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From: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Date: Fri, 1 Jun 2012 15:37:37 -0400
Message-ID: <CAHGf_=qDy79cvHX3ym7RvkX7q9+2TDKhgtBHVj6+XHORczj94A@mail.gmail.com>
Subject: Re: [PATCH 0/6] mempolicy memory corruption fixlet
To: david@lang.hm
Cc: Christoph Lameter <cl@linux.com>, Andi Kleen <andi@firstfloor.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Andrew Morton <akpm@google.com>, Dave Jones <davej@redhat.com>,
        Mel Gorman <mgorman@suse.de>, stable@vger.kernel.org, hughd@google.com,
        sivanich@sgi.com
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>>>>>> Yes, that's right direction, I think. Currently, shmem_set_policy()
>>>>>> can't handle
>>>>>> nonlinear mapping.
>>>>>
>>>>> I've been mulling for some time to just remove non linear mappings.
>>>>> AFAIK they were only useful on 32bit and are obsolete and could be
>>>>> emulated with VMAs instead.
>>>>
>>>>
>>>> I agree. It is only userful on 32bit and current enterprise users don't
>>>> use
>>>> 32bit anymore. So, I don't think emulated by vmas cause user visible
>>>> issue.
>>>
>>>
>>> I wish this was true, there are a lot of systems out there still running
>>> 32
>>> bit linux, even on 64 bit capible hardware. This is especially true in
>>> enterprises where they have either homegrown or proprietary software that
>>> isn't 64 bit clean.
>>
>> 32 bit binaries (and entire distros) run fine under 64 bit kernels.
>
> unfortunantly, not quite 100% of the time. It's very good, but the automount
> bug a month or so ago is an example of how you can run into rare problems.
> Many "enterprise" systems are not willing to risk it.

Then we can remove a feature safely. Risk not taker continue to uses old distro
kernel. And some years after, distros discontinue to support 32bit. And then,
problem will vanish automatically.
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