From: "J. Bruce Fields" <bfields@fieldses.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Jeff Layton <jlayton@redhat.com>,
y2038 Mailman List <y2038@lists.linaro.org>,
Deepa Dinamani <deepa.kernel@gmail.com>,
Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
Trond Myklebust <trond.myklebust@primarydata.com>,
NeilBrown <neilb@suse.com>, Kinglong Mee <kinglongmee@gmail.com>,
linux-nfs@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] nfds: avoid gettimeofday for nfssvc_boot time
Date: Fri, 20 Oct 2017 15:19:35 -0400 [thread overview]
Message-ID: <20171020191935.GE15211@fieldses.org> (raw)
In-Reply-To: <CAK8P3a0K0FcepYtxw-6sct0b5ZTx4b+TW9bF9uqL5HV_M03H-w@mail.gmail.com>
On Thu, Oct 19, 2017 at 01:04:35PM +0200, Arnd Bergmann wrote:
> On Thu, Oct 19, 2017 at 12:54 PM, Jeff Layton <jlayton@redhat.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:
It might reduce the chances of a collision if someone is doing extreme
boot-time optimization, or if time goes backwards for some reason?
> 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.
Anyway, no objection to doing this differently if someone wants, but
I'll just take this patch for now.
Thanks.--b.
>
> > Reviewed-by: Jeff Layton <jlayton@redhat.com>
>
> Thanks.
>
> Arnd
prev parent reply other threads:[~2017-10-20 19:19 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-19 10:04 [PATCH] nfds: avoid gettimeofday for nfssvc_boot time Arnd Bergmann
2017-10-19 10:54 ` Jeff Layton
2017-10-19 11:04 ` Arnd Bergmann
2017-10-20 19:19 ` J. Bruce Fields [this message]
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