Re: [PATCH v2] mm/memory-tiers: reset demotion targets of nodes without memory

[Zi Yan]

On 20 Oct 2026, at 22:44, Gregory Price (Meta) wrote:

> When a node loses its last memory, offline_pages() clears N_MEMORY
> before the memory-tier callback rebuilds the demotion targets.
> disable_all_demotion_targets() resets only N_MEMORY nodes, so the node
> keeps its old node_demotion[] entry while it has no memory. Before
> 6c542ab75714, the reset covered every online node.
>
> A reclaimer reads the stale entry only between the node regaining memory
> and its targets being rebuilt, and it filters the entry against the
> current allowed targets, so there is no user-visible effect. To see it,
> online and then offline a node's only DIMM: a debugger still finds the
> lower-tier node in node_demotion[nid].preferred.
>
> Reset the targets of every node.
>
> Fixes: 6c542ab75714 ("mm/demotion: build demotion targets based on explicit memory tiers")
> Signed-off-by: Gregory Price (Meta) <gourry@xxxxxxxxxx>
> ---
> v2: +comment
>
>  mm/memory-tiers.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
LGTM. Thanks.

Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>

Best Regards,
Yan, Zi