linux-kernel - Re: [PATCH] mm/mremap: Document MREMAP_FIXED dependency on MREMAP

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Message-Id: <d482a336-cc08-a47e-24b8-8d91316f1d0d@linux.vnet.ibm.com>
Date:   Tue, 11 Jul 2017 07:45:32 +0530
From:   Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>,
        Michal Hocko <mhocko@...nel.org>,
        Anshuman Khandual <khandual@...ux.vnet.ibm.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        akpm@...ux-foundation.org
Subject: Re: [PATCH] mm/mremap: Document MREMAP_FIXED dependency on
 MREMAP_MAYMOVE

On 07/10/2017 11:01 PM, Mike Kravetz wrote:
> On 07/10/2017 06:41 AM, Michal Hocko wrote:
>> On Mon 10-07-17 17:02:11, Anshuman Khandual wrote:
>>> In the header file, just specify the dependency of MREMAP_FIXED
>>> on MREMAP_MAYMOVE and make it explicit for the user space.
>> I really fail to see a point of this patch. The depency belongs to the
>> code and it seems that we already enforce it
>> 	if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE))
>> 		return ret;
>>
>> So what is the point here?
> Agree, I am not sure of your reasoning.
> 
> If to assist the programmer, there is no need as this is clearly specified
> in the man page:
> 
> "If  MREMAP_FIXED  is  specified,  then MREMAP_MAYMOVE must also be
>  specified."

Yeah the idea was to assist the programmer and I missed the man page's
details on this. My bad.