[LTP] [PATCH] lib/tst_supported_fs_types.c: Add tmpfs to filesystem whitelist

[zhaogongyi]

Hi Cyril,

I have resubmit the patch according to your review.

Thanks so much!

> 
> Hi!
> > > But there is another problem there, since the code still mounts
> > > tmpfs on tmpdir for a short while, which is temporary directory used
> > > by all LTP tests, which may potentially break tests that runs in parallel.
> >
> > 	In general, when all_filesystems has been set to 1,  the
> needs_tmpdir would be set to 1 and the mntpoint must has been set to
> some path, so the test run in /tmp/tmpxxxxxx/mntpoint and
> > 	other LTP tests would run in another tmpdir. So it has no problem for
> running in parallel.
> >
> > 	I don't know if I understand it right.
> 
> The has_kernel_support() uses TMPDIR as the mount point, which is the
> parent directory for all LTP tests, moreover it often points to just "/tmp". If
> you mount anything over that directory, even for a short while, the whole
> system will get different and empty "/tmp" which will possibly break many
> things.
> 
> We may get over this with using "." instead, in a case that testcase has
> created temporary directory and changed the PWD to it, but it's not that
> simple either, since tst_test.c is not the only place that calls
> has_kernel_support().
> 
> We have testcases/lib/tst_supported_fs.c helper as well that is used by
> shell tests. This is a standalone binary that does not create a temporary
> directory and should work even without TMPDIR being set, which is the
> reason we have the if (!tmpdir) tmpdir = "/tmp"; check in the
> has_kernel_support() function to begin with.
> 
> So all in all I guess that safest option would be to create a unique
> temporary directory under TMPDIR and use it as a mount point in the
> has_kernel_support() function.
> 
> --
> Cyril Hrubis
> chrubis@suse.cz