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

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Message-ID: <20250520155301.5217dd81@kernel.org>
Date: Tue, 20 May 2025 15:53:01 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Tariq Toukan <tariqt@...dia.com>
Cc: "David S. Miller" <davem@...emloft.net>, Paolo Abeni
 <pabeni@...hat.com>, Eric Dumazet <edumazet@...gle.com>, "Andrew Lunn"
 <andrew+netdev@...n.ch>, Jiri Pirko <jiri@...dia.com>, Gal Pressman
 <gal@...dia.com>, "Leon Romanovsky" <leonro@...dia.com>, Donald Hunter
 <donald.hunter@...il.com>, "Jiri Pirko" <jiri@...nulli.us>, Jonathan Corbet
 <corbet@....net>, Saeed Mahameed <saeedm@...dia.com>, Leon Romanovsky
 <leon@...nel.org>, Shuah Khan <shuah@...nel.org>, <netdev@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>, <linux-doc@...r.kernel.org>,
 <linux-rdma@...r.kernel.org>, <linux-kselftest@...r.kernel.org>, "Moshe
 Shemesh" <moshe@...dia.com>, Mark Bloch <mbloch@...dia.com>, Carolina
 Jubran <cjubran@...dia.com>, Cosmin Ratiu <cratiu@...dia.com>
Subject: Re: [PATCH net-next V10 1/6] devlink: Extend devlink rate API with
 traffic classes bandwidth management

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 ?

> +      -
> +        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.

> +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.

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.

> +			 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() ?

> +		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;
> +		}
> +	}