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Subject: [PATCH v4 23/33] SUNRPC: Refactor recvfrom path dealing with
 incomplete TCP receives
From:   Chuck Lever <chuck.lever@oracle.com>
To:     bfields@fieldses.org
Cc:     linux-nfs@vger.kernel.org, linux-rdma@vger.kernel.org
Date:   Sat, 30 May 2020 09:30:05 -0400
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Clean up: move exception processing out of the main path.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 include/trace/events/sunrpc.h |   31 +++++++++++++++++++++++++++++++
 net/sunrpc/svcsock.c          |   39 +++++++++++++++++++--------------------
 2 files changed, 50 insertions(+), 20 deletions(-)

diff --git a/include/trace/events/sunrpc.h b/include/trace/events/sunrpc.h
index dc7388b72501..22e67fbf79b0 100644
--- a/include/trace/events/sunrpc.h
+++ b/include/trace/events/sunrpc.h
@@ -1522,9 +1522,40 @@ DECLARE_EVENT_CLASS(svcsock_class,
 DEFINE_SVCSOCK_EVENT(udp_send);
 DEFINE_SVCSOCK_EVENT(tcp_send);
 DEFINE_SVCSOCK_EVENT(tcp_recv);
+DEFINE_SVCSOCK_EVENT(tcp_recv_eagain);
+DEFINE_SVCSOCK_EVENT(tcp_recv_err);
 DEFINE_SVCSOCK_EVENT(data_ready);
 DEFINE_SVCSOCK_EVENT(write_space);
 
+TRACE_EVENT(svcsock_tcp_recv_short,
+	TP_PROTO(
+		const struct svc_xprt *xprt,
+		u32 expected,
+		u32 received
+	),
+
+	TP_ARGS(xprt, expected, received),
+
+	TP_STRUCT__entry(
+		__field(u32, expected)
+		__field(u32, received)
+		__field(unsigned long, flags)
+		__string(addr, xprt->xpt_remotebuf)
+	),
+
+	TP_fast_assign(
+		__entry->expected = expected;
+		__entry->received = received;
+		__entry->flags = xprt->xpt_flags;
+		__assign_str(addr, xprt->xpt_remotebuf);
+	),
+
+	TP_printk("addr=%s flags=%s expected=%u received=%u",
+		__get_str(addr), show_svc_xprt_flags(__entry->flags),
+		__entry->expected, __entry->received
+	)
+);
+
 TRACE_EVENT(svcsock_tcp_state,
 	TP_PROTO(
 		const struct svc_xprt *xprt,
diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index 8cf06b676831..087e21b0f1bb 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -968,23 +968,10 @@ static int svc_tcp_recvfrom(struct svc_rqst *rqstp)
 		svsk->sk_tcplen += len;
 		svsk->sk_datalen += len;
 	}
-	if (len != want || !svc_sock_final_rec(svsk)) {
-		svc_tcp_save_pages(svsk, rqstp);
-		if (len < 0 && len != -EAGAIN)
-			goto err_delete;
-		if (len == want)
-			svc_tcp_fragment_received(svsk);
-		else
-			dprintk("svc: incomplete TCP record (%d of %d)\n",
-				(int)(svsk->sk_tcplen - sizeof(rpc_fraghdr)),
-				svc_sock_reclen(svsk));
-		goto err_noclose;
-	}
-
-	if (svsk->sk_datalen < 8) {
-		svsk->sk_datalen = 0;
-		goto err_delete; /* client is nuts. */
-	}
+	if (len != want || !svc_sock_final_rec(svsk))
+		goto err_incomplete;
+	if (svsk->sk_datalen < 8)
+		goto err_nuts;
 
 	rqstp->rq_arg.len = svsk->sk_datalen;
 	rqstp->rq_arg.page_base = 0;
@@ -1019,14 +1006,26 @@ static int svc_tcp_recvfrom(struct svc_rqst *rqstp)
 
 	return rqstp->rq_arg.len;
 
+err_incomplete:
+	svc_tcp_save_pages(svsk, rqstp);
+	if (len < 0 && len != -EAGAIN)
+		goto err_delete;
+	if (len == want)
+		svc_tcp_fragment_received(svsk);
+	else
+		trace_svcsock_tcp_recv_short(&svsk->sk_xprt,
+				svc_sock_reclen(svsk),
+				svsk->sk_tcplen - sizeof(rpc_fraghdr));
+	goto err_noclose;
 error:
 	if (len != -EAGAIN)
 		goto err_delete;
-	dprintk("RPC: TCP recvfrom got EAGAIN\n");
+	trace_svcsock_tcp_recv_eagain(&svsk->sk_xprt, 0);
 	return 0;
+err_nuts:
+	svsk->sk_datalen = 0;
 err_delete:
-	printk(KERN_NOTICE "%s: recvfrom returned errno %d\n",
-	       svsk->sk_xprt.xpt_server->sv_name, -len);
+	trace_svcsock_tcp_recv_err(&svsk->sk_xprt, len);
 	set_bit(XPT_CLOSE, &svsk->sk_xprt.xpt_flags);
 err_noclose:
 	return 0;	/* record not complete */