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