Received-SPF: pass (google.com: domain of linux-ext4-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <e84b9caf376a9b958a95ca4e0d088808c482f109.camel@kernel.org>
Subject: Re: should we make "-o iversion" the default on ext4 ?
From:   Jeff Layton <jlayton@kernel.org>
To:     Benjamin Coddington <bcodding@redhat.com>
Cc:     Lukas Czerner <lczerner@redhat.com>, tytso@mit.edu,
        adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>
Date:   Wed, 20 Jul 2022 12:15:05 -0400
In-Reply-To: <BAFC8295-B629-49DB-A381-DD592182055D@redhat.com>
References: <69ac1d3ef0f63b309204a570ef4922d2684ed7f9.camel@kernel.org>
         <20220720141546.46l2d7bxwukjhtl7@fedora>
         <ad7218a41fa8ac26911a9ccb79c87609d4279fea.camel@kernel.org>
         <BAFC8295-B629-49DB-A381-DD592182055D@redhat.com>
Content-Type: text/plain; charset="ISO-8859-15"
Content-Transfer-Encoding: quoted-printable
User-Agent: Evolution 3.44.3 (3.44.3-1.fc36) 
MIME-Version: 1.0
Precedence: bulk

On Wed, 2022-07-20 at 11:56 -0400, Benjamin Coddington wrote:
> On 20 Jul 2022, at 10:38, Jeff Layton wrote:
> > On Wed, 2022-07-20 at 16:15 +0200, Lukas Czerner wrote:
> > >=20
> > > Is there a different way I am not seeing?
> > >=20
> >=20
> > Right, implementing this is the difficult bit actually since this uses =
a
> > MS_* flag.=A0If we do make this the default, we'd definitely want to
> > continue allowing "-o noiversion" to disable it.
> >=20
> > Could we just reverse the default in libmount? It might cause this to
> > suddenly be enabled in some deployments, but in most cases, people
> > wouldn't even notice and they could still specify -o noiversion to turn
> > it off.
> >=20
> > Another idea would be to introduce new mount options for this, but
> > that's kind of nasty from a UI standpoint.
>=20
> Is it safe to set SB_I_VERSION at export time?  If so, export_operations
> could grow an ->enable_iversion().
>=20

That sounds like it might be problematic.

Consider the case where a NFSv4 client has cached file data and the
change attribute for the file. Server then reboots, but before the
export happens a local user makes a change to the file and it doesn't
update the i_version.
--=20
Jeff Layton <jlayton@kernel.org>