[RFC v2 04/11] block: introduce dma token backed bio type

[Anuj gupta]

> @@ -328,6 +328,29 @@ int bio_split_io_at(struct bio *bio, const struct queue_limits *lim,
>         unsigned nsegs = 0, bytes = 0, gaps = 0;
>         struct bvec_iter iter;
>
> +       if (bio_flagged(bio, BIO_DMA_TOKEN)) {
> +               int offset = offset_in_page(bio->bi_iter.bi_bvec_done);
> +
> +               nsegs = ALIGN(bio->bi_iter.bi_size + offset, PAGE_SIZE);
> +               nsegs >>= PAGE_SHIFT;
> +
> +               if (offset & lim->dma_alignment || bytes & len_align_mask)
> +                       return -EINVAL;

bytes == 0 is a dead check here. Probably you would like to check the
length of the first and last segment to match with what the normal path
below is doing.