Add direct unpack support for overlay and aufs

Signed-off-by: Lantao Liu <lantaol@google.com>

diff/apply/apply.go

@@ -19,10 +19,8 @@ package apply
 import (
 	"context"
 	"io"
-	"io/ioutil"
 	"time"
 
-	"github.com/containerd/containerd/archive"
 	"github.com/containerd/containerd/content"
 	"github.com/containerd/containerd/diff"
 	"github.com/containerd/containerd/log"
@@ -94,15 +92,8 @@ func (s *fsApplier) Apply(ctx context.Context, desc ocispec.Descriptor, mounts [
 	rc := &readCounter{
 		r: io.TeeReader(processor, digester.Hash()),
 	}
-	if err := mount.WithTempMount(ctx, mounts, func(root string) error {
-		if _, err := archive.Apply(ctx, root, rc); err != nil {
-			return err
-		}
 
-		// Read any trailing data
-		_, err := io.Copy(ioutil.Discard, rc)
-		return err
-	}); err != nil {
+	if err := apply(ctx, mounts, rc); err != nil {
 		return emptyDesc, err
 	}
 

diff/apply/apply_linux.go

@@ -0,0 +1,90 @@
+// +build linux
+
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package apply
+
+import (
+	"context"
+	"io"
+	"strings"
+
+	"github.com/containerd/containerd/archive"
+	"github.com/containerd/containerd/mount"
+	"github.com/pkg/errors"
+)
+
+func apply(ctx context.Context, mounts []mount.Mount, r io.Reader) error {
+	switch {
+	case len(mounts) == 1 && mounts[0].Type == "overlay":
+		path, err := getOverlayPath(mounts[0].Options)
+		if err != nil {
+			return err
+		}
+		_, err = archive.Apply(ctx, path, r,
+			archive.WithConvertWhiteout(archive.OverlayConvertWhiteout))
+		return err
+	case len(mounts) == 1 && mounts[0].Type == "aufs":
+		path, err := getAufsPath(mounts[0].Options)
+		if err != nil {
+			return err
+		}
+		_, err = archive.Apply(ctx, path, r,
+			archive.WithConvertWhiteout(archive.AufsConvertWhiteout))
+		return err
+	default:
+		return mount.WithTempMount(ctx, mounts, func(root string) error {
+			_, err := archive.Apply(ctx, root, r)
+			return err
+		})
+	}
+}
+
+func getOverlayPath(options []string) (string, error) {
+	const upperdirPrefix = "upperdir="
+	for _, o := range options {
+		if strings.HasPrefix(o, upperdirPrefix) {
+			return strings.TrimPrefix(o, upperdirPrefix), nil
+		}
+	}
+	return "", errors.New("upperdir not found")
+}
+
+func getAufsPath(options []string) (string, error) {
+	const (
+		sep       = ":"
+		brPrefix1 = "br:"
+		brPrefix2 = "br="
+		rwSuffix  = "=rw"
+	)
+	for _, o := range options {
+		if strings.HasPrefix(o, brPrefix1) {
+			o = strings.TrimPrefix(o, brPrefix1)
+		} else if strings.HasPrefix(o, brPrefix2) {
+			o = strings.TrimPrefix(o, brPrefix2)
+		} else {
+			continue
+		}
+		for _, b := range strings.Split(o, sep) {
+			if strings.HasSuffix(b, rwSuffix) {
+				return strings.TrimSuffix(b, rwSuffix), nil
+			}
+		}
+		break
+	}
+	return "", errors.New("rw branch not found")
+}

diff/apply/apply_linux_test.go

@@ -0,0 +1,79 @@
+// +build linux
+
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package apply
+
+import (
+	"testing"
+)
+
+func TestGetOverlayPath(t *testing.T) {
+	good := []string{"upperdir=/test/upper", "lowerdir=/test/lower", "workdir=/test/work"}
+	path, err := getOverlayPath(good)
+	if err != nil {
+		t.Fatalf("Get overlay path failed: %v", err)
+	}
+	if path != "/test/upper" {
+		t.Fatalf("Unexpected upperdir: %q", path)
+	}
+
+	bad := []string{"lowerdir=/test/lower"}
+	_, err = getOverlayPath(bad)
+	if err == nil {
+		t.Fatalf("An error is expected")
+	}
+}
+
+func TestGetAufsPath(t *testing.T) {
+	rwDir := "/test/rw"
+	for _, test := range []struct {
+		options   []string
+		expectErr bool
+	}{
+		{
+			options:   []string{"random:option", "br:" + rwDir + "=rw:/test/ro=ro+wh"},
+			expectErr: false,
+		},
+		{
+			options:   []string{"random:option", "br=" + rwDir + "=rw:/test/ro=ro+wh"},
+			expectErr: false,
+		},
+		{
+			options:   []string{"random:option"},
+			expectErr: true,
+		},
+		{
+			options:   []string{"br:/test/ro=ro+wh"},
+			expectErr: true,
+		},
+	} {
+		path, err := getAufsPath(test.options)
+		if test.expectErr {
+			if err == nil {
+				t.Fatalf("An error is expected")
+			}
+			continue
+		}
+		if err != nil {
+			t.Fatalf("Get aufs path failed: %v", err)
+		}
+		if path != rwDir {
+			t.Fatalf("Unexpected rw dir: %q", path)
+		}
+	}
+}

diff/apply/apply_other.go

@@ -0,0 +1,34 @@
+// +build !linux
+
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package apply
+
+import (
+	"context"
+	"io"
+
+	"github.com/containerd/containerd/archive"
+	"github.com/containerd/containerd/mount"
+)
+
+func apply(ctx context.Context, mounts []mount.Mount, r io.Reader) error {
+	return mount.WithTempMount(ctx, mounts, func(root string) error {
+		_, err := archive.Apply(ctx, root, r)
+		return err
+	})
+}