netdev - Re: [PATCH 3/7] netlink: set extack error message in nla

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Date:   Wed, 19 Sep 2018 18:31:11 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     David Ahern <dsahern@...il.com>, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH 3/7] netlink: set extack error message in nla_validate()

On Wed, 2018-09-19 at 09:20 -0700, David Ahern wrote:

> >  	nla_for_each_attr(nla, head, len, rem) {
> > -		int err = validate_nla(nla, maxtype, policy, NULL);
> > +		static const char _msg[] = "Attribute failed policy validation";
> > +		const char *msg = _msg;
> > +		int err = validate_nla(nla, maxtype, policy, &msg);
> >  
> >  		if (err < 0) {
> > +			if (extack)
> > +				extack->_msg = msg;
> >  			NL_SET_BAD_ATTR(extack, nla);
> 
> msg, NL_SET_BAD_ATTR and extack handling all can be done in validate_nla
> removing the need for the same message ("Attribute failed policy
> validation") to be declared twice and simplifying the extack setting.

Yeah, perhaps I should take another look at that. I didn't want to do
that originally as validate_nla() has so many exit points, but perhaps
it's better to put a goto label there.

FWIW, in the next patch I'm getting rid of the duplication again - I
wanted to have the patch that has an effect (this one, setting the
message) more clearly separated.

johannes