[PATCH] pgdat allocation and update for ia64 of memory hotplug: update pgdat address array

This is to refresh node_data[] array for ia64.  As I mentioned previous
patches, ia64 has copies of information of pgdat address array on each node as
per node data.

At v2 of node_add, this function used stop_machine_run() to update them.  (I
wished that they were copied safety as much as possible.) But, in this patch,
this arrays are just copied simply, and set node_online_map bit after
completion of pgdat initialization.

So, kernel must touch NODE_DATA() macro after checking node_online_map().
(Current code has already done it.) This is more simple way for just
hot-add.....

Note : It will be problem when hot-remove will occur,
       because, even if online_map bit is set, kernel may
       touch NODE_DATA() due to race condition. :-(

Signed-off-by: Yasunori Goto <[email protected]>
Cc: "Luck, Tony" <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

include/asm-ia64/nodedata.h

@@ -46,6 +46,18 @@ struct ia64_node_data {
  */
 #define NODE_DATA(nid)		(local_node_data->pg_data_ptrs[nid])
 
+/*
+ * LOCAL_DATA_ADDR - This is to calculate the address of other node's
+ *		     "local_node_data" at hot-plug phase. The local_node_data
+ *		     is pointed by per_cpu_page. Kernel usually use it for
+ *		     just executing cpu. However, when new node is hot-added,
+ *		     the addresses of local data for other nodes are necessary
+ *		     to update all of them.
+ */
+#define LOCAL_DATA_ADDR(pgdat)  			\
+	((struct ia64_node_data *)((u64)(pgdat) + 	\
+				   L1_CACHE_ALIGN(sizeof(struct pglist_data))))
+
 #endif /* CONFIG_NUMA */
 
 #endif /* _ASM_IA64_NODEDATA_H */