linux-kernel - Re: [patch] mremap.2: Add description of old

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Message-ID: <d06a26f1-5509-bd85-74bc-b08c3db0cb0d@redhat.com>
Date:   Mon, 25 Sep 2017 16:54:39 +0200
From:   Florian Weimer <fweimer@...hat.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Mike Kravetz <mike.kravetz@...cle.com>, mtk.manpages@...il.com,
        linux-man@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org, Andrea Arcangeli <aarcange@...hat.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
        linux-mm@...ck.org
Subject: Re: [patch] mremap.2: Add description of old_size == 0 functionality

On 09/25/2017 04:52 PM, Michal Hocko wrote:
> 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?

It's mapped readable and executable, but not writable.  So the only 
thing that could interfere would be a debugger.

Thanks,
Florian