linux-kernel - Re: [PATCH] MM: Support more pagesizes for MAP_HUGETLB/SHM

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Message-ID: <20121022133534.GR16230@one.firstfloor.org>
Date:	Mon, 22 Oct 2012 15:35:34 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Michael Kerrisk <mtk.manpages@...il.com>,
	akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
	Hillf Danton <dhillf@...il.com>
Subject: Re: [PATCH] MM: Support more pagesizes for MAP_HUGETLB/SHM_HUGETLB v6

On Mon, Oct 22, 2012 at 03:27:33PM +0200, Andi Kleen wrote:
> > Maybe I am missing something obvious, but does this not conflict with
> > include/uapi/asm-generic/mman-common.h:
> > 
> > #ifdef CONFIG_MMAP_ALLOW_UNINITIALIZED
> > # define MAP_UNINITIALIZED 0x4000000
> > ...
> > 
> > 0x4000000 == (1 << 26
> > 
> 
> You're right. Someone added that since I wrote the patch originally.
> I owned them when originally submitted @) Thanks for catching.
> 
> Have to move my bits two up, which will still work, but limit the

Two up won't work, need one up.  

32..28 = 16  is too small for 2^30 = 1GB pages
32..27 = 32  max 4GB pages

So this will use up all remaining flag bits now.

-Andi
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