SUNRPC: Add a separate spinlock to protect the RPC request receive list

This further reduces contention with the transport_lock, and allows us
to convert to using a non-bh-safe spinlock, since the list is now never
accessed from a bh context.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

include/linux/sunrpc/xprt.h

@@ -232,6 +232,7 @@ struct rpc_xprt {
 	 */
 	spinlock_t		transport_lock;	/* lock transport info */
 	spinlock_t		reserve_lock;	/* lock slot table */
+	spinlock_t		recv_lock;	/* lock receive list */
 	u32			xid;		/* Next XID value to use */
 	struct rpc_task *	snd_task;	/* Task blocked in send */
 	struct svc_xprt		*bc_xprt;	/* NFSv4.1 backchannel */

net/sunrpc/svcsock.c

@@ -1001,7 +1001,7 @@ static int receive_cb_reply(struct svc_sock *svsk, struct svc_rqst *rqstp)
 
 	if (!bc_xprt)
 		return -EAGAIN;
-	spin_lock_bh(&bc_xprt->transport_lock);
+	spin_lock(&bc_xprt->recv_lock);
 	req = xprt_lookup_rqst(bc_xprt, xid);
 	if (!req)
 		goto unlock_notfound;
@@ -1019,7 +1019,7 @@ static int receive_cb_reply(struct svc_sock *svsk, struct svc_rqst *rqstp)
 	memcpy(dst->iov_base, src->iov_base, src->iov_len);
 	xprt_complete_rqst(req->rq_task, rqstp->rq_arg.len);
 	rqstp->rq_arg.len = 0;
-	spin_unlock_bh(&bc_xprt->transport_lock);
+	spin_unlock(&bc_xprt->recv_lock);
 	return 0;
 unlock_notfound:
 	printk(KERN_NOTICE
@@ -1028,7 +1028,7 @@ static int receive_cb_reply(struct svc_sock *svsk, struct svc_rqst *rqstp)
 		__func__, ntohl(calldir),
 		bc_xprt, ntohl(xid));
 unlock_eagain:
-	spin_unlock_bh(&bc_xprt->transport_lock);
+	spin_unlock(&bc_xprt->recv_lock);
 	return -EAGAIN;
 }
 

net/sunrpc/xprt.c

@@ -872,17 +872,17 @@ void xprt_unpin_rqst(struct rpc_rqst *req)
 }
 
 static void xprt_wait_on_pinned_rqst(struct rpc_rqst *req)
-__must_hold(&req->rq_xprt->transport_lock)
+__must_hold(&req->rq_xprt->recv_lock)
 {
 	struct rpc_task *task = req->rq_task;
 	
 	if (task && test_bit(RPC_TASK_MSG_RECV, &task->tk_runstate)) {
-		spin_unlock_bh(&req->rq_xprt->transport_lock);
+		spin_unlock(&req->rq_xprt->recv_lock);
 		set_bit(RPC_TASK_MSG_RECV_WAIT, &task->tk_runstate);
 		wait_on_bit(&task->tk_runstate, RPC_TASK_MSG_RECV,
 				TASK_UNINTERRUPTIBLE);
 		clear_bit(RPC_TASK_MSG_RECV_WAIT, &task->tk_runstate);
-		spin_lock_bh(&req->rq_xprt->transport_lock);
+		spin_lock(&req->rq_xprt->recv_lock);
 	}
 }
 
@@ -1008,13 +1008,13 @@ void xprt_transmit(struct rpc_task *task)
 			/*
 			 * Add to the list only if we're expecting a reply
 			 */
-			spin_lock_bh(&xprt->transport_lock);
 			/* Update the softirq receive buffer */
 			memcpy(&req->rq_private_buf, &req->rq_rcv_buf,
 					sizeof(req->rq_private_buf));
 			/* Add request to the receive list */
+			spin_lock(&xprt->recv_lock);
 			list_add_tail(&req->rq_list, &xprt->recv);
-			spin_unlock_bh(&xprt->transport_lock);
+			spin_unlock(&xprt->recv_lock);
 			xprt_reset_majortimeo(req);
 			/* Turn off autodisconnect */
 			del_singleshot_timer_sync(&xprt->timer);
@@ -1329,15 +1329,18 @@ void xprt_release(struct rpc_task *task)
 		task->tk_ops->rpc_count_stats(task, task->tk_calldata);
 	else if (task->tk_client)
 		rpc_count_iostats(task, task->tk_client->cl_metrics);
+	spin_lock(&xprt->recv_lock);
+	if (!list_empty(&req->rq_list)) {
+		list_del(&req->rq_list);
+		xprt_wait_on_pinned_rqst(req);
+	}
+	spin_unlock(&xprt->recv_lock);
 	spin_lock_bh(&xprt->transport_lock);
 	xprt->ops->release_xprt(xprt, task);
 	if (xprt->ops->release_request)
 		xprt->ops->release_request(task);
-	if (!list_empty(&req->rq_list))
-		list_del(&req->rq_list);
 	xprt->last_used = jiffies;
 	xprt_schedule_autodisconnect(xprt);
-	xprt_wait_on_pinned_rqst(req);
 	spin_unlock_bh(&xprt->transport_lock);
 	if (req->rq_buffer)
 		xprt->ops->buf_free(task);
@@ -1361,6 +1364,7 @@ static void xprt_init(struct rpc_xprt *xprt, struct net *net)
 
 	spin_lock_init(&xprt->transport_lock);
 	spin_lock_init(&xprt->reserve_lock);
+	spin_lock_init(&xprt->recv_lock);
 
 	INIT_LIST_HEAD(&xprt->free);
 	INIT_LIST_HEAD(&xprt->recv);

net/sunrpc/xprtrdma/rpc_rdma.c

@@ -1051,7 +1051,7 @@ rpcrdma_reply_handler(struct work_struct *work)
 	 * RPC completion while holding the transport lock to ensure
 	 * the rep, rqst, and rq_task pointers remain stable.
 	 */
-	spin_lock_bh(&xprt->transport_lock);
+	spin_lock(&xprt->recv_lock);
 	rqst = xprt_lookup_rqst(xprt, headerp->rm_xid);
 	if (!rqst)
 		goto out_norqst;
@@ -1136,7 +1136,7 @@ rpcrdma_reply_handler(struct work_struct *work)
 		xprt_release_rqst_cong(rqst->rq_task);
 
 	xprt_complete_rqst(rqst->rq_task, status);
-	spin_unlock_bh(&xprt->transport_lock);
+	spin_unlock(&xprt->recv_lock);
 	dprintk("RPC:       %s: xprt_complete_rqst(0x%p, 0x%p, %d)\n",
 		__func__, xprt, rqst, status);
 	return;
@@ -1187,12 +1187,12 @@ rpcrdma_reply_handler(struct work_struct *work)
 	r_xprt->rx_stats.bad_reply_count++;
 	goto out;
 
-/* The req was still available, but by the time the transport_lock
+/* The req was still available, but by the time the recv_lock
  * was acquired, the rqst and task had been released. Thus the RPC
  * has already been terminated.
  */
 out_norqst:
-	spin_unlock_bh(&xprt->transport_lock);
+	spin_unlock(&xprt->recv_lock);
 	rpcrdma_buffer_put(req);
 	dprintk("RPC:       %s: race, no rqst left for req %p\n",
 		__func__, req);

net/sunrpc/xprtrdma/svc_rdma_backchannel.c

@@ -52,7 +52,7 @@ int svc_rdma_handle_bc_reply(struct rpc_xprt *xprt, __be32 *rdma_resp,
 	if (src->iov_len < 24)
 		goto out_shortreply;
 
-	spin_lock_bh(&xprt->transport_lock);
+	spin_lock(&xprt->recv_lock);
 	req = xprt_lookup_rqst(xprt, xid);
 	if (!req)
 		goto out_notfound;
@@ -69,17 +69,20 @@ int svc_rdma_handle_bc_reply(struct rpc_xprt *xprt, __be32 *rdma_resp,
 	else if (credits > r_xprt->rx_buf.rb_bc_max_requests)
 		credits = r_xprt->rx_buf.rb_bc_max_requests;
 
+	spin_lock_bh(&xprt->transport_lock);
 	cwnd = xprt->cwnd;
 	xprt->cwnd = credits << RPC_CWNDSHIFT;
 	if (xprt->cwnd > cwnd)
 		xprt_release_rqst_cong(req->rq_task);
+	spin_unlock_bh(&xprt->transport_lock);
+
 
 	ret = 0;
 	xprt_complete_rqst(req->rq_task, rcvbuf->len);
 	rcvbuf->len = 0;
 
 out_unlock:
-	spin_unlock_bh(&xprt->transport_lock);
+	spin_unlock(&xprt->recv_lock);
 out:
 	return ret;
 

net/sunrpc/xprtsock.c

@@ -969,12 +969,12 @@ static void xs_local_data_read_skb(struct rpc_xprt *xprt,
 		return;
 
 	/* Look up and lock the request corresponding to the given XID */
-	spin_lock_bh(&xprt->transport_lock);
+	spin_lock(&xprt->recv_lock);
 	rovr = xprt_lookup_rqst(xprt, *xp);
 	if (!rovr)
 		goto out_unlock;
 	xprt_pin_rqst(rovr);
-	spin_unlock_bh(&xprt->transport_lock);
+	spin_unlock(&xprt->recv_lock);
 	task = rovr->rq_task;
 
 	copied = rovr->rq_private_buf.buflen;
@@ -983,16 +983,16 @@ static void xs_local_data_read_skb(struct rpc_xprt *xprt,
 
 	if (xs_local_copy_to_xdr(&rovr->rq_private_buf, skb)) {
 		dprintk("RPC:       sk_buff copy failed\n");
-		spin_lock_bh(&xprt->transport_lock);
+		spin_lock(&xprt->recv_lock);
 		goto out_unpin;
 	}
 
-	spin_lock_bh(&xprt->transport_lock);
+	spin_lock(&xprt->recv_lock);
 	xprt_complete_rqst(task, copied);
 out_unpin:
 	xprt_unpin_rqst(rovr);
  out_unlock:
-	spin_unlock_bh(&xprt->transport_lock);
+	spin_unlock(&xprt->recv_lock);
 }
 
 static void xs_local_data_receive(struct sock_xprt *transport)
@@ -1055,12 +1055,12 @@ static void xs_udp_data_read_skb(struct rpc_xprt *xprt,
 		return;
 
 	/* Look up and lock the request corresponding to the given XID */
-	spin_lock_bh(&xprt->transport_lock);
+	spin_lock(&xprt->recv_lock);
 	rovr = xprt_lookup_rqst(xprt, *xp);
 	if (!rovr)
 		goto out_unlock;
 	xprt_pin_rqst(rovr);
-	spin_unlock_bh(&xprt->transport_lock);
+	spin_unlock(&xprt->recv_lock);
 	task = rovr->rq_task;
 
 	if ((copied = rovr->rq_private_buf.buflen) > repsize)
@@ -1069,7 +1069,7 @@ static void xs_udp_data_read_skb(struct rpc_xprt *xprt,
 	/* Suck it into the iovec, verify checksum if not done by hw. */
 	if (csum_partial_copy_to_xdr(&rovr->rq_private_buf, skb)) {
 		__UDPX_INC_STATS(sk, UDP_MIB_INERRORS);
-		spin_lock_bh(&xprt->transport_lock);
+		spin_lock(&xprt->recv_lock);
 		goto out_unpin;
 	}
 
@@ -1077,11 +1077,13 @@ static void xs_udp_data_read_skb(struct rpc_xprt *xprt,
 
 	spin_lock_bh(&xprt->transport_lock);
 	xprt_adjust_cwnd(xprt, task, copied);
+	spin_unlock_bh(&xprt->transport_lock);
+	spin_lock(&xprt->recv_lock);
 	xprt_complete_rqst(task, copied);
 out_unpin:
 	xprt_unpin_rqst(rovr);
  out_unlock:
-	spin_unlock_bh(&xprt->transport_lock);
+	spin_unlock(&xprt->recv_lock);
 }
 
 static void xs_udp_data_receive(struct sock_xprt *transport)
@@ -1344,24 +1346,24 @@ static inline int xs_tcp_read_reply(struct rpc_xprt *xprt,
 	dprintk("RPC:       read reply XID %08x\n", ntohl(transport->tcp_xid));
 
 	/* Find and lock the request corresponding to this xid */
-	spin_lock_bh(&xprt->transport_lock);
+	spin_lock(&xprt->recv_lock);
 	req = xprt_lookup_rqst(xprt, transport->tcp_xid);
 	if (!req) {
 		dprintk("RPC:       XID %08x request not found!\n",
 				ntohl(transport->tcp_xid));
-		spin_unlock_bh(&xprt->transport_lock);
+		spin_unlock(&xprt->recv_lock);
 		return -1;
 	}
 	xprt_pin_rqst(req);
-	spin_unlock_bh(&xprt->transport_lock);
+	spin_unlock(&xprt->recv_lock);
 
 	xs_tcp_read_common(xprt, desc, req);
 
-	spin_lock_bh(&xprt->transport_lock);
+	spin_lock(&xprt->recv_lock);
 	if (!(transport->tcp_flags & TCP_RCV_COPY_DATA))
 		xprt_complete_rqst(req->rq_task, transport->tcp_copied);
 	xprt_unpin_rqst(req);
-	spin_unlock_bh(&xprt->transport_lock);
+	spin_unlock(&xprt->recv_lock);
 	return 0;
 }