mm/slab: use more appropriate condition check for debug_pagealloc

debug_pagealloc debugging is related to SLAB_POISON flag rather than
FORCED_DEBUG option, although FORCED_DEBUG option will enable
SLAB_POISON.  Fix it.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: JoonsooKim

mm/slab.c

@@ -2180,22 +2180,20 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
 		else
 			size += BYTES_PER_WORD;
 	}
-#if FORCED_DEBUG && defined(CONFIG_DEBUG_PAGEALLOC)
 	/*
 	 * To activate debug pagealloc, off-slab management is necessary
 	 * requirement. In early phase of initialization, small sized slab
 	 * doesn't get initialized so it would not be possible. So, we need
 	 * to check size >= 256. It guarantees that all necessary small
 	 * sized slab is initialized in current slab initialization sequence.
 	 */
-	if (debug_pagealloc_enabled() &&
+	if (debug_pagealloc_enabled() && (flags & SLAB_POISON) &&
 		!slab_early_init && size >= kmalloc_size(INDEX_NODE) &&
 		size >= 256 && cachep->object_size > cache_line_size() &&
 		ALIGN(size, cachep->align) < PAGE_SIZE) {
 		cachep->obj_offset += PAGE_SIZE - ALIGN(size, cachep->align);
 		size = PAGE_SIZE;
 	}
-#endif
 #endif
 
 	/*