[RFC PATCH v3 1/2] mm: vmascan: add find_folios_written_back() helper

[Chen Ridong <chenridong@xxxxxxxxxxxxxxx>]

From: Chen Ridong <chenridong@xxxxxxxxxx>

Add find_folios_written_back() helper, which will be called in the
shrink_inactive_list function in subsequent patch.

Signed-off-by: Chen Ridong <chenridong@xxxxxxxxxx>
---
 mm/vmscan.c | 73 +++++++++++++++++++++++++++++++----------------------
 1 file changed, 43 insertions(+), 30 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 76378bc257e3..af1ff76f83e7 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -283,6 +283,48 @@ static void set_task_reclaim_state(struct task_struct *task,
 	task->reclaim_state = rs;
 }
 
+/**
+ * find_folios_written_back - Find and move the written back folios to a new list.
+ * @list: filios list
+ * @clean: the written back folios list
+ * @skip: whether skip to move the written back folios to clean list.
+ */
+static inline void find_folios_written_back(struct list_head *list,
+		struct list_head *clean, bool skip)
+{
+	struct folio *folio;
+	struct folio *next;
+
+	list_for_each_entry_safe_reverse(folio, next, list, lru) {
+		if (!folio_evictable(folio)) {
+			list_del(&folio->lru);
+			folio_putback_lru(folio);
+			continue;
+		}
+
+		if (folio_test_reclaim(folio) &&
+		    (folio_test_dirty(folio) || folio_test_writeback(folio))) {
+			/* restore LRU_REFS_FLAGS cleared by isolate_folio() */
+			if (lru_gen_enabled() && folio_test_workingset(folio))
+				folio_set_referenced(folio);
+			continue;
+		}
+
+		if (skip || folio_test_active(folio) || folio_test_referenced(folio) ||
+		    folio_mapped(folio) || folio_test_locked(folio) ||
+		    folio_test_dirty(folio) || folio_test_writeback(folio)) {
+			/* don't add rejected folios to the oldest generation */
+			if (lru_gen_enabled())
+				set_mask_bits(&folio->flags, LRU_REFS_MASK | LRU_REFS_FLAGS,
+					      BIT(PG_active));
+			continue;
+		}
+
+		/* retry folios that may have missed folio_rotate_reclaimable() */
+		list_move(&folio->lru, clean);
+	}
+}
+
 /*
  * flush_reclaim_state(): add pages reclaimed outside of LRU-based reclaim to
  * scan_control->nr_reclaimed.
@@ -4567,8 +4609,6 @@ static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swap
 	int reclaimed;
 	LIST_HEAD(list);
 	LIST_HEAD(clean);
-	struct folio *folio;
-	struct folio *next;
 	enum vm_event_item item;
 	struct reclaim_stat stat;
 	struct lru_gen_mm_walk *walk;
@@ -4597,34 +4637,7 @@ static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swap
 			scanned, reclaimed, &stat, sc->priority,
 			type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON);
 
-	list_for_each_entry_safe_reverse(folio, next, &list, lru) {
-		if (!folio_evictable(folio)) {
-			list_del(&folio->lru);
-			folio_putback_lru(folio);
-			continue;
-		}
-
-		if (folio_test_reclaim(folio) &&
-		    (folio_test_dirty(folio) || folio_test_writeback(folio))) {
-			/* restore LRU_REFS_FLAGS cleared by isolate_folio() */
-			if (folio_test_workingset(folio))
-				folio_set_referenced(folio);
-			continue;
-		}
-
-		if (skip_retry || folio_test_active(folio) || folio_test_referenced(folio) ||
-		    folio_mapped(folio) || folio_test_locked(folio) ||
-		    folio_test_dirty(folio) || folio_test_writeback(folio)) {
-			/* don't add rejected folios to the oldest generation */
-			set_mask_bits(&folio->flags, LRU_REFS_MASK | LRU_REFS_FLAGS,
-				      BIT(PG_active));
-			continue;
-		}
-
-		/* retry folios that may have missed folio_rotate_reclaimable() */
-		list_move(&folio->lru, &clean);
-	}
-
+	find_folios_written_back(&list, &clean, skip_retry);
 	spin_lock_irq(&lruvec->lru_lock);
 
 	move_folios_to_lru(lruvec, &list);
-- 
2.34.1