Use taskq_wait_outstanding() function

Replace taskq_wait() with taskq_wait_oustanding().  This way callers
will only block until previously submitted tasks have been completed.
This was the previous behavior of task_wait() prior to the introduction
of taskq_wait_outstanding() so this isn't really a functionalty change
for these callers.

Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

module/zfs/metaslab.c

@@ -556,7 +556,7 @@ metaslab_group_passivate(metaslab_group_t *mg)
 		return;
 	}
 
-	taskq_wait(mg->mg_taskq);
+	taskq_wait_outstanding(mg->mg_taskq, 0);
 	metaslab_group_alloc_update(mg);
 
 	mgprev = mg->mg_prev;
@@ -1596,7 +1596,7 @@ metaslab_group_preload(metaslab_group_t *mg)
 	int m = 0;
 
 	if (spa_shutting_down(spa) || !metaslab_preload_enabled) {
-		taskq_wait(mg->mg_taskq);
+		taskq_wait_outstanding(mg->mg_taskq, 0);
 		return;
 	}
 

module/zfs/txg.c

@@ -471,7 +471,7 @@ txg_wait_callbacks(dsl_pool_t *dp)
 	tx_state_t *tx = &dp->dp_tx;
 
 	if (tx->tx_commit_cb_taskq != NULL)
-		taskq_wait(tx->tx_commit_cb_taskq);
+		taskq_wait_outstanding(tx->tx_commit_cb_taskq, 0);
 }
 
 static void

module/zfs/zfs_vfsops.c

@@ -1152,8 +1152,8 @@ zfs_sb_teardown(zfs_sb_t *zsb, boolean_t unmounting)
 		 */
 		int round = 0;
 		while (zsb->z_nr_znodes > 0) {
-			taskq_wait(dsl_pool_iput_taskq(dmu_objset_pool(
-			    zsb->z_os)));
+			taskq_wait_outstanding(dsl_pool_iput_taskq(
+			    dmu_objset_pool(zsb->z_os)), 0);
 			if (++round > 1 && !unmounting)
 				break;
 		}
@@ -1740,7 +1740,7 @@ zfs_init(void)
 void
 zfs_fini(void)
 {
-	taskq_wait(system_taskq);
+	taskq_wait_outstanding(system_taskq, 0);
 	unregister_filesystem(&zpl_fs_type);
 	zfs_znode_fini();
 	zfsctl_fini();