cephfs: detect corrupt ceph-fuse mounts and try to remount

Mounts managed by ceph-fuse may get corrupted by e.g. the ceph-fuse process
exiting abruptly, or its parent container being terminated, taking down its
child processes with it.

This commit adds checks to NodeStageVolume and NodePublishVolume procedures
to detect whether a mountpoint in staging_target_path and/or target_path is
corrupted, and remount is performed if corruption is detected.

Signed-off-by: Robert Vasek <robert.vasek@cern.ch>

deploy/cephfs/kubernetes/csi-cephfsplugin.yaml

@@ -100,6 +100,8 @@ spec:
               mountPath: /etc/ceph-csi-config/
             - name: keys-tmp-dir
               mountPath: /tmp/csi/keys
+            - name: ceph-csi-mountinfo
+              mountPath: /csi/mountinfo
         - name: liveness-prometheus
           securityContext:
             privileged: true
@@ -164,6 +166,10 @@ spec:
           emptyDir: {
             medium: "Memory"
           }
+        - name: ceph-csi-mountinfo
+          hostPath:
+            path: /var/lib/kubelet/plugins/cephfs.csi.ceph.com/mountinfo
+            type: DirectoryOrCreate
 ---
 # This is a service to expose the liveness metrics
 apiVersion: v1