__kmalloc: Generate BUG if size requested is too large.

I had an issue on ia64 where I got a bug in kernel/workqueue because kzalloc
returned a NULL pointer due to the task structure getting too big for the slab
allocator. Usually these cases are caught by the kmalloc macro in include/linux/slab.h.
Compilation will fail if a too big value is passed to kmalloc.

However, kzalloc uses __kmalloc which has no check for that. This patch makes __kmalloc
bug if a too large entity is requested.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.14-rc2/mm/slab.c
===================================================================
--- linux-2.6.14-rc2.orig/mm/slab.c	2005-09-22 11:21:07.000000000 -0700
+++ linux-2.6.14-rc2/mm/slab.c	2005-09-22 11:58:45.000000000 -0700
@@ -2906,8 +2906,7 @@ void *__kmalloc(size_t size, unsigned in
 	 * functions.
 	 */
 	cachep = __find_general_cachep(size, flags);
-	if (unlikely(cachep == NULL))
-		return NULL;
+	BUG_ON(!cachep);		/* Allocation size too large for kmalloc */
 	return __cache_alloc(cachep, flags);
 }
 EXPORT_SYMBOL(__kmalloc);