Re: [PATCH v3] mm: folio_zero_user: open code range computation in folio_zero_user()

[David Hildenbrand (Arm)]

On 2/6/26 23:38, Ankur Arora wrote:
> riscv64-gcc-linux-gnu (v8.5) reports a compile time assert in:
>
>     r[2] = DEFINE_RANGE(clamp_t(s64, fault_idx - radius, pg.start, pg.end),
>   		       clamp_t(s64, fault_idx + radius, pg.start, pg.end));
>
> where it decides that pg.start > pg.end in:
>    clamp_t(s64, fault_idx + radius, pg.start, pg.end));
>
> where pg comes from:
>    const struct range pg = DEFINE_RANGE(0, folio_nr_pages(folio) - 1);
>
> That does not seem like it could be true. Even for pg.start == pg.end,
> we would need folio_test_large() to evaluate to false at compile time:
>
>    static inline unsigned long folio_nr_pages(const struct folio *folio)
>    {
> 	if (!folio_test_large(folio))
> 		return 1;
> 	return folio_large_nr_pages(folio);
>    }
>
> Workaround by open coding the range computation. Also, simplify the type
> declarations for the relevant variables.
>
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Closes: https://lore.kernel.org/oe-kbuild-all/202601240453.QCjgGdJa-lkp@xxxxxxxxx/
> Fixes: 93552c9a3350 ("mm: folio_zero_user: cache neighbouring pages")
> Signed-off-by: Ankur Arora <ankur.a.arora@xxxxxxxxxx>
> Acked-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>
> ---
>
> Hi Andrew

Thanks Amkur and hoping you'll have a nice weekend!

--
Cheers,

David