Fix false assertion in dmu_tx_dirty_buf() on cloning

[amotin]

Same as writes block cloning can increase block size and number of indirection levels. That means it can dirty block 0 at level 0 or at new top indirection level without explicitly holding them.

How Has This Been Tested?

Thanks to @ixhamza this reproduction was found and now addressed:

truncate -s 1G /tmp/file_vdev
zpool create tank /tmp/file_vdev -O mountpoint=/mnt/tank
zfs create -o recordsize=128k tank/src
zfs create -o recordsize=128k tank/dst
# Write 1024 blocks
dd if=/dev/urandom of=/mnt/tank/src/f1 bs=128k count=1024 oflag=direct
zpool sync
# Clone 1024 blocks at 1024 block offset
/usr/share/zfs/zfs-tests/bin/clonefile -f /mnt/tank/src/f1 /mnt/tank/dst/f1_clone 0 134217728 134217728

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.

[robn]

Oh, that's subtle. Nice.

Worth a test case, since you've got the steps right there?

[behlendorf]

Ah, good find.

[amotin]

Thanks @ixhamza for the test. Included.