Subject: Re: union fs changes
To: None <firstname.lastname@example.org>
From: Charles M. Hannum <email@example.com>
Date: 12/30/1994 17:08:40
One more problem: having to use two steps to make the lower
layer file reappear seems counterintuitive. I'd expect
unlink() to just remove the upper layer file so that the
lower layer file instantly reappears. This is clean and
`Clean and simple' and completely breaks the semantics of unlink(2)?
Did you forget a smilie in there?
automagically create whiteout. What happens if you have
*no* write access in the upper layer but *do have* write
access on the lower layer? (Assuming you can have more
layers), what happens if you have write access on one of
the intermediate layers? How does one remove a file from
a lower layer?
The *only* way to make a file in the lower layer appear to be gone is
by creating a `whiteout'. The lower layer is considered read-only.
More problems: what happens when you remove a file, then
create another file of the same name in the same directory
and now want to ``unremove'' the old file?
You have to unlink(2) the new file, and then undelete(2) the whiteout.
when you create a new file of the same name and remove it?
You end up with a whiteout again.