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

/*
 *  Deadline i/o scheduler.
 *
 *  Copyright (C) 2002 Jens Axboe <[email protected]>
 */
#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 */
	sector_t last_sector;		/* head position */
	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 *);

#define RQ_RB_ROOT(dd, rq)	(&(dd)->sort_list[rq_data_dir((rq))])

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

retry:
	__alias = elv_rb_add(root, rq);
	if (unlikely(__alias)) {
		deadline_move_request(dd, __alias);
		goto retry;
	}
}

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) {
		struct rb_node *rbnext = rb_next(&rq->rb_node);

		dd->next_rq[data_dir] = NULL;
		if (rbnext)
			dd->next_rq[data_dir] = rb_entry_rq(rbnext);
	}

	elv_rb_del(RQ_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 (only used for reads) and add to fifo list
	 */
	rq_set_fifo_time(rq, 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(request_queue_t *q, struct request *rq)
{
	struct deadline_data *dd = q->elevator->elevator_data;

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

static int
deadline_merge(request_queue_t *q, struct request **req, struct bio *bio)
{
	struct deadline_data *dd = q->elevator->elevator_data;
	struct request *__rq;
	int ret;

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

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

			if (elv_rq_merge_ok(__rq, bio)) {
				ret = ELEVATOR_FRONT_MERGE;
				goto out;
			}
		}
	}

	return ELEVATOR_NO_MERGE;
out:
	*req = __rq;
	return ret;
}

static void deadline_merged_request(request_queue_t *q, struct request *req,
				    int 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(RQ_RB_ROOT(dd, req), req);
		deadline_add_rq_rb(dd, req);
	}
}

static void
deadline_merged_requests(request_queue_t *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(rq_fifo_time(next), rq_fifo_time(req))) {
			list_move(&req->queuelist, &next->queuelist);
			rq_set_fifo_time(req, rq_fifo_time(next));
		}
	}

	/*
	 * 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)
{
	request_queue_t *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);
	struct rb_node *rbnext = rb_next(&rq->rb_node);

	dd->next_rq[READ] = NULL;
	dd->next_rq[WRITE] = NULL;

	if (rbnext)
		dd->next_rq[data_dir] = rb_entry_rq(rbnext);
	
	dd->last_sector = rq->sector + rq->nr_sectors;

	/*
	 * 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 reads 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(jiffies, rq_fifo_time(rq)))
		return 1;

	return 0;
}

/*
 * deadline_dispatch_requests selects the best request according to
 * read/write expire, fifo_batch, etc
 */
static int deadline_dispatch_requests(request_queue_t *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) {
		/* we have a "next request" */
		
		if (dd->last_sector != rq->sector)
			/* end the batch on a non sequential request */
			dd->batching += dd->fifo_batch;
		
		if (dd->batching < dd->fifo_batch)
			/* we 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)) {
		/* An expired request exists - satisfy it */
		dd->batching = 0;
		rq = rq_entry_fifo(dd->fifo_list[data_dir].next);
		
	} else if (dd->next_rq[data_dir]) {
		/*
		 * 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];
	} else {
		struct rb_node *node;
		/*
		 * The last req was the other direction or we have run out of
		 * higher-sectored requests. Go back to the lowest sectored
		 * request (1 way elevator) and start a new batch.
		 */
		dd->batching = 0;
		node = rb_first(&dd->sort_list[data_dir]);
		if (node)
			rq = rb_entry_rq(node);
	}

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

	return 1;
}

static int deadline_queue_empty(request_queue_t *q)
{
	struct deadline_data *dd = q->elevator->elevator_data;

	return list_empty(&dd->fifo_list[WRITE])
		&& list_empty(&dd->fifo_list[READ]);
}

static void deadline_exit_queue(elevator_t *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 void *deadline_init_queue(request_queue_t *q, elevator_t *e)
{
	struct deadline_data *dd;

	dd = kmalloc_node(sizeof(*dd), GFP_KERNEL, q->node);
	if (!dd)
		return NULL;
	memset(dd, 0, sizeof(*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;
	return dd;
}

/*
 * 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(elevator_t *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(elevator_t *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 = {
		.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_queue_empty_fn =	deadline_queue_empty,
		.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 <[email protected]>
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];
	36
	37	/*
	38	* next in sort order. read, write or both are NULL
	39	*/
8840faa1	40	struct request *next_rq[2];
1da177e4 LT	41	unsigned int batching; /* number of sequential requests made */
	42	sector_t last_sector; /* head position */
	43	unsigned int starved; /* times reads have starved writes */
	44
	45	/*
	46	* settings that change how the i/o scheduler behaves
	47	*/
	48	int fifo_expire[2];
	49	int fifo_batch;
	50	int writes_starved;
	51	int front_merges;
1da177e4 LT	52	};
1da177e4 LT	53
8840faa1	54	static void deadline_move_request(struct deadline_data , struct request );
1da177e4	55
b8aca35a	56	#define RQ_RB_ROOT(dd, rq) (&(dd)->sort_list[rq_data_dir((rq))])
1da177e4 LT	57
1da177e4 LT	58	static void
8840faa1	59	deadline_add_rq_rb(struct deadline_data dd, struct request rq)
1da177e4	60	{
b8aca35a JA	61	struct rb_root *root = RQ_RB_ROOT(dd, rq);
b8aca35a JA	62	struct request *__alias;
1da177e4 LT	63
1da177e4 LT	64	retry:
b8aca35a JA	65	__alias = elv_rb_add(root, rq);
b8aca35a JA	66	if (unlikely(__alias)) {
8840faa1	67	deadline_move_request(dd, __alias);
b8aca35a	68	goto retry;
1da177e4	69	}
1da177e4 LT	70	}
	71
	72	static inline void
8840faa1	73	deadline_del_rq_rb(struct deadline_data dd, struct request rq)
1da177e4	74	{
b8aca35a	75	const int data_dir = rq_data_dir(rq);
1da177e4	76
8840faa1	77	if (dd->next_rq[data_dir] == rq) {
b8aca35a	78	struct rb_node *rbnext = rb_next(&rq->rb_node);
1da177e4	79
8840faa1	80	dd->next_rq[data_dir] = NULL;
1da177e4	81	if (rbnext)
8840faa1	82	dd->next_rq[data_dir] = rb_entry_rq(rbnext);
1da177e4 LT	83	}
1da177e4 LT	84
b8aca35a	85	elv_rb_del(RQ_RB_ROOT(dd, rq), rq);
1da177e4 LT	86	}
	87
	88	/*
8840faa1	89	* add rq to rbtree and fifo
1da177e4	90	*/
b4878f24	91	static void
1da177e4 LT	92	deadline_add_request(struct request_queue q, struct request rq)
	93	{
	94	struct deadline_data *dd = q->elevator->elevator_data;
8840faa1	95	const int data_dir = rq_data_dir(rq);
1da177e4	96
8840faa1	97	deadline_add_rq_rb(dd, rq);
9817064b	98
1da177e4 LT	99	/*
	100	* set expire time (only used for reads) and add to fifo list
	101	*/
8840faa1 JA	102	rq_set_fifo_time(rq, jiffies + dd->fifo_expire[data_dir]);
8840faa1 JA	103	list_add_tail(&rq->queuelist, &dd->fifo_list[data_dir]);
1da177e4 LT	104	}
	105
	106	/*
9817064b	107	* remove rq from rbtree and fifo.
1da177e4 LT	108	*/
	109	static void deadline_remove_request(request_queue_t q, struct request rq)
	110	{
b4878f24	111	struct deadline_data *dd = q->elevator->elevator_data;
1da177e4	112
8840faa1 JA	113	rq_fifo_clear(rq);
8840faa1 JA	114	deadline_del_rq_rb(dd, rq);
1da177e4 LT	115	}
	116
	117	static int
	118	deadline_merge(request_queue_t q, struct request req, struct bio bio)
	119	{
	120	struct deadline_data *dd = q->elevator->elevator_data;
	121	struct request *__rq;
	122	int ret;
	123
1da177e4 LT	124	/*
	125	* check for front merge
	126	*/
	127	if (dd->front_merges) {
b8aca35a	128	sector_t sector = bio->bi_sector + bio_sectors(bio);
1da177e4	129
b8aca35a	130	__rq = elv_rb_find(&dd->sort_list[bio_data_dir(bio)], sector);
1da177e4	131	if (__rq) {
b8aca35a	132	BUG_ON(sector != __rq->sector);
1da177e4 LT	133
	134	if (elv_rq_merge_ok(__rq, bio)) {
	135	ret = ELEVATOR_FRONT_MERGE;
	136	goto out;
	137	}
	138	}
	139	}
	140
	141	return ELEVATOR_NO_MERGE;
	142	out:
1da177e4 LT	143	*req = __rq;
	144	return ret;
	145	}
	146
b8aca35a JA	147	static void deadline_merged_request(request_queue_t q, struct request req,
b8aca35a JA	148	int type)
1da177e4 LT	149	{
1da177e4 LT	150	struct deadline_data *dd = q->elevator->elevator_data;
1da177e4	151
1da177e4 LT	152	/*
	153	* if the merge was a front merge, we need to reposition request
	154	*/
b8aca35a JA	155	if (type == ELEVATOR_FRONT_MERGE) {
b8aca35a JA	156	elv_rb_del(RQ_RB_ROOT(dd, req), req);
8840faa1	157	deadline_add_rq_rb(dd, req);
1da177e4	158	}
1da177e4 LT	159	}
	160
	161	static void
	162	deadline_merged_requests(request_queue_t q, struct request req,
	163	struct request *next)
	164	{
1da177e4	165	/*
8840faa1 JA	166	* if next expires before rq, assign its expire time to rq
8840faa1 JA	167	* and move into next position (next will be deleted) in fifo
1da177e4	168	*/
8840faa1 JA	169	if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) {
	170	if (time_before(rq_fifo_time(next), rq_fifo_time(req))) {
	171	list_move(&req->queuelist, &next->queuelist);
	172	rq_set_fifo_time(req, rq_fifo_time(next));
1da177e4 LT	173	}
	174	}
	175
	176	/*
	177	* kill knowledge of next, this one is a goner
	178	*/
	179	deadline_remove_request(q, next);
	180	}
	181
	182	/*
	183	* move request from sort list to dispatch queue.
	184	*/
	185	static inline void
8840faa1	186	deadline_move_to_dispatch(struct deadline_data dd, struct request rq)
1da177e4	187	{
8840faa1	188	request_queue_t *q = rq->q;
1da177e4	189
8840faa1 JA	190	deadline_remove_request(q, rq);
8840faa1 JA	191	elv_dispatch_add_tail(q, rq);
1da177e4 LT	192	}
	193
	194	/*
	195	* move an entry to dispatch queue
	196	*/
	197	static void
8840faa1	198	deadline_move_request(struct deadline_data dd, struct request rq)
1da177e4	199	{
b8aca35a JA	200	const int data_dir = rq_data_dir(rq);
b8aca35a JA	201	struct rb_node *rbnext = rb_next(&rq->rb_node);
1da177e4	202
8840faa1 JA	203	dd->next_rq[READ] = NULL;
8840faa1 JA	204	dd->next_rq[WRITE] = NULL;
1da177e4 LT	205
1da177e4 LT	206	if (rbnext)
8840faa1	207	dd->next_rq[data_dir] = rb_entry_rq(rbnext);
1da177e4	208
8840faa1	209	dd->last_sector = rq->sector + rq->nr_sectors;
1da177e4 LT	210
	211	/*
	212	* take it off the sort and fifo list, move
	213	* to dispatch queue
	214	*/
8840faa1	215	deadline_move_to_dispatch(dd, rq);
1da177e4 LT	216	}
1da177e4 LT	217
1da177e4 LT	218	/*
	219	* deadline_check_fifo returns 0 if there are no expired reads on the fifo,
	220	* 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
	221	*/
	222	static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
	223	{
8840faa1	224	struct request *rq = rq_entry_fifo(dd->fifo_list[ddir].next);
1da177e4 LT	225
1da177e4 LT	226	/*
8840faa1	227	* rq is expired!
1da177e4	228	*/
8840faa1	229	if (time_after(jiffies, rq_fifo_time(rq)))
1da177e4 LT	230	return 1;
	231
	232	return 0;
	233	}
	234
	235	/*
	236	* deadline_dispatch_requests selects the best request according to
	237	* read/write expire, fifo_batch, etc
	238	*/
b4878f24	239	static int deadline_dispatch_requests(request_queue_t *q, int force)
1da177e4	240	{
b4878f24	241	struct deadline_data *dd = q->elevator->elevator_data;
1da177e4 LT	242	const int reads = !list_empty(&dd->fifo_list[READ]);
1da177e4 LT	243	const int writes = !list_empty(&dd->fifo_list[WRITE]);
8840faa1	244	struct request *rq;
4b0dc07e	245	int data_dir;
1da177e4 LT	246
	247	/*
	248	* batches are currently reads XOR writes
	249	*/
8840faa1 JA	250	if (dd->next_rq[WRITE])
8840faa1 JA	251	rq = dd->next_rq[WRITE];
9d5c1e1b	252	else
8840faa1	253	rq = dd->next_rq[READ];
1da177e4	254
8840faa1	255	if (rq) {
1da177e4 LT	256	/* we have a "next request" */
1da177e4 LT	257
8840faa1	258	if (dd->last_sector != rq->sector)
1da177e4 LT	259	/* end the batch on a non sequential request */
	260	dd->batching += dd->fifo_batch;
	261
	262	if (dd->batching < dd->fifo_batch)
	263	/* we are still entitled to batch */
	264	goto dispatch_request;
	265	}
	266
	267	/*
	268	* at this point we are not running a batch. select the appropriate
	269	* data direction (read / write)
	270	*/
	271
	272	if (reads) {
dd67d051	273	BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[READ]));
1da177e4 LT	274
	275	if (writes && (dd->starved++ >= dd->writes_starved))
	276	goto dispatch_writes;
	277
	278	data_dir = READ;
1da177e4 LT	279
	280	goto dispatch_find_request;
	281	}
	282
	283	/*
	284	* there are either no reads or writes have been starved
	285	*/
	286
	287	if (writes) {
	288	dispatch_writes:
dd67d051	289	BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[WRITE]));
1da177e4 LT	290
	291	dd->starved = 0;
	292
	293	data_dir = WRITE;
1da177e4 LT	294
	295	goto dispatch_find_request;
	296	}
	297
	298	return 0;
	299
	300	dispatch_find_request:
	301	/*
	302	* we are not running a batch, find best request for selected data_dir
	303	*/
	304	if (deadline_check_fifo(dd, data_dir)) {
	305	/* An expired request exists - satisfy it */
	306	dd->batching = 0;
8840faa1	307	rq = rq_entry_fifo(dd->fifo_list[data_dir].next);
1da177e4	308
8840faa1	309	} else if (dd->next_rq[data_dir]) {
1da177e4 LT	310	/*
	311	* The last req was the same dir and we have a next request in
	312	* sort order. No expired requests so continue on from here.
	313	*/
8840faa1	314	rq = dd->next_rq[data_dir];
1da177e4	315	} else {
8840faa1	316	struct rb_node *node;
1da177e4 LT	317	/*
	318	* The last req was the other direction or we have run out of
	319	* higher-sectored requests. Go back to the lowest sectored
	320	* request (1 way elevator) and start a new batch.
	321	*/
	322	dd->batching = 0;
8840faa1 JA	323	node = rb_first(&dd->sort_list[data_dir]);
	324	if (node)
	325	rq = rb_entry_rq(node);
1da177e4 LT	326	}
	327
	328	dispatch_request:
	329	/*
8840faa1	330	* rq is the selected appropriate request.
1da177e4 LT	331	*/
1da177e4 LT	332	dd->batching++;
8840faa1	333	deadline_move_request(dd, rq);
1da177e4 LT	334
	335	return 1;
	336	}
	337
1da177e4 LT	338	static int deadline_queue_empty(request_queue_t *q)
	339	{
	340	struct deadline_data *dd = q->elevator->elevator_data;
	341
b4878f24 JA	342	return list_empty(&dd->fifo_list[WRITE])
b4878f24 JA	343	&& list_empty(&dd->fifo_list[READ]);
1da177e4 LT	344	}
1da177e4 LT	345
1da177e4 LT	346	static void deadline_exit_queue(elevator_t *e)
	347	{
	348	struct deadline_data *dd = e->elevator_data;
	349
	350	BUG_ON(!list_empty(&dd->fifo_list[READ]));
	351	BUG_ON(!list_empty(&dd->fifo_list[WRITE]));
	352
1da177e4 LT	353	kfree(dd);
	354	}
	355
	356	/*
8840faa1	357	* initialize elevator private data (deadline_data).
1da177e4	358	*/
bc1c1169	359	static void deadline_init_queue(request_queue_t q, elevator_t *e)
1da177e4 LT	360	{
1da177e4 LT	361	struct deadline_data *dd;
1da177e4	362
1946089a	363	dd = kmalloc_node(sizeof(*dd), GFP_KERNEL, q->node);
1da177e4	364	if (!dd)
bc1c1169	365	return NULL;
1da177e4 LT	366	memset(dd, 0, sizeof(*dd));
1da177e4 LT	367
1da177e4 LT	368	INIT_LIST_HEAD(&dd->fifo_list[READ]);
	369	INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
	370	dd->sort_list[READ] = RB_ROOT;
	371	dd->sort_list[WRITE] = RB_ROOT;
1da177e4 LT	372	dd->fifo_expire[READ] = read_expire;
	373	dd->fifo_expire[WRITE] = write_expire;
	374	dd->writes_starved = writes_starved;
	375	dd->front_merges = 1;
	376	dd->fifo_batch = fifo_batch;
bc1c1169	377	return dd;
1da177e4 LT	378	}
1da177e4 LT	379
1da177e4 LT	380	/*
	381	* sysfs parts below
	382	*/
1da177e4 LT	383
	384	static ssize_t
	385	deadline_var_show(int var, char *page)
	386	{
	387	return sprintf(page, "%d\n", var);
	388	}
	389
	390	static ssize_t
	391	deadline_var_store(int var, const char page, size_t count)
	392	{
	393	char p = (char ) page;
	394
	395	*var = simple_strtol(p, &p, 10);
	396	return count;
	397	}
	398
	399	#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
3d1ab40f	400	static ssize_t __FUNC(elevator_t e, char page) \
1da177e4	401	{ \
3d1ab40f AV	402	struct deadline_data *dd = e->elevator_data; \
3d1ab40f AV	403	int __data = __VAR; \
1da177e4 LT	404	if (__CONV) \
	405	__data = jiffies_to_msecs(__data); \
	406	return deadline_var_show(__data, (page)); \
	407	}
e572ec7e AV	408	SHOW_FUNCTION(deadline_read_expire_show, dd->fifo_expire[READ], 1);
	409	SHOW_FUNCTION(deadline_write_expire_show, dd->fifo_expire[WRITE], 1);
	410	SHOW_FUNCTION(deadline_writes_starved_show, dd->writes_starved, 0);
	411	SHOW_FUNCTION(deadline_front_merges_show, dd->front_merges, 0);
	412	SHOW_FUNCTION(deadline_fifo_batch_show, dd->fifo_batch, 0);
1da177e4 LT	413	#undef SHOW_FUNCTION
	414
	415	#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
3d1ab40f	416	static ssize_t __FUNC(elevator_t e, const char page, size_t count) \
1da177e4	417	{ \
3d1ab40f	418	struct deadline_data *dd = e->elevator_data; \
1da177e4 LT	419	int __data; \
	420	int ret = deadline_var_store(&__data, (page), count); \
	421	if (__data < (MIN)) \
	422	__data = (MIN); \
	423	else if (__data > (MAX)) \
	424	__data = (MAX); \
	425	if (__CONV) \
	426	*(__PTR) = msecs_to_jiffies(__data); \
	427	else \
	428	*(__PTR) = __data; \
	429	return ret; \
	430	}
e572ec7e AV	431	STORE_FUNCTION(deadline_read_expire_store, &dd->fifo_expire[READ], 0, INT_MAX, 1);
	432	STORE_FUNCTION(deadline_write_expire_store, &dd->fifo_expire[WRITE], 0, INT_MAX, 1);
	433	STORE_FUNCTION(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX, 0);
	434	STORE_FUNCTION(deadline_front_merges_store, &dd->front_merges, 0, 1, 0);
	435	STORE_FUNCTION(deadline_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX, 0);
1da177e4 LT	436	#undef STORE_FUNCTION
1da177e4 LT	437
e572ec7e AV	438	#define DD_ATTR(name) \
	439	__ATTR(name, S_IRUGO\|S_IWUSR, deadline_##name##_show, \
	440	deadline_##name##_store)
	441
	442	static struct elv_fs_entry deadline_attrs[] = {
	443	DD_ATTR(read_expire),
	444	DD_ATTR(write_expire),
	445	DD_ATTR(writes_starved),
	446	DD_ATTR(front_merges),
	447	DD_ATTR(fifo_batch),
	448	__ATTR_NULL
1da177e4 LT	449	};
1da177e4 LT	450
1da177e4 LT	451	static struct elevator_type iosched_deadline = {
	452	.ops = {
	453	.elevator_merge_fn = deadline_merge,
	454	.elevator_merged_fn = deadline_merged_request,
	455	.elevator_merge_req_fn = deadline_merged_requests,
b4878f24 JA	456	.elevator_dispatch_fn = deadline_dispatch_requests,
b4878f24 JA	457	.elevator_add_req_fn = deadline_add_request,
1da177e4	458	.elevator_queue_empty_fn = deadline_queue_empty,
b8aca35a JA	459	.elevator_former_req_fn = elv_rb_former_request,
b8aca35a JA	460	.elevator_latter_req_fn = elv_rb_latter_request,
1da177e4 LT	461	.elevator_init_fn = deadline_init_queue,
	462	.elevator_exit_fn = deadline_exit_queue,
	463	},
	464
3d1ab40f	465	.elevator_attrs = deadline_attrs,
1da177e4 LT	466	.elevator_name = "deadline",
	467	.elevator_owner = THIS_MODULE,
	468	};
	469
	470	static int __init deadline_init(void)
	471	{
8840faa1	472	return elv_register(&iosched_deadline);
1da177e4 LT	473	}
	474
	475	static void __exit deadline_exit(void)
	476	{
1da177e4 LT	477	elv_unregister(&iosched_deadline);
	478	}
	479
	480	module_init(deadline_init);
	481	module_exit(deadline_exit);
	482
	483	MODULE_AUTHOR("Jens Axboe");
	484	MODULE_LICENSE("GPL");
	485	MODULE_DESCRIPTION("deadline IO scheduler");