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From: Michael Ellerman <mpe-Gsx/Oe8HsFggBc27wqDAHg@public.gmane.org>
To: Matthew Wilcox <willy-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
Cc: Cyril Hrubis <chrubis-AlSwsSmVLrQ@public.gmane.org>,
	Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	Kees Cook <keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
	Linux API <linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Khalid Aziz <khalid.aziz-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>,
	Andrew Morton
	<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
	Russell King - ARM Linux
	<linux-I+IVW8TIWO2tmTQ+vhA3Yw@public.gmane.org>,
	Andrea Arcangeli
	<aarcange-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Linux-MM <linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org>,
	LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	linux-arch <linux-arch-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Florian Weimer <fweimer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	John Hubbard <jhubbard-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>,
	Abdul Haleem
	<abdhalee-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>,
	Joel Stanley <joel-U3u1mxZcP9KHXe+LvDLADg@public.gmane.org>
Subject: Re: [PATCH 0/2] mm: introduce MAP_FIXED_SAFE
Date: Thu, 07 Dec 2017 16:46:11 +1100
Message-ID: <87bmjbks4c.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <20171206070355.GA32044-PfSpb0PWhxZc2C7mugBRk2EX/6BAtgUQ@public.gmane.org>

Matthew Wilcox <willy-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org> writes:

> 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-AlSwsSmVLrQ@public.gmane.org> 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.

MAP_REQUIRED doesn't immediately grab me, but I don't actively dislike
it either :)

What about MAP_AT_ADDR ?

It's short, and says what it does on the tin. The first argument to mmap
is actually called "addr" too.

cheers

  parent reply index

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-11-29 14:42 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
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 [this message]
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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