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RE: Move and Delete (was: bind draft issues)

From: Julian Reschke <julian.reschke@gmx.de>
Date: Tue, 4 Mar 2003 18:27:08 +0100
To: "Jason Crawford" <nn683849@smallcue.com>, "Julian Reschke" <julian.reschke@gmx.de>
Cc: "Clemm, Geoff" <gclemm@Rational.Com>, "'WebDAV'" <w3c-dist-auth@w3.org>
Message-ID: <JIEGINCHMLABHJBIGKBCEEFLGKAA.julian.reschke@gmx.de>

> From: w3c-dist-auth-request@w3.org
> [mailto:w3c-dist-auth-request@w3.org]On Behalf Of Jason Crawford
> Sent: Tuesday, March 04, 2003 6:05 PM
> To: Julian Reschke
> Cc: Clemm, Geoff; 'WebDAV'
> Subject: RE: Move and Delete (was: bind draft issues)
>
>
>
>
>
>
> > > Just for interests sake, how many examples are there of
> > > repositories that do support multiple bindings to a collection
> > > but cannot support atomic DELETE/MOVE?
> > The Unix file system?
>
> Sort of.  On most (all?) Unix file systems you can't create a

It may depend on the implementation and your permissions.

> hard link to a directory, but you can create a soft/symbolic link.
> In essence, all directories have one hard link and zero or more
> symbolic links to them.  The symbolic link has no referential

Wrong.

Any directory has two hard links (it's entry in the parent, and the "."
entry as internal member). In addition, it gets hard links for each internal
member that is a directory (through it's ".." entry). You can check this
easily using ls.

> integrity, but that's probably not a major issue for a WebDAV
> server since the link can be traversed to confirm that the referee
> still exists.  (See caveat below.)
>
> To simulate BIND support one can use symbolic links.  In that

I'd be surprised if you could. If you delete a directory, how do you detect
that there are symlinks left pointing to it?

> ,...
>
> Whether it's a symbolic link or a
> hard link being removed, you still need to do a fix up of symbolic
> links in to the subtree being removed.  That obviously is not

Why do I need to fix up symlinks? It's their nature that they are weak
links. I'd be surprised if they track another resource automatically.

> atomic, but at the WebDAV level you can block or remap access
> until that's completed.s

I may be able to block that at the WebDAV level, but the WebDAV code may not
be able to block other access types (such as filesystem access).

> Or... you can just reject BIND requests to directories.  :-)

Even if I'd do that, the current wording of the BIND draft does not allow me
to keep my current RFC2518-compliant DELETE implementation. I feel this is a
problem.

> But more to the point of the discussion, there is nothing that will cause
> the file based Unix server to need to return a status code indicating that
only
> "part" of the DELETE/UNBIND operation occured.

Because rmdir() only applies to empty directories and therefore doesn't need
to consider this issue.

Julian

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Received on Tuesday, 4 March 2003 12:27:41 GMT

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