[PATCH] RPC: clean up after nocong was removed

 Clean-up:  Move some macros that are specific to the Van Jacobson
 implementation into xprt.c.  Get rid of the cong_wait field in
 rpc_xprt, which is no longer used.  Get rid of xprt_clear_backlog.

 Test-plan:
 Compile with CONFIG_NFS enabled.

 Signed-off-by: Chuck Lever <cel@netapp.com>
 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 19 insertions, 10 deletions

diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index e8d11bd6158e..0458319a1bdd 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -62,7 +62,23 @@ static inline void	do_xprt_reserve(struct rpc_task *);
 static void     xprt_connect_status(struct rpc_task *task);
 static int      __xprt_get_cong(struct rpc_xprt *, struct rpc_task *);
 
-static int      xprt_clear_backlog(struct rpc_xprt *xprt);
+/*
+ * The transport code maintains an estimate on the maximum number of out-
+ * standing RPC requests, using a smoothed version of the congestion
+ * avoidance implemented in 44BSD. This is basically the Van Jacobson
+ * congestion algorithm: If a retransmit occurs, the congestion window is
+ * halved; otherwise, it is incremented by 1/cwnd when
+ *
+ *      -       a reply is received and
+ *      -       a full number of requests are outstanding and
+ *      -       the congestion window hasn't been updated recently.
+ */
+#define RPC_CWNDSHIFT           (8U)
+#define RPC_CWNDSCALE           (1U << RPC_CWNDSHIFT)
+#define RPC_INITCWND            RPC_CWNDSCALE
+#define RPC_MAXCWND(xprt)       ((xprt)->max_reqs << RPC_CWNDSHIFT)
+
+#define RPCXPRT_CONGESTED(xprt) ((xprt)->cong >= (xprt)->cwnd)
 
 /**
  * xprt_reserve_xprt - serialize write access to transports
@@ -850,7 +866,7 @@ void xprt_release(struct rpc_task *task)
 
         spin_lock(&xprt->reserve_lock);
         list_add(&req->rq_list, &xprt->free);
-        xprt_clear_backlog(xprt);
+        rpc_wake_up_next(&xprt->backlog);
         spin_unlock(&xprt->reserve_lock);
 }
 
@@ -902,7 +918,6 @@ static struct rpc_xprt *xprt_setup(int proto, struct sockaddr_in *ap, struct rpc
 
         spin_lock_init(&xprt->transport_lock);
         spin_lock_init(&xprt->reserve_lock);
-        init_waitqueue_head(&xprt->cong_wait);
 
         INIT_LIST_HEAD(&xprt->free);
         INIT_LIST_HEAD(&xprt->recv);
@@ -911,6 +926,7 @@ static struct rpc_xprt *xprt_setup(int proto, struct sockaddr_in *ap, struct rpc
         xprt->timer.function = xprt_init_autodisconnect;
         xprt->timer.data = (unsigned long) xprt;
         xprt->last_used = jiffies;
+        xprt->cwnd = RPC_INITCWND;
 
         rpc_init_wait_queue(&xprt->pending, "xprt_pending");
         rpc_init_wait_queue(&xprt->sending, "xprt_sending");
@@ -955,16 +971,9 @@ static void xprt_shutdown(struct rpc_xprt *xprt)
         rpc_wake_up(&xprt->resend);
         xprt_wake_pending_tasks(xprt, -EIO);
         rpc_wake_up(&xprt->backlog);
-        wake_up(&xprt->cong_wait);
         del_timer_sync(&xprt->timer);
 }
 
-static int xprt_clear_backlog(struct rpc_xprt *xprt) {
-        rpc_wake_up_next(&xprt->backlog);
-        wake_up(&xprt->cong_wait);
-        return 1;
-}
-
 /**
  * xprt_destroy - destroy an RPC transport, killing off all requests.
  * @xprt: transport to destroy