tst-open-tmpfile and pre-3.18 kernels

[Joseph Myers]

I'm observing a test failure

FAIL: io/tst-open-tmpfile

on a system with a 3.14 kernel.  This appears to correspond to a lack of 
the fix:

commit 69a91c237ab0ebe4e9fdeaf6d0090c85275594ec
Author: Eric Rannaud <e@nanocritical.com>
Date:   Thu Oct 30 01:51:01 2014 -0700

    fs: allow open(dir, O_TMPFILE|..., 0) with mode 0

meaning I get

error: openat ("/dev/shm", O_TMPFILE | O_RDWR): Permission denied

in tst-open-tmpfile.out.

Should we make the test also treat EACCES as meaning lack of O_TMPFILE 
support to allow for this kernel bug, or just document this on the release 
wiki page as a known cause of a test failure?

-- 
Joseph S. Myers
joseph@codesourcery.com