1 files changed, 126 insertions, 0 deletions
diff --git a/kernel/queue.c b/kernel/queue.c
new file mode 100644
index 0000000..30a0112
--- /dev/null
+++ b/kernel/queue.c
@@ -0,0 +1,126 @@
+/*
+ * queue.c - queues for requests to be submitted (tx_queue) 
+ *           and outstanding requests (rx_queue)
+ * Copyright (C) 2006 Thorsten Zitterell <thorsten@zitterell.de>
+ */
+
+#include <linux/blkdev.h>
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/fs.h>
+
+#include <linux/spinlock.h>
+
+#include <linux/in.h>
+
+#include "dnbd.h"
+#include "queue.h"
+
+/* enqueue to a queue */
+void dnbd_enq_request(dnbd_queue_t * q, struct request *req, int wakeup)
+{
+	unsigned long flags;
+	spin_lock_irqsave(&q->lock, flags);
+	list_add(&req->queuelist, &q->head);
+	spin_unlock_irqrestore(&q->lock,flags);
+	if (wakeup)
+		wake_up(&q->waiters);
+}
+
+/* dequeue from a queue with position */
+struct request *dnbd_deq_request_handle(dnbd_queue_t * q, uint64_t pos)
+{
+	struct request *req = NULL;
+	struct list_head *tmp;
+		unsigned long flags;
+
+	spin_lock_irqsave(&q->lock,flags);
+	list_for_each(tmp, &q->head) {
+		req = blkdev_entry_to_request(tmp);
+		if (((u64) req->sector) << 9 == pos) {
+			list_del_init(&req->queuelist);
+			goto out;
+		}
+
+	}
+	req = NULL;
+      out:
+	spin_unlock_irqrestore(&q->lock,flags);
+	return req;
+}
+
+/* dequeue from queue */
+struct request *dnbd_deq_request(dnbd_queue_t * q)
+{
+	struct request *req = NULL;
+	unsigned long flags;
+
+	spin_lock_irqsave(&q->lock, flags);
+	if (!list_empty(&q->head)) {
+		req = blkdev_entry_to_request(q->head.prev);
+		list_del_init(&req->queuelist);
+	}
+	spin_unlock_irqrestore(&q->lock, flags);
+	return req;
+}
+
+/* sleep until request can be dequeued */
+struct request *dnbd_try_deq_request(dnbd_queue_t * q)
+{
+	struct request *req;
+
+
+	req = dnbd_deq_request(q);
+	if (!req) {
+		struct task_struct *tsk = current;
+
+		DECLARE_WAITQUEUE(wait, tsk);
+		add_wait_queue(&q->waiters, &wait);
+
+		for (;;) {
+
+			set_current_state(TASK_INTERRUPTIBLE);
+			req = dnbd_deq_request(q);
+
+			if (req || signal_pending(current))
+				break;
+
+			schedule();
+		}
+
+		set_current_state(TASK_RUNNING);
+		remove_wait_queue(&q->waiters, &wait);
+	}
+
+	return req;
+}
+
+/* requeue requests with timeout */
+int dnbd_requeue_requests(dnbd_queue_t * to, dnbd_queue_t * from,
+			  unsigned long timeout)
+{
+	struct request *req = NULL;
+	struct list_head *tmp, *keep;
+	int requeued = 0;
+	unsigned long flags;
+
+	spin_lock_irqsave(&from->lock,flags);
+
+	list_for_each_safe(tmp, keep, &from->head) {
+		req = blkdev_entry_to_request(tmp);
+		if (req->start_time < timeout) {
+			requeued++;
+			list_del_init(&req->queuelist);
+
+			spin_lock_irqsave(&to->lock,flags);
+			list_add(&req->queuelist, &to->head);
+			spin_unlock_irqrestore(&to->lock,flags);
+		}
+	}
+
+	spin_unlock_irqrestore(&from->lock,flags);
+
+	wake_up(&to->waiters);
+
+	return requeued;
+}