linux-kernel - Re: [PATCH 1/5] asm-generic: cosmetic updates to uapi/asm/mman.h

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Message-Id: <a44eb23a-97cf-4920-8cee-5197754d28f6@app.fastmail.com>
Date: Thu, 26 Sep 2024 09:41:48 +0000
From: "Arnd Bergmann" <arnd@...db.de>
To: "Helge Deller" <deller@....de>, "Arnd Bergmann" <arnd@...nel.org>,
 linux-mm@...ck.org
Cc: "Jason A . Donenfeld" <Jason@...c4.com>,
 "Alexander Viro" <viro@...iv.linux.org.uk>,
 "Alexandre Torgue" <alexandre.torgue@...s.st.com>,
 "Andreas Larsson" <andreas@...sler.com>,
 "Andrew Morton" <akpm@...ux-foundation.org>,
 "Ard Biesheuvel" <ardb@...nel.org>,
 "Christian Brauner" <brauner@...nel.org>,
 "Christoph Hellwig" <hch@....de>,
 "Christophe Leroy" <christophe.leroy@...roup.eu>,
 "Damien Le Moal" <dlemoal@...nel.org>,
 "David Hildenbrand" <david@...hat.com>,
 "Greg Ungerer" <gerg@...ux-m68k.org>, "Kees Cook" <kees@...nel.org>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>,
 "Lorenzo Stoakes" <lorenzo.stoakes@...cle.com>,
 "Matt Turner" <mattst88@...il.com>, "Max Filippov" <jcmvbkbc@...il.com>,
 "Michael Ellerman" <mpe@...erman.id.au>,
 "Michal Hocko" <mhocko@...e.com>, "Nicholas Piggin" <npiggin@...il.com>,
 "Richard Henderson" <richard.henderson@...aro.org>,
 "Thomas Bogendoerfer" <tsbogend@...ha.franken.de>,
 "Vladimir Murzin" <vladimir.murzin@....com>,
 "Vlastimil Babka" <vbabka@...e.cz>,
 linux-stm32@...md-mailman.stormreply.com, linux-kernel@...r.kernel.org,
 linux-mips@...r.kernel.org, linux-parisc@...r.kernel.org,
 linuxppc-dev@...ts.ozlabs.org, Linux-Arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH 1/5] asm-generic: cosmetic updates to uapi/asm/mman.h

On Thu, Sep 26, 2024, at 09:21, Helge Deller wrote:
> On 9/25/24 23:06, Arnd Bergmann wrote:

>> -/* not used by linux, but here to make sure we don't clash with OSF/1 defines */
>> -#define _MAP_HASSEMAPHORE 0x0200
>> -#define _MAP_INHERIT	0x0400
>> -#define _MAP_UNALIGNED	0x0800
>
> I suggest to keep ^^ those. It's useful information which isn't
> easily visible otherwise.

Fair enough. I removed them in order to bring the differences
between files to an absolute minimum, but since at the end
of the series the files only contain the map values, there is
no real harm in keeping them, and they may help.

>> -/* not used by linux, but here to make sure we don't clash with ABI defines */
>> -#define MAP_RENAME	0x020		/* Assign page to file */
>> -#define MAP_AUTOGROW	0x040		/* File may grow by writing */
>> -#define MAP_LOCAL	0x080		/* Copy on fork/sproc */
>> -#define MAP_AUTORSRV	0x100		/* Logical swap reserved on demand */
>
> same here. I think they should be preserved.

Right.

>>   /* 0x01 - 0x03 are defined in linux/mman.h */
>> -#define MAP_TYPE	0x00f		/* Mask for type of mapping */
>> -#define MAP_FIXED	0x010		/* Interpret addr exactly */
>> +#define MAP_TYPE	0x0f		/* Mask for type of mapping */
>> +#define MAP_FIXED	0x10		/* Interpret addr exactly */
>>
>> -/* not used by linux, but here to make sure we don't clash with ABI defines */
>> -#define MAP_RENAME	0x020		/* Assign page to file */
>> -#define MAP_AUTOGROW	0x040		/* File may grow by writing */
>> -#define MAP_LOCAL	0x080		/* Copy on fork/sproc */
>> -#define MAP_AUTORSRV	0x100		/* Logical swap reserved on demand */
>
> If xtensa had those, those should be kept as well IMHO.

The thing with xtensa is that the file was blindly copied from
mips, so I'm sure it never had these, but there may be value
in keeping the two files in sync anyway. The only difference
at the moment is MAP_UNINITIALIZED, which is potentially
used on xtensa-nommu.

Let's see if Max Filippov has an opinion on this, otherwise I'd
keep it the same as mips.

      Arnd