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

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Date:   Mon, 18 Sep 2017 10:19:09 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Jann Horn <jannh@...gle.com>
Cc:     Michael Kerrisk-manpages <mtk.manpages@...il.com>,
        linux-man@...r.kernel.org,
        kernel list <linux-kernel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        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>,
        linux-mm@...ck.org
Subject: Re: [patch] mremap.2: Add description of old_size == 0 functionality

On 09/17/2017 06:52 PM, Jann Horn wrote:
> On Fri, Sep 15, 2017 at 2:37 PM, Mike Kravetz <mike.kravetz@...cle.com> wrote:
> [...]
>> A recent change was made to mremap so that an attempt to create a
>> duplicate a private mapping will fail.
>>
>> commit dba58d3b8c5045ad89c1c95d33d01451e3964db7
>> Author: Mike Kravetz <mike.kravetz@...cle.com>
>> Date:   Wed Sep 6 16:20:55 2017 -0700
>>
>>     mm/mremap: fail map duplication attempts for private mappings
>>
>> This return code is also documented here.
> [...]
>> diff --git a/man2/mremap.2 b/man2/mremap.2
> [...]
>> @@ -174,7 +189,12 @@ and
>>  or
>>  .B MREMAP_FIXED
>>  was specified without also specifying
>> -.BR MREMAP_MAYMOVE .
>> +.BR MREMAP_MAYMOVE ;
>> +or \fIold_size\fP was zero and \fIold_address\fP does not refer to a
>> +private anonymous mapping;
> 
> Shouldn't this be the other way around? "or old_size was zero and
> old_address refers to a private anonymous mapping"?

Thanks Jann,

Yes that is wrong.  In addition, the description of this functionality
in the section before this is also incorrect.

I will fix both in a new version of the patch.

-- 
Mike Kravetz