Introduce dedupused/dedupsaved pool properties

[amotin]

Currently there is only a dedup ratio reported via pool properties. If dedup is enabled only for some datasets, it is impossible to say how much space the ratio actually covers. Fix this by introducing dedupused/dedupsaved pool properties, similar to earlier added block cloning ones. Combined with work to expose allocation classes stats, it should give user-space enough visibility to correlate zpool list and zfs list space numbers.

How Has This Been Tested?

mav@genoa1:/optane# zpool get all | egrep ' (dedup|bclo)'
optane  dedupratio                     5.00x                          -
optane  bcloneused                     0                              -
optane  bclonesaved                    0                              -
optane  bcloneratio                    1.00x                          -
optane  dedup_table_size               288K                           -
optane  dedup_table_quota              auto                           default
optane  dedupused                      65M                            -
optane  dedupsaved                     260M                           -

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)
• Quality assurance (non-breaking change which makes the code more robust against bugs)
• 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.

[ryan-moeller]

These properties can be added to tests/zfs-tests/tests/functional/cli_root/zpool_get/zpool_get_parsable.cfg as well. It looks like the values should always be parsable.

dedupused will be redundant with dedup_stats.deflated_size in the json status output, but that is harmless.

[ryan-moeller]

I'll bump the man page date in #18238 after this.

[amotin]

These properties can be added to tests/zfs-tests/tests/functional/cli_root/zpool_get/zpool_get_parsable.cfg as well. It looks like the values should always be parsable.

Added.