xref: /linux/block/elevator.h (revision b8e7cd09ae543c1d384677b3d43e009a0e8647ca)
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 
9 struct io_cq;
10 struct elevator_type;
11 struct blk_mq_debugfs_attr;
12 
13 /*
14  * Return values from elevator merger
15  */
16 enum elv_merge {
17 	ELEVATOR_NO_MERGE	= 0,
18 	ELEVATOR_FRONT_MERGE	= 1,
19 	ELEVATOR_BACK_MERGE	= 2,
20 	ELEVATOR_DISCARD_MERGE	= 3,
21 };
22 
23 struct blk_mq_alloc_data;
24 struct blk_mq_hw_ctx;
25 
26 struct elevator_mq_ops {
27 	int (*init_sched)(struct request_queue *, struct elevator_type *);
28 	void (*exit_sched)(struct elevator_queue *);
29 	int (*init_hctx)(struct blk_mq_hw_ctx *, unsigned int);
30 	void (*exit_hctx)(struct blk_mq_hw_ctx *, unsigned int);
31 	void (*depth_updated)(struct blk_mq_hw_ctx *);
32 
33 	bool (*allow_merge)(struct request_queue *, struct request *, struct bio *);
34 	bool (*bio_merge)(struct request_queue *, struct bio *, unsigned int);
35 	int (*request_merge)(struct request_queue *q, struct request **, struct bio *);
36 	void (*request_merged)(struct request_queue *, struct request *, enum elv_merge);
37 	void (*requests_merged)(struct request_queue *, struct request *, struct request *);
38 	void (*limit_depth)(blk_opf_t, struct blk_mq_alloc_data *);
39 	void (*prepare_request)(struct request *);
40 	void (*finish_request)(struct request *);
41 	void (*insert_requests)(struct blk_mq_hw_ctx *hctx, struct list_head *list,
42 			blk_insert_t flags);
43 	struct request *(*dispatch_request)(struct blk_mq_hw_ctx *);
44 	bool (*has_work)(struct blk_mq_hw_ctx *);
45 	void (*completed_request)(struct request *, u64);
46 	void (*requeue_request)(struct request *);
47 	struct request *(*former_request)(struct request_queue *, struct request *);
48 	struct request *(*next_request)(struct request_queue *, struct request *);
49 	void (*init_icq)(struct io_cq *);
50 	void (*exit_icq)(struct io_cq *);
51 };
52 
53 #define ELV_NAME_MAX	(16)
54 
55 struct elv_fs_entry {
56 	struct attribute attr;
57 	ssize_t (*show)(struct elevator_queue *, char *);
58 	ssize_t (*store)(struct elevator_queue *, const char *, size_t);
59 };
60 
61 /*
62  * identifies an elevator type, such as AS or deadline
63  */
64 struct elevator_type
65 {
66 	/* managed by elevator core */
67 	struct kmem_cache *icq_cache;
68 
69 	/* fields provided by elevator implementation */
70 	struct elevator_mq_ops ops;
71 
72 	size_t icq_size;	/* see iocontext.h */
73 	size_t icq_align;	/* ditto */
74 	struct elv_fs_entry *elevator_attrs;
75 	const char *elevator_name;
76 	const char *elevator_alias;
77 	struct module *elevator_owner;
78 #ifdef CONFIG_BLK_DEBUG_FS
79 	const struct blk_mq_debugfs_attr *queue_debugfs_attrs;
80 	const struct blk_mq_debugfs_attr *hctx_debugfs_attrs;
81 #endif
82 
83 	/* managed by elevator core */
84 	char icq_cache_name[ELV_NAME_MAX + 6];	/* elvname + "_io_cq" */
85 	struct list_head list;
86 };
87 
elevator_tryget(struct elevator_type * e)88 static inline bool elevator_tryget(struct elevator_type *e)
89 {
90 	return try_module_get(e->elevator_owner);
91 }
92 
__elevator_get(struct elevator_type * e)93 static inline void __elevator_get(struct elevator_type *e)
94 {
95 	__module_get(e->elevator_owner);
96 }
97 
elevator_put(struct elevator_type * e)98 static inline void elevator_put(struct elevator_type *e)
99 {
100 	module_put(e->elevator_owner);
101 }
102 
103 #define ELV_HASH_BITS 6
104 
105 void elv_rqhash_del(struct request_queue *q, struct request *rq);
106 void elv_rqhash_add(struct request_queue *q, struct request *rq);
107 void elv_rqhash_reposition(struct request_queue *q, struct request *rq);
108 struct request *elv_rqhash_find(struct request_queue *q, sector_t offset);
109 
110 /*
111  * each queue has an elevator_queue associated with it
112  */
113 struct elevator_queue
114 {
115 	struct elevator_type *type;
116 	void *elevator_data;
117 	struct kobject kobj;
118 	struct mutex sysfs_lock;
119 	unsigned long flags;
120 	DECLARE_HASHTABLE(hash, ELV_HASH_BITS);
121 };
122 
123 #define ELEVATOR_FLAG_REGISTERED	0
124 #define ELEVATOR_FLAG_DISABLE_WBT	1
125 
126 /*
127  * block elevator interface
128  */
129 extern enum elv_merge elv_merge(struct request_queue *, struct request **,
130 		struct bio *);
131 extern void elv_merge_requests(struct request_queue *, struct request *,
132 			       struct request *);
133 extern void elv_merged_request(struct request_queue *, struct request *,
134 		enum elv_merge);
135 extern bool elv_attempt_insert_merge(struct request_queue *, struct request *,
136 				     struct list_head *);
137 extern struct request *elv_former_request(struct request_queue *, struct request *);
138 extern struct request *elv_latter_request(struct request_queue *, struct request *);
139 void elevator_init_mq(struct request_queue *q);
140 
141 /*
142  * io scheduler registration
143  */
144 extern int elv_register(struct elevator_type *);
145 extern void elv_unregister(struct elevator_type *);
146 
147 /*
148  * io scheduler sysfs switching
149  */
150 ssize_t elv_iosched_show(struct gendisk *disk, char *page);
151 int elv_iosched_load_module(struct gendisk *disk, const char *page,
152 			    size_t count);
153 ssize_t elv_iosched_store(struct gendisk *disk, const char *page, size_t count);
154 
155 extern bool elv_bio_merge_ok(struct request *, struct bio *);
156 extern struct elevator_queue *elevator_alloc(struct request_queue *,
157 					struct elevator_type *);
158 
159 /*
160  * Helper functions.
161  */
162 extern struct request *elv_rb_former_request(struct request_queue *, struct request *);
163 extern struct request *elv_rb_latter_request(struct request_queue *, struct request *);
164 
165 /*
166  * rb support functions.
167  */
168 extern void elv_rb_add(struct rb_root *, struct request *);
169 extern void elv_rb_del(struct rb_root *, struct request *);
170 extern struct request *elv_rb_find(struct rb_root *, sector_t);
171 
172 /*
173  * Insertion selection
174  */
175 #define ELEVATOR_INSERT_FRONT	1
176 #define ELEVATOR_INSERT_BACK	2
177 #define ELEVATOR_INSERT_SORT	3
178 #define ELEVATOR_INSERT_REQUEUE	4
179 #define ELEVATOR_INSERT_FLUSH	5
180 #define ELEVATOR_INSERT_SORT_MERGE	6
181 
182 #define rb_entry_rq(node)	rb_entry((node), struct request, rb_node)
183 
184 #define rq_entry_fifo(ptr)	list_entry((ptr), struct request, queuelist)
185 #define rq_fifo_clear(rq)	list_del_init(&(rq)->queuelist)
186 
187 #endif /* _ELEVATOR_H */
188