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From: Alexander Aring <aring@mojatatu.com>
Date: Fri, 2 Mar 2018 09:21:56 -0500
Message-ID: <CAOHTApiUzfew+RnGYaKTOduaYmWEEO+N+MkJkDSQjDZ_ySJNGw@mail.gmail.com>
Subject: Re: [patch net-next 09/10] net: sch: prio: Add offload ability for
 grafting a child
To: Jiri Pirko <jiri@resnulli.us>
Cc: Jakub Kicinski <kubakici@wp.pl>, netdev@vger.kernel.org,
        nogahf@mellanox.com, yuvalm@mellanox.com,
        David Miller <davem@davemloft.net>, idosch@mellanox.com,
        mlxsw@mellanox.com, Jamal Hadi Salim <jhs@mojatatu.com>,
        Cong Wang <xiyou.wangcong@gmail.com>, kernel@mojatatu.com
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Hi,

On Fri, Mar 2, 2018 at 3:37 AM, Jiri Pirko <jiri@resnulli.us> wrote:
> Fri, Mar 02, 2018 at 04:48:40AM CET, kubakici@wp.pl wrote:
>>On Thu, 1 Mar 2018 22:38:50 -0500, Alexander Aring wrote:
>>> I guess to make extack working, you need to return an errno if failed.
>>
>>AFAIK extack is printed as a warning if operation did not fail.
>
> Yes, I checked this and it is printed as warning.

ouch, so far I know extack it allows only one messages delivered back
to the user space.

If we introduce a warning in the successful path here, it could be
that in the callpath (after "successful" part of this callback), that
somebody else want to add a warning and overwrites actually your
warning (even, he is not aware that this warning was set - okay I
suppose you can do another check on NULL and set a warning, that
somebody overwrites a warning :-D).

If extack messages get's append and is some kind of for_each_nested
string in netlink -> we have no problem, but I guess this not how it's
working. :-/

- Alex