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From:   Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Date:   Tue, 27 Oct 2020 09:13:29 -0400
Message-ID: <CAF=yD-+izgrvj2diXK9=mztq+z0Gb8eVJYB78zUyP5U_WsMY4A@mail.gmail.com>
Subject: Re: [PATCH v3 2/3] net: add kcov handle to skb extensions
To:     Aleksandr Nogikh <nogikh@google.com>
Cc:     Aleksandr Nogikh <aleksandrnogikh@gmail.com>,
        David Miller <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Johannes Berg <johannes@sipsolutions.net>,
        Eric Dumazet <edumazet@google.com>,
        Andrey Konovalov <andreyknvl@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Marco Elver <elver@google.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Network Development <netdev@vger.kernel.org>,
        linux-wireless <linux-wireless@vger.kernel.org>
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On Tue, Oct 27, 2020 at 8:31 AM Aleksandr Nogikh <nogikh@google.com> wrote:
>
> On Mon, Oct 26, 2020 at 7:57 PM Willem de Bruijn
> <willemdebruijn.kernel@gmail.com> wrote:
> [...]
> > If the handle does not need to be set if zero, why then set it if the
> > skb has extensions?
>
> The point of that condition is to avoid unnecessary allocations of skb ex=
tension
> objects. At the same time, one would expect skb_get_kcov_handle to return=
 the
> latest value that was set via skb_set_kcov_handle. So if a buffer already=
 has a
> non-zero kcov_handle and skb_set_kcov_handle is called to set it to zero,=
 it
> should be set to zero.

I see. I thought it was some best effort approach: if there happens to
be space, use it, but don't allocate. Which I did not understand.
Could you rephrase the comment to make more clear that this is about
clearing a possibly previously set value.


> > skb_ext_add and skb_ext_find are not defined unless CONFIG_SKB_EXTENSIO=
NS.
> >
> > Perhaps CONFIG_KCOV should be made to select that?
>
> Yes, thank you for pointing it out. I=E2=80=99ll fix it in the next versi=
on.