Remove locks from volumes

I was looking into why we have locks in volumes, and I'm fairly
convinced they're unnecessary.

We don't have a state whose accesses we need to guard with locks
and syncs. The only real purpose for the lock was to prevent
concurrent removal of the same volume.

Looking at the code, concurrent removal ought to be fine with a
bit of reordering - one or the other might fail, but we will
successfully evict the volume from the state.

Also, remove the 'prune' bool from RemoveVolume. None of our
other API functions accept it, and it only served to toggle off
more verbose error messages.

Signed-off-by: Matthew Heon <matthew.heon@pm.me>

libpod/boltdb_state.go

@@ -1369,10 +1369,6 @@ func (s *BoltState) RemoveVolume(volume *Volume) error {
 		return ErrDBClosed
 	}
 
-	if !volume.valid {
-		return ErrVolumeRemoved
-	}
-
 	volName := []byte(volume.Name())
 
 	db, err := s.getDBCon()

libpod/boltdb_state_internal.go

@@ -348,13 +348,6 @@ func (s *BoltState) getVolumeFromDB(name []byte, volume *Volume, volBkt *bolt.Bu
 		return errors.Wrapf(err, "error unmarshalling volume %s config from DB", string(name))
 	}
 
-	// Get the lock
-	lock, err := s.runtime.lockManager.RetrieveLock(volume.config.LockID)
-	if err != nil {
-		return errors.Wrapf(err, "error retrieving lockfile for volume %s", string(name))
-	}
-	volume.lock = lock
-
 	volume.runtime = s.runtime
 	volume.valid = true
 

libpod/runtime_ctr.go

@@ -421,7 +421,7 @@ func (r *Runtime) removeContainer(ctx context.Context, c *Container, force bool,
 
 	for _, v := range volumes {
 		if volume, err := runtime.state.Volume(v); err == nil {
-			if err := runtime.removeVolume(ctx, volume, false, true); err != nil && err != ErrNoSuchVolume && err != ErrVolumeBeingUsed {
+			if err := runtime.removeVolume(ctx, volume, false); err != nil && err != ErrNoSuchVolume && err != ErrVolumeBeingUsed {
 				logrus.Errorf("cleanup volume (%s): %v", v, err)
 			}
 		}

libpod/runtime_renumber.go

@@ -12,6 +12,12 @@ import (
 // It renders the runtime it is called on, and all container/pod/volume structs
 // from that runtime, unusable, and requires that a new runtime be initialized
 // after it is called.
+// TODO: It would be desirable to make it impossible to call this until all
+// other libpod sessions are dead.
+// Possibly use a read-write file lock, with all non-renumber podmans owning the
+// lock as read, renumber attempting to take a write lock?
+// The alternative is some sort of session tracking, and I don't know how
+// reliable that can be.
 func (r *Runtime) RenumberLocks() error {
 	r.lock.Lock()
 	locked := true

libpod/runtime_volume.go

@@ -19,7 +19,7 @@ type VolumeCreateOption func(*Volume) error
 type VolumeFilter func(*Volume) bool
 
 // RemoveVolume removes a volumes
-func (r *Runtime) RemoveVolume(ctx context.Context, v *Volume, force, prune bool) error {
+func (r *Runtime) RemoveVolume(ctx context.Context, v *Volume, force bool) error {
 	r.lock.Lock()
 	defer r.lock.Unlock()
 
@@ -35,10 +35,7 @@ func (r *Runtime) RemoveVolume(ctx context.Context, v *Volume, force, prune bool
 		}
 	}
 
-	v.lock.Lock()
-	defer v.lock.Unlock()
-
-	return r.removeVolume(ctx, v, force, prune)
+	return r.removeVolume(ctx, v, force)
 }
 
 // RemoveVolumes removes a slice of volumes or all with a force bool
@@ -64,7 +61,7 @@ func (r *Runtime) RemoveVolumes(ctx context.Context, volumes []string, all, forc
 	}
 
 	for _, vol := range vols {
-		if err := r.RemoveVolume(ctx, vol, force, false); err != nil {
+		if err := r.RemoveVolume(ctx, vol, force); err != nil {
 			return deletedVols, err
 		}
 		logrus.Debugf("removed volume %s", vol.Name())
@@ -168,8 +165,8 @@ func (r *Runtime) PruneVolumes(ctx context.Context) ([]string, []error) {
 	}
 
 	for _, vol := range vols {
-		if err := r.RemoveVolume(ctx, vol, false, true); err != nil {
-			if err != ErrVolumeBeingUsed {
+		if err := r.RemoveVolume(ctx, vol, false); err != nil {
+			if errors.Cause(err) != ErrVolumeBeingUsed && errors.Cause(err) != ErrVolumeRemoved {
 				pruneErrors = append(pruneErrors, err)
 			}
 			continue

libpod/runtime_volume_linux.go

@@ -67,13 +67,6 @@ func (r *Runtime) newVolume(ctx context.Context, options ...VolumeCreateOption)
 	}
 	volume.config.MountPoint = fullVolPath
 
-	lock, err := r.lockManager.AllocateLock()
-	if err != nil {
-		return nil, errors.Wrapf(err, "error allocating lock for new volume")
-	}
-	volume.lock = lock
-	volume.config.LockID = volume.lock.ID()
-
 	volume.valid = true
 
 	// Add the volume to state
@@ -85,9 +78,12 @@ func (r *Runtime) newVolume(ctx context.Context, options ...VolumeCreateOption)
 }
 
 // removeVolume removes the specified volume from state as well tears down its mountpoint and storage
-func (r *Runtime) removeVolume(ctx context.Context, v *Volume, force, prune bool) error {
+func (r *Runtime) removeVolume(ctx context.Context, v *Volume, force bool) error {
 	if !v.valid {
-		return ErrNoSuchVolume
+		if ok, _ := r.state.HasVolume(v.Name()); !ok {
+			return nil
+		}
+		return ErrVolumeRemoved
 	}
 
 	deps, err := r.state.VolumeInUse(v)
@@ -95,9 +91,6 @@ func (r *Runtime) removeVolume(ctx context.Context, v *Volume, force, prune bool
 		return err
 	}
 	if len(deps) != 0 {
-		if prune {
-			return ErrVolumeBeingUsed
-		}
 		depsStr := strings.Join(deps, ", ")
 		if !force {
 			return errors.Wrapf(ErrVolumeBeingUsed, "volume %s is being used by the following container(s): %s", v.Name(), depsStr)
@@ -112,18 +105,20 @@ func (r *Runtime) removeVolume(ctx context.Context, v *Volume, force, prune bool
 		}
 	}
 
-	// Delete the mountpoint path of the volume, that is delete the volume from /var/lib/containers/storage/volumes
-	if err := v.teardownStorage(); err != nil {
-		return errors.Wrapf(err, "error cleaning up volume storage for %q", v.Name())
-	}
+	// Set volume as invalid so it can no longer be used
+	v.valid = false
 
 	// Remove the volume from the state
 	if err := r.state.RemoveVolume(v); err != nil {
 		return errors.Wrapf(err, "error removing volume %s", v.Name())
 	}
 
-	// Set volume as invalid so it can no longer be used
-	v.valid = false
+	// Delete the mountpoint path of the volume, that is delete the volume from /var/lib/containers/storage/volumes
+	if err := v.teardownStorage(); err != nil {
+		return errors.Wrapf(err, "error cleaning up volume storage for %q", v.Name())
+	}
+
+	logrus.Debugf("Removed volume %s", v.Name())
 
 	return nil
 }

libpod/volume.go

@@ -1,7 +1,5 @@
 package libpod
 
-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
 type Volume struct {
@@ -9,7 +7,6 @@ type Volume struct {
 
 	valid   bool
 	runtime *Runtime
-	lock    lock.Locker
 }
 
 // VolumeConfig holds the volume's config information
@@ -17,8 +14,6 @@ type Volume struct {
 type VolumeConfig struct {
 	// Name of the volume
 	Name string `json:"name"`
-	// ID of this volume's lock
-	LockID uint32 `json:"lockID"`
 
 	Labels     map[string]string `json:"labels"`
 	MountPoint string            `json:"mountPoint"`

libpod/volume_internal.go

@@ -18,8 +18,5 @@ func newVolume(runtime *Runtime) (*Volume, error) {
 
 // teardownStorage deletes the volume from volumePath
 func (v *Volume) teardownStorage() error {
-	if !v.valid {
-		return ErrNoSuchVolume
-	}
 	return os.RemoveAll(filepath.Join(v.runtime.config.VolumePath, v.Name()))
 }