elevator.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2#ifndef _ELEVATOR_H
  3#define _ELEVATOR_H
  4
  5#include <linux/percpu.h>
  6#include <linux/hashtable.h>
  7#include "blk-mq.h"
  8
  9struct io_cq;
 10struct elevator_type;
 11struct blk_mq_debugfs_attr;
 12
 13/*
 14 * Return values from elevator merger
 15 */
 16enum elv_merge {
 17	ELEVATOR_NO_MERGE	= 0,
 18	ELEVATOR_FRONT_MERGE	= 1,
 19	ELEVATOR_BACK_MERGE	= 2,
 20	ELEVATOR_DISCARD_MERGE	= 3,
 21};
 22
 23struct blk_mq_alloc_data;
 24struct blk_mq_hw_ctx;
 25
 26struct elevator_tags {
 27	/* num. of hardware queues for which tags are allocated */
 28	unsigned int nr_hw_queues;
 29	/* depth used while allocating tags */
 30	unsigned int nr_requests;
 31	/* shared tag is stored at index 0 */
 32	struct blk_mq_tags *tags[];
 33};
 34
 35struct elevator_resources {
 36	/* holds elevator data */
 37	void *data;
 38	/* holds elevator tags */
 39	struct elevator_tags *et;
 40};
 41
 42/* Holding context data for changing elevator */
 43struct elv_change_ctx {
 44	const char *name;
 45	bool no_uevent;
 46
 47	/* for unregistering old elevator */
 48	struct elevator_queue *old;
 49	/* for registering new elevator */
 50	struct elevator_queue *new;
 51	/* store elevator type */
 52	struct elevator_type *type;
 53	/* store elevator resources */
 54	struct elevator_resources res;
 55};
 56
 57struct elevator_mq_ops {
 58	int (*init_sched)(struct request_queue *, struct elevator_queue *);
 59	void (*exit_sched)(struct elevator_queue *);
 60	int (*init_hctx)(struct blk_mq_hw_ctx *, unsigned int);
 61	void (*exit_hctx)(struct blk_mq_hw_ctx *, unsigned int);
 62	void (*depth_updated)(struct request_queue *);
 63	void *(*alloc_sched_data)(struct request_queue *);
 64	void (*free_sched_data)(void *);
 65
 66	bool (*allow_merge)(struct request_queue *, struct request *, struct bio *);
 67	bool (*bio_merge)(struct request_queue *, struct bio *, unsigned int);
 68	int (*request_merge)(struct request_queue *q, struct request **, struct bio *);
 69	void (*request_merged)(struct request_queue *, struct request *, enum elv_merge);
 70	void (*requests_merged)(struct request_queue *, struct request *, struct request *);
 71	void (*limit_depth)(blk_opf_t, struct blk_mq_alloc_data *);
 72	void (*prepare_request)(struct request *);
 73	void (*finish_request)(struct request *);
 74	void (*insert_requests)(struct blk_mq_hw_ctx *hctx, struct list_head *list,
 75			blk_insert_t flags);
 76	struct request *(*dispatch_request)(struct blk_mq_hw_ctx *);
 77	bool (*has_work)(struct blk_mq_hw_ctx *);
 78	void (*completed_request)(struct request *, u64);
 79	void (*requeue_request)(struct request *);
 80	struct request *(*former_request)(struct request_queue *, struct request *);
 81	struct request *(*next_request)(struct request_queue *, struct request *);
 82	void (*init_icq)(struct io_cq *);
 83	void (*exit_icq)(struct io_cq *);
 84};
 85
 86#define ELV_NAME_MAX	(16)
 87
 88struct elv_fs_entry {
 89	struct attribute attr;
 90	ssize_t (*show)(struct elevator_queue *, char *);
 91	ssize_t (*store)(struct elevator_queue *, const char *, size_t);
 92};
 93
 94/*
 95 * identifies an elevator type, such as AS or deadline
 96 */
 97struct elevator_type
 98{
 99	/* managed by elevator core */
100	struct kmem_cache *icq_cache;
101
102	/* fields provided by elevator implementation */
103	struct elevator_mq_ops ops;
104
105	size_t icq_size;	/* see iocontext.h */
106	size_t icq_align;	/* ditto */
107	const struct elv_fs_entry *elevator_attrs;
108	const char *elevator_name;
109	const char *elevator_alias;
110	struct module *elevator_owner;
111#ifdef CONFIG_BLK_DEBUG_FS
112	const struct blk_mq_debugfs_attr *queue_debugfs_attrs;
113	const struct blk_mq_debugfs_attr *hctx_debugfs_attrs;
114#endif
115
116	/* managed by elevator core */
117	char icq_cache_name[ELV_NAME_MAX + 6];	/* elvname + "_io_cq" */
118	struct list_head list;
119};
120
121static inline bool elevator_tryget(struct elevator_type *e)
122{
123	return try_module_get(e->elevator_owner);
124}
125
126static inline void __elevator_get(struct elevator_type *e)
127{
128	__module_get(e->elevator_owner);
129}
130
131static inline void elevator_put(struct elevator_type *e)
132{
133	module_put(e->elevator_owner);
134}
135
136#define ELV_HASH_BITS 6
137
138void elv_rqhash_del(struct request_queue *q, struct request *rq);
139void elv_rqhash_add(struct request_queue *q, struct request *rq);
140void elv_rqhash_reposition(struct request_queue *q, struct request *rq);
141struct request *elv_rqhash_find(struct request_queue *q, sector_t offset);
142
143/*
144 * each queue has an elevator_queue associated with it
145 */
146struct elevator_queue
147{
148	struct elevator_type *type;
149	struct elevator_tags *et;
150	void *elevator_data;
151	struct kobject kobj;
152	struct mutex sysfs_lock;
153	unsigned long flags;
154	DECLARE_HASHTABLE(hash, ELV_HASH_BITS);
155};
156
157#define ELEVATOR_FLAG_REGISTERED	0
158#define ELEVATOR_FLAG_DYING		1
159
160/*
161 * block elevator interface
162 */
163extern enum elv_merge elv_merge(struct request_queue *, struct request **,
164		struct bio *);
165extern void elv_merge_requests(struct request_queue *, struct request *,
166			       struct request *);
167extern void elv_merged_request(struct request_queue *, struct request *,
168		enum elv_merge);
169extern bool elv_attempt_insert_merge(struct request_queue *, struct request *,
170				     struct list_head *);
171extern struct request *elv_former_request(struct request_queue *, struct request *);
172extern struct request *elv_latter_request(struct request_queue *, struct request *);
173
174/*
175 * io scheduler registration
176 */
177extern int elv_register(struct elevator_type *);
178extern void elv_unregister(struct elevator_type *);
179
180/*
181 * io scheduler sysfs switching
182 */
183ssize_t elv_iosched_show(struct gendisk *disk, char *page);
184ssize_t elv_iosched_store(struct gendisk *disk, const char *page, size_t count);
185
186extern bool elv_bio_merge_ok(struct request *, struct bio *);
187struct elevator_queue *elevator_alloc(struct request_queue *,
188		struct elevator_type *, struct elevator_resources *);
189
190/*
191 * Helper functions.
192 */
193extern struct request *elv_rb_former_request(struct request_queue *, struct request *);
194extern struct request *elv_rb_latter_request(struct request_queue *, struct request *);
195
196/*
197 * rb support functions.
198 */
199extern void elv_rb_add(struct rb_root *, struct request *);
200extern void elv_rb_del(struct rb_root *, struct request *);
201extern struct request *elv_rb_find(struct rb_root *, sector_t);
202
203/*
204 * Insertion selection
205 */
206#define ELEVATOR_INSERT_FRONT	1
207#define ELEVATOR_INSERT_BACK	2
208#define ELEVATOR_INSERT_SORT	3
209#define ELEVATOR_INSERT_REQUEUE	4
210#define ELEVATOR_INSERT_FLUSH	5
211#define ELEVATOR_INSERT_SORT_MERGE	6
212
213#define rb_entry_rq(node)	rb_entry((node), struct request, rb_node)
214
215#define rq_entry_fifo(ptr)	list_entry((ptr), struct request, queuelist)
216#define rq_fifo_clear(rq)	list_del_init(&(rq)->queuelist)
217
218void blk_mq_sched_reg_debugfs(struct request_queue *q);
219void blk_mq_sched_unreg_debugfs(struct request_queue *q);
220
221#endif /* _ELEVATOR_H */