libcontainer: cgroups: add pids.max to PidsStats

libcontainer/cgroups/fs/pids.go

@@ -47,11 +47,17 @@ func (s *PidsGroup) Remove(d *cgroupData) error {
 }
 
 func (s *PidsGroup) GetStats(path string, stats *cgroups.Stats) error {
-	value, err := getCgroupParamUint(path, "pids.current")
+	current, err := getCgroupParamUint(path, "pids.current")
 	if err != nil {
 		return fmt.Errorf("failed to parse pids.current - %s", err)
 	}
 
-	stats.PidsStats.Current = value
+	max, err := getCgroupParamUint(path, "pids.max")
+	if err != nil {
+		return fmt.Errorf("failed to parse pids.max - %s", err)
+	}
+
+	stats.PidsStats.Current = current
+	stats.PidsStats.Max = max
 	return nil
 }

libcontainer/cgroups/fs/pids_test.go

@@ -80,4 +80,8 @@ func TestPidsStats(t *testing.T) {
 	if stats.PidsStats.Current != 1337 {
 		t.Fatalf("Expected %d, got %d for pids.current", 1337, stats.PidsStats.Current)
 	}
+
+	if stats.PidsStats.Max != maxLimited {
+		t.Fatalf("Expected %d, got %d for pids.max", maxLimited, stats.PidsStats.Max)
+	}
 }

libcontainer/cgroups/stats.go

@@ -54,6 +54,8 @@ type MemoryStats struct {
 type PidsStats struct {
 	// number of pids in the cgroup
 	Current uint64 `json:"current,omitempty"`
+	// active pids hard limit
+	Max uint64 `json:"max,omitempty"`
 }
 
 type BlkioStatEntry struct {