[PATCH v5 1/5] mm/vmscan: introduce folio_activate_locked() helper

[Zhang Peng <zippermonkey@icloud.com>]

The activate_locked label in shrink_folio_list() reclaims swap cache
when needed, marks the folio active, and updates activation statistics.
Extract this block into folio_activate_locked() so it can be reused.

No functional change.

Signed-off-by: Zhang Peng <bruzzhang@tencent.com>
---
 mm/vmscan.c | 38 +++++++++++++++++++++++++++-----------
 1 file changed, 27 insertions(+), 11 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index ca4533eba701..5ba880dce21e 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1050,6 +1050,32 @@ static bool may_enter_fs(struct folio *folio, gfp_t gfp_mask)
 	return !data_race(folio_swap_flags(folio) & SWP_FS_OPS);
 }
 
+/*
+ * Prepare a locked folio to be kept active rather than reclaimed.
+ * Reclaims its swap slot if it will not be swapped, then marks it
+ * active and updates activation statistics.
+ */
+static void folio_activate_locked(struct folio *folio,
+		struct reclaim_stat *stat)
+{
+	unsigned int nr_pages = folio_nr_pages(folio);
+
+	VM_WARN_ON_ONCE_FOLIO(!folio_test_locked(folio), folio);
+	VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio);
+
+	/* Not a candidate for swapping, so reclaim swap space. */
+	if (folio_test_swapcache(folio) &&
+	    (mem_cgroup_swap_full(folio) || folio_test_mlocked(folio)))
+		folio_free_swap(folio);
+	if (!folio_test_mlocked(folio)) {
+		int type = folio_is_file_lru(folio);
+
+		folio_set_active(folio);
+		stat->nr_activate[type] += nr_pages;
+		count_memcg_folio_events(folio, PGACTIVATE, nr_pages);
+	}
+}
+
 /*
  * shrink_folio_list() returns the number of reclaimed pages
  */
@@ -1525,17 +1551,7 @@ static unsigned int shrink_folio_list(struct list_head *folio_list,
 			nr_pages = 1;
 		}
 activate_locked:
-		/* Not a candidate for swapping, so reclaim swap space. */
-		if (folio_test_swapcache(folio) &&
-		    (mem_cgroup_swap_full(folio) || folio_test_mlocked(folio)))
-			folio_free_swap(folio);
-		VM_BUG_ON_FOLIO(folio_test_active(folio), folio);
-		if (!folio_test_mlocked(folio)) {
-			int type = folio_is_file_lru(folio);
-			folio_set_active(folio);
-			stat->nr_activate[type] += nr_pages;
-			count_memcg_folio_events(folio, PGACTIVATE, nr_pages);
-		}
+		folio_activate_locked(folio, stat);
 keep_locked:
 		folio_unlock(folio);
 keep:

-- 
2.43.7