Add support for smart cloning in rbd

[Madhu-1]

below are the sub-tasks to achieve the smart cloning

• Implement stand-alone snapshot creation more info here (Add support for standalone snapshot creation #467)
• Implement rbd image flattening
• Implement rbd cloning from a snapshot
• Implement cloning image from another image (combined with above 3 implementations)
• Enable E2E testing for snapshot
• Add E2E testing for smart cloning

[zhucan]

@Madhu-1 I don't understand it that restore from snapshot not use “rbd rollback” but use "rbd clone" and the restore from snapshot not support flatten， why？

[Madhu-1]

we will support flatten with the new implementation

[dillaman]

@Madhu-1 I don't understand it that restore from snapshot not use “rbd rollback” but use "rbd clone" and the restore from snapshot not support flatten， why？

@zhucan From the point-of-view of k8s, the "restore" operation is to just create a new PV from the snapshot. Therefore, you cannot just rollback (plus it's very inefficient).

[zhucan]

@dillaman Thanks， There is plan to do volume clone for ceph-csi?

[dillaman]

@zhucan Indeed -- I believe that's what this issue is tracking.

[zhucan]

@dillaman Thanks

[Madhu-1]

I had a discussion with @dillaman since we are facing issue with the current approach. we are moving to a new implementation as detailed below

# CO create snapshot process
* create temporary RBD snapshot on source volume's RBD image
* RBD clone CO source volume's RBD image's snapshot to new RBD image
* remove temporary RBD snapshot on CO source volume's RBD image

# CO create volume from snapshot process
* serialize work on RBD snapshot image clone
* test RBD snapshot image clone's depth
* if depth over the hard limit (no soft-limit anymore), flatten clone
* create RBD snapshot on RBD snapshot image clone
* create RBD volume image clone from RBD snapshot image clone

# CO create volume from the volume process
* create RBD snapshot image as if running "CO create snapshot" process
* create RBD volume image as if running "CO create volume from snapshot" process

[Madhu-1]

update snapshot from alpha to beta once we change the design for snapshot and cloning

[Madhu-1]

This is fixed now closing this one