mm: workingset: add vmstat counter for shadow nodes

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

[akpm@linux-foundation.org: assert that irqs are disabled, for __inc_lruvec_page_state()]
[akpm@linux-foundation.org: s/WARN_ON_ONCE/VM_WARN_ON_ONCE/, per Johannes]
Link: http://lkml.kernel.org/r/20181009184732.762-4-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 12 insertions, 2 deletions

diff --git a/mm/workingset.c b/mm/workingset.c
index 5a72c9d5e195..7e6ef312cea5 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -377,12 +377,20 @@ void workingset_update_node(struct radix_tree_node *node)
          * already where they should be. The list_empty() test is safe
          * as node->private_list is protected by the i_pages lock.
          */
+        VM_WARN_ON_ONCE(!irqs_disabled());  /* For __inc_lruvec_page_state */
+
         if (node->count && node->count == node->exceptional) {
-                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);
+                }
         }
 }
 
@@ -473,6 +481,8 @@ 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);
 
         /*