linux-kernel - Re: [PATCH] generic/365: Fix false failure when mapping ends with free space

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Message-ID: <20250825152925.tcbbn5rxbjpk4ts7@dell-per750-06-vm-08.rhts.eng.pek2.redhat.com>
Date: Mon, 25 Aug 2025 23:29:25 +0800
From: Zorro Lang <zlang@...hat.com>
To: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
Cc: fstests@...r.kernel.org, Ritesh Harjani <ritesh.list@...il.com>,
	djwong@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] generic/365: Fix false failure when mapping ends with
 free space

On Tue, Aug 05, 2025 at 02:55:56PM +0530, Ojaswin Mujoo wrote:
> If we have a small FS where the first free space mapping is also the
> last mapping of the FS, then the following sub-test fails:
> 
>   echo "test whatever came after freesp"
>   $XFS_IO_PROG -c "fsmap -d $((freesp_end + 2)) $((freesp_end + 3))" $SCRATCH_MNT
> 
> since there is nothing after the freespace. Fix this by punching a 1M
> hole in a 3M file to ensure that the first free space is always
> surrounded by allocated blocks.
> 
> Signed-off-by: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
> ---
>  tests/generic/365 | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/tests/generic/365 b/tests/generic/365
> index 36cb2530..bbadae71 100755
> --- a/tests/generic/365
> +++ b/tests/generic/365
> @@ -32,6 +32,10 @@ if ((blksz < 2048)); then
>  	_notrun "test requires at least 4 bblocks per fsblock"
>  fi
>  
> +# This makes sure there is free space surrounded by allocated blocks, which
> +# is needed for some sub tests.
> +$XFS_IO_PROG -fc 'falloc 0 3M' -c 'fpunch 1M 1M' -c 'fsync' $SCRATCH_MNT/f

If you add "falloc" and "fpunch" operations, you need to:

_require_xfs_io_command "falloc"
_require_xfs_io_command "fpunch"

Due to not all fileystems support these two fs operations.

BTW, I'm wondering how small (and what kind of) the fs you use, cause there's only
one unused region, even this's a clean fs, there're some still many different
metadatas. I even tried a 100M ext2 fs (which doesn't has log space), there're
many free space regions. So I'm curious, how can you hit this issue? And if the
SCRATCH_DEV is too small (e.g. 10M), do we really need to test with that fs size:)

Thanks,
Zorro

> +
>  $XFS_IO_PROG -c 'fsmap' $SCRATCH_MNT >> $seqres.full
>  
>  find_freesp() {
> -- 
> 2.49.0
>