vendor/github.com/containerd/containerd/mount/mount_unix.go

//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 (
	"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
	}
	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
}