mount: some refactor and improved GoDoc about Windows support

mount/doc.go

@@ -0,0 +1,5 @@
+// Package mount provides a set of functions to mount and unmount mounts.
+//
+// Currently it supports Linux. For historical reasons, there is also some support for FreeBSD.
+
+package mount

mount/flags.go → mount/flags_unix.go

@@ -1,3 +1,5 @@
+// +build !darwin,!windows
+
 package mount
 
 import (

mount/mount.go → mount/mount_unix.go

@@ -1,4 +1,4 @@
-// +build go1.13
+// +build !darwin,!windows
 
 package mount
 
@@ -7,6 +7,7 @@ import (
 	"sort"
 
 	"github.com/moby/sys/mountinfo"
+	"golang.org/x/sys/unix"
 )
 
 // Mount will mount filesystem according to the specified configuration.
@@ -18,9 +19,22 @@ func Mount(device, target, mType, options string) error {
 }
 
 // Unmount lazily unmounts a filesystem on supported platforms, otherwise does
-// a normal unmount.  If target is not a mount point, no error is returned.
+// a normal unmount. If target is not a mount point, no error is returned.
 func Unmount(target string) error {
-	return unmount(target, mntDetach)
+	err := unix.Unmount(target, mntDetach)
+	if err == nil || err == unix.EINVAL {
+		// Ignore "not mounted" error here. Note the same error
+		// can be returned if flags are invalid, so this code
+		// assumes that the flags value is always correct.
+		return nil
+	}
+
+	return &mountError{
+		op:     "umount",
+		target: target,
+		flags:  uintptr(mntDetach),
+		err:    err,
+	}
 }
 
 // RecursiveUnmount unmounts the target and all mounts underneath, starting
@@ -32,7 +46,7 @@ func RecursiveUnmount(target string) error {
 	// platforms, if there are submounts, we'll get EBUSY (and fall back
 	// to the slow path). NOTE we do not ignore EINVAL here as target might
 	// not be a mount point itself (but there can be mounts underneath).
-	if err := unmountBare(target, mntDetach); err == nil {
+	if err := unix.Unmount(target, mntDetach); err == nil {
 		return nil
 	}
 
@@ -49,7 +63,7 @@ func RecursiveUnmount(target string) error {
 
 	var suberr error
 	for i, m := range mounts {
-		err = unmount(m.Mountpoint, mntDetach)
+		err = Unmount(m.Mountpoint)
 		if err != nil {
 			if i == len(mounts)-1 { // last mount
 				return fmt.Errorf("%w (possible cause: %s)", err, suberr)

mount/mounter_freebsd.go

@@ -1,3 +1,5 @@
+// +build freebsd cgo
+
 package mount
 
 /*

mount/mounter_unsupported.go

@@ -1,7 +1,7 @@
-// +build !linux,!freebsd freebsd,!cgo
+// +build freebsd,!cgo
 
 package mount
 
 func mount(device, target, mType string, flag uintptr, data string) error {
-	panic("Not implemented")
+	panic("cgo required on freebsd")
 }

mount/sharedsubtree_linux_test.go

@@ -1,4 +1,4 @@
-// +build linux,go1.13
+// +build linux
 
 package mount