linux-kernel - Re: [PATCH 09/10] fs: ceph: Replace CURRENT_TIME by ktime_get_real

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Message-ID: <4400939.hfiB5KsmnG@wuerfel>
Date:	Thu, 04 Feb 2016 09:30:20 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	"Yan, Zheng" <zyan@...hat.com>
Cc:	Deepa Dinamani <deepa.kernel@...il.com>,
	Zheng Yan <ukernel@...il.com>, linux-fsdevel@...r.kernel.org,
	y2038@...ts.linaro.org, Dave Chinner <david@...morbit.com>,
	Theodore Ts'o <tytso@....edu>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Sage Weil <sage@...hat.com>, Ilya Dryomov <idryomov@...il.com>,
	ceph-devel <ceph-devel@...r.kernel.org>
Subject: Re: [PATCH 09/10] fs: ceph: Replace CURRENT_TIME by ktime_get_real_ts()

On Thursday 04 February 2016 10:00:19 Yan, Zheng wrote:
> > On Feb 4, 2016, at 05:27, Arnd Bergmann <arnd@...db.de> wrote:
> {
>           struct ceph_timespec ts;
>           ceph_encode_timespec(&ts, &req->r_stamp);
>           ceph_encode_copy(&p, &ts, sizeof(ts));
> }

Ok, that does make the behavior consistent on all architectures, but
leads to a different question:

struct ceph_timespec {
        __le32 tv_sec;
        __le32 tv_nsec;
} __attribute__ ((packed));

How do you define ceph_timespec, is tv_sec supposed to be signed or unsigned?

It seems that you treat it as signed, meaning you interpret times
from the server as being in the [1902..2038] range, rather than the
[1970..2106] range:

static inline void ceph_decode_timespec(struct timespec *ts,
                                        const struct ceph_timespec *tv)
{
        ts->tv_sec = (__kernel_time_t)le32_to_cpu(tv->tv_sec);
        ts->tv_nsec = (long)le32_to_cpu(tv->tv_nsec);
}

Is that intentional and documented? If yes, what is your plan to deal
with y2038 support?

	Arnd