This commit was manufactured by cvs2svn to create branch 'vserver'.

[linux-2.6.git] / block / noop-iosched.c

diff --git a/block/noop-iosched.c b/block/noop-iosched.c
new file mode 100644 (file)
index 0000000..56a7c62
--- /dev/null
+++ b/block/noop-iosched.c
@@ -0,0 +1,118 @@
+/*
+ * 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 void *noop_init_queue(request_queue_t *q, elevator_t *e)
+{
+       struct noop_data *nd;
+
+       nd = kmalloc(sizeof(*nd), GFP_KERNEL);
+       if (!nd)
+               return NULL;
+       INIT_LIST_HEAD(&nd->queue);
+       return nd;
+}
+
+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");