Re: [PATCH net-next v11 10/21] net: add helpers for setting a memory provider on an rx queue

[Jakub Kicinski <kuba@kernel.org>]

On Thu, 16 Jan 2025 15:16:52 -0800 David Wei wrote:
> +static void __net_mp_close_rxq(struct net_device *dev, unsigned ifq_idx,
> +			      struct pp_memory_provider_params *old_p)
> +{
> +	struct netdev_rx_queue *rxq;
> +	int ret;
> +
> +	if (WARN_ON_ONCE(ifq_idx >= dev->real_num_rx_queues))
> +		return;
> + 
> +	rxq = __netif_get_rx_queue(dev, ifq_idx);

I think there's a small race between io_uring closing and the netdev
unregister. We can try to uninstall twice, let's put

	/* Callers holding a netdev ref may get here after we already
	 * went thru shutdown via dev_memory_provider_uninstall().
	 */
	if (dev->reg_state > NETREG_REGISTERED &&
	    !rxq->mp_params.mp_ops)
		return;

here, and in dev_memory_provider_uninstall() clear the pointers?

> +	if (WARN_ON_ONCE(rxq->mp_params.mp_ops != old_p->mp_ops ||
> +			 rxq->mp_params.mp_priv != old_p->mp_priv))
> +		return;
> +
> +	rxq->mp_params.mp_ops = NULL;
> +	rxq->mp_params.mp_priv = NULL;
> +	ret = netdev_rx_queue_restart(dev, ifq_idx);
> +	if (ret)
> +		pr_devel("Could not restart queue %u after removing memory provider.\n",
> +			 ifq_idx);
> +}