Messages in this thread |  | | From | Andy Lutomirski <> | Date | Thu, 13 Feb 2014 10:21:42 -0800 | Subject | Re: [PATCH 00/13] cross rename v4 |
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On Thu, Feb 13, 2014 at 9:28 AM, Miklos Szeredi <miklos@szeredi.hu> wrote: > On Thu, Feb 13, 2014 at 5:42 PM, David Howells <dhowells@redhat.com> wrote: >> Miklos Szeredi <miklos@szeredi.hu> wrote: >> >>> Regarding whiteouts, I raised a couple of questions that nobody answered >>> yet, so let me ask again. >>> >>> - If a filesystem containing whiteouts (fallthroughs, etc...) is mounted as >>> not part of a union, how are these special entities represented to >>> userspace? >> >> I would suggest that whiteouts appear as otherwise negative dentries and that >> they don't appear in getdents(). > > I'd argue that this is an administration nightmare. E.g. what if the > a backup needs to be made of the rw layer? > > Will rmdir work normally in a directory containing whiteouts? Will > the VFS take care of that, just like if it was part of a union? Or > will it fail with ENOTEMPTY despite *appearing* empty? > > And zillion other problems related to the fact that things happen to a > filesystem even when they do not appear to happen ("mv foo bar; mv bar > foo" has side effects).
Are there any users of unions / overlays who will want to modify the bottom layer after creating the top layer? I'm starting to think that changing the bottom layer should require userspace to do a three-way merge or something and explicitly decide what it wants to do.
--Andy
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