([#37991](https://github.com/kubernetes/kubernetes/pull/37991), [@pwittrock](https://github.com/pwittrock))

* The strategicmerge patchMergeKey for VolumeMounts was changed from "name" to "mountPath".  This was necessary because the name field refers to the name of the Volume, and is not a unique key for the VolumeMount.  Multiple VolumeMounts will have the same Volume name if mounting the same volume more than once.  The "mountPath" is verified to be unique and can act as the mergekey.  ([#3...

* [alpha] Mount namespace propagation

  * The `VolumeMount.Propagation` field for `VolumeMount` in pod containers is now available.

  * You can now set `VolumeMount.Propagation` to `Bidirectional` to enable a particular mount for a container to propagate itself to the host or other containers.

* [alpha] Improve Flex volume deployment

* Reimplement 'pause' in C - smaller footprint all around ([#23009](https://github.com/kubernetes/kubernetes/pull/23009), [@uluyol](https://github.com/uluyol))
* Add subPath to mount a child dir or file of a volumeMount ([#22575](https://github.com/kubernetes/kubernetes/pull/22575), [@MikaelCluseau](https://github.com/MikaelCluseau))

### Other notable changes

* Update the GCI image to gci-dev-55-8872-18-0 ([#35243](https://github.com/kubernetes/kubernetes/pull/35243), [@maisem](https://github.com/maisem))
* Change merge key for VolumeMount to mountPath ([#35071](https://github.com/kubernetes/kubernetes/pull/35071), [@thockin](https://github.com/thockin))

* PodSpecs containing parent directory references such as `..` (for example, `../bar`) in hostPath volume path or in volumeMount subpaths must be changed to the simple absolute path. Backsteps `..` are no longer allowed.([#47290](https://github.com/kubernetes/kubernetes/pull/47290), [@jhorwit2](https://github.com/jhorwit2)).


### API Machinery

- kubeadm: Fixed unnecessary upgrades caused by undefined order of Volumes and VolumeMounts in manifests ([#70027](https://github.com/kubernetes/kubernetes/pull/70027), [@bart0sh](https://github.com/bart0sh))

* Fix `SubPath` printing of `VolumeMounts`. ([#70127](https://github.com/kubernetes/kubernetes/pull/70127), [@dtaniwaki](https://github.com/dtaniwaki))