[PATCH 4.18 007/158] mm/hugetlb: filter out hugetlb pages if HUGEPAGE migration is not supported.

[Greg Kroah-Hartman]

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>

commit 464c7ffbcb164b2e5cebfa406b7fc6cdb7945344 upstream.

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;
	}

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.

This issue was revealed by, but not caused by 72b39cfc4d75 ("mm,
memory_hotplug: do not fail offlining too early").

Link: http://lkml.kernel.org/r/20180824063314.21981-1-aneesh.kumar@xxxxxxxxxxxxx
Fixes: 72b39cfc4d75 ("mm, memory_hotplug: do not fail offlining too early")
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
Reported-by: Haren Myneni <haren@xxxxxxxxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Reviewed-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 mm/memory_hotplug.c |    3 ++-
 mm/page_alloc.c     |    4 ++++
 2 files changed, 6 insertions(+), 1 deletion(-)

--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1341,7 +1341,8 @@ static unsigned long scan_movable_pages(
 			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,
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7649,6 +7649,10 @@ bool has_unmovable_pages(struct zone *zo
 		 * 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;
 		}