linux-kernel - Re: [PATCH v1 0/7] Remove in-tree usage of MAP

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Message-ID: <CAHk-=wifW=eDZdOdydRTmupzzJj=6A+Z5dLFrjM3Hfmxj6DfyA@mail.gmail.com>
Date:   Thu, 12 Aug 2021 08:21:20 -1000
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Florian Weimer <fweimer@...hat.com>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        Andy Lutomirski <luto@...nel.org>,
        David Hildenbrand <david@...hat.com>,
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Subject: Re: [PATCH v1 0/7] Remove in-tree usage of MAP_DENYWRITE

On Thu, Aug 12, 2021 at 8:16 AM Florian Weimer <fweimer@...hat.com> wrote:
>
> I think this is called MAP_COPY:
>
>   <https://www.gnu.org/software/hurd/glibc/mmap.html>

Please don't even consider the crazy notions that GNU Hurd did.

It's a fundamental design mistake. The Hurd VM was horrendous, and
MAP_COPY was a prime example of the kinds of horrors it had.

I'm not sure how much of the mis-designs were due to Hurd, and how
much of it due to Mach 3. But please don't point to Hurd VM
documentation except possibly to warn people. We want people to
_forget_ those mistakes, not repeat them.

          Linus