netdev - Re: [PATCH v2 net 2/9] net: enetc: correct the tx

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Message-ID: <20250221091835.g6ybtng4wiltg4ii@skbuf>
Date: Fri, 21 Feb 2025 11:18:35 +0200
From: Vladimir Oltean <vladimir.oltean@....com>
To: Wei Fang <wei.fang@....com>
Cc: Claudiu Manoil <claudiu.manoil@....com>,
	Clark Wang <xiaoning.wang@....com>,
	"andrew+netdev@...n.ch" <andrew+netdev@...n.ch>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"edumazet@...gle.com" <edumazet@...gle.com>,
	"kuba@...nel.org" <kuba@...nel.org>,
	"pabeni@...hat.com" <pabeni@...hat.com>,
	Ioana Ciornei <ioana.ciornei@....com>,
	"Y.B. Lu" <yangbo.lu@....com>,
	"michal.swiatkowski@...ux.intel.com" <michal.swiatkowski@...ux.intel.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"imx@...ts.linux.dev" <imx@...ts.linux.dev>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH v2 net 2/9] net: enetc: correct the tx_swbd statistics

On Fri, Feb 21, 2025 at 03:42:05AM +0200, Wei Fang wrote:
> > I'm not sure "correct the statistics" is the best way to describe this
> > change. Maybe "keep track of correct TXBD count in
> > enetc_map_tx_tso_buffs()"?
> 
> Hi Vladimir,
> 
> Inspired by Michal, I think we don't need to keep the count variable, because
> we already have index "i", we just need to record the value of the initial i at the
> beginning. So I plan to do this optimization on the net-next tree in the future.
> So I don't think it is necessary to modify enetc_map_tx_tso_hdr().

You are saying this in reply to my observation that the title of the
change does not correctly represent the change. But I don't see how what
you're saying is connected to that. Currently there exists a "count"
variable based on which TX BDs are unmapped, and these patches are not
changing that fact.

> > stylistic nitpick: I think this implementation choice obscures the fact,
> > to an unfamiliar reader, that the requirement for an extended TXBD comes
> > from enetc_map_tx_tso_hdr(). This is because you repeat the condition
> > for skb_vlan_tag_present(), but it's not obvious it's correlated to the
> > other one. Something like the change below is more expressive in this
> > regard, in my opinion:

It seems you were objecting to this other change suggestion instead.
Sure, I mean, ignore it if you want, but you're saying "well I'm going
to change the scheme for net-next, so no point in making the code more
obviously correct in stable branches", but the stable branches aren't
going to pick up the net-next patch - they are essentially frozen except
for bug fixes. I would still recommend writing code that makes the most
sense for stable (to the extent that this is logically part of fixing a
bug), and then writing code that makes most sense for net-next, even if
it implies changing some of it back the way it was.