3 files changed, 33 insertions, 2 deletions

diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index 721dae795d68..d245c0bf7873 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -118,6 +118,10 @@ rpcrdma_convert_iovs(struct xdr_buf *xdrbuf, unsigned int pos,
 	}
 
 	if (xdrbuf->tail[0].iov_len) {
+		/* the rpcrdma protocol allows us to omit any trailing
+		 * xdr pad bytes, saving the server an RDMA operation. */
+		if (xdrbuf->tail[0].iov_len < 4 && xprt_rdma_pad_optimize)
+			return n;
 		if (n == nsegs)
 			return 0;
 		seg[n].mr_page = NULL;
@@ -594,7 +598,7 @@ rpcrdma_count_chunks(struct rpcrdma_rep *rep, unsigned int max, int wrchunk, __b
  * Scatter inline received data back into provided iov's.
  */
 static void
-rpcrdma_inline_fixup(struct rpc_rqst *rqst, char *srcp, int copy_len)
+rpcrdma_inline_fixup(struct rpc_rqst *rqst, char *srcp, int copy_len, int pad)
 {
 	int i, npages, curlen, olen;
 	char *destp;
@@ -660,6 +664,13 @@ rpcrdma_inline_fixup(struct rpc_rqst *rqst, char *srcp, int copy_len)
 	} else
 		rqst->rq_rcv_buf.tail[0].iov_len = 0;
 
+	if (pad) {
+		/* implicit padding on terminal chunk */
+		unsigned char *p = rqst->rq_rcv_buf.tail[0].iov_base;
+		while (pad--)
+			p[rqst->rq_rcv_buf.tail[0].iov_len++] = 0;
+	}
+
 	if (copy_len)
 		dprintk("RPC:       %s: %d bytes in"
 			" %d extra segments (%d lost)\n",
@@ -794,14 +805,20 @@ repost:
 			    ((unsigned char *)iptr - (unsigned char *)headerp);
 			status = rep->rr_len + rdmalen;
 			r_xprt->rx_stats.total_rdma_reply += rdmalen;
+			/* special case - last chunk may omit padding */
+			if (rdmalen &= 3) {
+				rdmalen = 4 - rdmalen;
+				status += rdmalen;
+			}
 		} else {
 			/* else ordinary inline */
+			rdmalen = 0;
 			iptr = (__be32 *)((unsigned char *)headerp + 28);
 			rep->rr_len -= 28; /*sizeof *headerp;*/
 			status = rep->rr_len;
 		}
 		/* Fix up the rpc results for upper layer */
-		rpcrdma_inline_fixup(rqst, (char *)iptr, rep->rr_len);
+		rpcrdma_inline_fixup(rqst, (char *)iptr, rep->rr_len, rdmalen);
 		break;
 
 	case __constant_htonl(RDMA_NOMSG):
diff --git a/net/sunrpc/xprtrdma/transport.c b/net/sunrpc/xprtrdma/transport.c
index ec6d1e7a1941..c7d2380bb5e3 100644
--- a/net/sunrpc/xprtrdma/transport.c
+++ b/net/sunrpc/xprtrdma/transport.c
@@ -71,6 +71,7 @@ static unsigned int xprt_rdma_max_inline_read = RPCRDMA_DEF_INLINE;
 static unsigned int xprt_rdma_max_inline_write = RPCRDMA_DEF_INLINE;
 static unsigned int xprt_rdma_inline_write_padding;
 static unsigned int xprt_rdma_memreg_strategy = RPCRDMA_FRMR;
+                int xprt_rdma_pad_optimize = 0;
 
 #ifdef RPC_DEBUG
 
@@ -136,6 +137,14 @@ static ctl_table xr_tunables_table[] = {
 		.extra2		= &max_memreg,
 	},
 	{
+		.ctl_name       = CTL_UNNUMBERED,
+		.procname	= "rdma_pad_optimize",
+		.data		= &xprt_rdma_pad_optimize,
+		.maxlen		= sizeof(unsigned int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec,
+	},
+	{
 		.ctl_name = 0,
 	},
 };
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index 2db2344d487e..fde6499a53b2 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -280,6 +280,11 @@ struct rpcrdma_xprt {
 #define rpcx_to_rdmax(x) container_of(x, struct rpcrdma_xprt, xprt)
 #define rpcx_to_rdmad(x) (rpcx_to_rdmax(x)->rx_data)
 
+/* Setting this to 0 ensures interoperability with early servers.
+ * Setting this to 1 enhances certain unaligned read/write performance.
+ * Default is 0, see sysctl entry and rpc_rdma.c rpcrdma_convert_iovs() */
+extern int xprt_rdma_pad_optimize;
+
 /*
  * Interface Adapter calls - xprtrdma/verbs.c
  */