xfs: rw remount with unknown ro-compat features

Although ro-compat features cannot be mounted rw, a bug allows an
ro->rw remount transition, and this will corrupt the filesystem if
it contains ro-compat features unknown to the running kernel.

This bug has been fixed on linux kernel (d0a58e8 xfs: disallow rw
remount on fs with unknown ro-compat features), this case is the
regression testcase of that bug.

Signed-off-by: Zorro Lang <zlang@redhat.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>

tests/xfs/270

@@ -0,0 +1,93 @@
+#! /bin/bash
+# FS QA Test 270
+#
+# Today ro-compat features can't be mounted rw, but a bug allows
+# an ro->rw remount transition. This bug has been fixed on linux
+# kernel (d0a58e8 xfs: disallow rw remount on fs with unknown
+# ro-compat features), and this case is the regression testcase.
+#
+#-----------------------------------------------------------------------
+# Copyright (c) 2016 Red Hat, Inc.  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!
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+_cleanup()
+{
+	cd /
+	rm -f $tmp.*
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+
+# remove previous $seqres.full before test
+rm -f $seqres.full
+
+# real QA test starts here
+_supported_fs xfs
+_supported_os Linux
+# skip fs check because superblock contains unknown ro-compat features
+_require_scratch_nocheck
+# Only V5 XFS disallow rw mount/remount with unknown ro-compat features
+_require_scratch_xfs_crc
+
+_scratch_mkfs_xfs >>$seqres.full 2>&1
+
+# set the highest bit of features_ro_compat, use it as an unknown
+# feature bit. If one day this bit become known feature, please
+# change this case.
+$XFS_DB_PROG -x -c "sb 0" -c "write features_ro_compat $((2**31))" $SCRATCH_DEV
+
+# rw mount with unknown ro-compat feature should fail
+echo "rw mount test"
+_scratch_mount 2>>$seqres.full
+if [ $? -eq 0 ]; then
+	_fail "rw mount test failed"
+fi
+
+# But ro mount should succeed
+echo "ro mount test"
+_scratch_mount -o ro
+if [ $? -ne 0 ]; then
+	_fail "ro mount test failed"
+else
+	# no hang/panic is fine
+	$FSSTRESS_PROG -d $SCRATCH_MNT -p 4 -n 400 >>$seqres.full 2>&1
+fi
+
+# remount as rw, kernel should reject it
+echo "rw remount test"
+_scratch_remount rw 2>>$seqres.full
+if [ $? -eq 0 ]; then
+	dmesg | tail -n 15 >> $seqres.full
+	_fail "rw remount test failed"
+fi
+
+_scratch_unmount
+
+# success, all done
+status=0
+exit

tests/xfs/270.out

@@ -0,0 +1,5 @@
+QA output created by 270
+features_ro_compat = 0x80000000
+rw mount test
+ro mount test
+rw remount test

tests/xfs/group

@@ -267,6 +267,7 @@
 267 dump ioctl tape
 268 dump ioctl tape
 269 auto quick ioctl
+270 auto quick mount
 278 repair auto
 279 auto mkfs
 281 dump ioctl auto quick