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-rw-r--r--mm/migrate.c13
1 files changed, 12 insertions, 1 deletions
diff --git a/mm/migrate.c b/mm/migrate.c
index 50b60fb414e9..3fe4a9854f7a 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1654,7 +1654,16 @@ static int migrate_pages_batch(struct list_head *from,
/*
* The rare folio on the deferred split list should
- * be split now. It should not count as a failure.
+ * be split now. It should not count as a failure:
+ * but increment nr_failed because, without doing so,
+ * migrate_pages() may report success with (split but
+ * unmigrated) pages still on its fromlist; whereas it
+ * always reports success when its fromlist is empty.
+ * stats->nr_thp_failed should be increased too,
+ * otherwise stats inconsistency will happen when
+ * migrate_pages_batch is called via migrate_pages()
+ * with MIGRATE_SYNC and MIGRATE_ASYNC.
+ *
* Only check it without removing it from the list.
* Since the folio can be on deferred_split_scan()
* local list and removing it can cause the local list
@@ -1669,6 +1678,8 @@ static int migrate_pages_batch(struct list_head *from,
if (nr_pages > 2 &&
!list_empty(&folio->_deferred_list)) {
if (try_split_folio(folio, split_folios) == 0) {
+ nr_failed++;
+ stats->nr_thp_failed += is_thp;
stats->nr_thp_split += is_thp;
stats->nr_split++;
continue;