1 files changed, 102 insertions, 0 deletions
diff --git a/kernel/core.h b/kernel/core.h
new file mode 100644
index 0000000..3c75ade
--- /dev/null
+++ b/kernel/core.h
@@ -0,0 +1,102 @@
+/*
+ * kernel/core.h
+ */
+
+
+/* interval to send heartbeats */
+#define HB_NORMAL_INTERVAL 30*HZ
+
+/* interval to send heartbeats in emergency-mode */
+#define HB_EMERG_INTERVAL  5*HZ
+
+/* interval to check the pending-queue */
+#define REQUEUE_INTERVAL HZ/20
+
+/* interval to look for faster servers */
+#define TO_INTERVAL HZ
+
+/* dnbd0, dnbd1, etc */
+#define DNBD2_DEVICES 3
+
+
+/* Given to us by the kernel at load-time. */
+extern int dnbd2_major;
+
+
+/*
+ * Called by the block layer to make the driver process some
+ * requests. For each request it does the following:
+ * 1. Prepares the request by attaching information to it.
+ * 2. Enqueues the request into the send-queue.
+ * 3. Wakes up dnbd2_tx_loop.
+ */
+void dnbd2_request(request_queue_t *q);
+
+/*
+ * This thread sleeps until there are requests in the send-queue.
+ * Each request is dequeued from the send-queue, enqueued into the
+ * pending-queue and finally given to dnbd2_send_request.
+ */
+int dnbd2_tx_loop(void *data);
+
+/*
+ * Send a request and update the request's and the destination
+ * server's counters.
+ */
+void dnbd2_send_request(struct request *req, dnbd2_device_t *dev);
+
+/*
+ * This thread sleeps until a reply arrives and then processes it.
+ */
+int dnbd2_rx_loop(void *data);
+
+/*
+ * When a reply arrives through the network it is caught by
+ * dnbd2_rx_loop, which calls this function to find a matching request
+ * in the pending queue.
+ */
+struct request *dnbd2_find_request(uint64_t num, uint16_t cmd,
+				   struct srv_info *dst);
+
+/*
+ * The driver calls this function when it is done processing a request
+ * and has no further use for it. Resources are freed and the block
+ * layer informed if necessary.
+ */
+void dnbd2_end_request(struct request *req, int success);
+
+/*
+ * If a request remains too long unanswered, it is moved by this
+ * function from the pending-queue into the send-queue. This function
+ * is fired regularly by a timer.
+ */
+void dnbd2_requeue_timer(unsigned long arg);
+
+/*
+ * Periodically enqueu, for each server, a heartbeat request
+ * (CMD_GET_SERVERS) into the send-queue.
+ */
+void dnbd2_hb_timer(unsigned long arg);
+
+/*
+ * Check every TO_INTERVAL jiffies if there is a faster server and
+ * switch to it.  TO stands for "takeover".
+ */
+void dnbd2_to_timer(unsigned long arg);
+
+/*
+ * If the driver looses contact to all servers it starts the emergency
+ * mode: First dnbd2_requeue_timer and dnbd2_to_timer are stopped.
+ * Then the emergency list (the last list of servers acquired with
+ * CMD_GET_SERVERS) is activated and the rate of heartbeats increased
+ * to HB_EMERG_INTERVAL.
+ */
+void start_emergency(dnbd2_device_t *dev);
+
+/*
+ * This function is called if a server answers to a heartbeat during
+ * emergency mode.  This server (@srv_info) is made the active server,
+ * dnbd2_requeue_timer and dnbd2_to_timer started and the rate of
+ * heartbeats decreased to HB_NORMAL_INTERVAL.
+ */
+void stop_emergency(struct srv_info *srv_info);