da77526502
Currently we allow any merge, even if the io originates from different processes. This can cause really bad starvation and unfairness, if those ios happen to be synchronous (reads or direct writes). So add a allow_merge hook to the io scheduler ops, so an io scheduler can help decide whether a bio/process combination may be merged with an existing request. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
212 lines
6.5 KiB
C
212 lines
6.5 KiB
C
#ifndef _LINUX_ELEVATOR_H
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#define _LINUX_ELEVATOR_H
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#include <linux/percpu.h>
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#ifdef CONFIG_BLOCK
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typedef int (elevator_merge_fn) (request_queue_t *, struct request **,
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struct bio *);
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typedef void (elevator_merge_req_fn) (request_queue_t *, struct request *, struct request *);
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typedef void (elevator_merged_fn) (request_queue_t *, struct request *, int);
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typedef int (elevator_allow_merge_fn) (request_queue_t *, struct request *, struct bio *);
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typedef int (elevator_dispatch_fn) (request_queue_t *, int);
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typedef void (elevator_add_req_fn) (request_queue_t *, struct request *);
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typedef int (elevator_queue_empty_fn) (request_queue_t *);
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typedef struct request *(elevator_request_list_fn) (request_queue_t *, struct request *);
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typedef void (elevator_completed_req_fn) (request_queue_t *, struct request *);
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typedef int (elevator_may_queue_fn) (request_queue_t *, int);
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typedef int (elevator_set_req_fn) (request_queue_t *, struct request *, gfp_t);
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typedef void (elevator_put_req_fn) (struct request *);
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typedef void (elevator_activate_req_fn) (request_queue_t *, struct request *);
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typedef void (elevator_deactivate_req_fn) (request_queue_t *, struct request *);
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typedef void *(elevator_init_fn) (request_queue_t *);
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typedef void (elevator_exit_fn) (elevator_t *);
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struct elevator_ops
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{
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elevator_merge_fn *elevator_merge_fn;
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elevator_merged_fn *elevator_merged_fn;
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elevator_merge_req_fn *elevator_merge_req_fn;
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elevator_allow_merge_fn *elevator_allow_merge_fn;
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elevator_dispatch_fn *elevator_dispatch_fn;
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elevator_add_req_fn *elevator_add_req_fn;
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elevator_activate_req_fn *elevator_activate_req_fn;
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elevator_deactivate_req_fn *elevator_deactivate_req_fn;
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elevator_queue_empty_fn *elevator_queue_empty_fn;
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elevator_completed_req_fn *elevator_completed_req_fn;
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elevator_request_list_fn *elevator_former_req_fn;
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elevator_request_list_fn *elevator_latter_req_fn;
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elevator_set_req_fn *elevator_set_req_fn;
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elevator_put_req_fn *elevator_put_req_fn;
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elevator_may_queue_fn *elevator_may_queue_fn;
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elevator_init_fn *elevator_init_fn;
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elevator_exit_fn *elevator_exit_fn;
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void (*trim)(struct io_context *);
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};
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#define ELV_NAME_MAX (16)
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struct elv_fs_entry {
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struct attribute attr;
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ssize_t (*show)(elevator_t *, char *);
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ssize_t (*store)(elevator_t *, const char *, size_t);
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};
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/*
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* identifies an elevator type, such as AS or deadline
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*/
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struct elevator_type
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{
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struct list_head list;
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struct elevator_ops ops;
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struct elv_fs_entry *elevator_attrs;
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char elevator_name[ELV_NAME_MAX];
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struct module *elevator_owner;
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};
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/*
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* each queue has an elevator_queue associated with it
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*/
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struct elevator_queue
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{
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struct elevator_ops *ops;
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void *elevator_data;
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struct kobject kobj;
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struct elevator_type *elevator_type;
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struct mutex sysfs_lock;
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struct hlist_head *hash;
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};
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/*
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* block elevator interface
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*/
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extern void elv_dispatch_sort(request_queue_t *, struct request *);
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extern void elv_dispatch_add_tail(request_queue_t *, struct request *);
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extern void elv_add_request(request_queue_t *, struct request *, int, int);
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extern void __elv_add_request(request_queue_t *, struct request *, int, int);
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extern void elv_insert(request_queue_t *, struct request *, int);
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extern int elv_merge(request_queue_t *, struct request **, struct bio *);
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extern void elv_merge_requests(request_queue_t *, struct request *,
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struct request *);
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extern void elv_merged_request(request_queue_t *, struct request *, int);
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extern void elv_dequeue_request(request_queue_t *, struct request *);
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extern void elv_requeue_request(request_queue_t *, struct request *);
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extern int elv_queue_empty(request_queue_t *);
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extern struct request *elv_next_request(struct request_queue *q);
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extern struct request *elv_former_request(request_queue_t *, struct request *);
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extern struct request *elv_latter_request(request_queue_t *, struct request *);
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extern int elv_register_queue(request_queue_t *q);
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extern void elv_unregister_queue(request_queue_t *q);
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extern int elv_may_queue(request_queue_t *, int);
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extern void elv_completed_request(request_queue_t *, struct request *);
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extern int elv_set_request(request_queue_t *, struct request *, gfp_t);
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extern void elv_put_request(request_queue_t *, struct request *);
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/*
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* io scheduler registration
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*/
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extern int elv_register(struct elevator_type *);
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extern void elv_unregister(struct elevator_type *);
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/*
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* io scheduler sysfs switching
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*/
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extern ssize_t elv_iosched_show(request_queue_t *, char *);
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extern ssize_t elv_iosched_store(request_queue_t *, const char *, size_t);
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extern int elevator_init(request_queue_t *, char *);
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extern void elevator_exit(elevator_t *);
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extern int elv_rq_merge_ok(struct request *, struct bio *);
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/*
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* Helper functions.
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*/
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extern struct request *elv_rb_former_request(request_queue_t *, struct request *);
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extern struct request *elv_rb_latter_request(request_queue_t *, struct request *);
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/*
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* rb support functions.
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*/
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extern struct request *elv_rb_add(struct rb_root *, struct request *);
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extern void elv_rb_del(struct rb_root *, struct request *);
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extern struct request *elv_rb_find(struct rb_root *, sector_t);
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/*
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* Return values from elevator merger
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*/
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#define ELEVATOR_NO_MERGE 0
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#define ELEVATOR_FRONT_MERGE 1
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#define ELEVATOR_BACK_MERGE 2
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/*
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* Insertion selection
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*/
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#define ELEVATOR_INSERT_FRONT 1
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#define ELEVATOR_INSERT_BACK 2
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#define ELEVATOR_INSERT_SORT 3
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#define ELEVATOR_INSERT_REQUEUE 4
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/*
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* return values from elevator_may_queue_fn
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*/
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enum {
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ELV_MQUEUE_MAY,
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ELV_MQUEUE_NO,
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ELV_MQUEUE_MUST,
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};
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#define rq_end_sector(rq) ((rq)->sector + (rq)->nr_sectors)
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#define rb_entry_rq(node) rb_entry((node), struct request, rb_node)
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/*
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* Hack to reuse the donelist list_head as the fifo time holder while
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* the request is in the io scheduler. Saves an unsigned long in rq.
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*/
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#define rq_fifo_time(rq) ((unsigned long) (rq)->donelist.next)
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#define rq_set_fifo_time(rq,exp) ((rq)->donelist.next = (void *) (exp))
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#define rq_entry_fifo(ptr) list_entry((ptr), struct request, queuelist)
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#define rq_fifo_clear(rq) do { \
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list_del_init(&(rq)->queuelist); \
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INIT_LIST_HEAD(&(rq)->donelist); \
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} while (0)
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/*
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* io context count accounting
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*/
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#define elv_ioc_count_mod(name, __val) \
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do { \
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preempt_disable(); \
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__get_cpu_var(name) += (__val); \
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preempt_enable(); \
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} while (0)
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#define elv_ioc_count_inc(name) elv_ioc_count_mod(name, 1)
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#define elv_ioc_count_dec(name) elv_ioc_count_mod(name, -1)
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#define elv_ioc_count_read(name) \
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({ \
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unsigned long __val = 0; \
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int __cpu; \
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smp_wmb(); \
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for_each_possible_cpu(__cpu) \
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__val += per_cpu(name, __cpu); \
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__val; \
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})
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#endif /* CONFIG_BLOCK */
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#endif
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