mm/slab.c: cleanup is_debug_pagealloc_cache()

Remove the if statement to increase code readability.
Also make the function inline, per David.
Signed-off-by: lvqian <lvqian@nfschina.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

mm/slab.c

@@ -1410,13 +1410,10 @@ static void kmem_rcu_free(struct rcu_head *head)
 }
 
 #if DEBUG
-static bool is_debug_pagealloc_cache(struct kmem_cache *cachep)
+static inline bool is_debug_pagealloc_cache(struct kmem_cache *cachep)
 {
-	if (debug_pagealloc_enabled_static() && OFF_SLAB(cachep) &&
-		(cachep->size % PAGE_SIZE) == 0)
-		return true;
-
-	return false;
+	return debug_pagealloc_enabled_static() && OFF_SLAB(cachep) &&
+			((cachep->size % PAGE_SIZE) == 0);
 }
 
 #ifdef CONFIG_DEBUG_PAGEALLOC