Re: [PATCH v2] btrfs/255: add test for quota disable in parallel with balance

[Filipe Manana <fdmanana@kernel.org>]

On Tue, Jan 18, 2022 at 02:57:21PM +0900, Shin'ichiro Kawasaki wrote:
> Test quota disable during btrfs balance and confirm it does not cause
> kernel hang. This is a regression test for the problem reported to
> linux-btrfs list [1]. The hang was recreated using the test case and
> memory backed null_blk device with 5GB size as the scratch device.
> 
> [1] https://lore.kernel.org/linux-btrfs/20220115053012.941761-1-shinichiro.kawasaki@wdc.com/
> 
> Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
> ---
> Changes from v1:
> * Put more stress by repeating quota enable/disable and btrfs balance
> * Reflected other comments on the list
> 
>  tests/btrfs/255     | 45 +++++++++++++++++++++++++++++++++++++++++++++
>  tests/btrfs/255.out |  2 ++
>  2 files changed, 47 insertions(+)
>  create mode 100755 tests/btrfs/255
>  create mode 100644 tests/btrfs/255.out
> 
> diff --git a/tests/btrfs/255 b/tests/btrfs/255
> new file mode 100755
> index 00000000..32f00f42
> --- /dev/null
> +++ b/tests/btrfs/255
> @@ -0,0 +1,45 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2022 Western Digital Corporation or its affiliates.
> +#
> +# FS QA Test No. btrfs/255
> +#
> +# Confirm that disabling quota during balance does not hang
> +#
> +. ./common/preamble
> +_begin_fstest auto qgroup balance
> +
> +# real QA test starts here
> +_supported_fs btrfs
> +_require_scratch
> +
> +_scratch_mkfs >> $seqres.full 2>&1
> +_scratch_mount
> +
> +# Fill 40% of the device or 2GB
> +fill_percent=40
> +max_fillsize=$((2 * 1024 * 1024 * 1024))
> +
> +devsize=$(($(_get_device_size $SCRATCH_DEV) * 512))
> +fillsize=$((devsize * fill_percent / 100))
> +((fillsize > max_fillsize)) && fillsize=$max_fillsize
> +
> +fs=$((4096 * 1024))
> +for ((i = 0; i * fs < fillsize; i++)); do
> +	dd if=/dev/zero of=$SCRATCH_MNT/file.$i bs=$fs count=1 \
> +	   >> $seqres.full 2>&1
> +done
> +
> +# Run btrfs balance and quota enable/disable in parallel
> +_btrfs_stress_balance $SCRATCH_MNT >> $seqres.full &
> +balance_pid=$!
> +echo $balance_pid >> $seqres.full
> +for ((i = 0; i < 20; i++)); do
> +	$BTRFS_UTIL_PROG quota enable $SCRATCH_MNT
> +	$BTRFS_UTIL_PROG quota disable $SCRATCH_MNT
> +done
> +kill $balance_pid &> /dev/null

You need to wait for the balance pid to exit before terminating the test,
otherwise the test will fail often when the fstests framework is trying
to unmount the scratch device (with an -EBUSY returned from umount).

And please do like in other tests that use _btrfs_stress_balance():

	kill $balance_pid
	wait
	# wait for the balance operation to finish
	while ps aux | grep "balance start" | grep -qv grep; do
		sleep 1
	done

Like in btrfs/060 for example.

Other than that, it looks fine, thanks.

> +
> +echo "Silence is golden"
> +status=0
> +exit
> diff --git a/tests/btrfs/255.out b/tests/btrfs/255.out
> new file mode 100644
> index 00000000..7eefb828
> --- /dev/null
> +++ b/tests/btrfs/255.out
> @@ -0,0 +1,2 @@
> +QA output created by 255
> +Silence is golden
> -- 
> 2.33.1
>