What problem are we solving?

Even if multiple pods use the same volume, the driver will fork a child process for each of them to mount the volume. This is wasteful of resources and bad for management.

How are we solving the problem?

The idea is that pods using the same volume need to share a weed mount child process.
We currently solve this problem based on the CSI specification.

1. When a volume is first used on a node, NodeStageVolume will fork a child process to mount it to host's /var/lib/kubelet/plugins/kubernetes.io/csi/pv/<pvc>/globalmount directory.
2. Later when other pod uses the volume, NodePublishVolume just needs to create a symbolic link /var/lib/kubelet/pods/<pod>/volumes/kubernetes.io~csi/<pvc>/mount to the /var/lib/kubelet/plugins/kubernetes.io/csi/pv/<pvc>/globalmount directory.
3. If the pod using the volume on the node is deleted, then NodeUnpublishVolume only needs to delete the corresponding symbolic link /var/lib/kubelet/pods/<pod>/volumes/kubernetes.io~csi/<pvc>/mount.
4. Finally, when the volume is not used by any pods on the node, NodeUnstageVolume will unmount the volume.

Additionally, according to the specification, we also consider scenarios for handling concurrent calls.
https://github.com/container-storage-interface/spec/blob/master/spec.md#concurrency

Checks

• I have tested the above scenarios if possible.