[NET]: Add the helper kernel_sock_shutdown()

...and fix a couple of bugs in the NBD, CIFS and OCFS2 socket handlers.

Looking at the sock->op->shutdown() handlers, it looks as if all of them
take a SHUT_RD/SHUT_WR/SHUT_RDWR argument instead of the
RCV_SHUTDOWN/SEND_SHUTDOWN arguments.
Add a helper, and then define the SHUT_* enum to ensure that kernel users
of shutdown() don't get confused.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Mark Fasheh <mark.fasheh@oracle.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/rxrpc/ar-local.c b/net/rxrpc/ar-local.c
index fe03f71..f3a2bd7 100644
--- a/net/rxrpc/ar-local.c
+++ b/net/rxrpc/ar-local.c
@@ -114,7 +114,7 @@
 	return 0;
 
 error:
-	local->socket->ops->shutdown(local->socket, 2);
+	kernel_sock_shutdown(local->socket, SHUT_RDWR);
 	local->socket->sk->sk_user_data = NULL;
 	sock_release(local->socket);
 	local->socket = NULL;
@@ -267,7 +267,7 @@
 	/* finish cleaning up the local descriptor */
 	rxrpc_purge_queue(&local->accept_queue);
 	rxrpc_purge_queue(&local->reject_queue);
-	local->socket->ops->shutdown(local->socket, 2);
+	kernel_sock_shutdown(local->socket, SHUT_RDWR);
 	sock_release(local->socket);
 
 	up_read(&rxrpc_local_sem);