linux-kernel - Re: [PATCH] nfds: avoid gettimeofday for nfssvc

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Message-ID: <CAK8P3a0K0FcepYtxw-6sct0b5ZTx4b+TW9bF9uqL5HV_M03H-w@mail.gmail.com>
Date:   Thu, 19 Oct 2017 13:04:35 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Jeff Layton <jlayton@...hat.com>
Cc:     y2038 Mailman List <y2038@...ts.linaro.org>,
        "J. Bruce Fields" <bfields@...ldses.org>,
        Deepa Dinamani <deepa.kernel@...il.com>,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        Trond Myklebust <trond.myklebust@...marydata.com>,
        NeilBrown <neilb@...e.com>, Kinglong Mee <kinglongmee@...il.com>,
        linux-nfs@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] nfds: avoid gettimeofday for nfssvc_boot time

On Thu, Oct 19, 2017 at 12:54 PM, Jeff Layton <jlayton@...hat.com> wrote:
>
> I wonder if we'd be better off just using nfssvc_boot.tv_sec as the
> verifier? I don't see us ever calling that ktime_get_real_ts64 more than
> once per second for this purpose, and that would eliminate wraparound.
> That said, wraparound is not a huge concern here anyway, so this is
> certainly fine for now:

I now have the feeling that we had previously had the same discussion
when someone else submitted a similar patch that ended up never getting
merged. I might also be confusing this with a different subsystem that
had the same requirement.

If we want this to be as unique as possible and also never (within
a few hundred years) wrap, we could call ktime_get_real_ns(), which
returns a 64-bit nanoseconds number.

> Reviewed-by: Jeff Layton <jlayton@...hat.com>

Thanks.

     Arnd