RDMA/cxgb3: Use for_each_sg_dma_page iterator on umem SGL

Use the for_each_sg_dma_page iterator variant to walk the umem DMA-mapped
SGL and get the page DMA address. This avoids the extra loop to iterate
pages in the SGE when for_each_sg iterator is used.

Additionally, purge umem->page_shift usage in the driver as its only
relevant for ODP MRs. Use system page size and shift instead.
Signed-off-by: Shiraz, Saleem <shiraz.saleem@intel.com>
Acked-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/cxgb3/iwch_provider.c

@@ -516,14 +516,13 @@ static struct ib_mr *iwch_reg_user_mr(struct ib_pd *pd, u64 start, u64 length,
 				      u64 virt, int acc, struct ib_udata *udata)
 {
 	__be64 *pages;
-	int shift, n, len;
-	int i, k, entry;
+	int shift, n, i;
 	int err = 0;
 	struct iwch_dev *rhp;
 	struct iwch_pd *php;
 	struct iwch_mr *mhp;
 	struct iwch_reg_user_mr_resp uresp;
-	struct scatterlist *sg;
+	struct sg_dma_page_iter sg_iter;
 	pr_debug("%s ib_pd %p\n", __func__, pd);
 
 	php = to_iwch_pd(pd);
@@ -541,7 +540,7 @@ static struct ib_mr *iwch_reg_user_mr(struct ib_pd *pd, u64 start, u64 length,
 		return ERR_PTR(err);
 	}
 
-	shift = mhp->umem->page_shift;
+	shift = PAGE_SHIFT;
 
 	n = mhp->umem->nmap;
 
@@ -557,19 +556,15 @@ static struct ib_mr *iwch_reg_user_mr(struct ib_pd *pd, u64 start, u64 length,
 
 	i = n = 0;
 
-	for_each_sg(mhp->umem->sg_head.sgl, sg, mhp->umem->nmap, entry) {
-			len = sg_dma_len(sg) >> shift;
-			for (k = 0; k < len; ++k) {
-				pages[i++] = cpu_to_be64(sg_dma_address(sg) +
-							 (k << shift));
-				if (i == PAGE_SIZE / sizeof *pages) {
-					err = iwch_write_pbl(mhp, pages, i, n);
-					if (err)
-						goto pbl_done;
-					n += i;
-					i = 0;
-				}
-			}
+	for_each_sg_dma_page(mhp->umem->sg_head.sgl, &sg_iter, mhp->umem->nmap, 0) {
+		pages[i++] = cpu_to_be64(sg_page_iter_dma_address(&sg_iter));
+		if (i == PAGE_SIZE / sizeof *pages) {
+			err = iwch_write_pbl(mhp, pages, i, n);
+			if (err)
+				goto pbl_done;
+			n += i;
+			i = 0;
+		}
 	}
 
 	if (i)