Re: [PATCH 3/8] arch: uapi: asm: mman.h: Let MADV_FREE have same value for all architectures

[Minchan Kim <minchan@kernel.org>]

On Sun, Nov 01, 2015 at 04:08:27PM -0800, Hugh Dickins wrote:
> On Fri, 30 Oct 2015, Minchan Kim wrote:
> > From: Chen Gang <gang.chen.5i5j@gmail.com>
> > 
> > For uapi, need try to let all macros have same value, and MADV_FREE is
> > added into main branch recently, so need redefine MADV_FREE for it.
> > 
> > At present, '8' can be shared with all architectures, so redefine it to
> > '8'.
> > 
> > Cc: rth@twiddle.net <rth@twiddle.net>,
> > Cc: ink@jurassic.park.msu.ru <ink@jurassic.park.msu.ru>
> > Cc: mattst88@gmail.com <mattst88@gmail.com>
> > Cc: Ralf Baechle <ralf@linux-mips.org>
> > Cc: jejb@parisc-linux.org <jejb@parisc-linux.org>
> > Cc: deller@gmx.de <deller@gmx.de>
> > Cc: chris@zankel.net <chris@zankel.net>
> > Cc: jcmvbkbc@gmail.com <jcmvbkbc@gmail.com>
> > Cc: Arnd Bergmann <arnd@arndb.de>
> > Cc: linux-arch@vger.kernel.org
> > Cc: linux-api@vger.kernel.org
> > Acked-by: Minchan Kim <minchan@kernel.org>
> > Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
> 
> Let me add
> Acked-by: Hugh Dickins <hughd@google.com>
> to this one too.
> 
> But I have extended your mail's Cc list: Darrick pointed out earlier
> that dietlibc has a Solaris #define MADV_FREE 0x5 in its mman.h,
> and that was in the kernel's sparc mman.h up until 2.6.25.  I doubt
> that presents any obstacle nowadays, but Dave Miller should be Cc'ed.
> 
> I was a little suspicious that 8 is available for MADV_FREE: why did
> the common/generic parameters start at 9 instead of 8 back in 2.6.16?
> I think the answer is that we had MADV_REMOVE coming in from one
> direction, and MADV_DONTFORK coming from another direction, and when
> Roland looked for where to start the commons for MADV_DONTFORK, it
> appeared that 8 was occupied - by MADV_REMOVE; then a little later
> MADV_REMOVE was shifted to become the first of the commons, at 9.

Thanks for Ack, Ccing relevant people and history!