zfsonlinux/zfs — pull request #2528 by dweeezil (2014-07-24 04:03:11+00:00)
Title: Illumos 4171, 4172 (beginning of new illumos/Delphix feature patch stack) - supersedes #2149 

4171 clean up spa_feature_*() interfaces
4172 implement extensible_dataset feature for use by other zpool features
Reviewed by: Max Grossman
Reviewed by: Christopher Siden
Reviewed by: George Wilson
Reviewed by: Jerry Jelinek
Approved by: Garrett D'Amore
Ported by: Tim Chase