#! /bin/bash
# SPDX-License-Identifier: GPL-2.0
# Copyright (C) 2018 SUSE Linux Products GmbH. All Rights Reserved.
#
# FS QA Test No. 170
#
# Test that if we write into an unwritten extent of a file when there is no
# more space left to allocate in the filesystem and then snapshot the file's
# subvolume, after a clean shutdown the data was not lost.
#
. ./common/preamble
_begin_fstest auto quick snapshot prealloc

# Import common functions.
. ./common/filter

# real QA test starts here
_supported_fs btrfs
_require_scratch
_require_xfs_io_command "falloc" "-k"

# Use a fixed size filesystem so that we can precisely fill the data block group
# mkfs.btrfs creates and allocate all unused space for a new data block group.
# It's important to not use the mixed block groups feature as well because we
# later want to not have more space available for allocating data extents but
# still have enough metadata space free for creating the snapshot.
fs_size=$((2 * 1024 * 1024 * 1024)) # 2Gb
_scratch_mkfs_sized $fs_size >>$seqres.full 2>&1

# Mount without space cache so that we can precisely fill all data space and
# unallocated space later (space cache v1 uses data block groups).
_scratch_mount $(_btrfs_no_v1_cache_opt)

# Create our test file and allocate 1826.25Mb of space for it.
# This will exhaust the existing data block group and all unallocated space on
# this small fileystem (2Gb).
$XFS_IO_PROG -f -c "falloc -k 0 1914961920" $SCRATCH_MNT/foobar

# Write some data to the file and check its digest. This write will result in a
# NOCOW write because there's no more space available to allocate and the file
# has preallocated (unwritten) extents.
$XFS_IO_PROG -c "pwrite -S 0xea -b 128K 0 128K" $SCRATCH_MNT/foobar | _filter_xfs_io

echo "File digest after write:"
md5sum $SCRATCH_MNT/foobar | _filter_scratch

# Create a snapshot of the subvolume where our file is.
$BTRFS_UTIL_PROG subvolume snapshot -r $SCRATCH_MNT $SCRATCH_MNT/snap 2>&1 \
	| _filter_scratch

# Cleanly unmount the filesystem.
_scratch_unmount

# Mount the filesystem again and verify the file has the same data it had before
# we unmounted the filesystem (same digest).
_scratch_mount
echo "File digest after mounting the filesystem again:"
md5sum $SCRATCH_MNT/foobar | _filter_scratch

status=0
exit