noop-iosched.c 2.5 KB

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