Re: [PATCH v5 1/6] userfaultfd: convert mfill_atomic_pte_copy() to use a folio

[Mike Kravetz]

On 03/31/23 17:39, Peng Zhang wrote:
> From: ZhangPeng <zhangpeng362@xxxxxxxxxx>
> 
> Call vma_alloc_folio() directly instead of alloc_page_vma() and convert
> page_kaddr to kaddr in mfill_atomic_pte_copy(). Removes several calls to
> compound_head().
> 
> Signed-off-by: ZhangPeng <zhangpeng362@xxxxxxxxxx>
> Reviewed-by: Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx>
> ---
>  mm/userfaultfd.c | 33 +++++++++++++++++----------------
>  1 file changed, 17 insertions(+), 16 deletions(-)

Looks good,

Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>

>  	} else {
> -		page = *pagep;
> +		folio = page_folio(*pagep);
> +		VM_BUG_ON_FOLIO(folio_test_large(folio), folio);
>  		*pagep = NULL;
>  	}

However, I am still unsure about the reason for adding the VM_BUG_ON_FOLIO
here.
-- 
Mike Kravetz