Messages in this thread | | | Date | Wed, 20 Mar 2019 17:06:24 +0800 | From | Baoquan He <> | Subject | Re: [PATCH] mm, memory_hotplug: Fix the wrong usage of N_HIGH_MEMORY |
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On 03/20/19 at 09:46am, Michal Hocko wrote: > 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?
Not sure. AFAIK, on x86_32 it can't be.
> > 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.
Yes, agree. I also thought this again after I sent out patch, feel log is not good. As you said, they are value of enum node_states and enum zone_type separately.
How about this:
~~~ In function node_states_check_changes_online(), N_HIGH_MEMORY is used to substitute ZONE_HIGHMEM directly. This is not right. N_HIGH_MEMORY is to mark the memory state of node. Here zone index is checked, which should be compared with 'ZONE_HIGHMEM' accordingly.
Replace it with ZONE_HIGHMEM. ~~~ > > > 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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