libctr/fs2: Initialize MaxUsage field with memory.peak value

as well as rework the function to reduce duplication, and update the test for it

Signed-off-by: Peter Hunt <[email protected]>

libcontainer/cgroups/fs2/memory.go

@@ -136,26 +136,43 @@ func getMemoryDataV2(path, name string) (cgroups.MemoryData, error) {
 	if name != "" {
 		moduleName = "memory." + name
 	}
-	usage := moduleName + ".current"
-	limit := moduleName + ".max"
-
-	value, err := fscommon.GetCgroupParamUint(path, usage)
-	if err != nil {
-		if name != "" && os.IsNotExist(err) {
-			// Ignore EEXIST as there's no swap accounting
-			// if kernel CONFIG_MEMCG_SWAP is not set or
-			// swapaccount=0 kernel boot parameter is given.
-			return cgroups.MemoryData{}, nil
+	files := []struct {
+		name  string
+		value *uint64
+	}{
+		{
+			name:  moduleName + ".current",
+			value: &memoryData.Usage,
+		},
+		{
+			name:  moduleName + ".max",
+			value: &memoryData.Limit,
+		},
+		{
+			name:  moduleName + ".peak",
+			value: &memoryData.MaxUsage,
+		},
+	}
+
+	for _, f := range files {
+		value, err := fscommon.GetCgroupParamUint(path, f.name)
+		if err != nil {
+			if os.IsNotExist(err) {
+				// Peak usage is only available since kernel v5.14, so collect best-effort.
+				if strings.HasSuffix(f.name, "peak") {
+					continue
+				}
+				// Ignore EEXIST as there's no swap accounting
+				// if kernel CONFIG_MEMCG_SWAP is not set or
+				// swapaccount=0 kernel boot parameter is given.
+				if name == "swap" {
+					return cgroups.MemoryData{}, nil
+				}
+			}
+			return memoryData, err
 		}
-		return cgroups.MemoryData{}, err
-	}
-	memoryData.Usage = value
-
-	value, err = fscommon.GetCgroupParamUint(path, limit)
-	if err != nil {
-		return cgroups.MemoryData{}, err
+		*f.value = value
 	}
-	memoryData.Limit = value
 
 	return memoryData, nil
 }

libcontainer/cgroups/fs2/memory_test.go

@@ -71,7 +71,7 @@ func TestStatMemoryPodCgroupNotFound(t *testing.T) {
 		t.Errorf("expected error when statting memory for cgroupv2 root, but was nil")
 	}
 
-	if !strings.Contains(err.Error(), "memory.current: no such file or directory") {
+	if !strings.Contains(err.Error(), "memory.peak: no such file or directory") {
 		t.Errorf("expected error to contain 'memory.current: no such file or directory', but was %s", err.Error())
 	}
 }
@@ -94,6 +94,10 @@ func TestStatMemoryPodCgroup(t *testing.T) {
 		t.Fatal(err)
 	}
 
+	if err := os.WriteFile(filepath.Join(fakeCgroupDir, "memory.peak"), []byte("10000000000000"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
 	gotStats := cgroups.NewStats()
 
 	// use a fake root path to trigger the pod cgroup lookup.
@@ -107,6 +111,16 @@ func TestStatMemoryPodCgroup(t *testing.T) {
 	if gotStats.MemoryStats.Usage.Usage != expectedUsageBytes {
 		t.Errorf("parsed cgroupv2 memory.stat doesn't match expected result: \ngot %#v\nexpected %#v\n", gotStats.MemoryStats.Usage.Usage, expectedUsageBytes)
 	}
+
+	var expectedLimitBytes uint64 = 999999999
+	if gotStats.MemoryStats.Usage.Limit != expectedLimitBytes {
+		t.Errorf("parsed cgroupv2 memory.stat doesn't match expected result: \ngot %#v\nexpected %#v\n", gotStats.MemoryStats.Usage.Limit, expectedLimitBytes)
+	}
+
+	var expectedMaxUsageBytes uint64 = 10000000000000
+	if gotStats.MemoryStats.Usage.MaxUsage != expectedMaxUsageBytes {
+		t.Errorf("parsed cgroupv2 memory.stat doesn't match expected result: \ngot %#v\nexpected %#v\n", gotStats.MemoryStats.Usage.MaxUsage, expectedMaxUsageBytes)
+	}
 }
 
 func TestRootStatsFromMeminfo(t *testing.T) {