[mirror_ubuntu-zesty-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 */
	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);
	struct request *__alias;

	while (unlikely(__alias = elv_rb_add(root, rq)))
		deadline_move_request(dd, __alias);
}

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_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(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->bi_sector + bio_sectors(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(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)
{
	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(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(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 void *deadline_init_queue(struct request_queue *q)
{
	struct deadline_data *dd;

	dd = kmalloc_node(sizeof(*dd), GFP_KERNEL | __GFP_ZERO, q->node);
	if (!dd)
		return NULL;

	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(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)
{
	elv_register(&iosched_deadline);

	return 0;
}

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 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);
b8aca35a	80	struct request *__alias;
1da177e4	81
4fb72f76	82	while (unlikely(__alias = elv_rb_add(root, rq)))
8840faa1	83	deadline_move_request(dd, __alias);
1da177e4 LT	84	}
	85
	86	static inline void
8840faa1	87	deadline_del_rq_rb(struct deadline_data dd, struct request rq)
1da177e4	88	{
b8aca35a	89	const int data_dir = rq_data_dir(rq);
1da177e4	90
5d1a5366 AC	91	if (dd->next_rq[data_dir] == rq)
5d1a5366 AC	92	dd->next_rq[data_dir] = deadline_latter_request(rq);
1da177e4	93
4fb72f76	94	elv_rb_del(deadline_rb_root(dd, rq), rq);
1da177e4 LT	95	}
	96
	97	/*
8840faa1	98	* add rq to rbtree and fifo
1da177e4	99	*/
b4878f24	100	static void
1da177e4 LT	101	deadline_add_request(struct request_queue q, struct request rq)
	102	{
	103	struct deadline_data *dd = q->elevator->elevator_data;
8840faa1	104	const int data_dir = rq_data_dir(rq);
1da177e4	105
8840faa1	106	deadline_add_rq_rb(dd, rq);
9817064b	107
1da177e4	108	/*
4fb72f76	109	* set expire time and add to fifo list
1da177e4	110	*/
8840faa1 JA	111	rq_set_fifo_time(rq, jiffies + dd->fifo_expire[data_dir]);
8840faa1 JA	112	list_add_tail(&rq->queuelist, &dd->fifo_list[data_dir]);
1da177e4 LT	113	}
	114
	115	/*
9817064b	116	* remove rq from rbtree and fifo.
1da177e4	117	*/
165125e1	118	static void deadline_remove_request(struct request_queue q, struct request rq)
1da177e4	119	{
b4878f24	120	struct deadline_data *dd = q->elevator->elevator_data;
1da177e4	121
8840faa1 JA	122	rq_fifo_clear(rq);
8840faa1 JA	123	deadline_del_rq_rb(dd, rq);
1da177e4 LT	124	}
	125
	126	static int
165125e1	127	deadline_merge(struct request_queue q, struct request req, struct bio bio)
1da177e4 LT	128	{
	129	struct deadline_data *dd = q->elevator->elevator_data;
	130	struct request *__rq;
	131	int ret;
	132
1da177e4 LT	133	/*
	134	* check for front merge
	135	*/
	136	if (dd->front_merges) {
b8aca35a	137	sector_t sector = bio->bi_sector + bio_sectors(bio);
1da177e4	138
b8aca35a	139	__rq = elv_rb_find(&dd->sort_list[bio_data_dir(bio)], sector);
1da177e4	140	if (__rq) {
83096ebf	141	BUG_ON(sector != blk_rq_pos(__rq));
1da177e4 LT	142
	143	if (elv_rq_merge_ok(__rq, bio)) {
	144	ret = ELEVATOR_FRONT_MERGE;
	145	goto out;
	146	}
	147	}
	148	}
	149
	150	return ELEVATOR_NO_MERGE;
	151	out:
1da177e4 LT	152	*req = __rq;
	153	return ret;
	154	}
	155
165125e1 JA	156	static void deadline_merged_request(struct request_queue *q,
165125e1 JA	157	struct request *req, int type)
1da177e4 LT	158	{
1da177e4 LT	159	struct deadline_data *dd = q->elevator->elevator_data;
1da177e4	160
1da177e4 LT	161	/*
	162	* if the merge was a front merge, we need to reposition request
	163	*/
b8aca35a	164	if (type == ELEVATOR_FRONT_MERGE) {
4fb72f76	165	elv_rb_del(deadline_rb_root(dd, req), req);
8840faa1	166	deadline_add_rq_rb(dd, req);
1da177e4	167	}
1da177e4 LT	168	}
	169
	170	static void
165125e1	171	deadline_merged_requests(struct request_queue q, struct request req,
1da177e4 LT	172	struct request *next)
1da177e4 LT	173	{
1da177e4	174	/*
8840faa1 JA	175	* if next expires before rq, assign its expire time to rq
8840faa1 JA	176	* and move into next position (next will be deleted) in fifo
1da177e4	177	*/
8840faa1 JA	178	if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) {
	179	if (time_before(rq_fifo_time(next), rq_fifo_time(req))) {
	180	list_move(&req->queuelist, &next->queuelist);
	181	rq_set_fifo_time(req, rq_fifo_time(next));
1da177e4 LT	182	}
	183	}
	184
	185	/*
	186	* kill knowledge of next, this one is a goner
	187	*/
	188	deadline_remove_request(q, next);
	189	}
	190
	191	/*
	192	* move request from sort list to dispatch queue.
	193	*/
	194	static inline void
8840faa1	195	deadline_move_to_dispatch(struct deadline_data dd, struct request rq)
1da177e4	196	{
165125e1	197	struct request_queue *q = rq->q;
1da177e4	198
8840faa1 JA	199	deadline_remove_request(q, rq);
8840faa1 JA	200	elv_dispatch_add_tail(q, rq);
1da177e4 LT	201	}
	202
	203	/*
	204	* move an entry to dispatch queue
	205	*/
	206	static void
8840faa1	207	deadline_move_request(struct deadline_data dd, struct request rq)
1da177e4	208	{
b8aca35a	209	const int data_dir = rq_data_dir(rq);
1da177e4	210
8840faa1 JA	211	dd->next_rq[READ] = NULL;
8840faa1 JA	212	dd->next_rq[WRITE] = NULL;
5d1a5366	213	dd->next_rq[data_dir] = deadline_latter_request(rq);
1da177e4	214
4fb72f76	215	dd->last_sector = rq_end_sector(rq);
1da177e4 LT	216
	217	/*
	218	* take it off the sort and fifo list, move
	219	* to dispatch queue
	220	*/
8840faa1	221	deadline_move_to_dispatch(dd, rq);
1da177e4 LT	222	}
1da177e4 LT	223
1da177e4	224	/*
4fb72f76	225	* deadline_check_fifo returns 0 if there are no expired requests on the fifo,
1da177e4 LT	226	* 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
	227	*/
	228	static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
	229	{
8840faa1	230	struct request *rq = rq_entry_fifo(dd->fifo_list[ddir].next);
1da177e4 LT	231
1da177e4 LT	232	/*
8840faa1	233	* rq is expired!
1da177e4	234	*/
8840faa1	235	if (time_after(jiffies, rq_fifo_time(rq)))
1da177e4 LT	236	return 1;
	237
	238	return 0;
	239	}
	240
	241	/*
	242	* deadline_dispatch_requests selects the best request according to
	243	* read/write expire, fifo_batch, etc
	244	*/
165125e1	245	static int deadline_dispatch_requests(struct request_queue *q, int force)
1da177e4	246	{
b4878f24	247	struct deadline_data *dd = q->elevator->elevator_data;
1da177e4 LT	248	const int reads = !list_empty(&dd->fifo_list[READ]);
1da177e4 LT	249	const int writes = !list_empty(&dd->fifo_list[WRITE]);
8840faa1	250	struct request *rq;
4b0dc07e	251	int data_dir;
1da177e4 LT	252
	253	/*
	254	* batches are currently reads XOR writes
	255	*/
8840faa1 JA	256	if (dd->next_rq[WRITE])
8840faa1 JA	257	rq = dd->next_rq[WRITE];
9d5c1e1b	258	else
8840faa1	259	rq = dd->next_rq[READ];
1da177e4	260
63de428b AC	261	if (rq && dd->batching < dd->fifo_batch)
	262	/* we have a next request are still entitled to batch */
	263	goto dispatch_request;
1da177e4 LT	264
	265	/*
	266	* at this point we are not running a batch. select the appropriate
	267	* data direction (read / write)
	268	*/
	269
	270	if (reads) {
dd67d051	271	BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[READ]));
1da177e4 LT	272
	273	if (writes && (dd->starved++ >= dd->writes_starved))
	274	goto dispatch_writes;
	275
	276	data_dir = READ;
1da177e4 LT	277
	278	goto dispatch_find_request;
	279	}
	280
	281	/*
	282	* there are either no reads or writes have been starved
	283	*/
	284
	285	if (writes) {
	286	dispatch_writes:
dd67d051	287	BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[WRITE]));
1da177e4 LT	288
	289	dd->starved = 0;
	290
	291	data_dir = WRITE;
1da177e4 LT	292
	293	goto dispatch_find_request;
	294	}
	295
	296	return 0;
	297
	298	dispatch_find_request:
	299	/*
	300	* we are not running a batch, find best request for selected data_dir
	301	*/
6f5d8aa6 AC	302	if (deadline_check_fifo(dd, data_dir) \|\| !dd->next_rq[data_dir]) {
	303	/*
	304	* A deadline has expired, the last request was in the other
	305	* direction, or we have run out of higher-sectored requests.
	306	* Start again from the request with the earliest expiry time.
	307	*/
8840faa1	308	rq = rq_entry_fifo(dd->fifo_list[data_dir].next);
6f5d8aa6	309	} else {
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 LT	315	}
1da177e4 LT	316
dfb3d72a AC	317	dd->batching = 0;
dfb3d72a AC	318
1da177e4 LT	319	dispatch_request:
1da177e4 LT	320	/*
8840faa1	321	* rq is the selected appropriate request.
1da177e4 LT	322	*/
1da177e4 LT	323	dd->batching++;
8840faa1	324	deadline_move_request(dd, rq);
1da177e4 LT	325
	326	return 1;
	327	}
	328
b374d18a	329	static void deadline_exit_queue(struct elevator_queue *e)
1da177e4 LT	330	{
	331	struct deadline_data *dd = e->elevator_data;
	332
	333	BUG_ON(!list_empty(&dd->fifo_list[READ]));
	334	BUG_ON(!list_empty(&dd->fifo_list[WRITE]));
	335
1da177e4 LT	336	kfree(dd);
	337	}
	338
	339	/*
8840faa1	340	* initialize elevator private data (deadline_data).
1da177e4	341	*/
165125e1	342	static void deadline_init_queue(struct request_queue q)
1da177e4 LT	343	{
1da177e4 LT	344	struct deadline_data *dd;
1da177e4	345
94f6030c	346	dd = kmalloc_node(sizeof(*dd), GFP_KERNEL \| __GFP_ZERO, q->node);
1da177e4	347	if (!dd)
bc1c1169	348	return NULL;
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;
bc1c1169	359	return dd;
1da177e4 LT	360	}
1da177e4 LT	361
1da177e4 LT	362	/*
	363	* sysfs parts below
	364	*/
1da177e4 LT	365
	366	static ssize_t
	367	deadline_var_show(int var, char *page)
	368	{
	369	return sprintf(page, "%d\n", var);
	370	}
	371
	372	static ssize_t
	373	deadline_var_store(int var, const char page, size_t count)
	374	{
	375	char p = (char ) page;
	376
	377	*var = simple_strtol(p, &p, 10);
	378	return count;
	379	}
	380
	381	#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
b374d18a	382	static ssize_t __FUNC(struct elevator_queue e, char page) \
1da177e4	383	{ \
3d1ab40f AV	384	struct deadline_data *dd = e->elevator_data; \
3d1ab40f AV	385	int __data = __VAR; \
1da177e4 LT	386	if (__CONV) \
	387	__data = jiffies_to_msecs(__data); \
	388	return deadline_var_show(__data, (page)); \
	389	}
e572ec7e AV	390	SHOW_FUNCTION(deadline_read_expire_show, dd->fifo_expire[READ], 1);
	391	SHOW_FUNCTION(deadline_write_expire_show, dd->fifo_expire[WRITE], 1);
	392	SHOW_FUNCTION(deadline_writes_starved_show, dd->writes_starved, 0);
	393	SHOW_FUNCTION(deadline_front_merges_show, dd->front_merges, 0);
	394	SHOW_FUNCTION(deadline_fifo_batch_show, dd->fifo_batch, 0);
1da177e4 LT	395	#undef SHOW_FUNCTION
	396
	397	#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
b374d18a	398	static ssize_t __FUNC(struct elevator_queue e, const char page, size_t count) \
1da177e4	399	{ \
3d1ab40f	400	struct deadline_data *dd = e->elevator_data; \
1da177e4 LT	401	int __data; \
	402	int ret = deadline_var_store(&__data, (page), count); \
	403	if (__data < (MIN)) \
	404	__data = (MIN); \
	405	else if (__data > (MAX)) \
	406	__data = (MAX); \
	407	if (__CONV) \
	408	*(__PTR) = msecs_to_jiffies(__data); \
	409	else \
	410	*(__PTR) = __data; \
	411	return ret; \
	412	}
e572ec7e AV	413	STORE_FUNCTION(deadline_read_expire_store, &dd->fifo_expire[READ], 0, INT_MAX, 1);
	414	STORE_FUNCTION(deadline_write_expire_store, &dd->fifo_expire[WRITE], 0, INT_MAX, 1);
	415	STORE_FUNCTION(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX, 0);
	416	STORE_FUNCTION(deadline_front_merges_store, &dd->front_merges, 0, 1, 0);
	417	STORE_FUNCTION(deadline_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX, 0);
1da177e4 LT	418	#undef STORE_FUNCTION
1da177e4 LT	419
e572ec7e AV	420	#define DD_ATTR(name) \
	421	__ATTR(name, S_IRUGO\|S_IWUSR, deadline_##name##_show, \
	422	deadline_##name##_store)
	423
	424	static struct elv_fs_entry deadline_attrs[] = {
	425	DD_ATTR(read_expire),
	426	DD_ATTR(write_expire),
	427	DD_ATTR(writes_starved),
	428	DD_ATTR(front_merges),
	429	DD_ATTR(fifo_batch),
	430	__ATTR_NULL
1da177e4 LT	431	};
1da177e4 LT	432
1da177e4 LT	433	static struct elevator_type iosched_deadline = {
	434	.ops = {
	435	.elevator_merge_fn = deadline_merge,
	436	.elevator_merged_fn = deadline_merged_request,
	437	.elevator_merge_req_fn = deadline_merged_requests,
b4878f24 JA	438	.elevator_dispatch_fn = deadline_dispatch_requests,
b4878f24 JA	439	.elevator_add_req_fn = deadline_add_request,
b8aca35a JA	440	.elevator_former_req_fn = elv_rb_former_request,
b8aca35a JA	441	.elevator_latter_req_fn = elv_rb_latter_request,
1da177e4 LT	442	.elevator_init_fn = deadline_init_queue,
	443	.elevator_exit_fn = deadline_exit_queue,
	444	},
	445
3d1ab40f	446	.elevator_attrs = deadline_attrs,
1da177e4 LT	447	.elevator_name = "deadline",
	448	.elevator_owner = THIS_MODULE,
	449	};
	450
	451	static int __init deadline_init(void)
	452	{
2fdd82bd AB	453	elv_register(&iosched_deadline);
	454
	455	return 0;
1da177e4 LT	456	}
	457
	458	static void __exit deadline_exit(void)
	459	{
1da177e4 LT	460	elv_unregister(&iosched_deadline);
	461	}
	462
	463	module_init(deadline_init);
	464	module_exit(deadline_exit);
	465
	466	MODULE_AUTHOR("Jens Axboe");
	467	MODULE_LICENSE("GPL");
	468	MODULE_DESCRIPTION("deadline IO scheduler");