[PATCH 3/4] mm: workingset: add vmstat counter for shadow nodes

[Johannes Weiner <hannes@cmpxchg.org>]

Make it easier to catch bugs in the shadow node shrinker by adding a
counter for the shadow nodes in circulation.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
 include/linux/mmzone.h |  1 +
 mm/vmstat.c            |  1 +
 mm/workingset.c        | 12 ++++++++++--
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 4179e67add3d..d82e80d82aa6 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -161,6 +161,7 @@ enum node_stat_item {
 	NR_SLAB_UNRECLAIMABLE,
 	NR_ISOLATED_ANON,	/* Temporary isolated pages from anon lru */
 	NR_ISOLATED_FILE,	/* Temporary isolated pages from file lru */
+	WORKINGSET_NODES,
 	WORKINGSET_REFAULT,
 	WORKINGSET_ACTIVATE,
 	WORKINGSET_RESTORE,
diff --git a/mm/vmstat.c b/mm/vmstat.c
index d08ed044759d..6038ce593ce3 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1143,6 +1143,7 @@ const char * const vmstat_text[] = {
 	"nr_slab_unreclaimable",
 	"nr_isolated_anon",
 	"nr_isolated_file",
+	"workingset_nodes",
 	"workingset_refault",
 	"workingset_activate",
 	"workingset_restore",
diff --git a/mm/workingset.c b/mm/workingset.c
index f564aaa6b71d..cfdf6adf7e7c 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -378,11 +378,17 @@ void workingset_update_node(struct xa_node *node)
 	 * as node->private_list is protected by the i_pages lock.
 	 */
 	if (node->count && node->count == node->nr_values) {
-		if (list_empty(&node->private_list))
+		if (list_empty(&node->private_list)) {
 			list_lru_add(&shadow_nodes, &node->private_list);
+			__inc_lruvec_page_state(virt_to_page(node),
+						WORKINGSET_NODES);
+		}
 	} else {
-		if (!list_empty(&node->private_list))
+		if (!list_empty(&node->private_list)) {
 			list_lru_del(&shadow_nodes, &node->private_list);
+			__dec_lruvec_page_state(virt_to_page(node),
+						WORKINGSET_NODES);
+		}
 	}
 }
 
@@ -472,6 +478,8 @@ static enum lru_status shadow_lru_isolate(struct list_head *item,
 	}
 
 	list_lru_isolate(lru, item);
+	__dec_lruvec_page_state(virt_to_page(node), WORKINGSET_NODES);
+
 	spin_unlock(lru_lock);
 
 	/*
-- 
2.19.0