From: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> commit 03e5f82ea632af329e32ec03d952b2d99497eeaa upstream. During THP migration, if THPs are not migrated but they are split and all subpages are migrated successfully, migrate_pages() will still return the number of THP pages that were not migrated. This will confuse the callers of migrate_pages(). For example, the longterm pinning will failed though all pages are migrated successfully. Thus we should return 0 to indicate that all pages are migrated in this case Link: https://lkml.kernel.org/r/de386aa864be9158d2f3b344091419ea7c38b2f7.1666599848.git.baolin.wang@xxxxxxxxxxxxxxxxx Fixes: b5bade978e9b ("mm: migrate: fix the return value of migrate_pages()") Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> Reviewed-by: Alistair Popple <apopple@xxxxxxxxxx> Reviewed-by: Yang Shi <shy828301@xxxxxxxxx> Cc: David Hildenbrand <david@xxxxxxxxxx> Cc: "Huang, Ying" <ying.huang@xxxxxxxxx> Cc: Zi Yan <ziy@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/migrate.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1558,6 +1558,13 @@ out: */ list_splice(&ret_pages, from); + /* + * Return 0 in case all subpages of fail-to-migrate THPs are + * migrated successfully. + */ + if (list_empty(from)) + rc = 0; + count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded); count_vm_events(PGMIGRATE_FAIL, nr_failed_pages); count_vm_events(THP_MIGRATION_SUCCESS, nr_thp_succeeded);
