From: Christoph Lameter <cl@linux.com>
Date: Thu, 23 Jun 2011 14:36:12 +0000 (-0500)
Subject: slab allocators: Provide generic description of alignment defines
X-Git-Url: https://openfabrics.org/gitweb/?a=commitdiff_plain;h=90810645f78f894acfb04b3768e8a7d45f2b303a;p=~shefty%2Frdma-dev.git

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 646a639a4aa..573c809c33d 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -133,12 +133,22 @@ unsigned int kmem_cache_size(struct kmem_cache *);
 #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