[NET]: Rate limiting for socket allocation failure messages.

This patch limits the warning messages when socket allocation failures
happen. It happens under memory pressure.
Signed-off-by: NAkinobu Mita <mita@miraclelinux.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/socket.c

@@ -1178,6 +1178,7 @@ static int __sock_create(int family, int type, int protocol, struct socket **res
  */
 
 	if (!(sock = sock_alloc())) {
+		if (net_ratelimit())
 			printk(KERN_WARNING "socket: no more sockets\n");
 		err = -ENFILE;		/* Not exactly a match, but its the
 					   closest posix thing */