Messages in this thread | | | Date | Wed, 20 Mar 2019 09:46:00 +0100 | From | Michal Hocko <> | Subject | Re: [PATCH] mm, memory_hotplug: Fix the wrong usage of N_HIGH_MEMORY |
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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 <bhe@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
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