[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>

2 files changed, 39 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);
diff --git a/net/9p/protocol.c b/net/9p/protocol.c
index 5936c50d0c93..7bca2421bfc8 100644
--- a/net/9p/protocol.c
+++ b/net/9p/protocol.c
@@ -114,6 +114,17 @@ pdu_write_u(struct p9_fcall *pdu, const char __user *udata, size_t size)
         return size - len;
 }
 
+static size_t
+pdu_write_urw(struct p9_fcall *pdu, const char *kdata, const char __user *udata,
+                size_t size)
+{
+        BUG_ON(pdu->size > P9_IOHDRSZ);
+        pdu->pubuf = (char __user *)udata;
+        pdu->pkbuf = (char *)kdata;
+        pdu->pbuf_size = size;
+        return 0;
+}
+
 /*
         b - int8_t
         w - int16_t
@@ -445,6 +456,16 @@ p9pdu_vwritef(struct p9_fcall *pdu, int proto_version, const char *fmt,
                                         errcode = -EFAULT;
                         }
                         break;
+                case 'E':{
+                                 int32_t cnt = va_arg(ap, int32_t);
+                                 const char *k = va_arg(ap, const void *);
+                                 const char *u = va_arg(ap, const void *);
+                                 errcode = p9pdu_writef(pdu, proto_version, "d",
+                                                 cnt);
+                                 if (!errcode && pdu_write_urw(pdu, k, u, cnt))
+                                        errcode = -EFAULT;
+                         }
+                         break;
                 case 'U':{
                                 int32_t count = va_arg(ap, int32_t);
                                 const char __user *udata =