[net/9p] readdir zerocopy changes for 9P2000.L protocol.

Modify p9_client_readdir() to check the transport preference and act according
If the preference is P9_TRANS_PREF_PAYLOAD_SEP, send the payload
separately instead of putting it directly on PDU.

Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
diff --git a/net/9p/client.c b/net/9p/client.c
index 412c52e..6e07ef4 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -1735,7 +1735,14 @@
 	if (count < rsize)
 		rsize = count;
 
-	req = p9_client_rpc(clnt, P9_TREADDIR, "dqd", fid->fid, offset, rsize);
+	if ((clnt->trans_mod->pref & P9_TRANS_PREF_PAYLOAD_MASK) ==
+			P9_TRANS_PREF_PAYLOAD_SEP) {
+		req = p9_client_rpc(clnt, P9_TREADDIR, "dqF", fid->fid,
+				offset, rsize, data);
+	} else {
+		req = p9_client_rpc(clnt, P9_TREADDIR, "dqd", fid->fid,
+				offset, rsize);
+	}
 	if (IS_ERR(req)) {
 		err = PTR_ERR(req);
 		goto error;
@@ -1749,7 +1756,7 @@
 
 	P9_DPRINTK(P9_DEBUG_9P, "<<< RREADDIR count %d\n", count);
 
-	if (data)
+	if (!req->tc->pbuf_size && data)
 		memmove(data, dataptr, count);
 
 	p9_free_req(clnt, req);