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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 <fuweid89@gmail.com>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,101 @@ | ||
| /* | ||
| 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 fs | ||
|
|
||
| import ( | ||
| "errors" | ||
| "fmt" | ||
| "os" | ||
| "path/filepath" | ||
| "syscall" | ||
|
|
||
| "github.com/containerd/continuity/devices" | ||
| "github.com/containerd/continuity/sysx" | ||
|
|
||
| "golang.org/x/sys/unix" | ||
| ) | ||
|
|
||
| const ( | ||
| // whiteoutPrefix prefix means file is a whiteout. If this is followed | ||
| // by a filename this means that file has been removed from the base | ||
| // layer. | ||
| // | ||
| // See https://github.com/opencontainers/image-spec/blob/master/layer.md#whiteouts | ||
| whiteoutPrefix = ".wh." | ||
| ) | ||
|
|
||
| // overlayFSWhiteoutConvert detects whiteouts and opaque directories. | ||
| // | ||
| // It returns deleted indicator if the file is a character device with 0/0 | ||
| // device number. And call changeFn with ChangeKindDelete for opaque | ||
| // directories. | ||
| // | ||
| // Check: https://www.kernel.org/doc/Documentation/filesystems/overlayfs.txt | ||
| func overlayFSWhiteoutConvert(diffDir, path string, f os.FileInfo, changeFn ChangeFunc) (deleted bool, _ error) { | ||
| if f.Mode()&os.ModeCharDevice != 0 { | ||
| if _, ok := f.Sys().(*syscall.Stat_t); !ok { | ||
| return false, nil | ||
| } | ||
|
|
||
| maj, min, err := devices.DeviceInfo(f) | ||
| if err != nil { | ||
| return false, err | ||
| } | ||
| return (maj == 0 && min == 0), nil | ||
| } | ||
|
|
||
| if f.IsDir() { | ||
| originalPath := filepath.Join(diffDir, path) | ||
| opaque, err := getOpaqueValue(originalPath) | ||
| if err != nil { | ||
| if errors.Is(err, unix.ENODATA) { | ||
| return false, nil | ||
| } | ||
| return false, err | ||
| } | ||
|
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| if len(opaque) == 1 && opaque[0] == 'y' { | ||
| opaqueDirPath := filepath.Join(path, whiteoutPrefix+".opq") | ||
| return false, changeFn(ChangeKindDelete, opaqueDirPath, nil, nil) | ||
| } | ||
| } | ||
| return false, nil | ||
| } | ||
|
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||
| // getOpaqueValue returns opaque value for a given file. | ||
| func getOpaqueValue(filePath string) ([]byte, error) { | ||
| for _, xattr := range []string{ | ||
| "trusted.overlay.opaque", | ||
| // TODO(fuweid): | ||
| // | ||
| // user.overlay.* is available since 5.11. We should check | ||
| // kernel version before read. | ||
| // | ||
| // REF: https://github.com/torvalds/linux/commit/2d2f2d7322ff43e0fe92bf8cccdc0b09449bf2e1 | ||
| "user.overlay.opaque", | ||
| } { | ||
| opaque, err := sysx.LGetxattr(filePath, xattr) | ||
| if err != nil { | ||
| if errors.Is(err, unix.ENODATA) || errors.Is(err, unix.ENOTSUP) { | ||
| continue | ||
| } | ||
| return nil, fmt.Errorf("failed to retrieve %s attr: %w", xattr, err) | ||
| } | ||
| return opaque, nil | ||
| } | ||
| return nil, unix.ENODATA | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,29 @@ | ||
| //go:build !linux | ||
| // +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 fs | ||
|
|
||
| import ( | ||
| "errors" | ||
| "os" | ||
| ) | ||
|
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| func overlayFSWhiteoutConvert(string, string, os.FileInfo, ChangeFunc) (bool, error) { | ||
| return false, errors.New("unsupported") | ||
| } |
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