Re: deconflicting new syscall numbers for 6.11

Linus Torvalds
2024-07-06T02:56:23Z

On Fri, 5 Jul 2024 at 19:10, Jason A. Donenfeld <Jason@zx2c4.com> wrote:
>
> https://git.zx2c4.com/linux-rng/log/

So we already expose VM_WIPEONFORK and VM_DONTDUMP using madvise().
Exposing them at mmap creation time with MMAP_xyz sounds fine.

However, I do note that both the pre-existing VM_WIPEONFORK - and the
new VM_DROPPABLE - needs to be limited to anonymous private mappings
only.

You did that for VM_DROPPABLE, but not for VM_WIPEONFORK.

Now, admittedly I don't remember *why* we made VM_WIPEONFORK only work
for private mappings, but that's what we did.

Anyway, that patch looks largely fine to me apart from that note, but
I do think you want to check it with the mm people on linux-mm.

> The selftest code is the largest part of it. There's no more syscall. I
> think it should be much more to your liking and seems like an alright
> set of compromises. Hopefully that's a bit closer to the mark.

From a "look through the patches" standpoint, this did look more
palatable to me, but I also would have had an easier time with looking
at the patches if the self-tests were separate commits.

Linus