[PATCH 2/2] mm/mglru: reset page lru tier bits when activating

[Wei Xu <weixugc@xxxxxxxxxx>]

folio_activate() calls lru_gen_add_folio() to move the folio to the
youngest generation.  But unlike folio_update_gen()/folio_inc_gen(),
lru_gen_add_folio() doesn't reset the folio lru tier bits
(LRU_REFS_MASK | LRU_REFS_FLAGS).  Fix this inconsistency in
lru_gen_add_folio() when activating a folio.

Fixes: 018ee47f1489 ("mm: multi-gen LRU: exploit locality in rmap")
Signed-off-by: Wei Xu <weixugc@xxxxxxxxxx>
---
 include/linux/mm_inline.h | 5 ++++-
 include/linux/mmzone.h    | 2 ++
 mm/vmscan.c               | 2 --
 3 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
index 6f801c7b36e2..87580e8363ef 100644
--- a/include/linux/mm_inline.h
+++ b/include/linux/mm_inline.h
@@ -222,6 +222,7 @@ static inline bool lru_gen_add_folio(struct lruvec *lruvec, struct folio *folio,
 {
 	unsigned long seq;
 	unsigned long flags;
+	unsigned long mask;
 	int gen = folio_lru_gen(folio);
 	int type = folio_is_file_lru(folio);
 	int zone = folio_zonenum(folio);
@@ -257,7 +258,9 @@ static inline bool lru_gen_add_folio(struct lruvec *lruvec, struct folio *folio,
 	gen = lru_gen_from_seq(seq);
 	flags = (gen + 1UL) << LRU_GEN_PGOFF;
 	/* see the comment on MIN_NR_GENS about PG_active */
-	set_mask_bits(&folio->flags, LRU_GEN_MASK | BIT(PG_active), flags);
+	mask = LRU_GEN_MASK | BIT(PG_active);
+	mask |= folio_test_active(folio) ? (LRU_REFS_MASK | LRU_REFS_FLAGS) : 0;
+	set_mask_bits(&folio->flags, mask, flags);
 
 	lru_gen_update_size(lruvec, folio, -1, gen);
 	/* for folio_rotate_reclaimable() */
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 17506e4a2835..96dea31fb211 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -403,6 +403,8 @@ enum {
 	NR_LRU_GEN_CAPS
 };
 
+#define LRU_REFS_FLAGS		(BIT(PG_referenced) | BIT(PG_workingset))
+
 #define MIN_LRU_BATCH		BITS_PER_LONG
 #define MAX_LRU_BATCH		(MIN_LRU_BATCH * 64)
 
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 9d1e1c4e383d..907262ebaef8 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2601,8 +2601,6 @@ static bool should_clear_pmd_young(void)
  *                          shorthand helpers
  ******************************************************************************/
 
-#define LRU_REFS_FLAGS	(BIT(PG_referenced) | BIT(PG_workingset))
-
 #define DEFINE_MAX_SEQ(lruvec)						\
 	unsigned long max_seq = READ_ONCE((lruvec)->lrugen.max_seq)
 
-- 
2.47.0.rc1.288.g06298d1525-goog