Re: [PATCH] mm/slob: avoid type warning about alignment value

From: David Rientjes
Date: Tue Jul 10 2012 - 21:18:14 EST


On Tue, 10 Jul 2012, Arnd Bergmann wrote:

> diff --git a/mm/slob.c b/mm/slob.c
> index 95d1c7d..51d6a27 100644
> --- a/mm/slob.c
> +++ b/mm/slob.c
> @@ -426,7 +426,7 @@ out:
> void *__kmalloc_node(size_t size, gfp_t gfp, int node)
> {
> unsigned int *m;
> - int align = max(ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
> + int align = max_t(size_t, ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
> void *ret;
>
> gfp &= gfp_allowed_mask;
> @@ -479,7 +479,7 @@ void kfree(const void *block)
>
> sp = virt_to_page(block);
> if (PageSlab(sp)) {
> - int align = max(ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
> + int align = max_t(size_t, ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
> unsigned int *m = (unsigned int *)(block - align);
> slob_free(m, *m + align);
> } else
> @@ -498,7 +498,7 @@ size_t ksize(const void *block)
>
> sp = virt_to_page(block);
> if (PageSlab(sp)) {
> - int align = max(ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
> + int align = max_t(size_t, ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
> unsigned int *m = (unsigned int *)(block - align);
> return SLOB_UNITS(*m) * SLOB_UNIT;
> } else

Wouldn't it be better to avoid this problem more generally by casting the
__alignof__ for ARCH_{KMALLOC,SLAB}_MINALIGN to int in slab.h? All
architectures that define these themselves will be using plain integers,
the problem is __alignof__ returning size_t when undefined.
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