linux-kernel - Re: [PATCH RFC V1 net-next 1/4] net: ethtool: Refactor identical get_ts

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Message-ID: <20220120161329.fbniou5kzn2x4rp7@skbuf>
Date:   Thu, 20 Jan 2022 16:13:29 +0000
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Richard Cochran <richardcochran@...il.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Lunn <andrew@...n.ch>,
        David Miller <davem@...emloft.net>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Jakub Kicinski <kuba@...nel.org>,
        Joakim Zhang <qiangqing.zhang@....com>,
        Kurt Kanzenbach <kurt@...utronix.de>,
        Miroslav Lichvar <mlichvar@...hat.com>,
        Russell King <linux@....linux.org.uk>,
        Hangbin Liu <liuhangbin@...il.com>
Subject: Re: [PATCH RFC V1 net-next 1/4] net: ethtool: Refactor identical
 get_ts_info implementations.

On Mon, Jan 03, 2022 at 03:25:52PM -0800, Richard Cochran wrote:
> Both the vlan and the bonding drivers call their "real" device driver
> in order to report the time stamping capabilities.  Provide a core
> ethtool helper function to avoid copy/paste in the stack.
> 
> Signed-off-by: Richard Cochran <richardcochran@...il.com>
> ---

Reviewed-by: Vladimir Oltean <vladimir.oltean@....com>

>  drivers/net/bonding/bond_main.c | 14 ++------------
>  include/linux/ethtool.h         |  8 ++++++++
>  net/8021q/vlan_dev.c            | 15 +--------------
>  net/ethtool/common.c            |  6 ++++++
>  4 files changed, 17 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index b60e22f6394a..f28b88b67b9e 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -5353,23 +5353,13 @@ static int bond_ethtool_get_ts_info(struct net_device *bond_dev,
>  				    struct ethtool_ts_info *info)
>  {
>  	struct bonding *bond = netdev_priv(bond_dev);
> -	const struct ethtool_ops *ops;
>  	struct net_device *real_dev;
> -	struct phy_device *phydev;
>  
>  	rcu_read_lock();
>  	real_dev = bond_option_active_slave_get_rcu(bond);
>  	rcu_read_unlock();

Side note: I'm a bit confused about this rcu_read_lock() ->
rcu_dereference_protected() -> rcu_read_unlock() pattern, and use of the
real_dev outside the RCU critical section. Isn't ->get_ts_info()
protected by the rtnl_mutex? Shouldn't there be a
bond_option_active_slave_get() which uses rtnl_dereference()?
I see the code has been recently added by Hangbin Liu.

> -	if (real_dev) {
> -		ops = real_dev->ethtool_ops;
> -		phydev = real_dev->phydev;
> -
> -		if (phy_has_tsinfo(phydev)) {
> -			return phy_ts_info(phydev, info);
> -		} else if (ops->get_ts_info) {
> -			return ops->get_ts_info(real_dev, info);
> -		}
> -	}
> +	if (real_dev)
> +		return ethtool_get_ts_info_by_layer(real_dev, info);
>  
>  	info->so_timestamping = SOF_TIMESTAMPING_RX_SOFTWARE |
>  				SOF_TIMESTAMPING_SOFTWARE;
> diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
> index a26f37a27167..1d72344493bb 100644
> --- a/include/linux/ethtool.h
> +++ b/include/linux/ethtool.h
> @@ -824,6 +824,14 @@ ethtool_params_from_link_mode(struct ethtool_link_ksettings *link_ksettings,
>   */
>  int ethtool_get_phc_vclocks(struct net_device *dev, int **vclock_index);
>  
> +/**
> + * ethtool_get_ts_info_by_layer - Obtains time stamping capabilities from the MAC or PHY layer.
> + * @dev: pointer to net_device structure
> + * @info: buffer to hold the result
> + * Returns zero on sauces, non-zero otherwise.
> + */
> +int ethtool_get_ts_info_by_layer(struct net_device *dev, struct ethtool_ts_info *info);
> +
>  /**
>   * ethtool_sprintf - Write formatted string to ethtool string data
>   * @data: Pointer to start of string to update
> diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
> index 26d031a43cc1..c645d7c46d78 100644
> --- a/net/8021q/vlan_dev.c
> +++ b/net/8021q/vlan_dev.c
> @@ -679,20 +679,7 @@ static int vlan_ethtool_get_ts_info(struct net_device *dev,
>  				    struct ethtool_ts_info *info)
>  {
>  	const struct vlan_dev_priv *vlan = vlan_dev_priv(dev);
> -	const struct ethtool_ops *ops = vlan->real_dev->ethtool_ops;
> -	struct phy_device *phydev = vlan->real_dev->phydev;
> -
> -	if (phy_has_tsinfo(phydev)) {
> -		return phy_ts_info(phydev, info);
> -	} else if (ops->get_ts_info) {
> -		return ops->get_ts_info(vlan->real_dev, info);
> -	} else {
> -		info->so_timestamping = SOF_TIMESTAMPING_RX_SOFTWARE |
> -			SOF_TIMESTAMPING_SOFTWARE;
> -		info->phc_index = -1;
> -	}
> -
> -	return 0;
> +	return ethtool_get_ts_info_by_layer(vlan->real_dev, info);
>  }
>  
>  static void vlan_dev_get_stats64(struct net_device *dev,
> diff --git a/net/ethtool/common.c b/net/ethtool/common.c
> index 0c5210015911..651d18eef589 100644
> --- a/net/ethtool/common.c
> +++ b/net/ethtool/common.c
> @@ -569,6 +569,12 @@ int ethtool_get_phc_vclocks(struct net_device *dev, int **vclock_index)
>  }
>  EXPORT_SYMBOL(ethtool_get_phc_vclocks);
>  
> +int ethtool_get_ts_info_by_layer(struct net_device *dev, struct ethtool_ts_info *info)
> +{
> +	return __ethtool_get_ts_info(dev, info);
> +}
> +EXPORT_SYMBOL(ethtool_get_ts_info_by_layer);

I would probably replace all __ethtool_get_ts_info() function name
occurrences with ethtool_get_ts_info_by_layer() (since it isn't a bad
name) to make it absolutely clear that it's recursive for VLAN and bond
interfaces. But maybe that's just me.

> +
>  const struct ethtool_phy_ops *ethtool_phy_ops;
>  
>  void ethtool_set_ethtool_phy_ops(const struct ethtool_phy_ops *ops)
> -- 
> 2.20.1
>