LTP test df01.sh detected different size of loop device in v5.19

From: Petr Vorel <pvorel@suse.cz>
To: linux-block@vger.kernel.org
Cc: Jens Axboe <axboe@kernel.dk>, Jan Kara <jack@suse.cz>,
	Hannes Reinecke <hare@suse.de>,
	linux-xfs@vger.kernel.org
Subject: LTP test df01.sh detected different size of loop device in v5.19
Date: Fri, 12 Aug 2022 15:20:37 +0200	[thread overview]
Message-ID: <YvZTpQFinpkB06p9@pevik> (raw)

Hi all,

LTP test df01.sh found different size of loop device in v5.19.
Test uses loop device formatted on various file systems, only XFS fails.
It randomly fails during verifying that loop size usage changes:

grep ${TST_DEVICE} output | grep -q "${total}.*${used}" [1]

How to reproduce:
# PATH="/opt/ltp/testcases/bin:$PATH" df01.sh -f xfs # it needs several tries to hit

df saved output:
Filesystem     1024-blocks    Used Available Capacity Mounted on
...
/dev/loop0          256672   16208    240464       7% /tmp/LTP_df01.1kRwoUCCR7/mntpoint
df output:
Filesystem     1024-blocks    Used Available Capacity Mounted on
...
tmpfs               201780       0    201780       0% /run/user/0
/dev/loop0          256672   15160    241512       6% /tmp/LTP_df01.1kRwoUCCR7/mntpoint
=> different size
df01 4 TFAIL: 'df -k -P' failed, not expected.

Also 'df -T -P' fails.

It might be a false positive / bug in the test, but it's at least a changed behavior.
I was able to reproduce it on v5.19 distro kernels (openSUSE, Debian).
I haven't bisected (yet), nor checked Jens' git tree (maybe it has been fixed).

Kind regards,
Petr

[1] https://github.com/linux-test-project/ltp/blob/f42f6f3b4671f447b743afe8612917ba4362b8a6/testcases/commands/df/df01.sh#L103-L110