overlay: don't trust the "trusted.overlay.opaque" xattr
overlay: don't trust the "trusted.overlay.opaque" xattr

If the overlay filesystem implements an optimization that landed in
97c684cc911060ba7f97c0925eaf842f159a39e8, and in the mainline kernel in
4.10, directories created in merged directories are marked as opaque by
the kernel to let the kernel know that it needn't bother looking at
other layers when reading the contents of that directory.

This means that, when generating a diff for an upper directory, we can't
treat the presence of an opaque attribute as enough of an indication
that a layer diff needs to include whiteout for a directory of the same
name from a lower layer.

Signed-off-by: Nalin Dahyabhai <f562fcb2a0b898bf0be1afc867ea92325d8f825f@redhat.com>

containers/storage,containers/storage,rhatdan/storage,rhatdan/storage,rhatdan/storage,containers/storage