Re: [PATCH v6 14/15] selftests/mm: add userfaultfd RWP tests

[Askar Safin]

"Kiryl Shutsemau (Meta)" <kas@xxxxxxxxxx>:
> +/*
> + * Test that GUP resolves through protnone PTEs (async mode).
> + * vmsplice() into a pipe pins user pages via get_user_pages_fast() --
> + * unlike write(), which goes through copy_from_user() and ordinary
> + * hardware page faults -- so it exercises gup_can_follow_protnone() on
> + * the RW-protected PTE. In async mode the kernel auto-restores
> + * permissions and GUP returns the page.
> + */

Note that I recently submitted a patch, which makes vmsplice equivalent to
preadv2/pwritev2, and it was accepted to next.

For now it is just an experiment, it is possible it will be reverted.

https://lore.kernel.org/all/20260601-aufweichen-dissens-ausrechnen-0d9b84728113@brauner/

-- 
Askar Safin