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From: Miklos Szeredi <miklos@szeredi.hu>
To: Amir Goldstein <amir73il@gmail.com>
Cc: Chengguang Xu <cgxu519@mykernel.net>,
	overlayfs <linux-unionfs@vger.kernel.org>
Subject: Re: [PATCH] ovl: consistent behavior for immutable/append-only inodes
Date: Wed, 9 Jun 2021 09:28:25 +0200	[thread overview]
Message-ID: <CAJfpegtupBqa6c4qgMVayWZO+5noGEnSAd9tOWySedx+VA=5JQ@mail.gmail.com> (raw)
In-Reply-To: <CAOQ4uxheGdKSqEBYAOTf7=UwqeW=JAaZBwaCs-ng28G7rtqZ7Q@mail.gmail.com>

On Wed, 9 Jun 2021 at 08:08, Amir Goldstein <amir73il@gmail.com> wrote:
>
> On Tue, Jun 8, 2021 at 9:20 PM Miklos Szeredi <miklos@szeredi.hu> wrote:
> >
> > On Tue, 8 Jun 2021 at 17:33, Amir Goldstein <amir73il@gmail.com> wrote:
> > >
> > > On Tue, Jun 8, 2021 at 5:49 PM Miklos Szeredi <miklos@szeredi.hu> wrote:
> > > >
> > > > On Tue, 8 Jun 2021 at 16:37, Amir Goldstein <amir73il@gmail.com> wrote:

> > > > > While you are here, do you think that will be sufficient for the on-disk format
> > > > > of overlay.xflags?
> > > > >
> > > > > struct ovl_xflags {
> > > > >         __le32 xflags;
> > > > >         __le32 xflags_mask;
> > > > > }
> > > >
> > > > I think I'd prefer a slightly more complex, but user friendlier
> > > > "+i,-a,..." format.
> > > >
> > >
> > > OK, but since this is not a merge, we'd only need:
> > > overlay.xflags = "ia..."
> > >
> > > Which is compatible with the format of:
> > > chattr =<xflags> <file>
> >
> > Fine.   Not sure what xflags_mask would be useful for in your proposal, though.
> >
>
> The idea was that in the context of fileattr_get(), any specific xflag
> value can be one of: SET, CLEAR, REAL.
>
> For most inodes all flags are REAL (no xflags xattr)
> All flags but the 4 in OVL_FS_XFLAGS_MASK are always REAL
> (i.e. taken from fileattr_get() on real inode).
>
> If we ever decide to extend OVL_FS_XFLAGS_MASK, say to include
> DIRSYNC, then an upper inode with DIRSYNC that was in state
> REAL before upgrade would become CLEAR after upgrade unless
> we kept the old xflags_mask in xattr.
>
> With the string format, this is not a concern.
> Therefore, I like the string format better.

Hmm, so if the attribute letters would have fixed places in the string
and clear attributes would be represented by a space or a "-" then
that would be similarly extensible.   Just having a list of set
attribute letters would not allow having three states.

Thanks,
Miklos

  reply	other threads:[~2021-06-09  7:29 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-06 14:46 Amir Goldstein
2021-06-08 13:52 ` Miklos Szeredi
2021-06-08 14:37   ` Amir Goldstein
2021-06-08 14:49     ` Miklos Szeredi
2021-06-08 15:33       ` Amir Goldstein
2021-06-08 18:20         ` Miklos Szeredi
2021-06-09  6:08           ` Amir Goldstein
2021-06-09  7:28             ` Miklos Szeredi [this message]
2021-06-09  7:57               ` Amir Goldstein
2021-06-11  7:31                 ` Amir Goldstein
2021-06-11  7:55                   ` Miklos Szeredi
2021-06-11  8:37                     ` Amir Goldstein
2021-06-11  8:39                       ` Miklos Szeredi

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