Move mount to core/mount

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

core/mount/lookup_unix.go

@@ -0,0 +1,51 @@
+//go:build !windows
+
+/*
+   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 (
+	"fmt"
+
+	"github.com/moby/sys/mountinfo"
+)
+
+// Lookup returns the mount info corresponds to the path.
+func Lookup(dir string) (Info, error) {
+	resolvedDir, err := CanonicalizePath(dir)
+	if err != nil {
+		return Info{}, err
+	}
+
+	m, err := mountinfo.GetMounts(mountinfo.ParentsFilter(resolvedDir))
+	if err != nil {
+		return Info{}, fmt.Errorf("failed to find the mount info for %q: %w", resolvedDir, err)
+	}
+	if len(m) == 0 {
+		return Info{}, fmt.Errorf("failed to find the mount info for %q", resolvedDir)
+	}
+
+	// find the longest matching mount point
+	var idx, maxlen int
+	for i := range m {
+		if len(m[i].Mountpoint) > maxlen {
+			maxlen = len(m[i].Mountpoint)
+			idx = i
+		}
+	}
+	return *m[idx], nil
+}