On Mon, Apr 08, 2019 at 12:46:37PM +0200, Christoph Hellwig wrote:
> The offset in scatterlists is allowed to be larger than the page size,
> so don't go to great length to avoid that case and simplify the
> arithmetics.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> block/blk-merge.c | 21 ++++++---------------
> 1 file changed, 6 insertions(+), 15 deletions(-)
>
> diff --git a/block/blk-merge.c b/block/blk-merge.c
> index 8f96d683b577..52dbdd089fdf 100644
> --- a/block/blk-merge.c
> +++ b/block/blk-merge.c
> @@ -467,26 +467,17 @@ static unsigned blk_bvec_map_sg(struct request_queue *q,
> struct scatterlist **sg)
> {
> unsigned nbytes = bvec->bv_len;
> - unsigned nsegs = 0, total = 0, offset = 0;
> + unsigned nsegs = 0, total = 0;
>
> while (nbytes > 0) {
> - unsigned seg_size;
> - struct page *pg;
> - unsigned idx;
> + unsigned offset = bvec->bv_offset + total;
> + unsigned len = min(get_max_segment_size(q, offset), nbytes);
>
> *sg = blk_next_sg(sg, sglist);
> + sg_set_page(*sg, bvec->bv_page, len, offset);
>
> - seg_size = get_max_segment_size(q, bvec->bv_offset + total);
> - seg_size = min(nbytes, seg_size);
> -
> - offset = (total + bvec->bv_offset) % PAGE_SIZE;
> - idx = (total + bvec->bv_offset) / PAGE_SIZE;
> - pg = bvec_nth_page(bvec->bv_page, idx);
> -
> - sg_set_page(*sg, pg, seg_size, offset);
> -
> - total += seg_size;
> - nbytes -= seg_size;
> + total += len;
> + nbytes -= len;
> nsegs++;
> }
Nice cleanup & simplification:
Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>
Thanks,
Ming
