[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>

include/linux/net.h

@@ -95,6 +95,12 @@ enum sock_type {
 
 #endif /* ARCH_HAS_SOCKET_TYPES */
 
+enum sock_shutdown_cmd {
+	SHUT_RD		= 0,
+	SHUT_WR		= 1,
+	SHUT_RDWR	= 2,
+};
+
 /**
  *  struct socket - general BSD socket
  *  @state: socket state (%SS_CONNECTED, etc)
@@ -223,6 +229,8 @@ extern int kernel_setsockopt(struct socket *sock, int level, int optname,
 extern int kernel_sendpage(struct socket *sock, struct page *page, int offset,
 			   size_t size, int flags);
 extern int kernel_sock_ioctl(struct socket *sock, int cmd, unsigned long arg);
+extern int kernel_sock_shutdown(struct socket *sock,
+				enum sock_shutdown_cmd how);
 
 #ifndef CONFIG_SMP
 #define SOCKOPS_WRAPPED(name) name