[PATCH] mm/hugetlb: filter out hugetlb pages if HUGEPAGE migration is not supported.

["Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>]

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.

Acked-by: Michal Hocko <mhocko@suse.com>
Reported-by: Haren Myneni <haren@linux.vnet.ibm.com>
CC: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.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