Re: [PATCH 1/2] common/rc: Enable _format_swapfile to return the swap size

[Zorro Lang <zlang@redhat.com>]

On Tue, Nov 02, 2021 at 04:28:27PM +0100, Carlos Maiolino wrote:
> Once the kernel is free to not map the full swap file during a swapon call,
> it can be useful to know the exact size of the swap area created during
> _format_swapfile().
> 
> To achieve this, it is required to change _require_scratch_swapfile(), to drop
> the _format_swapfile() return value, otherwise, it will also have a return value
> that will end up in tests outputs causing tests to fail.
> 
> Tests using _format_swapfile() that do not require the swap file size do not
> need to be modified, as the return value will be simply ignored.
> 
> Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
> ---
>  common/rc | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/common/rc b/common/rc
> index 7f693d39..fb1f32e0 100644
> --- a/common/rc
> +++ b/common/rc
> @@ -2587,6 +2587,7 @@ _require_odirect()
>  _format_swapfile() {
>  	local fname="$1"
>  	local sz="$2"
> +	local swap_log=""
>  
>  	rm -f "$fname"
>  	touch "$fname"
> @@ -2595,8 +2596,11 @@ _format_swapfile() {
>  	$CHATTR_PROG +C "$fname" > /dev/null 2>&1
>  	_pwrite_byte 0x61 0 "$sz" "$fname" >> $seqres.full
>  	# Ignore permission complaints on filesystems that don't support perms
> -	$MKSWAP_PROG "$fname" 2>&1 >> $seqres.full | \
> -		grep -v "insecure permission"
> +	swap_log=$($MKSWAP_PROG "$fname" 2>&1 | grep -v "insecure permission")
> +	echo $swap_log >> $seqres.full
> +
> +	# return created swap size
> +	echo $swap_log | grep -oP '(?<=size = )\w+'

I saw you've changed generic/643 to suit this change, but there're many cases
call _format_swapfile() [1], now it print something to stdout by default, did
you make sure it won't break other cases' golden image?

Thanks,
Zorro

[1]
$ grep -rsn _format_swapfile tests/
tests/btrfs/173:22:# We can't use _format_swapfile because we don't want chattr +C, and we can't
tests/btrfs/173:34:_format_swapfile "$SCRATCH_MNT/swap" $(($(get_page_size) * 10))
tests/btrfs/177:66:_format_swapfile "$swapfile" $((32 * 1024 * 1024))
tests/btrfs/174:23:_format_swapfile "$swapfile" $(($(get_page_size) * 10))
tests/btrfs/175:21:     _format_swapfile "$SCRATCH_MNT/swap" "$sz"
tests/btrfs/175:50:_format_swapfile "$SCRATCH_MNT/swap" $(($(get_page_size) * 10))
tests/btrfs/176:32:_format_swapfile "$SCRATCH_MNT/swap" $(($(get_page_size) * 10))
tests/btrfs/176:50:_format_swapfile "$SCRATCH_MNT/swap" $(($(get_page_size) * 10))
tests/generic/643:39:_format_swapfile $swapfile 1m >> $seqres.full
tests/generic/357:42:_format_swapfile "$testdir/file1" $((blocks * blksz))
tests/generic/493:30:_format_swapfile "$testdir/file1" $((blocks * blksz))
tests/generic/494:29:_format_swapfile "$testdir/file1" $((blocks * blksz))
tests/generic/356:42:_format_swapfile "$testdir/file1" $((blocks * blksz))
tests/generic/569:34:_format_swapfile $testfile 20m
tests/generic/495:24:# We can't use _format_swapfile because we're using our custom mkswap and
tests/generic/554:33:_format_swapfile $SCRATCH_MNT/swapfile 16m

>  }
>  
>  _swapon_file() {
> @@ -2628,7 +2632,7 @@ _require_scratch_swapfile()
>  	_scratch_mount
>  
>  	# Minimum size for mkswap is 10 pages
> -	_format_swapfile "$SCRATCH_MNT/swap" $(($(get_page_size) * 10))
> +	_format_swapfile "$SCRATCH_MNT/swap" $(($(get_page_size) * 10)) > /dev/null
>  
>  	# ext* has supported all variants of swap files since their
>  	# introduction, so swapon should not fail.
> -- 
> 2.31.1
>