3 files changed, 33 insertions, 2 deletions

diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index 721dae795d6..d245c0bf787 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 ec6d1e7a194..c7d2380bb5e 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 2db2344d487..fde6499a53b 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
  */