* Flex volume plugin is updated to support attach/detach interfaces. It broke backward compatibility. Please update your drivers and implement the new callouts.  ([#41804](https://github.com/kubernetes/kubernetes/pull/41804), [@chakri-nelluri](https://github.com/chakri-nelluri))

## Notable Features

- `CSINodeExpandSecret` feature has been promoted to `GA` in this release and is enabled
  by default. The CSI drivers can make use of the `secretRef` values passed in `NodeExpansion`

* Bug fixes

  * Fixes issue with Flexvolume, introduced in 1.6.0, where drivers without an attacher would fail (node indefinitely waiting for attach). A driver API addition is introduced: drivers that don't implement attach should return attach: false on init. ([#47503](https://github.com/kubernetes/kubernetes/pull/47503), [@chakri-nelluri](https://github.com/chakri-nelluri))

    * 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

### Feature

- 'Added selector validation to `HorizontalPodAutoscaler`: when multiple HPAs
  select the same set of Pods, scaling now will be disabled for those HPAs with
  the reason `AmbiguousSelector`. This change also covers a case when multiple HPAs
  point to the same deployment.'
   ([#112011](https://github.com/kubernetes/kubernetes/pull/112011), [@pbeschetnov](https://github.com/pbeschetnov))

* 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))

  passed a file which contains RBAC roles, rolebindings, clusterroles, or
  clusterrolebindings, this command computes covers and adds the missing rules.
  The logic required to properly apply RBAC permissions is more complicated
  than a JSON merge because you have to compute logical covers operations between
  rule sets. This means that we cannot use `kubectl apply` to update RBAC roles

- Metric names for CSI and flexvolume drivers will include the driver name as well as the CSI plugin name. ([#96474](https://github.com/kubernetes/kubernetes/pull/96474), [@mattcary](https://github.com/mattcary)) [SIG Instrumentation and Storage]

  // +optional
  optional StorageOSVolumeSource storageos = 27;

  // csi (Container Storage Interface) represents ephemeral storage that is handled by certain external CSI drivers (Beta feature).
  // +optional
  optional CSIVolumeSource csi = 28;

  // ephemeral represents a volume that is handled by a cluster storage driver.

of the beta plugin registration directory `{kubelet_root_dir}/plugins/` for registration of external drivers via the kubelet plugin registration protocol is deprecated in favor of `{kubelet_root_dir}/plugins_registry/`. Support for the old directory is planned to be removed in v1.15. Device plugin and CSI storage drivers should switch to the new directory prior to v1.15. Only CSI storage drivers that support 0.x versions of the CSI API are allowed in the old directory. ([#70494](https://github.c...