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>

@@ -90,49 +90,40 @@
 zfeature_is_supported(const char *guid)
 {
         if (zfeature_checks_disable)
                 return (B_TRUE);
 
-        return (0 == zfeature_lookup_guid(guid, NULL));
-}
-
-int
-zfeature_lookup_guid(const char *guid, zfeature_info_t **res)
-{
-        for (int i = 0; i < SPA_FEATURES; i++) {
+        for (spa_feature_t i = 0; i < SPA_FEATURES; i++) {
                 zfeature_info_t *feature = &spa_feature_table[i];
-                if (strcmp(guid, feature->fi_guid) == 0) {
-                        if (res != NULL)
-                                *res = feature;
-                        return (0);
+                if (strcmp(guid, feature->fi_guid) == 0)
+                        return (B_TRUE);
                 }
-        }
-
-        return (ENOENT);
+        return (B_FALSE);
 }
 
 int
-zfeature_lookup_name(const char *name, zfeature_info_t **res)
+zfeature_lookup_name(const char *name, spa_feature_t *res)
 {
-        for (int i = 0; i < SPA_FEATURES; i++) {
+        for (spa_feature_t i = 0; i < SPA_FEATURES; i++) {
                 zfeature_info_t *feature = &spa_feature_table[i];
                 if (strcmp(name, feature->fi_uname) == 0) {
                         if (res != NULL)
-                                *res = feature;
+                                *res = i;
                         return (0);
                 }
         }
 
         return (ENOENT);
 }
 
 static void
-zfeature_register(int fid, const char *guid, const char *name, const char *desc,
-    boolean_t readonly, boolean_t mos, zfeature_info_t **deps)
+zfeature_register(spa_feature_t fid, const char *guid, const char *name,
+    const char *desc, boolean_t readonly, boolean_t mos,
+    const spa_feature_t *deps)
 {
         zfeature_info_t *feature = &spa_feature_table[fid];
-        static zfeature_info_t *nodeps[] = { NULL };
+        static spa_feature_t nodeps[] = { SPA_FEATURE_NONE };
 
         ASSERT(name != NULL);
         ASSERT(desc != NULL);
         ASSERT(!readonly || !mos);
         ASSERT3U(fid, <, SPA_FEATURES);

@@ -139,10 +130,11 @@
         ASSERT(zfeature_is_valid_guid(guid));
 
         if (deps == NULL)
                 deps = nodeps;
 
+        feature->fi_feature = fid;
         feature->fi_guid = guid;
         feature->fi_uname = name;
         feature->fi_desc = desc;
         feature->fi_can_readonly = readonly;
         feature->fi_mos = mos;

@@ -165,6 +157,10 @@
             "com.joyent:multi_vdev_crash_dump", "multi_vdev_crash_dump",
             "Crash dumps to multiple vdev pools.", B_FALSE, B_FALSE, NULL);
         zfeature_register(SPA_FEATURE_SPACEMAP_HISTOGRAM,
             "com.delphix:spacemap_histogram", "spacemap_histogram",
             "Spacemaps maintain space histograms.", B_TRUE, B_FALSE, NULL);
+        zfeature_register(SPA_FEATURE_EXTENSIBLE_DATASET,
+            "com.delphix:extensible_dataset", "extensible_dataset",
+            "Enhanced dataset functionality, used by other features.",
+            B_FALSE, B_FALSE, NULL);
 }