4171 clean up spa_feature_*() interfaces
4172 implement extensible_dataset feature for use by other zpool features
Reviewed by: Max Grossman <max.grossman@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>

@@ -47,13 +47,13 @@
 struct dsl_pool;
 
 #define DS_FLAG_INCONSISTENT    (1ULL<<0)
 #define DS_IS_INCONSISTENT(ds)  \
         ((ds)->ds_phys->ds_flags & DS_FLAG_INCONSISTENT)
+
 /*
- * Note: nopromote can not yet be set, but we want support for it in this
- * on-disk version, so that we don't need to upgrade for it later.
+ * Do not allow this dataset to be promoted.
  */
 #define DS_FLAG_NOPROMOTE       (1ULL<<1)
 
 /*
  * DS_FLAG_UNIQUE_ACCURATE is set if ds_unique_bytes has been correctly

@@ -69,10 +69,15 @@
 #define DS_FLAG_DEFER_DESTROY   (1ULL<<3)
 #define DS_IS_DEFER_DESTROY(ds) \
         ((ds)->ds_phys->ds_flags & DS_FLAG_DEFER_DESTROY)
 
 /*
+ * DS_FIELD_* are strings that are used in the "extensified" dataset zap object.
+ * They should be of the format <reverse-dns>:<field>.
+ */
+
+/*
  * DS_FLAG_CI_DATASET is set if the dataset contains a file system whose
  * name lookups should be performed case-insensitively.
  */
 #define DS_FLAG_CI_DATASET      (1ULL<<16)