#! /bin/bash
# SPDX-License-Identifier: GPL-2.0
# Copyright (c) 2017 Red Hat, Inc.  All Rights Reserved.
#
# 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.
#
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
. ./common/inject

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

# Modify as appropriate.
_supported_fs generic
_supported_os Linux
_require_scratch
_require_xfs_io_error_injection "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.
_scratch_inject_error "drop_writes" 1

# 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

_scratch_inject_error "drop_writes" 0

_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))
	_scratch_inject_error "drop_writes"
	$XFS_IO_PROG -c "pwrite ${punchoffset}m 4k" $file >> $seqres.full 2>&1
	_scratch_inject_error "drop_writes" 0
done

echo "Silence is golden."

status=0
exit