tests/xfs/196

#! /bin/bash
# FS QA Test No. 196
#
# This test stresses indirect block reservation for delayed allocation extents.
# XFS reserves extra blocks for deferred allocation of delalloc extents. These
# reserved blocks can be divided among more extents than anticipated if the
# original extent for which the blocks were reserved is split into multiple
# delalloc extents. If this scenario repeats, eventually some extents are left
# without any indirect block reservation whatsoever. This leads to assert
# failures and possibly other problems in XFS.
#
#-----------------------------------------------------------------------
# Copyright (c) 2017 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/punch

# real QA test starts here
rm -f $seqres.full

# Modify as appropriate.
_supported_fs generic
_supported_os Linux
_require_scratch

DROP_WRITES="drop_writes"
# replace "drop_writes" with "fail_writes" for old kernel
if [ -f /sys/fs/xfs/$(_short_dev $TEST_DEV)/fail_writes ];then
	DROP_WRITES="fail_writes"
fi
_require_xfs_sysfs $(_short_dev $TEST_DEV)/${DROP_WRITES}

_scratch_mkfs >/dev/null 2>&1
_scratch_mount

sdev=$(_short_dev $SCRATCH_DEV)
file=$SCRATCH_MNT/file.$seq
bytes=$((64 * 1024))

# create sequential delayed allocation
$XFS_IO_PROG -f -c "pwrite 0 $bytes" $file >> $seqres.full 2>&1

# Enable write drops. All buffered writes are dropped from this point on.
echo 1 > /sys/fs/xfs/$sdev/$DROP_WRITES

# Write every other 4k range to split the larger delalloc extent into many more
# smaller extents. Use pwrite because with write failures enabled, all
# preexisting delalloc blocks in the range of the I/O are tossed without
# discretion. This allows manipulation of the delalloc extent without conversion
# to real blocks (and thus releasing the indirect reservation).
endoff=$((bytes - 4096))
for i in $(seq 0 8192 $endoff); do
	$XFS_IO_PROG -c "pwrite $i 4k" $file >> $seqres.full 2>&1
done

# now pwrite the opposite set to remove remaining delalloc extents
for i in $(seq 4096 8192 $endoff); do
	$XFS_IO_PROG -c "pwrite $i 4k" $file >> $seqres.full 2>&1
done

echo 0 > /sys/fs/xfs/$sdev/$DROP_WRITES

_scratch_cycle_mount
$XFS_IO_PROG -c 'bmap -vp' $file | _filter_bmap

# Now test a buffered write workload with larger extents. Write a 100m extent,
# split it at the 3/4 mark, then write another 100m extent that is contiguous
# with the 1/4 portion of the split extent. Repeat several times. This pattern
# is known to prematurely exhaust indirect reservations and cause warnings and
# assert failures.
rm -f $file
for offset in $(seq 0 100 500); do
	$XFS_IO_PROG -fc "pwrite ${offset}m 100m" $file >> $seqres.full 2>&1

	punchoffset=$((offset + 75))
	echo 1 > /sys/fs/xfs/$sdev/$DROP_WRITES
	$XFS_IO_PROG -c "pwrite ${punchoffset}m 4k" $file >> $seqres.full 2>&1
	echo 0 > /sys/fs/xfs/$sdev/$DROP_WRITES
done

echo "Silence is golden."

status=0
exit