[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 */
	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 int
deadline_merge(struct request_queue *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_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_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(struct request_queue *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(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(next->fifo_time, 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, 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 = {
		.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 <[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];
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	}
	122
	123	static int
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;
	128	int ret;
	129
1da177e4 LT	130	/*
	131	* check for front merge
	132	*/
	133	if (dd->front_merges) {
f73a1c7d	134	sector_t sector = bio_end_sector(bio);
1da177e4	135
b8aca35a	136	__rq = elv_rb_find(&dd->sort_list[bio_data_dir(bio)], sector);
1da177e4	137	if (__rq) {
83096ebf	138	BUG_ON(sector != blk_rq_pos(__rq));
1da177e4 LT	139
	140	if (elv_rq_merge_ok(__rq, bio)) {
	141	ret = ELEVATOR_FRONT_MERGE;
	142	goto out;
	143	}
	144	}
	145	}
	146
	147	return ELEVATOR_NO_MERGE;
	148	out:
1da177e4 LT	149	*req = __rq;
	150	return ret;
	151	}
	152
165125e1 JA	153	static void deadline_merged_request(struct request_queue *q,
165125e1 JA	154	struct request *req, int type)
1da177e4 LT	155	{
1da177e4 LT	156	struct deadline_data *dd = q->elevator->elevator_data;
1da177e4	157
1da177e4 LT	158	/*
	159	* if the merge was a front merge, we need to reposition request
	160	*/
b8aca35a	161	if (type == ELEVATOR_FRONT_MERGE) {
4fb72f76	162	elv_rb_del(deadline_rb_root(dd, req), req);
8840faa1	163	deadline_add_rq_rb(dd, req);
1da177e4	164	}
1da177e4 LT	165	}
	166
	167	static void
165125e1	168	deadline_merged_requests(struct request_queue q, struct request req,
1da177e4 LT	169	struct request *next)
1da177e4 LT	170	{
1da177e4	171	/*
8840faa1 JA	172	* if next expires before rq, assign its expire time to rq
8840faa1 JA	173	* and move into next position (next will be deleted) in fifo
1da177e4	174	*/
8840faa1	175	if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) {
8b4922d3	176	if (time_before(next->fifo_time, req->fifo_time)) {
8840faa1	177	list_move(&req->queuelist, &next->queuelist);
8b4922d3	178	req->fifo_time = next->fifo_time;
1da177e4 LT	179	}
	180	}
	181
	182	/*
	183	* kill knowledge of next, this one is a goner
	184	*/
	185	deadline_remove_request(q, next);
	186	}
	187
	188	/*
	189	* move request from sort list to dispatch queue.
	190	*/
	191	static inline void
8840faa1	192	deadline_move_to_dispatch(struct deadline_data dd, struct request rq)
1da177e4	193	{
165125e1	194	struct request_queue *q = rq->q;
1da177e4	195
8840faa1 JA	196	deadline_remove_request(q, rq);
8840faa1 JA	197	elv_dispatch_add_tail(q, rq);
1da177e4 LT	198	}
	199
	200	/*
	201	* move an entry to dispatch queue
	202	*/
	203	static void
8840faa1	204	deadline_move_request(struct deadline_data dd, struct request rq)
1da177e4	205	{
b8aca35a	206	const int data_dir = rq_data_dir(rq);
1da177e4	207
8840faa1 JA	208	dd->next_rq[READ] = NULL;
8840faa1 JA	209	dd->next_rq[WRITE] = NULL;
5d1a5366	210	dd->next_rq[data_dir] = deadline_latter_request(rq);
1da177e4	211
1da177e4 LT	212	/*
	213	* take it off the sort and fifo list, move
	214	* to dispatch queue
	215	*/
8840faa1	216	deadline_move_to_dispatch(dd, rq);
1da177e4 LT	217	}
1da177e4 LT	218
1da177e4	219	/*
4fb72f76	220	* deadline_check_fifo returns 0 if there are no expired requests on the fifo,
1da177e4 LT	221	* 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
	222	*/
	223	static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
	224	{
8840faa1	225	struct request *rq = rq_entry_fifo(dd->fifo_list[ddir].next);
1da177e4 LT	226
1da177e4 LT	227	/*
8840faa1	228	* rq is expired!
1da177e4	229	*/
8b4922d3	230	if (time_after_eq(jiffies, rq->fifo_time))
1da177e4 LT	231	return 1;
	232
	233	return 0;
	234	}
	235
	236	/*
	237	* deadline_dispatch_requests selects the best request according to
	238	* read/write expire, fifo_batch, etc
	239	*/
165125e1	240	static int deadline_dispatch_requests(struct request_queue *q, int force)
1da177e4	241	{
b4878f24	242	struct deadline_data *dd = q->elevator->elevator_data;
1da177e4 LT	243	const int reads = !list_empty(&dd->fifo_list[READ]);
1da177e4 LT	244	const int writes = !list_empty(&dd->fifo_list[WRITE]);
8840faa1	245	struct request *rq;
4b0dc07e	246	int data_dir;
1da177e4 LT	247
	248	/*
	249	* batches are currently reads XOR writes
	250	*/
8840faa1 JA	251	if (dd->next_rq[WRITE])
8840faa1 JA	252	rq = dd->next_rq[WRITE];
9d5c1e1b	253	else
8840faa1	254	rq = dd->next_rq[READ];
1da177e4	255
63de428b AC	256	if (rq && dd->batching < dd->fifo_batch)
	257	/* we have a next request are still entitled to batch */
	258	goto dispatch_request;
1da177e4 LT	259
	260	/*
	261	* at this point we are not running a batch. select the appropriate
	262	* data direction (read / write)
	263	*/
	264
	265	if (reads) {
dd67d051	266	BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[READ]));
1da177e4 LT	267
	268	if (writes && (dd->starved++ >= dd->writes_starved))
	269	goto dispatch_writes;
	270
	271	data_dir = READ;
1da177e4 LT	272
	273	goto dispatch_find_request;
	274	}
	275
	276	/*
	277	* there are either no reads or writes have been starved
	278	*/
	279
	280	if (writes) {
	281	dispatch_writes:
dd67d051	282	BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[WRITE]));
1da177e4 LT	283
	284	dd->starved = 0;
	285
	286	data_dir = WRITE;
1da177e4 LT	287
	288	goto dispatch_find_request;
	289	}
	290
	291	return 0;
	292
	293	dispatch_find_request:
	294	/*
	295	* we are not running a batch, find best request for selected data_dir
	296	*/
6f5d8aa6 AC	297	if (deadline_check_fifo(dd, data_dir) \|\| !dd->next_rq[data_dir]) {
	298	/*
	299	* A deadline has expired, the last request was in the other
	300	* direction, or we have run out of higher-sectored requests.
	301	* Start again from the request with the earliest expiry time.
	302	*/
8840faa1	303	rq = rq_entry_fifo(dd->fifo_list[data_dir].next);
6f5d8aa6	304	} else {
1da177e4 LT	305	/*
	306	* The last req was the same dir and we have a next request in
	307	* sort order. No expired requests so continue on from here.
	308	*/
8840faa1	309	rq = dd->next_rq[data_dir];
1da177e4 LT	310	}
1da177e4 LT	311
dfb3d72a AC	312	dd->batching = 0;
dfb3d72a AC	313
1da177e4 LT	314	dispatch_request:
1da177e4 LT	315	/*
8840faa1	316	* rq is the selected appropriate request.
1da177e4 LT	317	*/
1da177e4 LT	318	dd->batching++;
8840faa1	319	deadline_move_request(dd, rq);
1da177e4 LT	320
	321	return 1;
	322	}
	323
b374d18a	324	static void deadline_exit_queue(struct elevator_queue *e)
1da177e4 LT	325	{
	326	struct deadline_data *dd = e->elevator_data;
	327
	328	BUG_ON(!list_empty(&dd->fifo_list[READ]));
	329	BUG_ON(!list_empty(&dd->fifo_list[WRITE]));
	330
1da177e4 LT	331	kfree(dd);
	332	}
	333
	334	/*
8840faa1	335	* initialize elevator private data (deadline_data).
1da177e4	336	*/
d50235b7	337	static int deadline_init_queue(struct request_queue q, struct elevator_type e)
1da177e4 LT	338	{
1da177e4 LT	339	struct deadline_data *dd;
d50235b7 JM	340	struct elevator_queue *eq;
	341
	342	eq = elevator_alloc(q, e);
	343	if (!eq)
	344	return -ENOMEM;
1da177e4	345
c1b511eb	346	dd = kzalloc_node(sizeof(*dd), GFP_KERNEL, q->node);
d50235b7 JM	347	if (!dd) {
d50235b7 JM	348	kobject_put(&eq->kobj);
b2fab5ac	349	return -ENOMEM;
d50235b7 JM	350	}
d50235b7 JM	351	eq->elevator_data = dd;
1da177e4	352
1da177e4 LT	353	INIT_LIST_HEAD(&dd->fifo_list[READ]);
	354	INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
	355	dd->sort_list[READ] = RB_ROOT;
	356	dd->sort_list[WRITE] = RB_ROOT;
1da177e4 LT	357	dd->fifo_expire[READ] = read_expire;
	358	dd->fifo_expire[WRITE] = write_expire;
	359	dd->writes_starved = writes_starved;
	360	dd->front_merges = 1;
	361	dd->fifo_batch = fifo_batch;
b2fab5ac	362
d50235b7 JM	363	spin_lock_irq(q->queue_lock);
	364	q->elevator = eq;
	365	spin_unlock_irq(q->queue_lock);
b2fab5ac	366	return 0;
1da177e4 LT	367	}
1da177e4 LT	368
1da177e4 LT	369	/*
	370	* sysfs parts below
	371	*/
1da177e4 LT	372
	373	static ssize_t
	374	deadline_var_show(int var, char *page)
	375	{
	376	return sprintf(page, "%d\n", var);
	377	}
	378
	379	static ssize_t
	380	deadline_var_store(int var, const char page, size_t count)
	381	{
	382	char p = (char ) page;
	383
	384	*var = simple_strtol(p, &p, 10);
	385	return count;
	386	}
	387
	388	#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
b374d18a	389	static ssize_t __FUNC(struct elevator_queue e, char page) \
1da177e4	390	{ \
3d1ab40f AV	391	struct deadline_data *dd = e->elevator_data; \
3d1ab40f AV	392	int __data = __VAR; \
1da177e4 LT	393	if (__CONV) \
	394	__data = jiffies_to_msecs(__data); \
	395	return deadline_var_show(__data, (page)); \
	396	}
e572ec7e AV	397	SHOW_FUNCTION(deadline_read_expire_show, dd->fifo_expire[READ], 1);
	398	SHOW_FUNCTION(deadline_write_expire_show, dd->fifo_expire[WRITE], 1);
	399	SHOW_FUNCTION(deadline_writes_starved_show, dd->writes_starved, 0);
	400	SHOW_FUNCTION(deadline_front_merges_show, dd->front_merges, 0);
	401	SHOW_FUNCTION(deadline_fifo_batch_show, dd->fifo_batch, 0);
1da177e4 LT	402	#undef SHOW_FUNCTION
	403
	404	#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
b374d18a	405	static ssize_t __FUNC(struct elevator_queue e, const char page, size_t count) \
1da177e4	406	{ \
3d1ab40f	407	struct deadline_data *dd = e->elevator_data; \
1da177e4 LT	408	int __data; \
	409	int ret = deadline_var_store(&__data, (page), count); \
	410	if (__data < (MIN)) \
	411	__data = (MIN); \
	412	else if (__data > (MAX)) \
	413	__data = (MAX); \
	414	if (__CONV) \
	415	*(__PTR) = msecs_to_jiffies(__data); \
	416	else \
	417	*(__PTR) = __data; \
	418	return ret; \
	419	}
e572ec7e AV	420	STORE_FUNCTION(deadline_read_expire_store, &dd->fifo_expire[READ], 0, INT_MAX, 1);
	421	STORE_FUNCTION(deadline_write_expire_store, &dd->fifo_expire[WRITE], 0, INT_MAX, 1);
	422	STORE_FUNCTION(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX, 0);
	423	STORE_FUNCTION(deadline_front_merges_store, &dd->front_merges, 0, 1, 0);
	424	STORE_FUNCTION(deadline_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX, 0);
1da177e4 LT	425	#undef STORE_FUNCTION
1da177e4 LT	426
e572ec7e AV	427	#define DD_ATTR(name) \
	428	__ATTR(name, S_IRUGO\|S_IWUSR, deadline_##name##_show, \
	429	deadline_##name##_store)
	430
	431	static struct elv_fs_entry deadline_attrs[] = {
	432	DD_ATTR(read_expire),
	433	DD_ATTR(write_expire),
	434	DD_ATTR(writes_starved),
	435	DD_ATTR(front_merges),
	436	DD_ATTR(fifo_batch),
	437	__ATTR_NULL
1da177e4 LT	438	};
1da177e4 LT	439
1da177e4 LT	440	static struct elevator_type iosched_deadline = {
	441	.ops = {
	442	.elevator_merge_fn = deadline_merge,
	443	.elevator_merged_fn = deadline_merged_request,
	444	.elevator_merge_req_fn = deadline_merged_requests,
b4878f24 JA	445	.elevator_dispatch_fn = deadline_dispatch_requests,
b4878f24 JA	446	.elevator_add_req_fn = deadline_add_request,
b8aca35a JA	447	.elevator_former_req_fn = elv_rb_former_request,
b8aca35a JA	448	.elevator_latter_req_fn = elv_rb_latter_request,
1da177e4 LT	449	.elevator_init_fn = deadline_init_queue,
	450	.elevator_exit_fn = deadline_exit_queue,
	451	},
	452
3d1ab40f	453	.elevator_attrs = deadline_attrs,
1da177e4 LT	454	.elevator_name = "deadline",
	455	.elevator_owner = THIS_MODULE,
	456	};
	457
	458	static int __init deadline_init(void)
	459	{
3d3c2379	460	return elv_register(&iosched_deadline);
1da177e4 LT	461	}
	462
	463	static void __exit deadline_exit(void)
	464	{
1da177e4 LT	465	elv_unregister(&iosched_deadline);
	466	}
	467
	468	module_init(deadline_init);
	469	module_exit(deadline_exit);
	470
	471	MODULE_AUTHOR("Jens Axboe");
	472	MODULE_LICENSE("GPL");
	473	MODULE_DESCRIPTION("deadline IO scheduler");