Re: [PATCH 1/4] block: use ARCH_KMALLOC_MINALIGN as the default dma pad mask

[Paul Mundt <lethal@linux-sh.org>]

On Tue, May 20, 2008 at 02:31:29AM -0700, Andrew Morton wrote:
> Why does ARCH_KMALLOC_MINALIGN even exist?  What is its mandate?  Sigh.
> 
> It's not really related to your patch (although your patch compounds
> the problem a little).  But we should sit down and work out what we
> actually want to do here.  Something like:
> 
> In each architecture's arch/foo/Kconfig, define
> 
> 	CONFIG_ARCH_DMA_ALIGN
> 
> and
> 
> 	CONFIG_ARCH_64BIT_POINTER_ALIGN
> 
> and then use them.  Note that these have nothing to do with each other,
> as far as I can tell.
> 
> Which leaves the question: "what should slab use"?  Maybe
> CONFIG_ARCH_DMA_ALIGN?  But that depends what ARCH_KMALLOC_MINALIGN is
> supposed to exist for.
> 
> ick.
> 
The only platforms that set ARCH_KMALLOC_MINALIGN appear to do so for DMA
alignment reasons, so your Kconfig option there seems reasonable.

The ARCH_SLAB_MINALIGN you can blame me for:

	http://marc.info/?l=linux-kernel&m=110227138116749&w=2

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