27070 archive files are deleted but space is not reclaimed

@@ -27,7 +27,7 @@
 
 /*
  * Copyright 2012 Nexenta Systems, Inc.  All rights reserved.
- * Copyright (c) 2012 by Delphix. All rights reserved.
+ * Copyright (c) 2013 by Delphix. All rights reserved.
  */
 
 /*
@@ -374,6 +374,27 @@ nlm_gc(struct nlm_globals *g)
 		while ((hostp = TAILQ_FIRST(&g->nlm_idle_hosts)) != NULL) {
 			bool_t has_locks = FALSE;
 
+			/*
+			 * A busy client will prevent the idle timeout from
+			 * ever being reached but may have stale holds
+			 * associated with it. If these stale holds are for
+			 * vnodes which have been removed they will prevent
+			 * the file system from being able to reclaim the
+			 * file's space.
+			 *
+			 * To address this problem we unconditionally GC
+			 * the host's vholds every time the GC runs. Since
+			 * this is an expensive check, drop the global lock
+			 * and only hold the host lock.
+			 */
+			mutex_exit(&g->lock);
+			mutex_enter(&hostp->nh_lock);
+
+			nlm_host_gc_vholds(hostp);
+
+			mutex_exit(&hostp->nh_lock);
+			mutex_enter(&g->lock);
+
 			if (hostp->nh_idle_timeout > now)
 				break;
 
@@ -388,10 +409,10 @@ nlm_gc(struct nlm_globals *g)
 
 			/*
 			 * nlm_globals lock was dropped earlier because
-			 * garbage collecting of vholds and checking whether
-			 * host has any locks/shares are expensive operations.
+			 * checking is an expensive operation. In the worst
+			 * case it may need to visit every file lock on the
+			 * system.
 			 */
-			nlm_host_gc_vholds(hostp);
 			has_locks = nlm_host_has_locks(hostp);
 
 			mutex_exit(&hostp->nh_lock);
@@ -1032,7 +1053,7 @@ nlm_vhold_destroy(struct nlm_host *hostp, struct nlm_vhold *nvp)
 	    (mod_hash_val_t)&nvp) == 0);
 
 	TAILQ_REMOVE(&hostp->nh_vholds_list, nvp, nv_link);
-	VN_RELE(nvp->nv_vp);
+	VN_RELE_ASYNC(nvp->nv_vp, system_taskq);
 	nvp->nv_vp = NULL;
 
 	kmem_cache_free(nlm_vhold_cache, nvp);