Merge tag 'loongarch-kvm-6.11' of git://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson into HEAD

LoongArch KVM changes for v6.11

1. Add ParaVirt steal time support.
2. Add some VM migration enhancement.
3. Add perf kvm-stat support for loongarch.

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;