4168 ztest assertion failure in dbuf_undirty
4169 verbatim import causes zdb to segfault
4170 zhack leaves pool in ACTIVE state
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Eric Schrock <eric.schrock@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>

*** 1332,1349 ****
          ASSERT(dr->dr_dbuf == db);
  
          DB_DNODE_ENTER(db);
          dn = DB_DNODE(db);
  
-         /*
-          * Note:  This code will probably work even if there are concurrent
-          * holders, but it is untested in that scenerio, as the ZPL and
-          * ztest have additional locking (the range locks) that prevents
-          * that type of concurrent access.
-          */
-         ASSERT3U(refcount_count(&db->db_holds), ==, db->db_dirtycnt);
- 
          dprintf_dbuf(db, "size=%llx\n", (u_longlong_t)db->db.db_size);
  
          ASSERT(db->db.db_size != 0);
  
          /*
--- 1332,1341 ----