Re: [PATCH v2 3/6] ntfs: Use zero_user_segment() in handle_bounds_compressed_page()

[Usama Arif <usama.arif@linux.dev>]

On Mon,  8 Jun 2026 22:06:13 +0100 "Matthew Wilcox (Oracle)" <willy@infradead.org> wrote:

> This fixes handle_bounds_compressed_page() on highmem memory
> as page_address() does not work on memory which has been kmap_local(),
> only on kmap() memory.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>  fs/ntfs/compress.c | 18 ++++++++----------
>  1 file changed, 8 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/ntfs/compress.c b/fs/ntfs/compress.c
> index b279f38636d6..89067fecf5a0 100644
> --- a/fs/ntfs/compress.c
> +++ b/fs/ntfs/compress.c
> @@ -108,16 +108,16 @@ static inline void handle_bounds_compressed_page(struct page *page,
>  	loff_t pos = page_offset(page);
>  
>  	if ((pos >= initialized_size) && (initialized_size < i_size)) {
> -		u8 *kp = page_address(page);
> -		unsigned int kp_ofs;
> +		size_t offset;
>  
>  		ntfs_debug("Zeroing page region outside initialized size.");
> -		if (pos >= initialized_size) {
> -			clear_page(kp);
> -			return;
> -		}
> -		kp_ofs = initialized_size & ~PAGE_MASK;
> -		memset(kp + kp_ofs, 0, PAGE_SIZE - kp_ofs);
> +		if (pos >= initialized_size)
> +			offset = 0;
> +		else
> +			offset = offset_in_page(initialized_size);

Is the else branch over here unreacheable as the outer if statement
already had if ((pos >= initialized_size) &&...


> +		zero_user_segment(page, offset, PAGE_SIZE);
> +	} else {
> +		flush_dcache_page(page);
>  	}
>  }
>  
> @@ -222,7 +222,6 @@ static int ntfs_decompress(struct page *dest_pages[], int completed_pages[],
>  				 */
>  				handle_bounds_compressed_page(dp, i_size,
>  						initialized_size);
> -				flush_dcache_page(dp);
>  				kunmap_local(page_address(dp));
>  				SetPageUptodate(dp);
>  				unlock_page(dp);
> @@ -758,7 +757,6 @@ int ntfs_read_compressed_block(struct folio *folio)
>  				 */
>  				handle_bounds_compressed_page(page, i_size,
>  						initialized_size);
> -				flush_dcache_page(page);
>  				kunmap_local(page_address(page));
>  				SetPageUptodate(page);
>  				unlock_page(page);
> -- 
> 2.47.3
> 
>