Subject: Re: [PATCH v12 3/6] mm/hwpoison: return -EFAULT when copy fail in copy_mc_[user]_highpage()

From: Jonathan Cameron <[email-masked]>
Date: Mon, 19 Aug 2024 12:43:00 +0100

On Tue, 28 May 2024 16:59:12 +0800
Tong Tiangen <[email-masked]> wrote:

> If hardware errors are encountered during page copying, returning the bytes
> not copied is not meaningful, and the caller cannot do any processing on
> the remaining data. Returning -EFAULT is more reasonable, which represents
> a hardware error encountered during the copying.
> 
> Signed-off-by: Tong Tiangen <[email-masked]>

LGTM
Reviewed-by: Jonathan Cameron <[email-masked]>

> ---
>  include/linux/highmem.h | 8 ++++----
>  mm/khugepaged.c         | 4 ++--
>  2 files changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/include/linux/highmem.h b/include/linux/highmem.h
> index 00341b56d291..64a567d5ad6f 100644
> --- a/include/linux/highmem.h
> +++ b/include/linux/highmem.h
> @@ -335,8 +335,8 @@ static inline void copy_highpage(struct page *to, struct page *from)
>  /*
>   * If architecture supports machine check exception handling, define the
>   * #MC versions of copy_user_highpage and copy_highpage. They copy a memory
> - * page with #MC in source page (@from) handled, and return the number
> - * of bytes not copied if there was a #MC, otherwise 0 for success.
> + * page with #MC in source page (@from) handled, and return -EFAULT if there
> + * was a #MC, otherwise 0 for success.
>   */
>  static inline int copy_mc_user_highpage(struct page *to, struct page *from,
>  					unsigned long vaddr, struct vm_area_struct *vma)
> @@ -352,7 +352,7 @@ static inline int copy_mc_user_highpage(struct page *to, struct page *from,
>  	kunmap_local(vto);
>  	kunmap_local(vfrom);
>  
> -	return ret;
> +	return ret ? -EFAULT : 0;
>  }
>  
>  static inline int copy_mc_highpage(struct page *to, struct page *from)
> @@ -368,7 +368,7 @@ static inline int copy_mc_highpage(struct page *to, struct page *from)
>  	kunmap_local(vto);
>  	kunmap_local(vfrom);
>  
> -	return ret;
> +	return ret ? -EFAULT : 0;
>  }
>  #else
>  static inline int copy_mc_user_highpage(struct page *to, struct page *from,
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 774a97e6e2da..cce838e85967 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -798,7 +798,7 @@ static int __collapse_huge_page_copy(pte_t *pte, struct folio *folio,
>  			continue;
>  		}
>  		src_page = pte_page(pteval);
> -		if (copy_mc_user_highpage(page, src_page, src_addr, vma) > 0) {
> +		if (copy_mc_user_highpage(page, src_page, src_addr, vma)) {
>  			result = SCAN_COPY_MC;
>  			break;
>  		}
> @@ -2042,7 +2042,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
>  			index++;
>  			dst++;
>  		}
> -		if (copy_mc_highpage(dst, folio_page(folio, 0)) > 0) {
> +		if (copy_mc_highpage(dst, folio_page(folio, 0))) {
>  			result = SCAN_COPY_MC;
>  			goto rollback;
>  		}