Currently it is possible that the mounter object stored in Mounted
Volume data structure in the actual state of kubelet volume manager is
nil if this information is recovered from state sync process. This will
cause nil pointer issue when calculating stats in volume_stat_calculator.
A quick fix is to not return the volume if its mounter is nil. A more
complete fix is to also recover mounter object when reconstructing the
volume data structure which will be addressed in PR #33616
This commit adds a new volume manager in kubelet that synchronizes
volume mount/unmount (and attach/detach, if attach/detach controller
is not enabled).
This eliminates the race conditions between the pod creation loop
and the orphaned volumes loops. It also removes the unmount/detach
from the `syncPod()` path so volume clean up never blocks the
`syncPod` loop.
Jing Xu