Implement Cloning for csi-hostpath driver

This PR adds support for cloning of hostpath volumes.

examples/csi-clone.yaml

@@ -0,0 +1,15 @@
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: hp-pvc-clone
+spec:
+  storageClassName: csi-hostpath-sc
+  dataSource:
+    name: src-hp-pvc
+    kind: PersistentVolumeClaim
+    apiGroup: ""
+  accessModes:
+    - ReadWriteOnce
+  resources:
+    requests:
+      storage: 1Gi

pkg/hostpath/controllerserver.go

@@ -65,6 +65,7 @@ func NewControllerServer(ephemeral bool) *controllerServer {
 				csi.ControllerServiceCapability_RPC_CREATE_DELETE_VOLUME,
 				csi.ControllerServiceCapability_RPC_CREATE_DELETE_SNAPSHOT,
 				csi.ControllerServiceCapability_RPC_LIST_SNAPSHOTS,
+				csi.ControllerServiceCapability_RPC_CLONE_VOLUME,
 			}),
 	}
 }
@@ -178,19 +179,47 @@ func (cs *controllerServer) CreateVolume(ctx context.Context, req *csi.CreateVol
 			snapshotId := contentSource.GetSnapshot().GetSnapshotId()
 			snapshot, ok := hostPathVolumeSnapshots[snapshotId]
 			if !ok {
+				deleteHostpathVolume(volumeID)
 				return nil, status.Errorf(codes.NotFound, "cannot find snapshot %v", snapshotId)
 			}
 			if snapshot.ReadyToUse != true {
+				deleteHostpathVolume(volumeID)
 				return nil, status.Errorf(codes.Internal, "Snapshot %v is not yet ready to use.", snapshotId)
 			}
 			snapshotPath := snapshot.Path
 			args := []string{"zxvf", snapshotPath, "-C", path}
 			executor := utilexec.New()
 			out, err := executor.Command("tar", args...).CombinedOutput()
 			if err != nil {
+				deleteHostpathVolume(volumeID)
 				return nil, status.Error(codes.Internal, fmt.Sprintf("failed pre-populate data for volume: %v: %s", err, out))
 			}
 		}
+		if srcVolume := contentSource.GetVolume(); srcVolume != nil {
+			srcVolumeID := srcVolume.GetVolumeId()
+			hostPathVolume, ok := hostPathVolumes[srcVolumeID]
+			if !ok {
+				deleteHostpathVolume(volumeID)
+				return nil, status.Error(codes.NotFound, "source volumeID does not exist, are source/destination in the same storage class?")
+			}
+			srcPath := hostPathVolume.VolPath
+			isEmpty, err := hostPathIsEmpty(srcPath)
+			if err != nil {
+				deleteHostpathVolume(volumeID)
+				return nil, status.Error(codes.Internal, fmt.Sprintf("failed verification check of source hostpath volume: %s: %v", srcVolumeID, err))
+			}
+
+			// If the source hostpath volume is empty it's a noop and we just move along, otherwise the cp call will fail with a a file stat error DNE
+			if !isEmpty {
+				args := []string{"-a", srcPath + "/*", path + "/"}
+				executor := utilexec.New()
+				out, err := executor.Command("cp", args...).CombinedOutput()
+				if err != nil {
+					deleteHostpathVolume(volumeID)
+					return nil, status.Error(codes.Internal, fmt.Sprintf("failed pre-populate data (clone) for volume: %s: %s", volumeID, out))
+				}
+			}
+		}
 	}
 
 	createVolumeResponse := &csi.CreateVolumeResponse{}

pkg/hostpath/hostpath.go

@@ -18,6 +18,7 @@ package hostpath
 
 import (
 	"fmt"
+	"io"
 	"os"
 
 	"github.com/golang/glog"
@@ -169,10 +170,27 @@ func createHostpathVolume(volID, name string, cap int64, volAccessType accessTyp
 
 // deleteVolume deletes the directory for the hostpath volume.
 func deleteHostpathVolume(volID string) error {
+	glog.V(4).Infof("deleting hostpath volume: %s", volID)
 	path := getVolumePath(volID)
 	if err := os.RemoveAll(path); err != nil {
 		return err
 	}
 	delete(hostPathVolumes, volID)
 	return nil
 }
+
+// hostPathIsEmpty is a simple check to determine if the specified hostpath directory
+// is empty or not.
+func hostPathIsEmpty(p string) (bool, error) {
+	f, err := os.Open(p)
+	if err != nil {
+		return true, fmt.Errorf("unable to open hostpath volume, error: %v", err)
+	}
+	defer f.Close()
+
+	_, err = f.Readdir(1)
+	if err == io.EOF {
+		return true, nil
+	}
+	return false, err
+}