Re: [PATCH V2 1/6] namespaces: assign each namespace instance a serial number

[Eric Paris <eparis-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

On Fri, 2014-05-09 at 20:27 -0400, Richard Guy Briggs wrote:
> Generate and assign a serial number per namespace instance since boot.
> 
> Use a serial number per namespace (unique across one boot of one kernel)
> instead of the inode number (which is claimed to have had the right to change
> reserved and is not necessarily unique if there is more than one proc fs) to
> uniquely identify it per kernel boot.
> 
> Signed-off-by: Richard Guy Briggs <rgb-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> ---

> +/**
> + * ns_serial - compute a serial number for the namespace
> + *
> + * Compute a serial number for the namespace to uniquely identify it in
> + * audit records.
> + */
> +unsigned long long ns_serial(void)
> +{
> +	static DEFINE_SPINLOCK(serial_lock);
> +	static unsigned long long serial = 4; /* reserved for IPC, UTS, user, PID */
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&serial_lock, flags);
> +	++serial;
> +	spin_unlock_irqrestore(&serial_lock, flags);
> +	BUG_ON(!serial);
> +
> +	return serial;
> +}
> +
>  static inline struct nsproxy *create_nsproxy(void)
>  {
>  	struct nsproxy *nsproxy;

atomic64_t instead of doing it yourself?

and why _irqsave() ?  Can we seriously create new namespaces in irq
context?  If you use the atomic though, you don't have to worry about
it...