Side-port of OS-2943 zone stuck 'down': references still extant (illumos-joyent 4cb09b44b4f851905a0e8cccbd9bfc834acc2041)

@@ -8,11 +8,11 @@
  * source.  A copy of the CDDL is also available via the Internet at
  * http://www.illumos.org/license/CDDL.
  */
 
 /*
- * Copyright 2013, Joyent, Inc. All rights reserved.
+ * Copyright 2014, Joyent, Inc. All rights reserved.
  */
 
 /*
  * The ZFS/Zone I/O throttle and scheduler attempts to ensure fair access to
  * ZFS I/O resources for each zone.

@@ -1139,14 +1139,14 @@
         hrtime_t now, unow, udelta;
 
         if (zp->io_type == ZIO_TYPE_IOCTL)
                 return;
 
-        if ((zonep = zone_find_by_id(zp->io_zoneid)) == NULL)
+        if (zp->io_dispatched == 0)
                 return;
 
-        if (zp->io_dispatched == 0)
+        if ((zonep = zone_find_by_id(zp->io_zoneid)) == NULL)
                 return;
 
         now = gethrtime();
         unow = NANO_TO_MICRO(now);
         udelta = unow - NANO_TO_MICRO(zp->io_dispatched);