Move mount to core/mount

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

core/mount/mount_unix.go

@@ -0,0 +1,71 @@
+//go:build !windows && !darwin && !openbsd
+
+/*
+   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 mount
+
+import (
+	"os"
+	"sort"
+
+	"github.com/moby/sys/mountinfo"
+)
+
+// UnmountRecursive unmounts the target and all mounts underneath, starting
+// with the deepest mount first.
+func UnmountRecursive(target string, flags int) error {
+	if target == "" {
+		return nil
+	}
+
+	target, err := CanonicalizePath(target)
+	if err != nil {
+		if os.IsNotExist(err) {
+			err = nil
+		}
+		return err
+	}
+
+	mounts, err := mountinfo.GetMounts(mountinfo.PrefixFilter(target))
+	if err != nil {
+		return err
+	}
+
+	targetSet := make(map[string]struct{})
+	for _, m := range mounts {
+		targetSet[m.Mountpoint] = struct{}{}
+	}
+
+	var targets []string
+	for m := range targetSet {
+		targets = append(targets, m)
+	}
+
+	// Make the deepest mount be first
+	sort.SliceStable(targets, func(i, j int) bool {
+		return len(targets[i]) > len(targets[j])
+	})
+
+	for i, target := range targets {
+		if err := UnmountAll(target, flags); err != nil {
+			if i == len(targets)-1 { // last mount
+				return err
+			}
+		}
+	}
+	return nil
+}