linux-kernel - Re: [PATCH] Fix for hugetlb-add-map_hugetlb-for-mmaping-pseudo-anonymous-huge-page-regions.patch in -mm

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Message-ID: <Pine.LNX.4.64.0909152146470.25625@sister.anvils>
Date:	Tue, 15 Sep 2009 21:53:12 +0100 (BST)
From:	Hugh Dickins <hugh.dickins@...cali.co.uk>
To:	Eric B Munson <ebmunson@...ibm.com>
cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, linux-man@...r.kernel.org,
	mtk.manpages@...il.com, randy.dunlap@...cle.com,
	Arnd Bergman <arnd@...db.de>
Subject: Re: [PATCH] Fix for hugetlb-add-map_hugetlb-for-mmaping-pseudo-anonymous-huge-page-regions.patch
 in -mm

On Tue, 15 Sep 2009, Eric B Munson wrote:
> Resending because this seems to have fallen between the cracks.

Yes, indeed.  I think it isn't quite what Arnd was suggesting, but I
agree with you that we might as well go for 0x080000 (so that even Alpha
can be just a cut-and-paste job from asm-generic), and right now it's
more important to finalize the number than what file it appears in.

Acked-by: Hugh Dickins <hugh.dickins@...cali.co.uk>

> 
> The patch
> hugetlb-add-map_hugetlb-for-mmaping-pseudo-anonymous-huge-page-regions.patch
> used the value 0x40 for MAP_HUGETLB which is the same value used for
> various other flags on some architectures.  This collision causes
> unexpected use of huge pages in the best case and mmap to fail with
> ENOMEM or ENOSYS in the worst.  This patch changes the value for
> MAP_HUGETLB to a value that is not currently used on any arch.
> 
> This patch should be considered a fix to
> hugetlb-add-map_hugetlb-for-mmaping-pseudo-anonymous-huge-page-regions.patch.
> 
> Reported-by: Hugh Dickins <hugh.dickins@...cali.co.uk>
> Signed-off-by: Eric B Munson <ebmunson@...ibm.com>
> ---
>  include/asm-generic/mman-common.h |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/include/asm-generic/mman-common.h b/include/asm-generic/mman-common.h
> index 12f5982..e6adb68 100644
> --- a/include/asm-generic/mman-common.h
> +++ b/include/asm-generic/mman-common.h
> @@ -19,7 +19,7 @@
>  #define MAP_TYPE	0x0f		/* Mask for type of mapping */
>  #define MAP_FIXED	0x10		/* Interpret addr exactly */
>  #define MAP_ANONYMOUS	0x20		/* don't use a file */
> -#define MAP_HUGETLB	0x40		/* create a huge page mapping */
> +#define MAP_HUGETLB	0x080000	/* create a huge page mapping */
>  
>  #define MS_ASYNC	1		/* sync memory asynchronously */
>  #define MS_INVALIDATE	2		/* invalidate the caches */
> -- 
> 1.6.3.2
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