Re: [PATCH v2 02/15] userfaultfd: introduce struct mfill_state

David Hildenbrand (Arm)
2026-03-20T12:43:10Z

On 3/6/26 18:18, Mike Rapoport wrote:
> From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
>
> mfill_atomic() passes a lot of parameters down to its callees.
>
> Aggregate them all into mfill_state structure and pass this structure to
> functions that implement various UFFDIO_ commands.
>
> Tracking the state in a structure will allow moving the code that retries
> copying of data for UFFDIO_COPY into mfill_atomic_pte_copy() and make the
> loop in mfill_atomic() identical for all UFFDIO operations on PTE-mapped
> memory.
>
> The mfill_state definition is deliberately local to mm/userfaultfd.c, hence
> shmem_mfill_atomic_pte() is not updated.
>
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---

[...]

> if (fatal_signal_pending(current))
> @@ -866,10 +882,10 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx,
>
> out_unlock:
> up_read(&ctx->map_changing_lock);
> - uffd_mfill_unlock(dst_vma);
> + uffd_mfill_unlock(state.vma);
> out:
> - if (folio)
> - folio_put(folio);
> + if (state.folio)
> + folio_put(state.folio);
> VM_WARN_ON_ONCE(copied < 0);
> VM_WARN_ON_ONCE(err > 0);
> VM_WARN_ON_ONCE(!copied && !err);

I guess, "copied" could be easily avoided by
comparing state.src_addr with start_addr.

Acked-by: David Hildenbrand (Arm) <david@kernel.org>

--
Cheers,

David