Move diff to core/diff

Signed-off-by: Derek McGowan <derek@mcg.dev>

core/diff/apply/apply_linux.go

@@ -0,0 +1,105 @@
+/*
+   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"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+
+	"github.com/containerd/containerd/v2/archive"
+	"github.com/containerd/containerd/v2/errdefs"
+	"github.com/containerd/containerd/v2/mount"
+	"github.com/containerd/containerd/v2/pkg/userns"
+
+	"golang.org/x/sys/unix"
+)
+
+func apply(ctx context.Context, mounts []mount.Mount, r io.Reader, sync bool) (retErr error) {
+	switch {
+	case len(mounts) == 1 && mounts[0].Type == "overlay":
+		// OverlayConvertWhiteout (mknod c 0 0) doesn't work in userns.
+		// https://github.com/containerd/containerd/issues/3762
+		if userns.RunningInUserNS() {
+			break
+		}
+		path, parents, err := getOverlayPath(mounts[0].Options)
+		if err != nil {
+			if errdefs.IsInvalidArgument(err) {
+				break
+			}
+			return err
+		}
+		opts := []archive.ApplyOpt{
+			archive.WithConvertWhiteout(archive.OverlayConvertWhiteout),
+		}
+		if len(parents) > 0 {
+			opts = append(opts, archive.WithParents(parents))
+		}
+		_, err = archive.Apply(ctx, path, r, opts...)
+		if err == nil && sync {
+			err = doSyncFs(path)
+		}
+		return err
+	case sync && len(mounts) == 1 && mounts[0].Type == "bind":
+		defer func() {
+			if retErr != nil {
+				return
+			}
+
+			retErr = doSyncFs(mounts[0].Source)
+		}()
+	}
+	return mount.WithTempMount(ctx, mounts, func(root string) error {
+		_, err := archive.Apply(ctx, root, r)
+		return err
+	})
+}
+
+func getOverlayPath(options []string) (upper string, lower []string, err error) {
+	const upperdirPrefix = "upperdir="
+	const lowerdirPrefix = "lowerdir="
+
+	for _, o := range options {
+		if strings.HasPrefix(o, upperdirPrefix) {
+			upper = strings.TrimPrefix(o, upperdirPrefix)
+		} else if strings.HasPrefix(o, lowerdirPrefix) {
+			lower = strings.Split(strings.TrimPrefix(o, lowerdirPrefix), ":")
+		}
+	}
+	if upper == "" {
+		return "", nil, fmt.Errorf("upperdir not found: %w", errdefs.ErrInvalidArgument)
+	}
+
+	return
+}
+
+func doSyncFs(file string) error {
+	fd, err := os.Open(file)
+	if err != nil {
+		return fmt.Errorf("failed to open %s: %w", file, err)
+	}
+	defer fd.Close()
+
+	_, _, errno := unix.Syscall(unix.SYS_SYNCFS, fd.Fd(), 0, 0)
+	if errno != 0 {
+		return fmt.Errorf("failed to syncfs for %s: %w", file, errno)
+	}
+	return nil
+}