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

Andrew Morton
2018-10-09T22:08:49Z

On Tue, 9 Oct 2018 14:47:32 -0400 Johannes Weiner <hannes@cmpxchg.org> wrote:

> --- 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);
> + }
> }
> }

A bit worried that we're depending on the caller's caller to have
disabled interrupts to avoid subtle and rare errors.

Can we do this?

--- a/mm/workingset.c~mm-workingset-add-vmstat-counter-for-shadow-nodes-fix
+++ a/mm/workingset.c
@@ -377,6 +377,8 @@ void workingset_update_node(struct radix
* already where they should be. The list_empty() test is safe
* as node->private_list is protected by the i_pages lock.
*/
+ WARN_ON_ONCE(!irqs_disabled()); /* For __inc_lruvec_page_state */
+
if (node->count && node->count == node->exceptional) {
if (list_empty(&node->private_list)) {
list_lru_add(&shadow_nodes, &node->private_list);
_