Merge pull request moby#4 from rumpl/c8d-snap-ff

Introduce containerd-snapshotter feature flag

daemon/daemon.go

@@ -147,6 +147,16 @@ func (daemon *Daemon) Features() *map[string]bool {
 	return &daemon.configStore.Features
 }
 
+// usesSnapshotter returns true if feature flag to use containerd snapshotter is enabled
+func (daemon *Daemon) usesSnapshotter() bool {
+	if daemon.configStore.Features != nil {
+		if b, ok := daemon.configStore.Features["containerd-snapshotter"]; ok {
+			return b
+		}
+	}
+	return false
+}
+
 // RegistryHosts returns registry configuration in containerd resolvers format
 func (daemon *Daemon) RegistryHosts() docker.RegistryHosts {
 	var (

daemon/oci_linux.go

@@ -720,13 +720,19 @@ func sysctlExists(s string) bool {
 // WithCommonOptions sets common docker options
 func WithCommonOptions(daemon *Daemon, c *container.Container) coci.SpecOpts {
 	return func(ctx context.Context, _ coci.Client, _ *containers.Container, s *coci.Spec) error {
-		if c.BaseFS == nil {
+		if c.BaseFS == nil && !daemon.usesSnapshotter() {
 			return errors.New("populateCommonSpec: BaseFS of container " + c.ID + " is unexpectedly nil")
 		}
 		linkedEnv, err := daemon.setupLinkedContainers(c)
 		if err != nil {
 			return err
 		}
+		if !daemon.usesSnapshotter() {
+			s.Root = &specs.Root{
+				Path:     c.BaseFS.Path(),
+				Readonly: c.HostConfig.ReadonlyRootfs,
+			}
+		}
 		s.Root = &specs.Root{
 			Path:     c.BaseFS.Path(),
 			Readonly: c.HostConfig.ReadonlyRootfs,