mm/migrate: Convert writeout() to take a folio

Use a folio throughout this function.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

mm/migrate.c

@@ -761,11 +761,10 @@ int buffer_migrate_page_norefs(struct address_space *mapping,
 #endif
 
 /*
- * Writeback a page to clean the dirty state
+ * Writeback a folio to clean the dirty state
  */
-static int writeout(struct address_space *mapping, struct page *page)
+static int writeout(struct address_space *mapping, struct folio *folio)
 {
-	struct folio *folio = page_folio(page);
 	struct writeback_control wbc = {
 		.sync_mode = WB_SYNC_NONE,
 		.nr_to_write = 1,
@@ -779,25 +778,25 @@ static int writeout(struct address_space *mapping, struct page *page)
 		/* No write method for the address space */
 		return -EINVAL;
 
-	if (!clear_page_dirty_for_io(page))
+	if (!folio_clear_dirty_for_io(folio))
 		/* Someone else already triggered a write */
 		return -EAGAIN;
 
 	/*
-	 * A dirty page may imply that the underlying filesystem has
-	 * the page on some queue. So the page must be clean for
-	 * migration. Writeout may mean we loose the lock and the
-	 * page state is no longer what we checked for earlier.
+	 * A dirty folio may imply that the underlying filesystem has
+	 * the folio on some queue. So the folio must be clean for
+	 * migration. Writeout may mean we lose the lock and the
+	 * folio state is no longer what we checked for earlier.
 	 * At this point we know that the migration attempt cannot
 	 * be successful.
 	 */
 	remove_migration_ptes(folio, folio, false);
 
-	rc = mapping->a_ops->writepage(page, &wbc);
+	rc = mapping->a_ops->writepage(&folio->page, &wbc);
 
 	if (rc != AOP_WRITEPAGE_ACTIVATE)
 		/* unlocked. Relock */
-		lock_page(page);
+		folio_lock(folio);
 
 	return (rc < 0) ? -EIO : -EAGAIN;
 }
@@ -817,7 +816,7 @@ static int fallback_migrate_folio(struct address_space *mapping,
 		default:
 			return -EBUSY;
 		}
-		return writeout(mapping, &src->page);
+		return writeout(mapping, src);
 	}
 
 	/*