xprtrdma: Update only specific fields in private receive buffer

Now that rpcrdma_inline_fixup() updates only two fields in
rq_rcv_buf, a full memcpy of that structure to rq_private_buf is
unwarranted. Updating rq_private_buf fields only where needed also
better documents what is going on.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Tested-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

1 files changed, 9 insertions, 4 deletions

diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index d018eb7814e7..a0e811dd7b84 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -750,6 +750,11 @@ rpcrdma_count_chunks(struct rpcrdma_rep *rep, int wrchunk, __be32 **iptrp)
  * The upper layer has set the maximum number of bytes it can
  * receive in each component of rq_rcv_buf. These values are set in
  * the head.iov_len, page_len, tail.iov_len, and buflen fields.
+ *
+ * Unlike the TCP equivalent (xdr_partial_copy_from_skb), in
+ * many cases this function simply updates iov_base pointers in
+ * rq_rcv_buf to point directly to the received reply data, to
+ * avoid copying reply data.
  */
 static void
 rpcrdma_inline_fixup(struct rpc_rqst *rqst, char *srcp, int copy_len, int pad)
@@ -763,6 +768,7 @@ rpcrdma_inline_fixup(struct rpc_rqst *rqst, char *srcp, int copy_len, int pad)
          * in the receive buffer, to avoid a memcopy.
          */
         rqst->rq_rcv_buf.head[0].iov_base = srcp;
+        rqst->rq_private_buf.head[0].iov_base = srcp;
 
         /* The contents of the receive buffer that follow
          * head.iov_len bytes are copied into the page list.
@@ -822,16 +828,15 @@ rpcrdma_inline_fixup(struct rpc_rqst *rqst, char *srcp, int copy_len, int pad)
         /* The tail iovec is redirected to the remaining data
          * in the receive buffer, to avoid a memcopy.
          */
-        if (copy_len || pad)
+        if (copy_len || pad) {
                 rqst->rq_rcv_buf.tail[0].iov_base = srcp;
+                rqst->rq_private_buf.tail[0].iov_base = srcp;
+        }
 
         if (copy_len)
                 dprintk("RPC:       %s: %d bytes in"
                         " %d extra segments (%d lost)\n",
                         __func__, olen, i, copy_len);
-
-        /* TBD avoid a warning from call_decode() */
-        rqst->rq_private_buf = rqst->rq_rcv_buf;
 }
 
 void