> In message <20070110161215.GB12654 atrey.karlin.mff.cuni.cz>, Jan Kara writes:
> > > In message <20070109122644.GB1260atrey.karlin.mff.cuni.cz>, Jan Kara writes:
> [...]
> > > Jan, all of it is duable: we can downgrade
the f/s to readonly, grab various
> > > locks, search through various lists looking
for open fd's and such, then
> > > decide if to allow the mount or not. And
hopefully all of that can be done
> > > in a non-racy manner. But it feels just
rather hacky and ugly to me. If
> > > this community will endorse such a solution,
we'll be happy to develop it.
> > > But right now my impression is that if we
posted such patches today, some
> > > people will have to wipe the vomit off of
their monitors... 
> > I see . To me it
just sounds as if you want to do remount-read-only
> > for source filesystems, which is operation we
support perfectly fine,
> > and after that create union mount. But I agree you
cannot do quite that
> > since you need to have write access later from
your union mount. So
> > maybe it's not so easy as I thought.
> > On the other hand, there was some effort to
support read-only bind-mounts of
> > read-write filesystems (there were even some
patches floating around but
> > I don't think they got merged) and that should be
even closer to what
> > you'd need...
>
> I didn't know about those patches, but yes, they do
sound useful. I'm
> curious who needed such functionality before and why.
If someone can point
> me to those patches, we can look into using them for
Unionfs. Thanks.
Dave Hansen writes them. One of recent submissions starts
for example at
http://openvz.org/pipermail/devel/2006-December/0025
43.html.
Honza
--
Jan Kara <jacksuse.cz>
SuSE CR Labs
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