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authorWei Yang <richard.weiyang@gmail.com>2018-11-30 14:09:07 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2018-11-30 14:56:14 -0800
commit8f416836c0d50b198cad1225132e5abebf8980dc (patch)
tree8b5d9c7ecc273545776d68e4e7c8576c46c84c80 /mm
parentc1cb20d43728aa9b5393bd8d489bc85c142949b2 (diff)
mm/page_alloc.c: fix calculation of pgdat->nr_zones
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). Michal said: "Having an incorrect nr_zones might result in all sorts of problems which would be quite hard to debug (e.g. reclaim not considering the movable zone). I do not expect many users would suffer from this it but still this is trivial and obviously right thing to do so backporting to the stable tree shouldn't be harmful (last famous words)" Link: http://lkml.kernel.org/r/20181117022022.9956-1-richard.weiyang@gmail.com Fixes: f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded memory to zones until online") Signed-off-by: Wei Yang <richard.weiyang@gmail.com> Acked-by: Michal Hocko <mhocko@suse.com> Reviewed-by: Oscar Salvador <osalvador@suse.de> Cc: Anshuman Khandual <anshuman.khandual@arm.com> Cc: Dave Hansen <dave.hansen@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/page_alloc.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6847177dc4a1..2ec9cc407216 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5813,8 +5813,10 @@ 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;