[OpenAFS] Re: AFS handling of deleted open files
Mon, 18 Jan 2021 12:33:49 -0800
Off the top of my head, the "vos release" workflows I deal with all involve
adding new data, not removing any.  So, in some cases it is prudent to send
a best-effort notification to potential consumers that they may experience
a pause in access, there's not a real need to specifically schedule the
release to avoid harming client applications. (In other cases I just do
the release whenever I want, such as when preparing new releases of OpenAFS
It would probably be more interesting to hear about other workflows...
 Even when updating software binaries, the binary or library is
typically installed at a versioned path, with an unversioned symlink that
gets updated to point to the "latest" version.
On Mon, Jan 18, 2021 at 03:20:04PM -0500, J. Bruce Fields wrote:
> The one other offlist response I got was that behavior can depend on the
> I guess what I'd really be most interested in is users' perspectives: is
> a "vos release" something you do you routinely with no special
> precautions? Or do you have to, say, schedule them for times when
> client applications aren't running to prevent crashes?
> On Mon, Jan 11, 2021 at 10:30:11AM -0500, J. Bruce Fields wrote:
> > Is there a better forum for this kind of question? I'm most interested
> > in the case where an in-use file is absent in a new version.
> > Summarizing a few points from a side conversation from Matt Benjamin.
> > (But any misunderstandings are mine, as my only AFS experience is purely
> > as a user 20+ years ago!):
> > AFS, like NFS, has "silly rename". The open happens on a read-only
> > replica, and the unlink on the read-write volume, so it's not obvious to
> > me when the silly rename would happen:
> > If it happens at the time of the unlink, I think that requires some sort
> > of protocol ensuring we know about the opens at unlink time.
> > Maybe it could instead happen at "vos release" time, silly-renaming on
> > the read-only replicas as necessary. That would mean different replicas
> > would no longer be identical--in-use but unlinked files could be present
> > on some replicas but not others.
> > Or maybe the client (cache manager) could handle this somehow. That
> > would require it to cache whole files.
> > Is AFS's handling of this case documented somewhere?
> > --b.
> > On Wed, Jan 06, 2021 at 09:20:39AM -0500, bfields wrote:
> > > When a read-only replica is updated, and files still in use by processes
> > > are modified or absent from the new version, what behavior do those
> > > processes see?
> > >
> > > What about in normal operation, if a file is in use while it's deleted
> > > by the same client or a different client?
> > >
> > > I'm working on the NFS behavior and just looking for a comparison.
> > > Thanks in advance for any pointers. This is probably all pretty
> > > elementary, but my searches weren't turning up answers....
> > >
> > > --b.
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