1 files changed, 119 insertions, 0 deletions
diff --git a/block/noop-iosched.c b/block/noop-iosched.c
new file mode 100644
index 000000000000..f370e4a7fe6d
--- /dev/null
+++ b/block/noop-iosched.c
@@ -0,0 +1,119 @@
+/*
+ * elevator noop
+ */
+#include <linux/blkdev.h>
+#include <linux/elevator.h>
+#include <linux/bio.h>
+#include <linux/module.h>
+#include <linux/init.h>
+
+struct noop_data {
+	struct list_head queue;
+};
+
+static void noop_merged_requests(request_queue_t *q, struct request *rq,
+				 struct request *next)
+{
+	list_del_init(&next->queuelist);
+}
+
+static int noop_dispatch(request_queue_t *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(request_queue_t *q, struct request *rq)
+{
+	struct noop_data *nd = q->elevator->elevator_data;
+
+	list_add_tail(&rq->queuelist, &nd->queue);
+}
+
+static int noop_queue_empty(request_queue_t *q)
+{
+	struct noop_data *nd = q->elevator->elevator_data;
+
+	return list_empty(&nd->queue);
+}
+
+static struct request *
+noop_former_request(request_queue_t *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(request_queue_t *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 int noop_init_queue(request_queue_t *q, elevator_t *e)
+{
+	struct noop_data *nd;
+
+	nd = kmalloc(sizeof(*nd), GFP_KERNEL);
+	if (!nd)
+		return -ENOMEM;
+	INIT_LIST_HEAD(&nd->queue);
+	e->elevator_data = nd;
+	return 0;
+}
+
+static void noop_exit_queue(elevator_t *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_queue_empty_fn	= noop_queue_empty,
+		.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");