SUNRPC: Turn off throttling of RPC slots for TCP sockets

The theory was that we would need to grab the socket lock anyway, so we
might as well use it to gate the allocation of RPC slots for a TCP
socket.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

include/linux/sunrpc/xprt.h

@@ -343,7 +343,6 @@ int			xprt_reserve_xprt_cong(struct rpc_xprt *xprt, struct rpc_task *task);
 void			xprt_alloc_slot(struct rpc_xprt *xprt, struct rpc_task *task);
 void			xprt_free_slot(struct rpc_xprt *xprt,
 				       struct rpc_rqst *req);
-void			xprt_lock_and_alloc_slot(struct rpc_xprt *xprt, struct rpc_task *task);
 bool			xprt_prepare_transmit(struct rpc_task *task);
 void			xprt_request_enqueue_transmit(struct rpc_task *task);
 void			xprt_request_enqueue_receive(struct rpc_task *task);

net/sunrpc/xprt.c

@@ -1429,20 +1429,6 @@ out_init_req:
 }
 EXPORT_SYMBOL_GPL(xprt_alloc_slot);
 
-void xprt_lock_and_alloc_slot(struct rpc_xprt *xprt, struct rpc_task *task)
-{
-	/* Note: grabbing the xprt_lock_write() ensures that we throttle
-	 * new slot allocation if the transport is congested (i.e. when
-	 * reconnecting a stream transport or when out of socket write
-	 * buffer space).
-	 */
-	if (xprt_lock_write(xprt, task)) {
-		xprt_alloc_slot(xprt, task);
-		xprt_release_write(xprt, task);
-	}
-}
-EXPORT_SYMBOL_GPL(xprt_lock_and_alloc_slot);
-
 void xprt_free_slot(struct rpc_xprt *xprt, struct rpc_rqst *req)
 {
 	spin_lock(&xprt->reserve_lock);

net/sunrpc/xprtsock.c

@@ -2809,7 +2809,7 @@ static const struct rpc_xprt_ops xs_udp_ops = {
 static const struct rpc_xprt_ops xs_tcp_ops = {
 	.reserve_xprt		= xprt_reserve_xprt,
 	.release_xprt		= xprt_release_xprt,
-	.alloc_slot		= xprt_lock_and_alloc_slot,
+	.alloc_slot		= xprt_alloc_slot,
 	.free_slot		= xprt_free_slot,
 	.rpcbind		= rpcb_getport_async,
 	.set_port		= xs_set_port,