[RFC] [PATCH 1/7] [net/9p] Additional elements to p9_fcall to accomodate zero copy.

["Venkateswararao Jujjuri (JV)" <jvrao@linux.vnet.ibm.com>]

Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
---
 net/9p/client.c   |   45 +++++++++++++++++++++++++++++++--------------
 net/9p/protocol.c |   38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 69 insertions(+), 14 deletions(-)

diff --git a/net/9p/client.c b/net/9p/client.c
index a848bca..f939edf 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -1270,7 +1270,14 @@ p9_client_read(struct p9_fid *fid, char *data, char __user *udata, u64 offset,
 	if (count < rsize)
 		rsize = count;
 
-	req = p9_client_rpc(clnt, P9_TREAD, "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_TREAD, "dqE", fid->fid, offset,
+				rsize, data ? data : udata);
+	} else {
+		req = p9_client_rpc(clnt, P9_TREAD, "dqd", fid->fid, offset,
+				rsize);
+	}
 	if (IS_ERR(req)) {
 		err = PTR_ERR(req);
 		goto error;
@@ -1284,13 +1291,15 @@ p9_client_read(struct p9_fid *fid, char *data, char __user *udata, u64 offset,
 
 	P9_DPRINTK(P9_DEBUG_9P, "<<< RREAD count %d\n", count);
 
-	if (data) {
-		memmove(data, dataptr, count);
-	} else {
-		err = copy_to_user(udata, dataptr, count);
-		if (err) {
-			err = -EFAULT;
-			goto free_and_error;
+	if (!req->tc->pbuf_size) {
+		if (data) {
+			memmove(data, dataptr, count);
+		} else {
+			err = copy_to_user(udata, dataptr, count);
+			if (err) {
+				err = -EFAULT;
+				goto free_and_error;
+			}
 		}
 	}
 	p9_free_req(clnt, req);
@@ -1323,12 +1332,20 @@ p9_client_write(struct p9_fid *fid, char *data, const char __user *udata,
 
 	if (count < rsize)
 		rsize = count;
-	if (data)
-		req = p9_client_rpc(clnt, P9_TWRITE, "dqD", fid->fid, offset,
-								rsize, data);
-	else
-		req = p9_client_rpc(clnt, P9_TWRITE, "dqU", fid->fid, offset,
-								rsize, udata);
+
+	if ((clnt->trans_mod->pref & P9_TRANS_PREF_PAYLOAD_MASK) ==
+			P9_TRANS_PREF_PAYLOAD_SEP) {
+		req = p9_client_rpc(clnt, P9_TWRITE, "dqF", fid->fid, offset,
+				rsize, data ? data : udata);
+	} else {
+		if (data)
+			req = p9_client_rpc(clnt, P9_TWRITE, "dqD", fid->fid,
+					offset, rsize, data);
+		else
+			req = p9_client_rpc(clnt, P9_TWRITE, "dqU", fid->fid,
+					offset, rsize, udata);
+	}
+
 	if (IS_ERR(req)) {
 		err = PTR_ERR(req);
 		goto error;
diff --git a/net/9p/protocol.c b/net/9p/protocol.c
index dfc358f..ea778dd 100644
--- a/net/9p/protocol.c
+++ b/net/9p/protocol.c
@@ -114,6 +114,24 @@ pdu_write_u(struct p9_fcall *pdu, const char __user *udata, size_t size)
 	return size - len;
 }
 
+static size_t
+pdu_write_uw(struct p9_fcall *pdu, const char *udata, size_t size)
+{
+	size_t len = min(pdu->capacity - pdu->size, size);
+	pdu->pbuf = udata;
+	pdu->pbuf_size = len;
+	return size - len;
+}
+
+static size_t
+pdu_write_ur(struct p9_fcall *pdu, const char *udata, size_t size)
+{
+	size_t len = min(pdu->capacity - pdu->size, size);
+	pdu->pbuf = udata;
+	pdu->pbuf_size = len;
+	return size - len;
+}
+
 /*
 	b - int8_t
 	w - int16_t
@@ -445,6 +463,26 @@ p9pdu_vwritef(struct p9_fcall *pdu, int proto_version, const char *fmt,
 					errcode = -EFAULT;
 			}
 			break;
+		case 'E':{
+				 int32_t count = va_arg(ap, int32_t);
+				 const char *udata = va_arg(ap, const void *);
+				 errcode = p9pdu_writef(pdu, proto_version, "d",
+						 count);
+				 if (!errcode && pdu_write_ur(pdu, udata,
+							 count))
+					 errcode = -EFAULT;
+			 }
+			 break;
+		case 'F':{
+				 int32_t count = va_arg(ap, int32_t);
+				 const char *udata = va_arg(ap, const void *);
+				 errcode = p9pdu_writef(pdu, proto_version, "d",
+						 count);
+				 if (!errcode && pdu_write_uw(pdu, udata,
+							 count))
+					 errcode = -EFAULT;
+			 }
+			 break;
 		case 'U':{
 				int32_t count = va_arg(ap, int32_t);
 				const char __user *udata =
-- 
1.6.5.2