On Tue, Mar 21, 2017 at 1:37 PM, Miklos Szeredi [off-list ref] wrote:

What overlayfs issues?  Overlayfs behaves exactly like a normal
filesystem wrt negative dentries.

Ignore me. I did indeed just confuse whiteouts with the normal
negative dentries.

I think this is historic.  may_delete() was doing the same as
may_create() and more.  Doesn't look like that's still strictly true,
so it might make sense to add a may_replace() operation that does
both.

They are definitely very different these days, with may_create()
requiring a valid UID mapping into the filesystem, for example.

That may make no sense for the move/link case, of course (since the
uid comes from the source file, not the current process), so it is
possible that may_delete() ends up being effectively a superset of the
may_create() things apart from that one thing, of course.

The one noticeable difference would seem to be the audit difference.
Maybe nobody cares.

               Linus