13 "github.com/Sirupsen/logrus"
14 "github.com/docker/docker/pkg/system"
15 "github.com/pkg/errors"
18 // hasOpaqueCopyUpBug checks whether the filesystem has a bug
19 // which copies up the opaque flag when copying up an opaque
20 // directory. When this bug exists naive diff should be used.
21 func hasOpaqueCopyUpBug(d string) error {
22 td, err := ioutil.TempDir(d, "opaque-bug-check")
27 if err := os.RemoveAll(td); err != nil {
28 logrus.Warnf("Failed to remove check directory %v: %v", td, err)
32 // Make directories l1/d, l2/d, l3, work, merged
33 if err := os.MkdirAll(filepath.Join(td, "l1", "d"), 0755); err != nil {
36 if err := os.MkdirAll(filepath.Join(td, "l2", "d"), 0755); err != nil {
39 if err := os.Mkdir(filepath.Join(td, "l3"), 0755); err != nil {
42 if err := os.Mkdir(filepath.Join(td, "work"), 0755); err != nil {
45 if err := os.Mkdir(filepath.Join(td, "merged"), 0755); err != nil {
49 // Mark l2/d as opaque
50 if err := system.Lsetxattr(filepath.Join(td, "l2", "d"), "trusted.overlay.opaque", []byte("y"), 0); err != nil {
51 return errors.Wrap(err, "failed to set opaque flag on middle layer")
54 opts := fmt.Sprintf("lowerdir=%s:%s,upperdir=%s,workdir=%s", path.Join(td, "l2"), path.Join(td, "l1"), path.Join(td, "l3"), path.Join(td, "work"))
55 if err := syscall.Mount("overlay", filepath.Join(td, "merged"), "overlay", 0, opts); err != nil {
56 return errors.Wrap(err, "failed to mount overlay")
59 if err := syscall.Unmount(filepath.Join(td, "merged"), 0); err != nil {
60 logrus.Warnf("Failed to unmount check directory %v: %v", filepath.Join(td, "merged"), err)
64 // Touch file in d to force copy up of opaque directory "d" from "l2" to "l3"
65 if err := ioutil.WriteFile(filepath.Join(td, "merged", "d", "f"), []byte{}, 0644); err != nil {
66 return errors.Wrap(err, "failed to write to merged directory")
69 // Check l3/d does not have opaque flag
70 xattrOpaque, err := system.Lgetxattr(filepath.Join(td, "l3", "d"), "trusted.overlay.opaque")
72 return errors.Wrap(err, "failed to read opaque flag on upper layer")
74 if string(xattrOpaque) == "y" {
75 return errors.New("opaque flag erroneously copied up, consider update to kernel 4.8 or later to fix")