netdev - Re: [PATCH V4 5/8] net/ethtool: support set coalesce per queue

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Date:	Sun, 14 Feb 2016 18:55:05 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Kan Liang <kan.liang@...el.com>, netdev@...r.kernel.org,
	davem@...emloft.net, bwh@...nel.org
Cc:	andi@...stfloor.org, jesse.brandeburg@...el.com,
	shannon.nelson@...el.com, f.fainelli@...il.com,
	alexander.duyck@...il.com, jeffrey.t.kirsher@...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, decot@...glers.com
Subject: Re: [PATCH V4 5/8] net/ethtool: support set coalesce per queue

On Mon, 2016-02-08 at 02:45 -0500, Kan Liang wrote:
> From: Kan Liang <kan.liang@...el.com>
> 
> This patch implements sub command ETHTOOL_SCOALESCE for ioctl
> ETHTOOL_PERQUEUE. It introduces an interface set_per_queue_coalesce to
> set coalesce of each masked queue to device driver. The wanted coalesce
> information are stored in "data" for each masked queue, which can copy
> from userspace.
> If it fails to set coalesce to device driver, the value which already
> set to specific queue will be tried to rollback.
> 
> Signed-off-by: Kan Liang <kan.liang@...el.com>
> ---
>  include/linux/ethtool.h |  8 +++++++
>  net/core/ethtool.c      | 60 +++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 68 insertions(+)
> 
> diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
> index a83566f..0c699b8 100644
> --- a/include/linux/ethtool.h
> +++ b/include/linux/ethtool.h
> @@ -208,6 +208,12 @@ static inline u32 ethtool_rxfh_indir_default(u32 index, u32 n_rx_rings)
>   *	zero should return. But related unavailable fields should be set to ~0,
>   *	which indicates RX or TX is not in the range.
>   *	Returns a negative error code or zero.
> + * @set_per_queue_coalesce: Set interrupt coalescing parameters per queue.
> + *	It needs to do range check for the input queue number. Only if
> + *	neither RX nor TX queue number is in the range, a negative error code
> + *	returns. For the case that only RX or only TX is not in the range,
> + *	zero should return. The related unavailable fields should be avoid.
> + *	Returns a negative error code or zero.

This is poorly worded.  I suggest:

"It must check that the given queue number is valid. If neither a RX
nor a TX queue has this number, return -EINVAL. If only a RX queue or a
TX queue has this number, ignore the inapplicable fields."

>   *
>   * All operations are optional (i.e. the function pointer may be set
>   * to %NULL) and callers must take this into account.  Callers must
> @@ -288,6 +294,8 @@ struct ethtool_ops {
>  			       const struct ethtool_tunable *, const void *);
>  	int	(*get_per_queue_coalesce)(struct net_device *, int,
>  					  struct ethtool_coalesce *);
> +	int	(*set_per_queue_coalesce)(struct net_device *, int,
> +					  struct ethtool_coalesce *);

Again, please use unsigned int for the queue number.

[...]
> diff --git a/net/core/ethtool.c b/net/core/ethtool.c
> index ccefbf5..933de09 100644
> --- a/net/core/ethtool.c
> +++ b/net/core/ethtool.c
> @@ -1854,6 +1854,64 @@ 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)
> +{
> +	int bit, i, ret = 0;
> +	int queue_num;

It would be clearer to call this n_queues ('number of queues') rather
than queue_num.

> +	struct ethtool_coalesce *backup = NULL, *tmp = NULL;
> +	DECLARE_BITMAP(queue_mask, MAX_NUM_QUEUE);
> +
> +	if ((!dev->ethtool_ops->set_per_queue_coalesce) ||
> +	    (!dev->ethtool_ops->get_per_queue_coalesce))
> +		return -EOPNOTSUPP;
> +
> +	useraddr += sizeof(*per_queue_opt);
> +
> +	bitmap_from_u32array(queue_mask,
> +			     MAX_NUM_QUEUE,
> +			     per_queue_opt->queue_mask,
> +			     DIV_ROUND_UP(MAX_NUM_QUEUE, 32));
> +	queue_num = bitmap_weight(queue_mask, MAX_NUM_QUEUE);
> +	tmp = backup = kmalloc_array(queue_num, sizeof(*backup), GFP_KERNEL);
> +	if (!backup)
> +		return -ENOMEM;
> +
> +	for_each_set_bit(bit, queue_mask, MAX_NUM_QUEUE) {
> +		struct ethtool_coalesce coalesce;
> +
> +		ret = dev->ethtool_ops->get_per_queue_coalesce(dev, bit, tmp);
> +		if (ret != 0)
> +			goto roll_back;
> +
> +		tmp += sizeof(struct ethtool_coalesce);

No!  tmp is a pointer to struct ethtool_coalesce, so it must be
incremented by 1.

> +		if (copy_from_user(&coalesce, useraddr, sizeof(coalesce))) {
> +			ret = -EFAULT;
> +			goto roll_back;
> +		}
> +
> +		ret = dev->ethtool_ops->set_per_queue_coalesce(dev, bit, &coalesce);
> +		if (ret != 0)
> +			goto roll_back;
> +
> +		useraddr += sizeof(coalesce);
> +	}
> +
> +roll_back:
> +	if (ret != 0) {
> +		tmp = backup;
> +		for_each_set_bit(i, queue_mask, bit) {
> +			dev->ethtool_ops->set_per_queue_coalesce(dev, i, tmp);
> +			tmp += sizeof(struct ethtool_coalesce);
[...]

Again, increment by 1.

Ben.

-- 
Ben Hutchings
Sturgeon's Law: Ninety percent of everything is crap.
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