Re: [PATCH v2 06/12] dax: advance the iomap_iter on zero range

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

On Wed, Feb 19, 2025 at 12:50:44PM -0500, Brian Foster wrote:
> Update the DAX zero range iomap iter handler to advance the iter
> directly. Advance by the full length in the hole/unwritten case, or
> otherwise advance incrementally in the zeroing loop. In either case,
> return 0 or an error code for success or failure.
> 
> Signed-off-by: Brian Foster <bfoster@redhat.com>

Pretty straightforward
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
>  fs/dax.c | 33 +++++++++++++++++----------------
>  1 file changed, 17 insertions(+), 16 deletions(-)
> 
> diff --git a/fs/dax.c b/fs/dax.c
> index 139e299e53e6..f4d8c8c10086 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -1358,13 +1358,12 @@ static s64 dax_zero_iter(struct iomap_iter *iter, bool *did_zero)
>  {
>  	const struct iomap *iomap = &iter->iomap;
>  	const struct iomap *srcmap = iomap_iter_srcmap(iter);
> -	loff_t pos = iter->pos;
>  	u64 length = iomap_length(iter);
> -	s64 written = 0;
> +	s64 ret;
>  
>  	/* already zeroed?  we're done. */
>  	if (srcmap->type == IOMAP_HOLE || srcmap->type == IOMAP_UNWRITTEN)
> -		return length;
> +		return iomap_iter_advance(iter, &length);
>  
>  	/*
>  	 * invalidate the pages whose sharing state is to be changed
> @@ -1372,33 +1371,35 @@ static s64 dax_zero_iter(struct iomap_iter *iter, bool *did_zero)
>  	 */
>  	if (iomap->flags & IOMAP_F_SHARED)
>  		invalidate_inode_pages2_range(iter->inode->i_mapping,
> -					      pos >> PAGE_SHIFT,
> -					      (pos + length - 1) >> PAGE_SHIFT);
> +				iter->pos >> PAGE_SHIFT,
> +				(iter->pos + length - 1) >> PAGE_SHIFT);
>  
>  	do {
> +		loff_t pos = iter->pos;
>  		unsigned offset = offset_in_page(pos);
> -		unsigned size = min_t(u64, PAGE_SIZE - offset, length);
>  		pgoff_t pgoff = dax_iomap_pgoff(iomap, pos);
> -		long rc;
>  		int id;
>  
> +		length = min_t(u64, PAGE_SIZE - offset, length);
> +
>  		id = dax_read_lock();
> -		if (IS_ALIGNED(pos, PAGE_SIZE) && size == PAGE_SIZE)
> -			rc = dax_zero_page_range(iomap->dax_dev, pgoff, 1);
> +		if (IS_ALIGNED(pos, PAGE_SIZE) && length == PAGE_SIZE)
> +			ret = dax_zero_page_range(iomap->dax_dev, pgoff, 1);
>  		else
> -			rc = dax_memzero(iter, pos, size);
> +			ret = dax_memzero(iter, pos, length);
>  		dax_read_unlock(id);
>  
> -		if (rc < 0)
> -			return rc;
> -		pos += size;
> -		length -= size;
> -		written += size;
> +		if (ret < 0)
> +			return ret;
> +
> +		ret = iomap_iter_advance(iter, &length);
> +		if (ret)
> +			return ret;
>  	} while (length > 0);
>  
>  	if (did_zero)
>  		*did_zero = true;
> -	return written;
> +	return ret;
>  }
>  
>  int dax_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
> -- 
> 2.48.1
> 
>