migrate_pages(): fix failure counting for THP subpages retrying

If THP is failed to be migrated for -ENOSYS and -ENOMEM, the THP will be
split into thp_split_pages, and after other pages are migrated, pages in
thp_split_pages will be migrated with no_subpage_counting == true, because
its failure have been counted already.  If some pages in thp_split_pages
are retried during migration, we should not count their failure if
no_subpage_counting == true too.  This is done this patch to fix the
failure counting for THP subpages retrying.

Link: https://lkml.kernel.org/r/20220817081408.513338-5-ying.huang@intel.com
Fixes: 5984fabb ("mm: move_pages: report the number of non-attempted pages")
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/migrate.c

@@ -1545,7 +1545,8 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 			}
 		}
 	}
-	nr_failed += retry;
+	if (!no_subpage_counting)
+		nr_failed += retry;
 	nr_thp_failed += thp_retry;
 	/*
 	 * Try to migrate subpages of fail-to-migrate THPs, no nr_failed