3 files changed, 57 insertions, 12 deletions

diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h
index ac08e99a81cb..eee1c6877851 100644
--- a/include/linux/sunrpc/xprt.h
+++ b/include/linux/sunrpc/xprt.h
@@ -132,6 +132,7 @@ struct rpc_xprt;
 
 struct rpc_xprt_ops {
         void            (*set_buffer_size)(struct rpc_xprt *xprt);
+        int             (*reserve_xprt)(struct rpc_task *task);
         void            (*connect)(struct rpc_task *task);
         int             (*send_request)(struct rpc_task *task);
         void            (*set_retrans_timeout)(struct rpc_task *task);
@@ -232,6 +233,8 @@ void			xprt_set_timeout(struct rpc_timeout *to, unsigned int retr, unsigned long
  */
 void                    xprt_connect(struct rpc_task *task);
 void                    xprt_reserve(struct rpc_task *task);
+int                     xprt_reserve_xprt(struct rpc_task *task);
+int                     xprt_reserve_xprt_cong(struct rpc_task *task);
 int                     xprt_prepare_transmit(struct rpc_task *task);
 void                    xprt_transmit(struct rpc_task *task);
 int                     xprt_adjust_timeout(struct rpc_rqst *req);
diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index 1ac2fbe05102..2d1e8b83dd68 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -64,14 +64,56 @@ static int      __xprt_get_cong(struct rpc_xprt *, struct rpc_task *);
 
 static int      xprt_clear_backlog(struct rpc_xprt *xprt);
 
+/**
+ * xprt_reserve_xprt - serialize write access to transports
+ * @task: task that is requesting access to the transport
+ *
+ * This prevents mixing the payload of separate requests, and prevents
+ * transport connects from colliding with writes.  No congestion control
+ * is provided.
+ */
+int xprt_reserve_xprt(struct rpc_task *task)
+{
+        struct rpc_xprt *xprt = task->tk_xprt;
+        struct rpc_rqst *req = task->tk_rqstp;
+
+        if (test_and_set_bit(XPRT_LOCKED, &xprt->state)) {
+                if (task == xprt->snd_task)
+                        return 1;
+                if (task == NULL)
+                        return 0;
+                goto out_sleep;
+        }
+        xprt->snd_task = task;
+        if (req) {
+                req->rq_bytes_sent = 0;
+                req->rq_ntrans++;
+        }
+        return 1;
+
+out_sleep:
+        dprintk("RPC: %4d failed to lock transport %p\n",
+                        task->tk_pid, xprt);
+        task->tk_timeout = 0;
+        task->tk_status = -EAGAIN;
+        if (req && req->rq_ntrans)
+                rpc_sleep_on(&xprt->resend, task, NULL, NULL);
+        else
+                rpc_sleep_on(&xprt->sending, task, NULL, NULL);
+        return 0;
+}
+
 /*
- * Serialize write access to transports, in order to prevent different
- * requests from interfering with each other.
- * Also prevents transport connects from colliding with writes.
+ * xprt_reserve_xprt_cong - serialize write access to transports
+ * @task: task that is requesting access to the transport
+ *
+ * Same as xprt_reserve_xprt, but Van Jacobson congestion control is
+ * integrated into the decision of whether a request is allowed to be
+ * woken up and given access to the transport.
  */
-static int
-__xprt_lock_write(struct rpc_xprt *xprt, struct rpc_task *task)
+int xprt_reserve_xprt_cong(struct rpc_task *task)
 {
+        struct rpc_xprt *xprt = task->tk_xprt;
         struct rpc_rqst *req = task->tk_rqstp;
 
         if (test_and_set_bit(XPRT_LOCKED, &xprt->state)) {
@@ -79,7 +121,7 @@ __xprt_lock_write(struct rpc_xprt *xprt, struct rpc_task *task)
                         return 1;
                 goto out_sleep;
         }
-        if (xprt->nocong || __xprt_get_cong(xprt, task)) {
+        if (__xprt_get_cong(xprt, task)) {
                 xprt->snd_task = task;
                 if (req) {
                         req->rq_bytes_sent = 0;
@@ -101,20 +143,18 @@ out_sleep:
         return 0;
 }
 
-static inline int
-xprt_lock_write(struct rpc_xprt *xprt, struct rpc_task *task)
+static inline int xprt_lock_write(struct rpc_xprt *xprt, struct rpc_task *task)
 {
         int retval;
 
         spin_lock_bh(&xprt->transport_lock);
-        retval = __xprt_lock_write(xprt, task);
+        retval = xprt->ops->reserve_xprt(task);
         spin_unlock_bh(&xprt->transport_lock);
         return retval;
 }
 
 
-static void
-__xprt_lock_write_next(struct rpc_xprt *xprt)
+static void __xprt_lock_write_next(struct rpc_xprt *xprt)
 {
         struct rpc_task *task;
 
@@ -598,7 +638,7 @@ int xprt_prepare_transmit(struct rpc_task *task)
                 err = req->rq_received;
                 goto out_unlock;
         }
-        if (!__xprt_lock_write(xprt, task)) {
+        if (!xprt->ops->reserve_xprt(task)) {
                 err = -EAGAIN;
                 goto out_unlock;
         }
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 79433ffd1df0..fc4fbe8ea346 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -1045,6 +1045,7 @@ static void xs_connect(struct rpc_task *task)
 
 static struct rpc_xprt_ops xs_udp_ops = {
         .set_buffer_size        = xs_udp_set_buffer_size,
+        .reserve_xprt           = xprt_reserve_xprt_cong,
         .connect                = xs_connect,
         .send_request           = xs_udp_send_request,
         .set_retrans_timeout    = xprt_set_retrans_timeout_rtt,
@@ -1054,6 +1055,7 @@ static struct rpc_xprt_ops xs_udp_ops = {
 
 static struct rpc_xprt_ops xs_tcp_ops = {
         .set_buffer_size        = xs_tcp_set_buffer_size,
+        .reserve_xprt           = xprt_reserve_xprt,
         .connect                = xs_connect,
         .send_request           = xs_tcp_send_request,
         .set_retrans_timeout    = xprt_set_retrans_timeout_def,