[LTP] [PATCH v2] lib: tst_device: Allow more control over the device size

[LTP] [PATCH v2] lib: tst_device: Allow more control over the device size

[Cyril Hrubis]

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>
---

v2: Updated both places where we compute the device size as pointed out
    by Joerg

 lib/tst_device.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/tst_device.c b/lib/tst_device.c
index c91c6cd55..73e70d26e 100644
--- a/lib/tst_device.c
+++ b/lib/tst_device.c
@@ -278,7 +278,7 @@ int tst_dev_sync(int fd)
 
 const char *tst_acquire_loop_device(unsigned int size, const char *filename)
 {
-	unsigned int acq_dev_size = MAX(size, DEV_SIZE_MB);
+	unsigned int acq_dev_size = size ? size : DEV_SIZE_MB;
 
 	if (tst_prealloc_file(filename, 1024 * 1024, acq_dev_size)) {
 		tst_resm(TWARN | TERRNO, "Failed to create %s", filename);
@@ -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");
 
-- 
2.31.1

[LTP] [PATCH v2] lib: tst_device: Allow more control over the device size

[Petr Vorel]

Hi Cyril, Joerg,

Reviewed-by: Petr Vorel <pvorel@suse.cz>

Kind regards,
Petr

[LTP] [PATCH v2] lib: tst_device: Allow more control over the device size

[Joerg Vehlow]

Hi Cyril,

On 8/2/2021 2:17 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>
> ---
>
> v2: Updated both places where we compute the device size as pointed out
>      by Joerg
>
>   lib/tst_device.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/lib/tst_device.c b/lib/tst_device.c
> index c91c6cd55..73e70d26e 100644
> --- a/lib/tst_device.c
> +++ b/lib/tst_device.c
> @@ -278,7 +278,7 @@ int tst_dev_sync(int fd)
>   
>   const char *tst_acquire_loop_device(unsigned int size, const char *filename)
>   {
> -	unsigned int acq_dev_size = MAX(size, DEV_SIZE_MB);
> +	unsigned int acq_dev_size = size ? size : DEV_SIZE_MB;
>   
>   	if (tst_prealloc_file(filename, 1024 * 1024, acq_dev_size)) {
>   		tst_resm(TWARN | TERRNO, "Failed to create %s", filename);
> @@ -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");
>   

Thanks, looks good now. Tested with the squashfs test.

Joerg

[LTP] [PATCH v2] lib: tst_device: Allow more control over the device size

[Cyril Hrubis]

Hi!
> Thanks, looks good now. Tested with the squashfs test.

Pushed, thanks.

-- 
Cyril Hrubis
chrubis@suse.cz