5a7c47eefb
The original implementation directly used dispatch queue. As new generic dispatch queue imposes stricter rules over ioscheds and dispatch queue usage, this direct use becomes somewhat problematic. This patch reimplements noop-iosched such that it complies to generic iosched model better. Request merging with q->last_merge and rq->queuelist.prev/next work again now. Signed-off-by: Tejun Heo <htejun@gmail.com> Signed-off-by: Jens Axboe <axboe@suse.de
120 lines
2.6 KiB
C
120 lines
2.6 KiB
C
/*
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* elevator noop
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*/
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#include <linux/blkdev.h>
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#include <linux/elevator.h>
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#include <linux/bio.h>
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#include <linux/module.h>
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#include <linux/init.h>
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struct noop_data {
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struct list_head queue;
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};
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static void noop_merged_requests(request_queue_t *q, struct request *rq,
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struct request *next)
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{
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list_del_init(&next->queuelist);
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}
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static int noop_dispatch(request_queue_t *q, int force)
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{
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struct noop_data *nd = q->elevator->elevator_data;
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if (!list_empty(&nd->queue)) {
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struct request *rq;
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rq = list_entry(nd->queue.next, struct request, queuelist);
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list_del_init(&rq->queuelist);
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elv_dispatch_sort(q, rq);
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return 1;
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}
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return 0;
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}
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static void noop_add_request(request_queue_t *q, struct request *rq)
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{
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struct noop_data *nd = q->elevator->elevator_data;
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list_add_tail(&rq->queuelist, &nd->queue);
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}
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static int noop_queue_empty(request_queue_t *q)
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{
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struct noop_data *nd = q->elevator->elevator_data;
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return list_empty(&nd->queue);
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}
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static struct request *
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noop_former_request(request_queue_t *q, struct request *rq)
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{
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struct noop_data *nd = q->elevator->elevator_data;
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if (rq->queuelist.prev == &nd->queue)
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return NULL;
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return list_entry(rq->queuelist.prev, struct request, queuelist);
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}
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static struct request *
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noop_latter_request(request_queue_t *q, struct request *rq)
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{
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struct noop_data *nd = q->elevator->elevator_data;
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if (rq->queuelist.next == &nd->queue)
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return NULL;
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return list_entry(rq->queuelist.next, struct request, queuelist);
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}
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static int noop_init_queue(request_queue_t *q, elevator_t *e)
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{
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struct noop_data *nd;
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nd = kmalloc(sizeof(*nd), GFP_KERNEL);
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if (!nd)
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return -ENOMEM;
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INIT_LIST_HEAD(&nd->queue);
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e->elevator_data = nd;
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return 0;
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}
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static void noop_exit_queue(elevator_t *e)
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{
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struct noop_data *nd = e->elevator_data;
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BUG_ON(!list_empty(&nd->queue));
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kfree(nd);
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}
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static struct elevator_type elevator_noop = {
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.ops = {
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.elevator_merge_req_fn = noop_merged_requests,
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.elevator_dispatch_fn = noop_dispatch,
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.elevator_add_req_fn = noop_add_request,
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.elevator_queue_empty_fn = noop_queue_empty,
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.elevator_former_req_fn = noop_former_request,
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.elevator_latter_req_fn = noop_latter_request,
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.elevator_init_fn = noop_init_queue,
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.elevator_exit_fn = noop_exit_queue,
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},
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.elevator_name = "noop",
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.elevator_owner = THIS_MODULE,
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};
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static int __init noop_init(void)
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{
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return elv_register(&elevator_noop);
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}
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static void __exit noop_exit(void)
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{
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elv_unregister(&elevator_noop);
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}
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module_init(noop_init);
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module_exit(noop_exit);
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MODULE_AUTHOR("Jens Axboe");
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("No-op IO scheduler");
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