[LTP] [PATCH v4 1/3] lib: alter find_free_loopdev()

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

>
>> Hi!
>>>> This needs more changes than this.
>>>> The problem here is that the function modifies dev_path which is
>>>> returned by tst_acquire_device() so if you call this function after
>>>> tst_acquire_device() it will rewrite the dev_path which means that the
>>>> test would end up with wrong device path in tst_device->dev.
>>>>
>>>> I guess that the easiest solution would be changing the function to get
>>>> buffer parameter which, when non-NULL, is filled with the path.
>>>> I.e. the function prototype would became:
>>>> int tst_find_free_loopdev(char *path, size_t path_len);
>>>> And we would pass the dev_path inside of the tst_device.c and NULL from
>>>> the copy_file_range() tests.
>>> Hi Cyril
>>> This is a good comment. But I doubt why we don't use a set_devpath_flag todistinguish it.
>>> Or you have a future plan(in different directory ,/dev,/dev/loop/,/dev/block)?
>> Well you can add a flag to the function but that would be a bad design
>> as far as I can tell. It would still allowed for a user to modify the
>> library internal state by calling the tst_find_free_loopdev() with the
>> flag set.
> Hi  Cyril
> Even we use int tst_find_free_loopdev(char *path, size_t path_len), user aslo can modify the internal state.
> I don't know how to limit it. Can you give some example code? If we set LTP_DEV in *tst_acquire_device__,
> we can pass dev and len to tst_find_free_loopdev(), but if we not set LTP_DEV, what can pass to tst_free_loopdev()?
Hi Cyril

ping.  :-)

> Thanks
> Yang Xu
>