cstyle fixes
dsl_dataset_set_fsid_guid should use ZFS_SPACE_CHECK_RESERVED
dsl_dataset_set_fsid_guid _check and _sync func declared static,
removed from dsl_dataset.h
rewrite unique_valid
6333 ZFS should let the user specify or modify the fsid_guid of a dataset

@@ -97,10 +97,25 @@
         mutex_exit(&unique_mtx);
 
         return (un->un_value);
 }
 
+boolean_t
+unique_valid(uint64_t value)
+{
+        unique_t un_tofind;
+
+        un_tofind.un_value = value;
+
+        mutex_enter(&unique_mtx);
+        boolean_t rv = ((value & ~UNIQUE_MASK) == 0 &&
+            avl_find(&unique_avl, &un_tofind, NULL) == NULL);
+        mutex_exit(&unique_mtx);
+
+        return (rv);
+}
+
 void
 unique_remove(uint64_t value)
 {
         unique_t un_tofind;
         unique_t *un;