Modify storage to allow callers to determine if a mount point is mounted

Add force to umount to force the umount of a container image
Add an interface to indicate whether or not the layer is mounted
Add a boolean return from unmount to indicate when the layer is really unmounted

Signed-off-by: Daniel J Walsh <[email protected]>

cmd/containers-storage/copy.go

@@ -59,7 +59,7 @@ func copyContent(flags *mflag.FlagSet, action string, m storage.Store, args []st
 			return 1
 		}
 		target = filepath.Join(targetMount, targetParts[1])
-		defer m.Unmount(targetLayer.ID)
+		defer m.Unmount(targetLayer.ID, false)
 	}
 	args = args[:len(args)-1]
 	for _, srcSpec := range args {
@@ -83,7 +83,7 @@ func copyContent(flags *mflag.FlagSet, action string, m storage.Store, args []st
 				return 1
 			}
 			source = filepath.Join(sourceMount, sourceParts[1])
-			defer m.Unmount(sourceLayer.ID)
+			defer m.Unmount(sourceLayer.ID, false)
 		}
 		archiver := chrootarchive.NewArchiverWithChown(tarIDMappings, chownOpts, untarIDMappings)
 		if err := archiver.CopyWithTar(source, target); err != nil {

cmd/containers-storage/main.go

@@ -24,6 +24,7 @@ type command struct {
 var (
 	commands   = []command{}
 	jsonOutput = false
+	force      = false
 )
 
 func main() {

cmd/containers-storage/mount.go

@@ -51,11 +51,15 @@ func unmount(flags *mflag.FlagSet, action string, m storage.Store, args []string
 	mes := []mountPointError{}
 	errors := false
 	for _, arg := range args {
-		err := m.Unmount(arg)
+		mounted, err := m.Unmount(arg, force)
 		errText := ""
 		if err != nil {
 			errText = fmt.Sprintf("%v", err)
 			errors = true
+		} else {
+			if !mounted {
+				fmt.Printf("%s mountpoint unmounted\n", arg)
+			}
 		}
 		mes = append(mes, mountPointError{arg, errText})
 	}
@@ -74,6 +78,37 @@ func unmount(flags *mflag.FlagSet, action string, m storage.Store, args []string
 	return 0
 }
 
+func mounted(flags *mflag.FlagSet, action string, m storage.Store, args []string) int {
+	mes := []mountPointError{}
+	errors := false
+	for _, arg := range args {
+		mounted, err := m.Mounted(arg)
+		errText := ""
+		if err != nil {
+			errText = fmt.Sprintf("%v", err)
+			errors = true
+		} else {
+			if mounted {
+				fmt.Printf("%s mounted\n", arg)
+			}
+		}
+		mes = append(mes, mountPointError{arg, errText})
+	}
+	if jsonOutput {
+		json.NewEncoder(os.Stdout).Encode(mes)
+	} else {
+		for _, me := range mes {
+			if me.Error != "" {
+				fmt.Fprintf(os.Stderr, "%s checking if %s is mounted\n", me.Error, me.ID)
+			}
+		}
+	}
+	if errors {
+		return 1
+	}
+	return 0
+}
+
 func init() {
 	commands = append(commands, command{
 		names:       []string{"mount"},
@@ -92,6 +127,17 @@ func init() {
 		usage:       "Unmount a layer or container",
 		minArgs:     1,
 		action:      unmount,
+		addFlags: func(flags *mflag.FlagSet, cmd *command) {
+			flags.BoolVar(&jsonOutput, []string{"-json", "j"}, jsonOutput, "Prefer JSON output")
+			flags.BoolVar(&force, []string{"-force", "f"}, jsonOutput, "Force the umount")
+		},
+	})
+	commands = append(commands, command{
+		names:       []string{"mounted"},
+		optionsHelp: "LayerOrContainerNameOrID",
+		usage:       "Check if a file system is mounted",
+		minArgs:     1,
+		action:      mounted,
 		addFlags: func(flags *mflag.FlagSet, cmd *command) {
 			flags.BoolVar(&jsonOutput, []string{"-json", "j"}, jsonOutput, "Prefer JSON output")
 		},

layers.go

@@ -211,7 +211,10 @@ type LayerStore interface {
 	Mount(id, mountLabel string) (string, error)
 
 	// Unmount unmounts a layer when it is no longer in use.
-	Unmount(id string) error
+	Unmount(id string, force bool) (bool, error)
+
+	// Mounted returns whether or not the layer is mounted.
+	Mounted(id string) (bool, error)
 
 	// ParentOwners returns the UIDs and GIDs of parents of the layer's mountpoint
 	// for which the layer's UID and GID maps don't contain corresponding entries.
@@ -624,6 +627,14 @@ func (r *layerStore) Create(id string, parent *Layer, names []string, mountLabel
 	return r.CreateWithFlags(id, parent, names, mountLabel, options, moreOptions, writeable, nil)
 }
 
+func (r *layerStore) Mounted(id string) (bool, error) {
+	layer, ok := r.lookup(id)
+	if !ok {
+		return false, ErrLayerUnknown
+	}
+	return layer.MountCount > 0, nil
+}
+
 func (r *layerStore) Mount(id, mountLabel string) (string, error) {
 	if !r.IsReadWrite() {
 		return "", errors.Wrapf(ErrStoreIsReadOnly, "not allowed to update mount locations for layers at %q", r.mountspath())
@@ -652,21 +663,24 @@ func (r *layerStore) Mount(id, mountLabel string) (string, error) {
 	return mountpoint, err
 }
 
-func (r *layerStore) Unmount(id string) error {
+func (r *layerStore) Unmount(id string, force bool) (bool, error) {
 	if !r.IsReadWrite() {
-		return errors.Wrapf(ErrStoreIsReadOnly, "not allowed to update mount locations for layers at %q", r.mountspath())
+		return false, errors.Wrapf(ErrStoreIsReadOnly, "not allowed to update mount locations for layers at %q", r.mountspath())
 	}
 	layer, ok := r.lookup(id)
 	if !ok {
 		layerByMount, ok := r.bymount[filepath.Clean(id)]
 		if !ok {
-			return ErrLayerUnknown
+			return false, ErrLayerUnknown
 		}
 		layer = layerByMount
 	}
+	if force {
+		layer.MountCount = 1
+	}
 	if layer.MountCount > 1 {
 		layer.MountCount--
-		return r.Save()
+		return true, r.Save()
 	}
 	err := r.driver.Put(id)
 	if err == nil || os.IsNotExist(err) {
@@ -675,9 +689,9 @@ func (r *layerStore) Unmount(id string) error {
 		}
 		layer.MountCount--
 		layer.MountPoint = ""
-		err = r.Save()
+		return false, r.Save()
 	}
-	return err
+	return true, err
 }
 
 func (r *layerStore) ParentOwners(id string) (uids, gids []int, err error) {
@@ -797,10 +811,8 @@ func (r *layerStore) Delete(id string) error {
 		return ErrLayerUnknown
 	}
 	id = layer.ID
-	for layer.MountCount > 0 {
-		if err := r.Unmount(id); err != nil {
-			return err
-		}
+	if _, err := r.Unmount(id, true); err != nil {
+		return err
 	}
 	err := r.driver.Remove(id)
 	if err == nil {
@@ -917,7 +929,8 @@ func (s *simpleGetCloser) Get(path string) (io.ReadCloser, error) {
 }
 
 func (s *simpleGetCloser) Close() error {
-	return s.r.Unmount(s.id)
+	_, err := s.r.Unmount(s.id, false)
+	return err
 }
 
 func (r *layerStore) newFileGetter(id string) (drivers.FileGetCloser, error) {

store.go

@@ -262,8 +262,11 @@ type Store interface {
 	Mount(id, mountLabel string) (string, error)
 
 	// Unmount attempts to unmount a layer, image, or container, given an ID, a
-	// name, or a mount path.
-	Unmount(id string) error
+	// name, or a mount path. Returns whether or not the layer is still mounted.
+	Unmount(id string, force bool) (bool, error)
+
+	// Unmount attempts to discover whether the specified id is mounted.
+	Mounted(id string) (bool, error)
 
 	// Changes returns a summary of the changes which would need to be made
 	// to one layer to make its contents the same as a second layer.  If
@@ -2245,23 +2248,40 @@ func (s *store) Mount(id, mountLabel string) (string, error) {
 	return "", ErrLayerUnknown
 }
 
-func (s *store) Unmount(id string) error {
+func (s *store) Mounted(id string) (bool, error) {
 	if layerID, err := s.ContainerLayerID(id); err == nil {
 		id = layerID
 	}
 	rlstore, err := s.LayerStore()
 	if err != nil {
-		return err
+		return false, err
+	}
+	rlstore.Lock()
+	defer rlstore.Unlock()
+	if modified, err := rlstore.Modified(); modified || err != nil {
+		rlstore.Load()
+	}
+
+	return rlstore.Mounted(id)
+}
+
+func (s *store) Unmount(id string, force bool) (bool, error) {
+	if layerID, err := s.ContainerLayerID(id); err == nil {
+		id = layerID
+	}
+	rlstore, err := s.LayerStore()
+	if err != nil {
+		return false, err
 	}
 	rlstore.Lock()
 	defer rlstore.Unlock()
 	if modified, err := rlstore.Modified(); modified || err != nil {
 		rlstore.Load()
 	}
 	if rlstore.Exists(id) {
-		return rlstore.Unmount(id)
+		return rlstore.Unmount(id, force)
 	}
-	return ErrLayerUnknown
+	return false, ErrLayerUnknown
 }
 
 func (s *store) Changes(from, to string) ([]archive.Change, error) {
@@ -2811,7 +2831,7 @@ func (s *store) Shutdown(force bool) ([]string, error) {
 		mounted = append(mounted, layer.ID)
 		if force {
 			for layer.MountCount > 0 {
-				err2 := rlstore.Unmount(layer.ID)
+				_, err2 := rlstore.Unmount(layer.ID, force)
 				if err2 != nil {
 					if err == nil {
 						err = err2

tests/mount-layer.bats

@@ -0,0 +1,81 @@
+#!/usr/bin/env bats
+
+load helpers
+
+@test "mount-layer" {
+	# Create a layer.
+	run storage --debug=false create-layer
+	[ "$status" -eq 0 ]
+	[ "$output" != "" ]
+	layer="$output"
+
+	# Mount the layer.
+	run storage --debug=false mount $layer
+	[ "$status" -eq 0 ]
+	[ "$output" != "" ]
+	# Check if layer is mounted.
+	run storage --debug=false mounted $layer
+	[ "$status" -eq 0 ]
+	[ "$output" == "$layer mounted" ]
+	# Unmount the layer.
+	run storage --debug=false unmount $layer
+	[ "$status" -eq 0 ]
+	[ "$output" != "" ]
+	# Make sure layer is not mounted.
+	run storage --debug=false mounted $layer
+	[ "$status" -eq 0 ]
+	[ "$output" == "" ]
+
+	# Mount the layer twice.
+	run storage --debug=false mount $layer
+	[ "$status" -eq 0 ]
+	[ "$output" != "" ]
+	run storage --debug=false mount $layer
+	[ "$status" -eq 0 ]
+	[ "$output" != "" ]
+	# Check if layer is mounted.
+	run storage --debug=false mounted $layer
+	[ "$status" -eq 0 ]
+	[ "$output" == "$layer mounted" ]
+	# Unmount the second layer.
+	run storage --debug=false unmount $layer
+	[ "$status" -eq 0 ]
+	[ "$output" == "" ]
+	# Check if layer is mounted.
+	run storage --debug=false mounted $layer
+	[ "$status" -eq 0 ]
+	[ "$output" == "$layer mounted" ]
+	# Unmount the first layer.
+	run storage --debug=false unmount $layer
+	[ "$status" -eq 0 ]
+	[ "$output" != "" ]
+	# Make sure layer is not mounted.
+	run storage --debug=false mounted $layer
+	[ "$status" -eq 0 ]
+	[ "$output" == "" ]
+
+
+	# Mount the layer twice and force umount.
+	run storage --debug=false mount $layer
+	[ "$status" -eq 0 ]
+	[ "$output" != "" ]
+	run storage --debug=false mount $layer
+	[ "$status" -eq 0 ]
+	[ "$output" != "" ]
+	# Check if layer is mounted.
+	run storage --debug=false mounted $layer
+	[ "$status" -eq 0 ]
+	[ "$output" == "$layer mounted" ]
+	# Unmount all layers.
+	run storage --debug=false unmount --force $layer
+	[ "$status" -eq 0 ]
+	[ "$output" != "" ]
+	# Make sure no layers are mounted.
+	run storage --debug=false mounted $layer
+	[ "$status" -eq 0 ]
+	[ "$output" == "" ]
+
+	# Delete the first layer
+	run storage delete-layer $layer
+	[ "$status" -eq 0 ]
+}