linux-kernel - Re: [Y2038] [PATCH] vfs: replace current_kernel

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Date:   Tue, 26 Jun 2018 18:08:01 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Dave Chinner <david@...morbit.com>
Cc:     Jens Axboe <axboe@...nel.dk>, Jan Kara <jack@...e.cz>,
        Jeff Layton <jlayton@...hat.com>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        y2038 Mailman List <y2038@...ts.linaro.org>,
        Brian Foster <bfoster@...hat.com>,
        Miklos Szeredi <miklos@...redi.hu>,
        Pavel Tatashin <pasha.tatashin@...cle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andi Kleen <andi.kleen@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Deepa Dinamani <deepa.kernel@...il.com>
Subject: Re: [Y2038] [PATCH] vfs: replace current_kernel_time64 with ktime equivalent

On Tue, Jun 26, 2018 at 2:24 AM, Dave Chinner <david@...morbit.com> wrote:
> On Fri, Jun 22, 2018 at 03:24:48PM +0200, Arnd Bergmann wrote:
>> On Thu, Jun 21, 2018 at 10:23 PM, Dave Chinner <david@...morbit.com> wrote:
>> > On Wed, Jun 20, 2018 at 05:01:24PM +0200, Arnd Bergmann wrote:

>> You definitely have a point about the documentation. I meant to
>> fix that as part of the recent rework of the timekeeping.h header
>> but haven't finished it, partly because the header is still being
>> changed as we get rid of the older interfaces.
>
> The interface documentation should be introduced with the new
> interfaces, not left for later as that leaves people like me with no
> fucking clue about what the changes actually mean or why they are
> being done.  Perhaps you'd have done better to explain this API as
> an internal implementation of clock_gettime(CLOCK_REALTIME_COARSE),
> which is clearly documented in the man page as:
>
> "Use when you need very fast, but not fine-grained timestamps."
>
> Put that comment on ktime_get_coarse_real_ts64(), and almost all the
> questions about "WTF does this whacky function do?" go away....

I've tried to come up with a coherent documentation now and sent a
patch for that. For this version, I ended up not documenting each of the
ktime_get() functions separately but instead added a new file in the
core-api documentation and a reference to that from the header. This
seemed easier to understand than duplicating the same text for over
30 very similar interfaces.

       Arnd