[GitHub/mt8127/android_kernel_alcatel_ttab.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 *);

#define RQ_RB_ROOT(dd, rq)	(&(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 = 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)
		dd->next_rq[data_dir] = deadline_latter_request(rq);

	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(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 != __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(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(RQ_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->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(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) {
		/* 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
	 * and start a new batch
	 */
	if (deadline_check_fifo(dd, data_dir)) {
		/* An expired request exists - satisfy it */
		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.
		 */
		node = rb_first(&dd->sort_list[data_dir]);
		if (node)
			rq = rb_entry_rq(node);
	}

	dd->batching = 0;

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

	return 1;
}

static int deadline_queue_empty(struct request_queue *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(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(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 <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];
	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	57
5d1a5366 AC	58	/*
	59	* get the request after `rq' in sector-sorted order
	60	*/
	61	static inline struct request *
	62	deadline_latter_request(struct request *rq)
	63	{
	64	struct rb_node *node = rb_next(&rq->rb_node);
	65
	66	if (node)
	67	return rb_entry_rq(node);
	68
	69	return NULL;
	70	}
	71
1da177e4	72	static void
8840faa1	73	deadline_add_rq_rb(struct deadline_data dd, struct request rq)
1da177e4	74	{
b8aca35a JA	75	struct rb_root *root = RQ_RB_ROOT(dd, rq);
b8aca35a JA	76	struct request *__alias;
1da177e4 LT	77
1da177e4 LT	78	retry:
b8aca35a JA	79	__alias = elv_rb_add(root, rq);
b8aca35a JA	80	if (unlikely(__alias)) {
8840faa1	81	deadline_move_request(dd, __alias);
b8aca35a	82	goto retry;
1da177e4	83	}
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
b8aca35a	94	elv_rb_del(RQ_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 LT	108	/*
	109	* set expire time (only used for reads) and add to fifo list
	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) {
b8aca35a	141	BUG_ON(sector != __rq->sector);
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 JA	164	if (type == ELEVATOR_FRONT_MERGE) {
b8aca35a JA	165	elv_rb_del(RQ_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
8840faa1	215	dd->last_sector = rq->sector + rq->nr_sectors;
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 LT	224	/*
	225	* deadline_check_fifo returns 0 if there are no expired reads on the fifo,
	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
8840faa1	261	if (rq) {
1da177e4 LT	262	/* we have a "next request" */
1da177e4 LT	263
8840faa1	264	if (dd->last_sector != rq->sector)
1da177e4 LT	265	/* end the batch on a non sequential request */
	266	dd->batching += dd->fifo_batch;
	267
	268	if (dd->batching < dd->fifo_batch)
	269	/* we are still entitled to batch */
	270	goto dispatch_request;
	271	}
	272
	273	/*
	274	* at this point we are not running a batch. select the appropriate
	275	* data direction (read / write)
	276	*/
	277
	278	if (reads) {
dd67d051	279	BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[READ]));
1da177e4 LT	280
	281	if (writes && (dd->starved++ >= dd->writes_starved))
	282	goto dispatch_writes;
	283
	284	data_dir = READ;
1da177e4 LT	285
	286	goto dispatch_find_request;
	287	}
	288
	289	/*
	290	* there are either no reads or writes have been starved
	291	*/
	292
	293	if (writes) {
	294	dispatch_writes:
dd67d051	295	BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[WRITE]));
1da177e4 LT	296
	297	dd->starved = 0;
	298
	299	data_dir = WRITE;
1da177e4 LT	300
	301	goto dispatch_find_request;
	302	}
	303
	304	return 0;
	305
	306	dispatch_find_request:
	307	/*
	308	* we are not running a batch, find best request for selected data_dir
dfb3d72a	309	* and start a new batch
1da177e4 LT	310	*/
	311	if (deadline_check_fifo(dd, data_dir)) {
	312	/* An expired request exists - satisfy it */
8840faa1	313	rq = rq_entry_fifo(dd->fifo_list[data_dir].next);
8840faa1	314	} else if (dd->next_rq[data_dir]) {
1da177e4 LT	315	/*
	316	* The last req was the same dir and we have a next request in
	317	* sort order. No expired requests so continue on from here.
	318	*/
8840faa1	319	rq = dd->next_rq[data_dir];
1da177e4	320	} else {
8840faa1	321	struct rb_node *node;
1da177e4 LT	322	/*
	323	* The last req was the other direction or we have run out of
	324	* higher-sectored requests. Go back to the lowest sectored
	325	* request (1 way elevator) and start a new batch.
	326	*/
8840faa1 JA	327	node = rb_first(&dd->sort_list[data_dir]);
	328	if (node)
	329	rq = rb_entry_rq(node);
1da177e4 LT	330	}
1da177e4 LT	331
dfb3d72a AC	332	dd->batching = 0;
dfb3d72a AC	333
1da177e4 LT	334	dispatch_request:
1da177e4 LT	335	/*
8840faa1	336	* rq is the selected appropriate request.
1da177e4 LT	337	*/
1da177e4 LT	338	dd->batching++;
8840faa1	339	deadline_move_request(dd, rq);
1da177e4 LT	340
	341	return 1;
	342	}
	343
165125e1	344	static int deadline_queue_empty(struct request_queue *q)
1da177e4 LT	345	{
	346	struct deadline_data *dd = q->elevator->elevator_data;
	347
b4878f24 JA	348	return list_empty(&dd->fifo_list[WRITE])
b4878f24 JA	349	&& list_empty(&dd->fifo_list[READ]);
1da177e4 LT	350	}
1da177e4 LT	351
1da177e4 LT	352	static void deadline_exit_queue(elevator_t *e)
	353	{
	354	struct deadline_data *dd = e->elevator_data;
	355
	356	BUG_ON(!list_empty(&dd->fifo_list[READ]));
	357	BUG_ON(!list_empty(&dd->fifo_list[WRITE]));
	358
1da177e4 LT	359	kfree(dd);
	360	}
	361
	362	/*
8840faa1	363	* initialize elevator private data (deadline_data).
1da177e4	364	*/
165125e1	365	static void deadline_init_queue(struct request_queue q)
1da177e4 LT	366	{
1da177e4 LT	367	struct deadline_data *dd;
1da177e4	368
94f6030c	369	dd = kmalloc_node(sizeof(*dd), GFP_KERNEL \| __GFP_ZERO, q->node);
1da177e4	370	if (!dd)
bc1c1169	371	return NULL;
1da177e4	372
1da177e4 LT	373	INIT_LIST_HEAD(&dd->fifo_list[READ]);
	374	INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
	375	dd->sort_list[READ] = RB_ROOT;
	376	dd->sort_list[WRITE] = RB_ROOT;
1da177e4 LT	377	dd->fifo_expire[READ] = read_expire;
	378	dd->fifo_expire[WRITE] = write_expire;
	379	dd->writes_starved = writes_starved;
	380	dd->front_merges = 1;
	381	dd->fifo_batch = fifo_batch;
bc1c1169	382	return dd;
1da177e4 LT	383	}
1da177e4 LT	384
1da177e4 LT	385	/*
	386	* sysfs parts below
	387	*/
1da177e4 LT	388
	389	static ssize_t
	390	deadline_var_show(int var, char *page)
	391	{
	392	return sprintf(page, "%d\n", var);
	393	}
	394
	395	static ssize_t
	396	deadline_var_store(int var, const char page, size_t count)
	397	{
	398	char p = (char ) page;
	399
	400	*var = simple_strtol(p, &p, 10);
	401	return count;
	402	}
	403
	404	#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
3d1ab40f	405	static ssize_t __FUNC(elevator_t e, char page) \
1da177e4	406	{ \
3d1ab40f AV	407	struct deadline_data *dd = e->elevator_data; \
3d1ab40f AV	408	int __data = __VAR; \
1da177e4 LT	409	if (__CONV) \
	410	__data = jiffies_to_msecs(__data); \
	411	return deadline_var_show(__data, (page)); \
	412	}
e572ec7e AV	413	SHOW_FUNCTION(deadline_read_expire_show, dd->fifo_expire[READ], 1);
	414	SHOW_FUNCTION(deadline_write_expire_show, dd->fifo_expire[WRITE], 1);
	415	SHOW_FUNCTION(deadline_writes_starved_show, dd->writes_starved, 0);
	416	SHOW_FUNCTION(deadline_front_merges_show, dd->front_merges, 0);
	417	SHOW_FUNCTION(deadline_fifo_batch_show, dd->fifo_batch, 0);
1da177e4 LT	418	#undef SHOW_FUNCTION
	419
	420	#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
3d1ab40f	421	static ssize_t __FUNC(elevator_t e, const char page, size_t count) \
1da177e4	422	{ \
3d1ab40f	423	struct deadline_data *dd = e->elevator_data; \
1da177e4 LT	424	int __data; \
	425	int ret = deadline_var_store(&__data, (page), count); \
	426	if (__data < (MIN)) \
	427	__data = (MIN); \
	428	else if (__data > (MAX)) \
	429	__data = (MAX); \
	430	if (__CONV) \
	431	*(__PTR) = msecs_to_jiffies(__data); \
	432	else \
	433	*(__PTR) = __data; \
	434	return ret; \
	435	}
e572ec7e AV	436	STORE_FUNCTION(deadline_read_expire_store, &dd->fifo_expire[READ], 0, INT_MAX, 1);
	437	STORE_FUNCTION(deadline_write_expire_store, &dd->fifo_expire[WRITE], 0, INT_MAX, 1);
	438	STORE_FUNCTION(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX, 0);
	439	STORE_FUNCTION(deadline_front_merges_store, &dd->front_merges, 0, 1, 0);
	440	STORE_FUNCTION(deadline_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX, 0);
1da177e4 LT	441	#undef STORE_FUNCTION
1da177e4 LT	442
e572ec7e AV	443	#define DD_ATTR(name) \
	444	__ATTR(name, S_IRUGO\|S_IWUSR, deadline_##name##_show, \
	445	deadline_##name##_store)
	446
	447	static struct elv_fs_entry deadline_attrs[] = {
	448	DD_ATTR(read_expire),
	449	DD_ATTR(write_expire),
	450	DD_ATTR(writes_starved),
	451	DD_ATTR(front_merges),
	452	DD_ATTR(fifo_batch),
	453	__ATTR_NULL
1da177e4 LT	454	};
1da177e4 LT	455
1da177e4 LT	456	static struct elevator_type iosched_deadline = {
	457	.ops = {
	458	.elevator_merge_fn = deadline_merge,
	459	.elevator_merged_fn = deadline_merged_request,
	460	.elevator_merge_req_fn = deadline_merged_requests,
b4878f24 JA	461	.elevator_dispatch_fn = deadline_dispatch_requests,
b4878f24 JA	462	.elevator_add_req_fn = deadline_add_request,
1da177e4	463	.elevator_queue_empty_fn = deadline_queue_empty,
b8aca35a JA	464	.elevator_former_req_fn = elv_rb_former_request,
b8aca35a JA	465	.elevator_latter_req_fn = elv_rb_latter_request,
1da177e4 LT	466	.elevator_init_fn = deadline_init_queue,
	467	.elevator_exit_fn = deadline_exit_queue,
	468	},
	469
3d1ab40f	470	.elevator_attrs = deadline_attrs,
1da177e4 LT	471	.elevator_name = "deadline",
	472	.elevator_owner = THIS_MODULE,
	473	};
	474
	475	static int __init deadline_init(void)
	476	{
8840faa1	477	return elv_register(&iosched_deadline);
1da177e4 LT	478	}
	479
	480	static void __exit deadline_exit(void)
	481	{
1da177e4 LT	482	elv_unregister(&iosched_deadline);
	483	}
	484
	485	module_init(deadline_init);
	486	module_exit(deadline_exit);
	487
	488	MODULE_AUTHOR("Jens Axboe");
	489	MODULE_LICENSE("GPL");
	490	MODULE_DESCRIPTION("deadline IO scheduler");