#! /bin/bash
# SPDX-License-Identifier: GPL-2.0
# Copyright (c) 2017 Facebook.  All Rights Reserved.
#
# FS QA Test 138
#
# Test decompression in the middle of large extents. Regression test for Linux
# kernel commit 6e78b3f7a193 ("Btrfs: fix btrfs_decompress_buf2page()").
#
. ./common/preamble
_begin_fstest auto compress

. ./common/filter

_supported_fs btrfs
_require_scratch
_require_btrfs_command property
_require_btrfs_no_nodatacow

algos=($(_btrfs_compression_algos))

_scratch_mkfs >>$seqres.full 2>&1
_scratch_mount
# Need 1GB for the uncompressed file plus <1GB for each compressed file.
_require_fs_space $SCRATCH_MNT $((1024 * 1024 * (1 + ${#algos[@]})))

# Checksum a piece in the middle of the file. This hits the unaligned case that
# caused the original bug.
do_csum()
{
	dd if="$1" bs=4K skip=555 count=100 2>>$seqres.full| md5sum | cut -d ' ' -f 1
}

# Create a large, uncompressed (but compressible) file.
touch "${SCRATCH_MNT}/uncompressed"
$BTRFS_UTIL_PROG property set "${SCRATCH_MNT}/uncompressed" compression ""
_ddt of="${SCRATCH_MNT}/uncompressed" bs=1M count=1K 2>&1 | _filter_dd

csum="$(do_csum "${SCRATCH_MNT}/uncompressed")"

for algo in ${algos[@]}; do
	echo "Testing ${algo}" >> $seqres.full

	# Copy the same data, but with compression enabled.
	touch "${SCRATCH_MNT}/${algo}"
	$BTRFS_UTIL_PROG property set "${SCRATCH_MNT}/${algo}" compression "${algo}"
	dd if="${SCRATCH_MNT}/uncompressed" of="${SCRATCH_MNT}/${algo}" bs=1M 2>&1 | _filter_dd

	# The correct data is likely still cached. Cycle the mount to drop the
	# cache and start fresh.
	_scratch_cycle_mount

	# Check the checksum.
	compressed_csum="$(do_csum "${SCRATCH_MNT}/${algo}")"
	if [ "${compressed_csum}" != "${csum}" ]; then
		echo "Checksum mismatch for ${algo} (expected ${csum}, got ${compressed_csum})"
	fi
done

echo "Silence is golden"

status=0
exit