Re: [RFC][PATCH 10/13] get rid of audit_reusename()

Mateusz Guzik
2025-11-09T22:33:17Z

On Sun, Nov 9, 2025 at 11:29 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Sun, 9 Nov 2025 at 14:18, Mateusz Guzik <mjguzik@gmail.com> wrote:
> >
> > You would need 256 bytes to cover almost all of this.
>
> Why would you care to cover all of that?
>
> Your very numbers show that 128 bytes covers 97+% of all cases (and
> 160 bytes is at 99.8%)
>
> The other cases need to be *correct*, of course, but not necessarily
> optimized for.
>
> If we can do 97% of all filenames with a simple on-stack allocation,
> that would be a huge win.
>
> (In fact, 64 bytes covers 90% of the cases according to your numbers).
>

The programs which pass in these "too long" names just keep doing it,
meaning with a stack-based scheme which forces an extra SMAP trip
means they are permanently shafted. It's not that only a small % of
their lookups is penalized.

However, now that I wrote, I figured one could create a trivial
heuristic: if a given process had too many long names in a row, switch
to go directly to kmem going forward? Reset the flag on exec.