Re: [PATCH] generic/520: use fsync instead of sync during clean_dir

[Yang Xu <xuyang2018.jy@cn.fujitsu.com>]

on 2019/12/18 6:36, Darrick J. Wong wrote:
> On Mon, Dec 16, 2019 at 02:24:56PM +0800, Yang Xu wrote:
>>
>>
>> on 2019/12/14 4:42, Darrick J. Wong wrote:
>>> On Fri, Dec 13, 2019 at 01:45:41PM +0800, Yang Xu wrote:
>>>> When I test this case on xfs, it may fail as below:
>>>> --------------------------------------------
>>>>    === link SCRATCH_MNT/A/foo SCRATCH_MNT/bar  with fsync SCRATCH_MNT/A ===
>>>> +umount: /mnt/xfstests/scratch: target is busy.
>>>> +        (In some cases useful info about processes that use
>>>> +         the device is found by lsof(8) or fuser(1))
>>>> ---------------------------------------------
>>>>
>>>> I think we don't need to sync all fs and fsync SCRATCH_MNT is enough.
>>>>
>>>> Signed-off-by: Yang Xu <xuyang2018.jy@cn.fujitsu.com>
>>>> ---
>>>>    tests/generic/520 | 2 +-
>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/tests/generic/520 b/tests/generic/520
>>>> index 167d7077..a16467ca 100755
>>>> --- a/tests/generic/520
>>>> +++ b/tests/generic/520
>>>> @@ -58,7 +58,7 @@ clean_dir()
>>>>    {
>>>>    	_mount_flakey
>>>>    	rm -rf $(find $SCRATCH_MNT/* | grep -v "lost+found")
>>>> -	sync
>>>> +	$XFS_IO_PROG -c "fsync" $SCRATCH_MNT
>>>
>>> But that only has to force the scratch mount directory to disk.
>>>
>>> Assuming the test authors really meant "write all of the scratch fs'
>>> dirty data/metadata to disk", I think you want:
>>>
>>>    $XFS_IO_PROG -c syncfs $SCRATCH_MNT
>>>
>>> here?
>> My xfsprogs version doesn't support syncfs command. Or, we can use fsync to
>> make four files(foo bar A/foo A/bar) write to disk?
> 
> Hmm, 'sync -f $SCRATCH_MNT' then?
Both syncfs and sync -f are all useful when I test on 
4.18.0-147.el8.x86_64. But on old system (3.10.0-1101.el7.x86_64
), sync command doesn't support -f option.  Or, I think we should use a 
generic way to avoid busy error. IMHO, it has two ways(mkfs and fsync), 
but mkfs will add more test time. What do you think about it?
> 
>>> Also, why did umount spit out 'target is busy' here?  clean_dir() erases
>>> the scratch fs between tests, there shouldn't be anything flakey about
>>> that.
>> I try to find the cause of this but fail. I debug it but no useful
>> output(using  _unmount_flakey  || fuser -uvm $SCRATCH_MNT ), failed as
>> below:
>> umount: /mnt/xfstests/scratch: target is busy.
>>          (In some cases useful info about processes that use
>>           the device is found by lsof(8) or fuser(1))
>>                       USER        PID ACCESS COMMAND
>> /mnt/xfstests/scratch:
>>                       root     kernel mount (root)/mnt/xfstests/scratch
>>
>> ps: My test machine only excutes this cases and doesn't do other  things.
> 
> Does a second umount attempt succeed after the fuser fails to find
> anything sitting on the mount?
Yes, second umount succeed.
> 
> --D
> 
>>>
>>> --D
>>>
>>>>    	_unmount_flakey
>>>>    }
>>>> -- 
>>>> 2.18.0
>>>>
>>>>
>>>>
>>>
>>>
>>
>>
> 
>