Subject: [PATCH RFC 08/29] mm/migrate: rename putback_movable_folio() to putback_movable_ops_page()

From: David Hildenbrand <[email-masked]>
Date: Wed, 18 Jun 2025 19:39:51 +0200

... and factor the complete handling of movable_ops pages out.
Convert it similar to isolate_movable_ops_page().

While at it, convert the VM_BUG_ON_FOLIO() into a VM_WARN_ON_PAGE().

Signed-off-by: David Hildenbrand <[email-masked]>
---
 mm/migrate.c | 37 ++++++++++++++++++++++++-------------
 1 file changed, 24 insertions(+), 13 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 6bbb455f8b593..32e77898f7d6c 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -133,12 +133,30 @@ bool isolate_movable_ops_page(struct page *page, isolate_mode_t mode)
 	return false;
 }
 
-static void putback_movable_folio(struct folio *folio)
+/**
+ * putback_movable_ops_page - putback an isolated movable_ops page
+ * @page: The isolated page.
+ *
+ * Putback an isolated movable_ops page.
+ *
+ * After the page was putback, it might get freed instantly.
+ */
+static void putback_movable_ops_page(struct page *page)
 {
-	const struct movable_operations *mops = folio_movable_ops(folio);
-
-	mops->putback_page(&folio->page);
-	folio_clear_isolated(folio);
+	/*
+	 * TODO: these pages will not be folios in the future. All
+	 * folio dependencies will have to be removed.
+	 */
+	struct folio *folio = page_folio(page);
+
+	VM_WARN_ON_ONCE_PAGE(!PageIsolated(page), page);
+	folio_lock(folio);
+	/* If the page was released by it's owner, there is nothing to do. */
+	if (PageMovable(page))
+		page_movable_ops(page)->putback_page(page);
+	ClearPageIsolated(page);
+	folio_unlock(folio);
+	folio_put(folio);
 }
 
 /*
@@ -166,14 +184,7 @@ void putback_movable_pages(struct list_head *l)
 		 * have PAGE_MAPPING_MOVABLE.
 		 */
 		if (unlikely(__folio_test_movable(folio))) {
-			VM_BUG_ON_FOLIO(!folio_test_isolated(folio), folio);
-			folio_lock(folio);
-			if (folio_test_movable(folio))
-				putback_movable_folio(folio);
-			else
-				folio_clear_isolated(folio);
-			folio_unlock(folio);
-			folio_put(folio);
+			putback_movable_ops_page(&folio->page);
 		} else {
 			node_stat_mod_folio(folio, NR_ISOLATED_ANON +
 					folio_is_file_lru(folio), -folio_nr_pages(folio));
-- 
2.49.0