Unmount() and Mounted(): utility functions to unmount a mountpoint and check if it's mounted, respectively

graph/image.go

@@ -92,9 +92,9 @@ func MountAUFS(ro []string, rw string, target string) error {
 }
 
 func (image *Image) Mount(root, rw string) error {
-	if isMounted, err := IsMounted(root); err != nil {
+	if mounted, err := Mounted(root); err != nil {
 		return err
-	} else if isMounted {
+	} else if mounted {
 		return fmt.Errorf("%s is already mounted", root)
 	}
 	layers, err := image.layers()

graph/mount.go

@@ -0,0 +1,48 @@
+package graph
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"syscall"
+	"time"
+)
+
+func Unmount(target string) error {
+	if err := syscall.Unmount(target, 0); err != nil {
+		return err
+	}
+	// Even though we just unmounted the filesystem, AUFS will prevent deleting the mntpoint
+	// for some time. We'll just keep retrying until it succeeds.
+	for retries := 0; retries < 1000; retries++ {
+		err := os.Remove(target)
+		if err == nil {
+			// rm mntpoint succeeded
+			return nil
+		}
+		if os.IsNotExist(err) {
+			// mntpoint doesn't exist anymore. Success.
+			return nil
+		}
+		// fmt.Printf("(%v) Remove %v returned: %v\n", retries, target, err)
+		time.Sleep(10 * time.Millisecond)
+	}
+	return fmt.Errorf("Umount: Failed to umount %v", target)
+}
+
+func Mounted(mountpoint string) (bool, error) {
+	mntpoint, err := os.Stat(mountpoint)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return false, nil
+		}
+		return false, err
+	}
+	parent, err := os.Stat(filepath.Join(mountpoint, ".."))
+	if err != nil {
+		return false, err
+	}
+	mntpointSt := mntpoint.Sys().(*syscall.Stat_t)
+	parentSt := parent.Sys().(*syscall.Stat_t)
+	return mntpointSt.Dev != parentSt.Dev, nil
+}