/*
 *  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>

static const int read_expire = HZ / 2; 
static const int write_expire = 5 * HZ; 
static const int writes_starved = 2;
static const int fifo_batch = 16;      
                



#define DELTA 1    

static const int read_time_per_byte = 30 ;  
static const int write_time_per_byte = 30  ; 


static const int read_time_once_transfer = 30 ; 
static const int write_time_once_transfer = 300 ; 

struct req_list_head
{
	struct request *current_req;
	unsigned long last_jiffies;
	long current_weight;
	struct req_list_head *next;
	struct req_list_head *prev;
};

struct deadline_data {

	struct req_list_head req_weight_list[2];
	struct request *next_rq[2];
	struct rb_root sort_list[2];	
	struct list_head fifo_list[2];
	unsigned int batching;		/* number of sequential requests made */      
	sector_t last_sector;		/* head position */
	unsigned int starved;		/* times reads have starved writes */
	int fifo_expire[2];                                                     
	int fifo_batch;
	int writes_starved;                                                    
	int front_merges;                                                        

};
void req_list_remove_request(struct req_list_head *list_head);
struct request *select_req_from_weight_list(struct req_list_head *req_write_list,struct req_list_head *req_read_list);
int req_list_empty(struct req_list_head *list_head);
void req_list_add(struct req_list_head *new_req,struct req_list_head *list_head);
void update_req_list_weight(struct req_list_head *list_head);
long req_list_count_weight(int data_dir,unsigned int bio_size);  
void Init_req_list_head(struct req_list_head *req_weight_list);
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)];
}

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)        
{
	printk("enter merge_add_request\n");
	struct deadline_data *dd = q->elevator->elevator_data;
	const int data_dir = rq_data_dir(rq);    
	
	unsigned int bio_size=rq->__data_len;


	struct req_list_head *req_list=(struct req_list_head *)kmalloc(sizeof(*req_list),GFP_KERNEL);
	req_list->current_req=rq;
	req_list->current_weight=req_list_count_weight(data_dir,bio_size);
	req_list->last_jiffies=jiffies;
	req_list_add(req_list,&dd->req_weight_list[data_dir]);

	deadline_add_rq_rb(dd, rq);
	rq_set_fifo_time(rq, jiffies + dd->fifo_expire[data_dir]);
	list_add_tail(&rq->queuelist, &dd->fifo_list[data_dir]);
		printk("Quit merge_add_request\n");
}

/*
 * 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);                                     
	}
	/*
	 * if the merge was a front merge, we need to reposition request
	 */
}

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;
    const int data_dir = rq_data_dir(rq);
	req_list_remove_request(&(dd->req_weight_list[data_dir]));
    
	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);
	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);
	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)  
{
	printk("enter merge_dispatch_request\n");
	struct deadline_data *dd = q->elevator->elevator_data;
	const int reads = !req_list_empty(&dd->req_weight_list[READ]);
	const int writes = !req_list_empty(&dd->req_weight_list[WRITE]);
	struct request *rq;

    if(reads&&writes)     
	{
		rq=select_req_from_weight_list(&dd->req_weight_list[READ],&dd->req_weight_list[WRITE]);
	    goto	dispatch_request;
	}
	else if(reads)
	{
		rq=dd->req_weight_list[READ].next->current_req;
		goto dispatch_request;
	}
	else if(writes)
	{
		rq=dd->req_weight_list[WRITE].next->current_req;
		goto dispatch_request;
	}
	else 
		return 0;
dispatch_request:
	deadline_move_request(dd, rq);  
	printk("enter merge_dispatch_request\n");
	return 1;
}

static int deadline_queue_empty(struct request_queue *q)
{
	struct deadline_data *dd = q->elevator->elevator_data;

	return req_list_empty(&dd->req_weight_list[WRITE])&&req_list_empty(&dd->req_weight_list[READ]);
}

static void deadline_exit_queue(struct elevator_queue *e)
{
	struct deadline_data *dd = e->elevator_data;

	BUG_ON(!req_list_empty(&dd->req_weight_list[WRITE]));
	BUG_ON(!req_list_empty(&dd->req_weight_list[READ])); 


	kfree(dd);
}

/*
 * initialize elevator private data (deadline_data).
 */
static void *deadline_init_queue(struct request_queue *q)
{

	struct deadline_data *dd;
	printk("enter merge_init_queue\n");
	dd = kmalloc_node(sizeof(*dd), GFP_KERNEL | __GFP_ZERO, q->node);
	if (!dd)
		return NULL;

	Init_req_list_head(&(dd->req_weight_list[READ]));
	Init_req_list_head(&(dd->req_weight_list[WRITE]));
	dd->fifo_expire[READ] = read_expire;
	dd->fifo_expire[WRITE] = write_expire;
	dd->writes_starved = writes_starved;
	dd->front_merges =0;
	dd->fifo_batch = fifo_batch;

	/*hl */
	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;
	printk("quit merge_init_queue\n");
	return dd;
}

void Init_req_list_head(struct req_list_head *req_weight_list)
{
	req_weight_list->next=req_weight_list;
	req_weight_list->prev=req_weight_list;
}

long req_list_count_weight(int data_dir,unsigned int bio_size)  
{
	long weight;
	if(data_dir==READ)
	{
		weight=read_expire*DELTA*1000-(bio_size)*read_time_per_byte*(10-DELTA)/1000-read_time_once_transfer*10;
		return weight;
	}
	else 
	{
		weight=write_expire*DELTA*1000-(bio_size)*write_time_per_byte*(10-DELTA)/1000-write_time_once_transfer*10;
		return weight;
	}
}


void update_req_list_weight(struct req_list_head *list_head)
{
	if(req_list_empty(list_head))
		return ;
	struct req_list_head *list_update=list_head;
	struct req_list_head *list_update_head=list_head;
	while(list_update->next!=list_update_head)
	{
		list_update=list_update->next;
		unsigned long go_by_jiffies;
		go_by_jiffies=jiffies - list_update->last_jiffies;
		list_update->last_jiffies=jiffies;
		list_update->current_weight=list_update->current_weight-go_by_jiffies*1000000*DELTA/HZ;
	}
}
void req_list_add(struct req_list_head *new_req,struct req_list_head *list_head)
{
	printk("enter merge_req_list_add\n");
	update_req_list_weight(list_head);

	if(list_head->next==list_head&&list_head->prev==list_head)
	{
		list_head->next=new_req;
		new_req->prev=list_head;
		list_head->prev=new_req;
		new_req->next=list_head;
		return ;
	}
	struct req_list_head *head_temp=list_head;
	struct req_list_head *head_list_temp=list_head;
    
	while(1)
	{
		if(new_req->current_weight>=head_temp->next->current_weight)
		{
			if(head_temp->next->next==head_list_temp)
			{
				struct req_list_head *temp_temp=head_temp->next;
				temp_temp->next=new_req;
				new_req->next=head_list_temp;
				new_req->prev=temp_temp;
				head_list_temp->prev=new_req;
				break;
			}
			    head_temp=head_temp->next;
		}
		else
		{
			struct req_list_head *next_req=head_temp->next;
			head_temp->next=new_req;
			new_req->next=next_req;
			next_req->prev=new_req;
			new_req->prev=head_temp;
			break;
		}
	}
		printk("quit merge_req_list_add\n");
}

int req_list_empty(struct req_list_head *list_head)
{
	if((list_head->next==list_head)&&(list_head->prev==list_head))
		return 1;
    else
		return 0;
}

struct request *select_req_from_weight_list(struct req_list_head *req_read_list,struct req_list_head *req_write_list)
{
		update_req_list_weight(req_read_list);
		update_req_list_weight(req_write_list);
		if(req_write_list->next->current_weight<req_read_list->next->current_weight)
			return req_write_list->next->current_req;
		else 
			return req_read_list->next->current_req;
}

void req_list_remove_request(struct req_list_head *list_head)
{
	printk("enter req_list_remove_request!\n");
	if(!req_list_empty(list_head))
	{	
		struct req_list_head *list_req=list_head->next;
		list_head->next=list_req->next;
		list_req->next->prev=list_head;
		list_req->next=list_req;
		list_req->prev=list_req;
		kfree(list_req);
	}
	printk("quit req_list_remove_request!\n");
}

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_simple = {
	.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_simple",
	.elevator_owner = THIS_MODULE,
};

static int __init deadline_simple_init(void)                                
{
	elv_register(&iosched_deadline_simple);

	return 0;
}

static void __exit deadline_simple_exit(void)
{
	elv_unregister(&iosched_deadline_simple);
}

module_init(deadline_simple_init);
module_exit(deadline_simple_exit);

MODULE_AUTHOR("Han");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("deadline_simple IO scheduler");