On 06.07.20 03:19, Jia He wrote: > 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(), > Hm. If I am not wrong, somebody used add_memory() with another nid than try_remove_memory()? Or did we pass the node_possible(nid) check in add_memory_resource(), and succeeded to add to nid==-1? Having that said, this feels somewhat wrong, especially checking against pgdat down in try_offline_node(). It really has to be the same nid as used when adding - and that nid has to be sane. -- Thanks, David / dhildenb
