vmbus: split ring buffer allocation from open

The UIO driver needs the ring buffer to be persistent(reused)
across open/close. Split the allocation and setup of ring buffer
out of vmbus_open. For normal usage vmbus_open/vmbus_close there
are no changes; only impacts uio_hv_generic which needs to keep
ring buffer memory and reuse when application restarts.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/hyperv.h

diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index a6c32d2..b3e2436 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -741,6 +741,7 @@ struct vmbus_channel {
 	/* Allocated memory for ring buffer */
 	struct page *ringbuffer_page;
 	u32 ringbuffer_pagecount;
+	u32 ringbuffer_send_offset;
 	struct hv_ring_buffer_info outbound;	/* send to parent */
 	struct hv_ring_buffer_info inbound;	/* receive from parent */
 
@@ -1021,6 +1022,14 @@ struct vmbus_packet_mpb_array {
 	struct hv_mpb_array range;
 } __packed;
 
+int vmbus_alloc_ring(struct vmbus_channel *channel,
+		     u32 send_size, u32 recv_size);
+void vmbus_free_ring(struct vmbus_channel *channel);
+
+int vmbus_connect_ring(struct vmbus_channel *channel,
+		       void (*onchannel_callback)(void *context),
+		       void *context);
+int vmbus_disconnect_ring(struct vmbus_channel *channel);
 
 extern int vmbus_open(struct vmbus_channel *channel,
 			    u32 send_ringbuffersize,