tests/generic/037

#! /bin/bash
# FSQA Test No. 037
#
# Verify that replacing a xattr's value is an atomic operation.
# This is motivated by an issue in btrfs where replacing a xattr's value
# wasn't an atomic operation, it consisted of removing the old value and
# then inserting the new value in a btree. This made readers (getxattr
# and listxattrs) not getting neither the old nor the new value during
# a short time window.
#
# The btrfs issue was fixed by the following linux kernel patch:
#
#    Btrfs: make xattr replace operations atomic
#
#-----------------------------------------------------------------------
#
# Copyright (C) 2014 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"
tmp=/tmp/$$
status=1	# failure is the default!
trap "_cleanup; exit \$status" 0 1 2 3 15

_cleanup()
{
	kill $setter_pid
	rm -f $tmp.*
}

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

# real QA test starts here
_supported_fs generic
_supported_os Linux
_require_scratch
_require_attrs

rm -f $seqres.full

xattr_name="user.something"
xattr_value1="foobar"
xattr_value2="rabbit_hole"

set_xattr_loop()
{
	local name=$1
	local cur_val=$xattr_value1
	while true; do
		$SETFATTR_PROG -n $xattr_name -v $cur_val $SCRATCH_MNT/$name
		if [ "$cur_val" == "$xattr_value1" ]; then
			cur_val=$xattr_value2
		else
			cur_val=$xattr_value1
		fi
	done
}

value_filter()
{
	grep "$xattr_name=" | cut -d '=' -f 2 | \
		sed -e "s/$xattr_value1/GOOD/" -e "s/$xattr_value2/GOOD/"
}

_scratch_mkfs >>$seqres.full 2>&1
_scratch_mount

test_file="test_xattr_replace"
touch $SCRATCH_MNT/$test_file
$SETFATTR_PROG -n $xattr_name -v $xattr_value1 $SCRATCH_MNT/$test_file

set_xattr_loop $test_file &
setter_pid=$!

for ((i = 0; i < 1000; i++)); do
	$GETFATTR_PROG --absolute-names -n $xattr_name \
		$SCRATCH_MNT/$test_file | value_filter
done

status=0
exit