[PATCH 2/3] mm/memory_hotplug: harden try_offline_node against bogus nid

From: Jia He
Date: Sun Jul 05 2020 - 21:20:14 EST


When testing the remove_memory path of dax pmem, there will be a panic with
call trace:
try_remove_memory+0x84/0x170
remove_memory+0x38/0x58
dev_dax_kmem_remove+0x3c/0x84 [kmem]
device_release_driver_internal+0xfc/0x1c8
device_release_driver+0x28/0x38
bus_remove_device+0xd4/0x158
device_del+0x160/0x3a0
unregister_dev_dax+0x30/0x68
devm_action_release+0x20/0x30
release_nodes+0x150/0x240
devres_release_all+0x6c/0x1d0
device_release_driver_internal+0x10c/0x1c8
driver_detach+0xac/0x170
bus_remove_driver+0x64/0x130
driver_unregister+0x34/0x60
dax_pmem_exit+0x14/0xffc4 [dax_pmem]
__arm64_sys_delete_module+0x18c/0x2d0
el0_svc_common.constprop.2+0x78/0x168
do_el0_svc+0x34/0xa0
el0_sync_handler+0xe0/0x188
el0_sync+0x164/0x180

It is caused by the bogus nid (-1). Although the root cause is pmem dax
translates from pxm to node_id incorrectly due to numa_off, it is worth
hardening the codes in try_offline_node(), quiting if !pgdat.

Signed-off-by: Jia He <justin.he@xxxxxxx>
---
mm/memory_hotplug.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index da374cd3d45b..e1e290577b45 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1680,6 +1680,9 @@ void try_offline_node(int nid)
pg_data_t *pgdat = NODE_DATA(nid);
int rc;

+ if (WARN_ON(!pgdat))
+ return;
+
/*
* If the node still spans pages (especially ZONE_DEVICE), don't
* offline it. A node spans memory after move_pfn_range_to_zone(),
--
2.17.1