Automatic merge from submit-queue
Document space shuttle style in controller/volume
Reverts #28813 and #28111.
@xiang90, I really appreciate the effort that went into your PRs (and think, in general, code simplification is a worthwhile effort), but the style in this controller was intentional to ensure that every branch is covered. The verbosity and branchyness of this controller stores a lot of context and knowledge about how this subsystem is meant to function, so we need to put them back in.
@kubernetes/sig-storage
cc @jsafrane @saad-ali @matchstick @thockin @childsb @rootfs
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