apfstests/tests/generic/056

#! /bin/bash
# FS QA Test No. 056
#
# This test is motivated by an fsync issue discovered in btrfs.
# The issue was that we could lose file data, that was previously fsync'ed
# successfully, if we end up adding a hard link to our inode and then persist
# the fsync log later via an fsync of other inode for example.
#
# The btrfs issue was fixed by the following linux kernel patch:
#
#  Btrfs: fix fsync data loss after adding hard link to inode
#
#-----------------------------------------------------------------------
# Copyright (C) 2015 SUSE Linux Products GmbH. All Rights Reserved.
# Author: Filipe Manana <fdmanana@suse.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!

_cleanup()
{
	_cleanup_flakey
	rm -f $tmp.*
}
trap "_cleanup; exit \$status" 0 1 2 3 15

# get standard environment, filters and checks
. ./common/rc
. ./common/filter
. ./common/dmflakey

# real QA test starts here
_supported_fs generic
_supported_os Linux
_need_to_be_root
_require_scratch
_require_dm_flakey
_require_metadata_journaling $SCRATCH_DEV

rm -f $seqres.full

_scratch_mkfs >> $seqres.full 2>&1
_init_flakey
_mount_flakey

# Create one file with data and fsync it.
# This made the btrfs fsync log persist the data and the inode metadata with
# a correct inode->i_size (4096 bytes).
$XFS_IO_PROG -f -c "pwrite -S 0xaa -b 4K 0 4K" -c "fsync" \
	$SCRATCH_MNT/foo | _filter_xfs_io

# Now add one hard link to our file. This made the btrfs code update the fsync
# log, in memory only, with an inode metadata having a size of 0.
ln $SCRATCH_MNT/foo $SCRATCH_MNT/foo_link

# Now force persistence of the fsync log to disk, for example, by fsyncing some
# other file.
touch $SCRATCH_MNT/bar
$XFS_IO_PROG -c "fsync" $SCRATCH_MNT/bar

# Before a power loss or crash, we could read the 4Kb of data from our file as
# expected.
echo "File content before:"
od -t x1 $SCRATCH_MNT/foo

# Simulate a crash/power loss.
_load_flakey_table $FLAKEY_DROP_WRITES
_unmount_flakey

_load_flakey_table $FLAKEY_ALLOW_WRITES
_mount_flakey

# After the fsync log replay, because the fsync log had a value of 0 for our
# inode's i_size, we couldn't read anymore the 4Kb of data that we previously
# wrote and fsync'ed. The size of the file became 0 after the fsync log replay.
echo "File content after:"
od -t x1 $SCRATCH_MNT/foo

status=0
exit