linux-kernel - Re: [patch v2] mremap.2: Add description of old

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Message-ID: <CAKgNAkhJEyK=LhFj9W-RgSv+ET64d+MaEAQ41y5eximfQmYPDw@mail.gmail.com>
Date:   Mon, 25 Sep 2017 21:26:42 +0200
From:   "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>
Cc:     linux-man <linux-man@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        Jann Horn <jannh@...gle.com>,
        Florian Weimer <fweimer@...hat.com>,
        Michal Hocko <mhocko@...e.com>,
        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>
Subject: Re: [patch v2] mremap.2: Add description of old_size == 0 functionality

Hi Mike,

On 25 September 2017 at 18:33, Mike Kravetz <mike.kravetz@...cle.com> wrote:
> On 09/20/2017 12:25 AM, Michael Kerrisk (man-pages) wrote:

[...]

>> I've applied this, and added Reviewed-by tags for Florian and Jann.
>> But, I think it's also worth noting the older, now disallowed, behavior,
>> and why the behavior was changed. So I added a note in BUGS:
>>
>>     BUGS
>>        Before Linux 4.14, if old_size was zero and the  mapping  referred
>>        to  by  old_address  was  a private mapping (mmap(2) MAP_PRIVATE),
>>        mremap() created a new private mapping unrelated to  the  original
>>        mapping.   This behavior was unintended and probably unexpected in
>>        user-space applications (since the intention  of  mremap()  is  to
>>        create  a new mapping based on the original mapping).  Since Linux
>>        4.14, mremap() fails with the error EINVAL in this scenario.
>>
>> Does that seem okay?
>
> Sorry for the late reply Michael,  I've been away for a few days.
>
> Yes, the above seems okay.  Thanks for your help with this.

You're welcome. Thanks for checking it over!

Cheers,

Michael

-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/