On Mon 28-01-19 09:50:54, Andrew Morton wrote:
> On Mon, 28 Jan 2019 15:45:04 +0100 Michal Hocko <mhocko@xxxxxxxxxx> wrote:
>
> > Mikhail has posted fixes for the two bugs quite some time ago [1]. I
> > have pushed back on those fixes because I believed that it is much
> > better to plug the problem at the initialization time rather than play
> > whack-a-mole all over the hotplug code and find all the places which
> > expect the full memory section to be initialized. We have ended up with
> > 2830bf6f05fb ("mm, memory_hotplug: initialize struct pages for the full
> > memory section") merged and cause a regression [2][3]. The reason is
> > that there might be memory layouts when two NUMA nodes share the same
> > memory section so the merged fix is simply incorrect.
> >
> > In order to plug this hole we really have to be zone range aware in
> > those handlers. I have split up the original patch into two. One is
> > unchanged (patch 2) and I took a different approach for `removable'
> > crash. It would be great if Mikhail could test it still works for his
> > memory layout.
> >
> > [1] http://lkml.kernel.org/r/20181105150401.97287-2-zaslonko@xxxxxxxxxxxxx
> > [2] https://bugzilla.redhat.com/show_bug.cgi?id=1666948
> > [3] http://lkml.kernel.org/r/20190125163938.GA20411@xxxxxxxxxxxxxx
>
> Any thoughts on which kernel version(s) need these patches?
My remark in 2830bf6f05fb still holds
: This has alwways been problem AFAIU. It just went unnoticed because we
: have zeroed memmaps during allocation before f7f99100d8d9 ("mm: stop
: zeroing memory during allocation in vmemmap") and so the above test
: would simply skip these ranges as belonging to zone 0 or provided a
: garbage.
:
: So I guess we do care for post f7f99100d8d9 kernels mostly and
: therefore Fixes: f7f99100d8d9 ("mm: stop zeroing memory during
: allocation in vmemmap")
But, please let's wait for the patch 1 to be confirmed to fix the issue.
--
Michal Hocko
SUSE Labs
