[PATCH 2/5] mm: migration of hugetlbfs page skip memcg

[Hugh Dickins]

hugetlbfs pages do not participate in memcg: so although they do find
most of migrate_page_states() useful, it would be better if they did
not call into mem_cgroup_migrate() - where Qian Cai reported that LTP's
move_pages12 triggers the warning in Alex Shi's prospective commit
"mm/memcg: warning on !memcg after readahead page charged".

Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
---
This fixes a likely future warning, but is just a cleanup right now.

 mm/migrate.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- 5.9-rc2/mm/migrate.c	2020-08-16 17:32:50.665507048 -0700
+++ linux/mm/migrate.c	2020-08-28 17:42:07.967278385 -0700
@@ -668,7 +668,8 @@ void migrate_page_states(struct page *ne
 
 	copy_page_owner(page, newpage);
 
-	mem_cgroup_migrate(page, newpage);
+	if (!PageHuge(page))
+		mem_cgroup_migrate(page, newpage);
 }
 EXPORT_SYMBOL(migrate_page_states);