linux-kernel - Re: [PATCH] cachefiles: avoid deprecated get

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Message-ID: <CAK8P3a06uP18jei=b3Hwdoe21f3gM6K5j2129Ra5CdVx5aKh6g@mail.gmail.com>
Date:   Wed, 20 Jun 2018 14:03:40 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     David Howells <dhowells@...hat.com>
Cc:     y2038 Mailman List <y2038@...ts.linaro.org>,
        linux-cachefs@...hat.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cachefiles: avoid deprecated get_seconds()

On Wed, Jun 20, 2018 at 12:58 PM, David Howells <dhowells@...hat.com> wrote:
> Arnd Bergmann <arnd@...db.de> wrote:
>
>> -     sprintf(nbuffer, "%08x%08x",
>> -             (uint32_t) get_seconds(),
>> +     sprintf(nbuffer, "%08llx%08x",
>> +             (uint64_t) ktime_get_real_seconds(),
>
> It's not necessary to expand the 'time' field of the name.  It's not
> interpreted by userspace, it's just there to prevent collisions when moving
> directories about.  If your cache goes weird in the future because there was a
> collision with an object that was moved to the graveyard 68 years ago and not
> cleaned up, then that's probably a bug in cachefilesd.
>
> But I've no objection to using ktime_get_real_seconds() and truncating the
> value.

Ok, fair enough. I was mainly worried about what might happen when the
file names stop being strictly sorted in numerical order by their creation
time. If that is not a problem, I'll send the simpler patch to use
lower_32_bits(ktime_get_real_seconds()) for clarity.

       Arnd