SUNRPC: Cleanup xs_tcp_read_common()

Simplify the code to avoid a full copy of the struct xdr_skb_reader.
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

net/sunrpc/xprtsock.c

@@ -1287,25 +1287,12 @@ static inline void xs_tcp_read_common(struct rpc_xprt *xprt,
 	}
 
 	len = desc->count;
-	if (len > transport->tcp_reclen - transport->tcp_offset) {
-		struct xdr_skb_reader my_desc;
-
-		len = transport->tcp_reclen - transport->tcp_offset;
-		memcpy(&my_desc, desc, sizeof(my_desc));
-		my_desc.count = len;
-		r = xdr_partial_copy_from_skb(rcvbuf, transport->tcp_copied,
-					  &my_desc, xdr_skb_read_bits);
-		desc->count -= r;
-		desc->offset += r;
-	} else
+	if (len > transport->tcp_reclen - transport->tcp_offset)
+		desc->count = transport->tcp_reclen - transport->tcp_offset;
 	r = xdr_partial_copy_from_skb(rcvbuf, transport->tcp_copied,
 					  desc, xdr_skb_read_bits);
 
-	if (r > 0) {
-		transport->tcp_copied += r;
-		transport->tcp_offset += r;
-	}
-	if (r != len) {
+	if (desc->count) {
 		/* Error when copying to the receive buffer,
 		 * usually because we weren't able to allocate
 		 * additional buffer pages. All we can do now
@@ -1325,6 +1312,10 @@ static inline void xs_tcp_read_common(struct rpc_xprt *xprt,
 		return;
 	}
 
+	transport->tcp_copied += r;
+	transport->tcp_offset += r;
+	desc->count = len - r;
+
 	dprintk("RPC:       XID %08x read %zd bytes\n",
 			ntohl(transport->tcp_xid), r);
 	dprintk("RPC:       xprt = %p, tcp_copied = %lu, tcp_offset = %u, "