When THP migration, if THPs are split and all subpages are migrated successfully , the migrate_pages() will still return the number of THP that were not migrated. That will confuse the callers of migrate_pages(), for example, which will make the longterm pinning failed though all pages are migrated successfully. Thus we should return 0 to indicate all pages are migrated in this case. Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> --- Changes from v1: - Fix the return value of migrate_pages() instead of fixing the callers' validation. --- mm/migrate.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/mm/migrate.c b/mm/migrate.c index 8e5eb6e..1da0dbc 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1582,6 +1582,13 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, */ list_splice(&ret_pages, from); + /* + * Return 0 in case all subpages of fail-to-migrate THPs are + * migrated successfully. + */ + if (nr_thp_split && 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); -- 1.8.3.1
