cmd/zpool: deny creation and upgrade of zpools with block_cloning on FreeBSD

[Mattia-Pascal]

The block_cloning feature is still under active stabilization. To avoid accidentally enabling during create or during upgrade add a deny enable flag. The user can still explicitly enable after creation.

Signed-off-by: Mattia Pascal mattia.pascal42@hotmail.com
Requested by: Mateusz Guzik mjg@FreeBSD.org
Sponsored by: Rubicon Communications, LLC ("Netgate")

Motivation and Context

Description

How Has This Been Tested?

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.

[behlendorf]

@pjd @allanjude thoughts on this.

@Mattia-Pascal the zloop failures here are suspicious. There's backtraces in the logs are incomplete so I can't say for certain, but normally zloop passes and in this case both runs failed.

[pjd]

@pjd @allanjude thoughts on this.

@Mattia-Pascal the zloop failures here are suspicious. There's backtraces in the logs are incomplete so I can't say for certain, but normally zloop passes and in this case both runs failed.

I've added sysctl vfs.zfs.brt.enabled to FreeBSD (disabled by default) to control block cloning. I personally don't see the reason to complicate ZFS further with change like that. I haven't received any reports since the last round of fixes, but I can consider renaming sysctl to something like vfs.zfs.brt.experimental_enabled.
Something like this should be added to Linux too for the time being.
I want to keep block cloning disabled by default at least for 14.0 time frame.

[grahamperrin]

Thank you,

vfs.zfs.brt.enabled

vfs.zfs.bclone_enabled, I think; ⚙ D39613 zfs: Add vfs.zfs.bclone_enabled sysctl..

(If I'm missing a more recent commit: sorry.)

[behlendorf]

Something like this should be added to Linux too for the time being.

For the moment at least I don't think we need this on Linux since it hasn't been wired up to the VFS.

[rincebrain]

I would agree that this shouldn't be FreeBSD-specific. If it's going to be disabled by default, it should be disabled everywhere by default.

I'd also agree it shouldn't be marked enabled on a pool by default if we're going to have a tunable mitigating that anyway. (Really, I suppose the same argument kind of applies to hole_birth....)

(I haven't done any testing of the feature recently, and this is not a vote on its stability, I just don't think we should have this special-cased to FreeBSD-only...)

[behlendorf]

Closing, I'd prefer not to add this additional complexity. In addition, this feature has now been wired up on Linux and seen further stabilization.