linux-kernel - Re: [PATCH] mm: kill kmemcheck again

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Message-ID: <20170930200239.ngcyp2tcpuidpctv@sasha-lappy>
Date:   Sat, 30 Sep 2017 20:02:41 +0000
From:   "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>
To:     Vegard Nossum <vegard.nossum@...il.com>
CC:     Steven Rostedt <rostedt@...dmis.org>,
        Michal Hocko <mhocko@...nel.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Alexander Potapenko <glider@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH] mm: kill kmemcheck again

On Sat, Sep 30, 2017 at 03:57:27PM +0200, Vegard Nossum wrote:
>On 30 September 2017 at 11:48, Steven Rostedt <rostedt@...dmis.org> wrote:
>> On Wed, 27 Sep 2017 17:02:07 +0200
>> Michal Hocko <mhocko@...nel.org> wrote:
>>
>>> > Now that 2 years have passed, and all distros provide gcc that supports
>>> > KASAN, kill kmemcheck again for the very same reasons.
>>>
>>> This is just too large to review manually. How have you generated the
>>> patch?
>>
>> I agree. This needs to be taken out piece by piece, not in one go,
>> where there could be unexpected fallout.
>
>I have a patch from earlier this year that starts by removing the core
>code and defining all the helpers/flags as no-ops so they can be
>removed bit by bit at a later time. See the attachment. Pekka signed
>off on it too.
>e
>I never actually submitted this because I was waiting for MSAN to be

I'm not sure how much value there is in doing it this way. I agree that the patch is big, but most of it is simply removing code under arch/x86/mm/kmemcheck.

The difference between Vegard's patch and mine is about 300 lines (out of 2800+), where those 300 lines are simply removing calls to kmemcheck. There are no logic changes. (so something very similar to 's/*kmemcheck*//g' would do the trick).

--

Thanks,
Sasha