[PATCH v2] mm: swap: add back full cluster when no entry is reclaimed

[Kemeng Shi]

If no swap cache is reclaimed, cluster taken off from full_clusters list
will not be put in any list and we can't reclaime HAS_CACHE slots
efficiently. Do relocate_cluster for such cluster to avoid inefficiency.

Fixes: 3b644773eefda ("mm, swap: reduce contention on device lock")
Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
Reviewed-by: Kairui Song <kasong@xxxxxxxxxxx>
---
 mm/swapfile.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 34baefb000b5..e5f58ab86329 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -861,6 +861,10 @@ static void swap_reclaim_full_clusters(struct swap_info_struct *si, bool force)
 			offset++;
 		}
 
+		/* in case no swap cache is reclaimed */
+		if (ci->flags == CLUSTER_FLAG_NONE)
+			relocate_cluster(si, ci);
+
 		unlock_cluster(ci);
 		if (to_scan <= 0)
 			break;
-- 
2.30.0