elevator.h 6.82 KB
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#ifndef _LINUX_ELEVATOR_H
#define _LINUX_ELEVATOR_H

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#include <linux/percpu.h>

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#ifdef CONFIG_BLOCK

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typedef int (elevator_merge_fn) (struct request_queue *, struct request **,
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				 struct bio *);

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typedef void (elevator_merge_req_fn) (struct request_queue *, struct request *, struct request *);
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typedef void (elevator_merged_fn) (struct request_queue *, struct request *, int);
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typedef int (elevator_allow_merge_fn) (struct request_queue *, struct request *, struct bio *);
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typedef int (elevator_dispatch_fn) (struct request_queue *, int);
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typedef void (elevator_add_req_fn) (struct request_queue *, struct request *);
typedef int (elevator_queue_empty_fn) (struct request_queue *);
typedef struct request *(elevator_request_list_fn) (struct request_queue *, struct request *);
typedef void (elevator_completed_req_fn) (struct request_queue *, struct request *);
typedef int (elevator_may_queue_fn) (struct request_queue *, int);
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typedef int (elevator_set_req_fn) (struct request_queue *, struct request *, gfp_t);
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typedef void (elevator_put_req_fn) (struct request *);
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typedef void (elevator_activate_req_fn) (struct request_queue *, struct request *);
typedef void (elevator_deactivate_req_fn) (struct request_queue *, struct request *);
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typedef void *(elevator_init_fn) (struct request_queue *);
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typedef void (elevator_exit_fn) (struct elevator_queue *);
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struct elevator_ops
{
	elevator_merge_fn *elevator_merge_fn;
	elevator_merged_fn *elevator_merged_fn;
	elevator_merge_req_fn *elevator_merge_req_fn;
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	elevator_allow_merge_fn *elevator_allow_merge_fn;
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	elevator_dispatch_fn *elevator_dispatch_fn;
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	elevator_add_req_fn *elevator_add_req_fn;
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	elevator_activate_req_fn *elevator_activate_req_fn;
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	elevator_deactivate_req_fn *elevator_deactivate_req_fn;

	elevator_queue_empty_fn *elevator_queue_empty_fn;
	elevator_completed_req_fn *elevator_completed_req_fn;

	elevator_request_list_fn *elevator_former_req_fn;
	elevator_request_list_fn *elevator_latter_req_fn;

	elevator_set_req_fn *elevator_set_req_fn;
	elevator_put_req_fn *elevator_put_req_fn;

	elevator_may_queue_fn *elevator_may_queue_fn;

	elevator_init_fn *elevator_init_fn;
	elevator_exit_fn *elevator_exit_fn;
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	void (*trim)(struct io_context *);
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};

#define ELV_NAME_MAX	(16)

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struct elv_fs_entry {
	struct attribute attr;
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	ssize_t (*show)(struct elevator_queue *, char *);
	ssize_t (*store)(struct elevator_queue *, const char *, size_t);
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};

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/*
 * identifies an elevator type, such as AS or deadline
 */
struct elevator_type
{
	struct list_head list;
	struct elevator_ops ops;
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	struct elv_fs_entry *elevator_attrs;
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	char elevator_name[ELV_NAME_MAX];
	struct module *elevator_owner;
};

/*
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 * each queue has an elevator_queue associated with it
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 */
struct elevator_queue
{
	struct elevator_ops *ops;
	void *elevator_data;
	struct kobject kobj;
	struct elevator_type *elevator_type;
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	struct mutex sysfs_lock;
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	struct hlist_head *hash;
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};

/*
 * block elevator interface
 */
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extern void elv_dispatch_sort(struct request_queue *, struct request *);
extern void elv_dispatch_add_tail(struct request_queue *, struct request *);
extern void elv_add_request(struct request_queue *, struct request *, int, int);
extern void __elv_add_request(struct request_queue *, struct request *, int, int);
extern void elv_insert(struct request_queue *, struct request *, int);
extern int elv_merge(struct request_queue *, struct request **, struct bio *);
extern void elv_merge_requests(struct request_queue *, struct request *,
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			       struct request *);
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extern void elv_merged_request(struct request_queue *, struct request *, int);
extern void elv_dequeue_request(struct request_queue *, struct request *);
extern void elv_requeue_request(struct request_queue *, struct request *);
extern int elv_queue_empty(struct request_queue *);
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extern struct request *elv_next_request(struct request_queue *q);
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extern struct request *elv_former_request(struct request_queue *, struct request *);
extern struct request *elv_latter_request(struct request_queue *, struct request *);
extern int elv_register_queue(struct request_queue *q);
extern void elv_unregister_queue(struct request_queue *q);
extern int elv_may_queue(struct request_queue *, int);
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extern void elv_abort_queue(struct request_queue *);
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extern void elv_completed_request(struct request_queue *, struct request *);
extern int elv_set_request(struct request_queue *, struct request *, gfp_t);
extern void elv_put_request(struct request_queue *, struct request *);
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/*
 * io scheduler registration
 */
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extern void elv_register(struct elevator_type *);
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extern void elv_unregister(struct elevator_type *);

/*
 * io scheduler sysfs switching
 */
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extern ssize_t elv_iosched_show(struct request_queue *, char *);
extern ssize_t elv_iosched_store(struct request_queue *, const char *, size_t);
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extern int elevator_init(struct request_queue *, char *);
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extern void elevator_exit(struct elevator_queue *);
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extern int elv_rq_merge_ok(struct request *, struct bio *);

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/*
 * Helper functions.
 */
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extern struct request *elv_rb_former_request(struct request_queue *, struct request *);
extern struct request *elv_rb_latter_request(struct request_queue *, struct request *);
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/*
 * rb support functions.
 */
extern struct request *elv_rb_add(struct rb_root *, struct request *);
extern void elv_rb_del(struct rb_root *, struct request *);
extern struct request *elv_rb_find(struct rb_root *, sector_t);

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/*
 * Return values from elevator merger
 */
#define ELEVATOR_NO_MERGE	0
#define ELEVATOR_FRONT_MERGE	1
#define ELEVATOR_BACK_MERGE	2

/*
 * Insertion selection
 */
#define ELEVATOR_INSERT_FRONT	1
#define ELEVATOR_INSERT_BACK	2
#define ELEVATOR_INSERT_SORT	3
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#define ELEVATOR_INSERT_REQUEUE	4
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/*
 * return values from elevator_may_queue_fn
 */
enum {
	ELV_MQUEUE_MAY,
	ELV_MQUEUE_NO,
	ELV_MQUEUE_MUST,
};

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#define rq_end_sector(rq)	((rq)->sector + (rq)->nr_sectors)
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#define rb_entry_rq(node)	rb_entry((node), struct request, rb_node)
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/*
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 * Hack to reuse the csd.list list_head as the fifo time holder while
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 * the request is in the io scheduler. Saves an unsigned long in rq.
 */
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#define rq_fifo_time(rq)	((unsigned long) (rq)->csd.list.next)
#define rq_set_fifo_time(rq,exp)	((rq)->csd.list.next = (void *) (exp))
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#define rq_entry_fifo(ptr)	list_entry((ptr), struct request, queuelist)
#define rq_fifo_clear(rq)	do {		\
	list_del_init(&(rq)->queuelist);	\
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	INIT_LIST_HEAD(&(rq)->csd.list);	\
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	} while (0)

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/*
 * io context count accounting
 */
#define elv_ioc_count_mod(name, __val)				\
	do {							\
		preempt_disable();				\
		__get_cpu_var(name) += (__val);			\
		preempt_enable();				\
	} while (0)

#define elv_ioc_count_inc(name)	elv_ioc_count_mod(name, 1)
#define elv_ioc_count_dec(name)	elv_ioc_count_mod(name, -1)

#define elv_ioc_count_read(name)				\
({								\
	unsigned long __val = 0;				\
	int __cpu;						\
	smp_wmb();						\
	for_each_possible_cpu(__cpu)				\
		__val += per_cpu(name, __cpu);			\
	__val;							\
})

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#endif /* CONFIG_BLOCK */
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#endif