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

Modify p9_client_read() 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, 18 insertions, 8 deletions

diff --git a/net/9p/client.c b/net/9p/client.c
index a848bca9fbff..82079f902f56 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -1270,7 +1270,15 @@ 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);
+        /* 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_TREAD, "dqE", fid->fid, offset,
+                                rsize, 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 +1292,15 @@ 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);