[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20100621231720.GC28850@shell>
Date: Mon, 21 Jun 2010 19:17:20 -0400
From: Valerie Aurora <vaurora@...hat.com>
To: Miklos Szeredi <miklos@...redi.hu>
Cc: raa.lkml@...il.com, viro@...iv.linux.org.uk, jblunck@...e.de,
hch@...radead.org, linux-kernel@...r.kernel.org,
linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 17/38] union-mount: Union mounts documentation
On Mon, Jun 21, 2010 at 03:14:35PM +0200, Miklos Szeredi wrote:
> On Thu, 17 Jun 2010, Valerie Aurora wrote:
> > On Thu, Jun 17, 2010 at 10:01:30AM +0200, Alex Riesen wrote:
> > > On Tue, Jun 15, 2010 at 20:39, Valerie Aurora <vaurora@...hat.com> wrote:
> > > > +git://git.kernel.org/pub/scm/fs/ext2/val/e2fsprogs.git
> > > > +
> > > > +Currently, whiteout directory entries are not returned to userland.
> > > > +While the directory type for whiteouts, DT_WHT, has been defined for
> > > > +many years, very little userland code handles them. ??Userland will
> > > > +never see fallthru directory entries.
> > >
> > > This may be a dumb question (I must admit I did only very little research),
> > > but how does one cleanup the topmost layer of whiteouts and fallthroughs,
> > > so that the entries of lower layer(s) can be made visible again?
> >
> > I'm not sure how best to do this. We don't want to add more system
> > calls. One thought of mine has been to do this offline, when the file
> > system is unmounted. For example, e2fsck could add a feature to
> > delete whiteouts and fallthrus. Another option is to add a flag to an
> > existing system call.
>
> One more advantage of doing whiteouts, etc. with hard links and
> extended attributes instead of as special filesystem objects. That
> way they are visible (unless part of a union) and can be treated as
> normal filesystem objects.
This should be reasonably easy to prototype - the whiteout and
fallthru patches are pretty well separated from the rest of union
mounts.
-VAL
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists