[LTP] TMPDIR minimal size requirement

[Petr Vorel]

Hi all,

recent LTP change 3626124a4 ("fallocate06: Increase test loop device size to
1GB") [1] increased requirement on TMPDIR size for syscalls. That hits the size
of tmpfs we use in openSUSE Tumbleweed on /tmp. While we can workaround easily
this in openQA framework we use for LTP testing (use TMPDIR=/var/tmp for
fallocate06 or even for whole runtest syscalls), I wonder if we should have some
LTP upstream fix.

What comes to mi mind, we could use as TMPDIR default /var/tmp (only if it does
not exists, we would fallback to /tmp). We could also warn against tmpfs use.
Or at least document on README that although many tests need 300 MB for a block
device, some tests require more and suggest to use /var/tmp.

Also, Cyril asked for a patch with minimal device size per filesystem (IMHO
still would be done). At least for Btrfs and XFS some people complains 300
MB is not a real testing scenario, therefore if we implement it and use 1 GB
e.g. for Btrfs and XFS we will hit limits on "low resource" devices.

Kind regards,
Petr

[1] https://github.com/linux-test-project/ltp/commit/3626124a42adfe536af2abff63213fa1ccc63795