1693 persistent 'comment' field for a zpool

@@ -203,10 +203,15 @@
                 spa_prop_add_list(*nvp, ZPOOL_PROP_VERSION, NULL, version, src);
         }
 
         spa_prop_add_list(*nvp, ZPOOL_PROP_GUID, NULL, spa_guid(spa), src);
 
+        if (spa->spa_comment != NULL) {
+                spa_prop_add_list(*nvp, ZPOOL_PROP_COMMENT, spa->spa_comment,
+                    0, ZPROP_SRC_LOCAL);
+        }
+
         if (spa->spa_root != NULL)
                 spa_prop_add_list(*nvp, ZPOOL_PROP_ALTROOT, spa->spa_root,
                     0, ZPROP_SRC_LOCAL);
 
         if ((dp = list_head(&spa->spa_config_list)) != NULL) {

@@ -342,11 +347,11 @@
         while ((elem = nvlist_next_nvpair(props, elem)) != NULL) {
                 zpool_prop_t prop;
                 char *propname, *strval;
                 uint64_t intval;
                 objset_t *os;
-                char *slash;
+                char *slash, *check;
 
                 propname = nvpair_name(elem);
 
                 if ((prop = zpool_name_to_prop(propname)) == ZPROP_INVAL)
                         return (EINVAL);

@@ -462,10 +467,30 @@
                         if (slash[1] == '\0' || strcmp(slash, "/.") == 0 ||
                             strcmp(slash, "/..") == 0)
                                 error = EINVAL;
                         break;
 
+                case ZPOOL_PROP_COMMENT:
+                        if ((error = nvpair_value_string(elem, &strval)) != 0)
+                                break;
+                        for (check = strval; *check != '\0'; check++) {
+                                /*
+                                 * The kernel doesn't have an easy isprint()
+                                 * check.  For this kernel check, we merely
+                                 * check ASCII apart from DEL.  Fix this if
+                                 * there is an easy-to-use kernel isprint().
+                                 */
+                                if (*check >= 0x7f) {
+                                        error = EINVAL;
+                                        break;
+                                }
+                                check++;
+                        }
+                        if (strlen(strval) > ZPROP_MAX_COMMENT)
+                                error = E2BIG;
+                        break;
+
                 case ZPOOL_PROP_DEDUPDITTO:
                         if (spa_version(spa) < SPA_VERSION_DEDUP)
                                 error = ENOTSUP;
                         else
                                 error = nvpair_value_uint64(elem, &intval);

@@ -1040,10 +1065,15 @@
         }
         spa->spa_l2cache.sav_count = 0;
 
         spa->spa_async_suspended = 0;
 
+        if (spa->spa_comment != NULL) {
+                spa_strfree(spa->spa_comment);
+                spa->spa_comment = NULL;
+        }
+
         spa_config_exit(spa, SCL_ALL, FTAG);
 }
 
 /*
  * Load (or re-load) the current list of vdevs describing the active spares for

@@ -1755,17 +1785,22 @@
 spa_load(spa_t *spa, spa_load_state_t state, spa_import_type_t type,
     boolean_t mosconfig)
 {
         nvlist_t *config = spa->spa_config;
         char *ereport = FM_EREPORT_ZFS_POOL;
+        char *comment;
         int error;
         uint64_t pool_guid;
         nvlist_t *nvl;
 
         if (nvlist_lookup_uint64(config, ZPOOL_CONFIG_POOL_GUID, &pool_guid))
                 return (EINVAL);
 
+        ASSERT(spa->spa_comment == NULL);
+        if (nvlist_lookup_string(config, ZPOOL_CONFIG_COMMENT, &comment) == 0)
+                spa->spa_comment = spa_strdup(comment);
+
         /*
          * Versioning wasn't explicitly added to the label until later, so if
          * it's not present treat it as the initial version.
          */
         if (nvlist_lookup_uint64(config, ZPOOL_CONFIG_VERSION,

@@ -5369,10 +5404,24 @@
                         /*
                          * 'readonly' and 'cachefile' are also non-persisitent
                          * properties.
                          */
                         break;
+                case ZPOOL_PROP_COMMENT:
+                        VERIFY(nvpair_value_string(elem, &strval) == 0);
+                        if (spa->spa_comment != NULL)
+                                spa_strfree(spa->spa_comment);
+                        spa->spa_comment = spa_strdup(strval);
+                        /*
+                         * We need to dirty the configuration on all the vdevs
+                         * so that their labels get updated.  It's unnecessary
+                         * to do this for pool creation since the vdev's
+                         * configuratoin has already been dirtied.
+                         */
+                        if (tx->tx_txg != TXG_INITIAL)
+                                vdev_config_dirty(spa->spa_root_vdev);
+                        break;
                 default:
                         /*
                          * Set pool property values in the poolprops mos object.
                          */
                         if (spa->spa_pool_props_object == 0) {