LXR linux/include/linux/elevator.h

   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
  10struct io_cq;
  11struct elevator_type;
  12#ifdef CONFIG_BLK_DEBUG_FS
  13struct blk_mq_debugfs_attr;
  14#endif
  15
  16/*
  17 * Return values from elevator merger
  18 */
  19enum elv_merge {
  20        ELEVATOR_NO_MERGE       = 0,
  21        ELEVATOR_FRONT_MERGE    = 1,
  22        ELEVATOR_BACK_MERGE     = 2,
  23        ELEVATOR_DISCARD_MERGE  = 3,
  24};
  25
  26struct blk_mq_alloc_data;
  27struct blk_mq_hw_ctx;
  28
  29struct 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
  57struct 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 */
  66struct 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
  93void elv_rqhash_del(struct request_queue *q, struct request *rq);
  94void elv_rqhash_add(struct request_queue *q, struct request *rq);
  95void elv_rqhash_reposition(struct request_queue *q, struct request *rq);
  96struct request *elv_rqhash_find(struct request_queue *q, sector_t offset);
  97
  98/*
  99 * each queue has an elevator_queue associated with it
 100 */
 101struct 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 */
 114extern enum elv_merge elv_merge(struct request_queue *, struct request **,
 115                struct bio *);
 116extern void elv_merge_requests(struct request_queue *, struct request *,
 117                               struct request *);
 118extern void elv_merged_request(struct request_queue *, struct request *,
 119                enum elv_merge);
 120extern bool elv_attempt_insert_merge(struct request_queue *, struct request *);
 121extern struct request *elv_former_request(struct request_queue *, struct request *);
 122extern struct request *elv_latter_request(struct request_queue *, struct request *);
 123
 124/*
 125 * io scheduler registration
 126 */
 127extern int elv_register(struct elevator_type *);
 128extern void elv_unregister(struct elevator_type *);
 129
 130/*
 131 * io scheduler sysfs switching
 132 */
 133extern ssize_t elv_iosched_show(struct request_queue *, char *);
 134extern ssize_t elv_iosched_store(struct request_queue *, const char *, size_t);
 135
 136extern bool elv_bio_merge_ok(struct request *, struct bio *);
 137extern struct elevator_queue *elevator_alloc(struct request_queue *,
 138                                        struct elevator_type *);
 139
 140/*
 141 * Helper functions.
 142 */
 143extern struct request *elv_rb_former_request(struct request_queue *, struct request *);
 144extern struct request *elv_rb_latter_request(struct request_queue *, struct request *);
 145
 146/*
 147 * rb support functions.
 148 */
 149extern void elv_rb_add(struct rb_root *, struct request *);
 150extern void elv_rb_del(struct rb_root *, struct request *);
 151extern 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
 178