Re: [PATCH net-next V10 1/6] devlink: Extend devlink rate API with traffic classes bandwidth management

[Carolina Jubran]

On 21/05/2025 1:53, Jakub Kicinski wrote:
> A few quick comments here as the test is failing
>
> On Tue, 20 May 2025 21:38:02 +0300 Tariq Toukan wrote:
> > +      -
> > +        name: rate-tc-bws
> > +        type: nest
> > +        multi-attr: true
> > +        nested-attributes: dl-rate-tc-bws
> > +      -
> > +        name: rate-tc-index
> > +        type: u8
> > +        checks:
> > +          min: 0
> > +          max: rate-tc-index-max
>
> no need for min: 0 on an unsigned type ?

Will remove them.

> > +      -
> > +        name: rate-tc-bw
> > +        type: u32
> > +        doc: |
> > +             Specifies the bandwidth allocation for the Traffic Class as a
> > +             percentage.
> > +        checks:
> > +          min: 0
> > +          max: 100
>
> Why in percentage? I don't think any existing param in devlink rate
> or net shapers is in percentage right? Not according to what i can
> grok about the uAPI.

I thought percentage might fit better here because it lets users clearly 
set the bandwidth share for each traffic class. While this isn’t the 
same as tx_weight in devlink-rate, the idea is related since both use 
relative values. If there isn’t a strong reason against it, I’d like to 
keep using percentages here.

> > +static int devlink_nl_rate_tc_bw_parse(struct nlattr *parent_nest, u32 *tc_bw,
> > +				       unsigned long *bitmap, struct netlink_ext_ack *extack)
> > +{
> > +	struct nlattr *tb[DEVLINK_ATTR_MAX + 1];
> > +	u8 tc_index;
> > +
> > +	nla_parse_nested(tb, DEVLINK_ATTR_MAX, parent_nest, devlink_dl_rate_tc_bws_nl_policy,
>
> Let's error check this, I get that we already validated via the policy
> but what if we do memory allocations during parsing one day, or some
> other failure-prone operation.. better check the return value.

Ack. will do.
> nit: over 80 chars for no good reason, the line overflows anyway.
> Please use checkpatch --max-line-width=80 for core code,
> at the very least.

I noticed the current code already goes over 80 chars, but I’ll update 
it to follow the 80-char limit. Will fix, thanks.

> > +			 extack);
> > +	if (!tb[DEVLINK_ATTR_RATE_TC_INDEX]) {
> > +		NL_SET_ERR_ATTR_MISS(extack, parent_nest, DEVLINK_ATTR_RATE_TC_INDEX);
> > +		return -EINVAL;
> > +	}
> > +
> > +	tc_index = nla_get_u8(tb[DEVLINK_ATTR_RATE_TC_INDEX]);
> > +
> > +	if (!tb[DEVLINK_ATTR_RATE_TC_BW]) {
> > +		NL_SET_ERR_ATTR_MISS(extack, parent_nest, DEVLINK_ATTR_RATE_TC_BW);
> > +		return -EINVAL;
> > +	}
> > +
> > +	if (test_and_set_bit(tc_index, bitmap)) {
> > +		NL_SET_ERR_MSG_FMT(extack, "Duplicate traffic class index specified (%u)",
> > +				   tc_index);
> > +		return -EINVAL;
> > +	}
> > +
> > +	tc_bw[tc_index] = nla_get_u32(tb[DEVLINK_ATTR_RATE_TC_BW]);
> > +
> > +	return 0;
> > +}
> > +
> > +static int devlink_nl_rate_tc_bw_set(struct devlink_rate *devlink_rate,
> > +				     struct genl_info *info)
> > +{
> > +	DECLARE_BITMAP(bitmap, DEVLINK_RATE_TCS_MAX) = {};
> > +	struct devlink *devlink = devlink_rate->devlink;
> > +	const struct devlink_ops *ops = devlink->ops;
> > +	int rem, err = -EOPNOTSUPP, i, total = 0;
> > +	u32 tc_bw[DEVLINK_RATE_TCS_MAX] = {};
> > +	struct nlattr *attr;
> > +
> > +	nla_for_each_attr(attr, genlmsg_data(info->genlhdr),
> > +			  genlmsg_len(info->genlhdr), rem) {
>
>   nla_for_each_attr_type() ?
>   or better still add a _type() version of nlmsg_for_each_attr() ?
Good point, thanks. I’ll add a _type() version for nlmsg_for_each_attr. 
Do you prefer this to be part of this patch or should I send it as a 
separate patch?

> > +		if (nla_type(attr) == DEVLINK_ATTR_RATE_TC_BWS) {
> > +			err = devlink_nl_rate_tc_bw_parse(attr, tc_bw, bitmap, info->extack);
> > +			if (err)
> > +				return err;
> > +		}
> > +	}