libcontainer: cgroups: deal with unlimited case for pids.max

libcontainer/cgroups/fs/pids.go

@@ -4,6 +4,7 @@ package fs
 
 import (
 	"fmt"
+	"path/filepath"
 	"strconv"
 
 	"github.com/opencontainers/runc/libcontainer/cgroups"
@@ -52,12 +53,21 @@ func (s *PidsGroup) GetStats(path string, stats *cgroups.Stats) error {
 		return fmt.Errorf("failed to parse pids.current - %s", err)
 	}
 
-	max, err := getCgroupParamUint(path, "pids.max")
+	maxString, err := getCgroupParamString(path, "pids.max")
 	if err != nil {
 		return fmt.Errorf("failed to parse pids.max - %s", err)
 	}
 
+	// Default if pids.max == "max" is 0 -- which represents "no limit".
+	var max uint64
+	if maxString != "max" {
+		max, err = parseUint(maxString, 10, 64)
+		if err != nil {
+			return fmt.Errorf("failed to parse pids.max - unable to parse %q as a uint from Cgroup file %q", maxString, filepath.Join(path, "pids.max"))
+		}
+	}
+
 	stats.PidsStats.Current = current
-	stats.PidsStats.Max = max
+	stats.PidsStats.Limit = max
 	return nil
 }

libcontainer/cgroups/fs/pids_test.go

@@ -81,7 +81,31 @@ func TestPidsStats(t *testing.T) {
 		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)
+	if stats.PidsStats.Limit != maxLimited {
+		t.Fatalf("Expected %d, got %d for pids.max", maxLimited, stats.PidsStats.Limit)
+	}
+}
+
+func TestPidsStatsUnlimited(t *testing.T) {
+	helper := NewCgroupTestUtil("pids", t)
+	defer helper.cleanup()
+
+	helper.writeFileContents(map[string]string{
+		"pids.current": strconv.Itoa(4096),
+		"pids.max":     "max",
+	})
+
+	pids := &PidsGroup{}
+	stats := *cgroups.NewStats()
+	if err := pids.GetStats(helper.CgroupPath, &stats); err != nil {
+		t.Fatal(err)
+	}
+
+	if stats.PidsStats.Current != 4096 {
+		t.Fatalf("Expected %d, got %d for pids.current", 4096, stats.PidsStats.Current)
+	}
+
+	if stats.PidsStats.Limit != 0 {
+		t.Fatalf("Expected %d, got %d for pids.max", 0, stats.PidsStats.Limit)
 	}
 }

libcontainer/cgroups/stats.go

@@ -55,7 +55,7 @@ type PidsStats struct {
 	// number of pids in the cgroup
 	Current uint64 `json:"current,omitempty"`
 	// active pids hard limit
-	Max uint64 `json:"max,omitempty"`
+	Limit uint64 `json:"limit,omitempty"`
 }
 
 type BlkioStatEntry struct {