5056 ZFS deadlock on db_mtx and dn_holds
Reviewed by: Will Andrews <willa@spectralogic.com>
Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Approved by: Dan McDonald <danmcd@omniti.com>

*** 20,29 ****
--- 20,30 ----
   */
  /*
   * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
   * Copyright (c) 2013 by Delphix. All rights reserved.
   * Copyright (c) 2014, Joyent, Inc. All rights reserved.
+  * Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
   */
  
  #ifndef _SYS_DSL_DIR_H
  #define _SYS_DSL_DIR_H
  
*** 82,91 ****
--- 83,94 ----
          uint64_t dd_clones; /* dsl_dir objects */
          uint64_t dd_pad[13]; /* pad out to 256 bytes for good measure */
  } dsl_dir_phys_t;
  
  struct dsl_dir {
+         dmu_buf_user_t dd_dbu;
+ 
          /* These are immutable; no lock needed: */
          uint64_t dd_object;
          dsl_pool_t *dd_pool;
  
          /* Stable until user eviction; no lock needed: */
*** 117,126 ****
--- 120,130 ----
  {
          return (dd->dd_dbuf->db_data);
  }
  
  void dsl_dir_rele(dsl_dir_t *dd, void *tag);
+ void dsl_dir_async_rele(dsl_dir_t *dd, void *tag);
  int dsl_dir_hold(dsl_pool_t *dp, const char *name, void *tag,
      dsl_dir_t **, const char **tail);
  int dsl_dir_hold_obj(dsl_pool_t *dp, uint64_t ddobj,
      const char *tail, void *tag, dsl_dir_t **);
  void dsl_dir_name(dsl_dir_t *dd, char *buf);