On Thu 26-04-18 21:11:11, Michal Hocko wrote:
> 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>
Btw. Cc: stable would be appropriate.
>
> > 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
--
Michal Hocko
SUSE Labs
