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    SubjectRe: [patch 2/2] slab: always consider arch mandated alignment
    On Wed, Jul 26, 2006 at 01:37:42PM +0300, Pekka J Enberg wrote:
    > On Wed, 26 Jul 2006, Heiko Carstens wrote:
    > > It's enough to fix the ARCH_SLAB_MINALIGN problem. But it does _not_ fix the
    > > ARCH_KMALLOC_MINALIGN problem. s390 currently only uses ARCH_KMALLOC_MINALIGN
    > > since that should be good enough and it doesn't disable as much debugging
    > > as ARCH_SLAB_MINALIGN does.
    > > What exactly isn't clear from the description of the first patch? Or why do
    > > you consider it bogus?
    >
    > Now I am confused. What do you mean by "doesn't disable as much debugging
    > as ARCH_SLAB_MINALIGN does"? AFAICT, the SLAB_RED_ZONE and SLAB_STORE_USER
    > options _require_ BYTES_PER_WORD alignment, so if s390 requires 8
    > byte alignment, you can't have them debugging anyhow...

    We only specify ARCH_KMALLOC_MINALIGN, since that aligns only the kmalloc
    caches, but it doesn't disable debugging on other caches that are created
    via kmem_cache_create() where an alignment of e.g. 0 is specified.

    The point of the first patch is: why should the slab cache be allowed to chose
    an aligment that is less than what the caller specified? This does very likely
    break things.
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