[PATCH] mm: revert slight behavior change for swappiness 1-200

[Barry Song (Xiaomi)]

Baoquan's review found that we unexpectedly introduced a slight behavior
change for swappiness 1-200. We could now have a case like:

1. First scan -> `scanned != 0`
2. Second scan -> `scanned = 0`
3. Type fallback

Step 3 was impossible before. Let's remove this possibility.

Reported-by: Baoquan He <baoquan.he@xxxxxxxxx>
Closes: https://lore.kernel.org/linux-mm/apfZQE1X6zGAsBb_@fedora/
Signed-off-by: Barry Song (Xiaomi) <baohua@xxxxxxxxxx>
---
 mm/vmscan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index bf2786c7247d..ba7adf36e69f 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4939,7 +4939,7 @@ static int isolate_folios(unsigned long nr_to_scan, struct lruvec *lruvec,
 	 * We are running out of the current reclaim type. Fall back to
 	 * the other type if allowed.
 	 */
-	if (!scanned && type_fallback_allowed) {
+	if (!scanned && !tried && type_fallback_allowed) {
 		type = !type;
 		tried = true;
 		type_fallback_allowed = false;
-- 
2.39.3 (Apple Git-146)