From: Miaohe Lin Subject: mm/migration: fix potential page refcounts leak in migrate_pages In -ENOMEM case, there might be some subpages of fail-to-migrate THPs left in thp_split_pages list. We should move them back to migration list so that they could be put back to the right list by the caller otherwise the page refcnt will be leaked here. Also adjust nr_failed and nr_thp_failed accordingly to make vm events account more accurate. Link: https://lkml.kernel.org/r/20220318111709.60311-10-linmiaohe@huawei.com Fixes: b5bade978e9b ("mm: migrate: fix the return value of migrate_pages()") Signed-off-by: Miaohe Lin Reviewed-by: Zi Yan Reviewed-by: "Huang, Ying" Reviewed-by: Baolin Wang Reviewed-by: Muchun Song Cc: Alistair Popple Signed-off-by: Andrew Morton --- mm/migrate.c | 8 ++++++++ 1 file changed, 8 insertions(+) --- a/mm/migrate.c~mm-migration-fix-potential-page-refcounts-leak-in-migrate_pages +++ a/mm/migrate.c @@ -1446,6 +1446,14 @@ retry: } nr_failed_pages += nr_subpages; + /* + * There might be some subpages of fail-to-migrate THPs + * left in thp_split_pages list. Move them back to migration + * list so that they could be put back to the right list by + * the caller otherwise the page refcnt will be leaked. + */ + list_splice_init(&thp_split_pages, from); + nr_thp_failed += thp_retry; goto out; case -EAGAIN: if (is_thp) _