[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 <y-goto@jp.fujitsu.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/ia64/mm/discontig.c

@@ -308,6 +308,17 @@ static void __init reserve_pernode_space(void)
 	}
 }
 
+static void __meminit scatter_node_data(void)
+{
+	pg_data_t **dst;
+	int node;
+
+	for_each_online_node(node) {
+		dst = LOCAL_DATA_ADDR(pgdat_list[node])->pg_data_ptrs;
+		memcpy(dst, pgdat_list, sizeof(pgdat_list));
+	}
+}
+
 /**
  * initialize_pernode_data - fixup per-cpu & per-node pointers
  *
@@ -320,11 +331,8 @@ static void __init initialize_pernode_data(void)
 {
 	int cpu, node;
 
-	/* Copy the pg_data_t list to each node and init the node field */
-	for_each_online_node(node) {
-		memcpy(mem_data[node].node_data->pg_data_ptrs, pgdat_list,
-		       sizeof(pgdat_list));
-	}
+	scatter_node_data();
+
 #ifdef CONFIG_SMP
 	/* Set the node_data pointer for each per-cpu struct */
 	for (cpu = 0; cpu < NR_CPUS; cpu++) {
@@ -783,3 +791,9 @@ void __init paging_init(void)
 
 	zero_page_memmap_ptr = virt_to_page(ia64_imva(empty_zero_page));
 }
+
+void arch_refresh_nodedata(int update_node, pg_data_t *update_pgdat)
+{
+	pgdat_list[update_node] = update_pgdat;
+	scatter_node_data();
+}

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 */

include/linux/memory_hotplug.h

@@ -91,9 +91,7 @@ static inline pg_data_t *arch_alloc_nodedata(int nid)
 static inline void arch_free_nodedata(pg_data_t *pgdat)
 {
 }
-static inline void arch_refresh_nodedata(int nid, pg_data_t *pgdat)
-{
-}
+extern void arch_refresh_nodedata(int nid, pg_data_t *pgdat);
 
 #else /* CONFIG_HAVE_ARCH_NODEDATA_EXTENSION */