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

Modify p9_client_write() to check the transport preference and act accordingly.
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>

1 files changed, 15 insertions, 6 deletions

diff --git a/net/9p/client.c b/net/9p/client.c
index 82079f902f56..412c52e1de74 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -1333,12 +1333,21 @@ 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);
+
+        /* Don't bother zerocopy form small IO (< 1024) */
+        if (((clnt->trans_mod->pref & P9_TRANS_PREF_PAYLOAD_MASK) ==
+                                P9_TRANS_PREF_PAYLOAD_SEP) && (rsize > 1024)) {
+                req = p9_client_rpc(clnt, P9_TWRITE, "dqE", fid->fid, offset,
+                                rsize, 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;