[PATCH RFC 4/8] svcrdma: RDMA transport support for automated padding of xdr_buf::pages

[Chuck Lever <chuck.lever@xxxxxxxxxx>]

---
 net/sunrpc/xprtrdma/svc_rdma_rw.c     |   13 +++++++++++++
 net/sunrpc/xprtrdma/svc_rdma_sendto.c |   27 +++++++++++++++++++--------
 2 files changed, 32 insertions(+), 8 deletions(-)

diff --git a/net/sunrpc/xprtrdma/svc_rdma_rw.c b/net/sunrpc/xprtrdma/svc_rdma_rw.c
index 467d40a1dffa..a7fb886ea136 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_rw.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_rw.c
@@ -14,6 +14,8 @@
 #include "xprt_rdma.h"
 #include <trace/events/rpcrdma.h>
 
+static const __be32 xdr_padding = xdr_zero;
+
 static void svc_rdma_write_done(struct ib_cq *cq, struct ib_wc *wc);
 static void svc_rdma_wc_read_done(struct ib_cq *cq, struct ib_wc *wc);
 
@@ -559,6 +561,9 @@ int svc_rdma_send_reply_chunk(struct svcxprt_rdma *rdma, __be32 *rp_ch,
 {
 	struct svc_rdma_write_info *info;
 	int consumed, ret;
+	struct kvec pad = {
+		.iov_base = (void *)&xdr_padding,
+	};
 
 	info = svc_rdma_write_info_alloc(rdma, rp_ch);
 	if (!info)
@@ -577,6 +582,14 @@ int svc_rdma_send_reply_chunk(struct svcxprt_rdma *rdma, __be32 *rp_ch,
 		if (ret < 0)
 			goto out_err;
 		consumed += xdr->page_len;
+
+		if (xdr->page_pad) {
+			pad.iov_len = xdr->page_pad;
+			ret = svc_rdma_send_xdr_kvec(info, &pad);
+			if (ret < 0)
+				goto out_err;
+			consumed += pad.iov_len;
+		}
 	}
 
 	if (xdr->tail[0].iov_len) {
diff --git a/net/sunrpc/xprtrdma/svc_rdma_sendto.c b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
index 33f817519964..d0f9acfe60a6 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_sendto.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
@@ -112,6 +112,8 @@
 #include "xprt_rdma.h"
 #include <trace/events/rpcrdma.h>
 
+static const __be32 xdr_padding = xdr_zero;
+
 static void svc_rdma_wc_send(struct ib_cq *cq, struct ib_wc *wc);
 
 static inline struct svc_rdma_send_ctxt *
@@ -320,11 +322,6 @@ int svc_rdma_send(struct svcxprt_rdma *rdma, struct ib_send_wr *wr)
 	return ret;
 }
 
-static u32 xdr_padsize(u32 len)
-{
-	return (len & 3) ? (4 - (len & 3)) : 0;
-}
-
 /* Returns length of transport header, in bytes.
  */
 static unsigned int svc_rdma_reply_hdr_len(__be32 *rdma_resp)
@@ -561,6 +558,8 @@ static bool svc_rdma_pull_up_needed(struct svcxprt_rdma *rdma,
 					   remaining);
 			pageoff = 0;
 		}
+		if (xdr->page_pad)
+			++elements;
 	}
 
 	/* xdr->tail */
@@ -593,7 +592,7 @@ static int svc_rdma_pull_up_reply_msg(struct svcxprt_rdma *rdma,
 	if (wr_lst) {
 		u32 xdrpad;
 
-		xdrpad = xdr_padsize(xdr->page_len);
+		xdrpad = xdr_pad_size(xdr->page_len);
 		if (taillen && xdrpad) {
 			tailbase += xdrpad;
 			taillen -= xdrpad;
@@ -614,12 +613,16 @@ static int svc_rdma_pull_up_reply_msg(struct svcxprt_rdma *rdma,
 			dst += len;
 			pageoff = 0;
 		}
+		if (xdr->page_pad) {
+			memcpy(dst, &xdr_padding, xdr->page_pad);
+			dst += xdr->page_pad;
+		}
 	}
 
 	if (taillen)
 		memcpy(dst, tailbase, taillen);
 
-	ctxt->sc_sges[0].length += xdr->len;
+	ctxt->sc_sges[0].length += xdr_buf_msglen(xdr);
 	ib_dma_sync_single_for_device(rdma->sc_pd->device,
 				      ctxt->sc_sges[0].addr,
 				      ctxt->sc_sges[0].length,
@@ -668,7 +671,7 @@ int svc_rdma_map_reply_msg(struct svcxprt_rdma *rdma,
 	if (wr_lst) {
 		base = xdr->tail[0].iov_base;
 		len = xdr->tail[0].iov_len;
-		xdr_pad = xdr_padsize(xdr->page_len);
+		xdr_pad = xdr_pad_size(xdr->page_len);
 
 		if (len && xdr_pad) {
 			base += xdr_pad;
@@ -693,6 +696,14 @@ int svc_rdma_map_reply_msg(struct svcxprt_rdma *rdma,
 		remaining -= len;
 		page_off = 0;
 	}
+	if (xdr->page_pad) {
+		++ctxt->sc_cur_sge_no;
+		ret = svc_rdma_dma_map_buf(rdma, ctxt,
+					   (unsigned char *)&xdr_padding,
+					   xdr->page_pad);
+		if (ret < 0)
+			return ret;
+	}
 
 	base = xdr->tail[0].iov_base;
 	len = xdr->tail[0].iov_len;