root/include/linux/elevator.h

INCLUDED FROM

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _LINUX_ELEVATOR_H
   3 #define _LINUX_ELEVATOR_H
   4 
   5 #include <linux/percpu.h>
   6 #include <linux/hashtable.h>
   7 
   8 #ifdef CONFIG_BLOCK
   9 
  10 struct io_cq;
  11 struct elevator_type;
  12 #ifdef CONFIG_BLK_DEBUG_FS
  13 struct blk_mq_debugfs_attr;
  14 #endif
  15 
  16 /*
  17  * Return values from elevator merger
  18  */
  19 enum elv_merge {
  20         ELEVATOR_NO_MERGE       = 0,
  21         ELEVATOR_FRONT_MERGE    = 1,
  22         ELEVATOR_BACK_MERGE     = 2,
  23         ELEVATOR_DISCARD_MERGE  = 3,
  24 };
  25 
  26 struct blk_mq_alloc_data;
  27 struct blk_mq_hw_ctx;
  28 
  29 struct elevator_mq_ops {
  30         int (*init_sched)(struct request_queue *, struct elevator_type *);
  31         void (*exit_sched)(struct elevator_queue *);
  32         int (*init_hctx)(struct blk_mq_hw_ctx *, unsigned int);
  33         void (*exit_hctx)(struct blk_mq_hw_ctx *, unsigned int);
  34         void (*depth_updated)(struct blk_mq_hw_ctx *);
  35 
  36         bool (*allow_merge)(struct request_queue *, struct request *, struct bio *);
  37         bool (*bio_merge)(struct blk_mq_hw_ctx *, struct bio *, unsigned int);
  38         int (*request_merge)(struct request_queue *q, struct request **, struct bio *);
  39         void (*request_merged)(struct request_queue *, struct request *, enum elv_merge);
  40         void (*requests_merged)(struct request_queue *, struct request *, struct request *);
  41         void (*limit_depth)(unsigned int, struct blk_mq_alloc_data *);
  42         void (*prepare_request)(struct request *, struct bio *bio);
  43         void (*finish_request)(struct request *);
  44         void (*insert_requests)(struct blk_mq_hw_ctx *, struct list_head *, bool);
  45         struct request *(*dispatch_request)(struct blk_mq_hw_ctx *);
  46         bool (*has_work)(struct blk_mq_hw_ctx *);
  47         void (*completed_request)(struct request *, u64);
  48         void (*requeue_request)(struct request *);
  49         struct request *(*former_request)(struct request_queue *, struct request *);
  50         struct request *(*next_request)(struct request_queue *, struct request *);
  51         void (*init_icq)(struct io_cq *);
  52         void (*exit_icq)(struct io_cq *);
  53 };
  54 
  55 #define ELV_NAME_MAX    (16)
  56 
  57 struct elv_fs_entry {
  58         struct attribute attr;
  59         ssize_t (*show)(struct elevator_queue *, char *);
  60         ssize_t (*store)(struct elevator_queue *, const char *, size_t);
  61 };
  62 
  63 /*
  64  * identifies an elevator type, such as AS or deadline
  65  */
  66 struct elevator_type
  67 {
  68         /* managed by elevator core */
  69         struct kmem_cache *icq_cache;
  70 
  71         /* fields provided by elevator implementation */
  72         struct elevator_mq_ops ops;
  73 
  74         size_t icq_size;        /* see iocontext.h */
  75         size_t icq_align;       /* ditto */
  76         struct elv_fs_entry *elevator_attrs;
  77         const char *elevator_name;
  78         const char *elevator_alias;
  79         const unsigned int elevator_features;
  80         struct module *elevator_owner;
  81 #ifdef CONFIG_BLK_DEBUG_FS
  82         const struct blk_mq_debugfs_attr *queue_debugfs_attrs;
  83         const struct blk_mq_debugfs_attr *hctx_debugfs_attrs;
  84 #endif
  85 
  86         /* managed by elevator core */
  87         char icq_cache_name[ELV_NAME_MAX + 6];  /* elvname + "_io_cq" */
  88         struct list_head list;
  89 };
  90 
  91 #define ELV_HASH_BITS 6
  92 
  93 void elv_rqhash_del(struct request_queue *q, struct request *rq);
  94 void elv_rqhash_add(struct request_queue *q, struct request *rq);
  95 void elv_rqhash_reposition(struct request_queue *q, struct request *rq);
  96 struct request *elv_rqhash_find(struct request_queue *q, sector_t offset);
  97 
  98 /*
  99  * each queue has an elevator_queue associated with it
 100  */
 101 struct elevator_queue
 102 {
 103         struct elevator_type *type;
 104         void *elevator_data;
 105         struct kobject kobj;
 106         struct mutex sysfs_lock;
 107         unsigned int registered:1;
 108         DECLARE_HASHTABLE(hash, ELV_HASH_BITS);
 109 };
 110 
 111 /*
 112  * block elevator interface
 113  */
 114 extern enum elv_merge elv_merge(struct request_queue *, struct request **,
 115                 struct bio *);
 116 extern void elv_merge_requests(struct request_queue *, struct request *,
 117                                struct request *);
 118 extern void elv_merged_request(struct request_queue *, struct request *,
 119                 enum elv_merge);
 120 extern bool elv_attempt_insert_merge(struct request_queue *, struct request *);
 121 extern struct request *elv_former_request(struct request_queue *, struct request *);
 122 extern struct request *elv_latter_request(struct request_queue *, struct request *);
 123 
 124 /*
 125  * io scheduler registration
 126  */
 127 extern int elv_register(struct elevator_type *);
 128 extern void elv_unregister(struct elevator_type *);
 129 
 130 /*
 131  * io scheduler sysfs switching
 132  */
 133 extern ssize_t elv_iosched_show(struct request_queue *, char *);
 134 extern ssize_t elv_iosched_store(struct request_queue *, const char *, size_t);
 135 
 136 extern bool elv_bio_merge_ok(struct request *, struct bio *);
 137 extern struct elevator_queue *elevator_alloc(struct request_queue *,
 138                                         struct elevator_type *);
 139 
 140 /*
 141  * Helper functions.
 142  */
 143 extern struct request *elv_rb_former_request(struct request_queue *, struct request *);
 144 extern struct request *elv_rb_latter_request(struct request_queue *, struct request *);
 145 
 146 /*
 147  * rb support functions.
 148  */
 149 extern void elv_rb_add(struct rb_root *, struct request *);
 150 extern void elv_rb_del(struct rb_root *, struct request *);
 151 extern struct request *elv_rb_find(struct rb_root *, sector_t);
 152 
 153 /*
 154  * Insertion selection
 155  */
 156 #define ELEVATOR_INSERT_FRONT   1
 157 #define ELEVATOR_INSERT_BACK    2
 158 #define ELEVATOR_INSERT_SORT    3
 159 #define ELEVATOR_INSERT_REQUEUE 4
 160 #define ELEVATOR_INSERT_FLUSH   5
 161 #define ELEVATOR_INSERT_SORT_MERGE      6
 162 
 163 #define rq_end_sector(rq)       (blk_rq_pos(rq) + blk_rq_sectors(rq))
 164 #define rb_entry_rq(node)       rb_entry((node), struct request, rb_node)
 165 
 166 #define rq_entry_fifo(ptr)      list_entry((ptr), struct request, queuelist)
 167 #define rq_fifo_clear(rq)       list_del_init(&(rq)->queuelist)
 168 
 169 /*
 170  * Elevator features.
 171  */
 172 
 173 /* Supports zoned block devices sequential write constraint */
 174 #define ELEVATOR_F_ZBD_SEQ_WRITE        (1U << 0)
 175 
 176 #endif /* CONFIG_BLOCK */
 177 #endif