On 02/05/2013 09:36 AM, Christoph Lameter wrote: > 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. Tested-by: Stephen Warren <swarren@xxxxxxxxxx> > +/* > + * 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 I might be tempted to drop that #define of KMALLOC_MIN_SIZE ... > +#define KMALLOC_SHIFT_LOW ilog2(ARCH_DMA_MINALIGN) > +#else > +#define ARCH_KMALLOC_MINALIGN __alignof__(unsigned long long) > +#endif > +#ifndef KMALLOC_MIN_SIZE > #define KMALLOC_MIN_SIZE (1 << KMALLOC_SHIFT_LOW) > #endif ... and simply drop the ifdef around that #define instead. That way, KMALLOC_MIN_SIZE is always defined in one place, and derived from KMALLOC_SHIFT_LOW; the logic will just set KMALLOC_SHIFT_LOW based on the various conditions. This seems a little safer to me; fewer conditions and less code to update if anything changes. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>