[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>

3 files changed, 32 insertions, 8 deletions

diff --git a/arch/ia64/mm/discontig.c b/arch/ia64/mm/discontig.c
index 83153ac18795..9153465d7fcc 100644
--- a/arch/ia64/mm/discontig.c
+++ b/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();
+}
diff --git a/include/asm-ia64/nodedata.h b/include/asm-ia64/nodedata.h
index a140310bf84d..2fb337b0e9b7 100644
--- a/include/asm-ia64/nodedata.h
+++ b/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 */
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 569b1f6c27d1..9b6260007e5e 100644
--- a/include/linux/memory_hotplug.h
+++ b/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 */