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From:   Eric Dumazet <edumazet@google.com>
Date:   Sat, 18 Jan 2020 20:12:48 -0800
Message-ID: <CANn89iJ02iFxGibdqO+YWVYX4q4J=W9vv7HOpMVqNK-qZvHcQw@mail.gmail.com>
Subject: Re: [PATCH] net: optimize cmpxchg in ip_idents_reserve
To:     Shaokun Zhang <zhangshaokun@hisilicon.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Eric Dumazet <eric.dumazet@gmail.com>,
        David Miller <davem@davemloft.net>,
        netdev <netdev@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>, jinyuqi@huawei.com,
        Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        guoyang2@huawei.com, Will Deacon <will@kernel.org>
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On Sat, Jan 18, 2020 at 7:47 PM Shaokun Zhang
<zhangshaokun@hisilicon.com> wrote:
>

> We have used the atomic_add_return[1], but it makes the UBSAN unhappy followed
> by the comment.
> It seems that Eric also agreed to do it if some comments are added. I will do
> it later.
>
> Thanks,
> Shaokun
>
> [1] https://lkml.org/lkml/2019/7/26/217
>

In case you have missed it, we needed a proper analysis.
My feedback was quite simple :

<quote>
Have you first checked that current UBSAN versions will not complain anymore ?
</quote>

You never did this work, never replied to my question, and months
later you come back
with a convoluted patch while we simply can proceed with a revert now
we are sure that linux kernels are compiled with the proper option.

As mentioned yesterday, no need for a comment.
Instead the changelog should be explaining why the revert is now safe.