[PATCHv3 01/11] mm/migrate: Transfer PG_dropbehind to the new folio

[Kirill A. Shutemov]

Do not lose the flag on page migration.

Ideally, these folios should be freed instead of migration. But it
requires to find right spot do this and proper testing.

Transfer the flag for now.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
 mm/migrate.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/migrate.c b/mm/migrate.c
index fb19a18892c8..1fb0698273f7 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -682,6 +682,10 @@ void folio_migrate_flags(struct folio *newfolio, struct folio *folio)
 	if (folio_test_dirty(folio))
 		folio_set_dirty(newfolio);
 
+	/* TODO: free the folio on migration? */
+	if (folio_test_dropbehind(folio))
+		folio_set_dropbehind(newfolio);
+
 	if (folio_test_young(folio))
 		folio_set_young(newfolio);
 	if (folio_test_idle(folio))
-- 
2.47.2