Re: [PATCH v2 16/51] block: bounce: avoid direct access to bvec table

[Matthew Wilcox]

On Mon, Jun 26, 2017 at 08:09:59PM +0800, Ming Lei wrote:
>  	bio_for_each_segment_all(bvec, bio, i) {
> -		org_vec = bio_orig->bi_io_vec + i + start;
> -
> -		if (bvec->bv_page == org_vec->bv_page)
> -			continue;
> +		orig_vec = bio_iter_iovec(bio_orig, orig_iter);
> +		if (bvec->bv_page == orig_vec.bv_page)
> +			goto next;
>  
>  		dec_zone_page_state(bvec->bv_page, NR_BOUNCE);
>  		mempool_free(bvec->bv_page, pool);
> + next:
> +		bio_advance_iter(bio_orig, &orig_iter, orig_vec.bv_len);
>  	}
>  

I think this might be written more clearly as:

 	bio_for_each_segment_all(bvec, bio, i) {
		orig_vec = bio_iter_iovec(bio_orig, orig_iter);
		if (bvec->bv_page != orig_vec.bv_page) {
 			dec_zone_page_state(bvec->bv_page, NR_BOUNCE);
	 		mempool_free(bvec->bv_page, pool);
		}
		bio_advance_iter(bio_orig, &orig_iter, orig_vec.bv_len);
 	}

What do you think?