At 12/26/2012 11:55 AM, Kamezawa Hiroyuki Wrote:

(2012/12/24 21:09), Tang Chen wrote:

quoted

From: Wen Congyang <redacted>

We call hotadd_new_pgdat() to allocate memory to store node_data. So we
should free it when removing a node.

Signed-off-by: Wen Congyang <redacted>

I'm sorry but is it safe to remove pgdat ? All zone cache and zonelists are
properly cleared/rebuilded in synchronous way ? and No threads are visinting
zone in vmscan.c ?

We have rebuilt zonelists when a zone has no memory after offlining some pages.

Thanks
Wen Congyang

Thanks,
-Kame

quoted

---
  mm/memory_hotplug.c |   20 +++++++++++++++++++-
  1 files changed, 19 insertions(+), 1 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index f8a1d2f..447fa24 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c

@@ -1680,9 +1680,12 @@ static int check_cpu_on_node(void *data)
  /* offline the node if all memory sections of this node are removed */
  static void try_offline_node(int nid)
  {
+	pg_data_t *pgdat = NODE_DATA(nid);
  	unsigned long start_pfn = NODE_DATA(nid)->node_start_pfn;
-	unsigned long end_pfn = start_pfn + NODE_DATA(nid)->node_spanned_pages;
+	unsigned long end_pfn = start_pfn + pgdat->node_spanned_pages;
  	unsigned long pfn;
+	struct page *pgdat_page = virt_to_page(pgdat);
+	int i;
  
  	for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
  		unsigned long section_nr = pfn_to_section_nr(pfn);

@@ -1709,6 +1712,21 @@ static void try_offline_node(int nid)
  	 */
  	node_set_offline(nid);
  	unregister_one_node(nid);
+
+	if (!PageSlab(pgdat_page) && !PageCompound(pgdat_page))
+		/* node data is allocated from boot memory */
+		return;
+
+	/* free waittable in each zone */
+	for (i = 0; i < MAX_NR_ZONES; i++) {
+		struct zone *zone = pgdat->node_zones + i;
+
+		if (zone->wait_table)
+			vfree(zone->wait_table);
+	}
+
+	arch_refresh_nodedata(nid, NULL);
+	arch_free_nodedata(pgdat);
  }
  
  int __ref remove_memory(int nid, u64 start, u64 size)