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passthrough readOnly to subpath
**What this PR does / why we need it**:
If a volume is mounted as readonly, or subpath volumeMount is configured as readonly, then the subpath bind mount should be readonly.
**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes#62752
**Special notes for your reviewer**:
**Release note**:
```release-note
Fixes issue where subpath readOnly mounts failed
```
Users must not be allowed to step outside the volume with subPath.
Therefore the final subPath directory must be "locked" somehow
and checked if it's inside volume.
On Windows, we lock the directories. On Linux, we bind-mount the final
subPath into /var/lib/kubelet/pods/<uid>/volume-subpaths/<container name>/<subPathName>,
it can't be changed to symlink user once it's bind-mounted.
Kubelet makes sure that /var/lib/kubelet is rshared when it starts.
If not, it bind-mounts it with rshared propagation to containers
that mount volumes to /var/lib/kubelet can benefit from mount propagation.
fsGroup check will be enforcing that if a volume has already been
mounted by one pod and another pod wants to mount it but has a different
fsGroup value, this mount operation will not be allowed.
this is a workaround for the unmount device issue caused by gci mounter. In GCI cluster, if gci mounter is used for mounting, the container started by mounter script will cause additional mounts created in the container. Since these mounts are irrelavant to the original mounts, they should be not considered when checking the mount references. By comparing the mount path prefix, those additional mounts can be filtered out.
Plan to work on better approach to solve this issue.
# *** ERROR: *** docs are out of sync between cli and markdown
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# Your commit will be aborted unless you regenerate docs.
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