generic: test writeback error handling on dmerror devices

Ensure that we get an error back on all fds when a block device is
open by multiple writers and writeback fails.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>

tests/generic/442

@@ -0,0 +1,63 @@
+#! /bin/bash
+# FS QA Test No. 442
+#
+# Test writeback error handling when writing to block devices via pagecache.
+# See src/fsync-err.c for details of what test actually does.
+#
+#-----------------------------------------------------------------------
+# Copyright (c) 2017, Jeff Layton <jlayton@redhat.com>
+#
+# 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 -rf $tmp.* $testdir
+    _dmerror_cleanup
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+. ./common/dmerror
+
+# real QA test starts here
+_supported_os Linux
+_require_scratch
+_require_dm_target error
+_require_test_program fsync-err
+_require_test_program dmerror
+
+rm -f $seqres.full
+
+_dmerror_init
+
+$here/src/fsync-err -d $here/src/dmerror $DMERROR_DEV
+
+# success, all done
+_dmerror_load_working_table
+_dmerror_cleanup
+_scratch_mkfs > $seqres.full 2>&1
+status=0
+exit

tests/generic/442.out

@@ -0,0 +1,2 @@
+QA output created by 442
+Test passed!

tests/generic/group

@@ -444,3 +444,4 @@
 439 auto quick punch
 440 auto quick encrypt
 441 auto quick
+442 blockdev