Fix dataset cloning and renaming to and from an encryption root

[mmatuska]

Motivation and Context

We intend to keep all datasets with an identical encryption root inside the child dataset hierarchy of the encryption root.

Currently it is forbidden to move an encrypted dataset ouside its encryption root but this is incomplete. We need to prevent cloning an encrypted dataset outside of its encryption root and renaming or cloning an unencrypted dataset under an encryption root.

Description

• forbid cloning of an encrypted dataset outside its encryption root
• forbid cloning an unencrypted dataset inside an encryption root
• forbit moving an unencrypted dataset inside an encryption root

How Has This Been Tested?

Tested on FreeBSD

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the OpenZFS code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• I have run the ZFS Test Suite with this change applied.
• All commit messages are properly formatted and contain Signed-off-by.

[scineram]

Could you explain why the latter two points are necessary? It seems creating unencrypted child is still allowed.

[rincebrain]

Renaming (or creating) an unencrypted one under an encryptionroot is explicitly supposed to be allowed right now, after being initially forbidden. #8870

[mmatuska]

I am withdrawing this PR. We can clone datasets outside the encryption root, as the cloned dataset remains tied to the originating snapshot and that makes the encryption root undeletable.