[PATCH RFC 02/11] svcrdma: Clean up RDMA Write path

[Chuck Lever <chuck.lever@xxxxxxxxxx>]

Constify the xdr_buf argument to ensure the code here does not
modify it, to enable callers to also use "const struct xdr_buf *".

Also, rename the helper functions, which emit RDMA Writes, not
RDMA Sends.

Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
 net/sunrpc/xprtrdma/svc_rdma_rw.c |   36 +++++++++++++++---------------------
 1 file changed, 15 insertions(+), 21 deletions(-)

diff --git a/net/sunrpc/xprtrdma/svc_rdma_rw.c b/net/sunrpc/xprtrdma/svc_rdma_rw.c
index bd7c195d872e..529f00a6896c 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_rw.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_rw.c
@@ -161,7 +161,7 @@ struct svc_rdma_write_info {
 	__be32			*wi_segs;
 
 	/* SGL constructor arguments */
-	struct xdr_buf		*wi_xdr;
+	const struct xdr_buf	*wi_xdr;
 	unsigned char		*wi_base;
 	unsigned int		wi_next_off;
 
@@ -369,7 +369,7 @@ static void svc_rdma_pagelist_to_sg(struct svc_rdma_write_info *info,
 				    struct svc_rdma_rw_ctxt *ctxt)
 {
 	unsigned int sge_no, sge_bytes, page_off, page_no;
-	struct xdr_buf *xdr = info->wi_xdr;
+	const struct xdr_buf *xdr = info->wi_xdr;
 	struct scatterlist *sg;
 	struct page **page;
 
@@ -470,27 +470,22 @@ svc_rdma_build_writes(struct svc_rdma_write_info *info,
 	return -EIO;
 }
 
-/* Send one of an xdr_buf's kvecs by itself. To send a Reply
- * chunk, the whole RPC Reply is written back to the client.
- * This function writes either the head or tail of the xdr_buf
- * containing the Reply.
+/* RDMA Write an iov.
  */
-static int svc_rdma_send_xdr_kvec(struct svc_rdma_write_info *info,
-				  struct kvec *vec)
+static int svc_rdma_write_vec(struct svc_rdma_write_info *info,
+			      const struct kvec *vec)
 {
 	info->wi_base = vec->iov_base;
 	return svc_rdma_build_writes(info, svc_rdma_vec_to_sg,
 				     vec->iov_len);
 }
 
-/* Send an xdr_buf's page list by itself. A Write chunk is just
- * the page list. A Reply chunk is @xdr's head, page list, and
- * tail. This function is shared between the two types of chunk.
+/* RDMA Write an xdr_buf's page list by itself.
  */
-static int svc_rdma_send_xdr_pagelist(struct svc_rdma_write_info *info,
-				      struct xdr_buf *xdr,
-				      unsigned int offset,
-				      unsigned long length)
+static int svc_rdma_write_pages(struct svc_rdma_write_info *info,
+				const struct xdr_buf *xdr,
+				unsigned int offset,
+				unsigned long length)
 {
 	info->wi_xdr = xdr;
 	info->wi_next_off = offset - xdr->head[0].iov_len;
@@ -527,7 +522,7 @@ int svc_rdma_send_write_chunk(struct svcxprt_rdma *rdma, __be32 *wr_ch,
 	if (!info)
 		return -ENOMEM;
 
-	ret = svc_rdma_send_xdr_pagelist(info, xdr, offset, length);
+	ret = svc_rdma_write_pages(info, xdr, offset, length);
 	if (ret < 0)
 		goto out_err;
 
@@ -567,7 +562,7 @@ int svc_rdma_send_reply_chunk(struct svcxprt_rdma *rdma,
 	if (!info)
 		return -ENOMEM;
 
-	ret = svc_rdma_send_xdr_kvec(info, &xdr->head[0]);
+	ret = svc_rdma_write_vec(info, &xdr->head[0]);
 	if (ret < 0)
 		goto out_err;
 	consumed = xdr->head[0].iov_len;
@@ -576,16 +571,15 @@ int svc_rdma_send_reply_chunk(struct svcxprt_rdma *rdma,
 	 * client did not provide Write chunks.
 	 */
 	if (!rctxt->rc_write_list && xdr->page_len) {
-		ret = svc_rdma_send_xdr_pagelist(info, xdr,
-						 xdr->head[0].iov_len,
-						 xdr->page_len);
+		ret = svc_rdma_write_pages(info, xdr, xdr->head[0].iov_len,
+					   xdr->page_len);
 		if (ret < 0)
 			goto out_err;
 		consumed += xdr->page_len;
 	}
 
 	if (xdr->tail[0].iov_len) {
-		ret = svc_rdma_send_xdr_kvec(info, &xdr->tail[0]);
+		ret = svc_rdma_write_vec(info, &xdr->tail[0]);
 		if (ret < 0)
 			goto out_err;
 		consumed += xdr->tail[0].iov_len;