On Thu 26-04-18 11:58:34, Pavel Tatashin wrote:
> Memory hotplug, and hotremove operate with per-block granularity. If
> machine has large amount of memory (more than 64G), the size of memory
> block can span multiple sections. By mistake, during hotremove we set
> only the first section to offline state.
>
> The bug was discovered because kernel selftest started to fail:
> https://lkml.kernel.org/r/20180423011247.GK5563@yexl-desktop
>
> After commit, "mm/memory_hotplug: optimize probe routine". But, the bug is
> older than this commit. In this optimization we also added a check for
> sections to be in a proper state during hotplug operation.
>
> Fixes: 2d070eab2e82 ("mm: consider zone which is not fully populated to have
> holes")
Dohh. When I saw this I've had that feeling that I have fixed this
already and it must have get lost somewhere. But no, this was the same
bug in a different path b4ccec41af82 ("mm/sparse.c: fix typo in
online_mem_sections"). I wonder why I haven't noticed the same pattern
in the offline path.
Thanks for noticing and fixing this.
> Signed-off-by: Pavel Tatashin <pasha.tatas...@oracle.com>
Acked-by: Michal Hocko <mho...@suse.com>
> ---
> mm/sparse.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/sparse.c b/mm/sparse.c
> index 62eef264a7bd..73dc2fcc0eab 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -629,7 +629,7 @@ void offline_mem_sections(unsigned long start_pfn,
> unsigned long end_pfn)
> unsigned long pfn;
>
> for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
> - unsigned long section_nr = pfn_to_section_nr(start_pfn);
> + unsigned long section_nr = pfn_to_section_nr(pfn);
> struct mem_section *ms;
>
> /*
> --
> 1.8.3.1
>
--
Michal Hocko
SUSE Labs
