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SubjectRe: next-20130204 - bisected slab problem to "slab: Common constants for kmalloc boundaries"
OK I was able to reproduce it by setting ARCH_DMA_MINALIGN in slab.h. This
patch fixes it here:


Subject: slab: Handle ARCH_DMA_MINALIGN correctly

A fixed KMALLOC_SHIFT_LOW does not work for arches with higher alignment
requirements.

Determine KMALLOC_SHIFT_LOW from ARCH_DMA_MINALIGN instead.

Signed-off-by: Christoph Lameter <cl@linux.com>

Index: linux/include/linux/slab.h
===================================================================
--- linux.orig/include/linux/slab.h 2013-02-05 10:30:53.917724146 -0600
+++ linux/include/linux/slab.h 2013-02-05 10:31:01.181836707 -0600
@@ -133,6 +133,19 @@ void kfree(const void *);
void kzfree(const void *);
size_t ksize(const void *);

+/*
+ * 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.
+ */
+#if defined(ARCH_DMA_MINALIGN) && ARCH_DMA_MINALIGN > 8
+#define ARCH_KMALLOC_MINALIGN ARCH_DMA_MINALIGN
+#define KMALLOC_MIN_SIZE ARCH_DMA_MINALIGN
+#define KMALLOC_SHIFT_LOW ilog2(ARCH_DMA_MINALIGN)
+#else
+#define ARCH_KMALLOC_MINALIGN __alignof__(unsigned long long)
+#endif
+
#ifdef CONFIG_SLOB
/*
* Common fields provided in kmem_cache by all slab allocators
@@ -179,7 +192,9 @@ struct kmem_cache {
#define KMALLOC_SHIFT_HIGH ((MAX_ORDER + PAGE_SHIFT - 1) <= 25 ? \
(MAX_ORDER + PAGE_SHIFT - 1) : 25)
#define KMALLOC_SHIFT_MAX KMALLOC_SHIFT_HIGH
+#ifndef KMALLOC_SHIFT_LOW
#define KMALLOC_SHIFT_LOW 5
+#endif
#else
/*
* SLUB allocates up to order 2 pages directly and otherwise
@@ -187,8 +202,10 @@ struct kmem_cache {
*/
#define KMALLOC_SHIFT_HIGH (PAGE_SHIFT + 1)
#define KMALLOC_SHIFT_MAX (MAX_ORDER + PAGE_SHIFT)
+#ifndef KMALLOC_SHIFT_LOW
#define KMALLOC_SHIFT_LOW 3
#endif
+#endif

/* Maximum allocatable size */
#define KMALLOC_MAX_SIZE (1UL << KMALLOC_SHIFT_MAX)
@@ -200,9 +217,7 @@ struct kmem_cache {
/*
* Kmalloc subsystem.
*/
-#if defined(ARCH_DMA_MINALIGN) && ARCH_DMA_MINALIGN > 8
-#define KMALLOC_MIN_SIZE ARCH_DMA_MINALIGN
-#else
+#ifndef KMALLOC_MIN_SIZE
#define KMALLOC_MIN_SIZE (1 << KMALLOC_SHIFT_LOW)
#endif

@@ -285,17 +300,6 @@ static __always_inline int kmalloc_size(
#endif /* !CONFIG_SLOB */

/*
- * 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.

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