optimize compat_core_sys_select() by a using stack space for small fd sets

	compat_ulong_t __user *outp, compat_ulong_t __user *exp, s64 *timeout)

{

	fd_set_bits fds;

	char *bits;

	void *bits;

	int size, max_fds, ret = -EINVAL;

	struct fdtable *fdt;

	long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];

	if (n < 0)

		goto out_nofds;

	 * since we used fdset we need to allocate memory in units of

	 * long-words.

	 */

	ret = -ENOMEM;

	size = FDS_BYTES(n);

	bits = stack_fds;

	if (size > sizeof(stack_fds) / 6) {

		bits = kmalloc(6 * size, GFP_KERNEL);

		ret = -ENOMEM;

		if (!bits)

			goto out_nofds;

	}

	fds.in      = (unsigned long *)  bits;

	fds.out     = (unsigned long *) (bits +   size);

	fds.ex      = (unsigned long *) (bits + 2*size);

	    compat_set_fd_set(n, exp, fds.res_ex))

		ret = -EFAULT;

out:

	if (bits != stack_fds)

		kfree(bits);

out_nofds:

	return ret;