[PATCH] __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>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

mm/slab.c

@@ -2907,8 +2907,7 @@ void *__kmalloc(size_t size, unsigned int __nocast flags)
 	 * 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);