2619 asynchronous destruction of ZFS file systems
2747 SPA versioning with zfs feature flags
Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <gwilson@delphix.com>
Reviewed by: Richard Lowe <richlowe@richlowe.net>
Reviewed by: Dan Kruchinin <dan.kruchinin@gmail.com>
Approved by: Dan McDonald <danmcd@nexenta.com>

*** 16,31 ****
--- 16,36 ----
   * fields enclosed by brackets "[]" replaced with your own identifying
   * information: Portions Copyright [yyyy] [name of copyright owner]
   *
   * CDDL HEADER END
   */
+ 
  /*
   * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
  
  /*
+  * Copyright (c) 2012 by Delphix. All rights reserved.
+  */
+ 
+ /*
   * The pool configuration repository is stored in /etc/zfs/zpool.cache as a
   * single packed nvlist.  While it would be nice to just read in this
   * file from userland, this wouldn't work from a local zone.  So we have to have
   * a zpool ioctl to return the complete configuration for all pools.  In the
   * global zone, this will be identical to reading the file and unpacking it in
*** 215,224 ****
--- 220,259 ----
          if (oldconfig)
                  *oldconfig = zhp->zpool_old_config;
          return (zhp->zpool_config);
  }
  
+ /*
+  * Retrieves a list of enabled features and their refcounts and caches it in
+  * the pool handle.
+  */
+ nvlist_t *
+ zpool_get_features(zpool_handle_t *zhp)
+ {
+         nvlist_t *config, *features;
+ 
+         config = zpool_get_config(zhp, NULL);
+ 
+         if (config == NULL || !nvlist_exists(config,
+             ZPOOL_CONFIG_FEATURE_STATS)) {
+                 int error;
+                 boolean_t missing = B_FALSE;
+ 
+                 error = zpool_refresh_stats(zhp, &missing);
+ 
+                 if (error != 0 || missing)
+                         return (NULL);
+ 
+                 config = zpool_get_config(zhp, NULL);
+         }
+ 
+         verify(nvlist_lookup_nvlist(config, ZPOOL_CONFIG_FEATURE_STATS,
+             &features) == 0);
+ 
+         return (features);
+ }
+ 
  /*
   * Refresh the vdev statistics associated with the given pool.  This is used in
   * iostat to show configuration changes and determine the delta from the last
   * time the function was called.  This function can fail, in case the pool has
   * been destroyed.