Description of problem:
Can restore a filesystem PVC from the snapshot taken from the block PVC. And the restored PVC can be used by a Pod correctly. Once the regular user did a misoperation then the snapshot will be damaged.

Version-Release number of selected component (if applicable):
4.8.0-0.nightly-2021-03-08-184701

How reproducible:
Always

Steps to Reproduce:
1. Create a block PVC
$ oc get pvc test-pvc-5 -ojson|jq .spec.volumeMode
"Block"
2. Create a volumesnapshotclass
$ oc get volumesnapshotclass
NAME                DRIVER            DELETIONPOLICY   AGE
csi-snapshotclass   ebs.csi.aws.com   Delete           26m
3. Take snapshot for PVC
$ oc get volumesnapshot
NAME         READYTOUSE   SOURCEPVC    SOURCESNAPSHOTCONTENT   RESTORESIZE   SNAPSHOTCLASS       SNAPSHOTCONTENT                                    CREATIONTIME   AGE
mysnapshot   true         test-pvc-5                           3Gi           csi-snapshotclass   snapcontent-8eb3fc3d-9bb7-46bb-b284-548c0c3af668   19m            19m
4. Create a restore pvc from the snapshot(didn't define the volumeMode)
$ cat restore-pvc.yaml 
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: restore-pvc
spec:
  storageClassName: gp2-csi
  dataSource:
    name: mysnapshot
    kind: VolumeSnapshot
    apiGroup: snapshot.storage.k8s.io
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 5Gi
5. Create a Pod consuming the restore pvc


Actual results:
If define spec.containers.volumeMounts.mountPath, restored volume will be formated and the data on it lost.
$ oc exec deployment-r-6f8888fc5b-r25gd -- df /mnt/storage
Filesystem     1K-blocks  Used Available Use% Mounted on
/dev/nvme2n1     5095040 20472   5058184   1% /mnt/storage

If define spec.containers.volumeDevices.devicePath, will report and data is safe:
  Warning  FailedMount             <invalid> (x2 over <invalid>)  kubelet                  Unable to attach or mount volumes: unmounted volumes=[local], unattached volumes=[default-token-c65mn local]: volume local has volumeMode Filesystem, but is specified in volumeDevices


Expected results:
Seems to block restoring a filesystem PVC is safer.

Master Log:

Node Log (of failed PODs):

PV Dump:

PVC Dump:

StorageClass Dump (if StorageClass used by PV/PVC):

Additional info: