/* SPDX-License-Identifier: GPL-2.0 */

  #ifndef _LINUX_ELEVATOR_H
  #define _LINUX_ELEVATOR_H

  #include <linux/percpu.h>

  #include <linux/hashtable.h>

  #ifdef CONFIG_BLOCK

  struct io_cq;

  struct elevator_type;

  #ifdef CONFIG_BLK_DEBUG_FS
  struct blk_mq_debugfs_attr;
  #endif

  /*
   * Return values from elevator merger
   */
  enum elv_merge {
  	ELEVATOR_NO_MERGE	= 0,
  	ELEVATOR_FRONT_MERGE	= 1,
  	ELEVATOR_BACK_MERGE	= 2,

  	ELEVATOR_DISCARD_MERGE	= 3,

  };

  struct blk_mq_alloc_data;
  struct blk_mq_hw_ctx;
  
  struct elevator_mq_ops {
  	int (*init_sched)(struct request_queue *, struct elevator_type *);
  	void (*exit_sched)(struct elevator_queue *);

  	int (*init_hctx)(struct blk_mq_hw_ctx *, unsigned int);
  	void (*exit_hctx)(struct blk_mq_hw_ctx *, unsigned int);

  	void (*depth_updated)(struct blk_mq_hw_ctx *);

  
  	bool (*allow_merge)(struct request_queue *, struct request *, struct bio *);

  	bool (*bio_merge)(struct blk_mq_hw_ctx *, struct bio *, unsigned int);

  	int (*request_merge)(struct request_queue *q, struct request **, struct bio *);

  	void (*request_merged)(struct request_queue *, struct request *, enum elv_merge);

  	void (*requests_merged)(struct request_queue *, struct request *, struct request *);

  	void (*limit_depth)(unsigned int, struct blk_mq_alloc_data *);

  	void (*prepare_request)(struct request *);

  	void (*finish_request)(struct request *);

  	void (*insert_requests)(struct blk_mq_hw_ctx *, struct list_head *, bool);

  	struct request *(*dispatch_request)(struct blk_mq_hw_ctx *);

  	bool (*has_work)(struct blk_mq_hw_ctx *);

  	void (*completed_request)(struct request *, u64);

  	void (*requeue_request)(struct request *);
  	struct request *(*former_request)(struct request_queue *, struct request *);
  	struct request *(*next_request)(struct request_queue *, struct request *);

  	void (*init_icq)(struct io_cq *);
  	void (*exit_icq)(struct io_cq *);
  };

  #define ELV_NAME_MAX	(16)

  struct elv_fs_entry {
  	struct attribute attr;

  	ssize_t (*show)(struct elevator_queue *, char *);
  	ssize_t (*store)(struct elevator_queue *, const char *, size_t);

  };

  /*
   * identifies an elevator type, such as AS or deadline
   */
  struct elevator_type
  {

  	/* managed by elevator core */
  	struct kmem_cache *icq_cache;
  
  	/* fields provided by elevator implementation */

  	struct elevator_mq_ops ops;

  	size_t icq_size;	/* see iocontext.h */
  	size_t icq_align;	/* ditto */

  	struct elv_fs_entry *elevator_attrs;

  	const char *elevator_name;

  	const char *elevator_alias;

  	const unsigned int elevator_features;

  	struct module *elevator_owner;

  #ifdef CONFIG_BLK_DEBUG_FS
  	const struct blk_mq_debugfs_attr *queue_debugfs_attrs;
  	const struct blk_mq_debugfs_attr *hctx_debugfs_attrs;
  #endif

  
  	/* managed by elevator core */

  	char icq_cache_name[ELV_NAME_MAX + 6];	/* elvname + "_io_cq" */

  	struct list_head list;

  };

  #define ELV_HASH_BITS 6

  void elv_rqhash_del(struct request_queue *q, struct request *rq);
  void elv_rqhash_add(struct request_queue *q, struct request *rq);
  void elv_rqhash_reposition(struct request_queue *q, struct request *rq);
  struct request *elv_rqhash_find(struct request_queue *q, sector_t offset);

  /*

   * each queue has an elevator_queue associated with it

   */
  struct elevator_queue
  {

  	struct elevator_type *type;

  	void *elevator_data;
  	struct kobject kobj;

  	struct mutex sysfs_lock;

  	unsigned int registered:1;

  	DECLARE_HASHTABLE(hash, ELV_HASH_BITS);

  };
  
  /*
   * block elevator interface
   */

  extern enum elv_merge elv_merge(struct request_queue *, struct request **,
  		struct bio *);

  extern void elv_merge_requests(struct request_queue *, struct request *,

  			       struct request *);

  extern void elv_merged_request(struct request_queue *, struct request *,
  		enum elv_merge);

  extern bool elv_attempt_insert_merge(struct request_queue *, struct request *);

  extern struct request *elv_former_request(struct request_queue *, struct request *);
  extern struct request *elv_latter_request(struct request_queue *, struct request *);

  
  /*
   * io scheduler registration
   */

  extern int elv_register(struct elevator_type *);

  extern void elv_unregister(struct elevator_type *);
  
  /*
   * io scheduler sysfs switching
   */

  extern ssize_t elv_iosched_show(struct request_queue *, char *);
  extern ssize_t elv_iosched_store(struct request_queue *, const char *, size_t);

  extern bool elv_bio_merge_ok(struct request *, struct bio *);

  extern struct elevator_queue *elevator_alloc(struct request_queue *,
  					struct elevator_type *);

  
  /*

   * Helper functions.
   */

  extern struct request *elv_rb_former_request(struct request_queue *, struct request *);
  extern struct request *elv_rb_latter_request(struct request_queue *, struct request *);

  
  /*
   * rb support functions.
   */

  extern void 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);
  
  /*

   * Insertion selection
   */
  #define ELEVATOR_INSERT_FRONT	1
  #define ELEVATOR_INSERT_BACK	2
  #define ELEVATOR_INSERT_SORT	3

  #define ELEVATOR_INSERT_REQUEUE	4

  #define ELEVATOR_INSERT_FLUSH	5

  #define ELEVATOR_INSERT_SORT_MERGE	6

  #define rq_end_sector(rq)	(blk_rq_pos(rq) + blk_rq_sectors(rq))

  #define rb_entry_rq(node)	rb_entry((node), struct request, rb_node)

  #define rq_entry_fifo(ptr)	list_entry((ptr), struct request, queuelist)

  #define rq_fifo_clear(rq)	list_del_init(&(rq)->queuelist)

  /*
   * Elevator features.
   */
  
  /* Supports zoned block devices sequential write constraint */
  #define ELEVATOR_F_ZBD_SEQ_WRITE	(1U << 0)

  #endif /* CONFIG_BLOCK */

  #endif