tests/btrfs/130

#! /bin/bash
# SPDX-License-Identifier: GPL-2.0
# Copyright (c) 2016 Fujitsu. All Rights Reserved.
#
# FS QA Test 130
#
# Check if btrfs send can handle large deduped file, whose file extents
# are all pointing to one extent.
# Such file structure will cause quite large pressure to any operation which
# iterates all backref of one extent.
# And unfortunately, btrfs send is one of these operations, and will cause
# softlock or OOM on systems with small memory(<4G).
#
. ./common/preamble
_begin_fstest auto quick clone send

. ./common/filter
. ./common/reflink

_require_scratch
_require_scratch_reflink

_scratch_mkfs > /dev/null 2>&1
_scratch_mount

nr_extents=$((256 * $LOAD_FACTOR))

# Use 128K blocksize, the default value of both deduperemove or
# inband dedupe
blocksize=$((128 * 1024))
file=$SCRATCH_MNT/foobar

echo LOAD_FACTOR=$LOAD_FACTOR nr_extents=$nr_extents blocksize=$blocksize >> $seqres.full

# create the initial file, whose file extents are all point to one extent
_pwrite_byte 0xcdcdcdcd 0 $blocksize  $file | _filter_xfs_io

for i in $(seq 1 $(($nr_extents - 1))); do
	_reflink_range $file 0 $file $(($i * $blocksize)) $blocksize \
		>> $seqres.full 2>&1
done

# create a RO snapshot, so we can send out the snapshot
_btrfs subvolume snapshot -r $SCRATCH_MNT $SCRATCH_MNT/ro_snap

# send out the subvolume, and it will either:
# 1) OOM since memory is allocated inside a O(n^3) loop
# 2) Softlock since time consuming backref walk is called without scheduling.
# the send destination is not important, just send will cause the problem
echo "# $BTRFS_UTIL_PROG send $SCRATCH_MNT/ro_snap > /dev/null" >> $seqres.full
$BTRFS_UTIL_PROG send $SCRATCH_MNT/ro_snap > /dev/null 2>>$seqres.full

# success, all done
status=0
exit