btrfs: add regression test for remount with thread_pool resized

Regression test for a btrfs issue of resizing 'thread_pool' when
remount the fs.

This regression was introduced by the following linux kernel commit:
    btrfs: Added btrfs_workqueue_struct implemented ordered
    execution based on kernel workqueue
    08a9ff3264181986d1d692a4e6fce3669700c9f8
And it was fixed by the following linux kernel commit:
    btrfs: fix crash in remount(thread_pool=) case
    800ee2247f483b6d05ed47ef3bbc90b56451746c

Signed-off-by: Xing Gu <gux.fnst@cn.fujitsu.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

common/filter

@@ -137,6 +137,10 @@ _filter_mkfs()
     case $FSTYP in
     xfs)
 	;;
+	btrfs)
+	sed -e "/Performing full device TRIM/d" \
+		-e "/Turning ON incompat feature/d"
+	return ;;
     *)
 	cat - >/dev/null
 	perl -e 'print STDERR "dbsize=4096\nisize=256\n"'

tests/btrfs/082

@@ -0,0 +1,65 @@
+#!/bin/bash
+# FS QA Test No. btrfs/082
+#
+# Regression test for a btrfs issue of resizing 'thread_pool' when
+# remount the fs.
+#
+# This regression was introduced by the following linux kernel commit:
+#     btrfs: Added btrfs_workqueue_struct implemented ordered
+#     execution based on kernel workqueue
+#     08a9ff3264181986d1d692a4e6fce3669700c9f8
+# And it was fixed by the following linux kernel commit:
+#     btrfs: fix crash in remount(thread_pool=) case
+#     800ee2247f483b6d05ed47ef3bbc90b56451746c
+#
+#-----------------------------------------------------------------------
+# Copyright (c) 2015 Fujitsu.  All Rights Reserved.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it would be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write the Free Software Foundation,
+# Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+#
+#-----------------------------------------------------------------------
+#
+
+seq=`basename $0`
+seqres=$RESULT_DIR/$seq
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+status=1	# failure is the default!
+
+_cleanup()
+{
+    rm -f $tmp.*
+}
+
+trap "_cleanup ; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+
+# real QA test starts here
+_supported_fs btrfs
+_supported_os Linux
+_require_scratch
+
+_scratch_mkfs |& _filter_mkfs
+
+_scratch_mount "-o thread_pool=6"
+_scratch_mount "-o remount,thread_pool=10"
+
+echo "Silence is golden"
+status=0
+exit

tests/btrfs/082.out

@@ -0,0 +1,2 @@
+QA output created by 082
+Silence is golden

tests/btrfs/group

@@ -84,3 +84,4 @@
 079 auto rw metadata
 080 auto snapshot
 081 auto quick clone
+082 auto quick remount