[PATCH 01/10] mm/slab: Decouple ARCH_KMALLOC_MINALIGN from ARCH_DMA_MINALIGN

[Catalin Marinas]

In preparation for supporting a dynamic kmalloc() minimum alignment,
allow architectures to define ARCH_KMALLOC_MINALIGN independently of
ARCH_DMA_MINALIGN. In addition, always define ARCH_DMA_MINALIGN even if
an architecture does not override it.

After this patch, ARCH_DMA_MINALIGN is expected to be used in static
alignment annotations and defined by an architecture to be the maximum
alignment for all supported configurations/SoCs in a single Image.
ARCH_KMALLOC_MINALIGN, if different, is the minimum alignment guaranteed
by kmalloc().

Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
 include/linux/slab.h | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 373b3ef99f4e..d58211bdeceb 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -187,17 +187,30 @@ bool kmem_valid_obj(void *object);
 void kmem_dump_obj(void *object);
 #endif
 
+/*
+ * slob does not support independent control of ARCH_KMALLOC_MINALIGN and
+ * ARCH_DMA_MINALIGN.
+ */
+#ifdef CONFIG_SLOB
+#undef ARCH_KMALLOC_MINALIGN
+#endif
+
 /*
  * Some archs want to perform DMA into kmalloc caches and need a guaranteed
  * alignment larger than the alignment of a 64-bit integer.
- * Setting ARCH_KMALLOC_MINALIGN in arch headers allows that.
+ * Setting ARCH_DMA_MINALIGN in arch headers allows that.
  */
-#if defined(ARCH_DMA_MINALIGN) && ARCH_DMA_MINALIGN > 8
+#ifndef ARCH_DMA_MINALIGN
+#define ARCH_DMA_MINALIGN __alignof__(unsigned long long)
+#elif ARCH_DMA_MINALIGN > 8 && !defined(ARCH_KMALLOC_MINALIGN)
 #define ARCH_KMALLOC_MINALIGN ARCH_DMA_MINALIGN
-#define KMALLOC_MIN_SIZE ARCH_DMA_MINALIGN
-#define KMALLOC_SHIFT_LOW ilog2(ARCH_DMA_MINALIGN)
-#else
+#endif
+
+#ifndef ARCH_KMALLOC_MINALIGN
 #define ARCH_KMALLOC_MINALIGN __alignof__(unsigned long long)
+#else
+#define KMALLOC_MIN_SIZE ARCH_KMALLOC_MINALIGN
+#define KMALLOC_SHIFT_LOW ilog2(KMALLOC_MIN_SIZE)
 #endif
 
 /*