Revert "SUNRPC: Micro-optimise when the task is known not to be sleeping"

This reverts commit 009a82f.

The ability to optimise here relies on compiler being able to optimise
away tail calls to avoid stack overflows. Unfortunately, we are seeing
reports of problems, so let's just revert.

Reported-by: Daniel Mack <daniel@zonque.org>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Author: Trond Myklebust

include/linux/sunrpc/sched.h

@@ -304,12 +304,4 @@ rpc_clnt_swap_deactivate(struct rpc_clnt *clnt)
 }
 #endif /* CONFIG_SUNRPC_SWAP */
 
-static inline bool
-rpc_task_need_resched(const struct rpc_task *task)
-{
-	if (RPC_IS_QUEUED(task) || task->tk_callback)
-		return true;
-	return false;
-}
-
 #endif /* _LINUX_SUNRPC_SCHED_H_ */

net/sunrpc/clnt.c

@@ -1540,7 +1540,6 @@ call_start(struct rpc_task *task)
 	clnt->cl_stats->rpccnt++;
 	task->tk_action = call_reserve;
 	rpc_task_set_transport(task, clnt);
-	call_reserve(task);
 }
 
 /*
@@ -1554,9 +1553,6 @@ call_reserve(struct rpc_task *task)
 	task->tk_status  = 0;
 	task->tk_action  = call_reserveresult;
 	xprt_reserve(task);
-	if (rpc_task_need_resched(task))
-		return;
-	 call_reserveresult(task);
 }
 
 static void call_retry_reserve(struct rpc_task *task);
@@ -1579,7 +1575,6 @@ call_reserveresult(struct rpc_task *task)
 	if (status >= 0) {
 		if (task->tk_rqstp) {
 			task->tk_action = call_refresh;
-			call_refresh(task);
 			return;
 		}
 
@@ -1605,7 +1600,6 @@ call_reserveresult(struct rpc_task *task)
 		/* fall through */
 	case -EAGAIN:	/* woken up; retry */
 		task->tk_action = call_retry_reserve;
-		call_retry_reserve(task);
 		return;
 	case -EIO:	/* probably a shutdown */
 		break;
@@ -1628,9 +1622,6 @@ call_retry_reserve(struct rpc_task *task)
 	task->tk_status  = 0;
 	task->tk_action  = call_reserveresult;
 	xprt_retry_reserve(task);
-	if (rpc_task_need_resched(task))
-		return;
-	call_reserveresult(task);
 }
 
 /*
@@ -1645,9 +1636,6 @@ call_refresh(struct rpc_task *task)
 	task->tk_status = 0;
 	task->tk_client->cl_stats->rpcauthrefresh++;
 	rpcauth_refreshcred(task);
-	if (rpc_task_need_resched(task))
-		return;
-	call_refreshresult(task);
 }
 
 /*
@@ -1666,7 +1654,6 @@ call_refreshresult(struct rpc_task *task)
 	case 0:
 		if (rpcauth_uptodatecred(task)) {
 			task->tk_action = call_allocate;
-			call_allocate(task);
 			return;
 		}
 		/* Use rate-limiting and a max number of retries if refresh
@@ -1685,7 +1672,6 @@ call_refreshresult(struct rpc_task *task)
 		task->tk_cred_retry--;
 		dprintk("RPC: %5u %s: retry refresh creds\n",
 				task->tk_pid, __func__);
-		call_refresh(task);
 		return;
 	}
 	dprintk("RPC: %5u %s: refresh creds failed with error %d\n",
@@ -1711,10 +1697,8 @@ call_allocate(struct rpc_task *task)
 	task->tk_status = 0;
 	task->tk_action = call_encode;
 
-	if (req->rq_buffer) {
-		call_encode(task);
+	if (req->rq_buffer)
 		return;
-	}
 
 	if (proc->p_proc != 0) {
 		BUG_ON(proc->p_arglen == 0);
@@ -1740,12 +1724,8 @@ call_allocate(struct rpc_task *task)
 
 	status = xprt->ops->buf_alloc(task);
 	xprt_inject_disconnect(xprt);
-	if (status == 0) {
-		if (rpc_task_need_resched(task))
-			return;
-		call_encode(task);
+	if (status == 0)
 		return;
-	}
 	if (status != -ENOMEM) {
 		rpc_exit(task, status);
 		return;
@@ -1828,8 +1808,12 @@ call_encode(struct rpc_task *task)
 		xprt_request_enqueue_receive(task);
 	xprt_request_enqueue_transmit(task);
 out:
-	task->tk_action = call_bind;
-	call_bind(task);
+	task->tk_action = call_transmit;
+	/* Check that the connection is OK */
+	if (!xprt_bound(task->tk_xprt))
+		task->tk_action = call_bind;
+	else if (!xprt_connected(task->tk_xprt))
+		task->tk_action = call_connect;
 }
 
 /*
@@ -1847,7 +1831,6 @@ rpc_task_handle_transmitted(struct rpc_task *task)
 {
 	xprt_end_transmit(task);
 	task->tk_action = call_transmit_status;
-	call_transmit_status(task);
 }
 
 /*
@@ -1865,7 +1848,6 @@ call_bind(struct rpc_task *task)
 
 	if (xprt_bound(xprt)) {
 		task->tk_action = call_connect;
-		call_connect(task);
 		return;
 	}
 
@@ -1896,7 +1878,6 @@ call_bind_status(struct rpc_task *task)
 		dprint_status(task);
 		task->tk_status = 0;
 		task->tk_action = call_connect;
-		call_connect(task);
 		return;
 	}
 
@@ -1981,7 +1962,6 @@ call_connect(struct rpc_task *task)
 
 	if (xprt_connected(xprt)) {
 		task->tk_action = call_transmit;
-		call_transmit(task);
 		return;
 	}
 
@@ -2051,7 +2031,6 @@ call_connect_status(struct rpc_task *task)
 	case 0:
 		clnt->cl_stats->netreconn++;
 		task->tk_action = call_transmit;
-		call_transmit(task);
 		return;
 	}
 	rpc_exit(task, status);
@@ -2087,9 +2066,6 @@ call_transmit(struct rpc_task *task)
 		xprt_transmit(task);
 	}
 	xprt_end_transmit(task);
-	if (rpc_task_need_resched(task))
-		return;
-	call_transmit_status(task);
 }
 
 /*
@@ -2107,9 +2083,6 @@ call_transmit_status(struct rpc_task *task)
 	if (rpc_task_transmitted(task)) {
 		if (task->tk_status == 0)
 			xprt_request_wait_receive(task);
-		if (rpc_task_need_resched(task))
-			return;
-		call_status(task);
 		return;
 	}
 
@@ -2170,7 +2143,6 @@ call_bc_encode(struct rpc_task *task)
 {
 	xprt_request_enqueue_transmit(task);
 	task->tk_action = call_bc_transmit;
-	call_bc_transmit(task);
 }
 
 /*
@@ -2261,7 +2233,6 @@ call_status(struct rpc_task *task)
 	status = task->tk_status;
 	if (status >= 0) {
 		task->tk_action = call_decode;
-		call_decode(task);
 		return;
 	}