Re: [PATCH 1/2] mm: drop migrate type checks from has_unmovable_pages

[Michal Hocko]

On Tue 17-10-17 22:41:08, Michael Ellerman wrote:
> Michal Hocko <mhocko@xxxxxxxxxx> writes:
> 
> > From: Michal Hocko <mhocko@xxxxxxxx>
> >
> > Michael has noticed that the memory offline tries to migrate kernel code
> > pages when doing
> >  echo 0 > /sys/devices/system/memory/memory0/online
> >
> > The current implementation will fail the operation after several failed
> > page migration attempts but we shouldn't even attempt to migrate
> > that memory and fail right away because this memory is clearly not
> > migrateable. This will become a real problem when we drop the retry loop
> > counter resp. timeout.
> >
> > The real problem is in has_unmovable_pages in fact. We should fail if
> > there are any non migrateable pages in the area. In orther to guarantee
> > that remove the migrate type checks because MIGRATE_MOVABLE is not
> > guaranteed to contain only migrateable pages. It is merely a heuristic.
> > Similarly MIGRATE_CMA does guarantee that the page allocator doesn't
> > allocate any non-migrateable pages from the block but CMA allocations
> > themselves are unlikely to migrateable. Therefore remove both checks.
> >
> > Reported-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> > Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
> 
> Thanks, that works for me.
> 
> Tested-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>

Thanks a lot Michael!

Andrew, could you add these two patches and merge them before
mm-memory_hotplug-do-not-fail-offlining-too-early.patch? Or should I
rather repost the full series (including 2 already merged patches?
again?
-- 
Michal Hocko
SUSE Labs