[PATCH] mm: fix shrink nr.unqueued_dirty counter issue

[Zhiguo Jiang]

It is needed to ensure sc->nr.unqueued_dirty > 0, which can avoid to
set PGDAT_DIRTY flag when sc->nr.unqueued_dirty and sc->nr.file_taken
are both zero at the same time.

Signed-off-by: Zhiguo Jiang <justinjiang@xxxxxxxx>
---
 mm/vmscan.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
 mode change 100644 => 100755 mm/vmscan.c

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 91e7d334a7ca..7c0cd7ecdfab
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -5957,7 +5957,8 @@ static void shrink_node(pg_data_t *pgdat, struct scan_control *sc)
 			set_bit(PGDAT_WRITEBACK, &pgdat->flags);
 
 		/* Allow kswapd to start writing pages during reclaim.*/
-		if (sc->nr.unqueued_dirty == sc->nr.file_taken)
+		if (sc->nr.unqueued_dirty &&
+			sc->nr.unqueued_dirty == sc->nr.file_taken)
 			set_bit(PGDAT_DIRTY, &pgdat->flags);
 
 		/*
-- 
2.39.0