In preparation for supporting a kmalloc() minimum alignment smaller than
the arch DMA alignment, decouple the two definitions. This requires that
either the kmalloc() caches are aligned to a (run-time) cache-line size
or the DMA API bounces unaligned kmalloc() allocations. Subsequent
patches will implement both options.
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.
Architectures opting in to a smaller ARCH_KMALLOC_MINALIGN will need to
define its value in the arch headers.
Since ARCH_DMA_MINALIGN is now always defined, adjust the #ifdef in
dma_get_cache_alignment() so that there is no change for architectures
not requiring a minimum DMA alignment.
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Robin Murphy <robin.murphy@xxxxxxx>
---
include/linux/dma-mapping.h | 2 +-
include/linux/slab.h | 16 +++++++++++++---
2 files changed, 14 insertions(+), 4 deletions(-)
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 0ee20b764000..3288a1339271 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -545,7 +545,7 @@ static inline int dma_set_min_align_mask(struct device *dev,
static inline int dma_get_cache_alignment(void)
{
-#ifdef ARCH_DMA_MINALIGN
+#ifdef ARCH_HAS_DMA_MINALIGN
return ARCH_DMA_MINALIGN;
#endif
return 1;
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 6b3e155b70bf..3f76e7c53ada 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -235,14 +235,24 @@ void kmem_dump_obj(void *object);
* alignment larger than the alignment of a 64-bit integer.
* Setting ARCH_DMA_MINALIGN in arch headers allows that.
*/
-#if defined(ARCH_DMA_MINALIGN) && ARCH_DMA_MINALIGN > 8
+#ifdef ARCH_DMA_MINALIGN
+#define ARCH_HAS_DMA_MINALIGN
+#if 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)
+#endif
#else
+#define ARCH_DMA_MINALIGN __alignof__(unsigned long long)
+#endif
+
+#ifndef ARCH_KMALLOC_MINALIGN
#define ARCH_KMALLOC_MINALIGN __alignof__(unsigned long long)
#endif
+#if ARCH_KMALLOC_MINALIGN > 8
+#define KMALLOC_MIN_SIZE ARCH_KMALLOC_MINALIGN
+#define KMALLOC_SHIFT_LOW ilog2(KMALLOC_MIN_SIZE)
+#endif
+
/*
* Setting ARCH_SLAB_MINALIGN in arch headers allows a different alignment.
* Intended for arches that get misalignment faults even for 64 bit integer
