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 struct request * 43noop_former_request(struct request_queue *q, struct request *rq) 44{ 45 struct noop_data *nd = q->elevator->elevator_data; 46 47 if (rq->queuelist.prev == &nd->queue) 48 return NULL; 49 return list_entry(rq->queuelist.prev, struct request, queuelist); 50} 51 52static struct request * 53noop_latter_request(struct request_queue *q, struct request *rq) 54{ 55 struct noop_data *nd = q->elevator->elevator_data; 56 57 if (rq->queuelist.next == &nd->queue) 58 return NULL; 59 return list_entry(rq->queuelist.next, struct request, queuelist); 60} 61 62static int noop_init_queue(struct request_queue *q, struct elevator_type *e) 63{ 64 struct noop_data *nd; 65 struct elevator_queue *eq; 66 67 eq = elevator_alloc(q, e); 68 if (!eq) 69 return -ENOMEM; 70 71 nd = kmalloc_node(sizeof(*nd), GFP_KERNEL, q->node); 72 if (!nd) { 73 kobject_put(&eq->kobj); 74 return -ENOMEM; 75 } 76 eq->elevator_data = nd; 77 78 INIT_LIST_HEAD(&nd->queue); 79 80 spin_lock_irq(q->queue_lock); 81 q->elevator = eq; 82 spin_unlock_irq(q->queue_lock); 83 return 0; 84} 85 86static void noop_exit_queue(struct elevator_queue *e) 87{ 88 struct noop_data *nd = e->elevator_data; 89 90 BUG_ON(!list_empty(&nd->queue)); 91 kfree(nd); 92} 93 94static struct elevator_type elevator_noop = { 95 .ops = { 96 .elevator_merge_req_fn = noop_merged_requests, 97 .elevator_dispatch_fn = noop_dispatch, 98 .elevator_add_req_fn = noop_add_request, 99 .elevator_former_req_fn = noop_former_request, 100 .elevator_latter_req_fn = noop_latter_request, 101 .elevator_init_fn = noop_init_queue, 102 .elevator_exit_fn = noop_exit_queue, 103 }, 104 .elevator_name = "noop", 105 .elevator_owner = THIS_MODULE, 106}; 107 108static int __init noop_init(void) 109{ 110 return elv_register(&elevator_noop); 111} 112 113static void __exit noop_exit(void) 114{ 115 elv_unregister(&elevator_noop); 116} 117 118module_init(noop_init); 119module_exit(noop_exit); 120 121 122MODULE_AUTHOR("Jens Axboe"); 123MODULE_LICENSE("GPL"); 124MODULE_DESCRIPTION("No-op IO scheduler"); 125