From: Mark Fortescue <mark@mtfhpc.demon.co.uk>

Verious alignment fixes in the SLAB alocator that increased the size
of the RedZone words failed to ensure that RedZone word 2 is aligned
on a 64bit boundary. This has resulted in random invalid instruction
occourances on Sparc32 (sun4c).
By increasing the size of the User Word (BYTES_PER_WORD) to 64bits
seams to ensure that correct alignment is maintained but assumes that:
   sizeof (void *) <= sizeof (unsigned dlong long) 

Signed-off-by: Mark Fortescue <mark@mtfhpc.demon.co.uk>
---
Alternative solutions would involve correcting the size caculations on
lines 2175 to 2275 and may also involve additional changes to the
calculations to get a pointer to the RedZone Word 2.
--- linux-2.6/mm/slab.c	2007-07-03 17:35:07.000000000 +0100
+++ linux-test/mm/slab.c	2007-07-03 19:05:19.000000000 +0100
@@ -136,7 +136,8 @@
 #endif
 
 /* Shouldn't this be in a header file somewhere? */
-#define	BYTES_PER_WORD		sizeof(void *)
+/* Fix alignment of redzone2. Assumes sizeof (void*) <= sizeof (unsigned long long) */
+#define	BYTES_PER_WORD		sizeof(unsigned long long)
 
 #ifndef cache_line_size
 #define cache_line_size()	L1_CACHE_BYTES
@@ -538,7 +539,7 @@ static unsigned long long *dbg_redzone1(
 {
 	BUG_ON(!(cachep->flags & SLAB_RED_ZONE));
 	return (unsigned long long*) (objp + obj_offset(cachep) -
-				      sizeof(unsigned long long));
+				      BYTES_PER_WORD);
 }
 
 static unsigned long long *dbg_redzone2(struct kmem_cache *cachep, void *objp)
@@ -546,10 +547,9 @@ static unsigned long long *dbg_redzone2(
 	BUG_ON(!(cachep->flags & SLAB_RED_ZONE));
 	if (cachep->flags & SLAB_STORE_USER)
 		return (unsigned long long *)(objp + cachep->buffer_size -
-					      sizeof(unsigned long long) -
-					      BYTES_PER_WORD);
+					      2 * BYTES_PER_WORD);
 	return (unsigned long long *) (objp + cachep->buffer_size -
-				       sizeof(unsigned long long));
+				       BYTES_PER_WORD);
 }
 
 static void **dbg_userword(struct kmem_cache *cachep, void *objp)
@@ -2256,8 +2256,8 @@ kmem_cache_create (const char *name, siz
 	 */
 	if (flags & SLAB_RED_ZONE) {
 		/* add space for red zone words */
-		cachep->obj_offset += sizeof(unsigned long long);
-		size += 2 * sizeof(unsigned long long);
+		cachep->obj_offset += BYTES_PER_WORD;
+		size += 2 * BYTES_PER_WORD;
 	}
 	if (flags & SLAB_STORE_USER) {
 		/* user store requires one word storage behind the end of