tests/btrfs/102

#! /bin/bash
# SPDX-License-Identifier: GPL-2.0
# Copyright (C) 2015 SUSE Linux Products GmbH. All Rights Reserved.
#
# FSQA Test No. 102
#
# Regression test for an ENOSPC issue when attempting to write to a file in
# a filesystem without any data block groups allocated.
#
. ./common/preamble
_begin_fstest auto quick metadata enospc balance

. ./common/filter

_require_scratch

_scratch_mkfs >>$seqres.full 2>&1

# Mount our filesystem without space caches enabled so that we do not get any
# space used from the initial data block group that mkfs creates (space caches
# used space from data block groups).
_scratch_mount $(_btrfs_no_v1_cache_opt)

# Need an fs with at least 2Gb to make sure mkfs.btrfs does not create an fs
# using mixed block groups (used both for data and metadata). We really need
# to have dedicated block groups for data to reproduce the issue and mkfs.btrfs
# defaults to mixed block groups only for small filesystems (up to 1Gb).
_require_fs_space $SCRATCH_MNT $((2 * 1024 * 1024))

# Run balance with the purpose of deleting the unused data block group that
# mkfs created. We could also wait for the background kthread to automatically
# delete the unused block group, but we do not have a way to make it run and
# wait for it to complete, so just do a balance instead of some unreliable sleep
_run_btrfs_balance_start -dusage=0 $SCRATCH_MNT >> $seqres.full

# Now unmount the filesystem, mount it again (either with or with space caches
# enabled, it does not matter to trigger the problem) and attempt to create a
# file with some data - this used to fail with ENOSPC because there were no
# data block groups when the filesystem was mounted and the data space info
# object was marked as full when initialized (because it had 0 total bytes),
# which prevented the file write path from attempting to allocate a data block
# group and fail immediately with ENOSPC.
_scratch_cycle_mount
echo "hello world" > $SCRATCH_MNT/foobar

echo "Silence is golden"
status=0
exit