[PATCH v5 20/36] mm/memcontrol: account private-node memory in per-node stats

[Gregory Price <gourry@gourry.net>]

Private nodes folios are charged like any other - the node's per-cpu
lruvec counters are increment even for N_MEMORY_PRIVATE.

The memcg-level totals in memory.stat therefore include this memory,
but the per-node views do not:

  - mem_cgroup_css_rstat_flush() folds the per-node percpu deltas into the
    aggregate only for N_MEMORY nodes, so a private node's lruvec aggregate
    is never refreshed.

  - memory.numa_stat (v2) and the v1 numa_stat skip private nodes, so they
    never emit an Nx= field for one.

So memory.numa_stat does not sum to memory.stat once a cgroup has memory
on a private node.

Include N_MEMORY_PRIVATE in the flush/display process so private-node
memory is folded in and reported per node.

This is pure accounting of memory that already exists and is already
charged, so it is unconditional - regardless of future capabilities.

Signed-off-by: Gregory Price <gourry@gourry.net>
---
 mm/memcontrol-v1.c |  8 ++++++--
 mm/memcontrol.c    | 11 +++++++++--
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c
index 2dc599484d006..5e464e52dfb9a 100644
--- a/mm/memcontrol-v1.c
+++ b/mm/memcontrol-v1.c
@@ -2132,14 +2132,18 @@ static int memcg_numa_stat_show(struct seq_file *m, void *v)
 	const struct numa_stat *stat;
 	int nid;
 	struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
+	nodemask_t reportable;
 
 	mem_cgroup_flush_stats(memcg);
 
+	/* Private nodes hold cgroup memory too, report them. */
+	nodes_or(reportable, node_states[N_MEMORY], node_states[N_MEMORY_PRIVATE]);
+
 	for (stat = stats; stat < ARRAY_END(stats); stat++) {
 		seq_printf(m, "%s=%lu", stat->name,
 			   mem_cgroup_nr_lru_pages(memcg, stat->lru_mask,
 						   false));
-		for_each_node_state(nid, N_MEMORY)
+		for_each_node_mask(nid, reportable)
 			seq_printf(m, " N%d=%lu", nid,
 				   mem_cgroup_node_nr_lru_pages(memcg, nid,
 							stat->lru_mask, false));
@@ -2151,7 +2155,7 @@ static int memcg_numa_stat_show(struct seq_file *m, void *v)
 		seq_printf(m, "hierarchical_%s=%lu", stat->name,
 			   mem_cgroup_nr_lru_pages(memcg, stat->lru_mask,
 						   true));
-		for_each_node_state(nid, N_MEMORY)
+		for_each_node_mask(nid, reportable)
 			seq_printf(m, " N%d=%lu", nid,
 				   mem_cgroup_node_nr_lru_pages(memcg, nid,
 							stat->lru_mask, true));
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f0dde52dc9e0e..4d79e238bc57d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4496,6 +4496,7 @@ static void mem_cgroup_css_rstat_flush(struct cgroup_subsys_state *css, int cpu)
 	struct mem_cgroup *parent = parent_mem_cgroup(memcg);
 	struct memcg_vmstats_percpu *statc;
 	struct aggregate_control ac;
+	nodemask_t reportable;
 	int nid;
 
 	flush_nmi_stats(memcg, parent);
@@ -4524,7 +4525,9 @@ static void mem_cgroup_css_rstat_flush(struct cgroup_subsys_state *css, int cpu)
 	};
 	mem_cgroup_stat_aggregate(&ac);
 
-	for_each_node_state(nid, N_MEMORY) {
+	/* Private nodes must also be accounted or numa_stat is misleading */
+	nodes_or(reportable, node_states[N_MEMORY], node_states[N_MEMORY_PRIVATE]);
+	for_each_node_mask(nid, reportable) {
 		struct mem_cgroup_per_node *pn = memcg->nodeinfo[nid];
 		struct lruvec_stats *lstats = pn->lruvec_stats;
 		struct lruvec_stats *plstats = NULL;
@@ -4947,9 +4950,13 @@ static int memory_numa_stat_show(struct seq_file *m, void *v)
 {
 	int i;
 	struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
+	nodemask_t reportable;
 
 	mem_cgroup_flush_stats(memcg);
 
+	/* Private nodes hold cgroup memory too, report them. */
+	nodes_or(reportable, node_states[N_MEMORY], node_states[N_MEMORY_PRIVATE]);
+
 	for (i = 0; i < ARRAY_SIZE(memory_stats); i++) {
 		int nid;
 
@@ -4957,7 +4964,7 @@ static int memory_numa_stat_show(struct seq_file *m, void *v)
 			continue;
 
 		seq_printf(m, "%s", memory_stats[i].name);
-		for_each_node_state(nid, N_MEMORY) {
+		for_each_node_mask(nid, reportable) {
 			u64 size;
 			struct lruvec *lruvec;
 
-- 
2.53.0-Meta