Re: [PATCH] btrfs/zoned: test premature ENOSPC because of reclaim being too slow

[David Disseldorp <ddiss@suse.de>]

Hi Johannes,

On Mon, 22 Jan 2024 02:55:54 -0800, Johannes Thumshirn wrote:

> Add a test writing a file of 60% the drive size on a zoned btrfs and then
> overwriting the file again.
> 
> On fast drives this will cause premature ENOSPC because the reclaim
> process isn't triggered fast enough.
> 
> The kernel patch for this issue is:
>  btrfs: zoned: wake up cleaner sooner if needed
> 
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
> ---
>  tests/btrfs/310     | 54 +++++++++++++++++++++++++++++++++++++++++++++
>  tests/btrfs/310.out |  2 ++
>  2 files changed, 56 insertions(+)
>  create mode 100755 tests/btrfs/310
>  create mode 100644 tests/btrfs/310.out
> 
> diff --git a/tests/btrfs/310 b/tests/btrfs/310
> new file mode 100755
> index 000000000000..6f6f5542f73f
> --- /dev/null
> +++ b/tests/btrfs/310
> @@ -0,0 +1,54 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2024 Western Digital Corporation.  All Rights Reserved.
> +#
> +# FS QA Test 310
> +#
> +# Write a single file with 60% disk size to a zoned btrfs and then overwrite
> +# it again. On kernels without the fix this results in ENOSPC.
> +#
> +# This issue is fixed by the following kernel patch:
> +#    btrfs: zoned: wake up cleaner sooner if needed

To-be-queued fixes are often flagged in the test via:
_fixed_by_kernel_commit XXXXXXXXXXXX \
	"btrfs: zoned: wake up cleaner sooner if needed"

> +
> +. ./common/preamble
> +_begin_fstest auto enospc rw zone
> +
> +# real QA test starts here
> +
> +_supported_fs btrfs

I don't see anything btrfs specific here, aside from the actual bug
being triggered.
Would it make sense to move this to generic, or would that be a waste of
cycles for non-zone envs?

> +_require_scratch
> +_require_zoned_device "$SCRATCH_DEV"
> +
> +devsize=$(cat /sys/block/$(_short_dev $SCRATCH_DEV)/size)
> +devsize=$(expr $devsize \* 512)
> +filesize=$(expr $devsize \* 60 / 100)
> +
> +fio_config=$tmp.fio
> +
> +# Override the default cleanup function.
> +_cleanup()
> +{
> +	rm -f $tmp.*
> +}

nit: looks like there's no need to override the default cleanup.

Test looks fine otherwise.

Cheers, David