nfs41: Process the RPC call direction

Reading and storing the RPC direction is a three step process.

1. xs_tcp_read_calldir() reads the RPC direction, but it will not store it
in the XDR buffer since the 'struct rpc_rqst' is not yet available.

2. The 'struct rpc_rqst' is obtained during the TCP_RCV_COPY_DATA state.
This state need not necessarily be preceeded by the TCP_RCV_READ_CALLDIR.
For example, we may be reading a continuation packet to a large reply.
Therefore, we can't simply obtain the 'struct rpc_rqst' during the
TCP_RCV_READ_CALLDIR state and assume it's available during TCP_RCV_COPY_DATA.

This patch adds a new TCP_RCV_READ_CALLDIR flag to indicate the need to
read the RPC direction.  It then uses TCP_RCV_COPY_CALLDIR to indicate the
RPC direction needs to be saved after the 'struct rpc_rqst' has been allocated.

3. The 'struct rpc_rqst' is obtained by the xs_tcp_read_data() helper
functions.  xs_tcp_read_common() then saves the RPC direction in the XDR
buffer if TCP_RCV_COPY_CALLDIR is set.  This will happen when we're reading
the data immediately after the direction was read.  xs_tcp_read_common()
then clears this flag.

[was nfs41: Skip past the RPC call direction]
Signed-off-by: Ricardo Labiaga <Ricardo.Labiaga@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
[nfs41: sunrpc: Add RPC direction back into the XDR buffer]
Signed-off-by: Ricardo Labiaga <Ricardo.Labiaga@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
[nfs41: sunrpc: Don't skip past the RPC call direction]
Signed-off-by: Ricardo Labiaga <Ricardo.Labiaga@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>

net/sunrpc/clnt.c

@@ -1390,13 +1390,14 @@ rpc_verify_header(struct rpc_task *task)
 	}
 	if ((len -= 3) < 0)
 		goto out_overflow;
-	p += 1;	/* skip XID */
 
+	p += 1; /* skip XID */
 	if ((n = ntohl(*p++)) != RPC_REPLY) {
 		dprintk("RPC: %5u %s: not an RPC reply: %x\n",
 			task->tk_pid, __func__, n);
 		goto out_garbage;
 	}
+
 	if ((n = ntohl(*p++)) != RPC_MSG_ACCEPTED) {
 		if (--len < 0)
 			goto out_overflow;

net/sunrpc/xprtsock.c

@@ -270,12 +270,13 @@ struct sock_xprt {
 #define TCP_RCV_COPY_FRAGHDR	(1UL << 1)
 #define TCP_RCV_COPY_XID	(1UL << 2)
 #define TCP_RCV_COPY_DATA	(1UL << 3)
-#define TCP_RCV_COPY_CALLDIR	(1UL << 4)
+#define TCP_RCV_READ_CALLDIR	(1UL << 4)
+#define TCP_RCV_COPY_CALLDIR	(1UL << 5)
 
 /*
  * TCP RPC flags
  */
-#define TCP_RPC_REPLY		(1UL << 5)
+#define TCP_RPC_REPLY		(1UL << 6)
 
 static inline struct sockaddr *xs_addr(struct rpc_xprt *xprt)
 {
@@ -997,7 +998,7 @@ static inline void xs_tcp_read_xid(struct sock_xprt *transport, struct xdr_skb_r
 	if (used != len)
 		return;
 	transport->tcp_flags &= ~TCP_RCV_COPY_XID;
-	transport->tcp_flags |= TCP_RCV_COPY_CALLDIR;
+	transport->tcp_flags |= TCP_RCV_READ_CALLDIR;
 	transport->tcp_copied = 4;
 	dprintk("RPC:       reading %s XID %08x\n",
 			(transport->tcp_flags & TCP_RPC_REPLY) ? "reply for"
@@ -1026,9 +1027,13 @@ static inline void xs_tcp_read_calldir(struct sock_xprt *transport,
 	transport->tcp_offset += used;
 	if (used != len)
 		return;
-	transport->tcp_flags &= ~TCP_RCV_COPY_CALLDIR;
+	transport->tcp_flags &= ~TCP_RCV_READ_CALLDIR;
+	transport->tcp_flags |= TCP_RCV_COPY_CALLDIR;
 	transport->tcp_flags |= TCP_RCV_COPY_DATA;
-	transport->tcp_copied += 4;
+	/*
+	 * We don't yet have the XDR buffer, so we will write the calldir
+	 * out after we get the buffer from the 'struct rpc_rqst'
+	 */
 	if (ntohl(calldir) == RPC_REPLY)
 		transport->tcp_flags |= TCP_RPC_REPLY;
 	else
@@ -1059,6 +1064,20 @@ static inline void xs_tcp_read_request(struct rpc_xprt *xprt, struct xdr_skb_rea
 	}
 
 	rcvbuf = &req->rq_private_buf;
+
+	if (transport->tcp_flags & TCP_RCV_COPY_CALLDIR) {
+		/*
+		 * Save the RPC direction in the XDR buffer
+		 */
+		__be32	calldir = transport->tcp_flags & TCP_RPC_REPLY ?
+					htonl(RPC_REPLY) : 0;
+
+		memcpy(rcvbuf->head[0].iov_base + transport->tcp_copied,
+			&calldir, sizeof(calldir));
+		transport->tcp_copied += sizeof(calldir);
+		transport->tcp_flags &= ~TCP_RCV_COPY_CALLDIR;
+	}
+
 	len = desc->count;
 	if (len > transport->tcp_reclen - transport->tcp_offset) {
 		struct xdr_skb_reader my_desc;
@@ -1156,7 +1175,7 @@ static int xs_tcp_data_recv(read_descriptor_t *rd_desc, struct sk_buff *skb, uns
 			continue;
 		}
 		/* Read in the call/reply flag */
-		if (transport->tcp_flags & TCP_RCV_COPY_CALLDIR) {
+		if (transport->tcp_flags & TCP_RCV_READ_CALLDIR) {
 			xs_tcp_read_calldir(transport, &desc);
 			continue;
 		}