[LTP] [PATCH] syscalls/statx01: loosen the stx_blocks check

[Steve Muckle]

On 7/24/19 4:57 AM, Cyril Hrubis wrote:
> Hi!
>>> Why 128?
>>
>> Was just restoring it to what it was previously.
>>
>>> Can't we rather multiply the buff.stx_blksize/512 by 16?
>>
>> That would work for ext4, but should this be loosened further to give
>> some headroom in case some FS preallocates more? Or is it preferable to
>> keep the test as strict as possible and loosen it when/if failures happen?
> 
> That is hard to decide. I would go for the lowest limit that works for
> everybody.
> 
> Also for me ext4 allocates only one block for the file no matter what I
> do, something has to be tuned differently in your setup.
> 
> Isn't it just a difference in the block size and inode size?

On my platform stx_blocks = 16 (8kb) and stx_blksize = 4096, so two fs 
blocks are being allocated.

Interestingly, if I create a 256 byte file on this Android platform in 
/data, it 4kb:

vsoc_x86:/data # dd if=/dev/zero of=test_file bs=1 count=256
256+0 records in
256+0 records out
256 bytes (256 B) copied, 0.000926 s, 270 K/s
vsoc_x86:/data # ls -ls test_file
4 -rw-rw-rw- 1 root root 256 2019-07-24 19:28 test_file

However if I go into the directory specified in TMPDIR, it takes 8kb:

vsoc_x86:/data/local/tmp # dd if=/dev/zero of=test_file bs=1 count=256
256+0 records in
256+0 records out
256 bytes (256 B) copied, 0.000927 s, 270 K/s
vsoc_x86:/data/local/tmp # ls -ls
total 8
8 -rw-rw-rw- 1 root root 256 2019-07-24 19:30 test_file

It is also 8kb if I create it in /data/local, but not if I create a 
directory at /data/testdir and create the file there.

Perhaps the x-attributes are spilling out of the inode in some cases and 
into a data block? I don't know enough about filesystems to say.