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From: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>
To: Eryu Guan <guan@eryu.me>
Cc: Dave Chinner <david@fromorbit.com>,
	"fstests@vger.kernel.org" <fstests@vger.kernel.org>,
	Naohiro Aota <Naohiro.Aota@wdc.com>,
	Johannes Thumshirn <Johannes.Thumshirn@wdc.com>,
	Damien Le Moal <Damien.LeMoal@wdc.com>
Subject: Re: [PATCH v2 3/3] common/rc: Check call order of _require_dm_target and _require_scratch*
Date: Sun, 12 Sep 2021 23:28:13 +0000	[thread overview]
Message-ID: <20210912232813.b5rajxu4ggywn2fh@shindev> (raw)
In-Reply-To: <YT3FmvvytzCvWllt@desktop>

On Sep 12, 2021 / 17:17, Eryu Guan wrote:
> On Fri, Sep 10, 2021 at 06:34:05AM +0000, Shinichiro Kawasaki wrote:
> > On Sep 10, 2021 / 10:48, Dave Chinner wrote:
> > > On Wed, Sep 08, 2021 at 05:37:15PM +0900, Shin'ichiro Kawasaki wrote:
> > > > When SCRATCH_DEV is not set and the test case does not call
> > > > _require_scratch* before _require_dm_target, _require_block_device
> > > > called from _require_dm_target fails to evaluate SCRATCH_DEV and
> > > > results in the test case failure. This failure reason is not described
> > > > in the error message and it takes some time to catch.
> > > 
> > > You should quote the actual failure message here so we have some
> > > idea of whether the message that was emitted was appropriate or not
> > > without having to go know how the test failed...
> > 
> > Sorry about the lack of the infomration. As you found below, the meesage was
> > "Usage: _require_block_device <dev>".
> > 
> > > 
> > > > To catch the failure reason easier, check SCRATCH_DEV in
> > > > _require_dm_target. If SCRATCH_DEV is not set, fail the test case
> > > > and print message which requests to fix call order of _require_scratch*
> > > > and _require_dm_target. This improvement follows what _scratch_shutdown
> > > > does for _require_scratch_shutdown.
> > > 
> > > Also, you don't need to describe the change in the commit message -
> > > the patch does that. The first paragraph is all that is needed here
> > > as it describes why you want to make the change.
> > 
> > I see. I will write "why" in the commit message, not "what". (In the past, I
> > was advised to write "what" the patch does, but I think this guide is valid
> > only when the change is complicated).
> > 
> > > 
> > > > Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
> > > > ---
> > > >  common/rc | 3 +++
> > > >  1 file changed, 3 insertions(+)
> > > > 
> > > > diff --git a/common/rc b/common/rc
> > > > index dda5da06..cbec8aaa 100644
> > > > --- a/common/rc
> > > > +++ b/common/rc
> > > > @@ -1971,6 +1971,9 @@ _require_dm_target()
> > > >  
> > > >  	# require SCRATCH_DEV to be a valid block device with sane BLKFLSBUF
> > > >  	# behaviour
> > > > +	if [ -z "$SCRATCH_DEV" ]; then
> > > > +		_fail "_require_dm_target: call _require_scratch* first in test"
> > > > +	fi
> > > >  	_require_block_device $SCRATCH_DEV
> > > >  	_require_sane_bdev_flush $SCRATCH_DEV
> > > >  	_require_command "$DMSETUP_PROG" dmsetup
> > > 
> > > That's a notrun case, not a fail.
> > > 
> > > Also, we report the error that has occurred, not how to resolve the
> > > problem. That's because we might change behaviour in future and now
> > > the error message tells people to do something that is
> > > wrong/non-existent. As such, I think the premise this change is based
> > > on is not really valid - people running fstests are assumed to have
> > > a level of knowledge sufficient to trace a failing test and
> > > determine what went wrong from the error reported. i.e. the error
> > > message should state what the problem was, not describe a potential
> > > solution.
> > 
> > Thank you for the comment. These are the points I missed. At least I was
> > able to catch the cause, so the improvement I suggested is not a big
> > improvement.
> > 
> > > 
> > > Also, this is not the place to check if SCRATCH_DEV is set. The
> > > check for a NULL device should be in _require_block_device(). Oh,
> > > wait, it already is:
> > > 
> > > _require_block_device()
> > > {
> > > 	if [ -z "$1" ]; then
> > > 		echo "Usage: _require_block_device <dev>" 1>&2
> > > 		exit 1
> > > 	fi
> > > ....
> > > }
> > > 
> > > And that's the error message the test emitted that you didn't
> > > understand, right?
> > 
> > Right :)
> > 
> > > 
> > > If so, the change here should really be to _require_block_device().
> > > i.e.
> > > 
> > > 	if [ -z "$1" ]; then
> > > 		_notrun "test requires a block device to be specified"
> > > 	fi
> > > 
> > > A quick scan shows a bunch of similar _requires checks that do
> > > similar things with poor error messages and 'exit 1' (e.g.
> > > _require_local_device()). _requires rules should call _notrun if the
> > > test should not run because of incorrect setup, not 'exit 1'.
> > 
> > Thank you for your thoughts. I walked through _require_* bash functions in
> > common/, and listed 20 functions below, which call 'exit 1', _fail, or
> > 'return 1' for its argument check failure:
> > 
> > --- list start ---
> > 
> > common/rc
> > 
> >   _require_scratch_size
> >   _require_scratch_size_nocheck
> >   _require_command *
> >   _require_block_device *
> >   _require_local_device *
> >   _require_zoned_device *
> >   _require_non_zoned_device *
> >   _require_scratch_ext4_feature
> >   _require_xfs_io_command
> >   _require_fio
> >   _require_batched_discard *
> >   _require_chattr
> >   _require_fs_sysfs
> >   _require_scratch_feature
> > 
> > common/btrfs
> > 
> >   _require_btrfs_mkfs_feature
> >   _require_btrfs_fs_feature
> > 
> > common/xfs
> > 
> >   _require_xfs_db_command
> >   _require_xfs_spaceman_command
> > 
> > common/encrypt
> > 
> >   _require_encryption_policy_support (checks arguments passed from _require_scratch_encryption)
> > 
> > common/rnameat2
> > 
> >   _require_renameat2
> > 
> > --- list end ---
> > 
> > Many of the functions above check arguments not for incorrect setup, but for
> > call in test cases with invalid arguments. 6 functions of them with * in the
> > list check arguments for the incorrect setups, such as DEBUGFS_PROG,
> > SCRATCH_DEV or SCRATCH_MNT. So I suggest to modify these functions to improve
> > error messages and call "_notrun". What do you think about this?
> 
> IMO the _fail calls in above _require* rules are indicating function
> usage errors, which are bugs in the test code. While _notrun indicates a
> required condition is not met for this test.

I see. I think the _require* rules with "exit 1" also indicates the usage errors
and the bugs. As Dave pointed out, it is assumed the fstests users have enough
skill to identify the bug, then this improvement I suggested don't have much
value. I withdraw this suggestion. Dave and Eryu, thank you for the comments.

> 
> Thanks,
> Eryu
> 
> P.S. I've applied the first two patches, thanks for the fix!

Thanks!

-- 
Best Regards,
Shin'ichiro Kawasaki

      reply	other threads:[~2021-09-12 23:28 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-08  8:37 [PATCH v2 0/3] fstests: Fix order of _require_scratch* and _require_dm_target Shin'ichiro Kawasaki
2021-09-08  8:37 ` [PATCH v2 1/3] generic/{628,629}: " Shin'ichiro Kawasaki
2021-09-08 17:04   ` Johannes Thumshirn
2021-09-08  8:37 ` [PATCH v2 2/3] btrfs/146: Add _require_scratch_dev_pool before _require_dm_target Shin'ichiro Kawasaki
2021-09-08 17:05   ` Johannes Thumshirn
2021-09-12  9:30   ` Eryu Guan
2021-09-08  8:37 ` [PATCH v2 3/3] common/rc: Check call order of _require_dm_target and _require_scratch* Shin'ichiro Kawasaki
2021-09-10  0:48   ` Dave Chinner
2021-09-10  6:34     ` Shinichiro Kawasaki
2021-09-12  9:17       ` Eryu Guan
2021-09-12 23:28         ` Shinichiro Kawasaki [this message]

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