slab, slub, slob: Unify alignment definition

Every slab has its on alignment definition in include/linux/sl?b_def.h. Extract those
and define a common set in include/linux/slab.h.

SLOB: As notes sometimes we need double word alignment on 32 bit. This gives all
structures allocated by SLOB a unsigned long long alignment like the others do.

SLAB: If ARCH_SLAB_MINALIGN is not set SLAB would set ARCH_SLAB_MINALIGN to
zero meaning no alignment at all. Give it the default unsigned long long alignment.

Signed-off-by: Christoph Lameter <[e-mail]>
Signed-off-by: Pekka Enberg <[e-mail]>

include/linux/slab.h

···
 #define KMALLOC_MAX_SIZE	(1UL << KMALLOC_SHIFT_HIGH)
 #define KMALLOC_MAX_ORDER	(KMALLOC_SHIFT_HIGH - PAGE_SHIFT)
 
+#ifdef ARCH_DMA_MINALIGN
+#define ARCH_KMALLOC_MINALIGN ARCH_DMA_MINALIGN
+#else
+#define ARCH_KMALLOC_MINALIGN __alignof__(unsigned long long)
+#endif
+
+#ifndef ARCH_SLAB_MINALIGN
+#define ARCH_SLAB_MINALIGN __alignof__(unsigned long long)
+#endif
+
 /*
  * Common kmalloc functions provided by all allocators
  */

include/linux/slab_def.h

···
 #include <trace/events/kmem.h>
 
 /*
- * Enforce a minimum alignment for the kmalloc caches.
- * Usually, the kmalloc caches are cache_line_size() aligned, except when
- * DEBUG and FORCED_DEBUG are enabled, then they are BYTES_PER_WORD aligned.
- * Some archs want to perform DMA into kmalloc caches and need a guaranteed
- * alignment larger than the alignment of a 64-bit integer.
- * ARCH_KMALLOC_MINALIGN allows that.
- * Note that increasing this value may disable some debug features.
- */
-#ifdef ARCH_DMA_MINALIGN
-#define ARCH_KMALLOC_MINALIGN ARCH_DMA_MINALIGN
-#else
-#define ARCH_KMALLOC_MINALIGN __alignof__(unsigned long long)
-#endif
-
-#ifndef ARCH_SLAB_MINALIGN
-/*
- * Enforce a minimum alignment for all caches.
- * Intended for archs that get misalignment faults even for BYTES_PER_WORD
- * aligned buffers. Includes ARCH_KMALLOC_MINALIGN.
- * If possible: Do not enable this flag for CONFIG_DEBUG_SLAB, it disables
- * some debug features.
- */
-#define ARCH_SLAB_MINALIGN 0
-#endif
-
-/*
  * struct kmem_cache
  *
  * manages a cache.

include/linux/slob_def.h

···
 #ifndef __LINUX_SLOB_DEF_H
 #define __LINUX_SLOB_DEF_H
 
-#ifdef ARCH_DMA_MINALIGN
-#define ARCH_KMALLOC_MINALIGN ARCH_DMA_MINALIGN
-#else
-#define ARCH_KMALLOC_MINALIGN __alignof__(unsigned long)
-#endif
-
-#ifndef ARCH_SLAB_MINALIGN
-#define ARCH_SLAB_MINALIGN __alignof__(unsigned long)
-#endif
-
 void *kmem_cache_alloc_node(struct kmem_cache *, gfp_t flags, int node);
 
 static __always_inline void *kmem_cache_alloc(struct kmem_cache *cachep,

include/linux/slub_def.h

···
 
 #define KMALLOC_SHIFT_LOW ilog2(KMALLOC_MIN_SIZE)
 
-#ifdef ARCH_DMA_MINALIGN
-#define ARCH_KMALLOC_MINALIGN ARCH_DMA_MINALIGN
-#else
-#define ARCH_KMALLOC_MINALIGN __alignof__(unsigned long long)
-#endif
-
-#ifndef ARCH_SLAB_MINALIGN
-#define ARCH_SLAB_MINALIGN __alignof__(unsigned long long)
-#endif
-
 /*
  * Maximum kmalloc object size handled by SLUB. Larger object allocations
  * are passed through to the page allocator. The page allocator "fastpath"