[LTP] [PATCH v2] Testing statx syscall

vaishnavi.d
2018-07-19T12:51:46Z

Hello,
>
> Hi!
>> Thanks for the review comments. We are working on resolving those
>> issues.
>> But, we have doubts regarding two comments.
>>
>> Regarding block size, looking at the behaviour of statx, we observed
>> that
>> statx automatically upscales the size value to the nearest blocksize of
>> that file system.
>>
>> For instance,
>> Case 1:
>> size = 10 and stx_blocksize = 4096
>> Blocks = 8
>>
>> Case 2:
>> size = 5012 and stx_blocksize = 4096
>> Blocks = 16
>>
>> blocks = ((5012 / 4096) + 1) * (4096 / 512)
>> = 16
>>
>> So, that is why we are incrementing (SIZE/stx_blksize) by 1 an
>> mutiplying
>> it by (stx_blksize/512) to get number of blocks.
>
> There are some assumptions that may not holt true here. The stx_blksize
> is supposed to be optimal block size for I/O, it may match the blocksize
> used by the filesystem but I doubt that it's guaranteed.
>
> And while it's likely that the stx_blocksize would be divideable by 512
> that one is not guaranteed either.
>
> However even if we decide to use it the way you compute the number of
> blocks based on size is unnecessarily complex, we just need to round the
> size to be nearest multiple of stx_blocksize and then divide it with
> 512, that is easily done with:
>
> (size + stx_blocksize - 1) / stx_blocksize * (stx_blocksize / 512);
>

Yeah, we will change to this formulae.

>> Also, since only ext4 supports these attribute flags for now, we have
>> used
>> that alone in our test case.
>
> Okay then, if it's supported only by ext4 then we should go with that
> for now, but we should make sure that mkfs.ext4 is present and that the
> kernel supports ext4. We do have a functions for that in the C test
> library.
>
>> Also we have used script because we don't have any equivalent for
>> tune2fs
>> and e4crypt.
>
> Looking closer, the tune2fs writes some bytes to the device, indeed that
> is something we do not want to replicate in our tests. But we can call
> the binary easily from the C test as well.
>
We are unable to understand this part, Can you help us with this please??

> The e4crypt seems to be doing add_key() syscall with the pasphrase but
> does some magic with sha512 and salt so it would be easier to run the
> e4crypt tool as well.
>
> BTW you can actually get a device formatted with ext4 in the C testcase
> by setting only single flag in the test library and it will correctly
> exit the test if ext4 is not supported...
>
> --
> Cyril Hrubis
> chrubis@suse.cz
>

Regards,
Vaishnavi.D
Tarun.T.U