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

[Amir Goldstein]

On Fri, Jul 12, 2019 at 8:26 AM Yang Xu <xuyang2018.jy@cn.fujitsu.com> wrote:
>
>
> > 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()?
>
>

I don't understand your concern.
Attached untested patch which implements Cyril's suggestion.

You may call tst_find_free_loopdev(NULL, 0) to get a free minor number
without changing lib internal state.

Thanks,
Amir.
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