btrfs: make a btrfs version of writeback error reporting test

For btrfs, we can test how it reports data writeback errors on fsync by
implementing a suggestion from Chris Mason:

Build a filesystem with 2 devices that stripes the data across
both devices, but mirrors metadata across both. Then, make one
of the devices fail and test what it does.

[eguan: add comments about creating btrfs with "-d raid0 -m raid1"]

Cc: Chris Mason <clm@fb.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>

tests/btrfs/146

@@ -0,0 +1,97 @@
+#! /bin/bash
+# FS QA Test No. 146
+#
+# Open a file several times, write to it, fsync on all fds and make sure that
+# they all return 0. Change the device to start throwing errors. Write again
+# on all fds and fsync on all fds. Ensure that we get errors on all of them.
+# Then fsync on all one last time and verify that all return 0.
+#
+#-----------------------------------------------------------------------
+# 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.* $testdir
+    _dmerror_cleanup
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+. ./common/dmerror
+
+# real QA test starts here
+_supported_os Linux
+_supported_fs btrfs
+_require_dm_target error
+_require_test_program fsync-err
+_require_test_program dmerror
+
+# bring up dmerror device
+_scratch_unmount
+_dmerror_init
+
+# Replace first device with error-test device
+old_SCRATCH_DEV=$SCRATCH_DEV
+SCRATCH_DEV_POOL=`echo $SCRATCH_DEV_POOL | perl -pe "s#$SCRATCH_DEV#$DMERROR_DEV#"`
+SCRATCH_DEV=$DMERROR_DEV
+
+_require_scratch
+_require_scratch_dev_pool
+
+rm -f $seqres.full
+
+echo "Format and mount"
+
+# Build a filesystem with 2 devices that stripes the data across
+# both devices, but mirrors metadata across both. Then, make one
+# of the devices fail and test what it does.
+_scratch_pool_mkfs "-d raid0 -m raid1" > $seqres.full 2>&1
+_scratch_mount
+
+# How much do we need to write? We need to hit all of the stripes. btrfs uses
+# a fixed 64k stripesize, so write enough to hit each one
+number_of_devices=`echo $SCRATCH_DEV_POOL | wc -w`
+write_kb=$(($number_of_devices * 64))
+_require_fs_space $SCRATCH_MNT $write_kb
+
+testfile=$SCRATCH_MNT/fsync-err-test
+
+SCRATCH_DEV=$old_SCRATCH_DEV
+$here/src/fsync-err -b $(($write_kb * 1024)) -d $here/src/dmerror $testfile
+
+# success, all done
+_dmerror_load_working_table
+
+# fs may be corrupt after this -- attempt to repair it
+_repair_scratch_fs >> $seqres.full
+
+# remove dmerror device
+_dmerror_cleanup
+
+status=0
+exit

tests/btrfs/146.out

@@ -0,0 +1,3 @@
+QA output created by 146
+Format and mount
+Test passed!

tests/btrfs/group

@@ -148,3 +148,4 @@
 143 auto quick
 144 auto quick send
 145 auto quick send
+146 auto quick