[PART1 Patch 3/3] memory_hotplug: ensure every online node has NORMAL memory

[Wen Congyang <wency@cn.fujitsu.com>]

From: Lai Jiangshan <laijs@cn.fujitsu.com>

Old  memory hotplug code and new online/movable may cause a online node
don't have any normal memory, but memory-management acts bad when we have
nodes which is online but don't have any normal memory.
Example: it may cause a bound task fail on all kernel allocation and
cause the task can't create task or create other kernel object.

So we disable non-normal-memory-node here, we will enable it
when we prepared.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
 mm/memory_hotplug.c | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index e6ec8c2..b557218 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -589,6 +589,12 @@ static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages,
 	return 0;
 }
 
+/* ensure every online node has NORMAL memory */
+static bool can_online_high_movable(struct zone *zone)
+{
+	return node_state(zone_to_nid(zone), N_NORMAL_MEMORY);
+}
+
 /* check which state of node_states will be changed when online memory */
 static void node_states_check_changes_online(unsigned long nr_pages,
 	struct zone *zone, struct memory_notify *arg)
@@ -654,6 +660,12 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
 	 */
 	zone = page_zone(pfn_to_page(pfn));
 
+	if ((zone_idx(zone) > ZONE_NORMAL || online_type == ONLINE_MOVABLE) &&
+	    !can_online_high_movable(zone)) {
+		unlock_memory_hotplug();
+		return -1;
+	}
+
 	if (online_type == ONLINE_KERNEL && zone_idx(zone) == ZONE_MOVABLE) {
 		if (move_pfn_range_left(zone - 1, zone, pfn, pfn + nr_pages)) {
 			unlock_memory_hotplug();
@@ -1058,6 +1070,30 @@ check_pages_isolated(unsigned long start_pfn, unsigned long end_pfn)
 	return offlined;
 }
 
+/* ensure the node has NORMAL memory if it is still online */
+static bool can_offline_normal(struct zone *zone, unsigned long nr_pages)
+{
+	struct pglist_data *pgdat = zone->zone_pgdat;
+	unsigned long present_pages = 0;
+	enum zone_type zt;
+
+	for (zt = 0; zt <= ZONE_NORMAL; zt++)
+		present_pages += pgdat->node_zones[zt].present_pages;
+
+	if (present_pages > nr_pages)
+		return true;
+
+	present_pages = 0;
+	for (; zt <= ZONE_MOVABLE; zt++)
+		present_pages += pgdat->node_zones[zt].present_pages;
+
+	/*
+	 * we can't offline the last normal memory until all
+	 * higher memory is offlined.
+	 */
+	return present_pages == 0;
+}
+
 /* check which state of node_states will be changed when offline memory */
 static void node_states_check_changes_offline(unsigned long nr_pages,
 		struct zone *zone, struct memory_notify *arg)
@@ -1145,6 +1181,10 @@ static int __ref __offline_pages(unsigned long start_pfn,
 	node = zone_to_nid(zone);
 	nr_pages = end_pfn - start_pfn;
 
+	ret = -EINVAL;
+	if (zone_idx(zone) <= ZONE_NORMAL && !can_offline_normal(zone, nr_pages))
+		goto out;
+
 	/* set above range as isolated */
 	ret = start_isolate_page_range(start_pfn, end_pfn, MIGRATE_MOVABLE);
 	if (ret)
-- 
1.8.0

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