xprtrdma: Recognize XDRBUF_SPARSE_PAGES

Commit 431f6eb3 ("SUNRPC: Add a label for RPC calls that require
allocation on receive") didn't update similar logic in rpc_rdma.c.
I don't think this is a bug, per-se; the commit just adds more
careful checking for broken upper layer behavior.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

net/sunrpc/xprtrdma/rpc_rdma.c

@@ -218,11 +218,12 @@ rpcrdma_convert_iovs(struct rpcrdma_xprt *r_xprt, struct xdr_buf *xdrbuf,
 	ppages = xdrbuf->pages + (xdrbuf->page_base >> PAGE_SHIFT);
 	page_base = offset_in_page(xdrbuf->page_base);
 	while (len) {
-		if (unlikely(!*ppages)) {
-			/* XXX: Certain upper layer operations do
-			 *	not provide receive buffer pages.
-			 */
-			*ppages = alloc_page(GFP_ATOMIC);
+		/* ACL likes to be lazy in allocating pages - ACLs
+		 * are small by default but can get huge.
+		 */
+		if (unlikely(xdrbuf->flags & XDRBUF_SPARSE_PAGES)) {
+			if (!*ppages)
+				*ppages = alloc_page(GFP_ATOMIC);
 			if (!*ppages)
 				return -ENOBUFS;
 		}