libctr/fs2: best effort collect memory stats

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

libcontainer/cgroups/fs2/memory.go

@@ -154,21 +154,22 @@ 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) {
 				// 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
+				continue
 			}
-			return cgroups.MemoryData{}, err
+			lastErr = err
 		}
 		*f.value = value
 	}
 
-	return memoryData, nil
+	return memoryData, lastErr
 }
 
 func rootStatsFromMeminfo(stats *cgroups.Stats) error {

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())
 	}
 }