Re: [PATCH v2] locks: eliminate false positive conflicts for write lease

From: Jeff Layton <jlayton@kernel.org>
To: Amir Goldstein <amir73il@gmail.com>,
	"J . Bruce Fields" <bfields@fieldses.org>
Cc: Miklos Szeredi <miklos@szeredi.hu>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
	overlayfs <linux-unionfs@vger.kernel.org>
Subject: Re: [PATCH v2] locks: eliminate false positive conflicts for write lease
Date: Tue, 09 Jul 2019 07:02:42 -0400	[thread overview]
Message-ID: <d86b0afa34654da16b4ecfeb6d23a6b0efcea3ba.camel@kernel.org> (raw)
In-Reply-To: <CAOQ4uxjBGHh9cU7EX7X3F-iVFZkD+kax2x+Hj8YX83HMiwLqSw@mail.gmail.com>

On Mon, 2019-07-08 at 19:09 +0300, Amir Goldstein wrote:
> On Thu, Jun 13, 2019 at 5:08 PM J . Bruce Fields <bfields@fieldses.org> wrote:
> > On Thu, Jun 13, 2019 at 04:28:49PM +0300, Amir Goldstein wrote:
> > > On Thu, Jun 13, 2019 at 4:22 PM Jeff Layton <jlayton@kernel.org> wrote:
> > > > Looks good to me. Aside from the minor nit above:
> > > > 
> > > >     Reviewed-by: Jeff Layton <jlayton@kernel.org>
> > > > 
> > > > I have one file locking patch queued up for v5.3 so far, but nothing for
> > > > v5.2. Miklos or Bruce, if either of you have anything to send to Linus
> > > > for v5.2 would you mind taking this one too?
> > > > 
> > > 
> > > Well. I did send a fix patch to Miklos for a bug introduced in v5.2-rc4,
> > > so...
> > 
> > I could take it.  I've modified it as below.
> > 
> > I'm very happy with the patch, but not so much with the idea of 5.2 and
> > stable.
> > 
> > It seems like a subtle change with some possibility of unintended side
> > effects.  (E.g. I don't think this is true any more, but my memory is
> > that for a long time the only thing stopping nfsd from giving out
> > (probably broken) write delegations was an extra reference that it held
> > during processing.) And if the overlayfs bug's been there since 4.19,
> > then waiting a little longer seems OK?
> > 
> 
> Getting back to this now that the patch is on its way to Linus.
> Bruce, I was fine with waiting to 5.3 and I also removed CC: stable,
> but did you mean that patch is not appropriate for stable or just that
> we'd better wait a bit and let it soak in master before forwarding it to stable?
> 

With NFS and SMB, oplocks/leases/delegations are optimizations and
you're never guaranteed to get one in the face of competing access.

stable-kernel-rules.rst says:

- It must fix a problem that causes a build error (but not for
things marked CONFIG_BROKEN), an oops, a hang, data corruption, a real
security issue, or some "oh, that's not good" issue.  In short,
something critical.

I'm not sure this clears that bar.
-- 
Jeff Layton <jlayton@kernel.org>