### Action Required

* ACTION REQUIRED: Removes defaulting of CSI file system type to ext4. All the production drivers listed under https://kubernetes-csi.github.io/docs/drivers.html were inspected and should not be impacted after this change. If you are using a driver not in that list, please test the drivers on an updated test cluster first. ([#65499](https://github.com/kubernetes/kubernetes/pull/65499), [@krunaljain](https://github.com/krunaljain))

- Promote CSIMigrationOpenStack to Beta (off by default since it requires installation of the OpenStack Cinder CSI Driver. The in-tree AWS OpenStack Cinder driver "kubernetes.io/cinder" was deprecated in 1.16 and will be removed in 1.20. Users should enable CSIMigration + CSIMigrationOpenStack features and install the OpenStack Cinder CSI Driver (https://github.com/kubernetes/cloud-provider-openstack) to avoid disruption to existing Pod and PVC objects at that time. Users should...

  by default. The CSI drivers can make use of the `secretRef` values passed in `NodeExpansion`
  request optionally sent by the CSI Client from this release onwards. ([#121303](https://github.com/kubernetes/kubernetes/pull/121303), [@humblec](https://github.com/humblec))

every node, instead of being compiled into the Kubernetes binary. See [example](examples/volumes/flexvolume/README.md) for details.
  * vendor volumes into a pod. It expects vendor drivers are installed in the
volume plugin path on each kubelet node. This is an alpha feature and may
change in future.

### Deprecation of FlexVolume

FlexVolume is deprecated. Out-of-tree CSI driver is the recommended way to write volume drivers in Kubernetes.
See [this doc](https://github.com/kubernetes/community/blob/master/sig-storage/volume-plugin-faq.md#kubernetes-volume-plugin-faq-for-storage-vendors) for more information.
Maintainers of FlexVolume drivers should implement a CSI driver and move users of FlexVolume to CSI.

- This release added support for `NodeExpandSecret` for CSI driver client which enables the CSI drivers to make use of this secret while performing node expansion operation based on the user request. Previously there was no secret  provided as part of the `nodeexpansion` call, thus CSI drivers did not make use of the same while expanding the volume at the node side. ([#105963](https://github.com/kubernetes/kubernetes/pull/105963),...

* ACTION REQUIRED: Removes defaulting of CSI file system type to ext4. All the production drivers listed under https://kubernetes-csi.github.io/docs/drivers.html were inspected and should not be impacted after this change. If you are using a driver not in that list, please test the drivers on an updated test cluster first. ([#65499](https://github.com/kubernetes/kubernetes/pull/65499), [@krunaljain](https://github.com/krunaljain))

Fixed kubelet so it would no longer crash when a DRA(Dynamic Resource Allocation) driver returns a nil as part of the Node(Un)PrepareResources response instead of an empty struct (Did not affect drivers written in Go, first showed up with a driver written in Rust). returns a nil as part of the Node(Un)PrepareResources response instead of an empty struct (did not affect drivers written in Go, first showed up with a driver written in Rust). ([#124091](https://github.com/kubernetes/kubernetes/pull/124091),...

  as it requires installation of AzureFile CSI Driver. Users should enable CSIMigration and
  CSIMigrationAzureFile features and install the [AzureFile CSI Driver](https://github.com/kubernetes-sigs/azurefile-csi-driver)
  to avoid disruption to existing Pod and PVC objects at that time. Azure File CSI driver does not support using same persistent

    * ACTION REQUIRED: the alpha CRDs are no longer used and drivers will need to be updated to use the beta APIs.
    * The support for `_` in the CSI driver name will be dropped as the CSI Spec does not allow that. 

### Other notable changes