mm/slub.c: update comments

Slub doesn't use PG_active and PG_error anymore.

Link: http://lkml.kernel.org/r/20191007222023.162256-1-yuzhao@google.com
Signed-off-by: Yu Zhao <yuzhao@google.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/slub.c

@@ -93,9 +93,7 @@
  * minimal so we rely on the page allocators per cpu caches for
  * fast frees and allocs.
  *
- * Overloading of page flags that are otherwise used for LRU management.
- *
- * PageActive 		The slab is frozen and exempt from list processing.
+ * page->frozen		The slab is frozen and exempt from list processing.
  * 			This means that the slab is dedicated to a purpose
  * 			such as satisfying allocations for a specific
  * 			processor. Objects may be freed in the slab while
@@ -111,7 +109,7 @@
  * 			free objects in addition to the regular freelist
  * 			that requires the slab lock.
  *
- * PageError		Slab requires special handling due to debug
+ * SLAB_DEBUG_FLAGS	Slab requires special handling due to debug
  * 			options set. This moves	slab handling out of
  * 			the fast path and disables lockless freelists.
  */