Problem writing to ovl with CIFS as lower dir

[Nikolay Borisov <kernel@kyup.com>]

Hello,

[I'm not subscribed to the list please CC me when replying]

I'm testing overlayfs on 3.12 (own-made port) and on 4.4 (to confirm
behavior) and what I observe is that when I try to write to a file in
the merge directory e.g:

echo "test" > merged/test-file1

I get -EINVAL on 3.12 and -ENXIO on 4.4. However, when I try to touch a
file in the merged directory I have no issues. This happens only when
the lower mount is either CIFS/NFS. When it's another ext4 directory I
have no problems whatsoever. Is this behavior expected, I'm willing to
assume I've screwed up the 3.12 port but given that I see this on 4.4
(no custom modifications) I'm beginning to think this is innate into the
the design?

Regards,
Nikolay