netdev - Re: [RFC 3/5] net/ethtool: support set coalesce per queue

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Date:	Sat, 19 Dec 2015 03:38:55 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	kan.liang@...el.com, netdev@...r.kernel.org, davem@...emloft.net,
	bwh@...nel.org
Cc:	jesse.brandeburg@...el.com, andi@...stfloor.org,
	f.fainelli@...il.com, alexander.duyck@...il.com,
	jeffrey.t.kirsher@...el.com, shannon.nelson@...el.com,
	carolyn.wyborny@...el.com, donald.c.skidmore@...el.com,
	mitch.a.williams@...el.com, ogerlitz@...lanox.com,
	edumazet@...gle.com, jiri@...lanox.com, sfeldma@...il.com,
	gospo@...ulusnetworks.com, sasha.levin@...cle.com,
	dsahern@...il.com, tj@...nel.org, cascardo@...hat.com,
	corbet@....net
Subject: Re: [RFC 3/5] net/ethtool: support set coalesce per queue

On Thu, 2015-12-17 at 06:51 +0000, kan.liang@...el.com wrote:
[...]
> --- a/net/core/ethtool.c
> +++ b/net/core/ethtool.c
> @@ -1778,6 +1778,37 @@ static int ethtool_get_per_queue_coalesce(struct net_device *dev,
>  	return 0;
>  }
>  
> +static int ethtool_set_per_queue_coalesce(struct net_device *dev,
> +					  void __user *useraddr,
> +					  struct ethtool_per_queue_op *per_queue_opt)
> +{
> +	u64 queue_mask;
> +	int bit, i, ret;
> +
> +	if (!dev->ethtool_ops->set_per_queue_coalesce)
> +		return -EOPNOTSUPP;
> +
> +	useraddr += sizeof(*per_queue_opt);
> +	for (i = 0; i < MAX_QUEUE_MASK; i++) {
> +		queue_mask = per_queue_opt->queue_mask[i];
> +		if (queue_mask > 0) {
> +			for_each_set_bit(bit, (unsigned long *)&queue_mask, 64) {
> +				struct ethtool_coalesce coalesce;
> +
> +				if (copy_from_user(&coalesce, useraddr, sizeof(coalesce)))
> +					return -EFAULT;
> +
> +				ret = dev->ethtool_ops->set_per_queue_coalesce(dev, bit + i * 64, &coalesce);
> +				if (ret != 0)
> +					return ret;
[...]

So there's no attempt to roll back on failure?

Then, what is the benefit of doing this iteration in the kernel rather
than userland?

Ben.

-- 
Ben Hutchings
Always try to do things in chronological order;
it's less confusing that way.
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