linux-kernel - Re: [PATCH v5] mmap.2: MAP_FIXED updated documentation

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Date:   Tue, 19 Dec 2017 06:35:12 +0100
From:   "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:     John Hubbard <jhubbard@...dia.com>
Cc:     mtk.manpages@...il.com, linux-man <linux-man@...r.kernel.org>,
        linux-api@...r.kernel.org, Michael Ellerman <mpe@...erman.id.au>,
        linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>,
        linux-arch@...r.kernel.org, Jann Horn <jannh@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Michal Hocko <mhocko@...nel.org>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Cyril Hrubis <chrubis@...e.cz>, Michal Hocko <mhocko@...e.com>,
        Pavel Machek <pavel@....cz>
Subject: Re: [PATCH v5] mmap.2: MAP_FIXED updated documentation

Hi John,

On 12/18/2017 10:27 PM, John Hubbard wrote:
> On 12/18/2017 11:15 AM, Michael Kerrisk (man-pages) wrote:
>> On 12/12/2017 01:23 AM, john.hubbard@...il.com wrote:
>>> From: John Hubbard <jhubbard@...dia.com>
>>>
>>>     -- Expand the documentation to discuss the hazards in
>>>        enough detail to allow avoiding them.
>>>
>>>     -- Mention the upcoming MAP_FIXED_SAFE flag.
>>>
>>>     -- Enhance the alignment requirement slightly.
>>>
>>> CC: Michael Ellerman <mpe@...erman.id.au>
>>> CC: Jann Horn <jannh@...gle.com>
>>> CC: Matthew Wilcox <willy@...radead.org>
>>> CC: Michal Hocko <mhocko@...nel.org>
>>> CC: Mike Rapoport <rppt@...ux.vnet.ibm.com>
>>> CC: Cyril Hrubis <chrubis@...e.cz>
>>> CC: Michal Hocko <mhocko@...e.com>
>>> CC: Pavel Machek <pavel@....cz>
>>> Signed-off-by: John Hubbard <jhubbard@...dia.com>
>>
>> John,
>>
>> Thanks for the patch. I think you win the prize for the 
>> most iterations ever on a man-pages patch! (And Michal,
>> thanks for helping out.) I've applied your patch, made 
>> some minor tweaks, and removed the mention of 
>> MAP_FIXED_SAFE, since I don't like to document stuff
>> that hasn't yet been merged. (I only later noticed the
>> fuss about the naming...)
>>
> 
> Hi Michael,
> 
> The final result looks nice, thanks for all the editing fixes.
> 
> One last thing: reading through this, I think it might need a wording
> fix (this is my fault), in order to avoid implying that brk() or
> malloc() use dlopen().
> 
> Something approximately like this:
> 
> diff --git a/man2/mmap.2 b/man2/mmap.2
> index 79681b31e..1c0bd80de 100644
> --- a/man2/mmap.2
> +++ b/man2/mmap.2
> @@ -250,8 +250,9 @@ suffice.
>  The
>  .BR dlopen (3)
>  call will map the library into the process's address space.
> -Furthermore, almost any library call may be implemented using this technique.
> -Examples include
> +Furthermore, almost any library call may be implemented in a way that
> +adds memory mappings to the address space, either with this technique,
> +or by simply allocating memory. Examples include
>  .BR brk (2),
>  .BR malloc (3),
>  .BR pthread_create (3),
> 
> 
> ...or does the current version seem OK to other people?

Thanks. Looks good to me. Applied.

Cheers,

Michael



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