Re: [PATCH 07/10] iomap: Use folio_next_pos()

["Darrick J. Wong" <djwong@kernel.org>]

On Fri, Oct 24, 2025 at 06:08:15PM +0100, Matthew Wilcox (Oracle) wrote:
> This is one instruction more efficient than open-coding folio_pos() +
> folio_size().  It's the equivalent of (x + y) << z rather than
> x << z + y << z.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> Cc: Christian Brauner <brauner@kernel.org>
> Cc: "Darrick J. Wong" <djwong@kernel.org>
> Cc: linux-xfs@vger.kernel.org

Looks like a nice win, even if a small one
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
>  fs/iomap/buffered-io.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index 8b847a1e27f1..32a27f36372d 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -707,7 +707,7 @@ static int __iomap_write_begin(const struct iomap_iter *iter,
>  	 * are not changing pagecache contents.
>  	 */
>  	if (!(iter->flags & IOMAP_UNSHARE) && pos <= folio_pos(folio) &&
> -	    pos + len >= folio_pos(folio) + folio_size(folio))
> +	    pos + len >= folio_next_pos(folio))
>  		return 0;
>  
>  	ifs = ifs_alloc(iter->inode, folio, iter->flags);
> @@ -1097,8 +1097,7 @@ static void iomap_write_delalloc_ifs_punch(struct inode *inode,
>  	if (!ifs)
>  		return;
>  
> -	last_byte = min_t(loff_t, end_byte - 1,
> -			folio_pos(folio) + folio_size(folio) - 1);
> +	last_byte = min_t(loff_t, end_byte - 1, folio_next_pos(folio) - 1);
>  	first_blk = offset_in_folio(folio, start_byte) >> blkbits;
>  	last_blk = offset_in_folio(folio, last_byte) >> blkbits;
>  	for (i = first_blk; i <= last_blk; i++) {
> @@ -1129,8 +1128,7 @@ static void iomap_write_delalloc_punch(struct inode *inode, struct folio *folio,
>  	 * Make sure the next punch start is correctly bound to
>  	 * the end of this data range, not the end of the folio.
>  	 */
> -	*punch_start_byte = min_t(loff_t, end_byte,
> -				folio_pos(folio) + folio_size(folio));
> +	*punch_start_byte = min_t(loff_t, end_byte, folio_next_pos(folio));
>  }
>  
>  /*
> @@ -1170,7 +1168,7 @@ static void iomap_write_delalloc_scan(struct inode *inode,
>  				start_byte, end_byte, iomap, punch);
>  
>  		/* move offset to start of next folio in range */
> -		start_byte = folio_pos(folio) + folio_size(folio);
> +		start_byte = folio_next_pos(folio);
>  		folio_unlock(folio);
>  		folio_put(folio);
>  	}
> -- 
> 2.47.2
>