linux-kernel - Re: Should mmap MAP_LOCKED fail if mm

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Message-ID: <20150428203625.GA9664@dhcp22.suse.cz>
Date:	Tue, 28 Apr 2015 22:36:25 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	linux-mm <linux-mm@...ck.org>, Cyril Hrubis <chrubis@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	Michel Lespinasse <walken@...gle.com>,
	Rik van Riel <riel@...hat.com>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux API <linux-api@...r.kernel.org>
Subject: Re: Should mmap MAP_LOCKED fail if mm_poppulate fails?

On Tue 28-04-15 11:38:35, Linus Torvalds wrote:
> On Tue, Apr 28, 2015 at 11:35 AM, Michal Hocko <mhocko@...e.cz> wrote:
> >
> > I am still not sure I see the problem here.
> 
> Basically, I absolutely hate the notion of us doing something
> unsynchronized, when I can see us undoing a mmap that another thread
> is doing. It's wrong.
> 
> You also didn't react to all the *other* things that were wrong in
> that patch-set. The games you play with !fatal_signal_pending() etc
> are just crazy.

I planed to get to those later, because I felt the locks vs. racing
mmaps argument was the most important objection.

> End result: I absolutely detest the whole thing. I told you what I
> consider an acceptable solution instead, that is much simpler and
> doesn't have any of the problems of your patchset.

I will surely think about those. As I've written in the cover email
already, I am fine with patching the man page and be clear about a long
term behavior. The primary motivation for this RFC was to start the
discussion.
-- 
Michal Hocko
SUSE Labs
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