From: Miklos Szeredi <miklos@szeredi.hu>
To: Amir Goldstein <amir73il@gmail.com>
Cc: Miklos Szeredi <mszeredi@redhat.com>,
overlayfs <linux-unionfs@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Vivek Goyal <vgoyal@redhat.com>
Subject: Re: [PATCH 4/4] ovl: alllow remote upper
Date: Fri, 31 Jan 2020 16:38:33 +0100 [thread overview]
Message-ID: <CAJfpegvMz-nHOb3GkoU_afqRrBKt-uvOXL6GxWLa3MVhwNGLpg@mail.gmail.com> (raw)
In-Reply-To: <CAOQ4uxgV9KbE9ROCi5=RmXe1moqnmwWqaZ98jDjLcpDuM70RGQ@mail.gmail.com>
On Fri, Jan 31, 2020 at 4:30 PM Amir Goldstein <amir73il@gmail.com> wrote:
>
> On Fri, Jan 31, 2020 at 1:51 PM Miklos Szeredi <mszeredi@redhat.com> wrote:
> >
> > No reason to prevent upper layer being a remote filesystem. Do the
> > revalidation in that case, just as we already do for lower layers.
> >
>
> No reason to prevent upper layer from being a remote filesystem, but
> the !remote criteria for upper fs kept away a lot of filesystems from
> upper. Those filesystems have never been tested as upper and many
> of them are probably not fit for upper.
>
> The goal is to lift the !remote limitation, not to allow for lots of new
> types of upper fs's.
>
> What can we do to minimize damages?
>
> We can assert that is upper is remote, it must qualify for a more strict
> criteria as upper fs, that is:
> - support d_type
> - support xattr
> - support RENAME_EXCHANGE|RENAME_WHITEOUT
>
> I have a patch on branch ovl-strict which implements those restrictions.
Sounds good. Not sure how much this is this going to be a
compatibility headache. If it does, then we can conditionally enable
this with a config/module option.
>
> Now I know fuse doesn't support RENAME_WHITEOUT, but it does
> support RENAME_EXCHANGE, which already proves to be a very narrow
> filter for remote fs: afs, fuse, gfs2.
> Did not check if afs, gfs2 qualify for the rest of the criteria.
>
> Is it simple to implement RENAME_WHITEOUT for fuse/virtiofs?
Trivial.
> Is it not a problem to rely on an upper fs for modern systems
> that does not support RENAME_WHITEOUT?
Limited r/w overlay functionality is still available without
whiteout/xattr support, so it could turn out to be something people
already rely on. Can't tell without trying...
Thanks,
Miklos
next prev parent reply other threads:[~2020-01-31 15:38 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-31 11:50 [PATCH 0/4] ovl: allow virtiofs as upper Miklos Szeredi
2020-01-31 11:50 ` [PATCH 1/4] ovl: restructure dentry revalidation Miklos Szeredi
2020-01-31 11:50 ` [PATCH 2/4] ovl: separate detection of remote upper layer from stacked overlay Miklos Szeredi
2020-01-31 11:50 ` [PATCH 3/4] ovl: decide if revalidate needed on a per-dentry bases Miklos Szeredi
2020-01-31 14:53 ` Amir Goldstein
2020-01-31 15:15 ` Miklos Szeredi
2020-01-31 11:50 ` [PATCH 4/4] ovl: alllow remote upper Miklos Szeredi
2020-01-31 15:29 ` Amir Goldstein
2020-01-31 15:38 ` Miklos Szeredi [this message]
2020-01-31 15:50 ` Amir Goldstein
2020-01-31 16:05 ` Miklos Szeredi
2020-02-04 14:59 ` Vivek Goyal
2020-02-04 16:16 ` Miklos Szeredi
2020-02-04 17:02 ` Amir Goldstein
2020-02-04 18:42 ` Vivek Goyal
2020-02-04 19:11 ` Amir Goldstein
2020-02-04 19:16 ` Miklos Szeredi
2020-02-20 7:52 ` Amir Goldstein
2020-02-20 20:00 ` Amir Goldstein
2020-03-14 13:16 ` Amir Goldstein
2020-03-16 17:54 ` Vivek Goyal
2020-03-16 19:02 ` Amir Goldstein
2020-03-16 19:40 ` Vivek Goyal
2020-03-18 13:36 ` unionmount testsuite with upper virtiofs Amir Goldstein
2020-03-19 21:40 ` Vivek Goyal
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