1da177e4 LT	458	}
	459
	460	static void __exit deadline_exit(void)
	461	{
1da177e4 LT	462	elv_unregister(&iosched_deadline);
	463	}
	464
	465	module_init(deadline_init);
	466	module_exit(deadline_exit);
	467
	468	MODULE_AUTHOR("Jens Axboe");
	469	MODULE_LICENSE("GPL");
	470	MODULE_DESCRIPTION("deadline IO scheduler");