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

[xuyang2018.jy@fujitsu.com]

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.
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