xref: /linux/block/elevator.h (revision f5a6604f7a4405450e4a1f54e5430f47290c500f)
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_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 
35 struct elevator_mq_ops {
36 	int (*init_sched)(struct request_queue *, struct elevator_queue *);
37 	void (*exit_sched)(struct elevator_queue *);
38 	int (*init_hctx)(struct blk_mq_hw_ctx *, unsigned int);
39 	void (*exit_hctx)(struct blk_mq_hw_ctx *, unsigned int);
40 	void (*depth_updated)(struct blk_mq_hw_ctx *);
41 
42 	bool (*allow_merge)(struct request_queue *, struct request *, struct bio *);
43 	bool (*bio_merge)(struct request_queue *, struct bio *, unsigned int);
44 	int (*request_merge)(struct request_queue *q, struct request **, struct bio *);
45 	void (*request_merged)(struct request_queue *, struct request *, enum elv_merge);
46 	void (*requests_merged)(struct request_queue *, struct request *, struct request *);
47 	void (*limit_depth)(blk_opf_t, struct blk_mq_alloc_data *);
48 	void (*prepare_request)(struct request *);
49 	void (*finish_request)(struct request *);
50 	void (*insert_requests)(struct blk_mq_hw_ctx *hctx, struct list_head *list,
51 			blk_insert_t flags);
52 	struct request *(*dispatch_request)(struct blk_mq_hw_ctx *);
53 	bool (*has_work)(struct blk_mq_hw_ctx *);
54 	void (*completed_request)(struct request *, u64);
55 	void (*requeue_request)(struct request *);
56 	struct request *(*former_request)(struct request_queue *, struct request *);
57 	struct request *(*next_request)(struct request_queue *, struct request *);
58 	void (*init_icq)(struct io_cq *);
59 	void (*exit_icq)(struct io_cq *);
60 };
61 
62 #define ELV_NAME_MAX	(16)
63 
64 struct elv_fs_entry {
65 	struct attribute attr;
66 	ssize_t (*show)(struct elevator_queue *, char *);
67 	ssize_t (*store)(struct elevator_queue *, const char *, size_t);
68 };
69 
70 /*
71  * identifies an elevator type, such as AS or deadline
72  */
73 struct elevator_type
74 {
75 	/* managed by elevator core */
76 	struct kmem_cache *icq_cache;
77 
78 	/* fields provided by elevator implementation */
79 	struct elevator_mq_ops ops;
80 
81 	size_t icq_size;	/* see iocontext.h */
82 	size_t icq_align;	/* ditto */
83 	const struct elv_fs_entry *elevator_attrs;
84 	const char *elevator_name;
85 	const char *elevator_alias;
86 	struct module *elevator_owner;
87 #ifdef CONFIG_BLK_DEBUG_FS
88 	const struct blk_mq_debugfs_attr *queue_debugfs_attrs;
89 	const struct blk_mq_debugfs_attr *hctx_debugfs_attrs;
90 #endif
91 
92 	/* managed by elevator core */
93 	char icq_cache_name[ELV_NAME_MAX + 6];	/* elvname + "_io_cq" */
94 	struct list_head list;
95 };
96 
elevator_tryget(struct elevator_type * e)97 static inline bool elevator_tryget(struct elevator_type *e)
98 {
99 	return try_module_get(e->elevator_owner);
100 }
101 
__elevator_get(struct elevator_type * e)102 static inline void __elevator_get(struct elevator_type *e)
103 {
104 	__module_get(e->elevator_owner);
105 }
106 
elevator_put(struct elevator_type * e)107 static inline void elevator_put(struct elevator_type *e)
108 {
109 	module_put(e->elevator_owner);
110 }
111 
112 #define ELV_HASH_BITS 6
113 
114 void elv_rqhash_del(struct request_queue *q, struct request *rq);
115 void elv_rqhash_add(struct request_queue *q, struct request *rq);
116 void elv_rqhash_reposition(struct request_queue *q, struct request *rq);
117 struct request *elv_rqhash_find(struct request_queue *q, sector_t offset);
118 
119 /*
120  * each queue has an elevator_queue associated with it
121  */
122 struct elevator_queue
123 {
124 	struct elevator_type *type;
125 	struct elevator_tags *et;
126 	void *elevator_data;
127 	struct kobject kobj;
128 	struct mutex sysfs_lock;
129 	unsigned long flags;
130 	DECLARE_HASHTABLE(hash, ELV_HASH_BITS);
131 };
132 
133 #define ELEVATOR_FLAG_REGISTERED	0
134 #define ELEVATOR_FLAG_DYING		1
135 #define ELEVATOR_FLAG_ENABLE_WBT_ON_EXIT	2
136 
137 /*
138  * block elevator interface
139  */
140 extern enum elv_merge elv_merge(struct request_queue *, struct request **,
141 		struct bio *);
142 extern void elv_merge_requests(struct request_queue *, struct request *,
143 			       struct request *);
144 extern void elv_merged_request(struct request_queue *, struct request *,
145 		enum elv_merge);
146 extern bool elv_attempt_insert_merge(struct request_queue *, struct request *,
147 				     struct list_head *);
148 extern struct request *elv_former_request(struct request_queue *, struct request *);
149 extern struct request *elv_latter_request(struct request_queue *, struct request *);
150 void elevator_init_mq(struct request_queue *q);
151 
152 /*
153  * io scheduler registration
154  */
155 extern int elv_register(struct elevator_type *);
156 extern void elv_unregister(struct elevator_type *);
157 
158 /*
159  * io scheduler sysfs switching
160  */
161 ssize_t elv_iosched_show(struct gendisk *disk, char *page);
162 ssize_t elv_iosched_store(struct gendisk *disk, const char *page, size_t count);
163 
164 extern bool elv_bio_merge_ok(struct request *, struct bio *);
165 struct elevator_queue *elevator_alloc(struct request_queue *,
166 		struct elevator_type *, struct elevator_tags *);
167 
168 /*
169  * Helper functions.
170  */
171 extern struct request *elv_rb_former_request(struct request_queue *, struct request *);
172 extern struct request *elv_rb_latter_request(struct request_queue *, struct request *);
173 
174 /*
175  * rb support functions.
176  */
177 extern void elv_rb_add(struct rb_root *, struct request *);
178 extern void elv_rb_del(struct rb_root *, struct request *);
179 extern struct request *elv_rb_find(struct rb_root *, sector_t);
180 
181 /*
182  * Insertion selection
183  */
184 #define ELEVATOR_INSERT_FRONT	1
185 #define ELEVATOR_INSERT_BACK	2
186 #define ELEVATOR_INSERT_SORT	3
187 #define ELEVATOR_INSERT_REQUEUE	4
188 #define ELEVATOR_INSERT_FLUSH	5
189 #define ELEVATOR_INSERT_SORT_MERGE	6
190 
191 #define rb_entry_rq(node)	rb_entry((node), struct request, rb_node)
192 
193 #define rq_entry_fifo(ptr)	list_entry((ptr), struct request, queuelist)
194 #define rq_fifo_clear(rq)	list_del_init(&(rq)->queuelist)
195 
196 void blk_mq_sched_reg_debugfs(struct request_queue *q);
197 void blk_mq_sched_unreg_debugfs(struct request_queue *q);
198 
199 #endif /* _ELEVATOR_H */
200