diff --git a/examples/llbout/example.go b/examples/llbout/example.go
index c2a0b9195..2806ab5cf 100644
--- a/examples/llbout/example.go
+++ b/examples/llbout/example.go
@@ -13,6 +13,7 @@ func main() {
 	alpine := llb.Image("docker.io/library/alpine:latest")
 	mod3 := mod2.Run(llb.Meta{Args: []string{"/bin/cp", "-a", "/alpine/etc/passwd", "baz"}, Cwd: "/"})
 	mod3.AddMount("/alpine", alpine)
+	mod3.AddMount("/redis", busybox)
 	mod4 := mod3.Run(llb.Meta{Args: []string{"/bin/ls", "-l", "/"}, Cwd: "/"})
 
 	res := mod4
diff --git a/solver/solver.go b/solver/solver.go
index e4100e4c6..9b17ae833 100644
--- a/solver/solver.go
+++ b/solver/solver.go
@@ -94,7 +94,7 @@ func (g *opVertex) release(ctx context.Context) (retErr error) {
 	return retErr
 }
 
-func (g *opVertex) getInputRef(i int) cache.ImmutableRef {
+func (g *opVertex) getInputRefForIndex(i int) cache.ImmutableRef {
 	input := g.op.Inputs[i]
 	for _, v := range g.inputs {
 		if v.dgst == digest.Digest(input.Digest) {
@@ -143,86 +143,101 @@ func (g *opVertex) solve(ctx context.Context, opt Opt) (retErr error) {
 		}
 	}
 
-	g.notifyStarted(pw)
-	defer g.notifyComplete(pw)
+	g.notifyStarted(ctx)
+	defer g.notifyCompleted(ctx)
 
 	switch op := g.op.Op.(type) {
 	case *pb.Op_Source:
-		id, err := source.FromString(op.Source.Identifier)
-		if err != nil {
+		if err := g.runSourceOp(ctx, opt.SourceManager, op); err != nil {
 			return err
 		}
-		ref, err := opt.SourceManager.Pull(ctx, id)
-		if err != nil {
-			return err
-		}
-		g.refs = []cache.ImmutableRef{ref}
 	case *pb.Op_Exec:
-
-		mounts := make(map[string]cache.Mountable)
-
-		var outputs []cache.MutableRef
-
-		defer func() {
-			for _, o := range outputs {
-				if o != nil {
-					s, err := o.Freeze() // TODO: log error
-					if err == nil {
-						s.Release(ctx)
-					}
-				}
-			}
-		}()
-
-		for _, m := range op.Exec.Mounts {
-			var mountable cache.Mountable
-			ref := g.getInputRef(int(m.Input))
-			mountable = ref
-			if m.Output != -1 {
-				active, err := opt.CacheManager.New(ctx, ref) // TODO: should be method
-				if err != nil {
-					return err
-				}
-				outputs = append(outputs, active)
-				mountable = active
-			}
-			mounts[m.Dest] = mountable
+		if err := g.runExecOp(ctx, opt.CacheManager, opt.Worker, op); err != nil {
+			return err
 		}
-
-		meta := worker.Meta{
-			Args: op.Exec.Meta.Args,
-			Env:  op.Exec.Meta.Env,
-			Cwd:  op.Exec.Meta.Cwd,
-		}
-
-		if err := opt.Worker.Exec(ctx, meta, mounts, os.Stderr, os.Stderr); err != nil {
-			return errors.Wrapf(err, "worker failed running %v", meta.Args)
-		}
-
-		g.refs = []cache.ImmutableRef{}
-
-		for i, o := range outputs {
-			ref, err := o.ReleaseAndCommit(ctx)
-			if err != nil {
-				return errors.Wrapf(err, "error committing %s", ref.ID())
-			}
-			g.refs = append(g.refs, ref)
-			outputs[i] = nil
-		}
-
 	default:
 		return errors.Errorf("invalid op type")
 	}
 	return nil
 }
 
-func (g *opVertex) notifyStarted(pw progress.Writer) {
+func (g *opVertex) runSourceOp(ctx context.Context, sm *source.Manager, op *pb.Op_Source) error {
+	id, err := source.FromString(op.Source.Identifier)
+	if err != nil {
+		return err
+	}
+	ref, err := sm.Pull(ctx, id)
+	if err != nil {
+		return err
+	}
+	g.refs = []cache.ImmutableRef{ref}
+	return nil
+}
+
+func (g *opVertex) runExecOp(ctx context.Context, cm cache.Manager, w worker.Worker, op *pb.Op_Exec) error {
+	mounts := make(map[string]cache.Mountable)
+
+	var outputs []cache.MutableRef
+
+	defer func() {
+		for _, o := range outputs {
+			if o != nil {
+				s, err := o.Freeze() // TODO: log error
+				if err == nil {
+					s.Release(ctx)
+				}
+			}
+		}
+	}()
+
+	for _, m := range op.Exec.Mounts {
+		var mountable cache.Mountable
+		ref := g.getInputRefForIndex(int(m.Input))
+		mountable = ref
+		if m.Output != -1 {
+			active, err := cm.New(ctx, ref) // TODO: should be method
+			if err != nil {
+				return err
+			}
+			outputs = append(outputs, active)
+			mountable = active
+		}
+		mounts[m.Dest] = mountable
+	}
+
+	meta := worker.Meta{
+		Args: op.Exec.Meta.Args,
+		Env:  op.Exec.Meta.Env,
+		Cwd:  op.Exec.Meta.Cwd,
+	}
+
+	if err := w.Exec(ctx, meta, mounts, os.Stderr, os.Stderr); err != nil {
+		return errors.Wrapf(err, "worker failed running %v", meta.Args)
+	}
+
+	g.refs = []cache.ImmutableRef{}
+	for i, o := range outputs {
+		ref, err := o.ReleaseAndCommit(ctx)
+		if err != nil {
+			return errors.Wrapf(err, "error committing %s", o.ID())
+		}
+		g.refs = append(g.refs, ref)
+		outputs[i] = nil
+	}
+	return nil
+}
+
+func (g *opVertex) notifyStarted(ctx context.Context) {
+	pw, _, _ := progress.FromContext(ctx)
+	defer pw.Close()
 	now := time.Now()
 	g.vtx.Started = &now
 	pw.Write(g.dgst.String(), g.vtx)
 }
 
-func (g *opVertex) notifyComplete(pw progress.Writer) {
+func (g *opVertex) notifyCompleted(ctx context.Context) {
+	pw, _, _ := progress.FromContext(ctx)
+	defer pw.Close()
 	now := time.Now()
 	g.vtx.Completed = &now
 	pw.Write(g.dgst.String(), g.vtx)
diff --git a/util/flightcontrol/flightcontrol.go b/util/flightcontrol/flightcontrol.go
index 7bfec5b36..83a120ff5 100644
--- a/util/flightcontrol/flightcontrol.go
+++ b/util/flightcontrol/flightcontrol.go
@@ -78,7 +78,7 @@ func newCall(fn func(ctx context.Context) (interface{}, error)) *call {
 	c.ctx = ctx
 	c.closeProgressWriter = closeProgressWriter
 
-	go c.progressState.run(pr)
+	go c.progressState.run(pr) // TODO: remove this, wrap writer instead
 
 	return c
 }