Messages in this thread | | | Date | Mon, 7 Mar 2022 15:04:52 +0800 | Subject | Re: [PATCH 14/16] mm/migration: fix potential invalid node access for reclaim-based migration | From | Baolin Wang <> |
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On 3/7/2022 1:14 PM, Huang, Ying wrote: > Baolin Wang <baolin.wang@linux.alibaba.com> writes: > >> On 3/4/2022 5:34 PM, Miaohe Lin wrote: >>> If we failed to setup hotplug state callbacks for mm/demotion:online in >>> some corner cases, node_demotion will be left uninitialized. Invalid node >>> might be returned from the next_demotion_node() when doing reclaim-based >>> migration. Use kcalloc to allocate node_demotion to fix the issue. >>> Fixes: ac16ec835314 ("mm: migrate: support multiple target nodes >>> demotion") >>> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> >>> --- >>> mm/migrate.c | 6 +++--- >>> 1 file changed, 3 insertions(+), 3 deletions(-) >>> diff --git a/mm/migrate.c b/mm/migrate.c >>> index 279940c0c064..7b1c0b988234 100644 >>> --- a/mm/migrate.c >>> +++ b/mm/migrate.c >>> @@ -2516,9 +2516,9 @@ static int __init migrate_on_reclaim_init(void) >>> { >>> int ret; >>> - node_demotion = kmalloc_array(nr_node_ids, >>> - sizeof(struct demotion_nodes), >>> - GFP_KERNEL); >>> + node_demotion = kcalloc(nr_node_ids, >>> + sizeof(struct demotion_nodes), >>> + GFP_KERNEL); >> >> Nit: not sure if this is worthy of this rare corner case, but I think >> the target demotion nodes' default value should be NUMA_NO_NODE >> instead of 0. > > The "nr" field of "struct demotion_nodes" should be initialized as 0. I > think that is checked before "nodes[]" field.
Right, but it will be confusing that if nr = 0, while the nodes[] still contains valid node id 0. While we are at this, why not initialize the node_demotion structure with a clear default value? Anyway, no strong opinion on this :)
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