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fs: add DiffDirChanges function to get changeset fast
Since AUFS/OverlayFS can persist changeset in diff directory, DiffDirChanges function can retrieve layer changeset from diff directory without walking the whole rootfs directory. Signed-off-by: Wei Fu <[email protected]>
1 parent 206f576 commit 8b312bd

9 files changed

+333
-39
lines changed

‎Makefile

+1-1
Original file line numberDiff line numberDiff line change
@@ -57,7 +57,7 @@ test:
5757

5858
root-test:
5959
@echo "+ $@"
60-
@go test -exec sudo ${TEST_REQUIRES_ROOT_PACKAGES} -test.root
60+
@go test -exec sudo ${TEST_REQUIRES_ROOT_PACKAGES} -test.root -test.v
6161

6262
test-compile:
6363
@echo "+ $@"

‎fs/diff.go

+63-24
Original file line numberDiff line numberDiff line change
@@ -18,6 +18,7 @@ package fs
1818

1919
import (
2020
"context"
21+
"errors"
2122
"os"
2223
"path/filepath"
2324
"strings"
@@ -102,9 +103,6 @@ func Changes(ctx context.Context, a, b string, changeFn ChangeFunc) error {
102103
if a == "" {
103104
logrus.Debugf("Using single walk diff for %s", b)
104105
return addDirChanges(ctx, changeFn, b)
105-
} else if diffOptions := detectDirDiff(b, a); diffOptions != nil {
106-
logrus.Debugf("Using single walk diff for %s from %s", diffOptions.diffDir, a)
107-
return diffDirChanges(ctx, changeFn, a, diffOptions)
108106
}
109107

110108
logrus.Debugf("Using double walk diff for %s from %s", b, a)
@@ -134,24 +132,53 @@ func addDirChanges(ctx context.Context, changeFn ChangeFunc, root string) error
134132
})
135133
}
136134

135+
// DiffChangeSource is the source of diff directory.
136+
type DiffSource int
137+
138+
const (
139+
// DiffSourceOverlayFS indicates that a diff directory is from
140+
// OverlayFS.
141+
DiffSourceOverlayFS DiffSource = iota
142+
)
143+
137144
// diffDirOptions is used when the diff can be directly calculated from
138145
// a diff directory to its base, without walking both trees.
139146
type diffDirOptions struct {
140-
diffDir string
141-
skipChange func(string) (bool, error)
142-
deleteChange func(string, string, os.FileInfo) (string, error)
147+
skipChange func(string, os.FileInfo) (bool, error)
148+
deleteChange func(string, string, os.FileInfo, ChangeFunc) (bool, error)
143149
}
144150

145-
// diffDirChanges walks the diff directory and compares changes against the base.
146-
func diffDirChanges(ctx context.Context, changeFn ChangeFunc, base string, o *diffDirOptions) error {
151+
// DiffDirChanges walks the diff directory and compares changes against the base.
152+
//
153+
// NOTE: If all the children of a dir are removed, or that dir are recreated
154+
// after remove, we will mark non-existing `.wh..opq` file as deleted. It's
155+
// unlikely to create explicit whiteout files for all the children and all
156+
// descendants. And based on OCI spec, it's not possible to create a file or
157+
// dir with a name beginning with `.wh.`. So, after `.wh..opq` file has been
158+
// deleted, the ChangeFunc, the receiver will add whiteout prefix to create a
159+
// opaque whiteout `.wh..wh..opq`.
160+
//
161+
// REF: https://github.com/opencontainers/image-spec/blob/v1.0/layer.md#whiteouts
162+
func DiffDirChanges(ctx context.Context, baseDir, diffDir string, source DiffSource, changeFn ChangeFunc) error {
163+
var o *diffDirOptions
164+
165+
switch source {
166+
case DiffSourceOverlayFS:
167+
o = &diffDirOptions{
168+
deleteChange: overlayFSWhiteoutConvert,
169+
}
170+
default:
171+
return errors.New("unknown diff change source")
172+
}
173+
147174
changedDirs := make(map[string]struct{})
148-
return filepath.Walk(o.diffDir, func(path string, f os.FileInfo, err error) error {
175+
return filepath.Walk(diffDir, func(path string, f os.FileInfo, err error) error {
149176
if err != nil {
150177
return err
151178
}
152179

153180
// Rebase path
154-
path, err = filepath.Rel(o.diffDir, path)
181+
path, err = filepath.Rel(diffDir, path)
155182
if err != nil {
156183
return err
157184
}
@@ -163,38 +190,45 @@ func diffDirChanges(ctx context.Context, changeFn ChangeFunc, base string, o *di
163190
return nil
164191
}
165192

166-
// TODO: handle opaqueness, start new double walker at this
167-
// location to get deletes, and skip tree in single walker
168-
169193
if o.skipChange != nil {
170-
if skip, err := o.skipChange(path); skip {
194+
if skip, err := o.skipChange(path, f); skip {
171195
return err
172196
}
173197
}
174198

175199
var kind ChangeKind
176200

177-
deletedFile, err := o.deleteChange(o.diffDir, path, f)
178-
if err != nil {
179-
return err
201+
deletedFile := false
202+
203+
if o.deleteChange != nil {
204+
deletedFile, err = o.deleteChange(diffDir, path, f, changeFn)
205+
if err != nil {
206+
return err
207+
}
208+
209+
_, err = os.Stat(filepath.Join(baseDir, path))
210+
if err != nil {
211+
if !os.IsNotExist(err) {
212+
return err
213+
}
214+
deletedFile = false
215+
}
180216
}
181217

182218
// Find out what kind of modification happened
183-
if deletedFile != "" {
184-
path = deletedFile
219+
if deletedFile {
185220
kind = ChangeKindDelete
186-
f = nil
187221
} else {
188222
// Otherwise, the file was added
189223
kind = ChangeKindAdd
190224

191-
// ...Unless it already existed in a base, in which case, it's a modification
192-
stat, err := os.Stat(filepath.Join(base, path))
225+
// ...Unless it already existed in a baseDir, in which case, it's a modification
226+
stat, err := os.Stat(filepath.Join(baseDir, path))
193227
if err != nil && !os.IsNotExist(err) {
194228
return err
195229
}
196230
if err == nil {
197-
// The file existed in the base, so that's a modification
231+
// The file existed in the baseDir, so that's a modification
198232

199233
// However, if it's a directory, maybe it wasn't actually modified.
200234
// If you modify /foo/bar/baz, then /foo will be part of the changed files only because it's the parent of bar
@@ -215,17 +249,22 @@ func diffDirChanges(ctx context.Context, changeFn ChangeFunc, base string, o *di
215249
if f.IsDir() {
216250
changedDirs[path] = struct{}{}
217251
}
252+
218253
if kind == ChangeKindAdd || kind == ChangeKindDelete {
219254
parent := filepath.Dir(path)
255+
220256
if _, ok := changedDirs[parent]; !ok && parent != "/" {
221-
pi, err := os.Stat(filepath.Join(o.diffDir, parent))
257+
pi, err := os.Stat(filepath.Join(diffDir, parent))
222258
if err := changeFn(ChangeKindModify, parent, pi, err); err != nil {
223259
return err
224260
}
225261
changedDirs[parent] = struct{}{}
226262
}
227263
}
228264

265+
if kind == ChangeKindDelete {
266+
f = nil
267+
}
229268
return changeFn(kind, path, f, nil)
230269
})
231270
}

‎fs/diff_linux.go

+101
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,101 @@
1+
/*
2+
Copyright The containerd Authors.
3+
4+
Licensed under the Apache License, Version 2.0 (the "License");
5+
you may not use this file except in compliance with the License.
6+
You may obtain a copy of the License at
7+
8+
http://www.apache.org/licenses/LICENSE-2.0
9+
10+
Unless required by applicable law or agreed to in writing, software
11+
distributed under the License is distributed on an "AS IS" BASIS,
12+
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13+
See the License for the specific language governing permissions and
14+
limitations under the License.
15+
*/
16+
17+
package fs
18+
19+
import (
20+
"errors"
21+
"fmt"
22+
"os"
23+
"path/filepath"
24+
"syscall"
25+
26+
"github.com/containerd/continuity/devices"
27+
"github.com/containerd/continuity/sysx"
28+
29+
"golang.org/x/sys/unix"
30+
)
31+
32+
const (
33+
// whiteoutPrefix prefix means file is a whiteout. If this is followed
34+
// by a filename this means that file has been removed from the base
35+
// layer.
36+
//
37+
// See https://github.com/opencontainers/image-spec/blob/master/layer.md#whiteouts
38+
whiteoutPrefix = ".wh."
39+
)
40+
41+
// overlayFSWhiteoutConvert detects whiteouts and opaque directories.
42+
//
43+
// It returns deleted indicator if the file is a character device with 0/0
44+
// device number. And call changeFn with ChangeKindDelete for opaque
45+
// directories.
46+
//
47+
// Check: https://www.kernel.org/doc/Documentation/filesystems/overlayfs.txt
48+
func overlayFSWhiteoutConvert(diffDir, path string, f os.FileInfo, changeFn ChangeFunc) (deleted bool, _ error) {
49+
if f.Mode()&os.ModeCharDevice != 0 {
50+
if _, ok := f.Sys().(*syscall.Stat_t); !ok {
51+
return false, nil
52+
}
53+
54+
maj, min, err := devices.DeviceInfo(f)
55+
if err != nil {
56+
return false, err
57+
}
58+
return (maj == 0 && min == 0), nil
59+
}
60+
61+
if f.IsDir() {
62+
originalPath := filepath.Join(diffDir, path)
63+
opaque, err := getOpaqueValue(originalPath)
64+
if err != nil {
65+
if errors.Is(err, unix.ENODATA) {
66+
return false, nil
67+
}
68+
return false, err
69+
}
70+
71+
if len(opaque) == 1 && opaque[0] == 'y' {
72+
opaqueDirPath := filepath.Join(path, whiteoutPrefix+".opq")
73+
return false, changeFn(ChangeKindDelete, opaqueDirPath, nil, nil)
74+
}
75+
}
76+
return false, nil
77+
}
78+
79+
// getOpaqueValue returns opaque value for a given file.
80+
func getOpaqueValue(filePath string) ([]byte, error) {
81+
for _, xattr := range []string{
82+
"trusted.overlay.opaque",
83+
// TODO(fuweid):
84+
//
85+
// user.overlay.* is available since 5.11. We should check
86+
// kernel version before read.
87+
//
88+
// REF: https://github.com/torvalds/linux/commit/2d2f2d7322ff43e0fe92bf8cccdc0b09449bf2e1
89+
"user.overlay.opaque",
90+
} {
91+
opaque, err := sysx.LGetxattr(filePath, xattr)
92+
if err != nil {
93+
if errors.Is(err, unix.ENODATA) || errors.Is(err, unix.ENOTSUP) {
94+
continue
95+
}
96+
return nil, fmt.Errorf("failed to retrieve %s attr: %w", xattr, err)
97+
}
98+
return opaque, nil
99+
}
100+
return nil, unix.ENODATA
101+
}

‎fs/diff_nonlinux.go

+29
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,29 @@
1+
//go:build !linux
2+
// +build !linux
3+
4+
/*
5+
Copyright The containerd Authors.
6+
7+
Licensed under the Apache License, Version 2.0 (the "License");
8+
you may not use this file except in compliance with the License.
9+
You may obtain a copy of the License at
10+
11+
http://www.apache.org/licenses/LICENSE-2.0
12+
13+
Unless required by applicable law or agreed to in writing, software
14+
distributed under the License is distributed on an "AS IS" BASIS,
15+
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16+
See the License for the specific language governing permissions and
17+
limitations under the License.
18+
*/
19+
20+
package fs
21+
22+
import (
23+
"errors"
24+
"os"
25+
)
26+
27+
func overlayFSWhiteoutConvert(string, string, os.FileInfo, ChangeFunc) (bool, error) {
28+
return false, errors.New("unsupported")
29+
}

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