block/sio-iosched.c - android_kernel_htc_msm7x30 - Gitiles

 /*
  * Simple IO scheduler
  * Based on Noop, Deadline and V(R) IO schedulers.
  *
  * Copyright (C) 2012 Miguel Boton <mboton@gmail.com>
  *
  *
  * This algorithm does not do any kind of sorting, as it is aimed for
  * aleatory access devices, but it does some basic merging. We try to
  * keep minimum overhead to achieve low latency.
  *
  * Asynchronous and synchronous requests are not treated separately, but
  * we relay on deadlines to ensure fairness.
  *
  */
 #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/version.h>

 enum { ASYNC, SYNC };

 /* Tunables */
 static const int sync_read_expire  = HZ / 2;	/* max time before a sync read is submitted. */
 static const int sync_write_expire = 2 * HZ;	/* max time before a sync write is submitted. */

 static const int async_read_expire  =  4 * HZ;	/* ditto for async, these limits are SOFT! */
 static const int async_write_expire = 16 * HZ;	/* ditto for async, these limits are SOFT! */

 static const int writes_starved = 2;		/* max times reads can starve a write */
 static const int fifo_batch     = 8;		/* # of sequential requests treated as one
 						   by the above parameters. For throughput. */

 /* Elevator data */
 struct sio_data {
 	/* Request queues */
 	struct list_head fifo_list[2][2];

 	/* Attributes */
 	unsigned int batched;
 	unsigned int starved;

 	/* Settings */
 	int fifo_expire[2][2];
 	int fifo_batch;
 	int writes_starved;
 };

 static void
 sio_merged_requests(struct request_queue *q, struct request *rq,
 		    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(&rq->queuelist) && !list_empty(&next->queuelist)) {
 		if (time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
 			list_move(&rq->queuelist, &next->queuelist);
 			rq_set_fifo_time(rq, rq_fifo_time(next));
 		}
 	}

 	/* Delete next request */
 	rq_fifo_clear(next);
 }

 static void
 sio_add_request(struct request_queue *q, struct request *rq)
 {
 	struct sio_data *sd = q->elevator->elevator_data;
 	const int sync = rq_is_sync(rq);
 	const int data_dir = rq_data_dir(rq);

 	/*
 	 * Add request to the proper fifo list and set its
 	 * expire time.
 	 */
 	rq_set_fifo_time(rq, jiffies + sd->fifo_expire[sync][data_dir]);
 	list_add_tail(&rq->queuelist, &sd->fifo_list[sync][data_dir]);
 }

 #if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,38)
 static int
 sio_queue_empty(struct request_queue *q)
 {
 	struct sio_data *sd = q->elevator->elevator_data;

 	/* Check if fifo lists are empty */
 	return list_empty(&sd->fifo_list[SYNC][READ]) && list_empty(&sd->fifo_list[SYNC][WRITE]) &&
 	       list_empty(&sd->fifo_list[ASYNC][READ]) && list_empty(&sd->fifo_list[ASYNC][WRITE]);
 }
 #endif

 static struct request *
 sio_expired_request(struct sio_data *sd, int sync, int data_dir)
 {
 	struct list_head *list = &sd->fifo_list[sync][data_dir];
 	struct request *rq;

 	if (list_empty(list))
 		return NULL;

 	/* Retrieve request */
 	rq = rq_entry_fifo(list->next);

 	/* Request has expired */
 	if (time_after(jiffies, rq_fifo_time(rq)))
 		return rq;

 	return NULL;
 }

 static struct request *
 sio_choose_expired_request(struct sio_data *sd)
 {
 	struct request *rq;

 	/*
 	 * Check expired requests.
 	 * Asynchronous requests have priority over synchronous.
 	 * Write requests have priority over read.
 	 */
 	rq = sio_expired_request(sd, ASYNC, WRITE);
 	if (rq)
 		return rq;
 	rq = sio_expired_request(sd, ASYNC, READ);
 	if (rq)
 		return rq;

 	rq = sio_expired_request(sd, SYNC, WRITE);
 	if (rq)
 		return rq;
 	rq = sio_expired_request(sd, SYNC, READ);
 	if (rq)
 		return rq;

 	return NULL;
 }

 static struct request *
 sio_choose_request(struct sio_data *sd, int data_dir)
 {
 	struct list_head *sync = sd->fifo_list[SYNC];
 	struct list_head *async = sd->fifo_list[ASYNC];

 	/*
 	 * Retrieve request from available fifo list.
 	 * Synchronous requests have priority over asynchronous.
 	 * Read requests have priority over write.
 	 */
 	if (!list_empty(&sync[data_dir]))
 		return rq_entry_fifo(sync[data_dir].next);
 	if (!list_empty(&async[data_dir]))
 		return rq_entry_fifo(async[data_dir].next);

 	if (!list_empty(&sync[!data_dir]))
 		return rq_entry_fifo(sync[!data_dir].next);
 	if (!list_empty(&async[!data_dir]))
 		return rq_entry_fifo(async[!data_dir].next);

 	return NULL;
 }

 static inline void
 sio_dispatch_request(struct sio_data *sd, struct request *rq)
 {
 	/*
 	 * Remove the request from the fifo list
 	 * and dispatch it.
 	 */
 	rq_fifo_clear(rq);
 	elv_dispatch_add_tail(rq->q, rq);

 	sd->batched++;

 	if (rq_data_dir(rq))
 		sd->starved = 0;
 	else
 		sd->starved++;
 }

 static int
 sio_dispatch_requests(struct request_queue *q, int force)
 {
 	struct sio_data *sd = q->elevator->elevator_data;
 	struct request *rq = NULL;
 	int data_dir = READ;

 	/*
 	 * Retrieve any expired request after a batch of
 	 * sequential requests.
 	 */
 	if (sd->batched > sd->fifo_batch) {
 		sd->batched = 0;
 		rq = sio_choose_expired_request(sd);
 	}

 	/* Retrieve request */
 	if (!rq) {
 		if (sd->starved > sd->writes_starved)
 			data_dir = WRITE;

 		rq = sio_choose_request(sd, data_dir);
 		if (!rq)
 			return 0;
 	}

 	/* Dispatch request */
 	sio_dispatch_request(sd, rq);

 	return 1;
 }

 static struct request *
 sio_former_request(struct request_queue *q, struct request *rq)
 {
 	struct sio_data *sd = q->elevator->elevator_data;
 	const int sync = rq_is_sync(rq);
 	const int data_dir = rq_data_dir(rq);

 	if (rq->queuelist.prev == &sd->fifo_list[sync][data_dir])
 		return NULL;

 	/* Return former request */
 	return list_entry(rq->queuelist.prev, struct request, queuelist);
 }

 static struct request *
 sio_latter_request(struct request_queue *q, struct request *rq)
 {
 	struct sio_data *sd = q->elevator->elevator_data;
 	const int sync = rq_is_sync(rq);
 	const int data_dir = rq_data_dir(rq);

 	if (rq->queuelist.next == &sd->fifo_list[sync][data_dir])
 		return NULL;

 	/* Return latter request */
 	return list_entry(rq->queuelist.next, struct request, queuelist);
 }

 static void *
 sio_init_queue(struct request_queue *q)
 {
 	struct sio_data *sd;

 	/* Allocate structure */
 	sd = kmalloc_node(sizeof(*sd), GFP_KERNEL, q->node);
 	if (!sd)
 		return NULL;

 	/* Initialize fifo lists */
 	INIT_LIST_HEAD(&sd->fifo_list[SYNC][READ]);
 	INIT_LIST_HEAD(&sd->fifo_list[SYNC][WRITE]);
 	INIT_LIST_HEAD(&sd->fifo_list[ASYNC][READ]);
 	INIT_LIST_HEAD(&sd->fifo_list[ASYNC][WRITE]);

 	/* Initialize data */
 	sd->batched = 0;
 	sd->fifo_expire[SYNC][READ] = sync_read_expire;
 	sd->fifo_expire[SYNC][WRITE] = sync_write_expire;
 	sd->fifo_expire[ASYNC][READ] = async_read_expire;
 	sd->fifo_expire[ASYNC][WRITE] = async_write_expire;
 	sd->fifo_batch = fifo_batch;

 	return sd;
 }

 static void
 sio_exit_queue(struct elevator_queue *e)
 {
 	struct sio_data *sd = e->elevator_data;

 	BUG_ON(!list_empty(&sd->fifo_list[SYNC][READ]));
 	BUG_ON(!list_empty(&sd->fifo_list[SYNC][WRITE]));
 	BUG_ON(!list_empty(&sd->fifo_list[ASYNC][READ]));
 	BUG_ON(!list_empty(&sd->fifo_list[ASYNC][WRITE]));

 	/* Free structure */
 	kfree(sd);
 }

 /*
  * sysfs code
  */

 static ssize_t
 sio_var_show(int var, char *page)
 {
 	return sprintf(page, "%d\n", var);
 }

 static ssize_t
 sio_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 sio_data *sd = e->elevator_data;			\
 	int __data = __VAR;						\
 	if (__CONV)							\
 		__data = jiffies_to_msecs(__data);			\
 	return sio_var_show(__data, (page));			\
 }
 SHOW_FUNCTION(sio_sync_read_expire_show, sd->fifo_expire[SYNC][READ], 1);
 SHOW_FUNCTION(sio_sync_write_expire_show, sd->fifo_expire[SYNC][WRITE], 1);
 SHOW_FUNCTION(sio_async_read_expire_show, sd->fifo_expire[ASYNC][READ], 1);
 SHOW_FUNCTION(sio_async_write_expire_show, sd->fifo_expire[ASYNC][WRITE], 1);
 SHOW_FUNCTION(sio_fifo_batch_show, sd->fifo_batch, 0);
 SHOW_FUNCTION(sio_writes_starved_show, sd->writes_starved, 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 sio_data *sd = e->elevator_data;			\
 	int __data;							\
 	int ret = sio_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(sio_sync_read_expire_store, &sd->fifo_expire[SYNC][READ], 0, INT_MAX, 1);
 STORE_FUNCTION(sio_sync_write_expire_store, &sd->fifo_expire[SYNC][WRITE], 0, INT_MAX, 1);
 STORE_FUNCTION(sio_async_read_expire_store, &sd->fifo_expire[ASYNC][READ], 0, INT_MAX, 1);
 STORE_FUNCTION(sio_async_write_expire_store, &sd->fifo_expire[ASYNC][WRITE], 0, INT_MAX, 1);
 STORE_FUNCTION(sio_fifo_batch_store, &sd->fifo_batch, 0, INT_MAX, 0);
 STORE_FUNCTION(sio_writes_starved_store, &sd->writes_starved, 0, INT_MAX, 0);
 #undef STORE_FUNCTION

 #define DD_ATTR(name) \
 	__ATTR(name, S_IRUGO|S_IWUSR, sio_##name##_show, \
 				      sio_##name##_store)

 static struct elv_fs_entry sio_attrs[] = {
 	DD_ATTR(sync_read_expire),
 	DD_ATTR(sync_write_expire),
 	DD_ATTR(async_read_expire),
 	DD_ATTR(async_write_expire),
 	DD_ATTR(fifo_batch),
 	DD_ATTR(writes_starved),
 	__ATTR_NULL
 };

 static struct elevator_type iosched_sio = {
 	.ops = {
 		.elevator_merge_req_fn		= sio_merged_requests,
 		.elevator_dispatch_fn		= sio_dispatch_requests,
 		.elevator_add_req_fn		= sio_add_request,
 #if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,38)
 		.elevator_queue_empty_fn	= sio_queue_empty,
 #endif
 		.elevator_former_req_fn		= sio_former_request,
 		.elevator_latter_req_fn		= sio_latter_request,
 		.elevator_init_fn		= sio_init_queue,
 		.elevator_exit_fn		= sio_exit_queue,
 	},

 	.elevator_attrs = sio_attrs,
 	.elevator_name = "sio",
 	.elevator_owner = THIS_MODULE,
 };

 static int __init sio_init(void)
 {
 	/* Register elevator */
 	elv_register(&iosched_sio);

 	return 0;
 }

 static void __exit sio_exit(void)
 {
 	/* Unregister elevator */
 	elv_unregister(&iosched_sio);
 }

 module_init(sio_init);
 module_exit(sio_exit);

 MODULE_AUTHOR("Miguel Boton");
 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("Simple IO scheduler");
 MODULE_VERSION("0.2");
	/*
	* Simple IO scheduler
	* Based on Noop, Deadline and V(R) IO schedulers.
	*
	* Copyright (C) 2012 Miguel Boton <mboton@gmail.com>
	*
	*
	* This algorithm does not do any kind of sorting, as it is aimed for
	* aleatory access devices, but it does some basic merging. We try to
	* keep minimum overhead to achieve low latency.
	*
	* Asynchronous and synchronous requests are not treated separately, but
	* we relay on deadlines to ensure fairness.
	*
	*/
	#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/version.h>

	enum { ASYNC, SYNC };

	/* Tunables */
	static const int sync_read_expire = HZ / 2; /* max time before a sync read is submitted. */
	static const int sync_write_expire = 2 * HZ; /* max time before a sync write is submitted. */

	static const int async_read_expire = 4 * HZ; /* ditto for async, these limits are SOFT! */
	static const int async_write_expire = 16 * HZ; /* ditto for async, these limits are SOFT! */

	static const int writes_starved = 2; /* max times reads can starve a write */
	static const int fifo_batch = 8; /* # of sequential requests treated as one
	by the above parameters. For throughput. */

	/* Elevator data */
	struct sio_data {
	/* Request queues */
	struct list_head fifo_list[2][2];

	/* Attributes */
	unsigned int batched;
	unsigned int starved;

	/* Settings */
	int fifo_expire[2][2];
	int fifo_batch;
	int writes_starved;
	};

	static void
	sio_merged_requests(struct request_queue q, struct request rq,
	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(&rq->queuelist) && !list_empty(&next->queuelist)) {
	if (time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
	list_move(&rq->queuelist, &next->queuelist);
	rq_set_fifo_time(rq, rq_fifo_time(next));
	}
	}

	/* Delete next request */
	rq_fifo_clear(next);
	}

	static void
	sio_add_request(struct request_queue q, struct request rq)
	{
	struct sio_data *sd = q->elevator->elevator_data;
	const int sync = rq_is_sync(rq);
	const int data_dir = rq_data_dir(rq);

	/*
	* Add request to the proper fifo list and set its
	* expire time.
	*/
	rq_set_fifo_time(rq, jiffies + sd->fifo_expire[sync][data_dir]);
	list_add_tail(&rq->queuelist, &sd->fifo_list[sync][data_dir]);
	}

	#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,38)
	static int
	sio_queue_empty(struct request_queue *q)
	{
	struct sio_data *sd = q->elevator->elevator_data;

	/* Check if fifo lists are empty */
	return list_empty(&sd->fifo_list[SYNC][READ]) && list_empty(&sd->fifo_list[SYNC][WRITE]) &&
	list_empty(&sd->fifo_list[ASYNC][READ]) && list_empty(&sd->fifo_list[ASYNC][WRITE]);
	}
	#endif

	static struct request *
	sio_expired_request(struct sio_data *sd, int sync, int data_dir)
	{
	struct list_head *list = &sd->fifo_list[sync][data_dir];
	struct request *rq;

	if (list_empty(list))
	return NULL;

	/* Retrieve request */
	rq = rq_entry_fifo(list->next);

	/* Request has expired */
	if (time_after(jiffies, rq_fifo_time(rq)))
	return rq;

	return NULL;
	}

	static struct request *
	sio_choose_expired_request(struct sio_data *sd)
	{
	struct request *rq;

	/*
	* Check expired requests.
	* Asynchronous requests have priority over synchronous.
	* Write requests have priority over read.
	*/
	rq = sio_expired_request(sd, ASYNC, WRITE);
	if (rq)
	return rq;
	rq = sio_expired_request(sd, ASYNC, READ);
	if (rq)
	return rq;

	rq = sio_expired_request(sd, SYNC, WRITE);
	if (rq)
	return rq;
	rq = sio_expired_request(sd, SYNC, READ);
	if (rq)
	return rq;

	return NULL;
	}

	static struct request *
	sio_choose_request(struct sio_data *sd, int data_dir)
	{
	struct list_head *sync = sd->fifo_list[SYNC];
	struct list_head *async = sd->fifo_list[ASYNC];

	/*
	* Retrieve request from available fifo list.
	* Synchronous requests have priority over asynchronous.
	* Read requests have priority over write.
	*/
	if (!list_empty(&sync[data_dir]))
	return rq_entry_fifo(sync[data_dir].next);
	if (!list_empty(&async[data_dir]))
	return rq_entry_fifo(async[data_dir].next);

	if (!list_empty(&sync[!data_dir]))
	return rq_entry_fifo(sync[!data_dir].next);
	if (!list_empty(&async[!data_dir]))
	return rq_entry_fifo(async[!data_dir].next);

	return NULL;
	}

	static inline void
	sio_dispatch_request(struct sio_data sd, struct request rq)
	{
	/*
	* Remove the request from the fifo list
	* and dispatch it.
	*/
	rq_fifo_clear(rq);
	elv_dispatch_add_tail(rq->q, rq);

	sd->batched++;

	if (rq_data_dir(rq))
	sd->starved = 0;
	else
	sd->starved++;
	}

	static int
	sio_dispatch_requests(struct request_queue *q, int force)
	{
	struct sio_data *sd = q->elevator->elevator_data;
	struct request *rq = NULL;
	int data_dir = READ;

	/*
	* Retrieve any expired request after a batch of
	* sequential requests.
	*/
	if (sd->batched > sd->fifo_batch) {
	sd->batched = 0;
	rq = sio_choose_expired_request(sd);
	}

	/* Retrieve request */
	if (!rq) {
	if (sd->starved > sd->writes_starved)
	data_dir = WRITE;

	rq = sio_choose_request(sd, data_dir);
	if (!rq)
	return 0;
	}

	/* Dispatch request */
	sio_dispatch_request(sd, rq);

	return 1;
	}

	static struct request *
	sio_former_request(struct request_queue q, struct request rq)
	{
	struct sio_data *sd = q->elevator->elevator_data;
	const int sync = rq_is_sync(rq);
	const int data_dir = rq_data_dir(rq);

	if (rq->queuelist.prev == &sd->fifo_list[sync][data_dir])
	return NULL;

	/* Return former request */
	return list_entry(rq->queuelist.prev, struct request, queuelist);
	}

	static struct request *
	sio_latter_request(struct request_queue q, struct request rq)
	{
	struct sio_data *sd = q->elevator->elevator_data;
	const int sync = rq_is_sync(rq);
	const int data_dir = rq_data_dir(rq);

	if (rq->queuelist.next == &sd->fifo_list[sync][data_dir])
	return NULL;

	/* Return latter request */
	return list_entry(rq->queuelist.next, struct request, queuelist);
	}

	static void *
	sio_init_queue(struct request_queue *q)
	{
	struct sio_data *sd;

	/* Allocate structure */
	sd = kmalloc_node(sizeof(*sd), GFP_KERNEL, q->node);
	if (!sd)
	return NULL;

	/* Initialize fifo lists */
	INIT_LIST_HEAD(&sd->fifo_list[SYNC][READ]);
	INIT_LIST_HEAD(&sd->fifo_list[SYNC][WRITE]);
	INIT_LIST_HEAD(&sd->fifo_list[ASYNC][READ]);
	INIT_LIST_HEAD(&sd->fifo_list[ASYNC][WRITE]);

	/* Initialize data */
	sd->batched = 0;
	sd->fifo_expire[SYNC][READ] = sync_read_expire;
	sd->fifo_expire[SYNC][WRITE] = sync_write_expire;
	sd->fifo_expire[ASYNC][READ] = async_read_expire;
	sd->fifo_expire[ASYNC][WRITE] = async_write_expire;
	sd->fifo_batch = fifo_batch;

	return sd;
	}

	static void
	sio_exit_queue(struct elevator_queue *e)
	{
	struct sio_data *sd = e->elevator_data;

	BUG_ON(!list_empty(&sd->fifo_list[SYNC][READ]));
	BUG_ON(!list_empty(&sd->fifo_list[SYNC][WRITE]));
	BUG_ON(!list_empty(&sd->fifo_list[ASYNC][READ]));
	BUG_ON(!list_empty(&sd->fifo_list[ASYNC][WRITE]));

	/* Free structure */
	kfree(sd);
	}

	/*
	* sysfs code
	*/

	static ssize_t
	sio_var_show(int var, char *page)
	{
	return sprintf(page, "%d\n", var);
	}

	static ssize_t
	sio_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 sio_data *sd = e->elevator_data; \
	int __data = __VAR; \
	if (__CONV) \
	__data = jiffies_to_msecs(__data); \
	return sio_var_show(__data, (page)); \
	}
	SHOW_FUNCTION(sio_sync_read_expire_show, sd->fifo_expire[SYNC][READ], 1);
	SHOW_FUNCTION(sio_sync_write_expire_show, sd->fifo_expire[SYNC][WRITE], 1);
	SHOW_FUNCTION(sio_async_read_expire_show, sd->fifo_expire[ASYNC][READ], 1);
	SHOW_FUNCTION(sio_async_write_expire_show, sd->fifo_expire[ASYNC][WRITE], 1);
	SHOW_FUNCTION(sio_fifo_batch_show, sd->fifo_batch, 0);
	SHOW_FUNCTION(sio_writes_starved_show, sd->writes_starved, 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 sio_data *sd = e->elevator_data; \
	int __data; \
	int ret = sio_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(sio_sync_read_expire_store, &sd->fifo_expire[SYNC][READ], 0, INT_MAX, 1);
	STORE_FUNCTION(sio_sync_write_expire_store, &sd->fifo_expire[SYNC][WRITE], 0, INT_MAX, 1);
	STORE_FUNCTION(sio_async_read_expire_store, &sd->fifo_expire[ASYNC][READ], 0, INT_MAX, 1);
	STORE_FUNCTION(sio_async_write_expire_store, &sd->fifo_expire[ASYNC][WRITE], 0, INT_MAX, 1);
	STORE_FUNCTION(sio_fifo_batch_store, &sd->fifo_batch, 0, INT_MAX, 0);
	STORE_FUNCTION(sio_writes_starved_store, &sd->writes_starved, 0, INT_MAX, 0);
	#undef STORE_FUNCTION

	#define DD_ATTR(name) \
	__ATTR(name, S_IRUGO\|S_IWUSR, sio_##name##_show, \
	sio_##name##_store)

	static struct elv_fs_entry sio_attrs[] = {
	DD_ATTR(sync_read_expire),
	DD_ATTR(sync_write_expire),
	DD_ATTR(async_read_expire),
	DD_ATTR(async_write_expire),
	DD_ATTR(fifo_batch),
	DD_ATTR(writes_starved),
	__ATTR_NULL
	};

	static struct elevator_type iosched_sio = {
	.ops = {
	.elevator_merge_req_fn = sio_merged_requests,
	.elevator_dispatch_fn = sio_dispatch_requests,
	.elevator_add_req_fn = sio_add_request,
	#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,38)
	.elevator_queue_empty_fn = sio_queue_empty,
	#endif
	.elevator_former_req_fn = sio_former_request,
	.elevator_latter_req_fn = sio_latter_request,
	.elevator_init_fn = sio_init_queue,
	.elevator_exit_fn = sio_exit_queue,
	},

	.elevator_attrs = sio_attrs,
	.elevator_name = "sio",
	.elevator_owner = THIS_MODULE,
	};

	static int __init sio_init(void)
	{
	/* Register elevator */
	elv_register(&iosched_sio);

	return 0;
	}

	static void __exit sio_exit(void)
	{
	/* Unregister elevator */
	elv_unregister(&iosched_sio);
	}

	module_init(sio_init);
	module_exit(sio_exit);

	MODULE_AUTHOR("Miguel Boton");
	MODULE_LICENSE("GPL");
	MODULE_DESCRIPTION("Simple IO scheduler");
	MODULE_VERSION("0.2");