/* * 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; struct request *rq; rq = list_first_entry_or_null(&nd->queue, struct request, queuelist); if (rq) { 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_prev_entry(rq, 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_next_entry(rq, queuelist); } static int noop_init_queue(struct request_queue *q, struct elevator_type *e) { struct noop_data *nd; struct elevator_queue *eq; eq = elevator_alloc(q, e); if (!eq) return -ENOMEM; nd = kmalloc_node(sizeof(*nd), GFP_KERNEL, q->node); if (!nd) { kobject_put(&eq->kobj); return -ENOMEM; } eq->elevator_data = nd; INIT_LIST_HEAD(&nd->queue); spin_lock_irq(q->queue_lock); q->elevator = eq; spin_unlock_irq(q->queue_lock); return 0; } 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) { return elv_register(&elevator_noop); } 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");