SUNRPC: Fix a potential race in xprt_connect()

If an asynchronous connection attempt completes while another task is
in xprt_connect(), then the call to rpc_sleep_on() could end up
racing with the call to xprt_wake_pending_tasks().
So add a second test of the connection state after we've put the
task to sleep and set the XPRT_CONNECTING flag, when we know that there
can be no asynchronous connection attempts still in progress.

Fixes: 0b9e79431377d ("SUNRPC: Move the test for XPRT_CONNECTING into...")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index 122c91c..ce92700 100644 (file)
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -826,8 +826,15 @@ void xprt_connect(struct rpc_task *task)
                        return;
                if (xprt_test_and_set_connecting(xprt))
                        return;
-               xprt->stat.connect_start = jiffies;
-               xprt->ops->connect(xprt, task);
+               /* Race breaker */
+               if (!xprt_connected(xprt)) {
+                       xprt->stat.connect_start = jiffies;
+                       xprt->ops->connect(xprt, task);
+               } else {
+                       xprt_clear_connecting(xprt);
+                       task->tk_status = 0;
+                       rpc_wake_up_queued_task(&xprt->pending, task);
+               }
        }
        xprt_release_write(xprt, task);
 }