[PATCH v3 2/3] block: move dif_prepare/dif_complete functions to block layer

[hch@lst.de (Christoph Hellwig)]

> +			pmap = kmap_atomic(iv.bv_page) + iv.bv_offset;
> +			p = pmap;

Maybe:

			pmap = p = kmap_atomic(iv.bv_page) + iv.bv_offset;

> +			for (j = 0; j < iv.bv_len; j += tuple_sz) {
> +				pi = (struct t10_pi_tuple *)p;

No need for the cast, also the pi declaration can be moved into the
inner scope:

				struct t10_pi_tuple *pi = p;

> +			pmap = kmap_atomic(iv.bv_page) + iv.bv_offset;
> +			p = pmap;
> +			for (j = 0; j < iv.bv_len; j += tuple_sz) {
> +				if (intervals == 0) {
> +					kunmap_atomic(pmap);
> +					return;
> +				}
> +				pi = (struct t10_pi_tuple *)p;

Same here.

Also the intervals check would make sense in the for loop I think, e.g.:

			pmap = p = kmap_atomic(iv.bv_page) + iv.bv_offset;
			for (j = 0; j < iv.bv_len && intervals; j += tuple_sz) {
				struct t10_pi_tuple *pi = p;