[LTP] [PATCH 2/3] zram/zram_lib.sh: Skip test if zram module can not be removed

[xuyang2018.jy@fujitsu.com]

Hi Petr
> Hi Petr
>> Hi Xu,
>>
>> [ Cc Naresh Kamboju who added zram support to kconfig ]
> Oh, I don't know kernel selftest also have these two zram tests.
>>
>>> Hi Petr
>>>> Hi Xu,
>>
>>>> ...
>>>>>>> ps: zram01 need to rmmod and modprobe zram. So if kernel built with
>>>>>>> CONFIG_ZRAM=y, we also need to TCONF. But it is another story.
>>>>>> +1
>>
>>>> We already have v3, but I got confused here in v1, thus asking.
>>
>>>>> Since zram_lib.sh uses tst_needs_driver to search module in
>>>>> modules.dep/modules.builtin. Maybe we can introduce a new macro
>>>>> TST_NEEDS_MODULES (like TST_NEEDS_DIRVERS)?
>>>> I got lost here, did you suggest zram_lib.sh to switch to use $TST_NEEDS_MODULE?
>>> Sorry, I don't know ltp shell api already have this TST_NEEDS_MODULE
>>> macro and so suggest to add a new macro wrongly.
>>
>>> Yes, I want to use TST_NEEDS_MODULE instead of TST_NEEDS_DIRVERS because
>>> the former is more accurate.
>>
>>> But it seems  our TST_NEEDS_MODULE only can check custom kernel module
>>> but can't check system kernel module(like ext4.ko.xz, xfs.ext4.ko.xz).
>> Good catch, tst_require_module() in tst_test.sh should be fixed.
>> Also, if I look correctly, there is no TST_NEEDS_MODULE equivalent for C API
>> (probably not needed).
> Maybe add a issue for this, so we or others can do it in the future.
>>
>>> ps: kconfig shell api can also do the thing by using "config_zram=m". So
>>> I may use kconfig shell api in here in the feature.
>> FYI When Naresh Kamboju put LTP zram tests into kselftest back in 2015,
>> he modified it to support also zram built-in (CONFIG_ZRAM=y).
>>
>> We don't support it, thus CONFIG_ZRAM=m is OK now, but we should consider to add
>> at least some minimal support for CONFIG_ZRAM=y.
Maybe add sysfs interface, we can use hot_add in setup and hot_remove in 
cleanup even zram device is being used or  zram module is builtin.

Best Regards
Yang Xu
> Yes, kernel selftest supports CONFIG_ZRAM=y. Because zram01.sh in kernel
> selftest only used one zram device(It only supports ext4 filesystem but
> ltp supports all possible filesystem).
>
> Since most distribution should use CONFIG_ZRAM=m, I guess we don't need
> to support CONFIG_ZRAM=y and ltp can support more filesystems.
> Maybe can add a note that user can use kernel selftest when his kernel
> config is CONFIG_ZRAM=y.
>
> Also, It seems kernel selftest zram case is old
> 1) should remove zram_max_streams
> 2) should use mm_stat instead of free -m to calcaute ratio
> 3) should consider the situation that /dev/zram0 is being used
>
> Best Regards
> Yang Xu
>>
>> Kind regards,
>> Petr
>>
>>> Best Regards
>>> Yang Xu
>