[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 *);

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);

	dd->last_sector = rq_end_sector(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 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
4fb72f76 AC	56	static inline struct rb_root *
	57	deadline_rb_root(struct deadline_data dd, struct request rq)
	58	{
	59	return &dd->sort_list[rq_data_dir(rq)];
	60	}
1da177e4	61
5d1a5366 AC	62	/*
	63	* get the request after `rq' in sector-sorted order
	64	*/
	65	static inline struct request *
	66	deadline_latter_request(struct request *rq)
	67	{
	68	struct rb_node *node = rb_next(&rq->rb_node);
	69
	70	if (node)
	71	return rb_entry_rq(node);
	72
	73	return NULL;
	74	}
	75
1da177e4	76	static void
8840faa1	77	deadline_add_rq_rb(struct deadline_data dd, struct request rq)
1da177e4	78	{
4fb72f76	79	struct rb_root *root = deadline_rb_root(dd, rq);
1da177e4	80
796d5116	81	elv_rb_add(root, rq);
1da177e4 LT	82	}
	83
	84	static inline void
8840faa1	85	deadline_del_rq_rb(struct deadline_data dd, struct request rq)
1da177e4	86	{
b8aca35a	87	const int data_dir = rq_data_dir(rq);
1da177e4	88
5d1a5366 AC	89	if (dd->next_rq[data_dir] == rq)
5d1a5366 AC	90	dd->next_rq[data_dir] = deadline_latter_request(rq);
1da177e4	91
4fb72f76	92	elv_rb_del(deadline_rb_root(dd, rq), rq);
1da177e4 LT	93	}
	94
	95	/*
8840faa1	96	* add rq to rbtree and fifo
1da177e4	97	*/
b4878f24	98	static void
1da177e4 LT	99	deadline_add_request(struct request_queue q, struct request rq)
	100	{
	101	struct deadline_data *dd = q->elevator->elevator_data;
8840faa1	102	const int data_dir = rq_data_dir(rq);
1da177e4	103
8840faa1	104	deadline_add_rq_rb(dd, rq);
9817064b	105
1da177e4	106	/*
4fb72f76	107	* set expire time and add to fifo list
1da177e4	108	*/
8b4922d3	109	rq->fifo_time = jiffies + dd->fifo_expire[data_dir];
8840faa1	110	list_add_tail(&rq->queuelist, &dd->fifo_list[data_dir]);
1da177e4 LT	111	}
	112
	113	/*
9817064b	114	* remove rq from rbtree and fifo.
1da177e4	115	*/
165125e1	116	static void deadline_remove_request(struct request_queue q, struct request rq)
1da177e4	117	{
b4878f24	118	struct deadline_data *dd = q->elevator->elevator_data;
1da177e4	119
8840faa1 JA	120	rq_fifo_clear(rq);
8840faa1 JA	121	deadline_del_rq_rb(dd, rq);
1da177e4 LT	122	}
	123
	124	static int
165125e1	125	deadline_merge(struct request_queue q, struct request req, struct bio bio)
1da177e4 LT	126	{
	127	struct deadline_data *dd = q->elevator->elevator_data;
	128	struct request *__rq;
	129	int ret;
	130
1da177e4 LT	131	/*
	132	* check for front merge
	133	*/
	134	if (dd->front_merges) {
f73a1c7d	135	sector_t sector = bio_end_sector(bio);
1da177e4	136
b8aca35a	137	__rq = elv_rb_find(&dd->sort_list[bio_data_dir(bio)], sector);
1da177e4	138	if (__rq) {
83096ebf	139	BUG_ON(sector != blk_rq_pos(__rq));
1da177e4 LT	140
	141	if (elv_rq_merge_ok(__rq, bio)) {
	142	ret = ELEVATOR_FRONT_MERGE;
	143	goto out;
	144	}
	145	}
	146	}
	147
	148	return ELEVATOR_NO_MERGE;
	149	out:
1da177e4 LT	150	*req = __rq;
	151	return ret;
	152	}
	153
165125e1 JA	154	static void deadline_merged_request(struct request_queue *q,
165125e1 JA	155	struct request *req, int type)
1da177e4 LT	156	{
1da177e4 LT	157	struct deadline_data *dd = q->elevator->elevator_data;
1da177e4	158
1da177e4 LT	159	/*
	160	* if the merge was a front merge, we need to reposition request
	161	*/
b8aca35a	162	if (type == ELEVATOR_FRONT_MERGE) {
4fb72f76	163	elv_rb_del(deadline_rb_root(dd, req), req);
8840faa1	164	deadline_add_rq_rb(dd, req);
1da177e4	165	}
1da177e4 LT	166	}
	167
	168	static void
165125e1	169	deadline_merged_requests(struct request_queue q, struct request req,
1da177e4 LT	170	struct request *next)
1da177e4 LT	171	{
1da177e4	172	/*
8840faa1 JA	173	* if next expires before rq, assign its expire time to rq
8840faa1 JA	174	* and move into next position (next will be deleted) in fifo
1da177e4	175	*/
8840faa1	176	if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) {
8b4922d3	177	if (time_before(next->fifo_time, req->fifo_time)) {
8840faa1	178	list_move(&req->queuelist, &next->queuelist);
8b4922d3	179	req->fifo_time = next->fifo_time;
1da177e4 LT	180	}
	181	}
	182
	183	/*
	184	* kill knowledge of next, this one is a goner
	185	*/
	186	deadline_remove_request(q, next);
	187	}
	188
	189	/*
	190	* move request from sort list to dispatch queue.
	191	*/
	192	static inline void
8840faa1	193	deadline_move_to_dispatch(struct deadline_data dd, struct request rq)
1da177e4	194	{
165125e1	195	struct request_queue *q = rq->q;
1da177e4	196
8840faa1 JA	197	deadline_remove_request(q, rq);
8840faa1 JA	198	elv_dispatch_add_tail(q, rq);
1da177e4 LT	199	}
	200
	201	/*
	202	* move an entry to dispatch queue
	203	*/
	204	static void
8840faa1	205	deadline_move_request(struct deadline_data dd, struct request rq)
1da177e4	206	{
b8aca35a	207	const int data_dir = rq_data_dir(rq);
1da177e4	208
8840faa1 JA	209	dd->next_rq[READ] = NULL;
8840faa1 JA	210	dd->next_rq[WRITE] = NULL;
5d1a5366	211	dd->next_rq[data_dir] = deadline_latter_request(rq);
1da177e4	212
4fb72f76	213	dd->last_sector = rq_end_sector(rq);
1da177e4 LT	214
	215	/*
	216	* take it off the sort and fifo list, move
	217	* to dispatch queue
	218	*/
8840faa1	219	deadline_move_to_dispatch(dd, rq);
1da177e4 LT	220	}
1da177e4 LT	221
1da177e4	222	/*
4fb72f76	223	* deadline_check_fifo returns 0 if there are no expired requests on the fifo,
1da177e4 LT	224	* 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
	225	*/
	226	static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
	227	{
8840faa1	228	struct request *rq = rq_entry_fifo(dd->fifo_list[ddir].next);
1da177e4 LT	229
1da177e4 LT	230	/*
8840faa1	231	* rq is expired!
1da177e4	232	*/
8b4922d3	233	if (time_after_eq(jiffies, rq->fifo_time))
1da177e4 LT	234	return 1;
	235
	236	return 0;
	237	}
	238
	239	/*
	240	* deadline_dispatch_requests selects the best request according to
	241	* read/write expire, fifo_batch, etc
	242	*/
165125e1	243	static int deadline_dispatch_requests(struct request_queue *q, int force)
1da177e4	244	{
b4878f24	245	struct deadline_data *dd = q->elevator->elevator_data;
1da177e4 LT	246	const int reads = !list_empty(&dd->fifo_list[READ]);
1da177e4 LT	247	const int writes = !list_empty(&dd->fifo_list[WRITE]);
8840faa1	248	struct request *rq;
4b0dc07e	249	int data_dir;
1da177e4 LT	250
	251	/*
	252	* batches are currently reads XOR writes
	253	*/
8840faa1 JA	254	if (dd->next_rq[WRITE])
8840faa1 JA	255	rq = dd->next_rq[WRITE];
9d5c1e1b	256	else
8840faa1	257	rq = dd->next_rq[READ];
1da177e4	258
63de428b AC	259	if (rq && dd->batching < dd->fifo_batch)
	260	/* we have a next request are still entitled to batch */
	261	goto dispatch_request;
1da177e4 LT	262
	263	/*
	264	* at this point we are not running a batch. select the appropriate
	265	* data direction (read / write)
	266	*/
	267
	268	if (reads) {
dd67d051	269	BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[READ]));
1da177e4 LT	270
	271	if (writes && (dd->starved++ >= dd->writes_starved))
	272	goto dispatch_writes;
	273
	274	data_dir = READ;
1da177e4 LT	275
	276	goto dispatch_find_request;
	277	}
	278
	279	/*
	280	* there are either no reads or writes have been starved
	281	*/
	282
	283	if (writes) {
	284	dispatch_writes:
dd67d051	285	BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[WRITE]));
1da177e4 LT	286
	287	dd->starved = 0;
	288
	289	data_dir = WRITE;
1da177e4 LT	290
	291	goto dispatch_find_request;
	292	}
	293
	294	return 0;
	295
	296	dispatch_find_request:
	297	/*
	298	* we are not running a batch, find best request for selected data_dir
	299	*/
6f5d8aa6 AC	300	if (deadline_check_fifo(dd, data_dir) \|\| !dd->next_rq[data_dir]) {
	301	/*
	302	* A deadline has expired, the last request was in the other
	303	* direction, or we have run out of higher-sectored requests.
	304	* Start again from the request with the earliest expiry time.
	305	*/
8840faa1	306	rq = rq_entry_fifo(dd->fifo_list[data_dir].next);
6f5d8aa6	307	} else {
1da177e4 LT	308	/*
	309	* The last req was the same dir and we have a next request in
	310	* sort order. No expired requests so continue on from here.
	311	*/
8840faa1	312	rq = dd->next_rq[data_dir];
1da177e4 LT	313	}
1da177e4 LT	314
dfb3d72a AC	315	dd->batching = 0;
dfb3d72a AC	316
1da177e4 LT	317	dispatch_request:
1da177e4 LT	318	/*
8840faa1	319	* rq is the selected appropriate request.
1da177e4 LT	320	*/
1da177e4 LT	321	dd->batching++;
8840faa1	322	deadline_move_request(dd, rq);
1da177e4 LT	323
	324	return 1;
	325	}
	326
b374d18a	327	static void deadline_exit_queue(struct elevator_queue *e)
1da177e4 LT	328	{
	329	struct deadline_data *dd = e->elevator_data;
	330
	331	BUG_ON(!list_empty(&dd->fifo_list[READ]));
	332	BUG_ON(!list_empty(&dd->fifo_list[WRITE]));
	333
1da177e4 LT	334	kfree(dd);
	335	}
	336
	337	/*
8840faa1	338	* initialize elevator private data (deadline_data).
1da177e4	339	*/
d50235b7	340	static int deadline_init_queue(struct request_queue q, struct elevator_type e)
1da177e4 LT	341	{
1da177e4 LT	342	struct deadline_data *dd;
d50235b7 JM	343	struct elevator_queue *eq;
	344
	345	eq = elevator_alloc(q, e);
	346	if (!eq)
	347	return -ENOMEM;
1da177e4	348
c1b511eb	349	dd = kzalloc_node(sizeof(*dd), GFP_KERNEL, q->node);
d50235b7 JM	350	if (!dd) {
d50235b7 JM	351	kobject_put(&eq->kobj);
b2fab5ac	352	return -ENOMEM;
d50235b7 JM	353	}
d50235b7 JM	354	eq->elevator_data = dd;
1da177e4	355
1da177e4 LT	356	INIT_LIST_HEAD(&dd->fifo_list[READ]);
	357	INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
	358	dd->sort_list[READ] = RB_ROOT;
	359	dd->sort_list[WRITE] = RB_ROOT;
1da177e4 LT	360	dd->fifo_expire[READ] = read_expire;
	361	dd->fifo_expire[WRITE] = write_expire;
	362	dd->writes_starved = writes_starved;
	363	dd->front_merges = 1;
	364	dd->fifo_batch = fifo_batch;
b2fab5ac	365
d50235b7 JM	366	spin_lock_irq(q->queue_lock);
	367	q->elevator = eq;
	368	spin_unlock_irq(q->queue_lock);
b2fab5ac	369	return 0;
1da177e4 LT	370	}
1da177e4 LT	371
1da177e4 LT	372	/*
	373	* sysfs parts below
	374	*/
1da177e4 LT	375
	376	static ssize_t
	377	deadline_var_show(int var, char *page)
	378	{
	379	return sprintf(page, "%d\n", var);
	380	}
	381
	382	static ssize_t
	383	deadline_var_store(int var, const char page, size_t count)
	384	{
	385	char p = (char ) page;
	386
	387	*var = simple_strtol(p, &p, 10);
	388	return count;
	389	}
	390
	391	#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
b374d18a	392	static ssize_t __FUNC(struct elevator_queue e, char page) \
1da177e4	393	{ \
3d1ab40f AV	394	struct deadline_data *dd = e->elevator_data; \
3d1ab40f AV	395	int __data = __VAR; \
1da177e4 LT	396	if (__CONV) \
	397	__data = jiffies_to_msecs(__data); \
	398	return deadline_var_show(__data, (page)); \
	399	}
e572ec7e AV	400	SHOW_FUNCTION(deadline_read_expire_show, dd->fifo_expire[READ], 1);
	401	SHOW_FUNCTION(deadline_write_expire_show, dd->fifo_expire[WRITE], 1);
	402	SHOW_FUNCTION(deadline_writes_starved_show, dd->writes_starved, 0);
	403	SHOW_FUNCTION(deadline_front_merges_show, dd->front_merges, 0);
	404	SHOW_FUNCTION(deadline_fifo_batch_show, dd->fifo_batch, 0);
1da177e4 LT	405	#undef SHOW_FUNCTION
	406
	407	#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
b374d18a	408	static ssize_t __FUNC(struct elevator_queue e, const char page, size_t count) \
1da177e4	409	{ \
3d1ab40f	410	struct deadline_data *dd = e->elevator_data; \
1da177e4 LT	411	int __data; \
	412	int ret = deadline_var_store(&__data, (page), count); \
	413	if (__data < (MIN)) \
	414	__data = (MIN); \
	415	else if (__data > (MAX)) \
	416	__data = (MAX); \
	417	if (__CONV) \
	418	*(__PTR) = msecs_to_jiffies(__data); \
	419	else \
	420	*(__PTR) = __data; \
	421	return ret; \
	422	}
e572ec7e AV	423	STORE_FUNCTION(deadline_read_expire_store, &dd->fifo_expire[READ], 0, INT_MAX, 1);
	424	STORE_FUNCTION(deadline_write_expire_store, &dd->fifo_expire[WRITE], 0, INT_MAX, 1);
	425	STORE_FUNCTION(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX, 0);
	426	STORE_FUNCTION(deadline_front_merges_store, &dd->front_merges, 0, 1, 0);
	427	STORE_FUNCTION(deadline_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX, 0);
1da177e4 LT	428	#undef STORE_FUNCTION
1da177e4 LT	429
e572ec7e AV	430	#define DD_ATTR(name) \
	431	__ATTR(name, S_IRUGO\|S_IWUSR, deadline_##name##_show, \
	432	deadline_##name##_store)
	433
	434	static struct elv_fs_entry deadline_attrs[] = {
	435	DD_ATTR(read_expire),
	436	DD_ATTR(write_expire),
	437	DD_ATTR(writes_starved),
	438	DD_ATTR(front_merges),
	439	DD_ATTR(fifo_batch),
	440	__ATTR_NULL
1da177e4 LT	441	};
1da177e4 LT	442
1da177e4 LT	443	static struct elevator_type iosched_deadline = {
	444	.ops = {
	445	.elevator_merge_fn = deadline_merge,
	446	.elevator_merged_fn = deadline_merged_request,
	447	.elevator_merge_req_fn = deadline_merged_requests,
b4878f24 JA	448	.elevator_dispatch_fn = deadline_dispatch_requests,
b4878f24 JA	449	.elevator_add_req_fn = deadline_add_request,
b8aca35a JA	450	.elevator_former_req_fn = elv_rb_former_request,
b8aca35a JA	451	.elevator_latter_req_fn = elv_rb_latter_request,
1da177e4 LT	452	.elevator_init_fn = deadline_init_queue,
	453	.elevator_exit_fn = deadline_exit_queue,
	454	},
	455
3d1ab40f	456	.elevator_attrs = deadline_attrs,
1da177e4 LT	457	.elevator_name = "deadline",
	458	.elevator_owner = THIS_MODULE,
	459	};
	460
	461	static int __init deadline_init(void)
	462	{
3d3c2379	463	return elv_register(&iosched_deadline);
1da177e4 LT	464	}
	465
	466	static void __exit deadline_exit(void)
	467	{
1da177e4 LT	468	elv_unregister(&iosched_deadline);
	469	}
	470
	471	module_init(deadline_init);
	472	module_exit(deadline_exit);
	473
	474	MODULE_AUTHOR("Jens Axboe");
	475	MODULE_LICENSE("GPL");
	476	MODULE_DESCRIPTION("deadline IO scheduler");