#! /bin/bash
# SPDX-License-Identifier: GPL-2.0
# Copyright (C) 2021 SUSE Linux Products GmbH. All Rights Reserved.
#
# FS QA Test No. 250
#
# Test that if we write to a range of a NOCOW file that has allocated extents
# and there is not enough available free space for allocating new data extents,
# the write succeeds. Test for direct IO and buffered IO writes.
# The patch that fixes the direct IO case has the following subject:
#
# "btrfs: fix ENOSPC failure when attempting direct IO write into NOCOW range"
#
. ./common/preamble
_begin_fstest auto quick enospc

_cleanup()
{
	cd /
	rm -r -f $tmp.*
}

. ./common/filter

_supported_fs btrfs
_require_scratch
_require_chattr C
_require_odirect

# Use a small fixed size filesystem so that it's quick to fill it up.
# Make sure the fs size is > 256M, so that the mixed block groups feature is
# not enabled by _scatch_mkfs_sized(), because we later want to not have more
# space available for allocating data extents but still have enough metadata
# space free for the file writes.
fs_size=$((1024 * 1024 * 1024)) # 1G
_scratch_mkfs_sized $fs_size >>$seqres.full 2>&1
_scratch_mount

# Create our test file with the NOCOW attribute set.
touch $SCRATCH_MNT/foobar
$CHATTR_PROG +C $SCRATCH_MNT/foobar

# Now fill in all unallocated space with data for our test file.
# This will allocate a data block group that will be full and leave no (or a
# very small amount of) unallocated space in the device, so that it will not be
# possible to allocate a new block group later.
echo "Creating test file with initial data..."
$XFS_IO_PROG -c "pwrite -S 0xab -b 1M 0 900M" $SCRATCH_MNT/foobar | _filter_xfs_io

# Now try a direct IO write against file range [0, 10M[.
# This should succeed since this is a NOCOW file and an extent for the range was
# previously allocated.
echo "Trying direct IO write over allocated space..."
$XFS_IO_PROG -d -c "pwrite -S 0xcd -b 10M 0 10M" $SCRATCH_MNT/foobar | _filter_xfs_io

# Now try a buffered IO write against file range [10M, 20M[.
# This should also succeed since this is a NOCOW file and an extent for the range
# was previously allocated.
echo "Trying buffered IO write over allocated space..."
$XFS_IO_PROG -c "pwrite -S 0xef -b 10M 10M 10M" $SCRATCH_MNT/foobar | _filter_xfs_io

# Unmount and mount again the filesystem to clear any data from our file from the
# page cache.
_scratch_cycle_mount

# Now read the file and verify that all the writes we did before were durably
# persisted.
echo "File data after mounting again the filesystem:"
od -A d -t x1 $SCRATCH_MNT/foobar

# success, all done
status=0
exit