releases/4.1.9/sunrpc-lock-the-transport-layer-on-shutdown.patch

From 79234c3db6842a3de03817211d891e0c2878f756 Mon Sep 17 00:00:00 2001
From: Trond Myklebust <trond.myklebust@primarydata.com>
Date: Fri, 18 Sep 2015 15:53:24 -0400
Subject: SUNRPC: Lock the transport layer on shutdown

From: Trond Myklebust <trond.myklebust@primarydata.com>

commit 79234c3db6842a3de03817211d891e0c2878f756 upstream.

Avoid all races with the connect/disconnect handlers by taking the
transport lock.

Reported-by:"Suzuki K. Poulose" <suzuki.poulose@arm.com>
Acked-by: Jeff Layton <jlayton@poochiereds.net>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 net/sunrpc/xprt.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -611,6 +611,7 @@ static void xprt_autoclose(struct work_s
 	xprt->ops->close(xprt);
 	clear_bit(XPRT_CLOSE_WAIT, &xprt->state);
 	xprt_release_write(xprt, NULL);
+	wake_up_bit(&xprt->state, XPRT_LOCKED);
 }
 
 /**
@@ -720,6 +721,7 @@ void xprt_unlock_connect(struct rpc_xprt
 	xprt->ops->release_xprt(xprt, NULL);
 out:
 	spin_unlock_bh(&xprt->transport_lock);
+	wake_up_bit(&xprt->state, XPRT_LOCKED);
 }
 
 /**
@@ -1389,6 +1391,10 @@ out:
 static void xprt_destroy(struct rpc_xprt *xprt)
 {
 	dprintk("RPC:       destroying transport %p\n", xprt);
+
+	/* Exclude transport connect/disconnect handlers */
+	wait_on_bit_lock(&xprt->state, XPRT_LOCKED, TASK_UNINTERRUPTIBLE);
+
 	del_timer_sync(&xprt->timer);
 
 	rpc_xprt_debugfs_unregister(xprt);