drbd: Preallocate one page per drbd_socket as a receive buffer

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 74637cc..932ba03 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -554,6 +554,8 @@
 #error "PAGE_SIZE too small"
 #endif
 
+#define DRBD_SOCKET_BUFFER_SIZE 4096
+
 union p_polymorph {
         struct p_header           header;
         struct p_handshake       handshake;
@@ -803,7 +805,7 @@
 	/* this way we get our
 	 * send/receive buffers off the stack */
 	union p_polymorph sbuf;
-	union p_polymorph rbuf;
+	void *rbuf;
 };
 
 struct drbd_md {