Merge pull request #9151 from tonistiigi/aufs-clipping-fix

Fix AUFS silent mount errors on many layers

daemon/graphdriver/aufs/aufs.go

@@ -412,39 +412,44 @@ func (a *Driver) aufsMount(ro []string, rw, target, mountLabel string) (err erro
 		}
 	}()
 
-	if err = a.tryMount(ro, rw, target, mountLabel); err != nil {
-		if err = a.mountRw(rw, target, mountLabel); err != nil {
-			return
+	// Mount options are clipped to page size(4096 bytes). If there are more
+	// layers then these are remounted individually using append.
+
+	b := make([]byte, syscall.Getpagesize()-len(mountLabel)-50) // room for xino & mountLabel
+	bp := copy(b, fmt.Sprintf("br:%s=rw", rw))
+
+	firstMount := true
+	i := 0
+
+	for {
+		for ; i < len(ro); i++ {
+			layer := fmt.Sprintf(":%s=ro+wh", ro[i])
+
+			if firstMount {
+				if bp+len(layer) > len(b) {
+					break
+				}
+				bp += copy(b[bp:], layer)
+			} else {
+				data := label.FormatMountLabel(fmt.Sprintf("append%s", layer), mountLabel)
+				if err = mount("none", target, "aufs", MsRemount, data); err != nil {
+					return
+				}
+			}
 		}
 
-		for _, layer := range ro {
-			data := label.FormatMountLabel(fmt.Sprintf("append:%s=ro+wh", layer), mountLabel)
-			if err = mount("none", target, "aufs", MsRemount, data); err != nil {
+		if firstMount {
+			data := label.FormatMountLabel(fmt.Sprintf("%s,xino=/dev/shm/aufs.xino", string(b[:bp])), mountLabel)
+			if err = mount("none", target, "aufs", 0, data); err != nil {
 				return
 			}
+			firstMount = false
 		}
-	}
-	return
-}
-
-// Try to mount using the aufs fast path, if this fails then
-// append ro layers.
-func (a *Driver) tryMount(ro []string, rw, target, mountLabel string) (err error) {
-	var (
-		rwBranch   = fmt.Sprintf("%s=rw", rw)
-		roBranches = fmt.Sprintf("%s=ro+wh:", strings.Join(ro, "=ro+wh:"))
-		data       = label.FormatMountLabel(fmt.Sprintf("br:%v:%v,xino=/dev/shm/aufs.xino", rwBranch, roBranches), mountLabel)
-	)
-	return mount("none", target, "aufs", 0, data)
-}
-
-func (a *Driver) mountRw(rw, target, mountLabel string) error {
-	data := label.FormatMountLabel(fmt.Sprintf("br:%s,xino=/dev/shm/aufs.xino", rw), mountLabel)
-	return mount("none", target, "aufs", 0, data)
-}
 
-func rollbackMount(target string, err error) {
-	if err != nil {
-		Unmount(target)
+		if i == len(ro) {
+			break
+		}
 	}
+
+	return
 }

daemon/graphdriver/aufs/aufs_test.go

@@ -635,9 +635,13 @@ func hash(c string) string {
 	return hex.EncodeToString(h.Sum(nil))
 }
 
-func TestMountMoreThan42Layers(t *testing.T) {
-	d := newDriver(t)
-	defer os.RemoveAll(tmp)
+func testMountMoreThan42Layers(t *testing.T, mountPath string) {
+	if err := os.MkdirAll(mountPath, 0755); err != nil {
+		t.Fatal(err)
+	}
+
+	d := testInit(mountPath, t).(*Driver)
+	defer os.RemoveAll(mountPath)
 	defer d.Cleanup()
 	var last string
 	var expected int
@@ -695,3 +699,25 @@ func TestMountMoreThan42Layers(t *testing.T) {
 		t.Fatalf("Expected %d got %d", expected, len(files))
 	}
 }
+
+func TestMountMoreThan42Layers(t *testing.T) {
+	testMountMoreThan42Layers(t, tmp)
+}
+
+func TestMountMoreThan42LayersMatchingPathLength(t *testing.T) {
+	tmp := "aufs-tests"
+	for {
+		// This finds a mount path so that when combined into aufs mount options
+		// 4096 byte boundary would be in between the paths or in permission
+		// section. For '/tmp' it will use '/tmp/aufs-tests00000000/aufs'
+		mountPath := path.Join(os.TempDir(), tmp, "aufs")
+		pathLength := 77 + len(mountPath)
+
+		if mod := 4095 % pathLength; mod == 0 || mod > pathLength-2 {
+			t.Logf("Using path: %s", mountPath)
+			testMountMoreThan42Layers(t, mountPath)
+			return
+		}
+		tmp += "0"
+	}
+}