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

[Arnd Bergmann]

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. 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