make sock_alloc_file() do sock_release() on failures

This changes calling conventions (and simplifies the hell out
the callers).  New rules: once struct socket had been passed
to sock_alloc_file(), it's been consumed either by struct file
or by sock_release() done by sock_alloc_file().  Either way
the caller should not do sock_release() after that point.

Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/9p/trans_fd.c

@@ -839,7 +839,6 @@ static int p9_socket_open(struct p9_client *client, struct socket *csocket)
 	if (IS_ERR(file)) {
 		pr_err("%s (%d): failed to map fd\n",
 		       __func__, task_pid_nr(current));
-		sock_release(csocket);
 		kfree(p);
 		return PTR_ERR(file);
 	}