[LTP] [PATCH] lib: tst_device: Allow more control over the device size

[Joerg Vehlow <lkml@jv-coder.de>]

Hi Cyril,

On 7/30/2021 3:31 PM, Cyril Hrubis wrote:
> There is actually no reason for lower limit on the device size, and we
> can safely allow the tests to request smaller device than the default
> hardcoded in the library. The backing file is preallocated without
> actually writing to it as long as the underlying filesystem supports it
> so the speedup will be minimal if measurable but we will at least spare
> some space which needs to be reserved on the filesystem which is still a
> good thing.
>
> The test may end up with a device that is bigger than the requsted size
> in a case that a real device was passed to the LTP for the testrun.  So
> tests should be able to cope with that and that's also the reason why
> the turning knob is still called dev_min_size.
>
> Also currently we use the dev_min_size only to increase the device size
> for a few tests so this change is safe and cannot break anything.
>
> CC: Joerg Vehlow <lkml@jv-coder.de>
> Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
> ---
>   lib/tst_device.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/lib/tst_device.c b/lib/tst_device.c
> index c91c6cd55..4ef802c41 100644
> --- a/lib/tst_device.c
> +++ b/lib/tst_device.c
> @@ -300,7 +300,7 @@ const char *tst_acquire_device__(unsigned int size)
>   	unsigned int acq_dev_size;
>   	uint64_t ltp_dev_size;
>   
> -	acq_dev_size = MAX(size, DEV_SIZE_MB);
> +	acq_dev_size = size ? size : DEV_SIZE_MB;
>   
>   	dev = getenv("LTP_DEV");
>   
This is not enough. tst_acquire_device__ calls tst_acquire_loop_device, 
that again has MAX(size, DEV_SIZE_MB).
But it should be sage to substitute it for size ? size : DEV_SIZE_MB as 
well.

Joerg