Re: [PATCH] mm/memory: refactor finish_fault

[David Hildenbrand (Arm)]

On 6/24/26 12:20, Sarthak Sharma wrote:
> finish_fault() currently has a goto fallback implementation
> where we try to map a large folio with PTEs. If that cannot be
> installed, we goto fallback and go through the fallback mapping
> path again. This looks weird and is tough to comprehend.
> 
> Remove the goto fallback implementation and try to map the
> whole folio if allowed. If the whole folio cannot be mapped,
> fall back to single page mapping without repeating the whole
> function.
> 
> The cleanup of finish_fault() was suggested by David in [1].
> 
> [1] https://lore.kernel.org/all/3684c55a-6581-4731-b94a-19526f455a1e@xxxxxxxxxx/
> 
> Suggested-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>
> Signed-off-by: Sarthak Sharma <sarthak.sharma@xxxxxxx>
> ---
> Tested this patch by running mm selftests on baseline and patched 7.1
> kernels. No regressions were observed.

This goes into the right direction, but I think we can do better.

For example, we know that we always have to fallback to a single PTE with
userfaultfd (incl. not mapping a PMD-sized folio by PMDs).

Let me find some time to play with this myself.

-- 
Cheers,

David