3740 Poor ZFS send / receive performance due to snapshot hold / release processing
Submitted by: Steven Hartland <steven.hartland@multiplay.co.uk>

*** 24,33 ****
--- 24,34 ----
   * Portions Copyright 2011 Martin Matuska
   * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
   * Copyright (c) 2012, Joyent, Inc. All rights reserved.
   * Copyright (c) 2013 by Delphix. All rights reserved.
   * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
+  * Copyright (c) 2013 Steven Hartland. All rights reserved.
   */
  
  /*
   * ZFS ioctls.
   *
*** 4978,4997 ****
   */
  /* ARGSUSED */
  static int
  zfs_ioc_release(const char *pool, nvlist_t *holds, nvlist_t *errlist)
  {
-         nvpair_t *pair;
- 
-         /*
-          * The release may cause the snapshot to be destroyed; make sure it
-          * is not mounted.
-          */
-         for (pair = nvlist_next_nvpair(holds, NULL); pair != NULL;
-             pair = nvlist_next_nvpair(holds, pair))
-                 zfs_unmount_snap(nvpair_name(pair));
- 
          return (dsl_dataset_user_release(holds, errlist));
  }
  
  /*
   * inputs:
--- 4979,4988 ----