LXR linux/block/noop-iosched.c

   1/*
   2 * elevator noop
   3 */
   4#include <linux/blkdev.h>
   5#include <linux/elevator.h>
   6#include <linux/bio.h>
   7#include <linux/module.h>
   8#include <linux/slab.h>
   9#include <linux/init.h>
  10
  11struct noop_data {
  12        struct list_head queue;
  13};
  14
  15static void noop_merged_requests(struct request_queue *q, struct request *rq,
  16                                 struct request *next)
  17{
  18        list_del_init(&next->queuelist);
  19}
  20
  21static int noop_dispatch(struct request_queue *q, int force)
  22{
  23        struct noop_data *nd = q->elevator->elevator_data;
  24
  25        if (!list_empty(&nd->queue)) {
  26                struct request *rq;
  27                rq = list_entry(nd->queue.next, struct request, queuelist);
  28                list_del_init(&rq->queuelist);
  29                elv_dispatch_sort(q, rq);
  30                return 1;
  31        }
  32        return 0;
  33}
  34
  35static void noop_add_request(struct request_queue *q, struct request *rq)
  36{
  37        struct noop_data *nd = q->elevator->elevator_data;
  38
  39        list_add_tail(&rq->queuelist, &nd->queue);
  40}
  41
  42static int noop_queue_empty(struct request_queue *q)
  43{
  44        struct noop_data *nd = q->elevator->elevator_data;
  45
  46        return list_empty(&nd->queue);
  47}
  48
  49static struct request *
  50noop_former_request(struct request_queue *q, struct request *rq)
  51{
  52        struct noop_data *nd = q->elevator->elevator_data;
  53
  54        if (rq->queuelist.prev == &nd->queue)
  55                return NULL;
  56        return list_entry(rq->queuelist.prev, struct request, queuelist);
  57}
  58
  59static struct request *
  60noop_latter_request(struct request_queue *q, struct request *rq)
  61{
  62        struct noop_data *nd = q->elevator->elevator_data;
  63
  64        if (rq->queuelist.next == &nd->queue)
  65                return NULL;
  66        return list_entry(rq->queuelist.next, struct request, queuelist);
  67}
  68
  69static void *noop_init_queue(struct request_queue *q)
  70{
  71        struct noop_data *nd;
  72
  73        nd = kmalloc_node(sizeof(*nd), GFP_KERNEL, q->node);
  74        if (!nd)
  75                return NULL;
  76        INIT_LIST_HEAD(&nd->queue);
  77        return nd;
  78}
  79
  80static void noop_exit_queue(struct elevator_queue *e)
  81{
  82        struct noop_data *nd = e->elevator_data;
  83
  84        BUG_ON(!list_empty(&nd->queue));
  85        kfree(nd);
  86}
  87
  88static struct elevator_type elevator_noop = {
  89        .ops = {
  90                .elevator_merge_req_fn          = noop_merged_requests,
  91                .elevator_dispatch_fn           = noop_dispatch,
  92                .elevator_add_req_fn            = noop_add_request,
  93                .elevator_queue_empty_fn        = noop_queue_empty,
  94                .elevator_former_req_fn         = noop_former_request,
  95                .elevator_latter_req_fn         = noop_latter_request,
  96                .elevator_init_fn               = noop_init_queue,
  97                .elevator_exit_fn               = noop_exit_queue,
  98        },
  99        .elevator_name = "noop",
 100        .elevator_owner = THIS_MODULE,
 101};
 102
 103static int __init noop_init(void)
 104{
 105        elv_register(&elevator_noop);
 106
 107        return 0;
 108}
 109
 110static void __exit noop_exit(void)
 111{
 112        elv_unregister(&elevator_noop);
 113}
 114
 115module_init(noop_init);
 116module_exit(noop_exit);
 117
 118
 119MODULE_AUTHOR("Jens Axboe");
 120MODULE_LICENSE("GPL");
 121MODULE_DESCRIPTION("No-op IO scheduler");
 122