[PATCH v3] mm/damon/paddr: fix missing folio_put()

[Andrew Yang]

From: "andrew.yang" <andrew.yang at mediatek.com>

damon_get_folio() would always increase folio _refcount and
folio_isolate_lru() would increase folio _refcount if the folio's lru
flag is set.

If an unevictable folio isolated successfully, there will be two more
_refcount. The one from folio_isolate_lru() will be decreased in
folio_puback_lru(), but the other one from damon_get_folio() will be
left behind. This causes a pin page.

Whatever the case, the _refcount from damon_get_folio() should be
decreased.

Signed-off-by: andrew.yang <andrew.yang at mediatek.com>
Fixes: 57223ac29584 ("mm/damon/paddr: support the pageout scheme")
Cc: <stable at vger.kernel.org> # 5.16.x
---
v3:
  add fixes tag and cc stable
v2:
  according to David's suggestion
    1. revise subject
  according to SeongJae's suggestions
    1. rebase to mm-unstable tree 
    2. remove braces for th single statements
---
 mm/damon/paddr.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
index 607bb69e526c..6c655d9b5639 100644
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -250,12 +250,11 @@ static unsigned long damon_pa_pageout(struct damon_region *r, struct damos *s)
 			folio_put(folio);
 			continue;
 		}
-		if (folio_test_unevictable(folio)) {
+		if (folio_test_unevictable(folio))
 			folio_putback_lru(folio);
-		} else {
+		else
 			list_add(&folio->lru, &folio_list);
-			folio_put(folio);
-		}
+		folio_put(folio);
 	}
 	applied = reclaim_pages(&folio_list);
 	cond_resched();
-- 
2.18.0