feat(shared): adding shared mount support ZFSPV volumes

Applications who wants to share a volume can use below storageclass
to make their volumes shared by multiple pods

```yaml
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-zfspv
parameters:
  shared: "yes"
  fstype: "zfs"
  poolname: "zfspv-pool"
provisioner: zfs.csi.openebs.io
```

Now the provisioned volume using this storageclass can be used by multiple pods.
Here pods have to make sure of the data consistency and have to have locking mechanism.
One thing to note here is pods will be scheduled to the node where volume is present
so that all the pods can use the same volume as they can access it locally only.
This was we can avoid the NFS overhead and can get the optimal performance also.

Signed-off-by: Pawan <pawan@mayadata.io>

pkg/apis/openebs.io/zfs/v1/zfsvolume.go

@@ -193,6 +193,13 @@ type VolumeInfo struct {
 	// FsType can not be modified once volume has been provisioned.
 	// Default Value: ext4.
 	FsType string `json:"fsType,omitempty"`
+
+	// Shared specifies where the volume can be shared among multiple pods.
+	// If it is not set to "yes", then the ZFS-LocalPV Driver will not allow
+	// the volumes to be mounted by more than one pods.
+	// +kubebuilder:validation:Required
+	// +kubebuilder:validation:Enum=yes;no
+	Shared string `json:"shared,omitempty"`
 }
 
 type VolStatus struct {

pkg/builder/volbuilder/build.go

@@ -172,6 +172,12 @@ func (b *Builder) WithFsType(fstype string) *Builder {
 	return b
 }
 
+// WithShared sets where filesystem is shared or not
+func (b *Builder) WithShared(shared string) *Builder {
+	b.volume.Object.Spec.Shared = shared
+	return b
+}
+
 // WithSnapshot sets Snapshot name for creating clone volume
 func (b *Builder) WithSnapshot(snap string) *Builder {
 	b.volume.Object.Spec.SnapName = snap

pkg/driver/controller.go

@@ -98,6 +98,7 @@ func CreateZFSVolume(req *csi.CreateVolumeRequest) (string, error) {
 	tp := parameters["thinprovision"]
 	schld := parameters["scheduler"]
 	fstype := parameters["fstype"]
+	shared := parameters["shared"]
 
 	vtype := zfs.GetVolumeType(fstype)
 
@@ -124,6 +125,7 @@ func CreateZFSVolume(req *csi.CreateVolumeRequest) (string, error) {
 		WithVolumeType(vtype).
 		WithVolumeStatus(zfs.ZFSStatusPending).
 		WithFsType(fstype).
+		WithShared(shared).
 		WithCompression(compression).Build()
 
 	if err != nil {

pkg/driver/grpc.go

@@ -69,7 +69,7 @@ func logGRPC(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, h
 
 	log := isInfotrmativeLog(info.FullMethod)
 	if log == true {
-		klog.Infof("GRPC call: %s\n requests %s", info.FullMethod, protosanitizer.StripSecrets(req))
+		klog.Infof("GRPC call: %s requests %s", info.FullMethod, protosanitizer.StripSecrets(req))
 	}
 
 	resp, err := handler(ctx, req)

pkg/zfs/mount.go

@@ -147,24 +147,27 @@ func verifyMountRequest(vol *apis.ZFSVolume, mountpath string) error {
 		return status.Errorf(codes.Internal, "verifyMount: GetVolumePath failed %s", err.Error())
 	}
 
-	/*
-	 * This check is the famous *Wall Of North*
-	 * It will not let the volume to be mounted
-	 * at more than two places. The volume should
-	 * be unmounted before proceeding to the mount
-	 * operation.
-	 */
-	currentMounts, err := GetMounts(devicePath)
-	if err != nil {
-		logrus.Errorf("can not get mounts for volume:%s dev %s err: %v",
-			vol.Name, devicePath, err.Error())
-		return status.Errorf(codes.Internal, "verifyMount: Getmounts failed %s", err.Error())
-	} else if len(currentMounts) >= 1 {
-		logrus.Errorf(
-			"can not mount, volume:%s already mounted dev %s mounts: %v",
-			vol.Name, devicePath, currentMounts,
-		)
-		return status.Errorf(codes.Internal, "verifyMount: device already mounted at %s", currentMounts)
+	// if it is not a shared volume, then make sure it is not mounted to more than one path
+	if vol.Spec.Shared != "yes" {
+		/*
+		 * This check is the famous *Wall Of North*
+		 * It will not let the volume to be mounted
+		 * at more than two places. The volume should
+		 * be unmounted before proceeding to the mount
+		 * operation.
+		 */
+		currentMounts, err := GetMounts(devicePath)
+		if err != nil {
+			logrus.Errorf("can not get mounts for volume:%s dev %s err: %v",
+				vol.Name, devicePath, err.Error())
+			return status.Errorf(codes.Internal, "verifyMount: Getmounts failed %s", err.Error())
+		} else if len(currentMounts) >= 1 {
+			logrus.Errorf(
+				"can not mount, volume:%s already mounted dev %s mounts: %v",
+				vol.Name, devicePath, currentMounts,
+			)
+			return status.Errorf(codes.Internal, "verifyMount: device already mounted at %s", currentMounts)
+		}
 	}
 	return nil
 }