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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>

@@ -159,27 +159,29 @@
  * decremented back to 0 to indicate that it has undone its on-disk format
  * changes.
  */
 
 typedef enum {
-        FEATURE_ACTION_ENABLE,
         FEATURE_ACTION_INCR,
         FEATURE_ACTION_DECR,
 } feature_action_t;
 
 /*
- * Checks that the features active in the specified object are supported by
+ * Checks that the active features in the pool are supported by
  * this software.  Adds each unsupported feature (name -> description) to
  * the supplied nvlist.
  */
 boolean_t
-feature_is_supported(objset_t *os, uint64_t obj, uint64_t desc_obj,
+spa_features_check(spa_t *spa, boolean_t for_write,
     nvlist_t *unsup_feat, nvlist_t *enabled_feat)
 {
+        objset_t *os = spa->spa_meta_objset;
         boolean_t supported;
         zap_cursor_t zc;
         zap_attribute_t za;
+        uint64_t obj = for_write ?
+            spa->spa_feat_for_write_obj : spa->spa_feat_for_read_obj;
 
         supported = B_TRUE;
         for (zap_cursor_init(&zc, os, obj);
             zap_cursor_retrieve(&zc, &za) == 0;
             zap_cursor_advance(&zc)) {

@@ -197,12 +199,12 @@
 
                         if (NULL != unsup_feat) {
                                 char *desc = "";
                                 char buf[MAXPATHLEN];
 
-                                if (zap_lookup(os, desc_obj, za.za_name,
-                                    1, sizeof (buf), buf) == 0)
+                                if (zap_lookup(os, spa->spa_feat_desc_obj,
+                                    za.za_name, 1, sizeof (buf), buf) == 0)
                                         desc = buf;
 
                                 VERIFY(nvlist_add_string(unsup_feat, za.za_name,
                                     desc) == 0);
                         }

@@ -211,27 +213,32 @@
         zap_cursor_fini(&zc);
 
         return (supported);
 }
 
-static int
-feature_get_refcount(objset_t *os, uint64_t read_obj, uint64_t write_obj,
-    zfeature_info_t *feature, uint64_t *res)
+/*
+ * Note: well-designed features will not need to use this; they should
+ * use spa_feature_is_enabled() and spa_feature_is_active() instead.
+ * However, this is non-static for zdb and zhack.
+ */
+int
+feature_get_refcount(spa_t *spa, zfeature_info_t *feature, uint64_t *res)
 {
         int err;
         uint64_t refcount;
-        uint64_t zapobj = feature->fi_can_readonly ? write_obj : read_obj;
+        uint64_t zapobj = feature->fi_can_readonly ?
+            spa->spa_feat_for_write_obj : spa->spa_feat_for_read_obj;
 
         /*
          * If the pool is currently being created, the feature objects may not
          * have been allocated yet.  Act as though all features are disabled.
          */
         if (zapobj == 0)
                 return (SET_ERROR(ENOTSUP));
 
-        err = zap_lookup(os, zapobj, feature->fi_guid, sizeof (uint64_t), 1,
-            &refcount);
+        err = zap_lookup(spa->spa_meta_objset, zapobj,
+            feature->fi_guid, sizeof (uint64_t), 1, &refcount);
         if (err != 0) {
                 if (err == ENOENT)
                         return (SET_ERROR(ENOTSUP));
                 else
                         return (err);

@@ -238,96 +245,93 @@
         }
         *res = refcount;
         return (0);
 }
 
-static int
-feature_do_action(objset_t *os, uint64_t read_obj, uint64_t write_obj,
-    uint64_t desc_obj, zfeature_info_t *feature, feature_action_t action,
+/*
+ * This function is non-static for zhack; it should otherwise not be used
+ * outside this file.
+ */
+void
+feature_sync(spa_t *spa, zfeature_info_t *feature, uint64_t refcount,
     dmu_tx_t *tx)
 {
-        int error;
-        uint64_t refcount;
-        uint64_t zapobj = feature->fi_can_readonly ? write_obj : read_obj;
+        uint64_t zapobj = feature->fi_can_readonly ?
+            spa->spa_feat_for_write_obj : spa->spa_feat_for_read_obj;
 
-        ASSERT(0 != zapobj);
-        ASSERT(zfeature_is_valid_guid(feature->fi_guid));
+        VERIFY0(zap_update(spa->spa_meta_objset, zapobj, feature->fi_guid,
+            sizeof (uint64_t), 1, &refcount, tx));
 
-        error = zap_lookup(os, zapobj, feature->fi_guid,
-            sizeof (uint64_t), 1, &refcount);
+        if (refcount == 0)
+                spa_deactivate_mos_feature(spa, feature->fi_guid);
+        else if (feature->fi_mos)
+                spa_activate_mos_feature(spa, feature->fi_guid);
+}
 
-        /*
-         * If we can't ascertain the status of the specified feature, an I/O
-         * error occurred.
+/*
+ * This function is non-static for zhack; it should otherwise not be used
+ * outside this file.
          */
-        if (error != 0 && error != ENOENT)
-                return (error);
+void
+feature_enable_sync(spa_t *spa, zfeature_info_t *feature, dmu_tx_t *tx)
+{
+        uint64_t zapobj = feature->fi_can_readonly ?
+            spa->spa_feat_for_write_obj : spa->spa_feat_for_read_obj;
 
-        switch (action) {
-        case FEATURE_ACTION_ENABLE:
+        ASSERT(0 != zapobj);
+        ASSERT(zfeature_is_valid_guid(feature->fi_guid));
+        ASSERT3U(spa_version(spa), >=, SPA_VERSION_FEATURES);
+
                 /*
                  * If the feature is already enabled, ignore the request.
                  */
-                if (error == 0)
-                        return (0);
-                refcount = 0;
-                break;
+        if (zap_contains(spa->spa_meta_objset, zapobj, feature->fi_guid) == 0)
+                return;
+
+        for (int i = 0; feature->fi_depends[i] != SPA_FEATURE_NONE; i++)
+                spa_feature_enable(spa, feature->fi_depends[i], tx);
+
+        VERIFY0(zap_update(spa->spa_meta_objset, spa->spa_feat_desc_obj,
+            feature->fi_guid, 1, strlen(feature->fi_desc) + 1,
+            feature->fi_desc, tx));
+        feature_sync(spa, feature, 0, tx);
+}
+
+static void
+feature_do_action(spa_t *spa, spa_feature_t fid, feature_action_t action,
+    dmu_tx_t *tx)
+{
+        uint64_t refcount;
+        zfeature_info_t *feature = &spa_feature_table[fid];
+        uint64_t zapobj = feature->fi_can_readonly ?
+            spa->spa_feat_for_write_obj : spa->spa_feat_for_read_obj;
+
+        ASSERT3U(fid, <, SPA_FEATURES);
+        ASSERT(0 != zapobj);
+        ASSERT(zfeature_is_valid_guid(feature->fi_guid));
+
+        ASSERT(dmu_tx_is_syncing(tx));
+        ASSERT3U(spa_version(spa), >=, SPA_VERSION_FEATURES);
+
+        VERIFY0(zap_lookup(spa->spa_meta_objset, zapobj, feature->fi_guid,
+            sizeof (uint64_t), 1, &refcount));
+
+        switch (action) {
         case FEATURE_ACTION_INCR:
-                if (error == ENOENT)
-                        return (SET_ERROR(ENOTSUP));
-                if (refcount == UINT64_MAX)
-                        return (SET_ERROR(EOVERFLOW));
+                VERIFY3U(refcount, !=, UINT64_MAX);
                 refcount++;
                 break;
         case FEATURE_ACTION_DECR:
-                if (error == ENOENT)
-                        return (SET_ERROR(ENOTSUP));
-                if (refcount == 0)
-                        return (SET_ERROR(EOVERFLOW));
+                VERIFY3U(refcount, !=, 0);
                 refcount--;
                 break;
         default:
                 ASSERT(0);
                 break;
         }
 
-        if (action == FEATURE_ACTION_ENABLE) {
-                int i;
-
-                for (i = 0; feature->fi_depends[i] != NULL; i++) {
-                        zfeature_info_t *dep = feature->fi_depends[i];
-
-                        error = feature_do_action(os, read_obj, write_obj,
-                            desc_obj, dep, FEATURE_ACTION_ENABLE, tx);
-                        if (error != 0)
-                                return (error);
-                }
-        }
-
-        error = zap_update(os, zapobj, feature->fi_guid,
-            sizeof (uint64_t), 1, &refcount, tx);
-        if (error != 0)
-                return (error);
-
-        if (action == FEATURE_ACTION_ENABLE) {
-                error = zap_update(os, desc_obj,
-                    feature->fi_guid, 1, strlen(feature->fi_desc) + 1,
-                    feature->fi_desc, tx);
-                if (error != 0)
-                        return (error);
-        }
-
-        if (action == FEATURE_ACTION_INCR && refcount == 1 && feature->fi_mos) {
-                spa_activate_mos_feature(dmu_objset_spa(os), feature->fi_guid);
-        }
-
-        if (action == FEATURE_ACTION_DECR && refcount == 0) {
-                spa_deactivate_mos_feature(dmu_objset_spa(os),
-                    feature->fi_guid);
-        }
-
-        return (0);
+        feature_sync(spa, feature, refcount, tx);
 }
 
 void
 spa_feature_create_zap_objects(spa_t *spa, dmu_tx_t *tx)
 {

@@ -351,84 +355,53 @@
 
 /*
  * Enable any required dependencies, then enable the requested feature.
  */
 void
-spa_feature_enable(spa_t *spa, zfeature_info_t *feature, dmu_tx_t *tx)
+spa_feature_enable(spa_t *spa, spa_feature_t fid, dmu_tx_t *tx)
 {
         ASSERT3U(spa_version(spa), >=, SPA_VERSION_FEATURES);
-        VERIFY3U(0, ==, feature_do_action(spa->spa_meta_objset,
-            spa->spa_feat_for_read_obj, spa->spa_feat_for_write_obj,
-            spa->spa_feat_desc_obj, feature, FEATURE_ACTION_ENABLE, tx));
+        ASSERT3U(fid, <, SPA_FEATURES);
+        feature_enable_sync(spa, &spa_feature_table[fid], tx);
 }
 
 void
-spa_feature_incr(spa_t *spa, zfeature_info_t *feature, dmu_tx_t *tx)
+spa_feature_incr(spa_t *spa, spa_feature_t fid, dmu_tx_t *tx)
 {
-        ASSERT(dmu_tx_is_syncing(tx));
-        ASSERT3U(spa_version(spa), >=, SPA_VERSION_FEATURES);
-        VERIFY3U(0, ==, feature_do_action(spa->spa_meta_objset,
-            spa->spa_feat_for_read_obj, spa->spa_feat_for_write_obj,
-            spa->spa_feat_desc_obj, feature, FEATURE_ACTION_INCR, tx));
+        feature_do_action(spa, fid, FEATURE_ACTION_INCR, tx);
 }
 
 void
-spa_feature_decr(spa_t *spa, zfeature_info_t *feature, dmu_tx_t *tx)
+spa_feature_decr(spa_t *spa, spa_feature_t fid, dmu_tx_t *tx)
 {
-        ASSERT(dmu_tx_is_syncing(tx));
-        ASSERT3U(spa_version(spa), >=, SPA_VERSION_FEATURES);
-        VERIFY3U(0, ==, feature_do_action(spa->spa_meta_objset,
-            spa->spa_feat_for_read_obj, spa->spa_feat_for_write_obj,
-            spa->spa_feat_desc_obj, feature, FEATURE_ACTION_DECR, tx));
+        feature_do_action(spa, fid, FEATURE_ACTION_DECR, tx);
 }
 
-/*
- * This interface is for debugging only. Normal consumers should use
- * spa_feature_is_enabled/spa_feature_is_active.
- */
-int
-spa_feature_get_refcount(spa_t *spa, zfeature_info_t *feature)
-{
-        int err;
-        uint64_t refcount;
-
-        if (spa_version(spa) < SPA_VERSION_FEATURES)
-                return (B_FALSE);
-
-        err = feature_get_refcount(spa->spa_meta_objset,
-            spa->spa_feat_for_read_obj, spa->spa_feat_for_write_obj,
-            feature, &refcount);
-        ASSERT(err == 0 || err == ENOTSUP);
-        return (err == 0 ? refcount : 0);
-}
-
 boolean_t
-spa_feature_is_enabled(spa_t *spa, zfeature_info_t *feature)
+spa_feature_is_enabled(spa_t *spa, spa_feature_t fid)
 {
         int err;
         uint64_t refcount;
 
+        ASSERT3U(fid, <, SPA_FEATURES);
         if (spa_version(spa) < SPA_VERSION_FEATURES)
                 return (B_FALSE);
 
-        err = feature_get_refcount(spa->spa_meta_objset,
-            spa->spa_feat_for_read_obj, spa->spa_feat_for_write_obj,
-            feature, &refcount);
+        err = feature_get_refcount(spa, &spa_feature_table[fid], &refcount);
         ASSERT(err == 0 || err == ENOTSUP);
         return (err == 0);
 }
 
 boolean_t
-spa_feature_is_active(spa_t *spa, zfeature_info_t *feature)
+spa_feature_is_active(spa_t *spa, spa_feature_t fid)
 {
         int err;
         uint64_t refcount;
 
+        ASSERT3U(fid, <, SPA_FEATURES);
         if (spa_version(spa) < SPA_VERSION_FEATURES)
                 return (B_FALSE);
 
-        err = feature_get_refcount(spa->spa_meta_objset,
-            spa->spa_feat_for_read_obj, spa->spa_feat_for_write_obj,
-            feature, &refcount);
+        err = feature_get_refcount(spa, &spa_feature_table[fid], &refcount);
         ASSERT(err == 0 || err == ENOTSUP);
         return (err == 0 && refcount > 0);
 }