slub, hotplug: ignore unrelated node's hot-adding and hot-removing

SLUB only focuses on the nodes which have normal memory and it ignores the
other node's hot-adding and hot-removing.

Aka: if some memory of a node which has no onlined memory is online, but
this new memory onlined is not normal memory (for example, highmem), we
should not allocate kmem_cache_node for SLUB.

And if the last normal memory is offlined, but the node still has memory,
we should remove kmem_cache_node for that node.  (The current code delays
it when all of the memory is offlined)

So we only do something when marg->status_change_nid_normal > 0.
marg->status_change_nid is not suitable here.

The same problem doesn't exist in SLAB, because SLAB allocates kmem_list3
for every node even the node don't have normal memory, SLAB tolerates
kmem_list3 on alien nodes.  SLUB only focuses on the nodes which have
normal memory, it don't tolerate alien kmem_cache_node.  The patch makes
SLUB become self-compatible and avoids WARNs and BUGs in rare conditions.

Signed-off-by: Lai Jiangshan <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: Yasuaki Ishimatsu <[email protected]>
Cc: Rob Landley <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Jiang Liu <[email protected]>
Cc: Kay Sievers <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Wen Congyang <[email protected]>
Acked-by: Christoph Lameter <[email protected]>
Cc: Pekka Enberg <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/slub.c

@@ -3573,7 +3573,7 @@ static void slab_mem_offline_callback(void *arg)
 	struct memory_notify *marg = arg;
 	int offline_node;
 
-	offline_node = marg->status_change_nid;
+	offline_node = marg->status_change_nid_normal;
 
 	/*
 	 * If the node still has available memory. we need kmem_cache_node
@@ -3606,7 +3606,7 @@ static int slab_mem_going_online_callback(void *arg)
 	struct kmem_cache_node *n;
 	struct kmem_cache *s;
 	struct memory_notify *marg = arg;
-	int nid = marg->status_change_nid;
+	int nid = marg->status_change_nid_normal;
 	int ret = 0;
 
 	/*