Re: [PATCH 1/2] namespaces: give each namespace a serial number

["Serge E. Hallyn" <serge@hallyn.com>]

Quoting Richard Guy Briggs (rgb@redhat.com):

Most of this looks reasonable, but I'm curious about something,

> +/**
> + * ns_serial - compute a serial number for the namespace
> + *
> + * Compute a serial number for the namespace to uniquely identify it in
> + * audit records.
> + */
> +unsigned int ns_serial(void)
> +{
> +	static DEFINE_SPINLOCK(serial_lock);
> +	static unsigned int serial = 4; /* reserved for IPC, UTS, user, PID */
> +
> +	unsigned long flags;
> +	unsigned int ret;
> +
> +	spin_lock_irqsave(&serial_lock, flags);
> +	do {
> +		ret = ++serial;
> +	} while (unlikely(!ret));

Why exactly are you doing this?  Surely if serial is going to
wrap around we've got a bigger problem than just wanting go
bump one more time?

> +	spin_unlock_irqrestore(&serial_lock, flags);
> +
> +	return ret;
> +}