vSphere. ([#59328](https://github.com/kubernetes/kubernetes/pull/59328), [@divyenpatel](https://github.com/divyenpatel))

* Emit number of bound and unbound persistent volumes as Metrics. This PR adds four kinds of Volume Metrics for kube-controller-manager: bound PVC numbers, unbound PVC numbers, bound PV numbers and unbound PV numbers. The PVC metrics use namespace as dimension and the PV metrics use StorageClassName as its dimension. With these metrics we can better monitor the use...

* kubeadm: Fixed support of node certificates when joining a cluster ([#69328](https://github.com/kubernetes/kubernetes/pull/69328), [@bart0sh](https://github.com/bart0sh))
* Fix an issue where filesystems are not unmounted when a backend is not reachable and returns EIO. ([#67097](https://github.com/kubernetes/kubernetes/pull/67097), [@chakri-nelluri](https://github.com/chakri-nelluri))

* Check if pathExists before performing Unmount ([#39311](https://github.com/kubernetes/kubernetes/pull/39311), [@rkouj](https://github.com/rkouj))
* Unmount operation should not fail if volume is already unmounted ([#38547](https://github.com/kubernetes/kubernetes/pull/38547), [@rkouj](https://github.com/rkouj))

- Content-type and verb for request metrics are now bounded to a known set. ([#89451](https://github.com/kubernetes/kubernetes/pull/89451), [@logicalhan](https://github.com/logicalhan)) [SIG API Machinery and Instrumentation]

## Changelog since v1.18.8

## Changes by Kind

### Bug or Regression

- "unbound immediate PersistentVolumeClaims" causes UnschedulableAndUnresolvable status rather than an Error in the scheduler. ([#93892](https://github.com/kubernetes/kubernetes/pull/93892), [@ahg-g](https://github.com/ahg-g)) [SIG Apps and Storage]

- Fixed a bug in block volume expansion. ([#77317](https://github.com/kubernetes/kubernetes/pull/77317), [@gnufied](https://github.com/gnufied))
- Count PVCs that are unbound towards attach limit. ([#73863](https://github.com/kubernetes/kubernetes/pull/73863), [@gnufied](https://github.com/gnufied))

### VMware

* Check if pathExists before performing Unmount ([#39311](https://github.com/kubernetes/kubernetes/pull/39311), [@rkouj](https://github.com/rkouj))
* Unmount operation should not fail if volume is already unmounted ([#38547](https://github.com/kubernetes/kubernetes/pull/38547), [@rkouj](https://github.com/rkouj))

* Fix potential panic when getting azure load balancer status ([#68609](https://github.com/kubernetes/kubernetes/pull/68609), [@feiskyer](https://github.com/feiskyer))
* Fix an issue where filesystems are not unmounted when a backend is not reachable and returns EIO. ([#67097](https://github.com/kubernetes/kubernetes/pull/67097), [@chakri-nelluri](https://github.com/chakri-nelluri))

- Unmounted volumes correctly for reconstructed volumes even if mount operation fails after kubelet restart. ([#110670](https://github.com/kubernetes/kubernetes/pull/110670), [@gnufied](https://github.com/gnufied))

</li>
<li>
	Both types have identical structure and their element types
	unify exactly.
</li>
<li>
	Exactly one type is an <a href="#Type_inference">unbound</a>
	type parameter, and all the types in its type set unify with
	the other type
	per the unification rules for <code>≡<sub>A</sub></code>
	(loose unification at the top level and exact unification