Merge pull request #3931 from mheon/volumes_with_options

Add support for mounting volumes with local driver and options

12 files changed, 534 insertions, 39 deletions

diff --git a/libpod/boltdb_state.go b/libpod/boltdb_state.go
index 1de8d80c9..31b551b36 100644
--- a/libpod/boltdb_state.go
+++ b/libpod/boltdb_state.go
@@ -159,6 +159,16 @@ func (s *BoltState) Refresh() error {
 			return err
 		}
 
+		allVolsBucket, err := getAllVolsBucket(tx)
+		if err != nil {
+			return err
+		}
+
+		volBucket, err := getVolBucket(tx)
+		if err != nil {
+			return err
+		}
+
 		// Iterate through all IDs. Check if they are containers.
 		// If they are, unmarshal their state, and then clear
 		// PID, mountpoint, and state for all of them
@@ -235,6 +245,44 @@ func (s *BoltState) Refresh() error {
 
 			return nil
 		})
+		if err != nil {
+			return err
+		}
+
+		// Now refresh volumes
+		err = allVolsBucket.ForEach(func(id, name []byte) error {
+			dbVol := volBucket.Bucket(id)
+			if dbVol == nil {
+				return errors.Wrapf(define.ErrInternal, "inconsistency in state - volume %s is in all volumes bucket but volume not found", string(id))
+			}
+
+			// Get the state
+			volStateBytes := dbVol.Get(stateKey)
+			if volStateBytes == nil {
+				// If the volume doesn't have a state, nothing to do
+				return nil
+			}
+
+			oldState := new(VolumeState)
+
+			if err := json.Unmarshal(volStateBytes, oldState); err != nil {
+				return errors.Wrapf(err, "error unmarshalling state for volume %s", string(id))
+			}
+
+			// Reset mount count to 0
+			oldState.MountCount = 0
+
+			newState, err := json.Marshal(oldState)
+			if err != nil {
+				return errors.Wrapf(err, "error marshalling state for volume %s", string(id))
+			}
+
+			if err := dbVol.Put(stateKey, newState); err != nil {
+				return errors.Wrapf(err, "error storing new state for volume %s", string(id))
+			}
+
+			return nil
+		})
 		return err
 	})
 	return err
@@ -1352,6 +1400,15 @@ func (s *BoltState) AddVolume(volume *Volume) error {
 		return errors.Wrapf(err, "error marshalling volume %s config to JSON", volume.Name())
 	}
 
+	// Volume state is allowed to not exist
+	var volStateJSON []byte
+	if volume.state != nil {
+		volStateJSON, err = json.Marshal(volume.state)
+		if err != nil {
+			return errors.Wrapf(err, "error marshalling volume %s state to JSON", volume.Name())
+		}
+	}
+
 	db, err := s.getDBCon()
 	if err != nil {
 		return err
@@ -1392,6 +1449,12 @@ func (s *BoltState) AddVolume(volume *Volume) error {
 			return errors.Wrapf(err, "error storing volume %s configuration in DB", volume.Name())
 		}
 
+		if volStateJSON != nil {
+			if err := newVol.Put(stateKey, volStateJSON); err != nil {
+				return errors.Wrapf(err, "error storing volume %s state in DB", volume.Name())
+			}
+		}
+
 		if err := allVolsBkt.Put(volName, volName); err != nil {
 			return errors.Wrapf(err, "error storing volume %s in all volumes bucket in DB", volume.Name())
 		}
@@ -1483,6 +1546,103 @@ func (s *BoltState) RemoveVolume(volume *Volume) error {
 	return err
 }
 
+// UpdateVolume updates the volume's state from the database.
+func (s *BoltState) UpdateVolume(volume *Volume) error {
+	if !s.valid {
+		return define.ErrDBClosed
+	}
+
+	if !volume.valid {
+		return define.ErrVolumeRemoved
+	}
+
+	newState := new(VolumeState)
+	volumeName := []byte(volume.Name())
+
+	db, err := s.getDBCon()
+	if err != nil {
+		return err
+	}
+	defer s.deferredCloseDBCon(db)
+
+	err = db.View(func(tx *bolt.Tx) error {
+		volBucket, err := getVolBucket(tx)
+		if err != nil {
+			return err
+		}
+
+		volToUpdate := volBucket.Bucket(volumeName)
+		if volToUpdate == nil {
+			volume.valid = false
+			return errors.Wrapf(define.ErrNoSuchVolume, "no volume with name %s found in database", volume.Name())
+		}
+
+		stateBytes := volToUpdate.Get(stateKey)
+		if stateBytes == nil {
+			// Having no state is valid.
+			// Return nil, use the empty state.
+			return nil
+		}
+
+		if err := json.Unmarshal(stateBytes, newState); err != nil {
+			return errors.Wrapf(err, "error unmarshalling volume %s state", volume.Name())
+		}
+
+		return nil
+	})
+	if err != nil {
+		return err
+	}
+
+	volume.state = newState
+
+	return nil
+}
+
+// SaveVolume saves the volume's state to the database.
+func (s *BoltState) SaveVolume(volume *Volume) error {
+	if !s.valid {
+		return define.ErrDBClosed
+	}
+
+	if !volume.valid {
+		return define.ErrVolumeRemoved
+	}
+
+	volumeName := []byte(volume.Name())
+
+	var newStateJSON []byte
+	if volume.state != nil {
+		stateJSON, err := json.Marshal(volume.state)
+		if err != nil {
+			return errors.Wrapf(err, "error marshalling volume %s state to JSON", volume.Name())
+		}
+		newStateJSON = stateJSON
+	}
+
+	db, err := s.getDBCon()
+	if err != nil {
+		return err
+	}
+	defer s.deferredCloseDBCon(db)
+
+	err = db.Update(func(tx *bolt.Tx) error {
+		volBucket, err := getVolBucket(tx)
+		if err != nil {
+			return err
+		}
+
+		volToUpdate := volBucket.Bucket(volumeName)
+		if volToUpdate == nil {
+			volume.valid = false
+			return errors.Wrapf(define.ErrNoSuchVolume, "no volume with name %s found in database", volume.Name())
+		}
+
+		return volToUpdate.Put(stateKey, newStateJSON)
+	})
+	return err
+}
+
 // AllVolumes returns all volumes present in the state
 func (s *BoltState) AllVolumes() ([]*Volume, error) {
 	if !s.valid {
@@ -1517,6 +1677,7 @@ func (s *BoltState) AllVolumes() ([]*Volume, error) {
 
 			volume := new(Volume)
 			volume.config = new(VolumeConfig)
+			volume.state = new(VolumeState)
 
 			if err := s.getVolumeFromDB(id, volume, volBucket); err != nil {
 				if errors.Cause(err) != define.ErrNSMismatch {
@@ -1551,6 +1712,7 @@ func (s *BoltState) Volume(name string) (*Volume, error) {
 
 	volume := new(Volume)
 	volume.config = new(VolumeConfig)
+	volume.state = new(VolumeState)
 
 	db, err := s.getDBCon()
 	if err != nil {
diff --git a/libpod/boltdb_state_internal.go b/libpod/boltdb_state_internal.go
index 6e4179835..a50fce31e 100644
--- a/libpod/boltdb_state_internal.go
+++ b/libpod/boltdb_state_internal.go
@@ -449,6 +449,14 @@ func (s *BoltState) getVolumeFromDB(name []byte, volume *Volume, volBkt *bolt.Bu
 		return errors.Wrapf(err, "error unmarshalling volume %s config from DB", string(name))
 	}
 
+	// Volume state is allowed to be nil for legacy compatibility
+	volStateBytes := volDB.Get(stateKey)
+	if volStateBytes != nil {
+		if err := json.Unmarshal(volStateBytes, volume.state); err != nil {
+			return errors.Wrapf(err, "error unmarshalling volume %s state from DB", string(name))
+		}
+	}
+
 	// Get the lock
 	lock, err := s.runtime.lockManager.RetrieveLock(volume.config.LockID)
 	if err != nil {
diff --git a/libpod/container_internal.go b/libpod/container_internal.go
index f51b53e85..ffc6c11ee 100644
--- a/libpod/container_internal.go
+++ b/libpod/container_internal.go
@@ -1205,7 +1205,7 @@ func (c *Container) restartWithTimeout(ctx context.Context, timeout uint) (err e
 // TODO: Add ability to override mount label so we can use this for Mount() too
 // TODO: Can we use this for export? Copying SHM into the export might not be
 // good
-func (c *Container) mountStorage() (string, error) {
+func (c *Container) mountStorage() (_ string, Err error) {
 	var err error
 	// Container already mounted, nothing to do
 	if c.state.Mounted {
@@ -1225,6 +1225,40 @@ func (c *Container) mountStorage() (string, error) {
 		if err := os.Chown(c.config.ShmDir, c.RootUID(), c.RootGID()); err != nil {
 			return "", errors.Wrapf(err, "failed to chown %s", c.config.ShmDir)
 		}
+		defer func() {
+			if Err != nil {
+				if err := c.unmountSHM(c.config.ShmDir); err != nil {
+					logrus.Errorf("Error unmounting SHM for container %s after mount error: %v", c.ID(), err)
+				}
+			}
+		}()
+	}
+
+	// Request a mount of all named volumes
+	for _, v := range c.config.NamedVolumes {
+		vol, err := c.runtime.state.Volume(v.Name)
+		if err != nil {
+			return "", errors.Wrapf(err, "error retrieving named volume %s for container %s", v.Name, c.ID())
+		}
+
+		if vol.needsMount() {
+			vol.lock.Lock()
+			if err := vol.mount(); err != nil {
+				vol.lock.Unlock()
+				return "", errors.Wrapf(err, "error mounting volume %s for container %s", vol.Name(), c.ID())
+			}
+			vol.lock.Unlock()
+			defer func() {
+				if Err == nil {
+					return
+				}
+				vol.lock.Lock()
+				if err := vol.unmount(false); err != nil {
+					logrus.Errorf("Error unmounting volume %s after error mounting container %s: %v", vol.Name(), c.ID(), err)
+				}
+				vol.lock.Unlock()
+			}()
+		}
 	}
 
 	// TODO: generalize this mount code so it will mount every mount in ctr.config.Mounts
@@ -1247,14 +1281,19 @@ func (c *Container) cleanupStorage() error {
 		return nil
 	}
 
+	var cleanupErr error
+
 	for _, containerMount := range c.config.Mounts {
 		if err := c.unmountSHM(containerMount); err != nil {
-			return err
+			if cleanupErr != nil {
+				logrus.Errorf("Error unmounting container %s: %v", c.ID(), cleanupErr)
+			}
+			cleanupErr = err
 		}
 	}
 
 	if c.config.Rootfs != "" {
-		return nil
+		return cleanupErr
 	}
 
 	if err := c.unmount(false); err != nil {
@@ -1264,19 +1303,52 @@ func (c *Container) cleanupStorage() error {
 		// state
 		if errors.Cause(err) == storage.ErrNotAContainer || errors.Cause(err) == storage.ErrContainerUnknown {
 			logrus.Errorf("Storage for container %s has been removed", c.ID())
-			return nil
+		} else {
+			if cleanupErr != nil {
+				logrus.Errorf("Error cleaning up container %s storage: %v", c.ID(), cleanupErr)
+			}
+			cleanupErr = err
 		}
+	}
 
-		return err
+	// Request an unmount of all named volumes
+	for _, v := range c.config.NamedVolumes {
+		vol, err := c.runtime.state.Volume(v.Name)
+		if err != nil {
+			if cleanupErr != nil {
+				logrus.Errorf("Error unmounting container %s: %v", c.ID(), cleanupErr)
+			}
+			cleanupErr = errors.Wrapf(err, "error retrieving named volume %s for container %s", v.Name, c.ID())
+
+			// We need to try and unmount every volume, so continue
+			// if they fail.
+			continue
+		}
+
+		if vol.needsMount() {
+			vol.lock.Lock()
+			if err := vol.unmount(false); err != nil {
+				if cleanupErr != nil {
+					logrus.Errorf("Error unmounting container %s: %v", c.ID(), cleanupErr)
+				}
+				cleanupErr = errors.Wrapf(err, "error unmounting volume %s for container %s", vol.Name(), c.ID())
+			}
+			vol.lock.Unlock()
+		}
 	}
 
 	c.state.Mountpoint = ""
 	c.state.Mounted = false
 
 	if c.valid {
-		return c.save()
+		if err := c.save(); err != nil {
+			if cleanupErr != nil {
+				logrus.Errorf("Error unmounting container %s: %v", c.ID(), cleanupErr)
+			}
+			cleanupErr = err
+		}
 	}
-	return nil
+	return cleanupErr
 }
 
 // Unmount the a container and free its resources
diff --git a/libpod/container_internal_linux.go b/libpod/container_internal_linux.go
index cb19b5484..a84db9aa5 100644
--- a/libpod/container_internal_linux.go
+++ b/libpod/container_internal_linux.go
@@ -49,19 +49,19 @@ func (c *Container) mountSHM(shmOptions string) error {
 }
 
 func (c *Container) unmountSHM(mount string) error {
-	if err := unix.Unmount(mount, unix.MNT_DETACH); err != nil {
+	if err := unix.Unmount(mount, 0); err != nil {
 		if err != syscall.EINVAL {
-			logrus.Warnf("container %s failed to unmount %s : %v", c.ID(), mount, err)
-		} else {
-			logrus.Debugf("container %s failed to unmount %s : %v", c.ID(), mount, err)
+			return errors.Wrapf(err, "error unmounting container %s SHM mount %s", c.ID(), mount)
 		}
+		// If it's just an EINVAL, debug logs only
+		logrus.Debugf("container %s failed to unmount %s : %v", c.ID(), mount, err)
 	}
 	return nil
 }
 
 // prepare mounts the container and sets up other required resources like net
 // namespaces
-func (c *Container) prepare() (err error) {
+func (c *Container) prepare() (Err error) {
 	var (
 		wg                              sync.WaitGroup
 		netNS                           ns.NetNS
@@ -108,31 +108,42 @@ func (c *Container) prepare() (err error) {
 		logrus.Debugf("Created root filesystem for container %s at %s", c.ID(), c.state.Mountpoint)
 	}()
 
-	defer func() {
-		if err != nil {
-			if err2 := c.cleanupNetwork(); err2 != nil {
-				logrus.Errorf("Error cleaning up container %s network: %v", c.ID(), err2)
-			}
-			if err2 := c.cleanupStorage(); err2 != nil {
-				logrus.Errorf("Error cleaning up container %s storage: %v", c.ID(), err2)
-			}
-		}
-	}()
-
 	wg.Wait()
 
+	var createErr error
 	if createNetNSErr != nil {
-		if mountStorageErr != nil {
-			logrus.Error(createNetNSErr)
-			return mountStorageErr
-		}
-		return createNetNSErr
+		createErr = createNetNSErr
 	}
 	if mountStorageErr != nil {
-		return mountStorageErr
+		logrus.Errorf("Error preparing container %s: %v", c.ID(), createErr)
+		createErr = mountStorageErr
+	}
+
+	// Only trigger storage cleanup if mountStorage was successful.
+	// Otherwise, we may mess up mount counters.
+	if createNetNSErr != nil && mountStorageErr == nil {
+		if err := c.cleanupStorage(); err != nil {
+			// createErr is guaranteed non-nil, so print
+			// unconditionally
+			logrus.Errorf("Error preparing container %s: %v", c.ID(), createErr)
+			createErr = errors.Wrapf(err, "error unmounting storage for container %s after network create failure", c.ID())
+		}
+	}
+
+	// It's OK to unconditionally trigger network cleanup. If the network
+	// isn't ready it will do nothing.
+	if createErr != nil {
+		if err := c.cleanupNetwork(); err != nil {
+			logrus.Errorf("Error preparing container %s: %v", c.ID(), createErr)
+			createErr = errors.Wrapf(err, "error cleaning up container %s network after setup failure", c.ID())
+		}
+	}
+
+	if createErr != nil {
+		return createErr
 	}
 
-	// Save the container
+	// Save changes to container state
 	return c.save()
 }
 
diff --git a/libpod/define/config.go b/libpod/define/config.go
index d8d6ccf55..c66f67feb 100644
--- a/libpod/define/config.go
+++ b/libpod/define/config.go
@@ -18,3 +18,7 @@ type InfoData struct {
 	Type string
 	Data map[string]interface{}
 }
+
+// VolumeDriverLocal is the "local" volume driver. It is managed by libpod
+// itself.
+const VolumeDriverLocal = "local"
diff --git a/libpod/in_memory_state.go b/libpod/in_memory_state.go
index a9b735327..280ae5f5c 100644
--- a/libpod/in_memory_state.go
+++ b/libpod/in_memory_state.go
@@ -507,6 +507,36 @@ func (s *InMemoryState) RemoveVolume(volume *Volume) error {
 	return nil
 }
 
+// UpdateVolume updates a volume from the database.
+// For the in-memory state, this is a no-op.
+func (s *InMemoryState) UpdateVolume(volume *Volume) error {
+	if !volume.valid {
+		return define.ErrVolumeRemoved
+	}
+
+	if _, ok := s.volumes[volume.Name()]; !ok {
+		volume.valid = false
+		return errors.Wrapf(define.ErrNoSuchVolume, "volume with name %q not found in state", volume.Name())
+	}
+
+	return nil
+}
+
+// SaveVolume saves a volume's state to the database.
+// For the in-memory state, this is a no-op.
+func (s *InMemoryState) SaveVolume(volume *Volume) error {
+	if !volume.valid {
+		return define.ErrVolumeRemoved
+	}
+
+	if _, ok := s.volumes[volume.Name()]; !ok {
+		volume.valid = false
+		return errors.Wrapf(define.ErrNoSuchVolume, "volume with name %q not found in state", volume.Name())
+	}
+
+	return nil
+}
+
 // VolumeInUse checks if the given volume is being used by at least one container
 func (s *InMemoryState) VolumeInUse(volume *Volume) ([]string, error) {
 	if !volume.valid {
diff --git a/libpod/runtime_volume_linux.go b/libpod/runtime_volume_linux.go
index 70296248c..9df93faf3 100644
--- a/libpod/runtime_volume_linux.go
+++ b/libpod/runtime_volume_linux.go
@@ -44,10 +44,23 @@ func (r *Runtime) newVolume(ctx context.Context, options ...VolumeCreateOption)
 		volume.config.Name = stringid.GenerateNonCryptoID()
 	}
 	if volume.config.Driver == "" {
-		volume.config.Driver = "local"
+		volume.config.Driver = define.VolumeDriverLocal
 	}
 	volume.config.CreatedTime = time.Now()
 
+	if volume.config.Driver == define.VolumeDriverLocal {
+		logrus.Debugf("Validating options for local driver")
+		// Validate options
+		for key := range volume.config.Options {
+			switch key {
+			case "device", "o", "type":
+				// Do nothing, valid keys
+			default:
+				return nil, errors.Wrapf(define.ErrInvalidArg, "invalid mount option %s for driver 'local'", key)
+			}
+		}
+	}
+
 	// Create the mountpoint of this volume
 	volPathRoot := filepath.Join(r.config.VolumePath, volume.config.Name)
 	if err := os.MkdirAll(volPathRoot, 0700); err != nil {
@@ -102,6 +115,11 @@ func (r *Runtime) removeVolume(ctx context.Context, v *Volume, force bool) error
 		return define.ErrVolumeRemoved
 	}
 
+	// Update volume status to pick up a potential removal from state
+	if err := v.update(); err != nil {
+		return err
+	}
+
 	deps, err := r.state.VolumeInUse(v)
 	if err != nil {
 		return err
@@ -137,6 +155,11 @@ func (r *Runtime) removeVolume(ctx context.Context, v *Volume, force bool) error
 		}
 	}
 
+	// If the volume is still mounted - force unmount it
+	if err := v.unmount(true); err != nil {
+		return errors.Wrapf(err, "error unmounting volume %s", v.Name())
+	}
+
 	// Set volume as invalid so it can no longer be used
 	v.valid = false
 
diff --git a/libpod/state.go b/libpod/state.go
index 5d704e69a..db4667ad6 100644
--- a/libpod/state.go
+++ b/libpod/state.go
@@ -203,6 +203,10 @@ type State interface {
 	// RemoveVolume removes the specified volume.
 	// Only volumes that have no container dependencies can be removed
 	RemoveVolume(volume *Volume) error
+	// UpdateVolume updates the volume's state from the database.
+	UpdateVolume(volume *Volume) error
+	// SaveVolume saves a volume's state to the database.
+	SaveVolume(volume *Volume) error
 	// AllVolumes returns all the volumes available in the state
 	AllVolumes() ([]*Volume, error)
 }
diff --git a/libpod/volume.go b/libpod/volume.go
index abfa7b3f4..b4de3aedc 100644
--- a/libpod/volume.go
+++ b/libpod/volume.go
@@ -6,17 +6,20 @@ import (
 	"github.com/containers/libpod/libpod/lock"
 )
 
-// Volume is the type used to create named volumes
-// TODO: all volumes should be created using this and the Volume API
+// Volume is a libpod named volume.
+// Named volumes may be shared by multiple containers, and may be created using
+// more complex options than normal bind mounts. They may be backed by a mounted
+// filesystem on the host.
 type Volume struct {
 	config *VolumeConfig
+	state  *VolumeState
 
 	valid   bool
 	runtime *Runtime
 	lock    lock.Locker
 }
 
-// VolumeConfig holds the volume's config information
+// VolumeConfig holds the volume's immutable configuration.
 type VolumeConfig struct {
 	// Name of the volume.
 	Name string `json:"name"`
@@ -26,7 +29,7 @@ type VolumeConfig struct {
 	Labels map[string]string `json:"labels"`
 	// The volume driver. Empty string or local does not activate a volume
 	// driver, all other volumes will.
-	Driver string `json:"driver"`
+	Driver string `json:"volumeDriver"`
 	// The location the volume is mounted at.
 	MountPoint string `json:"mountPoint"`
 	// Time the volume was created.
@@ -34,7 +37,7 @@ type VolumeConfig struct {
 	// Options to pass to the volume driver. For the local driver, this is
 	// a list of mount options. For other drivers, they are passed to the
 	// volume driver handling the volume.
-	Options map[string]string `json:"options"`
+	Options map[string]string `json:"volumeOptions,omitempty"`
 	// Whether this volume was created for a specific container and will be
 	// removed with it.
 	IsCtrSpecific bool `json:"ctrSpecific"`
@@ -44,6 +47,18 @@ type VolumeConfig struct {
 	GID int `json:"gid"`
 }
 
+// VolumeState holds the volume's mutable state.
+// Volumes are not guaranteed to have a state. Only volumes using the Local
+// driver that have mount options set will create a state.
+type VolumeState struct {
+	// MountCount is the number of times this volume has been requested to
+	// be mounted.
+	// It is incremented on mount() and decremented on unmount().
+	// On incrementing from 0, the volume will be mounted on the host.
+	// On decrementing to 0, the volume will be unmounted on the host.
+	MountCount uint `json:"mountCount"`
+}
+
 // Name retrieves the volume's name
 func (v *Volume) Name() string {
 	return v.config.Name
@@ -78,10 +93,9 @@ func (v *Volume) MountPoint() string {
 // Options return the volume's options
 func (v *Volume) Options() map[string]string {
 	options := make(map[string]string)
-	for key, value := range v.config.Options {
-		options[key] = value
+	for k, v := range v.config.Options {
+		options[k] = v
 	}
-
 	return options
 }
 
diff --git a/libpod/volume_internal.go b/libpod/volume_internal.go
index 35f0ca19d..2e886e1b0 100644
--- a/libpod/volume_internal.go
+++ b/libpod/volume_internal.go
@@ -3,6 +3,8 @@ package libpod
 import (
 	"os"
 	"path/filepath"
+
+	"github.com/containers/libpod/libpod/define"
 )
 
 // Creates a new volume
@@ -20,3 +22,25 @@ func newVolume(runtime *Runtime) (*Volume, error) {
 func (v *Volume) teardownStorage() error {
 	return os.RemoveAll(filepath.Join(v.runtime.config.VolumePath, v.Name()))
 }
+
+// Volumes with options set, or a filesystem type, or a device to mount need to
+// be mounted and unmounted.
+func (v *Volume) needsMount() bool {
+	return len(v.config.Options) > 0 && v.config.Driver == define.VolumeDriverLocal
+}
+
+// update() updates the volume state from the DB.
+func (v *Volume) update() error {
+	if err := v.runtime.state.UpdateVolume(v); err != nil {
+		return err
+	}
+	if !v.valid {
+		return define.ErrVolumeRemoved
+	}
+	return nil
+}
+
+// save() saves the volume state to the DB
+func (v *Volume) save() error {
+	return v.runtime.state.SaveVolume(v)
+}
diff --git a/libpod/volume_internal_linux.go b/libpod/volume_internal_linux.go
new file mode 100644
index 000000000..9ae4dcf69
--- /dev/null
+++ b/libpod/volume_internal_linux.go
@@ -0,0 +1,128 @@
+// +build linux
+
+package libpod
+
+import (
+	"io/ioutil"
+	"os/exec"
+
+	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
+	"golang.org/x/sys/unix"
+)
+
+// mount mounts the volume if necessary.
+// A mount is necessary if a volume has any options set.
+// If a mount is necessary, v.state.MountCount will be incremented.
+// If it was 0 when the increment occurred, the volume will be mounted on the
+// host. Otherwise, we assume it is already mounted.
+// Must be done while the volume is locked.
+// Is a no-op on volumes that do not require a mount (as defined by
+// volumeNeedsMount())
+func (v *Volume) mount() error {
+	if !v.needsMount() {
+		return nil
+	}
+
+	// Update the volume from the DB to get an accurate mount counter.
+	if err := v.update(); err != nil {
+		return err
+	}
+
+	// If the count is non-zero, the volume is already mounted.
+	// Nothing to do.
+	if v.state.MountCount > 0 {
+		v.state.MountCount = v.state.MountCount + 1
+		logrus.Debugf("Volume %s mount count now at %d", v.Name(), v.state.MountCount)
+		return v.save()
+	}
+
+	volDevice := v.config.Options["device"]
+	volType := v.config.Options["type"]
+	volOptions := v.config.Options["o"]
+
+	// Some filesystems (tmpfs) don't have a device, but we still need to
+	// give the kernel something.
+	if volDevice == "" && volType != "" {
+		volDevice = volType
+	}
+
+	// We need to use the actual mount command.
+	// Convincing unix.Mount to use the same semantics as the mount command
+	// itself seems prohibitively difficult.
+	// TODO: might want to cache this path in the runtime?
+	mountPath, err := exec.LookPath("mount")
+	if err != nil {
+		return errors.Wrapf(err, "error locating 'mount' binary")
+	}
+	mountArgs := []string{}
+	if volOptions != "" {
+		mountArgs = append(mountArgs, "-o", volOptions)
+	}
+	if volType != "" {
+		mountArgs = append(mountArgs, "-t", volType)
+	}
+	mountArgs = append(mountArgs, volDevice, v.config.MountPoint)
+	mountCmd := exec.Command(mountPath, mountArgs...)
+
+	errPipe, err := mountCmd.StderrPipe()
+	if err != nil {
+		return errors.Wrapf(err, "error getting stderr pipe for mount")
+	}
+	if err := mountCmd.Start(); err != nil {
+		out, err2 := ioutil.ReadAll(errPipe)
+		if err2 != nil {
+			return errors.Wrapf(err2, "error reading mount STDERR")
+		}
+		return errors.Wrapf(errors.New(string(out)), "error mounting volume %s", v.Name())
+	}
+
+	logrus.Debugf("Mounted volume %s", v.Name())
+
+	// Increment the mount counter
+	v.state.MountCount = v.state.MountCount + 1
+	logrus.Debugf("Volume %s mount count now at %d", v.Name(), v.state.MountCount)
+	return v.save()
+}
+
+// unmount unmounts the volume if necessary.
+// Unmounting a volume that is not mounted is a no-op.
+// Unmounting a volume that does not require a mount is a no-op.
+// The volume must be locked for this to occur.
+// The mount counter will be decremented if non-zero. If the counter reaches 0,
+// the volume will really be unmounted, as no further containers are using the
+// volume.
+// If force is set, the volume will be unmounted regardless of mount counter.
+func (v *Volume) unmount(force bool) error {
+	if !v.needsMount() {
+		return nil
+	}
+
+	// Update the volume from the DB to get an accurate mount counter.
+	if err := v.update(); err != nil {
+		return err
+	}
+
+	if v.state.MountCount == 0 {
+		logrus.Debugf("Volume %s already unmounted", v.Name())
+		return nil
+	}
+
+	if !force {
+		v.state.MountCount = v.state.MountCount - 1
+	} else {
+		v.state.MountCount = 0
+	}
+
+	logrus.Debugf("Volume %s mount count now at %d", v.Name(), v.state.MountCount)
+
+	if v.state.MountCount == 0 {
+		// Unmount the volume
+		if err := unix.Unmount(v.config.MountPoint, unix.MNT_DETACH); err != nil {
+			return errors.Wrapf(err, "error unmounting volume %s", v.Name())
+		}
+		logrus.Debugf("Unmounted volume %s", v.Name())
+	}
+
+	return v.save()
+}
diff --git a/libpod/volume_internal_unsupported.go b/libpod/volume_internal_unsupported.go
new file mode 100644
index 000000000..74e24cfda
--- /dev/null
+++ b/libpod/volume_internal_unsupported.go
@@ -0,0 +1,15 @@
+// +build !linux
+
+package libpod
+
+import (
+	"github.com/containers/libpod/libpod/define"
+)
+
+func (v *Volume) mount() error {
+	return define.ErrNotImplemented
+}
+
+func (v *Volume) unmount(force bool) error {
+	return define.ErrNotImplemented
+}