netdev - Re: [PATCH net-next v7 05/16] net: Proxy net_mp_{open,close}

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Message-ID: <20260120180402.2b9ab13a@kernel.org>
Date: Tue, 20 Jan 2026 18:04:02 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Daniel Borkmann <daniel@...earbox.net>
Cc: netdev@...r.kernel.org, bpf@...r.kernel.org, davem@...emloft.net,
 razor@...ckwall.org, pabeni@...hat.com, willemb@...gle.com,
 sdf@...ichev.me, john.fastabend@...il.com, martin.lau@...nel.org,
 jordan@...fe.io, maciej.fijalkowski@...el.com, magnus.karlsson@...el.com,
 dw@...idwei.uk, toke@...hat.com, yangzhenze@...edance.com,
 wangdongdong.6@...edance.com
Subject: Re: [PATCH net-next v7 05/16] net: Proxy net_mp_{open,close}_rxq
 for leased queues

On Thu, 15 Jan 2026 09:25:52 +0100 Daniel Borkmann wrote:
>  	if (!netdev_need_ops_lock(dev))
>  		return -EOPNOTSUPP;
> -
>  	if (rxq_idx >= dev->real_num_rx_queues) {
>  		NL_SET_ERR_MSG(extack, "rx queue index out of range");
>  		return -ERANGE;
>  	}
> -	rxq_idx = array_index_nospec(rxq_idx, dev->real_num_rx_queues);
>  
> +	rxq_idx = array_index_nospec(rxq_idx, dev->real_num_rx_queues);

The white space changes here look haphazard.

> +	rxq = netif_get_rx_queue_lease_locked(&dev, &rxq_idx);

I really hate this function but I don't have any great suggestion on
how to make it better. I'd prefer if there was a clear separation
between the case where we call directly, vs where swapped the queue.
Instead of replacing pointers passed in by reference :| And that'd 
remove the conditional locking too.

> +	if (!rxq) {
> +		NL_SET_ERR_MSG(extack, "rx queue peered to a virtual netdev");

The fact the !rxq means the queue was leased is also fairly random
vs all the subsequent checks.

> +		return -EBUSY;
> +	}
> +	if (!dev->dev.parent) {
> +		NL_SET_ERR_MSG(extack, "rx queue is mapped to a virtual netdev");

mapped? Or belongs?

> +		ret = -EBUSY;
> +		goto out;
> +	}
>  	if (dev->cfg->hds_config != ETHTOOL_TCP_DATA_SPLIT_ENABLED) {
>  		NL_SET_ERR_MSG(extack, "tcp-data-split is disabled");
> -		return -EINVAL;
> +		ret = -EINVAL;
> +		goto out;
>  	}
>  	if (dev->cfg->hds_thresh) {
>  		NL_SET_ERR_MSG(extack, "hds-thresh is not zero");
> -		return -EINVAL;
> +		ret = -EINVAL;
> +		goto out;
>  	}
>  	if (dev_xdp_prog_count(dev)) {
>  		NL_SET_ERR_MSG(extack, "unable to custom memory provider to device with XDP program attached");
> -		return -EEXIST;
> +		ret = -EEXIST;
> +		goto out;
>  	}
> -
> -	rxq = __netif_get_rx_queue(dev, rxq_idx);
>  	if (rxq->mp_params.mp_ops) {
>  		NL_SET_ERR_MSG(extack, "designated queue already memory provider bound");
> -		return -EEXIST;
> +		ret = -EEXIST;
> +		goto out;
>  	}
>  #ifdef CONFIG_XDP_SOCKETS
>  	if (rxq->pool) {
>  		NL_SET_ERR_MSG(extack, "designated queue already in use by AF_XDP");
> -		return -EBUSY;
> +		ret = -EBUSY;
> +		goto out;

All these checks can be factored out to avoid making this function long
and having 5 gotos.

>  	}
>  #endif
> -

Please lease my whitespace be.

>  	rxq->mp_params = *p;
>  	ret = netdev_rx_queue_restart(dev, rxq_idx);
>  	if (ret) {
>  		rxq->mp_params.mp_ops = NULL;
>  		rxq->mp_params.mp_priv = NULL;
>  	}