/* * elevator noop */ #include <linux/blkdev.h> #include <linux/elevator.h> #include <linux/bio.h> #include <linux/module.h> #include <linux/slab.h> #include <linux/init.h> struct noop_data { struct list_head queue; }; static void noop_merged_requests(struct request_queue *q, struct request *rq, struct request *next) { list_del_init(&next->queuelist); } static int noop_dispatch(struct request_queue *q, int force) { struct noop_data *nd = q->elevator->elevator_data; if (!list_empty(&nd->queue)) { struct request *rq; rq = list_entry(nd->queue.next, struct request, queuelist); list_del_init(&rq->queuelist); elv_dispatch_sort(q, rq); return 1; } return 0; } static void noop_add_request(struct request_queue *q, struct request *rq) { struct noop_data *nd = q->elevator->elevator_data; list_add_tail(&rq->queuelist, &nd->queue); } static struct request * noop_former_request(struct request_queue *q, struct request *rq) { struct noop_data *nd = q->elevator->elevator_data; if (rq->queuelist.prev == &nd->queue) return NULL; return list_entry(rq->queuelist.prev, struct request, queuelist); } static struct request * noop_latter_request(struct request_queue *q, struct request *rq) { struct noop_data *nd = q->elevator->elevator_data; if (rq->queuelist.next == &nd->queue) return NULL; return list_entry(rq->queuelist.next, struct request, queuelist); } static void *noop_init_queue(struct request_queue *q) { struct noop_data *nd; nd = kmalloc_node(sizeof(*nd), GFP_KERNEL, q->node); if (!nd) return NULL; INIT_LIST_HEAD(&nd->queue); return nd; } static void noop_exit_queue(struct elevator_queue *e) { struct noop_data *nd = e->elevator_data; BUG_ON(!list_empty(&nd->queue)); kfree(nd); } static struct elevator_type elevator_noop = { .ops = { .elevator_merge_req_fn = noop_merged_requests, .elevator_dispatch_fn = noop_dispatch, .elevator_add_req_fn = noop_add_request, .elevator_former_req_fn = noop_former_request, .elevator_latter_req_fn = noop_latter_request, .elevator_init_fn = noop_init_queue, .elevator_exit_fn = noop_exit_queue, }, .elevator_name = "noop", .elevator_owner = THIS_MODULE, }; static int __init noop_init(void) { elv_register(&elevator_noop); return 0; } static void __exit noop_exit(void) { elv_unregister(&elevator_noop); } module_init(noop_init); module_exit(noop_exit); MODULE_AUTHOR("Jens Axboe"); MODULE_LICENSE("GPL"); MODULE_DESCRIPTION("No-op IO scheduler");