Re: [PATCH] efi: cper: avoid using get_seconds()

[Ard Biesheuvel]

On 18 June 2018 at 17:49, Arnd Bergmann <arnd@xxxxxxxx> wrote:
> On Mon, Jun 18, 2018 at 5:47 PM, Ard Biesheuvel
> <ard.biesheuvel@xxxxxxxxxx> wrote:
>> On 18 June 2018 at 16:17, Arnd Bergmann <arnd@xxxxxxxx> wrote:
>
>>> -               atomic64_set(&seq, ((u64)get_seconds()) << 32);
>>> +       if (!atomic64_read(&seq)) {
>>> +               time64_t time = ktime_get_real_seconds();
>>> +
>>> +               /*
>>> +                * This code is unlikely to still be needed in year 2106,
>>> +                * but just in case, let's use a few more bits for timestamps
>>> +                * after y2038 to be sure they keep increasing monotonically
>>> +                * for the next few hundred years...
>>> +                */
>>> +               if (time < 0x80000000)
>>> +                       atomic64_set(&seq, (ktime_get_real_seconds()) << 32);
>>> +               else
>>> +                       atomic64_set(&seq, 0x8000000000000000ull |
>>> +                                          ktime_get_real_seconds() << 24);
>>> +       }
>>
>> Given that these values are never decoded and interpreted as
>> timestamps, can't we simply switch to the second flavour immediately?
>
> I considered that, but the downside would be that all future filenames would
> come before all past file names.

Won't we have that same problem in 2038?

> I don't know if the order is important at
> all, but the current implementation at least looks like it's intended to keep
> all file names strictly sorted across boots.
>
>          Arnd