From 7c9abfa7ab0bc88e059800c6a5f8d2c2ebb62588 Mon Sep 17 00:00:00 2001
From: Gary Mills <gary_mills@fastmail.fm>
Date: Tue, 2 Feb 2016 16:23:21 -0800
Subject: [PATCH] Illumos 6537 - Panic on zpool scrub with DEBUG kernel

6537 Panic on zpool scrub with DEBUG kernel
Reviewed by: Steve Gonczi <gonczi@comcast.net>
Reviewed by: Dan McDonald <danmcd@omniti.com>
Reviewed by: Igor Kozhukhov <ikozhukhov@gmail.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Matthew Ahrens <mahrens@delphix.com>

References:
  https://www.illumos.org/issues/6537
  https://github.com/illumos/illumos-gate/commit/8c04a1f

Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>
---
 module/zfs/dsl_scan.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/module/zfs/dsl_scan.c b/module/zfs/dsl_scan.c
index 166d0c1eb..8a5fac25f 100644
--- a/module/zfs/dsl_scan.c
+++ b/module/zfs/dsl_scan.c
@@ -21,6 +21,7 @@
 /*
  * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2011, 2015 by Delphix. All rights reserved.
+ * Copyright 2016 Gary Mills
  */
 
 #include <sys/dsl_scan.h>
@@ -1626,7 +1627,8 @@ dsl_scan_sync(dsl_pool_t *dp, dmu_tx_t *tx)
 	}
 	if (err != 0)
 		return;
-	if (!scn->scn_async_destroying && zfs_free_leak_on_eio &&
+	if (dp->dp_free_dir != NULL && !scn->scn_async_destroying &&
+	    zfs_free_leak_on_eio &&
 	    (dsl_dir_phys(dp->dp_free_dir)->dd_used_bytes != 0 ||
 	    dsl_dir_phys(dp->dp_free_dir)->dd_compressed_bytes != 0 ||
 	    dsl_dir_phys(dp->dp_free_dir)->dd_uncompressed_bytes != 0)) {
@@ -1652,7 +1654,7 @@ dsl_scan_sync(dsl_pool_t *dp, dmu_tx_t *tx)
 		    -dsl_dir_phys(dp->dp_free_dir)->dd_compressed_bytes,
 		    -dsl_dir_phys(dp->dp_free_dir)->dd_uncompressed_bytes, tx);
 	}
-	if (!scn->scn_async_destroying) {
+	if (dp->dp_free_dir != NULL && !scn->scn_async_destroying) {
 		/* finished; verify that space accounting went to zero */
 		ASSERT0(dsl_dir_phys(dp->dp_free_dir)->dd_used_bytes);
 		ASSERT0(dsl_dir_phys(dp->dp_free_dir)->dd_compressed_bytes);
-- 
2.40.0