Description of problem:

When accessing a cinder-backed volume for the first time (where the corresponding cinder volume does not contain a filesystem yet) it gets formatted and mounted; the resulting mount point is owned by root:root mode 0755, so the pod uid can't write to it.

Version-Release number of selected component (if applicable):
openshift v3.1.0.4-5-gebe80f5
kubernetes v1.1.0-origin-1107-g4c8e6f4

How reproducible:
Always

Steps to Reproduce:
1. Create a volume in cinder, note its ID (e.g. d0f3cda0-cf89-45ae-8a79-fb083f6884f2)
2. Create a PersistentVolume to describe the cinder volume, e.g.

[root@master ~]# cat registry-pv.yaml 
apiVersion: "v1"
kind: "PersistentVolume"
metadata:
  name: "registry" 
spec:
  capacity:
    storage: "25Gi" 
  accessModes:
    - "ReadWriteOnce"
  cinder: 
    fsType: "ext3" 
    volumeID: "d0f3cda0-cf89-45ae-8a79-fb083f6884f2"
[root@master ~]# oc create -f registry-pv.yaml

3. Create a PersistentVolumeClaim to use the above PV:

[root@master ~]# cat registry-pvc.json 
{
    "apiVersion": "v1",
    "kind": "PersistentVolumeClaim",
    "metadata": {
        "name": "registry"
    },
    "spec": {
        "accessModes": [ "ReadWriteOnce" ],
        "resources": {
            "requests": {
                "storage": "25Gi"
            }
        }
    }
}
[root@master ~]# oc create -f registry-pvc.json

4. Use that claim in a DC. Using the docker-registry as an example here, something like:
# oc volume dc/docker-registry --add --name=registry-storage -t pvc --claim-name=registry --overwrite

resulting in this in the registry's DC:

      volumes:
      - name: registry-storage
        persistentVolumeClaim:
          claimName: registry

5. Wait for the above DC to be deployed (trigger if needed)

Actual results:

Looking at the node where the pod is running we can see the volume:

    [root@node2 ~]# grep cinder/registry /proc/mounts
    /dev/vdc /var/lib/origin/openshift.local.volumes/pods/f4f3e79b-ae4d-11e5-9a3c-fa163e8e7483/volumes/kubernetes.io~cinder/registry ext3 rw,seclabel,relatime,data=ordered 0 0

and we can see that the filesystem that was created there has its mount point owned by root, mode 755:

    [root@node2 ~]# ls -la /var/lib/origin/openshift.local.volumes/plugins/kubernetes.io/cinder/mounts/d0f3cda0-cf89-45ae-8a79-fb083f6884f2
    total 20
    drwxr-xr-x. 3 root root  4096 29 des 11:59 .
    drwxr-x---. 3 root root    49 29 des 12:03 ..
    drwx------. 2 root root 16384 29 des 11:59 lost+found

As a result, the pod can't write there:

  time="2015-12-30T04:38:07-05:00" level=error msg="An error occured" err.code=UNKNOWN err.detail="mkdir /registry/docker: permission denied" ...

Expected results:

Pods from the DC that has the RWO PVC can write to their new volume