netdev - Re: [PATCH net-next v3 1/2] netdev-genl: Add an XSK attribute to queues

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Message-ID: <Z6Vl6lcPpj1qBN5e@LQ3V64L9R2>
Date: Thu, 6 Feb 2025 17:46:18 -0800
From: Joe Damato <jdamato@...tly.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: netdev@...r.kernel.org, Donald Hunter <donald.hunter@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Stanislav Fomichev <sdf@...ichev.me>,
	Mina Almasry <almasrymina@...gle.com>,
	Daniel Jurgens <danielj@...dia.com>,
	Martin Karsten <mkarsten@...terloo.ca>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next v3 1/2] netdev-genl: Add an XSK attribute to
 queues

On Thu, Feb 06, 2025 at 05:41:38PM -0800, Jakub Kicinski wrote:
> On Thu, 6 Feb 2025 17:31:47 -0800 Joe Damato wrote:
> > > nla_nest_start() can fail, you gotta nul-check the return value.
> > > You could possibly add an nla_put_empty_nest() helper in netlink.h
> > > to make this less awkward? I think the iouring guys had the same bug  
> > 
> > Ah, right.
> > 
> > I'll see what a helper looks like. Feels like maybe overkill?
> 
> Yeah, not sure either. Technically nla_nest_end() isn't required here,
> but that's not very obvious to a casual reader. So a helper that hides
> that fact could be useful:
> 
> static inline int nla_put_empty_nest(struct sk_buff *skb, int attrtype)
> {
> 	return nla_nest_start(skb, attrtype) ? 0 : -EMSGSIZE;
> }

Yea after reading the code it makes sense that nla_nest_end is not
needed. I wrote a small thing similar to what you proposed above,
but yours is more succinct.

I'll go with that and see how it looks.

> But totally unsure whether it's worthwhile. Just don't want for someone
> to suggest this on v4 and make you respin once again.

No worries; respinning is not the end of the world.