linux-kernel - Re: [PATCH v4] mmap.2: MAP_FIXED updated documentation

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Message-ID: <20171211090303.GG20234@dhcp22.suse.cz>
Date:   Mon, 11 Dec 2017 10:03:03 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     John Hubbard <jhubbard@...dia.com>
Cc:     Michael Kerrisk <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>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Cyril Hrubis <chrubis@...e.cz>
Subject: Re: [PATCH v4] mmap.2: MAP_FIXED updated documentation

On Sun 10-12-17 18:22:05, John Hubbard wrote:
> On 12/10/2017 02:31 AM, Michal Hocko wrote:
> > On Tue 05-12-17 19:14:34, john.hubbard@...il.com wrote:
> >> From: John Hubbard <jhubbard@...dia.com>
> >>
> >> Previously, MAP_FIXED was "discouraged", due to portability
> >> issues with the fixed address. In fact, there are other, more
> >> serious issues. Also, alignment requirements were a bit vague.
> >> So:
> >>
> >>     -- 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.
> >>
> >> Some of the wording is lifted from Matthew Wilcox's review
> >> (the "Portability issues" section). The alignment requirements
> >> section uses Cyril Hrubis' wording, with light editing applied.
> >>
> >> Suggested-by: Matthew Wilcox <willy@...radead.org>
> >> Suggested-by: Cyril Hrubis <chrubis@...e.cz>
> >> Signed-off-by: John Hubbard <jhubbard@...dia.com>
> > 
> > Would you mind if I take this patch and resubmit it along with my
> > MAP_FIXED_SAFE (or whatever name I will end up with) next week?
> > 
> > Acked-by: Michal Hocko <mhocko@...e.com>
> 
> Sure, that works for me. A tiny complication: I see that Michael
> Kerrisk has already applied the much smaller v2 of this patch (the
> one that "no longer discourages" the option, but that's all), as:
> 
>    ffa518803e14 mmap.2: MAP_FIXED is no longer discouraged
> 
> so this one here will need to be adjusted slightly to merge
> gracefully. Let me know if you want me to respin, or if you
> want to handle the merge.

Yes, please respin.
-- 
Michal Hocko
SUSE Labs