On Tue, Jan 15, 2019 at 10:34 PM Dominique Martinet [off-list ref]
wrote:

There is a difference with your previous patch though, that used to list no
page in core when it didn't know; this patch lists pages as in core when it
refuses to tell. I don't think that's very important, though.

Is there a reason not to return -EPERM in this case?

If anything, the 0400 user-owner file might be a problem in some edge
case (e.g. if you're preloading git directories, many objects are 0444);
should we *also* check ownership?...

Yes, this seems valuable. Some databases with immutable files (e.g. git, as
you've mentioned) conceivably operate this way.

Josh