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

Andrew Morton
2008-05-20T09:52:31Z

On Tue, 20 May 2008 17:38:20 +0800 Herbert Xu <herbert@gondor.apana.org.au> wrote:

> On Tue, May 20, 2008 at 02:31:29AM -0700, Andrew Morton wrote:
> >
> > So here you're using it for "dma aligment" whereas crypto is using it
> > (or ARCH_SLAB_MINALIGN!) for "cpu 64-bit alignment".
>
> No the 64-bit alignment is just an example. The purpose of
> CRYPTO_MINALIGN is pretty much the same as ARCH_KMALLOC_MINALIGN,
> i.e., the minimum alignment guaranteed by kmalloc. The only
> reason it exists is because ARCH_KMALLOC_MINALIGN isn't defined
> on all platforms.

I'm struggling to understand what you're saying here.

The comment you have there over the CRYPTO_MINALIGN definition is quite
specific. Is it wrong?

Whether the mapping between CRYPTO_MINALIGN and ARCH_KMALLOC_MINALIGN
is abusive is (I find) hard to say, because first one would need to be
able to say what ARCH_KMALLOC_MINALIGN is for. I expect it was for DMA
purposes.