Re: [PATCH v2] common/rc: Modify _require_batched_discard to improve test coverage

[Zorro Lang]

On Mon, May 16, 2022 at 12:09:51PM +0530, Ojaswin Mujoo wrote:
> A recent ext4 patch discussed [1] that some devices (eg LVMs) can
> have a discard granularity as big as 42MB which makes it larger
> than the group size of ext4 FS with 1k BS.  This causes the FITRIM
> IOCTL to fail.
> 
> This case was not correctly handled by this test since
> "_require_batched_discard" incorrectly interpreted the FITRIM
> failure as SCRATCH_DEV not supporting the IOCTL. This caused the test
> to report "not run" instead of "failed" in case of large discard granularity.
> 
> Fix "_require_batched_discard" to use a more accurate method
> to determine if discard is supported.
> 
> [1] commit 173b6e383d2
>     ext4: avoid trim error on fs with small groups
> 
> Signed-off-by: Ojaswin Mujoo <ojaswin@xxxxxxxxxxxxx>
> Reviewed-by: Ritesh Harjani <riteshh@xxxxxxxxxxxxx>
> ---
> 
> Changes since v1 [1] 
> 
> *  Changed $RET to a local variable
> *  Fixed the grep command 
> 
> [1]
> https://lore.kernel.org/all/20220401055713.634842-1-ojaswin@xxxxxxxxxxxxx/
> 
>  common/rc | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/common/rc b/common/rc
> index e2d3d72a..f366e409 100644
> --- a/common/rc
> +++ b/common/rc
> @@ -3858,7 +3858,13 @@ _require_batched_discard()
>  		exit 1
>  	fi
>  	_require_fstrim
> -	$FSTRIM_PROG $1 > /dev/null 2>&1 || _notrun "FITRIM not supported on $1"
> +
> +	grep -q "not supported" <($FSTRIM_PROG $1 2>&1)
> +	local ret=$?
> +	if [ "$ret" = "0" ]

Oh I forgot to ask why we need to add a variable (ret), to record the return
value at here. Why can't use "$?" directly? e.g.

  grep -q "not supported" <($FSTRIM_PROG $1 2>&1)
  if [ $? -eq 0 ]

Others look good to me.

Thanks,
Zorro

> +	then
> +		_notrun "FITRIM not supported on $1"
> +	fi
>  }
>  
>  _require_dumpe2fs()
> -- 
> 2.27.0
>