Re: [PATCH] btrfs: add test case to verify that btrfs won't waste IO/CPU to defrag compressed extents already at their max size

[Ritesh Harjani <riteshh@linux.ibm.com>]

On 22/01/27 01:53PM, Qu Wenruo wrote:
> There is a long existing bug in btrfs defrag code that it will always
> try to defrag compressed extents, even they are already at max capacity.
>
> This will not reduce the number of extents, but only waste IO/CPU.
>
> The kernel fix is titled:
>
>   btrfs: defrag: don't defrag extents which is already at its max capacity
>
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> ---
>  tests/btrfs/257     | 79 +++++++++++++++++++++++++++++++++++++++++++++
>  tests/btrfs/257.out |  2 ++
>  2 files changed, 81 insertions(+)
>  create mode 100755 tests/btrfs/257
>  create mode 100644 tests/btrfs/257.out
>
> diff --git a/tests/btrfs/257 b/tests/btrfs/257
> new file mode 100755
> index 00000000..326687dc
> --- /dev/null
> +++ b/tests/btrfs/257
> @@ -0,0 +1,79 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (C) 2022 SUSE Linux Products GmbH. All Rights Reserved.
> +#
> +# FS QA Test 257
> +#
> +# Make sure btrfs defrag ioctl won't defrag compressed extents which are already
> +# at their max capacity.

Haven't really looked into this fstest. But it is a good practice to add the
commit id and the title here for others to easily refer kernel commit.

-ritesh