RDMA/rxe: Use for_each_sg_page iterator on umem SGL

The driver walks the umem SGL assuming a 1:1 mapping between SGE and
system page. Update to use the for_each_sg_page iterator to get individual
pages contained in the SGEs.  This is a pre-requisite before adding page
combining into SGEs while building the scatter table in IB core.

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>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/sw/rxe/rxe_mr.c

@@ -162,11 +162,10 @@ int rxe_mem_init_user(struct rxe_pd *pd, u64 start,
 		      u64 length, u64 iova, int access, struct ib_udata *udata,
 		      struct rxe_mem *mem)
 {
-	int			entry;
 	struct rxe_map		**map;
 	struct rxe_phys_buf	*buf = NULL;
 	struct ib_umem		*umem;
-	struct scatterlist	*sg;
+	struct sg_page_iter	sg_iter;
 	int			num_buf;
 	void			*vaddr;
 	int err;
@@ -191,16 +190,16 @@ int rxe_mem_init_user(struct rxe_pd *pd, u64 start,
 		goto err1;
 	}
 
-	mem->page_shift		= umem->page_shift;
-	mem->page_mask		= BIT(umem->page_shift) - 1;
+	mem->page_shift		= PAGE_SHIFT;
+	mem->page_mask = PAGE_SIZE - 1;
 
 	num_buf			= 0;
 	map			= mem->map;
 	if (length > 0) {
 		buf = map[0]->buf;
 
-		for_each_sg(umem->sg_head.sgl, sg, umem->nmap, entry) {
-			vaddr = page_address(sg_page(sg));
+		for_each_sg_page(umem->sg_head.sgl, &sg_iter, umem->nmap, 0) {
+			vaddr = page_address(sg_page_iter_page(&sg_iter));
 			if (!vaddr) {
 				pr_warn("null vaddr\n");
 				err = -ENOMEM;
@@ -208,7 +207,7 @@ int rxe_mem_init_user(struct rxe_pd *pd, u64 start,
 			}
 
 			buf->addr = (uintptr_t)vaddr;
-			buf->size = BIT(umem->page_shift);
+			buf->size = PAGE_SIZE;
 			num_buf++;
 			buf++;