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authorChristoph Lameter <cl@linux.com>2011-06-23 09:36:12 -0500
committerPekka Enberg <penberg@kernel.org>2011-07-07 21:04:12 +0300
commit90810645f78f894acfb04b3768e8a7d45f2b303a (patch)
tree114dce690d2f74cdb347e68d1386c605cdeee093
parent3192b920bf7d0c528ab54e7d3689f44055316a37 (diff)
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>
-rw-r--r--include/linux/slab.h10
1 files changed, 10 insertions, 0 deletions
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 646a639a4aae..573c809c33d9 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