[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/socket.c b/net/socket.c
index 5d879fd..74784df 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -2319,6 +2319,11 @@
 	return err;
 }
 
+int kernel_sock_shutdown(struct socket *sock, enum sock_shutdown_cmd how)
+{
+	return sock->ops->shutdown(sock, how);
+}
+
 /* ABI emulation layers need these two */
 EXPORT_SYMBOL(move_addr_to_kernel);
 EXPORT_SYMBOL(move_addr_to_user);
@@ -2345,3 +2350,4 @@
 EXPORT_SYMBOL(kernel_setsockopt);
 EXPORT_SYMBOL(kernel_sendpage);
 EXPORT_SYMBOL(kernel_sock_ioctl);
+EXPORT_SYMBOL(kernel_sock_shutdown);