[PATCH RFC v2 10/15] mm/damon: convert to LRU refs based operations

[Kairui Song via B4 Relay]

From: Kairui Song <kasong@xxxxxxxxxxx>

damon_pa_pageout() cleared PG_referenced directly, which under MGLRU
may corrupts the folio's refs count in later commits. That flag is now
bit 0 of the count (LRU_REFS_FLAGS).

Reset the count instead under MGLRU.

Signed-off-by: Kairui Song <kasong@xxxxxxxxxxx>
---
 mm/damon/paddr.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
index 79195026b903..38d3ff7019e3 100644
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -280,7 +280,14 @@ static unsigned long damon_pa_pageout(struct damon_region *r,
 		else
 			*sz_filter_passed += folio_size(folio) / addr_unit;
 
-		folio_clear_referenced(folio);
+		/*
+		 * DAMON only gets here for regions it measured as cold,
+		 * so the hotness can be, and better be dropped.
+		 */
+		if (lru_gen_enabled())
+			folio_set_lru_refs(folio, 0);
+		else
+			folio_clear_referenced(folio);
 		folio_test_clear_young(folio);
 		if (!folio_isolate_lru(folio))
 			goto put_folio;

-- 
2.55.0