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Date:   Thu, 23 Mar 2023 13:34:22 -0700
From:   Jakub Kicinski <kuba@kernel.org>
To:     Shay Agroskin <shayagr@amazon.com>
Cc:     Paolo Abeni <pabeni@redhat.com>,
        David Miller <davem@davemloft.net>, <netdev@vger.kernel.org>,
        "Woodhouse, David" <dwmw@amazon.com>,
        "Machulsky, Zorik" <zorik@amazon.com>,
        "Matushevsky, Alexander" <matua@amazon.com>,
        Saeed Bshara <saeedb@amazon.com>,
        "Wilson, Matt" <msw@amazon.com>,
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        "Bshara, Nafea" <nafea@amazon.com>,
        "Belgazal, Netanel" <netanel@amazon.com>,
        "Saidi, Ali" <alisaidi@amazon.com>,
        "Herrenschmidt, Benjamin" <benh@amazon.com>,
        "Kiyanovski, Arthur" <akiyano@amazon.com>,
        "Dagan, Noam" <ndagan@amazon.com>,
        "Arinzon, David" <darinzon@amazon.com>,
        "Itzko, Shahar" <itzko@amazon.com>,
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        Eric Dumazet <edumazet@google.com>,
        Vladimir Oltean <vladimir.oltean@nxp.com>,
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        Guangbin Huang <huangguangbin2@huawei.com>,
        Jie Wang <wangjie125@huawei.com>,
        Johannes Berg <johannes@sipsolutions.net>,
        Edward Cree <ecree.xilinx@gmail.com>,
        "Florian Westphal" <fw@strlen.de>
Subject: Re: [PATCH v6 net-next 1/7] netlink: Add a macro to set policy
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On Thu, 23 Mar 2023 21:44:52 +0200 Shay Agroskin wrote:
> > That's why we have the local variable called __extack, that we 
> > *can*
> > use multiple times, because it's a separate variable, (extack) 
> > is
> > evaluated only once, to initialize it...
> >
> > We don't need to copy the string formatting, unless I'm missing
> > something. Paolo was just asking for:  
> 
> There is an issue with shadowing __extack by NL_SET_ERR_MSG_FMT 
> causing the changes to __extack not to be propagated back to the 
> caller.
> I'm not that big of an expert in C but changing __extack -> 
> _extack fixes the shadowing issue.
> 
> Might not be the most robust solution, though it might suffice for 
> this use case.

TBH the hierarchy should be the other way around, NL_SET_ERR_MSG_FMT()
should be converted to be:

#define NL_SET_ERR_MSG_FMT(extack, attr, msg, args...) \
	NL_SET_ERR_MSG_ATTR_POL_FMT(extack, NULL, NULL, msg, ##args)

and that'd fix the shadowing, right?