Re: [PATCH v5 12/12] mm/mmzone: remove zonelist_node_idx()

["Zi Yan" <ziy@nvidia.com>]

On Sat Oct 31, 2026 at 10:13 PM EDT, Gregory Price (Meta) wrote:
> zonelist_node_idx() looks like it returns a field of the zoneref, as
> zonelist_zone_idx() does, but it loads the zone from the slot again.
>
> Memory hotplug rewrites zonelists in place, so a caller that has already
> checked the slot can get a different zone, or the NULL terminator, from
> that second load.
>
> __next_zones_zonelist() and mempolicy_slab_node() had this bug.
>
> Remove the helper and open-code it in its two remaining callers, neither
> of which can race with a rebuild.  local_memory_node() runs either inside
> __build_all_zonelists() or during CPU bring-up, which holds
> cpu_hotplug_lock for write and so excludes mem_hotplug_begin().
>
> The lookup in mpol_misplaced() is unreachable: it needs a policy with
> MPOL_F_MOF but not MPOL_F_MORON, and nothing sets one without the other.
>
> Signed-off-by: Gregory Price (Meta) <gourry@gourry.net>
> ---
>  include/linux/mmzone.h | 6 ------
>  mm/mempolicy.c         | 2 +-
>  mm/page_alloc.c        | 2 +-
>  3 files changed, 2 insertions(+), 8 deletions(-)
>
LGTM.

Reviewed-by: Zi Yan <ziy@nvidia.com>

-- 
Best Regards,
Yan, Zi