Re: [PATCH 3/3] block,iov_iter: move bio_iov_iter_align_down into iov_iter_extract_bvecs

[Keith Busch <kbusch@kernel.org>]

On Tue, Jul 14, 2026 at 03:12:00PM +0200, Christoph Hellwig wrote:
>  ssize_t iov_iter_extract_bvecs(struct iov_iter *iter, struct bio_vec *bv,
>  		size_t max_size, unsigned short *nr_vecs,
>  		unsigned short max_vecs, unsigned mem_align_mask,
> -		iov_iter_extraction_t extraction_flags)
> +		unsigned len_align_mask, iov_iter_extraction_t extraction_flags)
>  {
>  	unsigned long start = (unsigned long)iter_iov_addr(iter);
>  	unsigned short entries_left = max_vecs - *nr_vecs;
> @@ -1960,11 +1991,13 @@ ssize_t iov_iter_extract_bvecs(struct iov_iter *iter, struct bio_vec *bv,
>  		offset = 0;
>  	}
>  
> +	size -= left;
>  	iov_iter_revert(iter, left);
>  	if (iov_iter_extract_will_pin(iter)) {
>  		while (i < nr_pages)
>  			unpin_user_page(pages[i++]);
>  	}
> -	return size - left;
> +
> +	return bvec_iter_align_down(iter, bv, size, nr_vecs, len_align_mask);

I don't think we can do this alignment inline with building the bio_vec.
The len_align_mask is usually the logical block size. We can submit
sub-sector sized vectors so aligning down after extracting such a vector
will result in a zero size for that iteration.