Re: [patch 2/2] slab: always consider arch mandated alignment

From: Pekka J Enberg
Date: Wed Jul 26 2006 - 06:03:42 EST


On Wed, 26 Jul 2006, Heiko Carstens wrote:
> Since ARCH_KMALLOC_MINALIGN didn't work on s390 I tried ARCH_SLAB_MINALIGN
> instead, just to find out that it didn't work too.
> In case of CONFIG_DEBUG_SLAB kmem_cache_create() creates caches with an
> alignment lesser than ARCH_SLAB_MINALIGN, which it shouldn't according to
> this comment in mm/slab.c :

[snip]

> Index: linux-2.6/mm/slab.c
> ===================================================================
> --- linux-2.6.orig/mm/slab.c 2006-07-26 09:55:54.000000000 +0200
> +++ linux-2.6/mm/slab.c 2006-07-26 09:57:07.000000000 +0200
> @@ -2103,6 +2103,9 @@
> if (ralign > BYTES_PER_WORD)
> flags &= ~(SLAB_RED_ZONE | SLAB_STORE_USER);
> }
> + if (BYTES_PER_WORD < ARCH_SLAB_MINALIGN)
> + flags &= ~(SLAB_RED_ZONE | SLAB_STORE_USER);
> +
> /* 3) caller mandated alignment: disables debug if necessary */
> if (ralign < align) {
> ralign = align;

This is similar to my patch and should be enough to fix the problem. The
first patch seems bogus and I don't really understand why you would need
it.

Pekka
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