slab allocators: Provide generic description of alignment defines
Provide description for alignment defines.
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 646a639..573c809 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -133,12 +133,22 @@
#define KMALLOC_MAX_SIZE (1UL << KMALLOC_SHIFT_HIGH)
#define KMALLOC_MAX_ORDER (KMALLOC_SHIFT_HIGH - PAGE_SHIFT)
+/*
+ * 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.
+ */
#ifdef ARCH_DMA_MINALIGN
#define ARCH_KMALLOC_MINALIGN ARCH_DMA_MINALIGN
#else
#define ARCH_KMALLOC_MINALIGN __alignof__(unsigned long long)
#endif
+/*
+ * Setting ARCH_SLAB_MINALIGN in arch headers allows a different alignment.
+ * Intended for arches that get misalignment faults even for 64 bit integer
+ * aligned buffers.
+ */
#ifndef ARCH_SLAB_MINALIGN
#define ARCH_SLAB_MINALIGN __alignof__(unsigned long long)
#endif