Re: [patch] mremap.2: Add description of old_size == 0 functionality

From	Michal Hocko <mhocko@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [patch] mremap.2: Add description of old_size == 0 functionality
Date	2017-09-25 17:00 +0200
Message-ID	<utD1v-7Jk-9@gated-at.bofh.it> (permalink)
References	(4 earlier) <urpFo-5m4-17@gated-at.bofh.it> <utAQ2-6lU-15@gated-at.bofh.it> <utAZI-6pv-25@gated-at.bofh.it> <utB9p-6tv-43@gated-at.bofh.it> <utBsK-6S0-19@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Mon 25-09-17 15:16:09, Florian Weimer wrote:
> On 09/25/2017 02:52 PM, Michal Hocko wrote:
> > So, how are you going to deal with the CoW and the implementation which
> > basically means that the newm mmap content is not the same as the
> > original one?
> 
> I don't understand why CoW would kick in.

So you can guarantee nobody is going to write to that memory? Moreover
for the anonymous mapping you really get zero pages rather than the
original content AFAIR.

> The approach I outlined is
> desirable because it avoids the need to modify any executable pages, so this
> is not a concern.  The point is to create a potentially unbounded number of
> thunks *without* run-time code generation.
> 
> If the file is rewritten on disk, that's already undefined today, so it's
> not something we need to be concerned with.  (Anything which replaces ELF
> files needs to use the rename-into-place approach anyway.)

Yeah that part is not all that interesting.
-- 
Michal Hocko
SUSE Labs

Thread

[patch] mremap.2: Add description of old_size == 0 functionality Mike Kravetz <mike.kravetz@oracle.com> - 2017-09-15 23:40 +0200
  Re: [patch] mremap.2: Add description of old_size == 0 functionality Mike Kravetz <mike.kravetz@oracle.com> - 2017-09-16 00:00 +0200
    Re: [patch] mremap.2: Add description of old_size == 0 functionality Florian Weimer <fweimer@redhat.com> - 2017-09-18 15:50 +0200
      Re: [patch] mremap.2: Add description of old_size == 0 functionality Mike Kravetz <mike.kravetz@oracle.com> - 2017-09-18 19:20 +0200
        Re: [patch] mremap.2: Add description of old_size == 0 functionality Florian Weimer <fweimer@redhat.com> - 2017-09-19 14:20 +0200
          [patch v2] mremap.2: Add description of old_size == 0 functionality Mike Kravetz <mike.kravetz@oracle.com> - 2017-09-19 23:50 +0200
            Re: [patch v2] mremap.2: Add description of old_size == 0  functionality "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2017-09-20 09:30 +0200
              Re: [patch v2] mremap.2: Add description of old_size == 0  functionality Michal Hocko <mhocko@kernel.org> - 2017-09-25 14:40 +0200
                Re: [patch v2] mremap.2: Add description of old_size == 0 functionality "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2017-09-25 14:50 +0200
              Re: [patch v2] mremap.2: Add description of old_size == 0  functionality Mike Kravetz <mike.kravetz@oracle.com> - 2017-09-25 18:40 +0200
                Re: [patch v2] mremap.2: Add description of old_size == 0 functionality "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2017-09-25 21:30 +0200
          Re: [patch] mremap.2: Add description of old_size == 0 functionality Michal Hocko <mhocko@kernel.org> - 2017-09-25 14:40 +0200
            Re: [patch] mremap.2: Add description of old_size == 0 functionality Florian Weimer <fweimer@redhat.com> - 2017-09-25 14:50 +0200
              Re: [patch] mremap.2: Add description of old_size == 0 functionality Michal Hocko <mhocko@kernel.org> - 2017-09-25 15:00 +0200
                Re: [patch] mremap.2: Add description of old_size == 0 functionality Florian Weimer <fweimer@redhat.com> - 2017-09-25 15:20 +0200
                Re: [patch] mremap.2: Add description of old_size == 0 functionality Michal Hocko <mhocko@kernel.org> - 2017-09-25 17:00 +0200
                Re: [patch] mremap.2: Add description of old_size == 0 functionality Florian Weimer <fweimer@redhat.com> - 2017-09-25 17:00 +0200
  Re: [patch] mremap.2: Add description of old_size == 0 functionality Jann Horn <jannh@google.com> - 2017-09-18 04:00 +0200
    Re: [patch] mremap.2: Add description of old_size == 0 functionality Mike Kravetz <mike.kravetz@oracle.com> - 2017-09-18 19:30 +0200

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