Received-SPF: pass (google.com: best guess record for domain of linux-nfs-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <20191124193145.22945-1-amir73il@gmail.com> <20191125164625.GB28608@fieldses.org>
In-Reply-To: <20191125164625.GB28608@fieldses.org>
From:   Deepa Dinamani <deepa.kernel@gmail.com>
Date:   Mon, 25 Nov 2019 10:16:57 -0800
Message-ID: <CABeXuvo3pToaexO26JarHHkQBWO9355YEyO=NeZh-36KciJu6Q@mail.gmail.com>
Subject: Re: [PATCH] utimes: Clamp the timestamps in notify_change()
To:     "J . Bruce Fields" <bfields@fieldses.org>
Cc:     Amir Goldstein <amir73il@gmail.com>, Arnd Bergmann <arnd@arndb.de>,
        Jeff Layton <jlayton@kernel.org>,
        Miklos Szeredi <miklos@szeredi.hu>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
        overlayfs <linux-unionfs@vger.kernel.org>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        y2038 Mailman List <y2038@lists.linaro.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-nfs-owner@vger.kernel.org
Precedence: bulk

On Mon, Nov 25, 2019 at 8:46 AM J . Bruce Fields <bfields@fieldses.org> wrote:
>
> On Sun, Nov 24, 2019 at 09:31:45PM +0200, Amir Goldstein wrote:
> > Push clamping timestamps down the call stack into notify_change(), so
> > in-kernel callers like nfsd and overlayfs will get similar timestamp
> > set behavior as utimes.
>
> So, nfsd has always bypassed timestamp_truncate() and we've never
> noticed till now?  What are the symptoms?  (Do timestamps go backwards
> after cache eviction on filesystems with large time granularity?)
>
> Looks like generic/402 has never run in my tests:
>
>         generic/402     [not run] no kernel support for y2038 sysfs switch

You need this in your xfstest:
https://patchwork.kernel.org/patch/11049745/ . The test has been
updated recently.

And, you need a change like for overlayfs as Amir pointed out.

-Deepa