linux-kernel - Re: [PATCH net-next 1/7] net: ethtool: netlink: Allow per-netdevice DUMP operations

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Message-ID: <20250307151409.GJ3666230@kernel.org>
Date: Fri, 7 Mar 2025 15:14:09 +0000
From: Simon Horman <horms@...nel.org>
To: Maxime Chevallier <maxime.chevallier@...tlin.com>
Cc: davem@...emloft.net, Andrew Lunn <andrew@...n.ch>,
	Jakub Kicinski <kuba@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
	Heiner Kallweit <hkallweit1@...il.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, thomas.petazzoni@...tlin.com,
	linux-arm-kernel@...ts.infradead.org,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Herve Codina <herve.codina@...tlin.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	Russell King <linux@...linux.org.uk>,
	Vladimir Oltean <vladimir.oltean@....com>,
	Köry Maincent <kory.maincent@...tlin.com>,
	Oleksij Rempel <o.rempel@...gutronix.de>,
	Romain Gantois <romain.gantois@...tlin.com>,
	Piergiorgio Beruto <piergiorgio.beruto@...il.com>
Subject: Re: [PATCH net-next 1/7] net: ethtool: netlink: Allow per-netdevice
 DUMP operations

On Fri, Mar 07, 2025 at 02:18:19PM +0100, Maxime Chevallier wrote:
> Hi Simon,
> 
> On Fri, 7 Mar 2025 12:21:19 +0000
> Simon Horman <horms@...nel.org> wrote:
> 
> > On Wed, Mar 05, 2025 at 03:19:31PM +0100, Maxime Chevallier wrote:
> > > We have a number of netlink commands in the ethnl family that may have
> > > multiple objects to dump even for a single net_device, including :
> > > 
> > >  - PLCA, PSE-PD, phy: one message per PHY device
> > >  - tsinfo: one message per timestamp source (netdev + phys)
> > >  - rss: One per RSS context
> > > 
> > > To get this behaviour, these netlink commands need to roll a custom  
> > > ->dumpit().  
> > > 
> > > To prepare making per-netdev DUMP more generic in ethnl, introduce a
> > > member in the ethnl ops to indicate if a given command may allow
> > > pernetdev DUMPs (also referred to as filtered DUMPs).
> > > 
> > > Signed-off-by: Maxime Chevallier <maxime.chevallier@...tlin.com>
> > > ---
> > >  net/ethtool/netlink.c | 45 ++++++++++++++++++++++++++++---------------
> > >  net/ethtool/netlink.h |  1 +
> > >  2 files changed, 30 insertions(+), 16 deletions(-)
> > > 
> > > diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
> > > index 734849a57369..0815b28ba32f 100644
> > > --- a/net/ethtool/netlink.c
> > > +++ b/net/ethtool/netlink.c
> > > @@ -578,21 +578,34 @@ static int ethnl_default_dumpit(struct sk_buff *skb,
> > >  	int ret = 0;
> > >  
> > >  	rcu_read_lock();
> > > -	for_each_netdev_dump(net, dev, ctx->pos_ifindex) {
> > > -		dev_hold(dev);
> > > +	if (ctx->req_info->dev) {
> > > +		dev = ctx->req_info->dev;
> > >  		rcu_read_unlock();
> > > -
> > > -		ret = ethnl_default_dump_one(skb, dev, ctx, genl_info_dump(cb));
> > > -
> > > +		/* Filtered DUMP request targeted to a single netdev. We already
> > > +		 * hold a ref to the netdev from ->start()
> > > +		 */
> > > +		ret = ethnl_default_dump_one_dev(skb, dev, ctx,
> > > +						 genl_info_dump(cb));  
> > 
> > Hi Maxime,
> > 
> > ethnl_default_dump_one_dev() is called here but it doesn't exist
> > until the following patch is applied, which breaks bisection.
> 
> Yeah I messed-up in my rebase and bisection broke :(
> 
> I'll send a new version in a few days, as Jakub said, let's give some
> time for the netdev_lock series to move forward and go through CI, I'll
> need to rebase on it at some point.

Thanks. Apologies for duplicating Jakub's comments to some extent.
I only saw them after I'd sent my previous email to you.

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