[Patch:BUG] oversight of copy pgdat array on each node for ia64's memory hotplug.

Yasunori Goto
2006-07-04T05:51:04Z

Hello.

I found a bug in memory hot-add code for ia64.

IA64's code has copies of pgdat's array on each node to reduce memory
access over crossing node. This array is used by NODE_DATA() macro.
When new node is hot-added, this pgdat's array should be updated and
copied on new node too.

However, I used for_each_online_node() in scatter_node_data() to copy
it. This meant its array is not copied on new node.
Because initialization of structures for new node was halfway,
so online_node_map couldn't be set at this time.

To copy arrays on new node, I changed it to check value of
pgdat_list[] which is source array of copies.
I tested this patch with my Memory Hotadd emulation on Tiger4.
This patch is for 2.6.17-git20.

Please apply.

Signed-off-by: Yasunori Goto <y-goto@jp.fujitsu.com>

---

arch/ia64/mm/discontig.c | 17 +++++++++++++----
1 files changed, 13 insertions(+), 4 deletions(-)

Index: pgdattest1/arch/ia64/mm/discontig.c
=================================--- pgdattest1.orig/arch/ia64/mm/discontig.c 2006-07-03 15:41:30.000000000 +0900
+++ pgdattest1/arch/ia64/mm/discontig.c 2006-07-03 15:44:48.000000000 +0900
@@ -313,10 +313,19 @@ static void __meminit scatter_node_data(
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));
- }
+ /*
+ * for_each_online_map() can't be used at here.
+ * node_online_map is not set for hot-added node at this time,
+ * because here is halfway of initilization of new node's structure.
+ * If for_each_online_node() is used, new node's pg_data_ptrs will
+ * be not initialized. Insted of using it, pgdat_list[] is checked.
+ */
+ for_each_node(node)
+ if (pgdat_list[node]){
+ dst = LOCAL_DATA_ADDR(pgdat_list[node])->pg_data_ptrs;
+ memcpy(dst, pgdat_list, sizeof(pgdat_list));
+ }
+
}

/**

--
Yasunori Goto