Function init_currently_empty_zone() will adjust pgdat->nr_zones and set
it to 'zone_idx(zone) + 1' unconditionally. This is correct in the
normal case, while not exact in hot-plug situation.
This function is used in two places:
* free_area_init_core()
* move_pfn_range_to_zone()
In the first case, we are sure zone index increase monotonically. While
in the second one, this is under users control.
One way to reproduce this is:
----------------------------
1. create a virtual machine with empty node1
-m 4G,slots=32,maxmem=32G \
-smp 4,maxcpus=8 \
-numa node,nodeid=0,mem=4G,cpus=0-3 \
-numa node,nodeid=1,mem=0G,cpus=4-7
2. hot-add cpu 3-7
cpu-add [3-7]
2. hot-add memory to nod1
object_add memory-backend-ram,id=ram0,size=1G
device_add pc-dimm,id=dimm0,memdev=ram0,node=1
3. online memory with following order
echo online_movable > memory47/state
echo online > memory40/state
After this, node1 will have its nr_zones equals to (ZONE_NORMAL + 1)
instead of (ZONE_MOVABLE + 1).
Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
---
mm/page_alloc.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5b7cd20dbaef..2d3c54201255 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5823,8 +5823,10 @@ void __meminit init_currently_empty_zone(struct zone *zone,
unsigned long size)
{
struct pglist_data *pgdat = zone->zone_pgdat;
+ int zone_idx = zone_idx(zone) + 1;
- pgdat->nr_zones = zone_idx(zone) + 1;
+ if (zone_idx > pgdat->nr_zones)
+ pgdat->nr_zones = zone_idx;
zone->zone_start_pfn = zone_start_pfn;
--
2.15.1
