rds: refactor zcopy code into rds_message_zcopy_from_user

Move the large block of code predicated on zcopy from
rds_message_copy_from_user into a new function,
rds_message_zcopy_from_user()
Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/rds/message.c

@@ -333,14 +333,14 @@ struct rds_message *rds_message_map_pages(unsigned long *page_addrs, unsigned in
 	return rm;
 }
 
-int rds_message_copy_from_user(struct rds_message *rm, struct iov_iter *from,
-			       bool zcopy)
+int rds_message_zcopy_from_user(struct rds_message *rm, struct iov_iter *from)
 {
-	unsigned long to_copy, nbytes;
 	unsigned long sg_off;
 	struct scatterlist *sg;
 	int ret = 0;
 	int length = iov_iter_count(from);
+	int total_copied = 0;
+	struct sk_buff *skb;
 
 	rm->m_inc.i_hdr.h_len = cpu_to_be32(iov_iter_count(from));
 
@@ -350,15 +350,10 @@ int rds_message_copy_from_user(struct rds_message *rm, struct iov_iter *from,
 	sg = rm->data.op_sg;
 	sg_off = 0; /* Dear gcc, sg->page will be null from kzalloc. */
 
-	if (zcopy) {
-		int total_copied = 0;
-		struct sk_buff *skb;
-
 	skb = alloc_skb(0, GFP_KERNEL);
 	if (!skb)
 		return -ENOMEM;
-		BUILD_BUG_ON(sizeof(skb->cb) <
-			     max_t(int, sizeof(struct rds_znotifier),
+	BUILD_BUG_ON(sizeof(skb->cb) < max_t(int, sizeof(struct rds_znotifier),
 					     sizeof(struct rds_zcopy_cookies)));
 	rm->data.op_mmp_znotifier = RDS_ZCOPY_SKB(skb);
 	if (mm_account_pinned_pages(&rm->data.op_mmp_znotifier->z_mmp,
@@ -397,7 +392,24 @@ int rds_message_copy_from_user(struct rds_message *rm, struct iov_iter *from,
 	consume_skb(skb);
 	rm->data.op_mmp_znotifier = NULL;
 	return ret;
-	} /* zcopy */
+}
+
+int rds_message_copy_from_user(struct rds_message *rm, struct iov_iter *from,
+			       bool zcopy)
+{
+	unsigned long to_copy, nbytes;
+	unsigned long sg_off;
+	struct scatterlist *sg;
+	int ret = 0;
+
+	rm->m_inc.i_hdr.h_len = cpu_to_be32(iov_iter_count(from));
+
+	/* now allocate and copy in the data payload.  */
+	sg = rm->data.op_sg;
+	sg_off = 0; /* Dear gcc, sg->page will be null from kzalloc. */
+
+	if (zcopy)
+		return rds_message_zcopy_from_user(rm, from);
 
 	while (iov_iter_count(from)) {
 		if (!sg_page(sg)) {