linux-kernel - [PATCH 4.4 01/86] SUNRPC: ECONNREFUSED should cause a rebind.

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Date:   Mon,  9 Nov 2020 13:54:08 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, NeilBrown <neilb@...e.com>,
        Trond Myklebust <trond.myklebust@...marydata.com>,
        Calum Mackay <calum.mackay@...cle.com>
Subject: [PATCH 4.4 01/86] SUNRPC: ECONNREFUSED should cause a rebind.

From: NeilBrown <neilb@...e.com>

commit fd01b2597941d9c17980222999b0721648b383b8 upstream.

If you
 - mount and NFSv3 filesystem
 - do some file locking which requires the server
   to make a GRANT call back
 - unmount
 - mount again and do the same locking

then the second attempt at locking suffers a 30 second delay.
Unmounting and remounting causes lockd to stop and restart,
which causes it to bind to a new port.
The server still thinks the old port is valid and gets ECONNREFUSED
when trying to contact it.
ECONNREFUSED should be seen as a hard error that is not worth
retrying.  Rebinding is the only reasonable response.

This patch forces a rebind if that makes sense.

Signed-off-by: NeilBrown <neilb@...e.com>
Signed-off-by: Trond Myklebust <trond.myklebust@...marydata.com>
Cc: Calum Mackay <calum.mackay@...cle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 net/sunrpc/clnt.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -1826,6 +1826,14 @@ call_connect_status(struct rpc_task *tas
 	task->tk_status = 0;
 	switch (status) {
 	case -ECONNREFUSED:
+		/* A positive refusal suggests a rebind is needed. */
+		if (RPC_IS_SOFTCONN(task))
+			break;
+		if (clnt->cl_autobind) {
+			rpc_force_rebind(clnt);
+			task->tk_action = call_bind;
+			return;
+		}
 	case -ECONNRESET:
 	case -ECONNABORTED:
 	case -ENETUNREACH: