slab: Return NULL for oversized allocations

The inline path seems to have changed the SLAB behavior for very large
kmalloc allocations with  commit e336601 ("slab: Use common
kmalloc_index/kmalloc_size functions"). This patch restores the old
behavior but also adds diagnostics so that we can figure where in the
code these large allocations occur.

Reported-and-tested-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Christoph Lameter <cl@linux.com>
Link: http://lkml.kernel.org/r/201305040348.CIF81716.OStQOHFJMFLOVF@I-love.SAKURA.ne.jp
[ penberg@kernel.org: use WARN_ON_ONCE ]
Signed-off-by: Pekka Enberg <penberg@kernel.org>

include/linux/slab_def.h

@@ -126,6 +126,9 @@ static __always_inline void *kmalloc(size_t size, gfp_t flags)
 		if (!size)
 			return ZERO_SIZE_PTR;
 
+		if (WARN_ON_ONCE(size > KMALLOC_MAX_SIZE))
+			return NULL;
+
 		i = kmalloc_index(size);
 
 #ifdef CONFIG_ZONE_DMA
@@ -172,6 +175,9 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
 		if (!size)
 			return ZERO_SIZE_PTR;
 
+		if (WARN_ON_ONCE(size > KMALLOC_MAX_SIZE))
+			return NULL;
+
 		i = kmalloc_index(size);
 
 #ifdef CONFIG_ZONE_DMA

mm/slab_common.c

@@ -373,6 +373,9 @@ struct kmem_cache *kmalloc_slab(size_t size, gfp_t flags)
 {
 	int index;
 
+	if (WARN_ON_ONCE(size > KMALLOC_MAX_SIZE))
+		return NULL;
+
 	if (size <= 192) {
 		if (!size)
 			return ZERO_SIZE_PTR;