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>

1 files changed, 25 insertions, 6 deletions

diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 8975c10591c3..a48df1449ece 100644
--- a/net/sunrpc/xprtsock.c
+++ b/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;
                 }