libctr/fs2: best effort collect memory stats

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

libcontainer/cgroups/fs2/memory.go

@@ -154,16 +154,23 @@ func getMemoryDataV2(path, name string) (cgroups.MemoryData, error) {
 		},
 	}
 
+	var lastErr error
 	for _, f := range files {
 		value, err := fscommon.GetCgroupParamUint(path, f.name)
 		if err != nil {
-			if name != "" && os.IsNotExist(err) {
+			if os.IsNotExist(err) {
+				// Peak usage is only available since kernel v5.14, so collect best-effort.
+				if strings.HasSuffix(v.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.
-				return cgroups.MemoryData{}, nil
+				if name == "swap" {
+					return cgroups.MemoryData{}, nil
+				}
 			}
-			return cgroups.MemoryData{}, err
+			return memoryData, err
 		}
 		*f.value = value
 	}

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())
 	}
 }