OpenZFS 7503 - zfs-test should tail ::zfs_dbgmsg on test failure

Authored by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed by: John Kennedy <john.kennedy@delphix.com>
Reviewed by: Matt Ahrens <mahrens@delphix.com>
Approved by: Gordon Ross <gordon.w.ross@gmail.com>
Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>

Porting Notes:
- Enable internal log for DEBUG builds and in zfs-tests.sh.
- callbacks/zfs_dbgmsg.ksh - Dump interal log via kstat.
- callbacks/zfs_dmesg.ksh - Dump dmesg log.
- default.cfg - 'Test Suite Specific Commands' dropped.

OpenZFS-issue: https://www.illumos.org/issues/7503
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/55a1300
Closes #6002

tests/zfs-tests/Makefile.am

@@ -1 +1 @@
-SUBDIRS = cmd include tests
+SUBDIRS = cmd include tests callbacks

tests/zfs-tests/callbacks/Makefile.am

@@ -0,0 +1,4 @@
+pkgdatadir = $(datadir)/@PACKAGE@/zfs-tests/callbacks
+dist_pkgdata_SCRIPTS = \
+	zfs_dbgmsg.ksh \
+	zfs_dmesg.ksh

tests/zfs-tests/callbacks/zfs_dbgmsg.ksh

@@ -0,0 +1,29 @@
+#!/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 (c) 2016 by Delphix. All rights reserved.
+#
+
+# $1: number of lines to output (default: 200)
+typeset lines=${1:-200}
+
+echo "================================================================="
+echo " Tailing last $lines lines of zfs_dbgmsg log"
+echo "================================================================="
+
+sudo tail -n $lines /proc/spl/kstat/zfs/dbgmsg
+
+echo "================================================================="
+echo " End of zfs_dbgmsg log"
+echo "================================================================="

tests/zfs-tests/callbacks/zfs_dmesg.ksh

@@ -0,0 +1,30 @@
+#!/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 (c) 2016 by Delphix. All rights reserved.
+# Copyright (c) 2017 Lawrence Livermore National Security, LLC.
+#
+
+# $1: number of lines to output (default: 200)
+typeset lines=${1:-200}
+
+echo "================================================================="
+echo " Tailing last $lines lines of dmesg log"
+echo "================================================================="
+
+sudo dmesg | tail -n $lines
+
+echo "================================================================="
+echo " End of dmesg log"
+echo "================================================================="