Fix issues found with zfs diff

Two deadlocks / ASSERT failures were introduced in a2c2ed1b which
would occur whenever arc_buf_fill() failed to decrypt a block of
data. This occurred because the call to arc_buf_destroy() which
was responsible for cleaning up the newly created buffer would
attempt to take out the hdr lock that it was already holding. This
was resolved by calling the underlying functions directly without
retaking the lock.

In addition, the dmu_diff() code did not properly ensure that keys
were loaded and mapped before begining dataset traversal. It turns
out that this code does not need to look at any encrypted values,
so the code was altered to perform raw IO only.

Reviewed by: Matthew Ahrens <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Tom Caputi <[email protected]>
Closes #7354 
Closes #7456 

3 files changed, 55 insertions, 1 deletions

diff --git a/tests/runfiles/linux.run b/tests/runfiles/linux.run
index 6dc4df96c..62dfcf44e 100644
--- a/tests/runfiles/linux.run
+++ b/tests/runfiles/linux.run
@@ -150,7 +150,7 @@ tags = ['functional', 'cli_root', 'zfs_destroy']
 
 [tests/functional/cli_root/zfs_diff]
 tests = ['zfs_diff_changes', 'zfs_diff_cliargs', 'zfs_diff_timestamp',
-    'zfs_diff_types']
+    'zfs_diff_types', 'zfs_diff_encrypted']
 tags = ['functional', 'cli_root', 'zfs_diff']
 
 [tests/functional/cli_root/zfs_get]
diff --git a/tests/zfs-tests/tests/functional/cli_root/zfs_diff/Makefile.am b/tests/zfs-tests/tests/functional/cli_root/zfs_diff/Makefile.am
index afb45371a..db90e0585 100644
--- a/tests/zfs-tests/tests/functional/cli_root/zfs_diff/Makefile.am
+++ b/tests/zfs-tests/tests/functional/cli_root/zfs_diff/Makefile.am
@@ -7,6 +7,7 @@ dist_pkgdata_SCRIPTS = \
 	setup.ksh \
 	zfs_diff_changes.ksh \
 	zfs_diff_cliargs.ksh \
+	zfs_diff_encrypted.ksh \
 	zfs_diff_timestamp.ksh \
 	zfs_diff_types.ksh
 
diff --git a/tests/zfs-tests/tests/functional/cli_root/zfs_diff/zfs_diff_encrypted.ksh b/tests/zfs-tests/tests/functional/cli_root/zfs_diff/zfs_diff_encrypted.ksh
new file mode 100755
index 000000000..471e9ca68
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/cli_root/zfs_diff/zfs_diff_encrypted.ksh
@@ -0,0 +1,53 @@
+#!/bin/ksh -p
+#
+# This file and its contents are supplied under the terms of the
+# Common Development and Distribution License ("CDDL"), version 1.0.
+# You may only use this file in accordance with the terms of version
+# 1.0 of the CDDL.
+#
+# A full copy of the text of the CDDL should have accompanied this
+# source.  A copy of the CDDL is also available via the Internet at
+# http://www.illumos.org/license/CDDL.
+#
+
+#
+# Copyright 2018, Datto Inc.
+#
+
+. $STF_SUITE/include/libtest.shlib
+
+#
+# DESCRIPTION:
+# 'zfs diff' should work with encrypted datasets
+#
+# STRATEGY:
+# 1. Create an encrypted dataset
+# 2. Create two snapshots of the dataset
+# 3. Perform 'zfs diff -Ft' and verify no errors occur
+#
+
+verify_runnable "both"
+
+function cleanup
+{
+	datasetexists $TESTPOOL/$TESTFS1 && \
+		log_must zfs destroy -r $TESTPOOL/$TESTFS1
+}
+
+log_assert "'zfs diff' should work with encrypted datasets"
+log_onexit cleanup
+
+# 1. Create an encrypted dataset
+log_must eval "echo 'password' | zfs create -o encryption=on \
+	-o keyformat=passphrase $TESTPOOL/$TESTFS1"
+MNTPOINT="$(get_prop mountpoint $TESTPOOL/$TESTFS1)"
+
+# 2. Create two snapshots of the dataset
+log_must zfs snapshot $TESTPOOL/$TESTFS1@snap1
+log_must touch "$MNTPOINT/file"
+log_must zfs snapshot $TESTPOOL/$TESTFS1@snap2
+
+# 3. Perform 'zfs diff' and verify no errors occur
+log_must zfs diff -Ft $TESTPOOL/$TESTFS1@snap1 $TESTPOOL/$TESTFS1@snap2
+
+log_pass "'zfs diff' works with encrypted datasets"