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

From: Eric Sandeen <sandeen@sandeen.net>
To: Petr Vorel <pvorel@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>,
	linux-block@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
	Jan Kara <jack@suse.cz>, Hannes Reinecke <hare@suse.de>,
	linux-xfs@vger.kernel.org, ltp@lists.linux.it
Subject: Re: LTP test df01.sh detected different size of loop device in v5.19
Date: Thu, 18 Aug 2022 11:05:33 -0500	[thread overview]
Message-ID: <f03c6929-9a14-dd58-3726-dd2c231d0981@sandeen.net> (raw)
In-Reply-To: <Yv5Z7eu5RGnutMly@pevik>

On 8/18/22 10:25 AM, Petr Vorel wrote:
> Hi Eric, all,
> 

...

> 
>> IOWS, I think the test expects that free space is reflected in statfs numbers
>> immediately after a file is removed, and that's no longer the case here. They
>> change in between the df check and the statfs check.
> 
>> (The test isn't just checking that the values are correct, it is checking that
>> the values are /immediately/ correct.)
> 
>> Putting a "sleep 1" after the "rm -f" in the test seems to fix it; IIRC
>> the max time to wait for inodegc is 1s. This does slow the test down a bit.
> 
> Sure, it looks like we can sleep just 50ms on my hw (although better might be to
> poll for the result [1]), I just wanted to make sure there is no bug/regression
> before hiding it with sleep.
> 
> Thanks for your input!
> 
> Kind regards,
> Petr
> 
> [1] https://people.kernel.org/metan/why-sleep-is-almost-never-acceptable-in-tests
> 
>> -Eric
> 
> +++ testcases/commands/df/df01.sh
> @@ -63,6 +63,10 @@ df_test()
>  		tst_res TFAIL "'$cmd' failed."
>  	fi
>  
> +	if [ "$DF_FS_TYPE" = xfs ]; then
> +		tst_sleep 50ms
> +	fi
> +

Probably worth at least a comment as to why ...

Dave / Darrick / Brian - I'm not sure how long it might take to finish inodegc?
A too-short sleep will let the flakiness remain ...

-Eric

>  	ROD_SILENT rm -rf mntpoint/testimg
>  
>  	# flush file system buffers, then we can get the actual sizes.
> 