Re: [PATCH v4 2/2] xfs/006: new case to test xfs fail_at_unmount error handling

[Eric Sandeen <sandeen@sandeen.net>]

On 6/21/16 8:42 PM, Zirong Lang wrote:
> Hi Dave
> 
> ----- 原始邮件 -----
>> 发件人: "Dave Chinner" <david@fromorbit.com>
>> 收件人: "Eryu Guan" <eguan@redhat.com>
>> 抄送: "Zorro Lang" <zlang@redhat.com>, fstests@vger.kernel.org, sandeen@redhat.com, cem@redhat.com
>> 发送时间: 星期三, 2016年 6 月 22日 上午 8:00:40
>> 主题: Re: [PATCH v4 2/2] xfs/006: new case to test xfs fail_at_unmount error handling
>>
>> On Tue, Jun 21, 2016 at 03:08:18PM +0800, Eryu Guan wrote:
>>> On Mon, Jun 20, 2016 at 09:24:33PM +0800, Zorro Lang wrote:
>>>> +# real QA test starts here
>>>> +_supported_fs xfs
>>>> +_supported_os Linux
>>>> +_require_dm_target error
>>>> +_require_scratch
>>>> +
>>>> +_scratch_mkfs > $seqres.full 2>&1
>>>> +_require_fs_sysfs $SCRATCH_DEV error/fail_at_unmount
>>>
>>> Usually we call _require_xxx before mkfs and do the real test, a comment
>>> to explain why we need to mkfs first would be good.
>>
>> Ok, so why do we need to test the scratch device for this
>> sysfs file check? We've already got the test device mounted, and
>> filesystems tend to present identical sysfs control files for all
>> mounted filesystems.
>>
>> i.e. this _require_fs_sysfs() function could just drop the device
>> and check the test device for whether the sysfs entry exists. If it
>> doesn't, then the scratch device isn't going to have it, either.
> 
> Hmm... at first I thought about if I should use TEST_DEV to do _require_fs_sysfs
> checking. But I'm not sure if different devices maybe bring different sysfs
> attributes in, if someone make a special device in one case? So I give one more
> argument about device name.

Sorry, I was kind of thinking this as well on my first review, but I let it pass.

I would say that for now, let's just use TEST_DEV.  There is no reason to code
around "what-if" scenarios.  If a filesystem ends up needing a special mkfs
or mount option to expose a sysfs tunable in the future, we can add a device name
at that point. Until then, I don't think there is any reason, and the "mkfs first,
then require" is definitely a little bit out of the ordinary.

-Eric