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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, NeilBrown <neilb@suse.com>,
        Trond Myklebust <trond.myklebust@primarydata.com>,
        Calum Mackay <calum.mackay@oracle.com>
Subject: [PATCH 4.9 001/117] SUNRPC: ECONNREFUSED should cause a rebind.
Date:   Mon,  9 Nov 2020 13:53:47 +0100
Message-Id: <20201109125025.700918529@linuxfoundation.org>
In-Reply-To: <20201109125025.630721781@linuxfoundation.org>
References: <20201109125025.630721781@linuxfoundation.org>
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From: NeilBrown <neilb@suse.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@suse.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Cc: Calum Mackay <calum.mackay@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -1936,6 +1936,14 @@ 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: