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

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Message-ID: <Pine.LNX.4.64.0707240007100.3128@schroedinger.engr.sgi.com>
Date:	Tue, 24 Jul 2007 00:09:47 -0700 (PDT)
From:	Christoph Lameter <clameter@....com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
cc:	Mel Gorman <mel@...net.ie>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Daniel Phillips <phillips@...gle.com>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH] add __GFP_ZERO to GFP_LEVEL_MASK

On Tue, 24 Jul 2007, Peter Zijlstra wrote:

> Then we can either fixup the slab allocators to mask out __GFP_ZERO, or
> do something like the below.
> 
> Personally I like the consistency of adding __GFP_ZERO here (removes
> this odd exception) and just masking it in the sl[aou]b thingies.

There is another exception for __GFP_DMA.

> Anybody else got a preference?

>  #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))
>  
> -/* if you forget to add the bitmask here kernel will crash, period */
> +/*
> + * If you forget to add the bitmask here kernel will crash, period!
> + *
> + * GFP_LEVEL_MASK is used to filter out the flags that are to be passed to the
> + * page allocator.
> + *

GFP_LEVEL_MASK is also used in mm/vmalloc.c. We need a definition that 
goes beyond slab allocators.

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