From: Matthew Wilcox <willy@infradead.org>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: Cyril Hrubis <chrubis@suse.cz>, Michal Hocko <mhocko@kernel.org>,
Kees Cook <keescook@chromium.org>,
Linux API <linux-api@vger.kernel.org>,
Khalid Aziz <khalid.aziz@oracle.com>,
Andrew Morton <akpm@linux-foundation.org>,
Russell King - ARM Linux <linux@armlinux.org.uk>,
Andrea Arcangeli <aarcange@redhat.com>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-arch <linux-arch@vger.kernel.org>,
Florian Weimer <fweimer@redhat.com>,
John Hubbard <jhubbard@nvidia.com>,
Abdul Haleem <abdhalee@linux.vnet.ibm.com>,
Joel Stanley <joel@jms.id.au>
Subject: Re: [PATCH 0/2] mm: introduce MAP_FIXED_SAFE
Date: Tue, 5 Dec 2017 23:03:55 -0800 [thread overview]
Message-ID: <20171206070355.GA32044@bombadil.infradead.org> (raw)
In-Reply-To: <20171206045433.GQ26021@bombadil.infradead.org>
On Tue, Dec 05, 2017 at 08:54:35PM -0800, Matthew Wilcox wrote:
> On Wed, Dec 06, 2017 at 03:51:44PM +1100, Michael Ellerman wrote:
> > Cyril Hrubis <chrubis@suse.cz> writes:
> >
> > > Hi!
> > >> > MAP_FIXED_UNIQUE
> > >> > MAP_FIXED_ONCE
> > >> > MAP_FIXED_FRESH
> > >>
> > >> Well, I can open a poll for the best name, but none of those you are
> > >> proposing sound much better to me. Yeah, naming sucks...
> > >
> > > Given that MAP_FIXED replaces the previous mapping MAP_FIXED_NOREPLACE
> > > would probably be a best fit.
> >
> > Yeah that could work.
> >
> > I prefer "no clobber" as I just suggested, because the existing
> > MAP_FIXED doesn't politely "replace" a mapping, it destroys the current
> > one - which you or another thread may be using - and clobbers it with
> > the new one.
>
> It's longer than MAP_FIXED_WEAK :-P
>
> You'd have to be pretty darn strong to clobber an existing mapping.
I think we're thinking about this all wrong. We shouldn't document it as
"This is a variant of MAP_FIXED". We should document it as "Here's an
alternative to MAP_FIXED".
So, just like we currently say "exactly one of MAP_SHARED or MAP_PRIVATE",
we could add a new paragraph saying "at most one of MAP_FIXED or
MAP_REQUIRED" and "any of the following values".
Now, we should implement MAP_REQUIRED as having each architecture
define _MAP_NOT_A_HINT, and then #define MAP_REQUIRED (MAP_FIXED |
_MAP_NOT_A_HINT), but that's not information to confuse users with.
Also, that lets us add a third option at some point that is Yet Another
Way to interpret the 'addr' argument, by having MAP_FIXED clear and
_MAP_NOT_A_HINT set.
I'm not set on MAP_REQUIRED. I came up with some awful names
(MAP_TODDLER, MAP_TANTRUM, MAP_ULTIMATUM, MAP_BOSS, MAP_PROGRAM_MANAGER,
etc). But I think we should drop FIXED from the middle of the name.
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next prev parent reply other threads:[~2017-12-06 7:03 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-29 14:42 [PATCH 0/2] mm: introduce MAP_FIXED_SAFE Michal Hocko
2017-11-29 14:42 ` [PATCH 1/2] " Michal Hocko
2017-12-06 5:15 ` Michael Ellerman
2017-12-06 9:27 ` Michal Hocko
2017-12-06 10:02 ` Michal Hocko
2017-12-07 12:07 ` Pavel Machek
2017-11-29 14:42 ` [PATCH 2/2] fs, elf: drop MAP_FIXED usage from elf_map Michal Hocko
2017-11-29 17:45 ` Khalid Aziz
2017-11-29 14:45 ` [PATCH] mmap.2: document new MAP_FIXED_SAFE flag Michal Hocko
2017-11-30 3:16 ` John Hubbard
2017-11-30 8:23 ` Michal Hocko
2017-11-30 8:24 ` [PATCH v2] " Michal Hocko
2017-11-30 18:31 ` John Hubbard
2017-11-30 18:39 ` Michal Hocko
2017-11-29 15:13 ` [PATCH 0/2] mm: introduce MAP_FIXED_SAFE Rasmus Villemoes
[not found] ` <b154b794-7a8b-995e-0954-9234b9446b31-rjjw5hvvQKZaa/9Udqfwiw@public.gmane.org>
2017-11-29 15:50 ` Michal Hocko
2017-11-29 22:15 ` Kees Cook
2017-11-29 22:12 ` Kees Cook
2017-11-29 22:25 ` Kees Cook
[not found] ` <CAGXu5jLa=b2HhjWXXTQunaZuz11qUhm5aNXHpS26jVqb=G-gfw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-11-30 6:58 ` Michal Hocko
2017-12-01 15:26 ` Cyril Hrubis
2017-12-06 4:51 ` Michael Ellerman
2017-12-06 4:54 ` Matthew Wilcox
2017-12-06 7:03 ` Matthew Wilcox [this message]
2017-12-06 7:33 ` John Hubbard
[not found] ` <5f4fc834-274a-b8f1-bda0-5bcddc5902ed-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
2017-12-06 7:35 ` Florian Weimer
2017-12-06 8:06 ` John Hubbard
[not found] ` <27ee1755-76d8-f086-5760-9c973b31108a-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
2017-12-06 8:54 ` Florian Weimer
[not found] ` <20171206070355.GA32044-PfSpb0PWhxZc2C7mugBRk2EX/6BAtgUQ@public.gmane.org>
2017-12-07 5:46 ` Michael Ellerman
2017-12-07 19:14 ` Kees Cook
[not found] ` <CAGXu5jLWRQn6EaXEEvdvXr+4gbiJawwp1EaLMfYisHVfMiqgSA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-12-07 19:57 ` Matthew Wilcox
2017-12-08 8:33 ` Michal Hocko
[not found] ` <20171208083315.GR20234-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org>
2017-12-08 20:13 ` Kees Cook
[not found] ` <CAGXu5j+VupGmKEEHx-uNXw27Xvndu=0ObsBqMwQiaYPyMGD+vw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-12-08 20:57 ` Matthew Wilcox
2017-12-08 11:08 ` Michael Ellerman
2017-12-08 14:27 ` Pavel Machek
2017-12-08 20:31 ` Cyril Hrubis
2017-12-08 20:47 ` Florian Weimer
2017-12-08 14:33 ` David Laight
2017-12-06 4:50 ` Michael Ellerman
[not found] ` <87zi6we9z2.fsf-W0DJWXSxmBNbyGPkN3NxC2scP1bn1w/D@public.gmane.org>
2017-12-06 7:33 ` Rasmus Villemoes
[not found] ` <a3b3129a-2626-a65e-59b0-68aada523723-rjjw5hvvQKZaa/9Udqfwiw@public.gmane.org>
2017-12-06 9:08 ` Michal Hocko
2017-12-07 0:19 ` Kees Cook
2017-12-07 1:08 ` John Hubbard
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