Re: [PATCH 19/20] pstore: fs superblock limits

[Deepa Dinamani]

On Tue, Jul 30, 2019 at 12:36 AM Arnd Bergmann <arnd@xxxxxxxx> wrote:
>
> On Tue, Jul 30, 2019 at 6:31 AM Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> >
> > On Mon, Jul 29, 2019 at 06:49:23PM -0700, Deepa Dinamani wrote:
> > > Also update the gran since pstore has microsecond granularity.
> >
> > So, I'm fine with this, but technically the granularity depends on the
> > backend storage... many have no actual time keeping, though. My point is,
> > pstore's timestamps are really mostly a lie, but the most common backend
> > (ramoops) is seconds-granularity.
> >
> > So, I'm fine with this, but it's a lie but it's a lie that doesn't
> > matter, so ...
> >
> > Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
> >
> > I'm open to suggestions to improve it...
>
> If we don't care about using sub-second granularity, then setting it
> to one second unconditionally here will make it always use that and
> report it correctly.

Should this printf in ramoops_write_kmsg_hdr() also be fixed then?

        RAMOOPS_KERNMSG_HDR "%lld.%06lu-%c\n",
        (time64_t)record->time.tv_sec,
        record->time.tv_nsec / 1000,
        record->compressed ? 'C' : 'D');
    persistent_ram_write(prz, hdr, len);

ramoops_read_kmsg_hdr() doesn't read this as microseconds. Seems like
a mismatch from above.

If we want to agree that we just want seconds granularity for pstore,
we could replace the tv_nsec part to be all 0's if anybody else is
depending on this format.
I could drop this patch from the series and post that patch seperately.

Thanks,
-Deepa