linux-kernel - Re: [PATCH] add __GFP_ZERP to GFP_LEVEL

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Date:	Mon, 23 Jul 2007 12:21:43 +0100
From:	mel@...net.ie (Mel Gorman)
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Christoph Lameter <clameter@....com>,
	Daniel Phillips <phillips@...gle.com>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH] add __GFP_ZERP to GFP_LEVEL_MASK

On (23/07/07 12:03), Peter Zijlstra didst pronounce:
> 
> Daniel recently spotted that __GFP_ZERO is not (and has never been)
> part of GFP_LEVEL_MASK. I could not find a reason for this in the
> original patch: 3977971c7f09ce08ed1b8d7a67b2098eb732e4cd in the -bk
> tree.
> 
> This of course is in stark contradiction with the comment accompanying
> GFP_LEVEL_MASK.

This probably never showed up as a problem because slab is not using
__GFP_ZERO. If a flag is used with slab that is not in the level mask,
it goes *bang* as described in the comment.

Does this patch compile though?

> 
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>

> ---
>  include/linux/gfp.h |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Index: linux-2.6-2/include/linux/gfp.h
> ===================================================================
> --- linux-2.6-2.orig/include/linux/gfp.h
> +++ linux-2.6-2/include/linux/gfp.h
> @@ -56,7 +56,7 @@ struct vm_area_struct;
>  /* if you forget to add the bitmask here kernel will crash, period */
>  #define GFP_LEVEL_MASK (__GFP_WAIT|__GFP_HIGH|__GFP_IO|__GFP_FS| \
>  			__GFP_COLD|__GFP_NOWARN|__GFP_REPEAT| \
> -			__GFP_NOFAIL|__GFP_NORETRY|__GFP_COMP| \
> +			__GFP_NOFAIL|__GFP_NORETRY|__GFP_COMP|__GFP_ZERO \

Should there be a | at the end there?

>  			__GFP_NOMEMALLOC|__GFP_HARDWALL|__GFP_THISNODE| \
>  			__GFP_MOVABLE)
>  
> 
> 
> -
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-- 
-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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