On Fri, Aug 24, 2018 at 09:58:15AM +0200, Michal Hocko wrote:
> On Fri 24-08-18 12:03:14, Aneesh Kumar K.V wrote:
> > When scanning for movable pages, filter out Hugetlb pages if hugepage
> > migration
> > is not supported. Without this we hit infinte loop in __offline pages where
> > we
> > do
> > pfn = scan_movable_pages(start_pfn, end_pfn);
> > if (pfn) { /* We have movable pages */
> > ret = do_migrate_range(pfn, end_pfn);
> > goto repeat;
> > }
> >
> > We do support hugetlb migration ony if the hugetlb pages are at pmd level.
> > Here
> > we just check for Kernel config. The gigantic page size check is done in
> > page_huge_active.
>
> Well, this is a bit misleading. I would say that
>
> Fix this by checking hugepage_migration_supported both in has_unmovable_pages
> which is the primary backoff mechanism for page offlining and for
> consistency reasons also into scan_movable_pages because it doesn't make
> any sense to return a pfn to non-migrateable huge page.
>
> > Acked-by: Michal Hocko <mho...@suse.com>
> > Reported-by: Haren Myneni <ha...@linux.vnet.ibm.com>
> > CC: Naoya Horiguchi <n-horigu...@ah.jp.nec.com>
> > Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
>
> I would add
> Fixes: 72b39cfc4d75 ("mm, memory_hotplug: do not fail offlining too early")
>
> Not because the bug has been introduced by that commit but rather
> because the issue would be latent before that commit.
>
> My Acked-by still holds.
Looks good to me (with Michal's update on description).
Reviewed-by: Naoya Horiguchi <n-horigu...@ah.jp.nec.com>
>
> > ---
> > mm/memory_hotplug.c | 3 ++-
> > mm/page_alloc.c | 4 ++++
> > 2 files changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> > index 9eea6e809a4e..38d94b703e9d 100644
> > --- a/mm/memory_hotplug.c
> > +++ b/mm/memory_hotplug.c
> > @@ -1333,7 +1333,8 @@ static unsigned long scan_movable_pages(unsigned long
> > start, unsigned long end)
> > if (__PageMovable(page))
> > return pfn;
> > if (PageHuge(page)) {
> > - if (page_huge_active(page))
> > + if
> > (hugepage_migration_supported(page_hstate(page)) &&
> > + page_huge_active(page))
> > return pfn;
> > else
> > pfn = round_up(pfn + 1,
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index c677c1506d73..b8d91f59b836 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -7709,6 +7709,10 @@ bool has_unmovable_pages(struct zone *zone, struct
> > page *page, int count,
> > * handle each tail page individually in migration.
> > */
> > if (PageHuge(page)) {
> > +
> > + if (!hugepage_migration_supported(page_hstate(page)))
> > + goto unmovable;
> > +
> > iter = round_up(iter + 1, 1<<compound_order(page)) - 1;
> > continue;
> > }
> > --
> > 2.17.1
>
> --
> Michal Hocko
> SUSE Labs
>
