On Wed 20-03-19 16:07:32, Baoquan He wrote:
> In function node_states_check_changes_online(), N_HIGH_MEMORY is used
> to substitute ZONE_HIGHMEM directly. This is not right. N_HIGH_MEMORY
> always has value '3' if CONFIG_HIGHMEM=y, while ZONE_HIGHMEM's value
> is not. It depends on whether CONFIG_ZONE_DMA/CONFIG_ZONE_DMA32 are
> enabled. Obviously it's not true for CONFIG_ZONE_DMA32 on 32bit system,
> and CONFIG_ZONE_DMA is also optional.
>
> Replace it with ZONE_HIGHMEM.
N*MEMORY is confusing as hell but I am really curious whether we have
ZONE_DMA32 and ZONE_HIGMEM together?
That being said N.*MEMORY is intended to check for nodes rather than
zones so the patch looks good to me but I think the above explanation is
misleading and will add even more mud to the picture when somebody tries
to understand what the heck is going on here.
> Fixes: 8efe33f40f3e ("mm/memory_hotplug.c: simplify
> node_states_check_changes_online")
> Signed-off-by: Baoquan He <b...@redhat.com>
> ---
> mm/memory_hotplug.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 6b05576fb4ec..09911d34a3be 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -712,7 +712,7 @@ static void node_states_check_changes_online(unsigned
> long nr_pages,
> if (zone_idx(zone) <= ZONE_NORMAL && !node_state(nid, N_NORMAL_MEMORY))
> arg->status_change_nid_normal = nid;
> #ifdef CONFIG_HIGHMEM
> - if (zone_idx(zone) <= N_HIGH_MEMORY && !node_state(nid, N_HIGH_MEMORY))
> + if (zone_idx(zone) <= ZONE_HIGHMEM && !node_state(nid, N_HIGH_MEMORY))
> arg->status_change_nid_high = nid;
> #endif
> }
> --
> 2.17.2
--
Michal Hocko
SUSE Labs
